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 @kindex set exec-wrapper
2093 @item set exec-wrapper @var{wrapper}
2094 @itemx show exec-wrapper
2095 @itemx unset exec-wrapper
2096 When @samp{exec-wrapper} is set, the specified wrapper is used to
2097 launch programs for debugging. @value{GDBN} starts your program
2098 with a shell command of the form @kbd{exec @var{wrapper}
2099 @var{program}}. Quoting is added to @var{program} and its
2100 arguments, but not to @var{wrapper}, so you should add quotes if
2101 appropriate for your shell. The wrapper runs until it executes
2102 your program, and then @value{GDBN} takes control.
2104 You can use any program that eventually calls @code{execve} with
2105 its arguments as a wrapper. Several standard Unix utilities do
2106 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2107 with @code{exec "$@@"} will also work.
2109 For example, you can use @code{env} to pass an environment variable to
2110 the debugged program, without setting the variable in your shell's
2114 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2118 This command is available when debugging locally on most targets, excluding
2119 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2121 @kindex set startup-with-shell
2122 @item set startup-with-shell
2123 @itemx set startup-with-shell on
2124 @itemx set startup-with-shell off
2125 @itemx show set startup-with-shell
2126 On Unix systems, by default, if a shell is available on your target,
2127 @value{GDBN}) uses it to start your program. Arguments of the
2128 @code{run} command are passed to the shell, which does variable
2129 substitution, expands wildcard characters and performs redirection of
2130 I/O. In some circumstances, it may be useful to disable such use of a
2131 shell, for example, when debugging the shell itself or diagnosing
2132 startup failures such as:
2136 Starting program: ./a.out
2137 During startup program terminated with signal SIGSEGV, Segmentation fault.
2141 which indicates the shell or the wrapper specified with
2142 @samp{exec-wrapper} crashed, not your program. Most often, this is
2143 caused by something odd in your shell's non-interactive mode
2144 initialization file---such as @file{.cshrc} for C-shell,
2145 $@file{.zshenv} for the Z shell, or the file specified in the
2146 @samp{BASH_ENV} environment variable for BASH.
2148 @kindex set disable-randomization
2149 @item set disable-randomization
2150 @itemx set disable-randomization on
2151 This option (enabled by default in @value{GDBN}) will turn off the native
2152 randomization of the virtual address space of the started program. This option
2153 is useful for multiple debugging sessions to make the execution better
2154 reproducible and memory addresses reusable across debugging sessions.
2156 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2157 On @sc{gnu}/Linux you can get the same behavior using
2160 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2163 @item set disable-randomization off
2164 Leave the behavior of the started executable unchanged. Some bugs rear their
2165 ugly heads only when the program is loaded at certain addresses. If your bug
2166 disappears when you run the program under @value{GDBN}, that might be because
2167 @value{GDBN} by default disables the address randomization on platforms, such
2168 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2169 disable-randomization off} to try to reproduce such elusive bugs.
2171 On targets where it is available, virtual address space randomization
2172 protects the programs against certain kinds of security attacks. In these
2173 cases the attacker needs to know the exact location of a concrete executable
2174 code. Randomizing its location makes it impossible to inject jumps misusing
2175 a code at its expected addresses.
2177 Prelinking shared libraries provides a startup performance advantage but it
2178 makes addresses in these libraries predictable for privileged processes by
2179 having just unprivileged access at the target system. Reading the shared
2180 library binary gives enough information for assembling the malicious code
2181 misusing it. Still even a prelinked shared library can get loaded at a new
2182 random address just requiring the regular relocation process during the
2183 startup. Shared libraries not already prelinked are always loaded at
2184 a randomly chosen address.
2186 Position independent executables (PIE) contain position independent code
2187 similar to the shared libraries and therefore such executables get loaded at
2188 a randomly chosen address upon startup. PIE executables always load even
2189 already prelinked shared libraries at a random address. You can build such
2190 executable using @command{gcc -fPIE -pie}.
2192 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2193 (as long as the randomization is enabled).
2195 @item show disable-randomization
2196 Show the current setting of the explicit disable of the native randomization of
2197 the virtual address space of the started program.
2202 @section Your Program's Arguments
2204 @cindex arguments (to your program)
2205 The arguments to your program can be specified by the arguments of the
2207 They are passed to a shell, which expands wildcard characters and
2208 performs redirection of I/O, and thence to your program. Your
2209 @code{SHELL} environment variable (if it exists) specifies what shell
2210 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2211 the default shell (@file{/bin/sh} on Unix).
2213 On non-Unix systems, the program is usually invoked directly by
2214 @value{GDBN}, which emulates I/O redirection via the appropriate system
2215 calls, and the wildcard characters are expanded by the startup code of
2216 the program, not by the shell.
2218 @code{run} with no arguments uses the same arguments used by the previous
2219 @code{run}, or those set by the @code{set args} command.
2224 Specify the arguments to be used the next time your program is run. If
2225 @code{set args} has no arguments, @code{run} executes your program
2226 with no arguments. Once you have run your program with arguments,
2227 using @code{set args} before the next @code{run} is the only way to run
2228 it again without arguments.
2232 Show the arguments to give your program when it is started.
2236 @section Your Program's Environment
2238 @cindex environment (of your program)
2239 The @dfn{environment} consists of a set of environment variables and
2240 their values. Environment variables conventionally record such things as
2241 your user name, your home directory, your terminal type, and your search
2242 path for programs to run. Usually you set up environment variables with
2243 the shell and they are inherited by all the other programs you run. When
2244 debugging, it can be useful to try running your program with a modified
2245 environment without having to start @value{GDBN} over again.
2249 @item path @var{directory}
2250 Add @var{directory} to the front of the @code{PATH} environment variable
2251 (the search path for executables) that will be passed to your program.
2252 The value of @code{PATH} used by @value{GDBN} does not change.
2253 You may specify several directory names, separated by whitespace or by a
2254 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2255 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2256 is moved to the front, so it is searched sooner.
2258 You can use the string @samp{$cwd} to refer to whatever is the current
2259 working directory at the time @value{GDBN} searches the path. If you
2260 use @samp{.} instead, it refers to the directory where you executed the
2261 @code{path} command. @value{GDBN} replaces @samp{.} in the
2262 @var{directory} argument (with the current path) before adding
2263 @var{directory} to the search path.
2264 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2265 @c document that, since repeating it would be a no-op.
2269 Display the list of search paths for executables (the @code{PATH}
2270 environment variable).
2272 @kindex show environment
2273 @item show environment @r{[}@var{varname}@r{]}
2274 Print the value of environment variable @var{varname} to be given to
2275 your program when it starts. If you do not supply @var{varname},
2276 print the names and values of all environment variables to be given to
2277 your program. You can abbreviate @code{environment} as @code{env}.
2279 @kindex set environment
2280 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2281 Set environment variable @var{varname} to @var{value}. The value
2282 changes for your program only, not for @value{GDBN} itself. @var{value} may
2283 be any string; the values of environment variables are just strings, and
2284 any interpretation is supplied by your program itself. The @var{value}
2285 parameter is optional; if it is eliminated, the variable is set to a
2287 @c "any string" here does not include leading, trailing
2288 @c blanks. Gnu asks: does anyone care?
2290 For example, this command:
2297 tells the debugged program, when subsequently run, that its user is named
2298 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2299 are not actually required.)
2301 @kindex unset environment
2302 @item unset environment @var{varname}
2303 Remove variable @var{varname} from the environment to be passed to your
2304 program. This is different from @samp{set env @var{varname} =};
2305 @code{unset environment} removes the variable from the environment,
2306 rather than assigning it an empty value.
2309 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2310 the shell indicated by your @code{SHELL} environment variable if it
2311 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2312 names a shell that runs an initialization file when started
2313 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2314 for the Z shell, or the file specified in the @samp{BASH_ENV}
2315 environment variable for BASH---any variables you set in that file
2316 affect your program. You may wish to move setting of environment
2317 variables to files that are only run when you sign on, such as
2318 @file{.login} or @file{.profile}.
2320 @node Working Directory
2321 @section Your Program's Working Directory
2323 @cindex working directory (of your program)
2324 Each time you start your program with @code{run}, it inherits its
2325 working directory from the current working directory of @value{GDBN}.
2326 The @value{GDBN} working directory is initially whatever it inherited
2327 from its parent process (typically the shell), but you can specify a new
2328 working directory in @value{GDBN} with the @code{cd} command.
2330 The @value{GDBN} working directory also serves as a default for the commands
2331 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2336 @cindex change working directory
2337 @item cd @r{[}@var{directory}@r{]}
2338 Set the @value{GDBN} working directory to @var{directory}. If not
2339 given, @var{directory} uses @file{'~'}.
2343 Print the @value{GDBN} working directory.
2346 It is generally impossible to find the current working directory of
2347 the process being debugged (since a program can change its directory
2348 during its run). If you work on a system where @value{GDBN} is
2349 configured with the @file{/proc} support, you can use the @code{info
2350 proc} command (@pxref{SVR4 Process Information}) to find out the
2351 current working directory of the debuggee.
2354 @section Your Program's Input and Output
2359 By default, the program you run under @value{GDBN} does input and output to
2360 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2361 to its own terminal modes to interact with you, but it records the terminal
2362 modes your program was using and switches back to them when you continue
2363 running your program.
2366 @kindex info terminal
2368 Displays information recorded by @value{GDBN} about the terminal modes your
2372 You can redirect your program's input and/or output using shell
2373 redirection with the @code{run} command. For example,
2380 starts your program, diverting its output to the file @file{outfile}.
2383 @cindex controlling terminal
2384 Another way to specify where your program should do input and output is
2385 with the @code{tty} command. This command accepts a file name as
2386 argument, and causes this file to be the default for future @code{run}
2387 commands. It also resets the controlling terminal for the child
2388 process, for future @code{run} commands. For example,
2395 directs that processes started with subsequent @code{run} commands
2396 default to do input and output on the terminal @file{/dev/ttyb} and have
2397 that as their controlling terminal.
2399 An explicit redirection in @code{run} overrides the @code{tty} command's
2400 effect on the input/output device, but not its effect on the controlling
2403 When you use the @code{tty} command or redirect input in the @code{run}
2404 command, only the input @emph{for your program} is affected. The input
2405 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2406 for @code{set inferior-tty}.
2408 @cindex inferior tty
2409 @cindex set inferior controlling terminal
2410 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2411 display the name of the terminal that will be used for future runs of your
2415 @item set inferior-tty /dev/ttyb
2416 @kindex set inferior-tty
2417 Set the tty for the program being debugged to /dev/ttyb.
2419 @item show inferior-tty
2420 @kindex show inferior-tty
2421 Show the current tty for the program being debugged.
2425 @section Debugging an Already-running Process
2430 @item attach @var{process-id}
2431 This command attaches to a running process---one that was started
2432 outside @value{GDBN}. (@code{info files} shows your active
2433 targets.) The command takes as argument a process ID. The usual way to
2434 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2435 or with the @samp{jobs -l} shell command.
2437 @code{attach} does not repeat if you press @key{RET} a second time after
2438 executing the command.
2441 To use @code{attach}, your program must be running in an environment
2442 which supports processes; for example, @code{attach} does not work for
2443 programs on bare-board targets that lack an operating system. You must
2444 also have permission to send the process a signal.
2446 When you use @code{attach}, the debugger finds the program running in
2447 the process first by looking in the current working directory, then (if
2448 the program is not found) by using the source file search path
2449 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2450 the @code{file} command to load the program. @xref{Files, ,Commands to
2453 The first thing @value{GDBN} does after arranging to debug the specified
2454 process is to stop it. You can examine and modify an attached process
2455 with all the @value{GDBN} commands that are ordinarily available when
2456 you start processes with @code{run}. You can insert breakpoints; you
2457 can step and continue; you can modify storage. If you would rather the
2458 process continue running, you may use the @code{continue} command after
2459 attaching @value{GDBN} to the process.
2464 When you have finished debugging the attached process, you can use the
2465 @code{detach} command to release it from @value{GDBN} control. Detaching
2466 the process continues its execution. After the @code{detach} command,
2467 that process and @value{GDBN} become completely independent once more, and you
2468 are ready to @code{attach} another process or start one with @code{run}.
2469 @code{detach} does not repeat if you press @key{RET} again after
2470 executing the command.
2473 If you exit @value{GDBN} while you have an attached process, you detach
2474 that process. If you use the @code{run} command, you kill that process.
2475 By default, @value{GDBN} asks for confirmation if you try to do either of these
2476 things; you can control whether or not you need to confirm by using the
2477 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2481 @section Killing the Child Process
2486 Kill the child process in which your program is running under @value{GDBN}.
2489 This command is useful if you wish to debug a core dump instead of a
2490 running process. @value{GDBN} ignores any core dump file while your program
2493 On some operating systems, a program cannot be executed outside @value{GDBN}
2494 while you have breakpoints set on it inside @value{GDBN}. You can use the
2495 @code{kill} command in this situation to permit running your program
2496 outside the debugger.
2498 The @code{kill} command is also useful if you wish to recompile and
2499 relink your program, since on many systems it is impossible to modify an
2500 executable file while it is running in a process. In this case, when you
2501 next type @code{run}, @value{GDBN} notices that the file has changed, and
2502 reads the symbol table again (while trying to preserve your current
2503 breakpoint settings).
2505 @node Inferiors and Programs
2506 @section Debugging Multiple Inferiors and Programs
2508 @value{GDBN} lets you run and debug multiple programs in a single
2509 session. In addition, @value{GDBN} on some systems may let you run
2510 several programs simultaneously (otherwise you have to exit from one
2511 before starting another). In the most general case, you can have
2512 multiple threads of execution in each of multiple processes, launched
2513 from multiple executables.
2516 @value{GDBN} represents the state of each program execution with an
2517 object called an @dfn{inferior}. An inferior typically corresponds to
2518 a process, but is more general and applies also to targets that do not
2519 have processes. Inferiors may be created before a process runs, and
2520 may be retained after a process exits. Inferiors have unique
2521 identifiers that are different from process ids. Usually each
2522 inferior will also have its own distinct address space, although some
2523 embedded targets may have several inferiors running in different parts
2524 of a single address space. Each inferior may in turn have multiple
2525 threads running in it.
2527 To find out what inferiors exist at any moment, use @w{@code{info
2531 @kindex info inferiors
2532 @item info inferiors
2533 Print a list of all inferiors currently being managed by @value{GDBN}.
2535 @value{GDBN} displays for each inferior (in this order):
2539 the inferior number assigned by @value{GDBN}
2542 the target system's inferior identifier
2545 the name of the executable the inferior is running.
2550 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2551 indicates the current inferior.
2555 @c end table here to get a little more width for example
2558 (@value{GDBP}) info inferiors
2559 Num Description Executable
2560 2 process 2307 hello
2561 * 1 process 3401 goodbye
2564 To switch focus between inferiors, use the @code{inferior} command:
2567 @kindex inferior @var{infno}
2568 @item inferior @var{infno}
2569 Make inferior number @var{infno} the current inferior. The argument
2570 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2571 in the first field of the @samp{info inferiors} display.
2575 You can get multiple executables into a debugging session via the
2576 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2577 systems @value{GDBN} can add inferiors to the debug session
2578 automatically by following calls to @code{fork} and @code{exec}. To
2579 remove inferiors from the debugging session use the
2580 @w{@code{remove-inferiors}} command.
2583 @kindex add-inferior
2584 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2585 Adds @var{n} inferiors to be run using @var{executable} as the
2586 executable. @var{n} defaults to 1. If no executable is specified,
2587 the inferiors begins empty, with no program. You can still assign or
2588 change the program assigned to the inferior at any time by using the
2589 @code{file} command with the executable name as its argument.
2591 @kindex clone-inferior
2592 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2593 Adds @var{n} inferiors ready to execute the same program as inferior
2594 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2595 number of the current inferior. This is a convenient command when you
2596 want to run another instance of the inferior you are debugging.
2599 (@value{GDBP}) info inferiors
2600 Num Description Executable
2601 * 1 process 29964 helloworld
2602 (@value{GDBP}) clone-inferior
2605 (@value{GDBP}) info inferiors
2606 Num Description Executable
2608 * 1 process 29964 helloworld
2611 You can now simply switch focus to inferior 2 and run it.
2613 @kindex remove-inferiors
2614 @item remove-inferiors @var{infno}@dots{}
2615 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2616 possible to remove an inferior that is running with this command. For
2617 those, use the @code{kill} or @code{detach} command first.
2621 To quit debugging one of the running inferiors that is not the current
2622 inferior, you can either detach from it by using the @w{@code{detach
2623 inferior}} command (allowing it to run independently), or kill it
2624 using the @w{@code{kill inferiors}} command:
2627 @kindex detach inferiors @var{infno}@dots{}
2628 @item detach inferior @var{infno}@dots{}
2629 Detach from the inferior or inferiors identified by @value{GDBN}
2630 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2631 still stays on the list of inferiors shown by @code{info inferiors},
2632 but its Description will show @samp{<null>}.
2634 @kindex kill inferiors @var{infno}@dots{}
2635 @item kill inferiors @var{infno}@dots{}
2636 Kill the inferior or inferiors identified by @value{GDBN} inferior
2637 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2638 stays on the list of inferiors shown by @code{info inferiors}, but its
2639 Description will show @samp{<null>}.
2642 After the successful completion of a command such as @code{detach},
2643 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2644 a normal process exit, the inferior is still valid and listed with
2645 @code{info inferiors}, ready to be restarted.
2648 To be notified when inferiors are started or exit under @value{GDBN}'s
2649 control use @w{@code{set print inferior-events}}:
2652 @kindex set print inferior-events
2653 @cindex print messages on inferior start and exit
2654 @item set print inferior-events
2655 @itemx set print inferior-events on
2656 @itemx set print inferior-events off
2657 The @code{set print inferior-events} command allows you to enable or
2658 disable printing of messages when @value{GDBN} notices that new
2659 inferiors have started or that inferiors have exited or have been
2660 detached. By default, these messages will not be printed.
2662 @kindex show print inferior-events
2663 @item show print inferior-events
2664 Show whether messages will be printed when @value{GDBN} detects that
2665 inferiors have started, exited or have been detached.
2668 Many commands will work the same with multiple programs as with a
2669 single program: e.g., @code{print myglobal} will simply display the
2670 value of @code{myglobal} in the current inferior.
2673 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2674 get more info about the relationship of inferiors, programs, address
2675 spaces in a debug session. You can do that with the @w{@code{maint
2676 info program-spaces}} command.
2679 @kindex maint info program-spaces
2680 @item maint info program-spaces
2681 Print a list of all program spaces currently being managed by
2684 @value{GDBN} displays for each program space (in this order):
2688 the program space number assigned by @value{GDBN}
2691 the name of the executable loaded into the program space, with e.g.,
2692 the @code{file} command.
2697 An asterisk @samp{*} preceding the @value{GDBN} program space number
2698 indicates the current program space.
2700 In addition, below each program space line, @value{GDBN} prints extra
2701 information that isn't suitable to display in tabular form. For
2702 example, the list of inferiors bound to the program space.
2705 (@value{GDBP}) maint info program-spaces
2708 Bound inferiors: ID 1 (process 21561)
2712 Here we can see that no inferior is running the program @code{hello},
2713 while @code{process 21561} is running the program @code{goodbye}. On
2714 some targets, it is possible that multiple inferiors are bound to the
2715 same program space. The most common example is that of debugging both
2716 the parent and child processes of a @code{vfork} call. For example,
2719 (@value{GDBP}) maint info program-spaces
2722 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2725 Here, both inferior 2 and inferior 1 are running in the same program
2726 space as a result of inferior 1 having executed a @code{vfork} call.
2730 @section Debugging Programs with Multiple Threads
2732 @cindex threads of execution
2733 @cindex multiple threads
2734 @cindex switching threads
2735 In some operating systems, such as HP-UX and Solaris, a single program
2736 may have more than one @dfn{thread} of execution. The precise semantics
2737 of threads differ from one operating system to another, but in general
2738 the threads of a single program are akin to multiple processes---except
2739 that they share one address space (that is, they can all examine and
2740 modify the same variables). On the other hand, each thread has its own
2741 registers and execution stack, and perhaps private memory.
2743 @value{GDBN} provides these facilities for debugging multi-thread
2747 @item automatic notification of new threads
2748 @item @samp{thread @var{threadno}}, a command to switch among threads
2749 @item @samp{info threads}, a command to inquire about existing threads
2750 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2751 a command to apply a command to a list of threads
2752 @item thread-specific breakpoints
2753 @item @samp{set print thread-events}, which controls printing of
2754 messages on thread start and exit.
2755 @item @samp{set libthread-db-search-path @var{path}}, which lets
2756 the user specify which @code{libthread_db} to use if the default choice
2757 isn't compatible with the program.
2761 @emph{Warning:} These facilities are not yet available on every
2762 @value{GDBN} configuration where the operating system supports threads.
2763 If your @value{GDBN} does not support threads, these commands have no
2764 effect. For example, a system without thread support shows no output
2765 from @samp{info threads}, and always rejects the @code{thread} command,
2769 (@value{GDBP}) info threads
2770 (@value{GDBP}) thread 1
2771 Thread ID 1 not known. Use the "info threads" command to
2772 see the IDs of currently known threads.
2774 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2775 @c doesn't support threads"?
2778 @cindex focus of debugging
2779 @cindex current thread
2780 The @value{GDBN} thread debugging facility allows you to observe all
2781 threads while your program runs---but whenever @value{GDBN} takes
2782 control, one thread in particular is always the focus of debugging.
2783 This thread is called the @dfn{current thread}. Debugging commands show
2784 program information from the perspective of the current thread.
2786 @cindex @code{New} @var{systag} message
2787 @cindex thread identifier (system)
2788 @c FIXME-implementors!! It would be more helpful if the [New...] message
2789 @c included GDB's numeric thread handle, so you could just go to that
2790 @c thread without first checking `info threads'.
2791 Whenever @value{GDBN} detects a new thread in your program, it displays
2792 the target system's identification for the thread with a message in the
2793 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2794 whose form varies depending on the particular system. For example, on
2795 @sc{gnu}/Linux, you might see
2798 [New Thread 0x41e02940 (LWP 25582)]
2802 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2803 the @var{systag} is simply something like @samp{process 368}, with no
2806 @c FIXME!! (1) Does the [New...] message appear even for the very first
2807 @c thread of a program, or does it only appear for the
2808 @c second---i.e.@: when it becomes obvious we have a multithread
2810 @c (2) *Is* there necessarily a first thread always? Or do some
2811 @c multithread systems permit starting a program with multiple
2812 @c threads ab initio?
2814 @cindex thread number
2815 @cindex thread identifier (GDB)
2816 For debugging purposes, @value{GDBN} associates its own thread
2817 number---always a single integer---with each thread in your program.
2820 @kindex info threads
2821 @item info threads @r{[}@var{id}@dots{}@r{]}
2822 Display a summary of all threads currently in your program. Optional
2823 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2824 means to print information only about the specified thread or threads.
2825 @value{GDBN} displays for each thread (in this order):
2829 the thread number assigned by @value{GDBN}
2832 the target system's thread identifier (@var{systag})
2835 the thread's name, if one is known. A thread can either be named by
2836 the user (see @code{thread name}, below), or, in some cases, by the
2840 the current stack frame summary for that thread
2844 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2845 indicates the current thread.
2849 @c end table here to get a little more width for example
2852 (@value{GDBP}) info threads
2854 3 process 35 thread 27 0x34e5 in sigpause ()
2855 2 process 35 thread 23 0x34e5 in sigpause ()
2856 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2860 On Solaris, you can display more information about user threads with a
2861 Solaris-specific command:
2864 @item maint info sol-threads
2865 @kindex maint info sol-threads
2866 @cindex thread info (Solaris)
2867 Display info on Solaris user threads.
2871 @kindex thread @var{threadno}
2872 @item thread @var{threadno}
2873 Make thread number @var{threadno} the current thread. The command
2874 argument @var{threadno} is the internal @value{GDBN} thread number, as
2875 shown in the first field of the @samp{info threads} display.
2876 @value{GDBN} responds by displaying the system identifier of the thread
2877 you selected, and its current stack frame summary:
2880 (@value{GDBP}) thread 2
2881 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2882 #0 some_function (ignore=0x0) at example.c:8
2883 8 printf ("hello\n");
2887 As with the @samp{[New @dots{}]} message, the form of the text after
2888 @samp{Switching to} depends on your system's conventions for identifying
2891 @vindex $_thread@r{, convenience variable}
2892 The debugger convenience variable @samp{$_thread} contains the number
2893 of the current thread. You may find this useful in writing breakpoint
2894 conditional expressions, command scripts, and so forth. See
2895 @xref{Convenience Vars,, Convenience Variables}, for general
2896 information on convenience variables.
2898 @kindex thread apply
2899 @cindex apply command to several threads
2900 @item thread apply [@var{threadno} | all] @var{command}
2901 The @code{thread apply} command allows you to apply the named
2902 @var{command} to one or more threads. Specify the numbers of the
2903 threads that you want affected with the command argument
2904 @var{threadno}. It can be a single thread number, one of the numbers
2905 shown in the first field of the @samp{info threads} display; or it
2906 could be a range of thread numbers, as in @code{2-4}. To apply a
2907 command to all threads, type @kbd{thread apply all @var{command}}.
2910 @cindex name a thread
2911 @item thread name [@var{name}]
2912 This command assigns a name to the current thread. If no argument is
2913 given, any existing user-specified name is removed. The thread name
2914 appears in the @samp{info threads} display.
2916 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2917 determine the name of the thread as given by the OS. On these
2918 systems, a name specified with @samp{thread name} will override the
2919 system-give name, and removing the user-specified name will cause
2920 @value{GDBN} to once again display the system-specified name.
2923 @cindex search for a thread
2924 @item thread find [@var{regexp}]
2925 Search for and display thread ids whose name or @var{systag}
2926 matches the supplied regular expression.
2928 As well as being the complement to the @samp{thread name} command,
2929 this command also allows you to identify a thread by its target
2930 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2934 (@value{GDBN}) thread find 26688
2935 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2936 (@value{GDBN}) info thread 4
2938 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2941 @kindex set print thread-events
2942 @cindex print messages on thread start and exit
2943 @item set print thread-events
2944 @itemx set print thread-events on
2945 @itemx set print thread-events off
2946 The @code{set print thread-events} command allows you to enable or
2947 disable printing of messages when @value{GDBN} notices that new threads have
2948 started or that threads have exited. By default, these messages will
2949 be printed if detection of these events is supported by the target.
2950 Note that these messages cannot be disabled on all targets.
2952 @kindex show print thread-events
2953 @item show print thread-events
2954 Show whether messages will be printed when @value{GDBN} detects that threads
2955 have started and exited.
2958 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2959 more information about how @value{GDBN} behaves when you stop and start
2960 programs with multiple threads.
2962 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2963 watchpoints in programs with multiple threads.
2965 @anchor{set libthread-db-search-path}
2967 @kindex set libthread-db-search-path
2968 @cindex search path for @code{libthread_db}
2969 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2970 If this variable is set, @var{path} is a colon-separated list of
2971 directories @value{GDBN} will use to search for @code{libthread_db}.
2972 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2973 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2974 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2977 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2978 @code{libthread_db} library to obtain information about threads in the
2979 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2980 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2981 specific thread debugging library loading is enabled
2982 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2984 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2985 refers to the default system directories that are
2986 normally searched for loading shared libraries. The @samp{$sdir} entry
2987 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2988 (@pxref{libthread_db.so.1 file}).
2990 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2991 refers to the directory from which @code{libpthread}
2992 was loaded in the inferior process.
2994 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2995 @value{GDBN} attempts to initialize it with the current inferior process.
2996 If this initialization fails (which could happen because of a version
2997 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2998 will unload @code{libthread_db}, and continue with the next directory.
2999 If none of @code{libthread_db} libraries initialize successfully,
3000 @value{GDBN} will issue a warning and thread debugging will be disabled.
3002 Setting @code{libthread-db-search-path} is currently implemented
3003 only on some platforms.
3005 @kindex show libthread-db-search-path
3006 @item show libthread-db-search-path
3007 Display current libthread_db search path.
3009 @kindex set debug libthread-db
3010 @kindex show debug libthread-db
3011 @cindex debugging @code{libthread_db}
3012 @item set debug libthread-db
3013 @itemx show debug libthread-db
3014 Turns on or off display of @code{libthread_db}-related events.
3015 Use @code{1} to enable, @code{0} to disable.
3019 @section Debugging Forks
3021 @cindex fork, debugging programs which call
3022 @cindex multiple processes
3023 @cindex processes, multiple
3024 On most systems, @value{GDBN} has no special support for debugging
3025 programs which create additional processes using the @code{fork}
3026 function. When a program forks, @value{GDBN} will continue to debug the
3027 parent process and the child process will run unimpeded. If you have
3028 set a breakpoint in any code which the child then executes, the child
3029 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3030 will cause it to terminate.
3032 However, if you want to debug the child process there is a workaround
3033 which isn't too painful. Put a call to @code{sleep} in the code which
3034 the child process executes after the fork. It may be useful to sleep
3035 only if a certain environment variable is set, or a certain file exists,
3036 so that the delay need not occur when you don't want to run @value{GDBN}
3037 on the child. While the child is sleeping, use the @code{ps} program to
3038 get its process ID. Then tell @value{GDBN} (a new invocation of
3039 @value{GDBN} if you are also debugging the parent process) to attach to
3040 the child process (@pxref{Attach}). From that point on you can debug
3041 the child process just like any other process which you attached to.
3043 On some systems, @value{GDBN} provides support for debugging programs that
3044 create additional processes using the @code{fork} or @code{vfork} functions.
3045 Currently, the only platforms with this feature are HP-UX (11.x and later
3046 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3048 By default, when a program forks, @value{GDBN} will continue to debug
3049 the parent process and the child process will run unimpeded.
3051 If you want to follow the child process instead of the parent process,
3052 use the command @w{@code{set follow-fork-mode}}.
3055 @kindex set follow-fork-mode
3056 @item set follow-fork-mode @var{mode}
3057 Set the debugger response to a program call of @code{fork} or
3058 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3059 process. The @var{mode} argument can be:
3063 The original process is debugged after a fork. The child process runs
3064 unimpeded. This is the default.
3067 The new process is debugged after a fork. The parent process runs
3072 @kindex show follow-fork-mode
3073 @item show follow-fork-mode
3074 Display the current debugger response to a @code{fork} or @code{vfork} call.
3077 @cindex debugging multiple processes
3078 On Linux, if you want to debug both the parent and child processes, use the
3079 command @w{@code{set detach-on-fork}}.
3082 @kindex set detach-on-fork
3083 @item set detach-on-fork @var{mode}
3084 Tells gdb whether to detach one of the processes after a fork, or
3085 retain debugger control over them both.
3089 The child process (or parent process, depending on the value of
3090 @code{follow-fork-mode}) will be detached and allowed to run
3091 independently. This is the default.
3094 Both processes will be held under the control of @value{GDBN}.
3095 One process (child or parent, depending on the value of
3096 @code{follow-fork-mode}) is debugged as usual, while the other
3101 @kindex show detach-on-fork
3102 @item show detach-on-fork
3103 Show whether detach-on-fork mode is on/off.
3106 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3107 will retain control of all forked processes (including nested forks).
3108 You can list the forked processes under the control of @value{GDBN} by
3109 using the @w{@code{info inferiors}} command, and switch from one fork
3110 to another by using the @code{inferior} command (@pxref{Inferiors and
3111 Programs, ,Debugging Multiple Inferiors and Programs}).
3113 To quit debugging one of the forked processes, you can either detach
3114 from it by using the @w{@code{detach inferiors}} command (allowing it
3115 to run independently), or kill it using the @w{@code{kill inferiors}}
3116 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3119 If you ask to debug a child process and a @code{vfork} is followed by an
3120 @code{exec}, @value{GDBN} executes the new target up to the first
3121 breakpoint in the new target. If you have a breakpoint set on
3122 @code{main} in your original program, the breakpoint will also be set on
3123 the child process's @code{main}.
3125 On some systems, when a child process is spawned by @code{vfork}, you
3126 cannot debug the child or parent until an @code{exec} call completes.
3128 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3129 call executes, the new target restarts. To restart the parent
3130 process, use the @code{file} command with the parent executable name
3131 as its argument. By default, after an @code{exec} call executes,
3132 @value{GDBN} discards the symbols of the previous executable image.
3133 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3137 @kindex set follow-exec-mode
3138 @item set follow-exec-mode @var{mode}
3140 Set debugger response to a program call of @code{exec}. An
3141 @code{exec} call replaces the program image of a process.
3143 @code{follow-exec-mode} can be:
3147 @value{GDBN} creates a new inferior and rebinds the process to this
3148 new inferior. The program the process was running before the
3149 @code{exec} call can be restarted afterwards by restarting the
3155 (@value{GDBP}) info inferiors
3157 Id Description Executable
3160 process 12020 is executing new program: prog2
3161 Program exited normally.
3162 (@value{GDBP}) info inferiors
3163 Id Description Executable
3169 @value{GDBN} keeps the process bound to the same inferior. The new
3170 executable image replaces the previous executable loaded in the
3171 inferior. Restarting the inferior after the @code{exec} call, with
3172 e.g., the @code{run} command, restarts the executable the process was
3173 running after the @code{exec} call. This is the default mode.
3178 (@value{GDBP}) info inferiors
3179 Id Description Executable
3182 process 12020 is executing new program: prog2
3183 Program exited normally.
3184 (@value{GDBP}) info inferiors
3185 Id Description Executable
3192 You can use the @code{catch} command to make @value{GDBN} stop whenever
3193 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3194 Catchpoints, ,Setting Catchpoints}.
3196 @node Checkpoint/Restart
3197 @section Setting a @emph{Bookmark} to Return to Later
3202 @cindex snapshot of a process
3203 @cindex rewind program state
3205 On certain operating systems@footnote{Currently, only
3206 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3207 program's state, called a @dfn{checkpoint}, and come back to it
3210 Returning to a checkpoint effectively undoes everything that has
3211 happened in the program since the @code{checkpoint} was saved. This
3212 includes changes in memory, registers, and even (within some limits)
3213 system state. Effectively, it is like going back in time to the
3214 moment when the checkpoint was saved.
3216 Thus, if you're stepping thru a program and you think you're
3217 getting close to the point where things go wrong, you can save
3218 a checkpoint. Then, if you accidentally go too far and miss
3219 the critical statement, instead of having to restart your program
3220 from the beginning, you can just go back to the checkpoint and
3221 start again from there.
3223 This can be especially useful if it takes a lot of time or
3224 steps to reach the point where you think the bug occurs.
3226 To use the @code{checkpoint}/@code{restart} method of debugging:
3231 Save a snapshot of the debugged program's current execution state.
3232 The @code{checkpoint} command takes no arguments, but each checkpoint
3233 is assigned a small integer id, similar to a breakpoint id.
3235 @kindex info checkpoints
3236 @item info checkpoints
3237 List the checkpoints that have been saved in the current debugging
3238 session. For each checkpoint, the following information will be
3245 @item Source line, or label
3248 @kindex restart @var{checkpoint-id}
3249 @item restart @var{checkpoint-id}
3250 Restore the program state that was saved as checkpoint number
3251 @var{checkpoint-id}. All program variables, registers, stack frames
3252 etc.@: will be returned to the values that they had when the checkpoint
3253 was saved. In essence, gdb will ``wind back the clock'' to the point
3254 in time when the checkpoint was saved.
3256 Note that breakpoints, @value{GDBN} variables, command history etc.
3257 are not affected by restoring a checkpoint. In general, a checkpoint
3258 only restores things that reside in the program being debugged, not in
3261 @kindex delete checkpoint @var{checkpoint-id}
3262 @item delete checkpoint @var{checkpoint-id}
3263 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3267 Returning to a previously saved checkpoint will restore the user state
3268 of the program being debugged, plus a significant subset of the system
3269 (OS) state, including file pointers. It won't ``un-write'' data from
3270 a file, but it will rewind the file pointer to the previous location,
3271 so that the previously written data can be overwritten. For files
3272 opened in read mode, the pointer will also be restored so that the
3273 previously read data can be read again.
3275 Of course, characters that have been sent to a printer (or other
3276 external device) cannot be ``snatched back'', and characters received
3277 from eg.@: a serial device can be removed from internal program buffers,
3278 but they cannot be ``pushed back'' into the serial pipeline, ready to
3279 be received again. Similarly, the actual contents of files that have
3280 been changed cannot be restored (at this time).
3282 However, within those constraints, you actually can ``rewind'' your
3283 program to a previously saved point in time, and begin debugging it
3284 again --- and you can change the course of events so as to debug a
3285 different execution path this time.
3287 @cindex checkpoints and process id
3288 Finally, there is one bit of internal program state that will be
3289 different when you return to a checkpoint --- the program's process
3290 id. Each checkpoint will have a unique process id (or @var{pid}),
3291 and each will be different from the program's original @var{pid}.
3292 If your program has saved a local copy of its process id, this could
3293 potentially pose a problem.
3295 @subsection A Non-obvious Benefit of Using Checkpoints
3297 On some systems such as @sc{gnu}/Linux, address space randomization
3298 is performed on new processes for security reasons. This makes it
3299 difficult or impossible to set a breakpoint, or watchpoint, on an
3300 absolute address if you have to restart the program, since the
3301 absolute location of a symbol will change from one execution to the
3304 A checkpoint, however, is an @emph{identical} copy of a process.
3305 Therefore if you create a checkpoint at (eg.@:) the start of main,
3306 and simply return to that checkpoint instead of restarting the
3307 process, you can avoid the effects of address randomization and
3308 your symbols will all stay in the same place.
3311 @chapter Stopping and Continuing
3313 The principal purposes of using a debugger are so that you can stop your
3314 program before it terminates; or so that, if your program runs into
3315 trouble, you can investigate and find out why.
3317 Inside @value{GDBN}, your program may stop for any of several reasons,
3318 such as a signal, a breakpoint, or reaching a new line after a
3319 @value{GDBN} command such as @code{step}. You may then examine and
3320 change variables, set new breakpoints or remove old ones, and then
3321 continue execution. Usually, the messages shown by @value{GDBN} provide
3322 ample explanation of the status of your program---but you can also
3323 explicitly request this information at any time.
3326 @kindex info program
3328 Display information about the status of your program: whether it is
3329 running or not, what process it is, and why it stopped.
3333 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3334 * Continuing and Stepping:: Resuming execution
3335 * Skipping Over Functions and Files::
3336 Skipping over functions and files
3338 * Thread Stops:: Stopping and starting multi-thread programs
3342 @section Breakpoints, Watchpoints, and Catchpoints
3345 A @dfn{breakpoint} makes your program stop whenever a certain point in
3346 the program is reached. For each breakpoint, you can add conditions to
3347 control in finer detail whether your program stops. You can set
3348 breakpoints with the @code{break} command and its variants (@pxref{Set
3349 Breaks, ,Setting Breakpoints}), to specify the place where your program
3350 should stop by line number, function name or exact address in the
3353 On some systems, you can set breakpoints in shared libraries before
3354 the executable is run. There is a minor limitation on HP-UX systems:
3355 you must wait until the executable is run in order to set breakpoints
3356 in shared library routines that are not called directly by the program
3357 (for example, routines that are arguments in a @code{pthread_create}
3361 @cindex data breakpoints
3362 @cindex memory tracing
3363 @cindex breakpoint on memory address
3364 @cindex breakpoint on variable modification
3365 A @dfn{watchpoint} is a special breakpoint that stops your program
3366 when the value of an expression changes. The expression may be a value
3367 of a variable, or it could involve values of one or more variables
3368 combined by operators, such as @samp{a + b}. This is sometimes called
3369 @dfn{data breakpoints}. You must use a different command to set
3370 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3371 from that, you can manage a watchpoint like any other breakpoint: you
3372 enable, disable, and delete both breakpoints and watchpoints using the
3375 You can arrange to have values from your program displayed automatically
3376 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3380 @cindex breakpoint on events
3381 A @dfn{catchpoint} is another special breakpoint that stops your program
3382 when a certain kind of event occurs, such as the throwing of a C@t{++}
3383 exception or the loading of a library. As with watchpoints, you use a
3384 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3385 Catchpoints}), but aside from that, you can manage a catchpoint like any
3386 other breakpoint. (To stop when your program receives a signal, use the
3387 @code{handle} command; see @ref{Signals, ,Signals}.)
3389 @cindex breakpoint numbers
3390 @cindex numbers for breakpoints
3391 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3392 catchpoint when you create it; these numbers are successive integers
3393 starting with one. In many of the commands for controlling various
3394 features of breakpoints you use the breakpoint number to say which
3395 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3396 @dfn{disabled}; if disabled, it has no effect on your program until you
3399 @cindex breakpoint ranges
3400 @cindex ranges of breakpoints
3401 Some @value{GDBN} commands accept a range of breakpoints on which to
3402 operate. A breakpoint range is either a single breakpoint number, like
3403 @samp{5}, or two such numbers, in increasing order, separated by a
3404 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3405 all breakpoints in that range are operated on.
3408 * Set Breaks:: Setting breakpoints
3409 * Set Watchpoints:: Setting watchpoints
3410 * Set Catchpoints:: Setting catchpoints
3411 * Delete Breaks:: Deleting breakpoints
3412 * Disabling:: Disabling breakpoints
3413 * Conditions:: Break conditions
3414 * Break Commands:: Breakpoint command lists
3415 * Dynamic Printf:: Dynamic printf
3416 * Save Breakpoints:: How to save breakpoints in a file
3417 * Static Probe Points:: Listing static probe points
3418 * Error in Breakpoints:: ``Cannot insert breakpoints''
3419 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3423 @subsection Setting Breakpoints
3425 @c FIXME LMB what does GDB do if no code on line of breakpt?
3426 @c consider in particular declaration with/without initialization.
3428 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3431 @kindex b @r{(@code{break})}
3432 @vindex $bpnum@r{, convenience variable}
3433 @cindex latest breakpoint
3434 Breakpoints are set with the @code{break} command (abbreviated
3435 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3436 number of the breakpoint you've set most recently; see @ref{Convenience
3437 Vars,, Convenience Variables}, for a discussion of what you can do with
3438 convenience variables.
3441 @item break @var{location}
3442 Set a breakpoint at the given @var{location}, which can specify a
3443 function name, a line number, or an address of an instruction.
3444 (@xref{Specify Location}, for a list of all the possible ways to
3445 specify a @var{location}.) The breakpoint will stop your program just
3446 before it executes any of the code in the specified @var{location}.
3448 When using source languages that permit overloading of symbols, such as
3449 C@t{++}, a function name may refer to more than one possible place to break.
3450 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3453 It is also possible to insert a breakpoint that will stop the program
3454 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3455 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3458 When called without any arguments, @code{break} sets a breakpoint at
3459 the next instruction to be executed in the selected stack frame
3460 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3461 innermost, this makes your program stop as soon as control
3462 returns to that frame. This is similar to the effect of a
3463 @code{finish} command in the frame inside the selected frame---except
3464 that @code{finish} does not leave an active breakpoint. If you use
3465 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3466 the next time it reaches the current location; this may be useful
3469 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3470 least one instruction has been executed. If it did not do this, you
3471 would be unable to proceed past a breakpoint without first disabling the
3472 breakpoint. This rule applies whether or not the breakpoint already
3473 existed when your program stopped.
3475 @item break @dots{} if @var{cond}
3476 Set a breakpoint with condition @var{cond}; evaluate the expression
3477 @var{cond} each time the breakpoint is reached, and stop only if the
3478 value is nonzero---that is, if @var{cond} evaluates as true.
3479 @samp{@dots{}} stands for one of the possible arguments described
3480 above (or no argument) specifying where to break. @xref{Conditions,
3481 ,Break Conditions}, for more information on breakpoint conditions.
3484 @item tbreak @var{args}
3485 Set a breakpoint enabled only for one stop. @var{args} are the
3486 same as for the @code{break} command, and the breakpoint is set in the same
3487 way, but the breakpoint is automatically deleted after the first time your
3488 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3491 @cindex hardware breakpoints
3492 @item hbreak @var{args}
3493 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3494 @code{break} command and the breakpoint is set in the same way, but the
3495 breakpoint requires hardware support and some target hardware may not
3496 have this support. The main purpose of this is EPROM/ROM code
3497 debugging, so you can set a breakpoint at an instruction without
3498 changing the instruction. This can be used with the new trap-generation
3499 provided by SPARClite DSU and most x86-based targets. These targets
3500 will generate traps when a program accesses some data or instruction
3501 address that is assigned to the debug registers. However the hardware
3502 breakpoint registers can take a limited number of breakpoints. For
3503 example, on the DSU, only two data breakpoints can be set at a time, and
3504 @value{GDBN} will reject this command if more than two are used. Delete
3505 or disable unused hardware breakpoints before setting new ones
3506 (@pxref{Disabling, ,Disabling Breakpoints}).
3507 @xref{Conditions, ,Break Conditions}.
3508 For remote targets, you can restrict the number of hardware
3509 breakpoints @value{GDBN} will use, see @ref{set remote
3510 hardware-breakpoint-limit}.
3513 @item thbreak @var{args}
3514 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3515 are the same as for the @code{hbreak} command and the breakpoint is set in
3516 the same way. However, like the @code{tbreak} command,
3517 the breakpoint is automatically deleted after the
3518 first time your program stops there. Also, like the @code{hbreak}
3519 command, the breakpoint requires hardware support and some target hardware
3520 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3521 See also @ref{Conditions, ,Break Conditions}.
3524 @cindex regular expression
3525 @cindex breakpoints at functions matching a regexp
3526 @cindex set breakpoints in many functions
3527 @item rbreak @var{regex}
3528 Set breakpoints on all functions matching the regular expression
3529 @var{regex}. This command sets an unconditional breakpoint on all
3530 matches, printing a list of all breakpoints it set. Once these
3531 breakpoints are set, they are treated just like the breakpoints set with
3532 the @code{break} command. You can delete them, disable them, or make
3533 them conditional the same way as any other breakpoint.
3535 The syntax of the regular expression is the standard one used with tools
3536 like @file{grep}. Note that this is different from the syntax used by
3537 shells, so for instance @code{foo*} matches all functions that include
3538 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3539 @code{.*} leading and trailing the regular expression you supply, so to
3540 match only functions that begin with @code{foo}, use @code{^foo}.
3542 @cindex non-member C@t{++} functions, set breakpoint in
3543 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3544 breakpoints on overloaded functions that are not members of any special
3547 @cindex set breakpoints on all functions
3548 The @code{rbreak} command can be used to set breakpoints in
3549 @strong{all} the functions in a program, like this:
3552 (@value{GDBP}) rbreak .
3555 @item rbreak @var{file}:@var{regex}
3556 If @code{rbreak} is called with a filename qualification, it limits
3557 the search for functions matching the given regular expression to the
3558 specified @var{file}. This can be used, for example, to set breakpoints on
3559 every function in a given file:
3562 (@value{GDBP}) rbreak file.c:.
3565 The colon separating the filename qualifier from the regex may
3566 optionally be surrounded by spaces.
3568 @kindex info breakpoints
3569 @cindex @code{$_} and @code{info breakpoints}
3570 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3571 @itemx info break @r{[}@var{n}@dots{}@r{]}
3572 Print a table of all breakpoints, watchpoints, and catchpoints set and
3573 not deleted. Optional argument @var{n} means print information only
3574 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3575 For each breakpoint, following columns are printed:
3578 @item Breakpoint Numbers
3580 Breakpoint, watchpoint, or catchpoint.
3582 Whether the breakpoint is marked to be disabled or deleted when hit.
3583 @item Enabled or Disabled
3584 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3585 that are not enabled.
3587 Where the breakpoint is in your program, as a memory address. For a
3588 pending breakpoint whose address is not yet known, this field will
3589 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3590 library that has the symbol or line referred by breakpoint is loaded.
3591 See below for details. A breakpoint with several locations will
3592 have @samp{<MULTIPLE>} in this field---see below for details.
3594 Where the breakpoint is in the source for your program, as a file and
3595 line number. For a pending breakpoint, the original string passed to
3596 the breakpoint command will be listed as it cannot be resolved until
3597 the appropriate shared library is loaded in the future.
3601 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3602 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3603 @value{GDBN} on the host's side. If it is ``target'', then the condition
3604 is evaluated by the target. The @code{info break} command shows
3605 the condition on the line following the affected breakpoint, together with
3606 its condition evaluation mode in between parentheses.
3608 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3609 allowed to have a condition specified for it. The condition is not parsed for
3610 validity until a shared library is loaded that allows the pending
3611 breakpoint to resolve to a valid location.
3614 @code{info break} with a breakpoint
3615 number @var{n} as argument lists only that breakpoint. The
3616 convenience variable @code{$_} and the default examining-address for
3617 the @code{x} command are set to the address of the last breakpoint
3618 listed (@pxref{Memory, ,Examining Memory}).
3621 @code{info break} displays a count of the number of times the breakpoint
3622 has been hit. This is especially useful in conjunction with the
3623 @code{ignore} command. You can ignore a large number of breakpoint
3624 hits, look at the breakpoint info to see how many times the breakpoint
3625 was hit, and then run again, ignoring one less than that number. This
3626 will get you quickly to the last hit of that breakpoint.
3629 For a breakpoints with an enable count (xref) greater than 1,
3630 @code{info break} also displays that count.
3634 @value{GDBN} allows you to set any number of breakpoints at the same place in
3635 your program. There is nothing silly or meaningless about this. When
3636 the breakpoints are conditional, this is even useful
3637 (@pxref{Conditions, ,Break Conditions}).
3639 @cindex multiple locations, breakpoints
3640 @cindex breakpoints, multiple locations
3641 It is possible that a breakpoint corresponds to several locations
3642 in your program. Examples of this situation are:
3646 Multiple functions in the program may have the same name.
3649 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3650 instances of the function body, used in different cases.
3653 For a C@t{++} template function, a given line in the function can
3654 correspond to any number of instantiations.
3657 For an inlined function, a given source line can correspond to
3658 several places where that function is inlined.
3661 In all those cases, @value{GDBN} will insert a breakpoint at all
3662 the relevant locations.
3664 A breakpoint with multiple locations is displayed in the breakpoint
3665 table using several rows---one header row, followed by one row for
3666 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3667 address column. The rows for individual locations contain the actual
3668 addresses for locations, and show the functions to which those
3669 locations belong. The number column for a location is of the form
3670 @var{breakpoint-number}.@var{location-number}.
3675 Num Type Disp Enb Address What
3676 1 breakpoint keep y <MULTIPLE>
3678 breakpoint already hit 1 time
3679 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3680 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3683 Each location can be individually enabled or disabled by passing
3684 @var{breakpoint-number}.@var{location-number} as argument to the
3685 @code{enable} and @code{disable} commands. Note that you cannot
3686 delete the individual locations from the list, you can only delete the
3687 entire list of locations that belong to their parent breakpoint (with
3688 the @kbd{delete @var{num}} command, where @var{num} is the number of
3689 the parent breakpoint, 1 in the above example). Disabling or enabling
3690 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3691 that belong to that breakpoint.
3693 @cindex pending breakpoints
3694 It's quite common to have a breakpoint inside a shared library.
3695 Shared libraries can be loaded and unloaded explicitly,
3696 and possibly repeatedly, as the program is executed. To support
3697 this use case, @value{GDBN} updates breakpoint locations whenever
3698 any shared library is loaded or unloaded. Typically, you would
3699 set a breakpoint in a shared library at the beginning of your
3700 debugging session, when the library is not loaded, and when the
3701 symbols from the library are not available. When you try to set
3702 breakpoint, @value{GDBN} will ask you if you want to set
3703 a so called @dfn{pending breakpoint}---breakpoint whose address
3704 is not yet resolved.
3706 After the program is run, whenever a new shared library is loaded,
3707 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3708 shared library contains the symbol or line referred to by some
3709 pending breakpoint, that breakpoint is resolved and becomes an
3710 ordinary breakpoint. When a library is unloaded, all breakpoints
3711 that refer to its symbols or source lines become pending again.
3713 This logic works for breakpoints with multiple locations, too. For
3714 example, if you have a breakpoint in a C@t{++} template function, and
3715 a newly loaded shared library has an instantiation of that template,
3716 a new location is added to the list of locations for the breakpoint.
3718 Except for having unresolved address, pending breakpoints do not
3719 differ from regular breakpoints. You can set conditions or commands,
3720 enable and disable them and perform other breakpoint operations.
3722 @value{GDBN} provides some additional commands for controlling what
3723 happens when the @samp{break} command cannot resolve breakpoint
3724 address specification to an address:
3726 @kindex set breakpoint pending
3727 @kindex show breakpoint pending
3729 @item set breakpoint pending auto
3730 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3731 location, it queries you whether a pending breakpoint should be created.
3733 @item set breakpoint pending on
3734 This indicates that an unrecognized breakpoint location should automatically
3735 result in a pending breakpoint being created.
3737 @item set breakpoint pending off
3738 This indicates that pending breakpoints are not to be created. Any
3739 unrecognized breakpoint location results in an error. This setting does
3740 not affect any pending breakpoints previously created.
3742 @item show breakpoint pending
3743 Show the current behavior setting for creating pending breakpoints.
3746 The settings above only affect the @code{break} command and its
3747 variants. Once breakpoint is set, it will be automatically updated
3748 as shared libraries are loaded and unloaded.
3750 @cindex automatic hardware breakpoints
3751 For some targets, @value{GDBN} can automatically decide if hardware or
3752 software breakpoints should be used, depending on whether the
3753 breakpoint address is read-only or read-write. This applies to
3754 breakpoints set with the @code{break} command as well as to internal
3755 breakpoints set by commands like @code{next} and @code{finish}. For
3756 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3759 You can control this automatic behaviour with the following commands::
3761 @kindex set breakpoint auto-hw
3762 @kindex show breakpoint auto-hw
3764 @item set breakpoint auto-hw on
3765 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3766 will try to use the target memory map to decide if software or hardware
3767 breakpoint must be used.
3769 @item set breakpoint auto-hw off
3770 This indicates @value{GDBN} should not automatically select breakpoint
3771 type. If the target provides a memory map, @value{GDBN} will warn when
3772 trying to set software breakpoint at a read-only address.
3775 @value{GDBN} normally implements breakpoints by replacing the program code
3776 at the breakpoint address with a special instruction, which, when
3777 executed, given control to the debugger. By default, the program
3778 code is so modified only when the program is resumed. As soon as
3779 the program stops, @value{GDBN} restores the original instructions. This
3780 behaviour guards against leaving breakpoints inserted in the
3781 target should gdb abrubptly disconnect. However, with slow remote
3782 targets, inserting and removing breakpoint can reduce the performance.
3783 This behavior can be controlled with the following commands::
3785 @kindex set breakpoint always-inserted
3786 @kindex show breakpoint always-inserted
3788 @item set breakpoint always-inserted off
3789 All breakpoints, including newly added by the user, are inserted in
3790 the target only when the target is resumed. All breakpoints are
3791 removed from the target when it stops.
3793 @item set breakpoint always-inserted on
3794 Causes all breakpoints to be inserted in the target at all times. If
3795 the user adds a new breakpoint, or changes an existing breakpoint, the
3796 breakpoints in the target are updated immediately. A breakpoint is
3797 removed from the target only when breakpoint itself is removed.
3799 @cindex non-stop mode, and @code{breakpoint always-inserted}
3800 @item set breakpoint always-inserted auto
3801 This is the default mode. If @value{GDBN} is controlling the inferior
3802 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3803 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3804 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3805 @code{breakpoint always-inserted} mode is off.
3808 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3809 when a breakpoint breaks. If the condition is true, then the process being
3810 debugged stops, otherwise the process is resumed.
3812 If the target supports evaluating conditions on its end, @value{GDBN} may
3813 download the breakpoint, together with its conditions, to it.
3815 This feature can be controlled via the following commands:
3817 @kindex set breakpoint condition-evaluation
3818 @kindex show breakpoint condition-evaluation
3820 @item set breakpoint condition-evaluation host
3821 This option commands @value{GDBN} to evaluate the breakpoint
3822 conditions on the host's side. Unconditional breakpoints are sent to
3823 the target which in turn receives the triggers and reports them back to GDB
3824 for condition evaluation. This is the standard evaluation mode.
3826 @item set breakpoint condition-evaluation target
3827 This option commands @value{GDBN} to download breakpoint conditions
3828 to the target at the moment of their insertion. The target
3829 is responsible for evaluating the conditional expression and reporting
3830 breakpoint stop events back to @value{GDBN} whenever the condition
3831 is true. Due to limitations of target-side evaluation, some conditions
3832 cannot be evaluated there, e.g., conditions that depend on local data
3833 that is only known to the host. Examples include
3834 conditional expressions involving convenience variables, complex types
3835 that cannot be handled by the agent expression parser and expressions
3836 that are too long to be sent over to the target, specially when the
3837 target is a remote system. In these cases, the conditions will be
3838 evaluated by @value{GDBN}.
3840 @item set breakpoint condition-evaluation auto
3841 This is the default mode. If the target supports evaluating breakpoint
3842 conditions on its end, @value{GDBN} will download breakpoint conditions to
3843 the target (limitations mentioned previously apply). If the target does
3844 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3845 to evaluating all these conditions on the host's side.
3849 @cindex negative breakpoint numbers
3850 @cindex internal @value{GDBN} breakpoints
3851 @value{GDBN} itself sometimes sets breakpoints in your program for
3852 special purposes, such as proper handling of @code{longjmp} (in C
3853 programs). These internal breakpoints are assigned negative numbers,
3854 starting with @code{-1}; @samp{info breakpoints} does not display them.
3855 You can see these breakpoints with the @value{GDBN} maintenance command
3856 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3859 @node Set Watchpoints
3860 @subsection Setting Watchpoints
3862 @cindex setting watchpoints
3863 You can use a watchpoint to stop execution whenever the value of an
3864 expression changes, without having to predict a particular place where
3865 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3866 The expression may be as simple as the value of a single variable, or
3867 as complex as many variables combined by operators. Examples include:
3871 A reference to the value of a single variable.
3874 An address cast to an appropriate data type. For example,
3875 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3876 address (assuming an @code{int} occupies 4 bytes).
3879 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3880 expression can use any operators valid in the program's native
3881 language (@pxref{Languages}).
3884 You can set a watchpoint on an expression even if the expression can
3885 not be evaluated yet. For instance, you can set a watchpoint on
3886 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3887 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3888 the expression produces a valid value. If the expression becomes
3889 valid in some other way than changing a variable (e.g.@: if the memory
3890 pointed to by @samp{*global_ptr} becomes readable as the result of a
3891 @code{malloc} call), @value{GDBN} may not stop until the next time
3892 the expression changes.
3894 @cindex software watchpoints
3895 @cindex hardware watchpoints
3896 Depending on your system, watchpoints may be implemented in software or
3897 hardware. @value{GDBN} does software watchpointing by single-stepping your
3898 program and testing the variable's value each time, which is hundreds of
3899 times slower than normal execution. (But this may still be worth it, to
3900 catch errors where you have no clue what part of your program is the
3903 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3904 x86-based targets, @value{GDBN} includes support for hardware
3905 watchpoints, which do not slow down the running of your program.
3909 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3910 Set a watchpoint for an expression. @value{GDBN} will break when the
3911 expression @var{expr} is written into by the program and its value
3912 changes. The simplest (and the most popular) use of this command is
3913 to watch the value of a single variable:
3916 (@value{GDBP}) watch foo
3919 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3920 argument, @value{GDBN} breaks only when the thread identified by
3921 @var{threadnum} changes the value of @var{expr}. If any other threads
3922 change the value of @var{expr}, @value{GDBN} will not break. Note
3923 that watchpoints restricted to a single thread in this way only work
3924 with Hardware Watchpoints.
3926 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3927 (see below). The @code{-location} argument tells @value{GDBN} to
3928 instead watch the memory referred to by @var{expr}. In this case,
3929 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3930 and watch the memory at that address. The type of the result is used
3931 to determine the size of the watched memory. If the expression's
3932 result does not have an address, then @value{GDBN} will print an
3935 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3936 of masked watchpoints, if the current architecture supports this
3937 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3938 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3939 to an address to watch. The mask specifies that some bits of an address
3940 (the bits which are reset in the mask) should be ignored when matching
3941 the address accessed by the inferior against the watchpoint address.
3942 Thus, a masked watchpoint watches many addresses simultaneously---those
3943 addresses whose unmasked bits are identical to the unmasked bits in the
3944 watchpoint address. The @code{mask} argument implies @code{-location}.
3948 (@value{GDBP}) watch foo mask 0xffff00ff
3949 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3953 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3954 Set a watchpoint that will break when the value of @var{expr} is read
3958 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3959 Set a watchpoint that will break when @var{expr} is either read from
3960 or written into by the program.
3962 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3963 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3964 This command prints a list of watchpoints, using the same format as
3965 @code{info break} (@pxref{Set Breaks}).
3968 If you watch for a change in a numerically entered address you need to
3969 dereference it, as the address itself is just a constant number which will
3970 never change. @value{GDBN} refuses to create a watchpoint that watches
3971 a never-changing value:
3974 (@value{GDBP}) watch 0x600850
3975 Cannot watch constant value 0x600850.
3976 (@value{GDBP}) watch *(int *) 0x600850
3977 Watchpoint 1: *(int *) 6293584
3980 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3981 watchpoints execute very quickly, and the debugger reports a change in
3982 value at the exact instruction where the change occurs. If @value{GDBN}
3983 cannot set a hardware watchpoint, it sets a software watchpoint, which
3984 executes more slowly and reports the change in value at the next
3985 @emph{statement}, not the instruction, after the change occurs.
3987 @cindex use only software watchpoints
3988 You can force @value{GDBN} to use only software watchpoints with the
3989 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3990 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3991 the underlying system supports them. (Note that hardware-assisted
3992 watchpoints that were set @emph{before} setting
3993 @code{can-use-hw-watchpoints} to zero will still use the hardware
3994 mechanism of watching expression values.)
3997 @item set can-use-hw-watchpoints
3998 @kindex set can-use-hw-watchpoints
3999 Set whether or not to use hardware watchpoints.
4001 @item show can-use-hw-watchpoints
4002 @kindex show can-use-hw-watchpoints
4003 Show the current mode of using hardware watchpoints.
4006 For remote targets, you can restrict the number of hardware
4007 watchpoints @value{GDBN} will use, see @ref{set remote
4008 hardware-breakpoint-limit}.
4010 When you issue the @code{watch} command, @value{GDBN} reports
4013 Hardware watchpoint @var{num}: @var{expr}
4017 if it was able to set a hardware watchpoint.
4019 Currently, the @code{awatch} and @code{rwatch} commands can only set
4020 hardware watchpoints, because accesses to data that don't change the
4021 value of the watched expression cannot be detected without examining
4022 every instruction as it is being executed, and @value{GDBN} does not do
4023 that currently. If @value{GDBN} finds that it is unable to set a
4024 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4025 will print a message like this:
4028 Expression cannot be implemented with read/access watchpoint.
4031 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4032 data type of the watched expression is wider than what a hardware
4033 watchpoint on the target machine can handle. For example, some systems
4034 can only watch regions that are up to 4 bytes wide; on such systems you
4035 cannot set hardware watchpoints for an expression that yields a
4036 double-precision floating-point number (which is typically 8 bytes
4037 wide). As a work-around, it might be possible to break the large region
4038 into a series of smaller ones and watch them with separate watchpoints.
4040 If you set too many hardware watchpoints, @value{GDBN} might be unable
4041 to insert all of them when you resume the execution of your program.
4042 Since the precise number of active watchpoints is unknown until such
4043 time as the program is about to be resumed, @value{GDBN} might not be
4044 able to warn you about this when you set the watchpoints, and the
4045 warning will be printed only when the program is resumed:
4048 Hardware watchpoint @var{num}: Could not insert watchpoint
4052 If this happens, delete or disable some of the watchpoints.
4054 Watching complex expressions that reference many variables can also
4055 exhaust the resources available for hardware-assisted watchpoints.
4056 That's because @value{GDBN} needs to watch every variable in the
4057 expression with separately allocated resources.
4059 If you call a function interactively using @code{print} or @code{call},
4060 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4061 kind of breakpoint or the call completes.
4063 @value{GDBN} automatically deletes watchpoints that watch local
4064 (automatic) variables, or expressions that involve such variables, when
4065 they go out of scope, that is, when the execution leaves the block in
4066 which these variables were defined. In particular, when the program
4067 being debugged terminates, @emph{all} local variables go out of scope,
4068 and so only watchpoints that watch global variables remain set. If you
4069 rerun the program, you will need to set all such watchpoints again. One
4070 way of doing that would be to set a code breakpoint at the entry to the
4071 @code{main} function and when it breaks, set all the watchpoints.
4073 @cindex watchpoints and threads
4074 @cindex threads and watchpoints
4075 In multi-threaded programs, watchpoints will detect changes to the
4076 watched expression from every thread.
4079 @emph{Warning:} In multi-threaded programs, software watchpoints
4080 have only limited usefulness. If @value{GDBN} creates a software
4081 watchpoint, it can only watch the value of an expression @emph{in a
4082 single thread}. If you are confident that the expression can only
4083 change due to the current thread's activity (and if you are also
4084 confident that no other thread can become current), then you can use
4085 software watchpoints as usual. However, @value{GDBN} may not notice
4086 when a non-current thread's activity changes the expression. (Hardware
4087 watchpoints, in contrast, watch an expression in all threads.)
4090 @xref{set remote hardware-watchpoint-limit}.
4092 @node Set Catchpoints
4093 @subsection Setting Catchpoints
4094 @cindex catchpoints, setting
4095 @cindex exception handlers
4096 @cindex event handling
4098 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4099 kinds of program events, such as C@t{++} exceptions or the loading of a
4100 shared library. Use the @code{catch} command to set a catchpoint.
4104 @item catch @var{event}
4105 Stop when @var{event} occurs. @var{event} can be any of the following:
4108 @item throw @r{[}@var{regexp}@r{]}
4109 @itemx rethrow @r{[}@var{regexp}@r{]}
4110 @itemx catch @r{[}@var{regexp}@r{]}
4112 @kindex catch rethrow
4114 @cindex stop on C@t{++} exceptions
4115 The throwing, re-throwing, or catching of a C@t{++} exception.
4117 If @var{regexp} is given, then only exceptions whose type matches the
4118 regular expression will be caught.
4120 @vindex $_exception@r{, convenience variable}
4121 The convenience variable @code{$_exception} is available at an
4122 exception-related catchpoint, on some systems. This holds the
4123 exception being thrown.
4125 There are currently some limitations to C@t{++} exception handling in
4130 The support for these commands is system-dependent. Currently, only
4131 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4135 The regular expression feature and the @code{$_exception} convenience
4136 variable rely on the presence of some SDT probes in @code{libstdc++}.
4137 If these probes are not present, then these features cannot be used.
4138 These probes were first available in the GCC 4.8 release, but whether
4139 or not they are available in your GCC also depends on how it was
4143 The @code{$_exception} convenience variable is only valid at the
4144 instruction at which an exception-related catchpoint is set.
4147 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4148 location in the system library which implements runtime exception
4149 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4150 (@pxref{Selection}) to get to your code.
4153 If you call a function interactively, @value{GDBN} normally returns
4154 control to you when the function has finished executing. If the call
4155 raises an exception, however, the call may bypass the mechanism that
4156 returns control to you and cause your program either to abort or to
4157 simply continue running until it hits a breakpoint, catches a signal
4158 that @value{GDBN} is listening for, or exits. This is the case even if
4159 you set a catchpoint for the exception; catchpoints on exceptions are
4160 disabled within interactive calls. @xref{Calling}, for information on
4161 controlling this with @code{set unwind-on-terminating-exception}.
4164 You cannot raise an exception interactively.
4167 You cannot install an exception handler interactively.
4171 @kindex catch exception
4172 @cindex Ada exception catching
4173 @cindex catch Ada exceptions
4174 An Ada exception being raised. If an exception name is specified
4175 at the end of the command (eg @code{catch exception Program_Error}),
4176 the debugger will stop only when this specific exception is raised.
4177 Otherwise, the debugger stops execution when any Ada exception is raised.
4179 When inserting an exception catchpoint on a user-defined exception whose
4180 name is identical to one of the exceptions defined by the language, the
4181 fully qualified name must be used as the exception name. Otherwise,
4182 @value{GDBN} will assume that it should stop on the pre-defined exception
4183 rather than the user-defined one. For instance, assuming an exception
4184 called @code{Constraint_Error} is defined in package @code{Pck}, then
4185 the command to use to catch such exceptions is @kbd{catch exception
4186 Pck.Constraint_Error}.
4188 @item exception unhandled
4189 @kindex catch exception unhandled
4190 An exception that was raised but is not handled by the program.
4193 @kindex catch assert
4194 A failed Ada assertion.
4198 @cindex break on fork/exec
4199 A call to @code{exec}. This is currently only available for HP-UX
4203 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4204 @kindex catch syscall
4205 @cindex break on a system call.
4206 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4207 syscall is a mechanism for application programs to request a service
4208 from the operating system (OS) or one of the OS system services.
4209 @value{GDBN} can catch some or all of the syscalls issued by the
4210 debuggee, and show the related information for each syscall. If no
4211 argument is specified, calls to and returns from all system calls
4214 @var{name} can be any system call name that is valid for the
4215 underlying OS. Just what syscalls are valid depends on the OS. On
4216 GNU and Unix systems, you can find the full list of valid syscall
4217 names on @file{/usr/include/asm/unistd.h}.
4219 @c For MS-Windows, the syscall names and the corresponding numbers
4220 @c can be found, e.g., on this URL:
4221 @c http://www.metasploit.com/users/opcode/syscalls.html
4222 @c but we don't support Windows syscalls yet.
4224 Normally, @value{GDBN} knows in advance which syscalls are valid for
4225 each OS, so you can use the @value{GDBN} command-line completion
4226 facilities (@pxref{Completion,, command completion}) to list the
4229 You may also specify the system call numerically. A syscall's
4230 number is the value passed to the OS's syscall dispatcher to
4231 identify the requested service. When you specify the syscall by its
4232 name, @value{GDBN} uses its database of syscalls to convert the name
4233 into the corresponding numeric code, but using the number directly
4234 may be useful if @value{GDBN}'s database does not have the complete
4235 list of syscalls on your system (e.g., because @value{GDBN} lags
4236 behind the OS upgrades).
4238 The example below illustrates how this command works if you don't provide
4242 (@value{GDBP}) catch syscall
4243 Catchpoint 1 (syscall)
4245 Starting program: /tmp/catch-syscall
4247 Catchpoint 1 (call to syscall 'close'), \
4248 0xffffe424 in __kernel_vsyscall ()
4252 Catchpoint 1 (returned from syscall 'close'), \
4253 0xffffe424 in __kernel_vsyscall ()
4257 Here is an example of catching a system call by name:
4260 (@value{GDBP}) catch syscall chroot
4261 Catchpoint 1 (syscall 'chroot' [61])
4263 Starting program: /tmp/catch-syscall
4265 Catchpoint 1 (call to syscall 'chroot'), \
4266 0xffffe424 in __kernel_vsyscall ()
4270 Catchpoint 1 (returned from syscall 'chroot'), \
4271 0xffffe424 in __kernel_vsyscall ()
4275 An example of specifying a system call numerically. In the case
4276 below, the syscall number has a corresponding entry in the XML
4277 file, so @value{GDBN} finds its name and prints it:
4280 (@value{GDBP}) catch syscall 252
4281 Catchpoint 1 (syscall(s) 'exit_group')
4283 Starting program: /tmp/catch-syscall
4285 Catchpoint 1 (call to syscall 'exit_group'), \
4286 0xffffe424 in __kernel_vsyscall ()
4290 Program exited normally.
4294 However, there can be situations when there is no corresponding name
4295 in XML file for that syscall number. In this case, @value{GDBN} prints
4296 a warning message saying that it was not able to find the syscall name,
4297 but the catchpoint will be set anyway. See the example below:
4300 (@value{GDBP}) catch syscall 764
4301 warning: The number '764' does not represent a known syscall.
4302 Catchpoint 2 (syscall 764)
4306 If you configure @value{GDBN} using the @samp{--without-expat} option,
4307 it will not be able to display syscall names. Also, if your
4308 architecture does not have an XML file describing its system calls,
4309 you will not be able to see the syscall names. It is important to
4310 notice that these two features are used for accessing the syscall
4311 name database. In either case, you will see a warning like this:
4314 (@value{GDBP}) catch syscall
4315 warning: Could not open "syscalls/i386-linux.xml"
4316 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4317 GDB will not be able to display syscall names.
4318 Catchpoint 1 (syscall)
4322 Of course, the file name will change depending on your architecture and system.
4324 Still using the example above, you can also try to catch a syscall by its
4325 number. In this case, you would see something like:
4328 (@value{GDBP}) catch syscall 252
4329 Catchpoint 1 (syscall(s) 252)
4332 Again, in this case @value{GDBN} would not be able to display syscall's names.
4336 A call to @code{fork}. This is currently only available for HP-UX
4341 A call to @code{vfork}. This is currently only available for HP-UX
4344 @item load @r{[}regexp@r{]}
4345 @itemx unload @r{[}regexp@r{]}
4347 @kindex catch unload
4348 The loading or unloading of a shared library. If @var{regexp} is
4349 given, then the catchpoint will stop only if the regular expression
4350 matches one of the affected libraries.
4352 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4353 @kindex catch signal
4354 The delivery of a signal.
4356 With no arguments, this catchpoint will catch any signal that is not
4357 used internally by @value{GDBN}, specifically, all signals except
4358 @samp{SIGTRAP} and @samp{SIGINT}.
4360 With the argument @samp{all}, all signals, including those used by
4361 @value{GDBN}, will be caught. This argument cannot be used with other
4364 Otherwise, the arguments are a list of signal names as given to
4365 @code{handle} (@pxref{Signals}). Only signals specified in this list
4368 One reason that @code{catch signal} can be more useful than
4369 @code{handle} is that you can attach commands and conditions to the
4372 When a signal is caught by a catchpoint, the signal's @code{stop} and
4373 @code{print} settings, as specified by @code{handle}, are ignored.
4374 However, whether the signal is still delivered to the inferior depends
4375 on the @code{pass} setting; this can be changed in the catchpoint's
4380 @item tcatch @var{event}
4382 Set a catchpoint that is enabled only for one stop. The catchpoint is
4383 automatically deleted after the first time the event is caught.
4387 Use the @code{info break} command to list the current catchpoints.
4391 @subsection Deleting Breakpoints
4393 @cindex clearing breakpoints, watchpoints, catchpoints
4394 @cindex deleting breakpoints, watchpoints, catchpoints
4395 It is often necessary to eliminate a breakpoint, watchpoint, or
4396 catchpoint once it has done its job and you no longer want your program
4397 to stop there. This is called @dfn{deleting} the breakpoint. A
4398 breakpoint that has been deleted no longer exists; it is forgotten.
4400 With the @code{clear} command you can delete breakpoints according to
4401 where they are in your program. With the @code{delete} command you can
4402 delete individual breakpoints, watchpoints, or catchpoints by specifying
4403 their breakpoint numbers.
4405 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4406 automatically ignores breakpoints on the first instruction to be executed
4407 when you continue execution without changing the execution address.
4412 Delete any breakpoints at the next instruction to be executed in the
4413 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4414 the innermost frame is selected, this is a good way to delete a
4415 breakpoint where your program just stopped.
4417 @item clear @var{location}
4418 Delete any breakpoints set at the specified @var{location}.
4419 @xref{Specify Location}, for the various forms of @var{location}; the
4420 most useful ones are listed below:
4423 @item clear @var{function}
4424 @itemx clear @var{filename}:@var{function}
4425 Delete any breakpoints set at entry to the named @var{function}.
4427 @item clear @var{linenum}
4428 @itemx clear @var{filename}:@var{linenum}
4429 Delete any breakpoints set at or within the code of the specified
4430 @var{linenum} of the specified @var{filename}.
4433 @cindex delete breakpoints
4435 @kindex d @r{(@code{delete})}
4436 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4437 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4438 ranges specified as arguments. If no argument is specified, delete all
4439 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4440 confirm off}). You can abbreviate this command as @code{d}.
4444 @subsection Disabling Breakpoints
4446 @cindex enable/disable a breakpoint
4447 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4448 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4449 it had been deleted, but remembers the information on the breakpoint so
4450 that you can @dfn{enable} it again later.
4452 You disable and enable breakpoints, watchpoints, and catchpoints with
4453 the @code{enable} and @code{disable} commands, optionally specifying
4454 one or more breakpoint numbers as arguments. Use @code{info break} to
4455 print a list of all breakpoints, watchpoints, and catchpoints if you
4456 do not know which numbers to use.
4458 Disabling and enabling a breakpoint that has multiple locations
4459 affects all of its locations.
4461 A breakpoint, watchpoint, or catchpoint can have any of several
4462 different states of enablement:
4466 Enabled. The breakpoint stops your program. A breakpoint set
4467 with the @code{break} command starts out in this state.
4469 Disabled. The breakpoint has no effect on your program.
4471 Enabled once. The breakpoint stops your program, but then becomes
4474 Enabled for a count. The breakpoint stops your program for the next
4475 N times, then becomes disabled.
4477 Enabled for deletion. The breakpoint stops your program, but
4478 immediately after it does so it is deleted permanently. A breakpoint
4479 set with the @code{tbreak} command starts out in this state.
4482 You can use the following commands to enable or disable breakpoints,
4483 watchpoints, and catchpoints:
4487 @kindex dis @r{(@code{disable})}
4488 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4489 Disable the specified breakpoints---or all breakpoints, if none are
4490 listed. A disabled breakpoint has no effect but is not forgotten. All
4491 options such as ignore-counts, conditions and commands are remembered in
4492 case the breakpoint is enabled again later. You may abbreviate
4493 @code{disable} as @code{dis}.
4496 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4497 Enable the specified breakpoints (or all defined breakpoints). They
4498 become effective once again in stopping your program.
4500 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4501 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4502 of these breakpoints immediately after stopping your program.
4504 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4505 Enable the specified breakpoints temporarily. @value{GDBN} records
4506 @var{count} with each of the specified breakpoints, and decrements a
4507 breakpoint's count when it is hit. When any count reaches 0,
4508 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4509 count (@pxref{Conditions, ,Break Conditions}), that will be
4510 decremented to 0 before @var{count} is affected.
4512 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4513 Enable the specified breakpoints to work once, then die. @value{GDBN}
4514 deletes any of these breakpoints as soon as your program stops there.
4515 Breakpoints set by the @code{tbreak} command start out in this state.
4518 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4519 @c confusing: tbreak is also initially enabled.
4520 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4521 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4522 subsequently, they become disabled or enabled only when you use one of
4523 the commands above. (The command @code{until} can set and delete a
4524 breakpoint of its own, but it does not change the state of your other
4525 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4529 @subsection Break Conditions
4530 @cindex conditional breakpoints
4531 @cindex breakpoint conditions
4533 @c FIXME what is scope of break condition expr? Context where wanted?
4534 @c in particular for a watchpoint?
4535 The simplest sort of breakpoint breaks every time your program reaches a
4536 specified place. You can also specify a @dfn{condition} for a
4537 breakpoint. A condition is just a Boolean expression in your
4538 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4539 a condition evaluates the expression each time your program reaches it,
4540 and your program stops only if the condition is @emph{true}.
4542 This is the converse of using assertions for program validation; in that
4543 situation, you want to stop when the assertion is violated---that is,
4544 when the condition is false. In C, if you want to test an assertion expressed
4545 by the condition @var{assert}, you should set the condition
4546 @samp{! @var{assert}} on the appropriate breakpoint.
4548 Conditions are also accepted for watchpoints; you may not need them,
4549 since a watchpoint is inspecting the value of an expression anyhow---but
4550 it might be simpler, say, to just set a watchpoint on a variable name,
4551 and specify a condition that tests whether the new value is an interesting
4554 Break conditions can have side effects, and may even call functions in
4555 your program. This can be useful, for example, to activate functions
4556 that log program progress, or to use your own print functions to
4557 format special data structures. The effects are completely predictable
4558 unless there is another enabled breakpoint at the same address. (In
4559 that case, @value{GDBN} might see the other breakpoint first and stop your
4560 program without checking the condition of this one.) Note that
4561 breakpoint commands are usually more convenient and flexible than break
4563 purpose of performing side effects when a breakpoint is reached
4564 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4566 Breakpoint conditions can also be evaluated on the target's side if
4567 the target supports it. Instead of evaluating the conditions locally,
4568 @value{GDBN} encodes the expression into an agent expression
4569 (@pxref{Agent Expressions}) suitable for execution on the target,
4570 independently of @value{GDBN}. Global variables become raw memory
4571 locations, locals become stack accesses, and so forth.
4573 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4574 when its condition evaluates to true. This mechanism may provide faster
4575 response times depending on the performance characteristics of the target
4576 since it does not need to keep @value{GDBN} informed about
4577 every breakpoint trigger, even those with false conditions.
4579 Break conditions can be specified when a breakpoint is set, by using
4580 @samp{if} in the arguments to the @code{break} command. @xref{Set
4581 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4582 with the @code{condition} command.
4584 You can also use the @code{if} keyword with the @code{watch} command.
4585 The @code{catch} command does not recognize the @code{if} keyword;
4586 @code{condition} is the only way to impose a further condition on a
4591 @item condition @var{bnum} @var{expression}
4592 Specify @var{expression} as the break condition for breakpoint,
4593 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4594 breakpoint @var{bnum} stops your program only if the value of
4595 @var{expression} is true (nonzero, in C). When you use
4596 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4597 syntactic correctness, and to determine whether symbols in it have
4598 referents in the context of your breakpoint. If @var{expression} uses
4599 symbols not referenced in the context of the breakpoint, @value{GDBN}
4600 prints an error message:
4603 No symbol "foo" in current context.
4608 not actually evaluate @var{expression} at the time the @code{condition}
4609 command (or a command that sets a breakpoint with a condition, like
4610 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4612 @item condition @var{bnum}
4613 Remove the condition from breakpoint number @var{bnum}. It becomes
4614 an ordinary unconditional breakpoint.
4617 @cindex ignore count (of breakpoint)
4618 A special case of a breakpoint condition is to stop only when the
4619 breakpoint has been reached a certain number of times. This is so
4620 useful that there is a special way to do it, using the @dfn{ignore
4621 count} of the breakpoint. Every breakpoint has an ignore count, which
4622 is an integer. Most of the time, the ignore count is zero, and
4623 therefore has no effect. But if your program reaches a breakpoint whose
4624 ignore count is positive, then instead of stopping, it just decrements
4625 the ignore count by one and continues. As a result, if the ignore count
4626 value is @var{n}, the breakpoint does not stop the next @var{n} times
4627 your program reaches it.
4631 @item ignore @var{bnum} @var{count}
4632 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4633 The next @var{count} times the breakpoint is reached, your program's
4634 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4637 To make the breakpoint stop the next time it is reached, specify
4640 When you use @code{continue} to resume execution of your program from a
4641 breakpoint, you can specify an ignore count directly as an argument to
4642 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4643 Stepping,,Continuing and Stepping}.
4645 If a breakpoint has a positive ignore count and a condition, the
4646 condition is not checked. Once the ignore count reaches zero,
4647 @value{GDBN} resumes checking the condition.
4649 You could achieve the effect of the ignore count with a condition such
4650 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4651 is decremented each time. @xref{Convenience Vars, ,Convenience
4655 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4658 @node Break Commands
4659 @subsection Breakpoint Command Lists
4661 @cindex breakpoint commands
4662 You can give any breakpoint (or watchpoint or catchpoint) a series of
4663 commands to execute when your program stops due to that breakpoint. For
4664 example, you might want to print the values of certain expressions, or
4665 enable other breakpoints.
4669 @kindex end@r{ (breakpoint commands)}
4670 @item commands @r{[}@var{range}@dots{}@r{]}
4671 @itemx @dots{} @var{command-list} @dots{}
4673 Specify a list of commands for the given breakpoints. The commands
4674 themselves appear on the following lines. Type a line containing just
4675 @code{end} to terminate the commands.
4677 To remove all commands from a breakpoint, type @code{commands} and
4678 follow it immediately with @code{end}; that is, give no commands.
4680 With no argument, @code{commands} refers to the last breakpoint,
4681 watchpoint, or catchpoint set (not to the breakpoint most recently
4682 encountered). If the most recent breakpoints were set with a single
4683 command, then the @code{commands} will apply to all the breakpoints
4684 set by that command. This applies to breakpoints set by
4685 @code{rbreak}, and also applies when a single @code{break} command
4686 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4690 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4691 disabled within a @var{command-list}.
4693 You can use breakpoint commands to start your program up again. Simply
4694 use the @code{continue} command, or @code{step}, or any other command
4695 that resumes execution.
4697 Any other commands in the command list, after a command that resumes
4698 execution, are ignored. This is because any time you resume execution
4699 (even with a simple @code{next} or @code{step}), you may encounter
4700 another breakpoint---which could have its own command list, leading to
4701 ambiguities about which list to execute.
4704 If the first command you specify in a command list is @code{silent}, the
4705 usual message about stopping at a breakpoint is not printed. This may
4706 be desirable for breakpoints that are to print a specific message and
4707 then continue. If none of the remaining commands print anything, you
4708 see no sign that the breakpoint was reached. @code{silent} is
4709 meaningful only at the beginning of a breakpoint command list.
4711 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4712 print precisely controlled output, and are often useful in silent
4713 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4715 For example, here is how you could use breakpoint commands to print the
4716 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4722 printf "x is %d\n",x
4727 One application for breakpoint commands is to compensate for one bug so
4728 you can test for another. Put a breakpoint just after the erroneous line
4729 of code, give it a condition to detect the case in which something
4730 erroneous has been done, and give it commands to assign correct values
4731 to any variables that need them. End with the @code{continue} command
4732 so that your program does not stop, and start with the @code{silent}
4733 command so that no output is produced. Here is an example:
4744 @node Dynamic Printf
4745 @subsection Dynamic Printf
4747 @cindex dynamic printf
4749 The dynamic printf command @code{dprintf} combines a breakpoint with
4750 formatted printing of your program's data to give you the effect of
4751 inserting @code{printf} calls into your program on-the-fly, without
4752 having to recompile it.
4754 In its most basic form, the output goes to the GDB console. However,
4755 you can set the variable @code{dprintf-style} for alternate handling.
4756 For instance, you can ask to format the output by calling your
4757 program's @code{printf} function. This has the advantage that the
4758 characters go to the program's output device, so they can recorded in
4759 redirects to files and so forth.
4761 If you are doing remote debugging with a stub or agent, you can also
4762 ask to have the printf handled by the remote agent. In addition to
4763 ensuring that the output goes to the remote program's device along
4764 with any other output the program might produce, you can also ask that
4765 the dprintf remain active even after disconnecting from the remote
4766 target. Using the stub/agent is also more efficient, as it can do
4767 everything without needing to communicate with @value{GDBN}.
4771 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4772 Whenever execution reaches @var{location}, print the values of one or
4773 more @var{expressions} under the control of the string @var{template}.
4774 To print several values, separate them with commas.
4776 @item set dprintf-style @var{style}
4777 Set the dprintf output to be handled in one of several different
4778 styles enumerated below. A change of style affects all existing
4779 dynamic printfs immediately. (If you need individual control over the
4780 print commands, simply define normal breakpoints with
4781 explicitly-supplied command lists.)
4784 @kindex dprintf-style gdb
4785 Handle the output using the @value{GDBN} @code{printf} command.
4788 @kindex dprintf-style call
4789 Handle the output by calling a function in your program (normally
4793 @kindex dprintf-style agent
4794 Have the remote debugging agent (such as @code{gdbserver}) handle
4795 the output itself. This style is only available for agents that
4796 support running commands on the target.
4798 @item set dprintf-function @var{function}
4799 Set the function to call if the dprintf style is @code{call}. By
4800 default its value is @code{printf}. You may set it to any expression.
4801 that @value{GDBN} can evaluate to a function, as per the @code{call}
4804 @item set dprintf-channel @var{channel}
4805 Set a ``channel'' for dprintf. If set to a non-empty value,
4806 @value{GDBN} will evaluate it as an expression and pass the result as
4807 a first argument to the @code{dprintf-function}, in the manner of
4808 @code{fprintf} and similar functions. Otherwise, the dprintf format
4809 string will be the first argument, in the manner of @code{printf}.
4811 As an example, if you wanted @code{dprintf} output to go to a logfile
4812 that is a standard I/O stream assigned to the variable @code{mylog},
4813 you could do the following:
4816 (gdb) set dprintf-style call
4817 (gdb) set dprintf-function fprintf
4818 (gdb) set dprintf-channel mylog
4819 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4820 Dprintf 1 at 0x123456: file main.c, line 25.
4822 1 dprintf keep y 0x00123456 in main at main.c:25
4823 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4828 Note that the @code{info break} displays the dynamic printf commands
4829 as normal breakpoint commands; you can thus easily see the effect of
4830 the variable settings.
4832 @item set disconnected-dprintf on
4833 @itemx set disconnected-dprintf off
4834 @kindex set disconnected-dprintf
4835 Choose whether @code{dprintf} commands should continue to run if
4836 @value{GDBN} has disconnected from the target. This only applies
4837 if the @code{dprintf-style} is @code{agent}.
4839 @item show disconnected-dprintf off
4840 @kindex show disconnected-dprintf
4841 Show the current choice for disconnected @code{dprintf}.
4845 @value{GDBN} does not check the validity of function and channel,
4846 relying on you to supply values that are meaningful for the contexts
4847 in which they are being used. For instance, the function and channel
4848 may be the values of local variables, but if that is the case, then
4849 all enabled dynamic prints must be at locations within the scope of
4850 those locals. If evaluation fails, @value{GDBN} will report an error.
4852 @node Save Breakpoints
4853 @subsection How to save breakpoints to a file
4855 To save breakpoint definitions to a file use the @w{@code{save
4856 breakpoints}} command.
4859 @kindex save breakpoints
4860 @cindex save breakpoints to a file for future sessions
4861 @item save breakpoints [@var{filename}]
4862 This command saves all current breakpoint definitions together with
4863 their commands and ignore counts, into a file @file{@var{filename}}
4864 suitable for use in a later debugging session. This includes all
4865 types of breakpoints (breakpoints, watchpoints, catchpoints,
4866 tracepoints). To read the saved breakpoint definitions, use the
4867 @code{source} command (@pxref{Command Files}). Note that watchpoints
4868 with expressions involving local variables may fail to be recreated
4869 because it may not be possible to access the context where the
4870 watchpoint is valid anymore. Because the saved breakpoint definitions
4871 are simply a sequence of @value{GDBN} commands that recreate the
4872 breakpoints, you can edit the file in your favorite editing program,
4873 and remove the breakpoint definitions you're not interested in, or
4874 that can no longer be recreated.
4877 @node Static Probe Points
4878 @subsection Static Probe Points
4880 @cindex static probe point, SystemTap
4881 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4882 for Statically Defined Tracing, and the probes are designed to have a tiny
4883 runtime code and data footprint, and no dynamic relocations. They are
4884 usable from assembly, C and C@t{++} languages. See
4885 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4886 for a good reference on how the @acronym{SDT} probes are implemented.
4888 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4889 @acronym{SDT} probes are supported on ELF-compatible systems. See
4890 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4891 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4892 in your applications.
4894 @cindex semaphores on static probe points
4895 Some probes have an associated semaphore variable; for instance, this
4896 happens automatically if you defined your probe using a DTrace-style
4897 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4898 automatically enable it when you specify a breakpoint using the
4899 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4900 location by some other method (e.g., @code{break file:line}), then
4901 @value{GDBN} will not automatically set the semaphore.
4903 You can examine the available static static probes using @code{info
4904 probes}, with optional arguments:
4908 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4909 If given, @var{provider} is a regular expression used to match against provider
4910 names when selecting which probes to list. If omitted, probes by all
4911 probes from all providers are listed.
4913 If given, @var{name} is a regular expression to match against probe names
4914 when selecting which probes to list. If omitted, probe names are not
4915 considered when deciding whether to display them.
4917 If given, @var{objfile} is a regular expression used to select which
4918 object files (executable or shared libraries) to examine. If not
4919 given, all object files are considered.
4921 @item info probes all
4922 List the available static probes, from all types.
4925 @vindex $_probe_arg@r{, convenience variable}
4926 A probe may specify up to twelve arguments. These are available at the
4927 point at which the probe is defined---that is, when the current PC is
4928 at the probe's location. The arguments are available using the
4929 convenience variables (@pxref{Convenience Vars})
4930 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4931 an integer of the appropriate size; types are not preserved. The
4932 convenience variable @code{$_probe_argc} holds the number of arguments
4933 at the current probe point.
4935 These variables are always available, but attempts to access them at
4936 any location other than a probe point will cause @value{GDBN} to give
4940 @c @ifclear BARETARGET
4941 @node Error in Breakpoints
4942 @subsection ``Cannot insert breakpoints''
4944 If you request too many active hardware-assisted breakpoints and
4945 watchpoints, you will see this error message:
4947 @c FIXME: the precise wording of this message may change; the relevant
4948 @c source change is not committed yet (Sep 3, 1999).
4950 Stopped; cannot insert breakpoints.
4951 You may have requested too many hardware breakpoints and watchpoints.
4955 This message is printed when you attempt to resume the program, since
4956 only then @value{GDBN} knows exactly how many hardware breakpoints and
4957 watchpoints it needs to insert.
4959 When this message is printed, you need to disable or remove some of the
4960 hardware-assisted breakpoints and watchpoints, and then continue.
4962 @node Breakpoint-related Warnings
4963 @subsection ``Breakpoint address adjusted...''
4964 @cindex breakpoint address adjusted
4966 Some processor architectures place constraints on the addresses at
4967 which breakpoints may be placed. For architectures thus constrained,
4968 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4969 with the constraints dictated by the architecture.
4971 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4972 a VLIW architecture in which a number of RISC-like instructions may be
4973 bundled together for parallel execution. The FR-V architecture
4974 constrains the location of a breakpoint instruction within such a
4975 bundle to the instruction with the lowest address. @value{GDBN}
4976 honors this constraint by adjusting a breakpoint's address to the
4977 first in the bundle.
4979 It is not uncommon for optimized code to have bundles which contain
4980 instructions from different source statements, thus it may happen that
4981 a breakpoint's address will be adjusted from one source statement to
4982 another. Since this adjustment may significantly alter @value{GDBN}'s
4983 breakpoint related behavior from what the user expects, a warning is
4984 printed when the breakpoint is first set and also when the breakpoint
4987 A warning like the one below is printed when setting a breakpoint
4988 that's been subject to address adjustment:
4991 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4994 Such warnings are printed both for user settable and @value{GDBN}'s
4995 internal breakpoints. If you see one of these warnings, you should
4996 verify that a breakpoint set at the adjusted address will have the
4997 desired affect. If not, the breakpoint in question may be removed and
4998 other breakpoints may be set which will have the desired behavior.
4999 E.g., it may be sufficient to place the breakpoint at a later
5000 instruction. A conditional breakpoint may also be useful in some
5001 cases to prevent the breakpoint from triggering too often.
5003 @value{GDBN} will also issue a warning when stopping at one of these
5004 adjusted breakpoints:
5007 warning: Breakpoint 1 address previously adjusted from 0x00010414
5011 When this warning is encountered, it may be too late to take remedial
5012 action except in cases where the breakpoint is hit earlier or more
5013 frequently than expected.
5015 @node Continuing and Stepping
5016 @section Continuing and Stepping
5020 @cindex resuming execution
5021 @dfn{Continuing} means resuming program execution until your program
5022 completes normally. In contrast, @dfn{stepping} means executing just
5023 one more ``step'' of your program, where ``step'' may mean either one
5024 line of source code, or one machine instruction (depending on what
5025 particular command you use). Either when continuing or when stepping,
5026 your program may stop even sooner, due to a breakpoint or a signal. (If
5027 it stops due to a signal, you may want to use @code{handle}, or use
5028 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5032 @kindex c @r{(@code{continue})}
5033 @kindex fg @r{(resume foreground execution)}
5034 @item continue @r{[}@var{ignore-count}@r{]}
5035 @itemx c @r{[}@var{ignore-count}@r{]}
5036 @itemx fg @r{[}@var{ignore-count}@r{]}
5037 Resume program execution, at the address where your program last stopped;
5038 any breakpoints set at that address are bypassed. The optional argument
5039 @var{ignore-count} allows you to specify a further number of times to
5040 ignore a breakpoint at this location; its effect is like that of
5041 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5043 The argument @var{ignore-count} is meaningful only when your program
5044 stopped due to a breakpoint. At other times, the argument to
5045 @code{continue} is ignored.
5047 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5048 debugged program is deemed to be the foreground program) are provided
5049 purely for convenience, and have exactly the same behavior as
5053 To resume execution at a different place, you can use @code{return}
5054 (@pxref{Returning, ,Returning from a Function}) to go back to the
5055 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5056 Different Address}) to go to an arbitrary location in your program.
5058 A typical technique for using stepping is to set a breakpoint
5059 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5060 beginning of the function or the section of your program where a problem
5061 is believed to lie, run your program until it stops at that breakpoint,
5062 and then step through the suspect area, examining the variables that are
5063 interesting, until you see the problem happen.
5067 @kindex s @r{(@code{step})}
5069 Continue running your program until control reaches a different source
5070 line, then stop it and return control to @value{GDBN}. This command is
5071 abbreviated @code{s}.
5074 @c "without debugging information" is imprecise; actually "without line
5075 @c numbers in the debugging information". (gcc -g1 has debugging info but
5076 @c not line numbers). But it seems complex to try to make that
5077 @c distinction here.
5078 @emph{Warning:} If you use the @code{step} command while control is
5079 within a function that was compiled without debugging information,
5080 execution proceeds until control reaches a function that does have
5081 debugging information. Likewise, it will not step into a function which
5082 is compiled without debugging information. To step through functions
5083 without debugging information, use the @code{stepi} command, described
5087 The @code{step} command only stops at the first instruction of a source
5088 line. This prevents the multiple stops that could otherwise occur in
5089 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5090 to stop if a function that has debugging information is called within
5091 the line. In other words, @code{step} @emph{steps inside} any functions
5092 called within the line.
5094 Also, the @code{step} command only enters a function if there is line
5095 number information for the function. Otherwise it acts like the
5096 @code{next} command. This avoids problems when using @code{cc -gl}
5097 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5098 was any debugging information about the routine.
5100 @item step @var{count}
5101 Continue running as in @code{step}, but do so @var{count} times. If a
5102 breakpoint is reached, or a signal not related to stepping occurs before
5103 @var{count} steps, stepping stops right away.
5106 @kindex n @r{(@code{next})}
5107 @item next @r{[}@var{count}@r{]}
5108 Continue to the next source line in the current (innermost) stack frame.
5109 This is similar to @code{step}, but function calls that appear within
5110 the line of code are executed without stopping. Execution stops when
5111 control reaches a different line of code at the original stack level
5112 that was executing when you gave the @code{next} command. This command
5113 is abbreviated @code{n}.
5115 An argument @var{count} is a repeat count, as for @code{step}.
5118 @c FIX ME!! Do we delete this, or is there a way it fits in with
5119 @c the following paragraph? --- Vctoria
5121 @c @code{next} within a function that lacks debugging information acts like
5122 @c @code{step}, but any function calls appearing within the code of the
5123 @c function are executed without stopping.
5125 The @code{next} command only stops at the first instruction of a
5126 source line. This prevents multiple stops that could otherwise occur in
5127 @code{switch} statements, @code{for} loops, etc.
5129 @kindex set step-mode
5131 @cindex functions without line info, and stepping
5132 @cindex stepping into functions with no line info
5133 @itemx set step-mode on
5134 The @code{set step-mode on} command causes the @code{step} command to
5135 stop at the first instruction of a function which contains no debug line
5136 information rather than stepping over it.
5138 This is useful in cases where you may be interested in inspecting the
5139 machine instructions of a function which has no symbolic info and do not
5140 want @value{GDBN} to automatically skip over this function.
5142 @item set step-mode off
5143 Causes the @code{step} command to step over any functions which contains no
5144 debug information. This is the default.
5146 @item show step-mode
5147 Show whether @value{GDBN} will stop in or step over functions without
5148 source line debug information.
5151 @kindex fin @r{(@code{finish})}
5153 Continue running until just after function in the selected stack frame
5154 returns. Print the returned value (if any). This command can be
5155 abbreviated as @code{fin}.
5157 Contrast this with the @code{return} command (@pxref{Returning,
5158 ,Returning from a Function}).
5161 @kindex u @r{(@code{until})}
5162 @cindex run until specified location
5165 Continue running until a source line past the current line, in the
5166 current stack frame, is reached. This command is used to avoid single
5167 stepping through a loop more than once. It is like the @code{next}
5168 command, except that when @code{until} encounters a jump, it
5169 automatically continues execution until the program counter is greater
5170 than the address of the jump.
5172 This means that when you reach the end of a loop after single stepping
5173 though it, @code{until} makes your program continue execution until it
5174 exits the loop. In contrast, a @code{next} command at the end of a loop
5175 simply steps back to the beginning of the loop, which forces you to step
5176 through the next iteration.
5178 @code{until} always stops your program if it attempts to exit the current
5181 @code{until} may produce somewhat counterintuitive results if the order
5182 of machine code does not match the order of the source lines. For
5183 example, in the following excerpt from a debugging session, the @code{f}
5184 (@code{frame}) command shows that execution is stopped at line
5185 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5189 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5191 (@value{GDBP}) until
5192 195 for ( ; argc > 0; NEXTARG) @{
5195 This happened because, for execution efficiency, the compiler had
5196 generated code for the loop closure test at the end, rather than the
5197 start, of the loop---even though the test in a C @code{for}-loop is
5198 written before the body of the loop. The @code{until} command appeared
5199 to step back to the beginning of the loop when it advanced to this
5200 expression; however, it has not really gone to an earlier
5201 statement---not in terms of the actual machine code.
5203 @code{until} with no argument works by means of single
5204 instruction stepping, and hence is slower than @code{until} with an
5207 @item until @var{location}
5208 @itemx u @var{location}
5209 Continue running your program until either the specified location is
5210 reached, or the current stack frame returns. @var{location} is any of
5211 the forms described in @ref{Specify Location}.
5212 This form of the command uses temporary breakpoints, and
5213 hence is quicker than @code{until} without an argument. The specified
5214 location is actually reached only if it is in the current frame. This
5215 implies that @code{until} can be used to skip over recursive function
5216 invocations. For instance in the code below, if the current location is
5217 line @code{96}, issuing @code{until 99} will execute the program up to
5218 line @code{99} in the same invocation of factorial, i.e., after the inner
5219 invocations have returned.
5222 94 int factorial (int value)
5224 96 if (value > 1) @{
5225 97 value *= factorial (value - 1);
5232 @kindex advance @var{location}
5233 @item advance @var{location}
5234 Continue running the program up to the given @var{location}. An argument is
5235 required, which should be of one of the forms described in
5236 @ref{Specify Location}.
5237 Execution will also stop upon exit from the current stack
5238 frame. This command is similar to @code{until}, but @code{advance} will
5239 not skip over recursive function calls, and the target location doesn't
5240 have to be in the same frame as the current one.
5244 @kindex si @r{(@code{stepi})}
5246 @itemx stepi @var{arg}
5248 Execute one machine instruction, then stop and return to the debugger.
5250 It is often useful to do @samp{display/i $pc} when stepping by machine
5251 instructions. This makes @value{GDBN} automatically display the next
5252 instruction to be executed, each time your program stops. @xref{Auto
5253 Display,, Automatic Display}.
5255 An argument is a repeat count, as in @code{step}.
5259 @kindex ni @r{(@code{nexti})}
5261 @itemx nexti @var{arg}
5263 Execute one machine instruction, but if it is a function call,
5264 proceed until the function returns.
5266 An argument is a repeat count, as in @code{next}.
5270 @anchor{range stepping}
5271 @cindex range stepping
5272 @cindex target-assisted range stepping
5273 By default, and if available, @value{GDBN} makes use of
5274 target-assisted @dfn{range stepping}. In other words, whenever you
5275 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5276 tells the target to step the corresponding range of instruction
5277 addresses instead of issuing multiple single-steps. This speeds up
5278 line stepping, particularly for remote targets. Ideally, there should
5279 be no reason you would want to turn range stepping off. However, it's
5280 possible that a bug in the debug info, a bug in the remote stub (for
5281 remote targets), or even a bug in @value{GDBN} could make line
5282 stepping behave incorrectly when target-assisted range stepping is
5283 enabled. You can use the following command to turn off range stepping
5287 @kindex set range-stepping
5288 @kindex show range-stepping
5289 @item set range-stepping
5290 @itemx show range-stepping
5291 Control whether range stepping is enabled.
5293 If @code{on}, and the target supports it, @value{GDBN} tells the
5294 target to step a range of addresses itself, instead of issuing
5295 multiple single-steps. If @code{off}, @value{GDBN} always issues
5296 single-steps, even if range stepping is supported by the target. The
5297 default is @code{on}.
5301 @node Skipping Over Functions and Files
5302 @section Skipping Over Functions and Files
5303 @cindex skipping over functions and files
5305 The program you are debugging may contain some functions which are
5306 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5307 skip a function or all functions in a file when stepping.
5309 For example, consider the following C function:
5320 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5321 are not interested in stepping through @code{boring}. If you run @code{step}
5322 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5323 step over both @code{foo} and @code{boring}!
5325 One solution is to @code{step} into @code{boring} and use the @code{finish}
5326 command to immediately exit it. But this can become tedious if @code{boring}
5327 is called from many places.
5329 A more flexible solution is to execute @kbd{skip boring}. This instructs
5330 @value{GDBN} never to step into @code{boring}. Now when you execute
5331 @code{step} at line 103, you'll step over @code{boring} and directly into
5334 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5335 example, @code{skip file boring.c}.
5338 @kindex skip function
5339 @item skip @r{[}@var{linespec}@r{]}
5340 @itemx skip function @r{[}@var{linespec}@r{]}
5341 After running this command, the function named by @var{linespec} or the
5342 function containing the line named by @var{linespec} will be skipped over when
5343 stepping. @xref{Specify Location}.
5345 If you do not specify @var{linespec}, the function you're currently debugging
5348 (If you have a function called @code{file} that you want to skip, use
5349 @kbd{skip function file}.)
5352 @item skip file @r{[}@var{filename}@r{]}
5353 After running this command, any function whose source lives in @var{filename}
5354 will be skipped over when stepping.
5356 If you do not specify @var{filename}, functions whose source lives in the file
5357 you're currently debugging will be skipped.
5360 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5361 These are the commands for managing your list of skips:
5365 @item info skip @r{[}@var{range}@r{]}
5366 Print details about the specified skip(s). If @var{range} is not specified,
5367 print a table with details about all functions and files marked for skipping.
5368 @code{info skip} prints the following information about each skip:
5372 A number identifying this skip.
5374 The type of this skip, either @samp{function} or @samp{file}.
5375 @item Enabled or Disabled
5376 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5378 For function skips, this column indicates the address in memory of the function
5379 being skipped. If you've set a function skip on a function which has not yet
5380 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5381 which has the function is loaded, @code{info skip} will show the function's
5384 For file skips, this field contains the filename being skipped. For functions
5385 skips, this field contains the function name and its line number in the file
5386 where it is defined.
5390 @item skip delete @r{[}@var{range}@r{]}
5391 Delete the specified skip(s). If @var{range} is not specified, delete all
5395 @item skip enable @r{[}@var{range}@r{]}
5396 Enable the specified skip(s). If @var{range} is not specified, enable all
5399 @kindex skip disable
5400 @item skip disable @r{[}@var{range}@r{]}
5401 Disable the specified skip(s). If @var{range} is not specified, disable all
5410 A signal is an asynchronous event that can happen in a program. The
5411 operating system defines the possible kinds of signals, and gives each
5412 kind a name and a number. For example, in Unix @code{SIGINT} is the
5413 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5414 @code{SIGSEGV} is the signal a program gets from referencing a place in
5415 memory far away from all the areas in use; @code{SIGALRM} occurs when
5416 the alarm clock timer goes off (which happens only if your program has
5417 requested an alarm).
5419 @cindex fatal signals
5420 Some signals, including @code{SIGALRM}, are a normal part of the
5421 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5422 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5423 program has not specified in advance some other way to handle the signal.
5424 @code{SIGINT} does not indicate an error in your program, but it is normally
5425 fatal so it can carry out the purpose of the interrupt: to kill the program.
5427 @value{GDBN} has the ability to detect any occurrence of a signal in your
5428 program. You can tell @value{GDBN} in advance what to do for each kind of
5431 @cindex handling signals
5432 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5433 @code{SIGALRM} be silently passed to your program
5434 (so as not to interfere with their role in the program's functioning)
5435 but to stop your program immediately whenever an error signal happens.
5436 You can change these settings with the @code{handle} command.
5439 @kindex info signals
5443 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5444 handle each one. You can use this to see the signal numbers of all
5445 the defined types of signals.
5447 @item info signals @var{sig}
5448 Similar, but print information only about the specified signal number.
5450 @code{info handle} is an alias for @code{info signals}.
5452 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5453 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5454 for details about this command.
5457 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5458 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5459 can be the number of a signal or its name (with or without the
5460 @samp{SIG} at the beginning); a list of signal numbers of the form
5461 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5462 known signals. Optional arguments @var{keywords}, described below,
5463 say what change to make.
5467 The keywords allowed by the @code{handle} command can be abbreviated.
5468 Their full names are:
5472 @value{GDBN} should not stop your program when this signal happens. It may
5473 still print a message telling you that the signal has come in.
5476 @value{GDBN} should stop your program when this signal happens. This implies
5477 the @code{print} keyword as well.
5480 @value{GDBN} should print a message when this signal happens.
5483 @value{GDBN} should not mention the occurrence of the signal at all. This
5484 implies the @code{nostop} keyword as well.
5488 @value{GDBN} should allow your program to see this signal; your program
5489 can handle the signal, or else it may terminate if the signal is fatal
5490 and not handled. @code{pass} and @code{noignore} are synonyms.
5494 @value{GDBN} should not allow your program to see this signal.
5495 @code{nopass} and @code{ignore} are synonyms.
5499 When a signal stops your program, the signal is not visible to the
5501 continue. Your program sees the signal then, if @code{pass} is in
5502 effect for the signal in question @emph{at that time}. In other words,
5503 after @value{GDBN} reports a signal, you can use the @code{handle}
5504 command with @code{pass} or @code{nopass} to control whether your
5505 program sees that signal when you continue.
5507 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5508 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5509 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5512 You can also use the @code{signal} command to prevent your program from
5513 seeing a signal, or cause it to see a signal it normally would not see,
5514 or to give it any signal at any time. For example, if your program stopped
5515 due to some sort of memory reference error, you might store correct
5516 values into the erroneous variables and continue, hoping to see more
5517 execution; but your program would probably terminate immediately as
5518 a result of the fatal signal once it saw the signal. To prevent this,
5519 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5522 @cindex extra signal information
5523 @anchor{extra signal information}
5525 On some targets, @value{GDBN} can inspect extra signal information
5526 associated with the intercepted signal, before it is actually
5527 delivered to the program being debugged. This information is exported
5528 by the convenience variable @code{$_siginfo}, and consists of data
5529 that is passed by the kernel to the signal handler at the time of the
5530 receipt of a signal. The data type of the information itself is
5531 target dependent. You can see the data type using the @code{ptype
5532 $_siginfo} command. On Unix systems, it typically corresponds to the
5533 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5536 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5537 referenced address that raised a segmentation fault.
5541 (@value{GDBP}) continue
5542 Program received signal SIGSEGV, Segmentation fault.
5543 0x0000000000400766 in main ()
5545 (@value{GDBP}) ptype $_siginfo
5552 struct @{...@} _kill;
5553 struct @{...@} _timer;
5555 struct @{...@} _sigchld;
5556 struct @{...@} _sigfault;
5557 struct @{...@} _sigpoll;
5560 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5564 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5565 $1 = (void *) 0x7ffff7ff7000
5569 Depending on target support, @code{$_siginfo} may also be writable.
5572 @section Stopping and Starting Multi-thread Programs
5574 @cindex stopped threads
5575 @cindex threads, stopped
5577 @cindex continuing threads
5578 @cindex threads, continuing
5580 @value{GDBN} supports debugging programs with multiple threads
5581 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5582 are two modes of controlling execution of your program within the
5583 debugger. In the default mode, referred to as @dfn{all-stop mode},
5584 when any thread in your program stops (for example, at a breakpoint
5585 or while being stepped), all other threads in the program are also stopped by
5586 @value{GDBN}. On some targets, @value{GDBN} also supports
5587 @dfn{non-stop mode}, in which other threads can continue to run freely while
5588 you examine the stopped thread in the debugger.
5591 * All-Stop Mode:: All threads stop when GDB takes control
5592 * Non-Stop Mode:: Other threads continue to execute
5593 * Background Execution:: Running your program asynchronously
5594 * Thread-Specific Breakpoints:: Controlling breakpoints
5595 * Interrupted System Calls:: GDB may interfere with system calls
5596 * Observer Mode:: GDB does not alter program behavior
5600 @subsection All-Stop Mode
5602 @cindex all-stop mode
5604 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5605 @emph{all} threads of execution stop, not just the current thread. This
5606 allows you to examine the overall state of the program, including
5607 switching between threads, without worrying that things may change
5610 Conversely, whenever you restart the program, @emph{all} threads start
5611 executing. @emph{This is true even when single-stepping} with commands
5612 like @code{step} or @code{next}.
5614 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5615 Since thread scheduling is up to your debugging target's operating
5616 system (not controlled by @value{GDBN}), other threads may
5617 execute more than one statement while the current thread completes a
5618 single step. Moreover, in general other threads stop in the middle of a
5619 statement, rather than at a clean statement boundary, when the program
5622 You might even find your program stopped in another thread after
5623 continuing or even single-stepping. This happens whenever some other
5624 thread runs into a breakpoint, a signal, or an exception before the
5625 first thread completes whatever you requested.
5627 @cindex automatic thread selection
5628 @cindex switching threads automatically
5629 @cindex threads, automatic switching
5630 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5631 signal, it automatically selects the thread where that breakpoint or
5632 signal happened. @value{GDBN} alerts you to the context switch with a
5633 message such as @samp{[Switching to Thread @var{n}]} to identify the
5636 On some OSes, you can modify @value{GDBN}'s default behavior by
5637 locking the OS scheduler to allow only a single thread to run.
5640 @item set scheduler-locking @var{mode}
5641 @cindex scheduler locking mode
5642 @cindex lock scheduler
5643 Set the scheduler locking mode. If it is @code{off}, then there is no
5644 locking and any thread may run at any time. If @code{on}, then only the
5645 current thread may run when the inferior is resumed. The @code{step}
5646 mode optimizes for single-stepping; it prevents other threads
5647 from preempting the current thread while you are stepping, so that
5648 the focus of debugging does not change unexpectedly.
5649 Other threads only rarely (or never) get a chance to run
5650 when you step. They are more likely to run when you @samp{next} over a
5651 function call, and they are completely free to run when you use commands
5652 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5653 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5654 the current thread away from the thread that you are debugging.
5656 @item show scheduler-locking
5657 Display the current scheduler locking mode.
5660 @cindex resume threads of multiple processes simultaneously
5661 By default, when you issue one of the execution commands such as
5662 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5663 threads of the current inferior to run. For example, if @value{GDBN}
5664 is attached to two inferiors, each with two threads, the
5665 @code{continue} command resumes only the two threads of the current
5666 inferior. This is useful, for example, when you debug a program that
5667 forks and you want to hold the parent stopped (so that, for instance,
5668 it doesn't run to exit), while you debug the child. In other
5669 situations, you may not be interested in inspecting the current state
5670 of any of the processes @value{GDBN} is attached to, and you may want
5671 to resume them all until some breakpoint is hit. In the latter case,
5672 you can instruct @value{GDBN} to allow all threads of all the
5673 inferiors to run with the @w{@code{set schedule-multiple}} command.
5676 @kindex set schedule-multiple
5677 @item set schedule-multiple
5678 Set the mode for allowing threads of multiple processes to be resumed
5679 when an execution command is issued. When @code{on}, all threads of
5680 all processes are allowed to run. When @code{off}, only the threads
5681 of the current process are resumed. The default is @code{off}. The
5682 @code{scheduler-locking} mode takes precedence when set to @code{on},
5683 or while you are stepping and set to @code{step}.
5685 @item show schedule-multiple
5686 Display the current mode for resuming the execution of threads of
5691 @subsection Non-Stop Mode
5693 @cindex non-stop mode
5695 @c This section is really only a place-holder, and needs to be expanded
5696 @c with more details.
5698 For some multi-threaded targets, @value{GDBN} supports an optional
5699 mode of operation in which you can examine stopped program threads in
5700 the debugger while other threads continue to execute freely. This
5701 minimizes intrusion when debugging live systems, such as programs
5702 where some threads have real-time constraints or must continue to
5703 respond to external events. This is referred to as @dfn{non-stop} mode.
5705 In non-stop mode, when a thread stops to report a debugging event,
5706 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5707 threads as well, in contrast to the all-stop mode behavior. Additionally,
5708 execution commands such as @code{continue} and @code{step} apply by default
5709 only to the current thread in non-stop mode, rather than all threads as
5710 in all-stop mode. This allows you to control threads explicitly in
5711 ways that are not possible in all-stop mode --- for example, stepping
5712 one thread while allowing others to run freely, stepping
5713 one thread while holding all others stopped, or stepping several threads
5714 independently and simultaneously.
5716 To enter non-stop mode, use this sequence of commands before you run
5717 or attach to your program:
5720 # Enable the async interface.
5723 # If using the CLI, pagination breaks non-stop.
5726 # Finally, turn it on!
5730 You can use these commands to manipulate the non-stop mode setting:
5733 @kindex set non-stop
5734 @item set non-stop on
5735 Enable selection of non-stop mode.
5736 @item set non-stop off
5737 Disable selection of non-stop mode.
5738 @kindex show non-stop
5740 Show the current non-stop enablement setting.
5743 Note these commands only reflect whether non-stop mode is enabled,
5744 not whether the currently-executing program is being run in non-stop mode.
5745 In particular, the @code{set non-stop} preference is only consulted when
5746 @value{GDBN} starts or connects to the target program, and it is generally
5747 not possible to switch modes once debugging has started. Furthermore,
5748 since not all targets support non-stop mode, even when you have enabled
5749 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5752 In non-stop mode, all execution commands apply only to the current thread
5753 by default. That is, @code{continue} only continues one thread.
5754 To continue all threads, issue @code{continue -a} or @code{c -a}.
5756 You can use @value{GDBN}'s background execution commands
5757 (@pxref{Background Execution}) to run some threads in the background
5758 while you continue to examine or step others from @value{GDBN}.
5759 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5760 always executed asynchronously in non-stop mode.
5762 Suspending execution is done with the @code{interrupt} command when
5763 running in the background, or @kbd{Ctrl-c} during foreground execution.
5764 In all-stop mode, this stops the whole process;
5765 but in non-stop mode the interrupt applies only to the current thread.
5766 To stop the whole program, use @code{interrupt -a}.
5768 Other execution commands do not currently support the @code{-a} option.
5770 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5771 that thread current, as it does in all-stop mode. This is because the
5772 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5773 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5774 changed to a different thread just as you entered a command to operate on the
5775 previously current thread.
5777 @node Background Execution
5778 @subsection Background Execution
5780 @cindex foreground execution
5781 @cindex background execution
5782 @cindex asynchronous execution
5783 @cindex execution, foreground, background and asynchronous
5785 @value{GDBN}'s execution commands have two variants: the normal
5786 foreground (synchronous) behavior, and a background
5787 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5788 the program to report that some thread has stopped before prompting for
5789 another command. In background execution, @value{GDBN} immediately gives
5790 a command prompt so that you can issue other commands while your program runs.
5792 You need to explicitly enable asynchronous mode before you can use
5793 background execution commands. You can use these commands to
5794 manipulate the asynchronous mode setting:
5797 @kindex set target-async
5798 @item set target-async on
5799 Enable asynchronous mode.
5800 @item set target-async off
5801 Disable asynchronous mode.
5802 @kindex show target-async
5803 @item show target-async
5804 Show the current target-async setting.
5807 If the target doesn't support async mode, @value{GDBN} issues an error
5808 message if you attempt to use the background execution commands.
5810 To specify background execution, add a @code{&} to the command. For example,
5811 the background form of the @code{continue} command is @code{continue&}, or
5812 just @code{c&}. The execution commands that accept background execution
5818 @xref{Starting, , Starting your Program}.
5822 @xref{Attach, , Debugging an Already-running Process}.
5826 @xref{Continuing and Stepping, step}.
5830 @xref{Continuing and Stepping, stepi}.
5834 @xref{Continuing and Stepping, next}.
5838 @xref{Continuing and Stepping, nexti}.
5842 @xref{Continuing and Stepping, continue}.
5846 @xref{Continuing and Stepping, finish}.
5850 @xref{Continuing and Stepping, until}.
5854 Background execution is especially useful in conjunction with non-stop
5855 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5856 However, you can also use these commands in the normal all-stop mode with
5857 the restriction that you cannot issue another execution command until the
5858 previous one finishes. Examples of commands that are valid in all-stop
5859 mode while the program is running include @code{help} and @code{info break}.
5861 You can interrupt your program while it is running in the background by
5862 using the @code{interrupt} command.
5869 Suspend execution of the running program. In all-stop mode,
5870 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5871 only the current thread. To stop the whole program in non-stop mode,
5872 use @code{interrupt -a}.
5875 @node Thread-Specific Breakpoints
5876 @subsection Thread-Specific Breakpoints
5878 When your program has multiple threads (@pxref{Threads,, Debugging
5879 Programs with Multiple Threads}), you can choose whether to set
5880 breakpoints on all threads, or on a particular thread.
5883 @cindex breakpoints and threads
5884 @cindex thread breakpoints
5885 @kindex break @dots{} thread @var{threadno}
5886 @item break @var{linespec} thread @var{threadno}
5887 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5888 @var{linespec} specifies source lines; there are several ways of
5889 writing them (@pxref{Specify Location}), but the effect is always to
5890 specify some source line.
5892 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5893 to specify that you only want @value{GDBN} to stop the program when a
5894 particular thread reaches this breakpoint. @var{threadno} is one of the
5895 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5896 column of the @samp{info threads} display.
5898 If you do not specify @samp{thread @var{threadno}} when you set a
5899 breakpoint, the breakpoint applies to @emph{all} threads of your
5902 You can use the @code{thread} qualifier on conditional breakpoints as
5903 well; in this case, place @samp{thread @var{threadno}} before or
5904 after the breakpoint condition, like this:
5907 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5912 Thread-specific breakpoints are automatically deleted when
5913 @value{GDBN} detects the corresponding thread is no longer in the
5914 thread list. For example:
5918 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5921 There are several ways for a thread to disappear, such as a regular
5922 thread exit, but also when you detach from the process with the
5923 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5924 Process}), or if @value{GDBN} loses the remote connection
5925 (@pxref{Remote Debugging}), etc. Note that with some targets,
5926 @value{GDBN} is only able to detect a thread has exited when the user
5927 explictly asks for the thread list with the @code{info threads}
5930 @node Interrupted System Calls
5931 @subsection Interrupted System Calls
5933 @cindex thread breakpoints and system calls
5934 @cindex system calls and thread breakpoints
5935 @cindex premature return from system calls
5936 There is an unfortunate side effect when using @value{GDBN} to debug
5937 multi-threaded programs. If one thread stops for a
5938 breakpoint, or for some other reason, and another thread is blocked in a
5939 system call, then the system call may return prematurely. This is a
5940 consequence of the interaction between multiple threads and the signals
5941 that @value{GDBN} uses to implement breakpoints and other events that
5944 To handle this problem, your program should check the return value of
5945 each system call and react appropriately. This is good programming
5948 For example, do not write code like this:
5954 The call to @code{sleep} will return early if a different thread stops
5955 at a breakpoint or for some other reason.
5957 Instead, write this:
5962 unslept = sleep (unslept);
5965 A system call is allowed to return early, so the system is still
5966 conforming to its specification. But @value{GDBN} does cause your
5967 multi-threaded program to behave differently than it would without
5970 Also, @value{GDBN} uses internal breakpoints in the thread library to
5971 monitor certain events such as thread creation and thread destruction.
5972 When such an event happens, a system call in another thread may return
5973 prematurely, even though your program does not appear to stop.
5976 @subsection Observer Mode
5978 If you want to build on non-stop mode and observe program behavior
5979 without any chance of disruption by @value{GDBN}, you can set
5980 variables to disable all of the debugger's attempts to modify state,
5981 whether by writing memory, inserting breakpoints, etc. These operate
5982 at a low level, intercepting operations from all commands.
5984 When all of these are set to @code{off}, then @value{GDBN} is said to
5985 be @dfn{observer mode}. As a convenience, the variable
5986 @code{observer} can be set to disable these, plus enable non-stop
5989 Note that @value{GDBN} will not prevent you from making nonsensical
5990 combinations of these settings. For instance, if you have enabled
5991 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5992 then breakpoints that work by writing trap instructions into the code
5993 stream will still not be able to be placed.
5998 @item set observer on
5999 @itemx set observer off
6000 When set to @code{on}, this disables all the permission variables
6001 below (except for @code{insert-fast-tracepoints}), plus enables
6002 non-stop debugging. Setting this to @code{off} switches back to
6003 normal debugging, though remaining in non-stop mode.
6006 Show whether observer mode is on or off.
6008 @kindex may-write-registers
6009 @item set may-write-registers on
6010 @itemx set may-write-registers off
6011 This controls whether @value{GDBN} will attempt to alter the values of
6012 registers, such as with assignment expressions in @code{print}, or the
6013 @code{jump} command. It defaults to @code{on}.
6015 @item show may-write-registers
6016 Show the current permission to write registers.
6018 @kindex may-write-memory
6019 @item set may-write-memory on
6020 @itemx set may-write-memory off
6021 This controls whether @value{GDBN} will attempt to alter the contents
6022 of memory, such as with assignment expressions in @code{print}. It
6023 defaults to @code{on}.
6025 @item show may-write-memory
6026 Show the current permission to write memory.
6028 @kindex may-insert-breakpoints
6029 @item set may-insert-breakpoints on
6030 @itemx set may-insert-breakpoints off
6031 This controls whether @value{GDBN} will attempt to insert breakpoints.
6032 This affects all breakpoints, including internal breakpoints defined
6033 by @value{GDBN}. It defaults to @code{on}.
6035 @item show may-insert-breakpoints
6036 Show the current permission to insert breakpoints.
6038 @kindex may-insert-tracepoints
6039 @item set may-insert-tracepoints on
6040 @itemx set may-insert-tracepoints off
6041 This controls whether @value{GDBN} will attempt to insert (regular)
6042 tracepoints at the beginning of a tracing experiment. It affects only
6043 non-fast tracepoints, fast tracepoints being under the control of
6044 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6046 @item show may-insert-tracepoints
6047 Show the current permission to insert tracepoints.
6049 @kindex may-insert-fast-tracepoints
6050 @item set may-insert-fast-tracepoints on
6051 @itemx set may-insert-fast-tracepoints off
6052 This controls whether @value{GDBN} will attempt to insert fast
6053 tracepoints at the beginning of a tracing experiment. It affects only
6054 fast tracepoints, regular (non-fast) tracepoints being under the
6055 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6057 @item show may-insert-fast-tracepoints
6058 Show the current permission to insert fast tracepoints.
6060 @kindex may-interrupt
6061 @item set may-interrupt on
6062 @itemx set may-interrupt off
6063 This controls whether @value{GDBN} will attempt to interrupt or stop
6064 program execution. When this variable is @code{off}, the
6065 @code{interrupt} command will have no effect, nor will
6066 @kbd{Ctrl-c}. It defaults to @code{on}.
6068 @item show may-interrupt
6069 Show the current permission to interrupt or stop the program.
6073 @node Reverse Execution
6074 @chapter Running programs backward
6075 @cindex reverse execution
6076 @cindex running programs backward
6078 When you are debugging a program, it is not unusual to realize that
6079 you have gone too far, and some event of interest has already happened.
6080 If the target environment supports it, @value{GDBN} can allow you to
6081 ``rewind'' the program by running it backward.
6083 A target environment that supports reverse execution should be able
6084 to ``undo'' the changes in machine state that have taken place as the
6085 program was executing normally. Variables, registers etc.@: should
6086 revert to their previous values. Obviously this requires a great
6087 deal of sophistication on the part of the target environment; not
6088 all target environments can support reverse execution.
6090 When a program is executed in reverse, the instructions that
6091 have most recently been executed are ``un-executed'', in reverse
6092 order. The program counter runs backward, following the previous
6093 thread of execution in reverse. As each instruction is ``un-executed'',
6094 the values of memory and/or registers that were changed by that
6095 instruction are reverted to their previous states. After executing
6096 a piece of source code in reverse, all side effects of that code
6097 should be ``undone'', and all variables should be returned to their
6098 prior values@footnote{
6099 Note that some side effects are easier to undo than others. For instance,
6100 memory and registers are relatively easy, but device I/O is hard. Some
6101 targets may be able undo things like device I/O, and some may not.
6103 The contract between @value{GDBN} and the reverse executing target
6104 requires only that the target do something reasonable when
6105 @value{GDBN} tells it to execute backwards, and then report the
6106 results back to @value{GDBN}. Whatever the target reports back to
6107 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6108 assumes that the memory and registers that the target reports are in a
6109 consistant state, but @value{GDBN} accepts whatever it is given.
6112 If you are debugging in a target environment that supports
6113 reverse execution, @value{GDBN} provides the following commands.
6116 @kindex reverse-continue
6117 @kindex rc @r{(@code{reverse-continue})}
6118 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6119 @itemx rc @r{[}@var{ignore-count}@r{]}
6120 Beginning at the point where your program last stopped, start executing
6121 in reverse. Reverse execution will stop for breakpoints and synchronous
6122 exceptions (signals), just like normal execution. Behavior of
6123 asynchronous signals depends on the target environment.
6125 @kindex reverse-step
6126 @kindex rs @r{(@code{step})}
6127 @item reverse-step @r{[}@var{count}@r{]}
6128 Run the program backward until control reaches the start of a
6129 different source line; then stop it, and return control to @value{GDBN}.
6131 Like the @code{step} command, @code{reverse-step} will only stop
6132 at the beginning of a source line. It ``un-executes'' the previously
6133 executed source line. If the previous source line included calls to
6134 debuggable functions, @code{reverse-step} will step (backward) into
6135 the called function, stopping at the beginning of the @emph{last}
6136 statement in the called function (typically a return statement).
6138 Also, as with the @code{step} command, if non-debuggable functions are
6139 called, @code{reverse-step} will run thru them backward without stopping.
6141 @kindex reverse-stepi
6142 @kindex rsi @r{(@code{reverse-stepi})}
6143 @item reverse-stepi @r{[}@var{count}@r{]}
6144 Reverse-execute one machine instruction. Note that the instruction
6145 to be reverse-executed is @emph{not} the one pointed to by the program
6146 counter, but the instruction executed prior to that one. For instance,
6147 if the last instruction was a jump, @code{reverse-stepi} will take you
6148 back from the destination of the jump to the jump instruction itself.
6150 @kindex reverse-next
6151 @kindex rn @r{(@code{reverse-next})}
6152 @item reverse-next @r{[}@var{count}@r{]}
6153 Run backward to the beginning of the previous line executed in
6154 the current (innermost) stack frame. If the line contains function
6155 calls, they will be ``un-executed'' without stopping. Starting from
6156 the first line of a function, @code{reverse-next} will take you back
6157 to the caller of that function, @emph{before} the function was called,
6158 just as the normal @code{next} command would take you from the last
6159 line of a function back to its return to its caller
6160 @footnote{Unless the code is too heavily optimized.}.
6162 @kindex reverse-nexti
6163 @kindex rni @r{(@code{reverse-nexti})}
6164 @item reverse-nexti @r{[}@var{count}@r{]}
6165 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6166 in reverse, except that called functions are ``un-executed'' atomically.
6167 That is, if the previously executed instruction was a return from
6168 another function, @code{reverse-nexti} will continue to execute
6169 in reverse until the call to that function (from the current stack
6172 @kindex reverse-finish
6173 @item reverse-finish
6174 Just as the @code{finish} command takes you to the point where the
6175 current function returns, @code{reverse-finish} takes you to the point
6176 where it was called. Instead of ending up at the end of the current
6177 function invocation, you end up at the beginning.
6179 @kindex set exec-direction
6180 @item set exec-direction
6181 Set the direction of target execution.
6182 @item set exec-direction reverse
6183 @cindex execute forward or backward in time
6184 @value{GDBN} will perform all execution commands in reverse, until the
6185 exec-direction mode is changed to ``forward''. Affected commands include
6186 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6187 command cannot be used in reverse mode.
6188 @item set exec-direction forward
6189 @value{GDBN} will perform all execution commands in the normal fashion.
6190 This is the default.
6194 @node Process Record and Replay
6195 @chapter Recording Inferior's Execution and Replaying It
6196 @cindex process record and replay
6197 @cindex recording inferior's execution and replaying it
6199 On some platforms, @value{GDBN} provides a special @dfn{process record
6200 and replay} target that can record a log of the process execution, and
6201 replay it later with both forward and reverse execution commands.
6204 When this target is in use, if the execution log includes the record
6205 for the next instruction, @value{GDBN} will debug in @dfn{replay
6206 mode}. In the replay mode, the inferior does not really execute code
6207 instructions. Instead, all the events that normally happen during
6208 code execution are taken from the execution log. While code is not
6209 really executed in replay mode, the values of registers (including the
6210 program counter register) and the memory of the inferior are still
6211 changed as they normally would. Their contents are taken from the
6215 If the record for the next instruction is not in the execution log,
6216 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6217 inferior executes normally, and @value{GDBN} records the execution log
6220 The process record and replay target supports reverse execution
6221 (@pxref{Reverse Execution}), even if the platform on which the
6222 inferior runs does not. However, the reverse execution is limited in
6223 this case by the range of the instructions recorded in the execution
6224 log. In other words, reverse execution on platforms that don't
6225 support it directly can only be done in the replay mode.
6227 When debugging in the reverse direction, @value{GDBN} will work in
6228 replay mode as long as the execution log includes the record for the
6229 previous instruction; otherwise, it will work in record mode, if the
6230 platform supports reverse execution, or stop if not.
6232 For architecture environments that support process record and replay,
6233 @value{GDBN} provides the following commands:
6236 @kindex target record
6237 @kindex target record-full
6238 @kindex target record-btrace
6241 @kindex record btrace
6245 @item record @var{method}
6246 This command starts the process record and replay target. The
6247 recording method can be specified as parameter. Without a parameter
6248 the command uses the @code{full} recording method. The following
6249 recording methods are available:
6253 Full record/replay recording using @value{GDBN}'s software record and
6254 replay implementation. This method allows replaying and reverse
6258 Hardware-supported instruction recording. This method does not allow
6259 replaying and reverse execution.
6261 This recording method may not be available on all processors.
6264 The process record and replay target can only debug a process that is
6265 already running. Therefore, you need first to start the process with
6266 the @kbd{run} or @kbd{start} commands, and then start the recording
6267 with the @kbd{record @var{method}} command.
6269 Both @code{record @var{method}} and @code{rec @var{method}} are
6270 aliases of @code{target record-@var{method}}.
6272 @cindex displaced stepping, and process record and replay
6273 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6274 will be automatically disabled when process record and replay target
6275 is started. That's because the process record and replay target
6276 doesn't support displaced stepping.
6278 @cindex non-stop mode, and process record and replay
6279 @cindex asynchronous execution, and process record and replay
6280 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6281 the asynchronous execution mode (@pxref{Background Execution}), not
6282 all recording methods are available. The @code{full} recording method
6283 does not support these two modes.
6288 Stop the process record and replay target. When process record and
6289 replay target stops, the entire execution log will be deleted and the
6290 inferior will either be terminated, or will remain in its final state.
6292 When you stop the process record and replay target in record mode (at
6293 the end of the execution log), the inferior will be stopped at the
6294 next instruction that would have been recorded. In other words, if
6295 you record for a while and then stop recording, the inferior process
6296 will be left in the same state as if the recording never happened.
6298 On the other hand, if the process record and replay target is stopped
6299 while in replay mode (that is, not at the end of the execution log,
6300 but at some earlier point), the inferior process will become ``live''
6301 at that earlier state, and it will then be possible to continue the
6302 usual ``live'' debugging of the process from that state.
6304 When the inferior process exits, or @value{GDBN} detaches from it,
6305 process record and replay target will automatically stop itself.
6309 Go to a specific location in the execution log. There are several
6310 ways to specify the location to go to:
6313 @item record goto begin
6314 @itemx record goto start
6315 Go to the beginning of the execution log.
6317 @item record goto end
6318 Go to the end of the execution log.
6320 @item record goto @var{n}
6321 Go to instruction number @var{n} in the execution log.
6325 @item record save @var{filename}
6326 Save the execution log to a file @file{@var{filename}}.
6327 Default filename is @file{gdb_record.@var{process_id}}, where
6328 @var{process_id} is the process ID of the inferior.
6330 This command may not be available for all recording methods.
6332 @kindex record restore
6333 @item record restore @var{filename}
6334 Restore the execution log from a file @file{@var{filename}}.
6335 File must have been created with @code{record save}.
6337 @kindex set record full
6338 @item set record full insn-number-max @var{limit}
6339 @itemx set record full insn-number-max unlimited
6340 Set the limit of instructions to be recorded for the @code{full}
6341 recording method. Default value is 200000.
6343 If @var{limit} is a positive number, then @value{GDBN} will start
6344 deleting instructions from the log once the number of the record
6345 instructions becomes greater than @var{limit}. For every new recorded
6346 instruction, @value{GDBN} will delete the earliest recorded
6347 instruction to keep the number of recorded instructions at the limit.
6348 (Since deleting recorded instructions loses information, @value{GDBN}
6349 lets you control what happens when the limit is reached, by means of
6350 the @code{stop-at-limit} option, described below.)
6352 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6353 delete recorded instructions from the execution log. The number of
6354 recorded instructions is limited only by the available memory.
6356 @kindex show record full
6357 @item show record full insn-number-max
6358 Show the limit of instructions to be recorded with the @code{full}
6361 @item set record full stop-at-limit
6362 Control the behavior of the @code{full} recording method when the
6363 number of recorded instructions reaches the limit. If ON (the
6364 default), @value{GDBN} will stop when the limit is reached for the
6365 first time and ask you whether you want to stop the inferior or
6366 continue running it and recording the execution log. If you decide
6367 to continue recording, each new recorded instruction will cause the
6368 oldest one to be deleted.
6370 If this option is OFF, @value{GDBN} will automatically delete the
6371 oldest record to make room for each new one, without asking.
6373 @item show record full stop-at-limit
6374 Show the current setting of @code{stop-at-limit}.
6376 @item set record full memory-query
6377 Control the behavior when @value{GDBN} is unable to record memory
6378 changes caused by an instruction for the @code{full} recording method.
6379 If ON, @value{GDBN} will query whether to stop the inferior in that
6382 If this option is OFF (the default), @value{GDBN} will automatically
6383 ignore the effect of such instructions on memory. Later, when
6384 @value{GDBN} replays this execution log, it will mark the log of this
6385 instruction as not accessible, and it will not affect the replay
6388 @item show record full memory-query
6389 Show the current setting of @code{memory-query}.
6393 Show various statistics about the recording depending on the recording
6398 For the @code{full} recording method, it shows the state of process
6399 record and its in-memory execution log buffer, including:
6403 Whether in record mode or replay mode.
6405 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6407 Highest recorded instruction number.
6409 Current instruction about to be replayed (if in replay mode).
6411 Number of instructions contained in the execution log.
6413 Maximum number of instructions that may be contained in the execution log.
6417 For the @code{btrace} recording method, it shows the number of
6418 instructions that have been recorded and the number of blocks of
6419 sequential control-flow that is formed by the recorded instructions.
6422 @kindex record delete
6425 When record target runs in replay mode (``in the past''), delete the
6426 subsequent execution log and begin to record a new execution log starting
6427 from the current address. This means you will abandon the previously
6428 recorded ``future'' and begin recording a new ``future''.
6430 @kindex record instruction-history
6431 @kindex rec instruction-history
6432 @item record instruction-history
6433 Disassembles instructions from the recorded execution log. By
6434 default, ten instructions are disassembled. This can be changed using
6435 the @code{set record instruction-history-size} command. Instructions
6436 are printed in execution order. There are several ways to specify
6437 what part of the execution log to disassemble:
6440 @item record instruction-history @var{insn}
6441 Disassembles ten instructions starting from instruction number
6444 @item record instruction-history @var{insn}, +/-@var{n}
6445 Disassembles @var{n} instructions around instruction number
6446 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6447 @var{n} instructions after instruction number @var{insn}. If
6448 @var{n} is preceded with @code{-}, disassembles @var{n}
6449 instructions before instruction number @var{insn}.
6451 @item record instruction-history
6452 Disassembles ten more instructions after the last disassembly.
6454 @item record instruction-history -
6455 Disassembles ten more instructions before the last disassembly.
6457 @item record instruction-history @var{begin} @var{end}
6458 Disassembles instructions beginning with instruction number
6459 @var{begin} until instruction number @var{end}. The instruction
6460 number @var{end} is not included.
6463 This command may not be available for all recording methods.
6466 @item set record instruction-history-size @var{size}
6467 @itemx set record instruction-history-size unlimited
6468 Define how many instructions to disassemble in the @code{record
6469 instruction-history} command. The default value is 10.
6470 A @var{size} of @code{unlimited} means unlimited instructions.
6473 @item show record instruction-history-size
6474 Show how many instructions to disassemble in the @code{record
6475 instruction-history} command.
6477 @kindex record function-call-history
6478 @kindex rec function-call-history
6479 @item record function-call-history
6480 Prints the execution history at function granularity. It prints one
6481 line for each sequence of instructions that belong to the same
6482 function giving the name of that function, the source lines
6483 for this instruction sequence (if the @code{/l} modifier is
6484 specified), and the instructions numbers that form the sequence (if
6485 the @code{/i} modifier is specified).
6488 (@value{GDBP}) @b{list 1, 10}
6499 (@value{GDBP}) @b{record function-call-history /l}
6505 By default, ten lines are printed. This can be changed using the
6506 @code{set record function-call-history-size} command. Functions are
6507 printed in execution order. There are several ways to specify what
6511 @item record function-call-history @var{func}
6512 Prints ten functions starting from function number @var{func}.
6514 @item record function-call-history @var{func}, +/-@var{n}
6515 Prints @var{n} functions around function number @var{func}. If
6516 @var{n} is preceded with @code{+}, prints @var{n} functions after
6517 function number @var{func}. If @var{n} is preceded with @code{-},
6518 prints @var{n} functions before function number @var{func}.
6520 @item record function-call-history
6521 Prints ten more functions after the last ten-line print.
6523 @item record function-call-history -
6524 Prints ten more functions before the last ten-line print.
6526 @item record function-call-history @var{begin} @var{end}
6527 Prints functions beginning with function number @var{begin} until
6528 function number @var{end}. The function number @var{end} is not
6532 This command may not be available for all recording methods.
6534 @item set record function-call-history-size @var{size}
6535 @itemx set record function-call-history-size unlimited
6536 Define how many lines to print in the
6537 @code{record function-call-history} command. The default value is 10.
6538 A size of @code{unlimited} means unlimited lines.
6540 @item show record function-call-history-size
6541 Show how many lines to print in the
6542 @code{record function-call-history} command.
6547 @chapter Examining the Stack
6549 When your program has stopped, the first thing you need to know is where it
6550 stopped and how it got there.
6553 Each time your program performs a function call, information about the call
6555 That information includes the location of the call in your program,
6556 the arguments of the call,
6557 and the local variables of the function being called.
6558 The information is saved in a block of data called a @dfn{stack frame}.
6559 The stack frames are allocated in a region of memory called the @dfn{call
6562 When your program stops, the @value{GDBN} commands for examining the
6563 stack allow you to see all of this information.
6565 @cindex selected frame
6566 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6567 @value{GDBN} commands refer implicitly to the selected frame. In
6568 particular, whenever you ask @value{GDBN} for the value of a variable in
6569 your program, the value is found in the selected frame. There are
6570 special @value{GDBN} commands to select whichever frame you are
6571 interested in. @xref{Selection, ,Selecting a Frame}.
6573 When your program stops, @value{GDBN} automatically selects the
6574 currently executing frame and describes it briefly, similar to the
6575 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6578 * Frames:: Stack frames
6579 * Backtrace:: Backtraces
6580 * Frame Filter Management:: Managing frame filters
6581 * Selection:: Selecting a frame
6582 * Frame Info:: Information on a frame
6587 @section Stack Frames
6589 @cindex frame, definition
6591 The call stack is divided up into contiguous pieces called @dfn{stack
6592 frames}, or @dfn{frames} for short; each frame is the data associated
6593 with one call to one function. The frame contains the arguments given
6594 to the function, the function's local variables, and the address at
6595 which the function is executing.
6597 @cindex initial frame
6598 @cindex outermost frame
6599 @cindex innermost frame
6600 When your program is started, the stack has only one frame, that of the
6601 function @code{main}. This is called the @dfn{initial} frame or the
6602 @dfn{outermost} frame. Each time a function is called, a new frame is
6603 made. Each time a function returns, the frame for that function invocation
6604 is eliminated. If a function is recursive, there can be many frames for
6605 the same function. The frame for the function in which execution is
6606 actually occurring is called the @dfn{innermost} frame. This is the most
6607 recently created of all the stack frames that still exist.
6609 @cindex frame pointer
6610 Inside your program, stack frames are identified by their addresses. A
6611 stack frame consists of many bytes, each of which has its own address; each
6612 kind of computer has a convention for choosing one byte whose
6613 address serves as the address of the frame. Usually this address is kept
6614 in a register called the @dfn{frame pointer register}
6615 (@pxref{Registers, $fp}) while execution is going on in that frame.
6617 @cindex frame number
6618 @value{GDBN} assigns numbers to all existing stack frames, starting with
6619 zero for the innermost frame, one for the frame that called it,
6620 and so on upward. These numbers do not really exist in your program;
6621 they are assigned by @value{GDBN} to give you a way of designating stack
6622 frames in @value{GDBN} commands.
6624 @c The -fomit-frame-pointer below perennially causes hbox overflow
6625 @c underflow problems.
6626 @cindex frameless execution
6627 Some compilers provide a way to compile functions so that they operate
6628 without stack frames. (For example, the @value{NGCC} option
6630 @samp{-fomit-frame-pointer}
6632 generates functions without a frame.)
6633 This is occasionally done with heavily used library functions to save
6634 the frame setup time. @value{GDBN} has limited facilities for dealing
6635 with these function invocations. If the innermost function invocation
6636 has no stack frame, @value{GDBN} nevertheless regards it as though
6637 it had a separate frame, which is numbered zero as usual, allowing
6638 correct tracing of the function call chain. However, @value{GDBN} has
6639 no provision for frameless functions elsewhere in the stack.
6642 @kindex frame@r{, command}
6643 @cindex current stack frame
6644 @item frame @var{args}
6645 The @code{frame} command allows you to move from one stack frame to another,
6646 and to print the stack frame you select. @var{args} may be either the
6647 address of the frame or the stack frame number. Without an argument,
6648 @code{frame} prints the current stack frame.
6650 @kindex select-frame
6651 @cindex selecting frame silently
6653 The @code{select-frame} command allows you to move from one stack frame
6654 to another without printing the frame. This is the silent version of
6662 @cindex call stack traces
6663 A backtrace is a summary of how your program got where it is. It shows one
6664 line per frame, for many frames, starting with the currently executing
6665 frame (frame zero), followed by its caller (frame one), and on up the
6668 @anchor{backtrace-command}
6671 @kindex bt @r{(@code{backtrace})}
6674 Print a backtrace of the entire stack: one line per frame for all
6675 frames in the stack.
6677 You can stop the backtrace at any time by typing the system interrupt
6678 character, normally @kbd{Ctrl-c}.
6680 @item backtrace @var{n}
6682 Similar, but print only the innermost @var{n} frames.
6684 @item backtrace -@var{n}
6686 Similar, but print only the outermost @var{n} frames.
6688 @item backtrace full
6690 @itemx bt full @var{n}
6691 @itemx bt full -@var{n}
6692 Print the values of the local variables also. @var{n} specifies the
6693 number of frames to print, as described above.
6695 @item backtrace no-filters
6696 @itemx bt no-filters
6697 @itemx bt no-filters @var{n}
6698 @itemx bt no-filters -@var{n}
6699 @itemx bt no-filters full
6700 @itemx bt no-filters full @var{n}
6701 @itemx bt no-filters full -@var{n}
6702 Do not run Python frame filters on this backtrace. @xref{Frame
6703 Filter API}, for more information. Additionally use @ref{disable
6704 frame-filter all} to turn off all frame filters. This is only
6705 relevant when @value{GDBN} has been configured with @code{Python}
6711 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6712 are additional aliases for @code{backtrace}.
6714 @cindex multiple threads, backtrace
6715 In a multi-threaded program, @value{GDBN} by default shows the
6716 backtrace only for the current thread. To display the backtrace for
6717 several or all of the threads, use the command @code{thread apply}
6718 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6719 apply all backtrace}, @value{GDBN} will display the backtrace for all
6720 the threads; this is handy when you debug a core dump of a
6721 multi-threaded program.
6723 Each line in the backtrace shows the frame number and the function name.
6724 The program counter value is also shown---unless you use @code{set
6725 print address off}. The backtrace also shows the source file name and
6726 line number, as well as the arguments to the function. The program
6727 counter value is omitted if it is at the beginning of the code for that
6730 Here is an example of a backtrace. It was made with the command
6731 @samp{bt 3}, so it shows the innermost three frames.
6735 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6737 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6738 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6740 (More stack frames follow...)
6745 The display for frame zero does not begin with a program counter
6746 value, indicating that your program has stopped at the beginning of the
6747 code for line @code{993} of @code{builtin.c}.
6750 The value of parameter @code{data} in frame 1 has been replaced by
6751 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6752 only if it is a scalar (integer, pointer, enumeration, etc). See command
6753 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6754 on how to configure the way function parameter values are printed.
6756 @cindex optimized out, in backtrace
6757 @cindex function call arguments, optimized out
6758 If your program was compiled with optimizations, some compilers will
6759 optimize away arguments passed to functions if those arguments are
6760 never used after the call. Such optimizations generate code that
6761 passes arguments through registers, but doesn't store those arguments
6762 in the stack frame. @value{GDBN} has no way of displaying such
6763 arguments in stack frames other than the innermost one. Here's what
6764 such a backtrace might look like:
6768 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6770 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6771 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6773 (More stack frames follow...)
6778 The values of arguments that were not saved in their stack frames are
6779 shown as @samp{<optimized out>}.
6781 If you need to display the values of such optimized-out arguments,
6782 either deduce that from other variables whose values depend on the one
6783 you are interested in, or recompile without optimizations.
6785 @cindex backtrace beyond @code{main} function
6786 @cindex program entry point
6787 @cindex startup code, and backtrace
6788 Most programs have a standard user entry point---a place where system
6789 libraries and startup code transition into user code. For C this is
6790 @code{main}@footnote{
6791 Note that embedded programs (the so-called ``free-standing''
6792 environment) are not required to have a @code{main} function as the
6793 entry point. They could even have multiple entry points.}.
6794 When @value{GDBN} finds the entry function in a backtrace
6795 it will terminate the backtrace, to avoid tracing into highly
6796 system-specific (and generally uninteresting) code.
6798 If you need to examine the startup code, or limit the number of levels
6799 in a backtrace, you can change this behavior:
6802 @item set backtrace past-main
6803 @itemx set backtrace past-main on
6804 @kindex set backtrace
6805 Backtraces will continue past the user entry point.
6807 @item set backtrace past-main off
6808 Backtraces will stop when they encounter the user entry point. This is the
6811 @item show backtrace past-main
6812 @kindex show backtrace
6813 Display the current user entry point backtrace policy.
6815 @item set backtrace past-entry
6816 @itemx set backtrace past-entry on
6817 Backtraces will continue past the internal entry point of an application.
6818 This entry point is encoded by the linker when the application is built,
6819 and is likely before the user entry point @code{main} (or equivalent) is called.
6821 @item set backtrace past-entry off
6822 Backtraces will stop when they encounter the internal entry point of an
6823 application. This is the default.
6825 @item show backtrace past-entry
6826 Display the current internal entry point backtrace policy.
6828 @item set backtrace limit @var{n}
6829 @itemx set backtrace limit 0
6830 @itemx set backtrace limit unlimited
6831 @cindex backtrace limit
6832 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6833 or zero means unlimited levels.
6835 @item show backtrace limit
6836 Display the current limit on backtrace levels.
6839 You can control how file names are displayed.
6842 @item set filename-display
6843 @itemx set filename-display relative
6844 @cindex filename-display
6845 Display file names relative to the compilation directory. This is the default.
6847 @item set filename-display basename
6848 Display only basename of a filename.
6850 @item set filename-display absolute
6851 Display an absolute filename.
6853 @item show filename-display
6854 Show the current way to display filenames.
6857 @node Frame Filter Management
6858 @section Management of Frame Filters.
6859 @cindex managing frame filters
6861 Frame filters are Python based utilities to manage and decorate the
6862 output of frames. @xref{Frame Filter API}, for further information.
6864 Managing frame filters is performed by several commands available
6865 within @value{GDBN}, detailed here.
6868 @kindex info frame-filter
6869 @item info frame-filter
6870 Print a list of installed frame filters from all dictionaries, showing
6871 their name, priority and enabled status.
6873 @kindex disable frame-filter
6874 @anchor{disable frame-filter all}
6875 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6876 Disable a frame filter in the dictionary matching
6877 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6878 @var{filter-dictionary} may be @code{all}, @code{global},
6879 @code{progspace} or the name of the object file where the frame filter
6880 dictionary resides. When @code{all} is specified, all frame filters
6881 across all dictionaries are disabled. @var{filter-name} is the name
6882 of the frame filter and is used when @code{all} is not the option for
6883 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6884 may be enabled again later.
6886 @kindex enable frame-filter
6887 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6888 Enable a frame filter in the dictionary matching
6889 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6890 @var{filter-dictionary} may be @code{all}, @code{global},
6891 @code{progspace} or the name of the object file where the frame filter
6892 dictionary resides. When @code{all} is specified, all frame filters across
6893 all dictionaries are enabled. @var{filter-name} is the name of the frame
6894 filter and is used when @code{all} is not the option for
6895 @var{filter-dictionary}.
6900 (gdb) info frame-filter
6902 global frame-filters:
6903 Priority Enabled Name
6904 1000 No PrimaryFunctionFilter
6907 progspace /build/test frame-filters:
6908 Priority Enabled Name
6909 100 Yes ProgspaceFilter
6911 objfile /build/test frame-filters:
6912 Priority Enabled Name
6913 999 Yes BuildProgra Filter
6915 (gdb) disable frame-filter /build/test BuildProgramFilter
6916 (gdb) info frame-filter
6918 global frame-filters:
6919 Priority Enabled Name
6920 1000 No PrimaryFunctionFilter
6923 progspace /build/test frame-filters:
6924 Priority Enabled Name
6925 100 Yes ProgspaceFilter
6927 objfile /build/test frame-filters:
6928 Priority Enabled Name
6929 999 No BuildProgramFilter
6931 (gdb) enable frame-filter global PrimaryFunctionFilter
6932 (gdb) info frame-filter
6934 global frame-filters:
6935 Priority Enabled Name
6936 1000 Yes PrimaryFunctionFilter
6939 progspace /build/test frame-filters:
6940 Priority Enabled Name
6941 100 Yes ProgspaceFilter
6943 objfile /build/test frame-filters:
6944 Priority Enabled Name
6945 999 No BuildProgramFilter
6948 @kindex set frame-filter priority
6949 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6950 Set the @var{priority} of a frame filter in the dictionary matching
6951 @var{filter-dictionary}, and the frame filter name matching
6952 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6953 @code{progspace} or the name of the object file where the frame filter
6954 dictionary resides. @var{priority} is an integer.
6956 @kindex show frame-filter priority
6957 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6958 Show the @var{priority} of a frame filter in the dictionary matching
6959 @var{filter-dictionary}, and the frame filter name matching
6960 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6961 @code{progspace} or the name of the object file where the frame filter
6967 (gdb) info frame-filter
6969 global frame-filters:
6970 Priority Enabled Name
6971 1000 Yes PrimaryFunctionFilter
6974 progspace /build/test frame-filters:
6975 Priority Enabled Name
6976 100 Yes ProgspaceFilter
6978 objfile /build/test frame-filters:
6979 Priority Enabled Name
6980 999 No BuildProgramFilter
6982 (gdb) set frame-filter priority global Reverse 50
6983 (gdb) info frame-filter
6985 global frame-filters:
6986 Priority Enabled Name
6987 1000 Yes PrimaryFunctionFilter
6990 progspace /build/test frame-filters:
6991 Priority Enabled Name
6992 100 Yes ProgspaceFilter
6994 objfile /build/test frame-filters:
6995 Priority Enabled Name
6996 999 No BuildProgramFilter
7001 @section Selecting a Frame
7003 Most commands for examining the stack and other data in your program work on
7004 whichever stack frame is selected at the moment. Here are the commands for
7005 selecting a stack frame; all of them finish by printing a brief description
7006 of the stack frame just selected.
7009 @kindex frame@r{, selecting}
7010 @kindex f @r{(@code{frame})}
7013 Select frame number @var{n}. Recall that frame zero is the innermost
7014 (currently executing) frame, frame one is the frame that called the
7015 innermost one, and so on. The highest-numbered frame is the one for
7018 @item frame @var{addr}
7020 Select the frame at address @var{addr}. This is useful mainly if the
7021 chaining of stack frames has been damaged by a bug, making it
7022 impossible for @value{GDBN} to assign numbers properly to all frames. In
7023 addition, this can be useful when your program has multiple stacks and
7024 switches between them.
7026 On the SPARC architecture, @code{frame} needs two addresses to
7027 select an arbitrary frame: a frame pointer and a stack pointer.
7029 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7030 pointer and a program counter.
7032 On the 29k architecture, it needs three addresses: a register stack
7033 pointer, a program counter, and a memory stack pointer.
7037 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7038 advances toward the outermost frame, to higher frame numbers, to frames
7039 that have existed longer. @var{n} defaults to one.
7042 @kindex do @r{(@code{down})}
7044 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7045 advances toward the innermost frame, to lower frame numbers, to frames
7046 that were created more recently. @var{n} defaults to one. You may
7047 abbreviate @code{down} as @code{do}.
7050 All of these commands end by printing two lines of output describing the
7051 frame. The first line shows the frame number, the function name, the
7052 arguments, and the source file and line number of execution in that
7053 frame. The second line shows the text of that source line.
7061 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7063 10 read_input_file (argv[i]);
7067 After such a printout, the @code{list} command with no arguments
7068 prints ten lines centered on the point of execution in the frame.
7069 You can also edit the program at the point of execution with your favorite
7070 editing program by typing @code{edit}.
7071 @xref{List, ,Printing Source Lines},
7075 @kindex down-silently
7077 @item up-silently @var{n}
7078 @itemx down-silently @var{n}
7079 These two commands are variants of @code{up} and @code{down},
7080 respectively; they differ in that they do their work silently, without
7081 causing display of the new frame. They are intended primarily for use
7082 in @value{GDBN} command scripts, where the output might be unnecessary and
7087 @section Information About a Frame
7089 There are several other commands to print information about the selected
7095 When used without any argument, this command does not change which
7096 frame is selected, but prints a brief description of the currently
7097 selected stack frame. It can be abbreviated @code{f}. With an
7098 argument, this command is used to select a stack frame.
7099 @xref{Selection, ,Selecting a Frame}.
7102 @kindex info f @r{(@code{info frame})}
7105 This command prints a verbose description of the selected stack frame,
7110 the address of the frame
7112 the address of the next frame down (called by this frame)
7114 the address of the next frame up (caller of this frame)
7116 the language in which the source code corresponding to this frame is written
7118 the address of the frame's arguments
7120 the address of the frame's local variables
7122 the program counter saved in it (the address of execution in the caller frame)
7124 which registers were saved in the frame
7127 @noindent The verbose description is useful when
7128 something has gone wrong that has made the stack format fail to fit
7129 the usual conventions.
7131 @item info frame @var{addr}
7132 @itemx info f @var{addr}
7133 Print a verbose description of the frame at address @var{addr}, without
7134 selecting that frame. The selected frame remains unchanged by this
7135 command. This requires the same kind of address (more than one for some
7136 architectures) that you specify in the @code{frame} command.
7137 @xref{Selection, ,Selecting a Frame}.
7141 Print the arguments of the selected frame, each on a separate line.
7145 Print the local variables of the selected frame, each on a separate
7146 line. These are all variables (declared either static or automatic)
7147 accessible at the point of execution of the selected frame.
7153 @chapter Examining Source Files
7155 @value{GDBN} can print parts of your program's source, since the debugging
7156 information recorded in the program tells @value{GDBN} what source files were
7157 used to build it. When your program stops, @value{GDBN} spontaneously prints
7158 the line where it stopped. Likewise, when you select a stack frame
7159 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7160 execution in that frame has stopped. You can print other portions of
7161 source files by explicit command.
7163 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7164 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7165 @value{GDBN} under @sc{gnu} Emacs}.
7168 * List:: Printing source lines
7169 * Specify Location:: How to specify code locations
7170 * Edit:: Editing source files
7171 * Search:: Searching source files
7172 * Source Path:: Specifying source directories
7173 * Machine Code:: Source and machine code
7177 @section Printing Source Lines
7180 @kindex l @r{(@code{list})}
7181 To print lines from a source file, use the @code{list} command
7182 (abbreviated @code{l}). By default, ten lines are printed.
7183 There are several ways to specify what part of the file you want to
7184 print; see @ref{Specify Location}, for the full list.
7186 Here are the forms of the @code{list} command most commonly used:
7189 @item list @var{linenum}
7190 Print lines centered around line number @var{linenum} in the
7191 current source file.
7193 @item list @var{function}
7194 Print lines centered around the beginning of function
7198 Print more lines. If the last lines printed were printed with a
7199 @code{list} command, this prints lines following the last lines
7200 printed; however, if the last line printed was a solitary line printed
7201 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7202 Stack}), this prints lines centered around that line.
7205 Print lines just before the lines last printed.
7208 @cindex @code{list}, how many lines to display
7209 By default, @value{GDBN} prints ten source lines with any of these forms of
7210 the @code{list} command. You can change this using @code{set listsize}:
7213 @kindex set listsize
7214 @item set listsize @var{count}
7215 @itemx set listsize unlimited
7216 Make the @code{list} command display @var{count} source lines (unless
7217 the @code{list} argument explicitly specifies some other number).
7218 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7220 @kindex show listsize
7222 Display the number of lines that @code{list} prints.
7225 Repeating a @code{list} command with @key{RET} discards the argument,
7226 so it is equivalent to typing just @code{list}. This is more useful
7227 than listing the same lines again. An exception is made for an
7228 argument of @samp{-}; that argument is preserved in repetition so that
7229 each repetition moves up in the source file.
7231 In general, the @code{list} command expects you to supply zero, one or two
7232 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7233 of writing them (@pxref{Specify Location}), but the effect is always
7234 to specify some source line.
7236 Here is a complete description of the possible arguments for @code{list}:
7239 @item list @var{linespec}
7240 Print lines centered around the line specified by @var{linespec}.
7242 @item list @var{first},@var{last}
7243 Print lines from @var{first} to @var{last}. Both arguments are
7244 linespecs. When a @code{list} command has two linespecs, and the
7245 source file of the second linespec is omitted, this refers to
7246 the same source file as the first linespec.
7248 @item list ,@var{last}
7249 Print lines ending with @var{last}.
7251 @item list @var{first},
7252 Print lines starting with @var{first}.
7255 Print lines just after the lines last printed.
7258 Print lines just before the lines last printed.
7261 As described in the preceding table.
7264 @node Specify Location
7265 @section Specifying a Location
7266 @cindex specifying location
7269 Several @value{GDBN} commands accept arguments that specify a location
7270 of your program's code. Since @value{GDBN} is a source-level
7271 debugger, a location usually specifies some line in the source code;
7272 for that reason, locations are also known as @dfn{linespecs}.
7274 Here are all the different ways of specifying a code location that
7275 @value{GDBN} understands:
7279 Specifies the line number @var{linenum} of the current source file.
7282 @itemx +@var{offset}
7283 Specifies the line @var{offset} lines before or after the @dfn{current
7284 line}. For the @code{list} command, the current line is the last one
7285 printed; for the breakpoint commands, this is the line at which
7286 execution stopped in the currently selected @dfn{stack frame}
7287 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7288 used as the second of the two linespecs in a @code{list} command,
7289 this specifies the line @var{offset} lines up or down from the first
7292 @item @var{filename}:@var{linenum}
7293 Specifies the line @var{linenum} in the source file @var{filename}.
7294 If @var{filename} is a relative file name, then it will match any
7295 source file name with the same trailing components. For example, if
7296 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7297 name of @file{/build/trunk/gcc/expr.c}, but not
7298 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7300 @item @var{function}
7301 Specifies the line that begins the body of the function @var{function}.
7302 For example, in C, this is the line with the open brace.
7304 @item @var{function}:@var{label}
7305 Specifies the line where @var{label} appears in @var{function}.
7307 @item @var{filename}:@var{function}
7308 Specifies the line that begins the body of the function @var{function}
7309 in the file @var{filename}. You only need the file name with a
7310 function name to avoid ambiguity when there are identically named
7311 functions in different source files.
7314 Specifies the line at which the label named @var{label} appears.
7315 @value{GDBN} searches for the label in the function corresponding to
7316 the currently selected stack frame. If there is no current selected
7317 stack frame (for instance, if the inferior is not running), then
7318 @value{GDBN} will not search for a label.
7320 @item *@var{address}
7321 Specifies the program address @var{address}. For line-oriented
7322 commands, such as @code{list} and @code{edit}, this specifies a source
7323 line that contains @var{address}. For @code{break} and other
7324 breakpoint oriented commands, this can be used to set breakpoints in
7325 parts of your program which do not have debugging information or
7328 Here @var{address} may be any expression valid in the current working
7329 language (@pxref{Languages, working language}) that specifies a code
7330 address. In addition, as a convenience, @value{GDBN} extends the
7331 semantics of expressions used in locations to cover the situations
7332 that frequently happen during debugging. Here are the various forms
7336 @item @var{expression}
7337 Any expression valid in the current working language.
7339 @item @var{funcaddr}
7340 An address of a function or procedure derived from its name. In C,
7341 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7342 simply the function's name @var{function} (and actually a special case
7343 of a valid expression). In Pascal and Modula-2, this is
7344 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7345 (although the Pascal form also works).
7347 This form specifies the address of the function's first instruction,
7348 before the stack frame and arguments have been set up.
7350 @item '@var{filename}'::@var{funcaddr}
7351 Like @var{funcaddr} above, but also specifies the name of the source
7352 file explicitly. This is useful if the name of the function does not
7353 specify the function unambiguously, e.g., if there are several
7354 functions with identical names in different source files.
7357 @cindex breakpoint at static probe point
7358 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7359 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7360 applications to embed static probes. @xref{Static Probe Points}, for more
7361 information on finding and using static probes. This form of linespec
7362 specifies the location of such a static probe.
7364 If @var{objfile} is given, only probes coming from that shared library
7365 or executable matching @var{objfile} as a regular expression are considered.
7366 If @var{provider} is given, then only probes from that provider are considered.
7367 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7368 each one of those probes.
7374 @section Editing Source Files
7375 @cindex editing source files
7378 @kindex e @r{(@code{edit})}
7379 To edit the lines in a source file, use the @code{edit} command.
7380 The editing program of your choice
7381 is invoked with the current line set to
7382 the active line in the program.
7383 Alternatively, there are several ways to specify what part of the file you
7384 want to print if you want to see other parts of the program:
7387 @item edit @var{location}
7388 Edit the source file specified by @code{location}. Editing starts at
7389 that @var{location}, e.g., at the specified source line of the
7390 specified file. @xref{Specify Location}, for all the possible forms
7391 of the @var{location} argument; here are the forms of the @code{edit}
7392 command most commonly used:
7395 @item edit @var{number}
7396 Edit the current source file with @var{number} as the active line number.
7398 @item edit @var{function}
7399 Edit the file containing @var{function} at the beginning of its definition.
7404 @subsection Choosing your Editor
7405 You can customize @value{GDBN} to use any editor you want
7407 The only restriction is that your editor (say @code{ex}), recognizes the
7408 following command-line syntax:
7410 ex +@var{number} file
7412 The optional numeric value +@var{number} specifies the number of the line in
7413 the file where to start editing.}.
7414 By default, it is @file{@value{EDITOR}}, but you can change this
7415 by setting the environment variable @code{EDITOR} before using
7416 @value{GDBN}. For example, to configure @value{GDBN} to use the
7417 @code{vi} editor, you could use these commands with the @code{sh} shell:
7423 or in the @code{csh} shell,
7425 setenv EDITOR /usr/bin/vi
7430 @section Searching Source Files
7431 @cindex searching source files
7433 There are two commands for searching through the current source file for a
7438 @kindex forward-search
7439 @kindex fo @r{(@code{forward-search})}
7440 @item forward-search @var{regexp}
7441 @itemx search @var{regexp}
7442 The command @samp{forward-search @var{regexp}} checks each line,
7443 starting with the one following the last line listed, for a match for
7444 @var{regexp}. It lists the line that is found. You can use the
7445 synonym @samp{search @var{regexp}} or abbreviate the command name as
7448 @kindex reverse-search
7449 @item reverse-search @var{regexp}
7450 The command @samp{reverse-search @var{regexp}} checks each line, starting
7451 with the one before the last line listed and going backward, for a match
7452 for @var{regexp}. It lists the line that is found. You can abbreviate
7453 this command as @code{rev}.
7457 @section Specifying Source Directories
7460 @cindex directories for source files
7461 Executable programs sometimes do not record the directories of the source
7462 files from which they were compiled, just the names. Even when they do,
7463 the directories could be moved between the compilation and your debugging
7464 session. @value{GDBN} has a list of directories to search for source files;
7465 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7466 it tries all the directories in the list, in the order they are present
7467 in the list, until it finds a file with the desired name.
7469 For example, suppose an executable references the file
7470 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7471 @file{/mnt/cross}. The file is first looked up literally; if this
7472 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7473 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7474 message is printed. @value{GDBN} does not look up the parts of the
7475 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7476 Likewise, the subdirectories of the source path are not searched: if
7477 the source path is @file{/mnt/cross}, and the binary refers to
7478 @file{foo.c}, @value{GDBN} would not find it under
7479 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7481 Plain file names, relative file names with leading directories, file
7482 names containing dots, etc.@: are all treated as described above; for
7483 instance, if the source path is @file{/mnt/cross}, and the source file
7484 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7485 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7486 that---@file{/mnt/cross/foo.c}.
7488 Note that the executable search path is @emph{not} used to locate the
7491 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7492 any information it has cached about where source files are found and where
7493 each line is in the file.
7497 When you start @value{GDBN}, its source path includes only @samp{cdir}
7498 and @samp{cwd}, in that order.
7499 To add other directories, use the @code{directory} command.
7501 The search path is used to find both program source files and @value{GDBN}
7502 script files (read using the @samp{-command} option and @samp{source} command).
7504 In addition to the source path, @value{GDBN} provides a set of commands
7505 that manage a list of source path substitution rules. A @dfn{substitution
7506 rule} specifies how to rewrite source directories stored in the program's
7507 debug information in case the sources were moved to a different
7508 directory between compilation and debugging. A rule is made of
7509 two strings, the first specifying what needs to be rewritten in
7510 the path, and the second specifying how it should be rewritten.
7511 In @ref{set substitute-path}, we name these two parts @var{from} and
7512 @var{to} respectively. @value{GDBN} does a simple string replacement
7513 of @var{from} with @var{to} at the start of the directory part of the
7514 source file name, and uses that result instead of the original file
7515 name to look up the sources.
7517 Using the previous example, suppose the @file{foo-1.0} tree has been
7518 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7519 @value{GDBN} to replace @file{/usr/src} in all source path names with
7520 @file{/mnt/cross}. The first lookup will then be
7521 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7522 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7523 substitution rule, use the @code{set substitute-path} command
7524 (@pxref{set substitute-path}).
7526 To avoid unexpected substitution results, a rule is applied only if the
7527 @var{from} part of the directory name ends at a directory separator.
7528 For instance, a rule substituting @file{/usr/source} into
7529 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7530 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7531 is applied only at the beginning of the directory name, this rule will
7532 not be applied to @file{/root/usr/source/baz.c} either.
7534 In many cases, you can achieve the same result using the @code{directory}
7535 command. However, @code{set substitute-path} can be more efficient in
7536 the case where the sources are organized in a complex tree with multiple
7537 subdirectories. With the @code{directory} command, you need to add each
7538 subdirectory of your project. If you moved the entire tree while
7539 preserving its internal organization, then @code{set substitute-path}
7540 allows you to direct the debugger to all the sources with one single
7543 @code{set substitute-path} is also more than just a shortcut command.
7544 The source path is only used if the file at the original location no
7545 longer exists. On the other hand, @code{set substitute-path} modifies
7546 the debugger behavior to look at the rewritten location instead. So, if
7547 for any reason a source file that is not relevant to your executable is
7548 located at the original location, a substitution rule is the only
7549 method available to point @value{GDBN} at the new location.
7551 @cindex @samp{--with-relocated-sources}
7552 @cindex default source path substitution
7553 You can configure a default source path substitution rule by
7554 configuring @value{GDBN} with the
7555 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7556 should be the name of a directory under @value{GDBN}'s configured
7557 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7558 directory names in debug information under @var{dir} will be adjusted
7559 automatically if the installed @value{GDBN} is moved to a new
7560 location. This is useful if @value{GDBN}, libraries or executables
7561 with debug information and corresponding source code are being moved
7565 @item directory @var{dirname} @dots{}
7566 @item dir @var{dirname} @dots{}
7567 Add directory @var{dirname} to the front of the source path. Several
7568 directory names may be given to this command, separated by @samp{:}
7569 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7570 part of absolute file names) or
7571 whitespace. You may specify a directory that is already in the source
7572 path; this moves it forward, so @value{GDBN} searches it sooner.
7576 @vindex $cdir@r{, convenience variable}
7577 @vindex $cwd@r{, convenience variable}
7578 @cindex compilation directory
7579 @cindex current directory
7580 @cindex working directory
7581 @cindex directory, current
7582 @cindex directory, compilation
7583 You can use the string @samp{$cdir} to refer to the compilation
7584 directory (if one is recorded), and @samp{$cwd} to refer to the current
7585 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7586 tracks the current working directory as it changes during your @value{GDBN}
7587 session, while the latter is immediately expanded to the current
7588 directory at the time you add an entry to the source path.
7591 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7593 @c RET-repeat for @code{directory} is explicitly disabled, but since
7594 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7596 @item set directories @var{path-list}
7597 @kindex set directories
7598 Set the source path to @var{path-list}.
7599 @samp{$cdir:$cwd} are added if missing.
7601 @item show directories
7602 @kindex show directories
7603 Print the source path: show which directories it contains.
7605 @anchor{set substitute-path}
7606 @item set substitute-path @var{from} @var{to}
7607 @kindex set substitute-path
7608 Define a source path substitution rule, and add it at the end of the
7609 current list of existing substitution rules. If a rule with the same
7610 @var{from} was already defined, then the old rule is also deleted.
7612 For example, if the file @file{/foo/bar/baz.c} was moved to
7613 @file{/mnt/cross/baz.c}, then the command
7616 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7620 will tell @value{GDBN} to replace @samp{/usr/src} with
7621 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7622 @file{baz.c} even though it was moved.
7624 In the case when more than one substitution rule have been defined,
7625 the rules are evaluated one by one in the order where they have been
7626 defined. The first one matching, if any, is selected to perform
7629 For instance, if we had entered the following commands:
7632 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7633 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7637 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7638 @file{/mnt/include/defs.h} by using the first rule. However, it would
7639 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7640 @file{/mnt/src/lib/foo.c}.
7643 @item unset substitute-path [path]
7644 @kindex unset substitute-path
7645 If a path is specified, search the current list of substitution rules
7646 for a rule that would rewrite that path. Delete that rule if found.
7647 A warning is emitted by the debugger if no rule could be found.
7649 If no path is specified, then all substitution rules are deleted.
7651 @item show substitute-path [path]
7652 @kindex show substitute-path
7653 If a path is specified, then print the source path substitution rule
7654 which would rewrite that path, if any.
7656 If no path is specified, then print all existing source path substitution
7661 If your source path is cluttered with directories that are no longer of
7662 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7663 versions of source. You can correct the situation as follows:
7667 Use @code{directory} with no argument to reset the source path to its default value.
7670 Use @code{directory} with suitable arguments to reinstall the
7671 directories you want in the source path. You can add all the
7672 directories in one command.
7676 @section Source and Machine Code
7677 @cindex source line and its code address
7679 You can use the command @code{info line} to map source lines to program
7680 addresses (and vice versa), and the command @code{disassemble} to display
7681 a range of addresses as machine instructions. You can use the command
7682 @code{set disassemble-next-line} to set whether to disassemble next
7683 source line when execution stops. When run under @sc{gnu} Emacs
7684 mode, the @code{info line} command causes the arrow to point to the
7685 line specified. Also, @code{info line} prints addresses in symbolic form as
7690 @item info line @var{linespec}
7691 Print the starting and ending addresses of the compiled code for
7692 source line @var{linespec}. You can specify source lines in any of
7693 the ways documented in @ref{Specify Location}.
7696 For example, we can use @code{info line} to discover the location of
7697 the object code for the first line of function
7698 @code{m4_changequote}:
7700 @c FIXME: I think this example should also show the addresses in
7701 @c symbolic form, as they usually would be displayed.
7703 (@value{GDBP}) info line m4_changequote
7704 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7708 @cindex code address and its source line
7709 We can also inquire (using @code{*@var{addr}} as the form for
7710 @var{linespec}) what source line covers a particular address:
7712 (@value{GDBP}) info line *0x63ff
7713 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7716 @cindex @code{$_} and @code{info line}
7717 @cindex @code{x} command, default address
7718 @kindex x@r{(examine), and} info line
7719 After @code{info line}, the default address for the @code{x} command
7720 is changed to the starting address of the line, so that @samp{x/i} is
7721 sufficient to begin examining the machine code (@pxref{Memory,
7722 ,Examining Memory}). Also, this address is saved as the value of the
7723 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7728 @cindex assembly instructions
7729 @cindex instructions, assembly
7730 @cindex machine instructions
7731 @cindex listing machine instructions
7733 @itemx disassemble /m
7734 @itemx disassemble /r
7735 This specialized command dumps a range of memory as machine
7736 instructions. It can also print mixed source+disassembly by specifying
7737 the @code{/m} modifier and print the raw instructions in hex as well as
7738 in symbolic form by specifying the @code{/r}.
7739 The default memory range is the function surrounding the
7740 program counter of the selected frame. A single argument to this
7741 command is a program counter value; @value{GDBN} dumps the function
7742 surrounding this value. When two arguments are given, they should
7743 be separated by a comma, possibly surrounded by whitespace. The
7744 arguments specify a range of addresses to dump, in one of two forms:
7747 @item @var{start},@var{end}
7748 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7749 @item @var{start},+@var{length}
7750 the addresses from @var{start} (inclusive) to
7751 @code{@var{start}+@var{length}} (exclusive).
7755 When 2 arguments are specified, the name of the function is also
7756 printed (since there could be several functions in the given range).
7758 The argument(s) can be any expression yielding a numeric value, such as
7759 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7761 If the range of memory being disassembled contains current program counter,
7762 the instruction at that location is shown with a @code{=>} marker.
7765 The following example shows the disassembly of a range of addresses of
7766 HP PA-RISC 2.0 code:
7769 (@value{GDBP}) disas 0x32c4, 0x32e4
7770 Dump of assembler code from 0x32c4 to 0x32e4:
7771 0x32c4 <main+204>: addil 0,dp
7772 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7773 0x32cc <main+212>: ldil 0x3000,r31
7774 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7775 0x32d4 <main+220>: ldo 0(r31),rp
7776 0x32d8 <main+224>: addil -0x800,dp
7777 0x32dc <main+228>: ldo 0x588(r1),r26
7778 0x32e0 <main+232>: ldil 0x3000,r31
7779 End of assembler dump.
7782 Here is an example showing mixed source+assembly for Intel x86, when the
7783 program is stopped just after function prologue:
7786 (@value{GDBP}) disas /m main
7787 Dump of assembler code for function main:
7789 0x08048330 <+0>: push %ebp
7790 0x08048331 <+1>: mov %esp,%ebp
7791 0x08048333 <+3>: sub $0x8,%esp
7792 0x08048336 <+6>: and $0xfffffff0,%esp
7793 0x08048339 <+9>: sub $0x10,%esp
7795 6 printf ("Hello.\n");
7796 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7797 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7801 0x08048348 <+24>: mov $0x0,%eax
7802 0x0804834d <+29>: leave
7803 0x0804834e <+30>: ret
7805 End of assembler dump.
7808 Here is another example showing raw instructions in hex for AMD x86-64,
7811 (gdb) disas /r 0x400281,+10
7812 Dump of assembler code from 0x400281 to 0x40028b:
7813 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7814 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7815 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7816 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7817 End of assembler dump.
7820 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7821 So, for example, if you want to disassemble function @code{bar}
7822 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7823 and not @samp{disassemble foo.c:bar}.
7825 Some architectures have more than one commonly-used set of instruction
7826 mnemonics or other syntax.
7828 For programs that were dynamically linked and use shared libraries,
7829 instructions that call functions or branch to locations in the shared
7830 libraries might show a seemingly bogus location---it's actually a
7831 location of the relocation table. On some architectures, @value{GDBN}
7832 might be able to resolve these to actual function names.
7835 @kindex set disassembly-flavor
7836 @cindex Intel disassembly flavor
7837 @cindex AT&T disassembly flavor
7838 @item set disassembly-flavor @var{instruction-set}
7839 Select the instruction set to use when disassembling the
7840 program via the @code{disassemble} or @code{x/i} commands.
7842 Currently this command is only defined for the Intel x86 family. You
7843 can set @var{instruction-set} to either @code{intel} or @code{att}.
7844 The default is @code{att}, the AT&T flavor used by default by Unix
7845 assemblers for x86-based targets.
7847 @kindex show disassembly-flavor
7848 @item show disassembly-flavor
7849 Show the current setting of the disassembly flavor.
7853 @kindex set disassemble-next-line
7854 @kindex show disassemble-next-line
7855 @item set disassemble-next-line
7856 @itemx show disassemble-next-line
7857 Control whether or not @value{GDBN} will disassemble the next source
7858 line or instruction when execution stops. If ON, @value{GDBN} will
7859 display disassembly of the next source line when execution of the
7860 program being debugged stops. This is @emph{in addition} to
7861 displaying the source line itself, which @value{GDBN} always does if
7862 possible. If the next source line cannot be displayed for some reason
7863 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7864 info in the debug info), @value{GDBN} will display disassembly of the
7865 next @emph{instruction} instead of showing the next source line. If
7866 AUTO, @value{GDBN} will display disassembly of next instruction only
7867 if the source line cannot be displayed. This setting causes
7868 @value{GDBN} to display some feedback when you step through a function
7869 with no line info or whose source file is unavailable. The default is
7870 OFF, which means never display the disassembly of the next line or
7876 @chapter Examining Data
7878 @cindex printing data
7879 @cindex examining data
7882 The usual way to examine data in your program is with the @code{print}
7883 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7884 evaluates and prints the value of an expression of the language your
7885 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7886 Different Languages}). It may also print the expression using a
7887 Python-based pretty-printer (@pxref{Pretty Printing}).
7890 @item print @var{expr}
7891 @itemx print /@var{f} @var{expr}
7892 @var{expr} is an expression (in the source language). By default the
7893 value of @var{expr} is printed in a format appropriate to its data type;
7894 you can choose a different format by specifying @samp{/@var{f}}, where
7895 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7899 @itemx print /@var{f}
7900 @cindex reprint the last value
7901 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7902 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7903 conveniently inspect the same value in an alternative format.
7906 A more low-level way of examining data is with the @code{x} command.
7907 It examines data in memory at a specified address and prints it in a
7908 specified format. @xref{Memory, ,Examining Memory}.
7910 If you are interested in information about types, or about how the
7911 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7912 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7915 @cindex exploring hierarchical data structures
7917 Another way of examining values of expressions and type information is
7918 through the Python extension command @code{explore} (available only if
7919 the @value{GDBN} build is configured with @code{--with-python}). It
7920 offers an interactive way to start at the highest level (or, the most
7921 abstract level) of the data type of an expression (or, the data type
7922 itself) and explore all the way down to leaf scalar values/fields
7923 embedded in the higher level data types.
7926 @item explore @var{arg}
7927 @var{arg} is either an expression (in the source language), or a type
7928 visible in the current context of the program being debugged.
7931 The working of the @code{explore} command can be illustrated with an
7932 example. If a data type @code{struct ComplexStruct} is defined in your
7942 struct ComplexStruct
7944 struct SimpleStruct *ss_p;
7950 followed by variable declarations as
7953 struct SimpleStruct ss = @{ 10, 1.11 @};
7954 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7958 then, the value of the variable @code{cs} can be explored using the
7959 @code{explore} command as follows.
7963 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7964 the following fields:
7966 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7967 arr = <Enter 1 to explore this field of type `int [10]'>
7969 Enter the field number of choice:
7973 Since the fields of @code{cs} are not scalar values, you are being
7974 prompted to chose the field you want to explore. Let's say you choose
7975 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7976 pointer, you will be asked if it is pointing to a single value. From
7977 the declaration of @code{cs} above, it is indeed pointing to a single
7978 value, hence you enter @code{y}. If you enter @code{n}, then you will
7979 be asked if it were pointing to an array of values, in which case this
7980 field will be explored as if it were an array.
7983 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7984 Continue exploring it as a pointer to a single value [y/n]: y
7985 The value of `*(cs.ss_p)' is a struct/class of type `struct
7986 SimpleStruct' with the following fields:
7988 i = 10 .. (Value of type `int')
7989 d = 1.1100000000000001 .. (Value of type `double')
7991 Press enter to return to parent value:
7995 If the field @code{arr} of @code{cs} was chosen for exploration by
7996 entering @code{1} earlier, then since it is as array, you will be
7997 prompted to enter the index of the element in the array that you want
8001 `cs.arr' is an array of `int'.
8002 Enter the index of the element you want to explore in `cs.arr': 5
8004 `(cs.arr)[5]' is a scalar value of type `int'.
8008 Press enter to return to parent value:
8011 In general, at any stage of exploration, you can go deeper towards the
8012 leaf values by responding to the prompts appropriately, or hit the
8013 return key to return to the enclosing data structure (the @i{higher}
8014 level data structure).
8016 Similar to exploring values, you can use the @code{explore} command to
8017 explore types. Instead of specifying a value (which is typically a
8018 variable name or an expression valid in the current context of the
8019 program being debugged), you specify a type name. If you consider the
8020 same example as above, your can explore the type
8021 @code{struct ComplexStruct} by passing the argument
8022 @code{struct ComplexStruct} to the @code{explore} command.
8025 (gdb) explore struct ComplexStruct
8029 By responding to the prompts appropriately in the subsequent interactive
8030 session, you can explore the type @code{struct ComplexStruct} in a
8031 manner similar to how the value @code{cs} was explored in the above
8034 The @code{explore} command also has two sub-commands,
8035 @code{explore value} and @code{explore type}. The former sub-command is
8036 a way to explicitly specify that value exploration of the argument is
8037 being invoked, while the latter is a way to explicitly specify that type
8038 exploration of the argument is being invoked.
8041 @item explore value @var{expr}
8042 @cindex explore value
8043 This sub-command of @code{explore} explores the value of the
8044 expression @var{expr} (if @var{expr} is an expression valid in the
8045 current context of the program being debugged). The behavior of this
8046 command is identical to that of the behavior of the @code{explore}
8047 command being passed the argument @var{expr}.
8049 @item explore type @var{arg}
8050 @cindex explore type
8051 This sub-command of @code{explore} explores the type of @var{arg} (if
8052 @var{arg} is a type visible in the current context of program being
8053 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8054 is an expression valid in the current context of the program being
8055 debugged). If @var{arg} is a type, then the behavior of this command is
8056 identical to that of the @code{explore} command being passed the
8057 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8058 this command will be identical to that of the @code{explore} command
8059 being passed the type of @var{arg} as the argument.
8063 * Expressions:: Expressions
8064 * Ambiguous Expressions:: Ambiguous Expressions
8065 * Variables:: Program variables
8066 * Arrays:: Artificial arrays
8067 * Output Formats:: Output formats
8068 * Memory:: Examining memory
8069 * Auto Display:: Automatic display
8070 * Print Settings:: Print settings
8071 * Pretty Printing:: Python pretty printing
8072 * Value History:: Value history
8073 * Convenience Vars:: Convenience variables
8074 * Convenience Funs:: Convenience functions
8075 * Registers:: Registers
8076 * Floating Point Hardware:: Floating point hardware
8077 * Vector Unit:: Vector Unit
8078 * OS Information:: Auxiliary data provided by operating system
8079 * Memory Region Attributes:: Memory region attributes
8080 * Dump/Restore Files:: Copy between memory and a file
8081 * Core File Generation:: Cause a program dump its core
8082 * Character Sets:: Debugging programs that use a different
8083 character set than GDB does
8084 * Caching Target Data:: Data caching for targets
8085 * Searching Memory:: Searching memory for a sequence of bytes
8089 @section Expressions
8092 @code{print} and many other @value{GDBN} commands accept an expression and
8093 compute its value. Any kind of constant, variable or operator defined
8094 by the programming language you are using is valid in an expression in
8095 @value{GDBN}. This includes conditional expressions, function calls,
8096 casts, and string constants. It also includes preprocessor macros, if
8097 you compiled your program to include this information; see
8100 @cindex arrays in expressions
8101 @value{GDBN} supports array constants in expressions input by
8102 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8103 you can use the command @code{print @{1, 2, 3@}} to create an array
8104 of three integers. If you pass an array to a function or assign it
8105 to a program variable, @value{GDBN} copies the array to memory that
8106 is @code{malloc}ed in the target program.
8108 Because C is so widespread, most of the expressions shown in examples in
8109 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8110 Languages}, for information on how to use expressions in other
8113 In this section, we discuss operators that you can use in @value{GDBN}
8114 expressions regardless of your programming language.
8116 @cindex casts, in expressions
8117 Casts are supported in all languages, not just in C, because it is so
8118 useful to cast a number into a pointer in order to examine a structure
8119 at that address in memory.
8120 @c FIXME: casts supported---Mod2 true?
8122 @value{GDBN} supports these operators, in addition to those common
8123 to programming languages:
8127 @samp{@@} is a binary operator for treating parts of memory as arrays.
8128 @xref{Arrays, ,Artificial Arrays}, for more information.
8131 @samp{::} allows you to specify a variable in terms of the file or
8132 function where it is defined. @xref{Variables, ,Program Variables}.
8134 @cindex @{@var{type}@}
8135 @cindex type casting memory
8136 @cindex memory, viewing as typed object
8137 @cindex casts, to view memory
8138 @item @{@var{type}@} @var{addr}
8139 Refers to an object of type @var{type} stored at address @var{addr} in
8140 memory. @var{addr} may be any expression whose value is an integer or
8141 pointer (but parentheses are required around binary operators, just as in
8142 a cast). This construct is allowed regardless of what kind of data is
8143 normally supposed to reside at @var{addr}.
8146 @node Ambiguous Expressions
8147 @section Ambiguous Expressions
8148 @cindex ambiguous expressions
8150 Expressions can sometimes contain some ambiguous elements. For instance,
8151 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8152 a single function name to be defined several times, for application in
8153 different contexts. This is called @dfn{overloading}. Another example
8154 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8155 templates and is typically instantiated several times, resulting in
8156 the same function name being defined in different contexts.
8158 In some cases and depending on the language, it is possible to adjust
8159 the expression to remove the ambiguity. For instance in C@t{++}, you
8160 can specify the signature of the function you want to break on, as in
8161 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8162 qualified name of your function often makes the expression unambiguous
8165 When an ambiguity that needs to be resolved is detected, the debugger
8166 has the capability to display a menu of numbered choices for each
8167 possibility, and then waits for the selection with the prompt @samp{>}.
8168 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8169 aborts the current command. If the command in which the expression was
8170 used allows more than one choice to be selected, the next option in the
8171 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8174 For example, the following session excerpt shows an attempt to set a
8175 breakpoint at the overloaded symbol @code{String::after}.
8176 We choose three particular definitions of that function name:
8178 @c FIXME! This is likely to change to show arg type lists, at least
8181 (@value{GDBP}) b String::after
8184 [2] file:String.cc; line number:867
8185 [3] file:String.cc; line number:860
8186 [4] file:String.cc; line number:875
8187 [5] file:String.cc; line number:853
8188 [6] file:String.cc; line number:846
8189 [7] file:String.cc; line number:735
8191 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8192 Breakpoint 2 at 0xb344: file String.cc, line 875.
8193 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8194 Multiple breakpoints were set.
8195 Use the "delete" command to delete unwanted
8202 @kindex set multiple-symbols
8203 @item set multiple-symbols @var{mode}
8204 @cindex multiple-symbols menu
8206 This option allows you to adjust the debugger behavior when an expression
8209 By default, @var{mode} is set to @code{all}. If the command with which
8210 the expression is used allows more than one choice, then @value{GDBN}
8211 automatically selects all possible choices. For instance, inserting
8212 a breakpoint on a function using an ambiguous name results in a breakpoint
8213 inserted on each possible match. However, if a unique choice must be made,
8214 then @value{GDBN} uses the menu to help you disambiguate the expression.
8215 For instance, printing the address of an overloaded function will result
8216 in the use of the menu.
8218 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8219 when an ambiguity is detected.
8221 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8222 an error due to the ambiguity and the command is aborted.
8224 @kindex show multiple-symbols
8225 @item show multiple-symbols
8226 Show the current value of the @code{multiple-symbols} setting.
8230 @section Program Variables
8232 The most common kind of expression to use is the name of a variable
8235 Variables in expressions are understood in the selected stack frame
8236 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8240 global (or file-static)
8247 visible according to the scope rules of the
8248 programming language from the point of execution in that frame
8251 @noindent This means that in the function
8266 you can examine and use the variable @code{a} whenever your program is
8267 executing within the function @code{foo}, but you can only use or
8268 examine the variable @code{b} while your program is executing inside
8269 the block where @code{b} is declared.
8271 @cindex variable name conflict
8272 There is an exception: you can refer to a variable or function whose
8273 scope is a single source file even if the current execution point is not
8274 in this file. But it is possible to have more than one such variable or
8275 function with the same name (in different source files). If that
8276 happens, referring to that name has unpredictable effects. If you wish,
8277 you can specify a static variable in a particular function or file by
8278 using the colon-colon (@code{::}) notation:
8280 @cindex colon-colon, context for variables/functions
8282 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8283 @cindex @code{::}, context for variables/functions
8286 @var{file}::@var{variable}
8287 @var{function}::@var{variable}
8291 Here @var{file} or @var{function} is the name of the context for the
8292 static @var{variable}. In the case of file names, you can use quotes to
8293 make sure @value{GDBN} parses the file name as a single word---for example,
8294 to print a global value of @code{x} defined in @file{f2.c}:
8297 (@value{GDBP}) p 'f2.c'::x
8300 The @code{::} notation is normally used for referring to
8301 static variables, since you typically disambiguate uses of local variables
8302 in functions by selecting the appropriate frame and using the
8303 simple name of the variable. However, you may also use this notation
8304 to refer to local variables in frames enclosing the selected frame:
8313 process (a); /* Stop here */
8324 For example, if there is a breakpoint at the commented line,
8325 here is what you might see
8326 when the program stops after executing the call @code{bar(0)}:
8331 (@value{GDBP}) p bar::a
8334 #2 0x080483d0 in foo (a=5) at foobar.c:12
8337 (@value{GDBP}) p bar::a
8341 @cindex C@t{++} scope resolution
8342 These uses of @samp{::} are very rarely in conflict with the very
8343 similar use of the same notation in C@t{++}. When they are in
8344 conflict, the C@t{++} meaning takes precedence; however, this can be
8345 overridden by quoting the file or function name with single quotes.
8347 For example, suppose the program is stopped in a method of a class
8348 that has a field named @code{includefile}, and there is also an
8349 include file named @file{includefile} that defines a variable,
8353 (@value{GDBP}) p includefile
8355 (@value{GDBP}) p includefile::some_global
8356 A syntax error in expression, near `'.
8357 (@value{GDBP}) p 'includefile'::some_global
8361 @cindex wrong values
8362 @cindex variable values, wrong
8363 @cindex function entry/exit, wrong values of variables
8364 @cindex optimized code, wrong values of variables
8366 @emph{Warning:} Occasionally, a local variable may appear to have the
8367 wrong value at certain points in a function---just after entry to a new
8368 scope, and just before exit.
8370 You may see this problem when you are stepping by machine instructions.
8371 This is because, on most machines, it takes more than one instruction to
8372 set up a stack frame (including local variable definitions); if you are
8373 stepping by machine instructions, variables may appear to have the wrong
8374 values until the stack frame is completely built. On exit, it usually
8375 also takes more than one machine instruction to destroy a stack frame;
8376 after you begin stepping through that group of instructions, local
8377 variable definitions may be gone.
8379 This may also happen when the compiler does significant optimizations.
8380 To be sure of always seeing accurate values, turn off all optimization
8383 @cindex ``No symbol "foo" in current context''
8384 Another possible effect of compiler optimizations is to optimize
8385 unused variables out of existence, or assign variables to registers (as
8386 opposed to memory addresses). Depending on the support for such cases
8387 offered by the debug info format used by the compiler, @value{GDBN}
8388 might not be able to display values for such local variables. If that
8389 happens, @value{GDBN} will print a message like this:
8392 No symbol "foo" in current context.
8395 To solve such problems, either recompile without optimizations, or use a
8396 different debug info format, if the compiler supports several such
8397 formats. @xref{Compilation}, for more information on choosing compiler
8398 options. @xref{C, ,C and C@t{++}}, for more information about debug
8399 info formats that are best suited to C@t{++} programs.
8401 If you ask to print an object whose contents are unknown to
8402 @value{GDBN}, e.g., because its data type is not completely specified
8403 by the debug information, @value{GDBN} will say @samp{<incomplete
8404 type>}. @xref{Symbols, incomplete type}, for more about this.
8406 If you append @kbd{@@entry} string to a function parameter name you get its
8407 value at the time the function got called. If the value is not available an
8408 error message is printed. Entry values are available only with some compilers.
8409 Entry values are normally also printed at the function parameter list according
8410 to @ref{set print entry-values}.
8413 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8419 (gdb) print i@@entry
8423 Strings are identified as arrays of @code{char} values without specified
8424 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8425 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8426 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8427 defines literal string type @code{"char"} as @code{char} without a sign.
8432 signed char var1[] = "A";
8435 You get during debugging
8440 $2 = @{65 'A', 0 '\0'@}
8444 @section Artificial Arrays
8446 @cindex artificial array
8448 @kindex @@@r{, referencing memory as an array}
8449 It is often useful to print out several successive objects of the
8450 same type in memory; a section of an array, or an array of
8451 dynamically determined size for which only a pointer exists in the
8454 You can do this by referring to a contiguous span of memory as an
8455 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8456 operand of @samp{@@} should be the first element of the desired array
8457 and be an individual object. The right operand should be the desired length
8458 of the array. The result is an array value whose elements are all of
8459 the type of the left argument. The first element is actually the left
8460 argument; the second element comes from bytes of memory immediately
8461 following those that hold the first element, and so on. Here is an
8462 example. If a program says
8465 int *array = (int *) malloc (len * sizeof (int));
8469 you can print the contents of @code{array} with
8475 The left operand of @samp{@@} must reside in memory. Array values made
8476 with @samp{@@} in this way behave just like other arrays in terms of
8477 subscripting, and are coerced to pointers when used in expressions.
8478 Artificial arrays most often appear in expressions via the value history
8479 (@pxref{Value History, ,Value History}), after printing one out.
8481 Another way to create an artificial array is to use a cast.
8482 This re-interprets a value as if it were an array.
8483 The value need not be in memory:
8485 (@value{GDBP}) p/x (short[2])0x12345678
8486 $1 = @{0x1234, 0x5678@}
8489 As a convenience, if you leave the array length out (as in
8490 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8491 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8493 (@value{GDBP}) p/x (short[])0x12345678
8494 $2 = @{0x1234, 0x5678@}
8497 Sometimes the artificial array mechanism is not quite enough; in
8498 moderately complex data structures, the elements of interest may not
8499 actually be adjacent---for example, if you are interested in the values
8500 of pointers in an array. One useful work-around in this situation is
8501 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8502 Variables}) as a counter in an expression that prints the first
8503 interesting value, and then repeat that expression via @key{RET}. For
8504 instance, suppose you have an array @code{dtab} of pointers to
8505 structures, and you are interested in the values of a field @code{fv}
8506 in each structure. Here is an example of what you might type:
8516 @node Output Formats
8517 @section Output Formats
8519 @cindex formatted output
8520 @cindex output formats
8521 By default, @value{GDBN} prints a value according to its data type. Sometimes
8522 this is not what you want. For example, you might want to print a number
8523 in hex, or a pointer in decimal. Or you might want to view data in memory
8524 at a certain address as a character string or as an instruction. To do
8525 these things, specify an @dfn{output format} when you print a value.
8527 The simplest use of output formats is to say how to print a value
8528 already computed. This is done by starting the arguments of the
8529 @code{print} command with a slash and a format letter. The format
8530 letters supported are:
8534 Regard the bits of the value as an integer, and print the integer in
8538 Print as integer in signed decimal.
8541 Print as integer in unsigned decimal.
8544 Print as integer in octal.
8547 Print as integer in binary. The letter @samp{t} stands for ``two''.
8548 @footnote{@samp{b} cannot be used because these format letters are also
8549 used with the @code{x} command, where @samp{b} stands for ``byte'';
8550 see @ref{Memory,,Examining Memory}.}
8553 @cindex unknown address, locating
8554 @cindex locate address
8555 Print as an address, both absolute in hexadecimal and as an offset from
8556 the nearest preceding symbol. You can use this format used to discover
8557 where (in what function) an unknown address is located:
8560 (@value{GDBP}) p/a 0x54320
8561 $3 = 0x54320 <_initialize_vx+396>
8565 The command @code{info symbol 0x54320} yields similar results.
8566 @xref{Symbols, info symbol}.
8569 Regard as an integer and print it as a character constant. This
8570 prints both the numerical value and its character representation. The
8571 character representation is replaced with the octal escape @samp{\nnn}
8572 for characters outside the 7-bit @sc{ascii} range.
8574 Without this format, @value{GDBN} displays @code{char},
8575 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8576 constants. Single-byte members of vectors are displayed as integer
8580 Regard the bits of the value as a floating point number and print
8581 using typical floating point syntax.
8584 @cindex printing strings
8585 @cindex printing byte arrays
8586 Regard as a string, if possible. With this format, pointers to single-byte
8587 data are displayed as null-terminated strings and arrays of single-byte data
8588 are displayed as fixed-length strings. Other values are displayed in their
8591 Without this format, @value{GDBN} displays pointers to and arrays of
8592 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8593 strings. Single-byte members of a vector are displayed as an integer
8597 Like @samp{x} formatting, the value is treated as an integer and
8598 printed as hexadecimal, but leading zeros are printed to pad the value
8599 to the size of the integer type.
8602 @cindex raw printing
8603 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8604 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8605 Printing}). This typically results in a higher-level display of the
8606 value's contents. The @samp{r} format bypasses any Python
8607 pretty-printer which might exist.
8610 For example, to print the program counter in hex (@pxref{Registers}), type
8617 Note that no space is required before the slash; this is because command
8618 names in @value{GDBN} cannot contain a slash.
8620 To reprint the last value in the value history with a different format,
8621 you can use the @code{print} command with just a format and no
8622 expression. For example, @samp{p/x} reprints the last value in hex.
8625 @section Examining Memory
8627 You can use the command @code{x} (for ``examine'') to examine memory in
8628 any of several formats, independently of your program's data types.
8630 @cindex examining memory
8632 @kindex x @r{(examine memory)}
8633 @item x/@var{nfu} @var{addr}
8636 Use the @code{x} command to examine memory.
8639 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8640 much memory to display and how to format it; @var{addr} is an
8641 expression giving the address where you want to start displaying memory.
8642 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8643 Several commands set convenient defaults for @var{addr}.
8646 @item @var{n}, the repeat count
8647 The repeat count is a decimal integer; the default is 1. It specifies
8648 how much memory (counting by units @var{u}) to display.
8649 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8652 @item @var{f}, the display format
8653 The display format is one of the formats used by @code{print}
8654 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8655 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8656 The default is @samp{x} (hexadecimal) initially. The default changes
8657 each time you use either @code{x} or @code{print}.
8659 @item @var{u}, the unit size
8660 The unit size is any of
8666 Halfwords (two bytes).
8668 Words (four bytes). This is the initial default.
8670 Giant words (eight bytes).
8673 Each time you specify a unit size with @code{x}, that size becomes the
8674 default unit the next time you use @code{x}. For the @samp{i} format,
8675 the unit size is ignored and is normally not written. For the @samp{s} format,
8676 the unit size defaults to @samp{b}, unless it is explicitly given.
8677 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8678 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8679 Note that the results depend on the programming language of the
8680 current compilation unit. If the language is C, the @samp{s}
8681 modifier will use the UTF-16 encoding while @samp{w} will use
8682 UTF-32. The encoding is set by the programming language and cannot
8685 @item @var{addr}, starting display address
8686 @var{addr} is the address where you want @value{GDBN} to begin displaying
8687 memory. The expression need not have a pointer value (though it may);
8688 it is always interpreted as an integer address of a byte of memory.
8689 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8690 @var{addr} is usually just after the last address examined---but several
8691 other commands also set the default address: @code{info breakpoints} (to
8692 the address of the last breakpoint listed), @code{info line} (to the
8693 starting address of a line), and @code{print} (if you use it to display
8694 a value from memory).
8697 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8698 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8699 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8700 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8701 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8703 Since the letters indicating unit sizes are all distinct from the
8704 letters specifying output formats, you do not have to remember whether
8705 unit size or format comes first; either order works. The output
8706 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8707 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8709 Even though the unit size @var{u} is ignored for the formats @samp{s}
8710 and @samp{i}, you might still want to use a count @var{n}; for example,
8711 @samp{3i} specifies that you want to see three machine instructions,
8712 including any operands. For convenience, especially when used with
8713 the @code{display} command, the @samp{i} format also prints branch delay
8714 slot instructions, if any, beyond the count specified, which immediately
8715 follow the last instruction that is within the count. The command
8716 @code{disassemble} gives an alternative way of inspecting machine
8717 instructions; see @ref{Machine Code,,Source and Machine Code}.
8719 All the defaults for the arguments to @code{x} are designed to make it
8720 easy to continue scanning memory with minimal specifications each time
8721 you use @code{x}. For example, after you have inspected three machine
8722 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8723 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8724 the repeat count @var{n} is used again; the other arguments default as
8725 for successive uses of @code{x}.
8727 When examining machine instructions, the instruction at current program
8728 counter is shown with a @code{=>} marker. For example:
8731 (@value{GDBP}) x/5i $pc-6
8732 0x804837f <main+11>: mov %esp,%ebp
8733 0x8048381 <main+13>: push %ecx
8734 0x8048382 <main+14>: sub $0x4,%esp
8735 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8736 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8739 @cindex @code{$_}, @code{$__}, and value history
8740 The addresses and contents printed by the @code{x} command are not saved
8741 in the value history because there is often too much of them and they
8742 would get in the way. Instead, @value{GDBN} makes these values available for
8743 subsequent use in expressions as values of the convenience variables
8744 @code{$_} and @code{$__}. After an @code{x} command, the last address
8745 examined is available for use in expressions in the convenience variable
8746 @code{$_}. The contents of that address, as examined, are available in
8747 the convenience variable @code{$__}.
8749 If the @code{x} command has a repeat count, the address and contents saved
8750 are from the last memory unit printed; this is not the same as the last
8751 address printed if several units were printed on the last line of output.
8753 @cindex remote memory comparison
8754 @cindex verify remote memory image
8755 When you are debugging a program running on a remote target machine
8756 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8757 remote machine's memory against the executable file you downloaded to
8758 the target. The @code{compare-sections} command is provided for such
8762 @kindex compare-sections
8763 @item compare-sections @r{[}@var{section-name}@r{]}
8764 Compare the data of a loadable section @var{section-name} in the
8765 executable file of the program being debugged with the same section in
8766 the remote machine's memory, and report any mismatches. With no
8767 arguments, compares all loadable sections. This command's
8768 availability depends on the target's support for the @code{"qCRC"}
8773 @section Automatic Display
8774 @cindex automatic display
8775 @cindex display of expressions
8777 If you find that you want to print the value of an expression frequently
8778 (to see how it changes), you might want to add it to the @dfn{automatic
8779 display list} so that @value{GDBN} prints its value each time your program stops.
8780 Each expression added to the list is given a number to identify it;
8781 to remove an expression from the list, you specify that number.
8782 The automatic display looks like this:
8786 3: bar[5] = (struct hack *) 0x3804
8790 This display shows item numbers, expressions and their current values. As with
8791 displays you request manually using @code{x} or @code{print}, you can
8792 specify the output format you prefer; in fact, @code{display} decides
8793 whether to use @code{print} or @code{x} depending your format
8794 specification---it uses @code{x} if you specify either the @samp{i}
8795 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8799 @item display @var{expr}
8800 Add the expression @var{expr} to the list of expressions to display
8801 each time your program stops. @xref{Expressions, ,Expressions}.
8803 @code{display} does not repeat if you press @key{RET} again after using it.
8805 @item display/@var{fmt} @var{expr}
8806 For @var{fmt} specifying only a display format and not a size or
8807 count, add the expression @var{expr} to the auto-display list but
8808 arrange to display it each time in the specified format @var{fmt}.
8809 @xref{Output Formats,,Output Formats}.
8811 @item display/@var{fmt} @var{addr}
8812 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8813 number of units, add the expression @var{addr} as a memory address to
8814 be examined each time your program stops. Examining means in effect
8815 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8818 For example, @samp{display/i $pc} can be helpful, to see the machine
8819 instruction about to be executed each time execution stops (@samp{$pc}
8820 is a common name for the program counter; @pxref{Registers, ,Registers}).
8823 @kindex delete display
8825 @item undisplay @var{dnums}@dots{}
8826 @itemx delete display @var{dnums}@dots{}
8827 Remove items from the list of expressions to display. Specify the
8828 numbers of the displays that you want affected with the command
8829 argument @var{dnums}. It can be a single display number, one of the
8830 numbers shown in the first field of the @samp{info display} display;
8831 or it could be a range of display numbers, as in @code{2-4}.
8833 @code{undisplay} does not repeat if you press @key{RET} after using it.
8834 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8836 @kindex disable display
8837 @item disable display @var{dnums}@dots{}
8838 Disable the display of item numbers @var{dnums}. A disabled display
8839 item is not printed automatically, but is not forgotten. It may be
8840 enabled again later. Specify the numbers of the displays that you
8841 want affected with the command argument @var{dnums}. It can be a
8842 single display number, one of the numbers shown in the first field of
8843 the @samp{info display} display; or it could be a range of display
8844 numbers, as in @code{2-4}.
8846 @kindex enable display
8847 @item enable display @var{dnums}@dots{}
8848 Enable display of item numbers @var{dnums}. It becomes effective once
8849 again in auto display of its expression, until you specify otherwise.
8850 Specify the numbers of the displays that you want affected with the
8851 command argument @var{dnums}. It can be a single display number, one
8852 of the numbers shown in the first field of the @samp{info display}
8853 display; or it could be a range of display numbers, as in @code{2-4}.
8856 Display the current values of the expressions on the list, just as is
8857 done when your program stops.
8859 @kindex info display
8861 Print the list of expressions previously set up to display
8862 automatically, each one with its item number, but without showing the
8863 values. This includes disabled expressions, which are marked as such.
8864 It also includes expressions which would not be displayed right now
8865 because they refer to automatic variables not currently available.
8868 @cindex display disabled out of scope
8869 If a display expression refers to local variables, then it does not make
8870 sense outside the lexical context for which it was set up. Such an
8871 expression is disabled when execution enters a context where one of its
8872 variables is not defined. For example, if you give the command
8873 @code{display last_char} while inside a function with an argument
8874 @code{last_char}, @value{GDBN} displays this argument while your program
8875 continues to stop inside that function. When it stops elsewhere---where
8876 there is no variable @code{last_char}---the display is disabled
8877 automatically. The next time your program stops where @code{last_char}
8878 is meaningful, you can enable the display expression once again.
8880 @node Print Settings
8881 @section Print Settings
8883 @cindex format options
8884 @cindex print settings
8885 @value{GDBN} provides the following ways to control how arrays, structures,
8886 and symbols are printed.
8889 These settings are useful for debugging programs in any language:
8893 @item set print address
8894 @itemx set print address on
8895 @cindex print/don't print memory addresses
8896 @value{GDBN} prints memory addresses showing the location of stack
8897 traces, structure values, pointer values, breakpoints, and so forth,
8898 even when it also displays the contents of those addresses. The default
8899 is @code{on}. For example, this is what a stack frame display looks like with
8900 @code{set print address on}:
8905 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8907 530 if (lquote != def_lquote)
8911 @item set print address off
8912 Do not print addresses when displaying their contents. For example,
8913 this is the same stack frame displayed with @code{set print address off}:
8917 (@value{GDBP}) set print addr off
8919 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8920 530 if (lquote != def_lquote)
8924 You can use @samp{set print address off} to eliminate all machine
8925 dependent displays from the @value{GDBN} interface. For example, with
8926 @code{print address off}, you should get the same text for backtraces on
8927 all machines---whether or not they involve pointer arguments.
8930 @item show print address
8931 Show whether or not addresses are to be printed.
8934 When @value{GDBN} prints a symbolic address, it normally prints the
8935 closest earlier symbol plus an offset. If that symbol does not uniquely
8936 identify the address (for example, it is a name whose scope is a single
8937 source file), you may need to clarify. One way to do this is with
8938 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8939 you can set @value{GDBN} to print the source file and line number when
8940 it prints a symbolic address:
8943 @item set print symbol-filename on
8944 @cindex source file and line of a symbol
8945 @cindex symbol, source file and line
8946 Tell @value{GDBN} to print the source file name and line number of a
8947 symbol in the symbolic form of an address.
8949 @item set print symbol-filename off
8950 Do not print source file name and line number of a symbol. This is the
8953 @item show print symbol-filename
8954 Show whether or not @value{GDBN} will print the source file name and
8955 line number of a symbol in the symbolic form of an address.
8958 Another situation where it is helpful to show symbol filenames and line
8959 numbers is when disassembling code; @value{GDBN} shows you the line
8960 number and source file that corresponds to each instruction.
8962 Also, you may wish to see the symbolic form only if the address being
8963 printed is reasonably close to the closest earlier symbol:
8966 @item set print max-symbolic-offset @var{max-offset}
8967 @itemx set print max-symbolic-offset unlimited
8968 @cindex maximum value for offset of closest symbol
8969 Tell @value{GDBN} to only display the symbolic form of an address if the
8970 offset between the closest earlier symbol and the address is less than
8971 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8972 to always print the symbolic form of an address if any symbol precedes
8973 it. Zero is equivalent to @code{unlimited}.
8975 @item show print max-symbolic-offset
8976 Ask how large the maximum offset is that @value{GDBN} prints in a
8980 @cindex wild pointer, interpreting
8981 @cindex pointer, finding referent
8982 If you have a pointer and you are not sure where it points, try
8983 @samp{set print symbol-filename on}. Then you can determine the name
8984 and source file location of the variable where it points, using
8985 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8986 For example, here @value{GDBN} shows that a variable @code{ptt} points
8987 at another variable @code{t}, defined in @file{hi2.c}:
8990 (@value{GDBP}) set print symbol-filename on
8991 (@value{GDBP}) p/a ptt
8992 $4 = 0xe008 <t in hi2.c>
8996 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8997 does not show the symbol name and filename of the referent, even with
8998 the appropriate @code{set print} options turned on.
9001 You can also enable @samp{/a}-like formatting all the time using
9002 @samp{set print symbol on}:
9005 @item set print symbol on
9006 Tell @value{GDBN} to print the symbol corresponding to an address, if
9009 @item set print symbol off
9010 Tell @value{GDBN} not to print the symbol corresponding to an
9011 address. In this mode, @value{GDBN} will still print the symbol
9012 corresponding to pointers to functions. This is the default.
9014 @item show print symbol
9015 Show whether @value{GDBN} will display the symbol corresponding to an
9019 Other settings control how different kinds of objects are printed:
9022 @item set print array
9023 @itemx set print array on
9024 @cindex pretty print arrays
9025 Pretty print arrays. This format is more convenient to read,
9026 but uses more space. The default is off.
9028 @item set print array off
9029 Return to compressed format for arrays.
9031 @item show print array
9032 Show whether compressed or pretty format is selected for displaying
9035 @cindex print array indexes
9036 @item set print array-indexes
9037 @itemx set print array-indexes on
9038 Print the index of each element when displaying arrays. May be more
9039 convenient to locate a given element in the array or quickly find the
9040 index of a given element in that printed array. The default is off.
9042 @item set print array-indexes off
9043 Stop printing element indexes when displaying arrays.
9045 @item show print array-indexes
9046 Show whether the index of each element is printed when displaying
9049 @item set print elements @var{number-of-elements}
9050 @itemx set print elements unlimited
9051 @cindex number of array elements to print
9052 @cindex limit on number of printed array elements
9053 Set a limit on how many elements of an array @value{GDBN} will print.
9054 If @value{GDBN} is printing a large array, it stops printing after it has
9055 printed the number of elements set by the @code{set print elements} command.
9056 This limit also applies to the display of strings.
9057 When @value{GDBN} starts, this limit is set to 200.
9058 Setting @var{number-of-elements} to @code{unlimited} or zero means
9059 that the number of elements to print is unlimited.
9061 @item show print elements
9062 Display the number of elements of a large array that @value{GDBN} will print.
9063 If the number is 0, then the printing is unlimited.
9065 @item set print frame-arguments @var{value}
9066 @kindex set print frame-arguments
9067 @cindex printing frame argument values
9068 @cindex print all frame argument values
9069 @cindex print frame argument values for scalars only
9070 @cindex do not print frame argument values
9071 This command allows to control how the values of arguments are printed
9072 when the debugger prints a frame (@pxref{Frames}). The possible
9077 The values of all arguments are printed.
9080 Print the value of an argument only if it is a scalar. The value of more
9081 complex arguments such as arrays, structures, unions, etc, is replaced
9082 by @code{@dots{}}. This is the default. Here is an example where
9083 only scalar arguments are shown:
9086 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9091 None of the argument values are printed. Instead, the value of each argument
9092 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9095 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9100 By default, only scalar arguments are printed. This command can be used
9101 to configure the debugger to print the value of all arguments, regardless
9102 of their type. However, it is often advantageous to not print the value
9103 of more complex parameters. For instance, it reduces the amount of
9104 information printed in each frame, making the backtrace more readable.
9105 Also, it improves performance when displaying Ada frames, because
9106 the computation of large arguments can sometimes be CPU-intensive,
9107 especially in large applications. Setting @code{print frame-arguments}
9108 to @code{scalars} (the default) or @code{none} avoids this computation,
9109 thus speeding up the display of each Ada frame.
9111 @item show print frame-arguments
9112 Show how the value of arguments should be displayed when printing a frame.
9114 @item set print raw frame-arguments on
9115 Print frame arguments in raw, non pretty-printed, form.
9117 @item set print raw frame-arguments off
9118 Print frame arguments in pretty-printed form, if there is a pretty-printer
9119 for the value (@pxref{Pretty Printing}),
9120 otherwise print the value in raw form.
9121 This is the default.
9123 @item show print raw frame-arguments
9124 Show whether to print frame arguments in raw form.
9126 @anchor{set print entry-values}
9127 @item set print entry-values @var{value}
9128 @kindex set print entry-values
9129 Set printing of frame argument values at function entry. In some cases
9130 @value{GDBN} can determine the value of function argument which was passed by
9131 the function caller, even if the value was modified inside the called function
9132 and therefore is different. With optimized code, the current value could be
9133 unavailable, but the entry value may still be known.
9135 The default value is @code{default} (see below for its description). Older
9136 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9137 this feature will behave in the @code{default} setting the same way as with the
9140 This functionality is currently supported only by DWARF 2 debugging format and
9141 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9142 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9145 The @var{value} parameter can be one of the following:
9149 Print only actual parameter values, never print values from function entry
9153 #0 different (val=6)
9154 #0 lost (val=<optimized out>)
9156 #0 invalid (val=<optimized out>)
9160 Print only parameter values from function entry point. The actual parameter
9161 values are never printed.
9163 #0 equal (val@@entry=5)
9164 #0 different (val@@entry=5)
9165 #0 lost (val@@entry=5)
9166 #0 born (val@@entry=<optimized out>)
9167 #0 invalid (val@@entry=<optimized out>)
9171 Print only parameter values from function entry point. If value from function
9172 entry point is not known while the actual value is known, print the actual
9173 value for such parameter.
9175 #0 equal (val@@entry=5)
9176 #0 different (val@@entry=5)
9177 #0 lost (val@@entry=5)
9179 #0 invalid (val@@entry=<optimized out>)
9183 Print actual parameter values. If actual parameter value is not known while
9184 value from function entry point is known, print the entry point value for such
9188 #0 different (val=6)
9189 #0 lost (val@@entry=5)
9191 #0 invalid (val=<optimized out>)
9195 Always print both the actual parameter value and its value from function entry
9196 point, even if values of one or both are not available due to compiler
9199 #0 equal (val=5, val@@entry=5)
9200 #0 different (val=6, val@@entry=5)
9201 #0 lost (val=<optimized out>, val@@entry=5)
9202 #0 born (val=10, val@@entry=<optimized out>)
9203 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9207 Print the actual parameter value if it is known and also its value from
9208 function entry point if it is known. If neither is known, print for the actual
9209 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9210 values are known and identical, print the shortened
9211 @code{param=param@@entry=VALUE} notation.
9213 #0 equal (val=val@@entry=5)
9214 #0 different (val=6, val@@entry=5)
9215 #0 lost (val@@entry=5)
9217 #0 invalid (val=<optimized out>)
9221 Always print the actual parameter value. Print also its value from function
9222 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9223 if both values are known and identical, print the shortened
9224 @code{param=param@@entry=VALUE} notation.
9226 #0 equal (val=val@@entry=5)
9227 #0 different (val=6, val@@entry=5)
9228 #0 lost (val=<optimized out>, val@@entry=5)
9230 #0 invalid (val=<optimized out>)
9234 For analysis messages on possible failures of frame argument values at function
9235 entry resolution see @ref{set debug entry-values}.
9237 @item show print entry-values
9238 Show the method being used for printing of frame argument values at function
9241 @item set print repeats @var{number-of-repeats}
9242 @itemx set print repeats unlimited
9243 @cindex repeated array elements
9244 Set the threshold for suppressing display of repeated array
9245 elements. When the number of consecutive identical elements of an
9246 array exceeds the threshold, @value{GDBN} prints the string
9247 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9248 identical repetitions, instead of displaying the identical elements
9249 themselves. Setting the threshold to @code{unlimited} or zero will
9250 cause all elements to be individually printed. The default threshold
9253 @item show print repeats
9254 Display the current threshold for printing repeated identical
9257 @item set print null-stop
9258 @cindex @sc{null} elements in arrays
9259 Cause @value{GDBN} to stop printing the characters of an array when the first
9260 @sc{null} is encountered. This is useful when large arrays actually
9261 contain only short strings.
9264 @item show print null-stop
9265 Show whether @value{GDBN} stops printing an array on the first
9266 @sc{null} character.
9268 @item set print pretty on
9269 @cindex print structures in indented form
9270 @cindex indentation in structure display
9271 Cause @value{GDBN} to print structures in an indented format with one member
9272 per line, like this:
9287 @item set print pretty off
9288 Cause @value{GDBN} to print structures in a compact format, like this:
9292 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9293 meat = 0x54 "Pork"@}
9298 This is the default format.
9300 @item show print pretty
9301 Show which format @value{GDBN} is using to print structures.
9303 @item set print sevenbit-strings on
9304 @cindex eight-bit characters in strings
9305 @cindex octal escapes in strings
9306 Print using only seven-bit characters; if this option is set,
9307 @value{GDBN} displays any eight-bit characters (in strings or
9308 character values) using the notation @code{\}@var{nnn}. This setting is
9309 best if you are working in English (@sc{ascii}) and you use the
9310 high-order bit of characters as a marker or ``meta'' bit.
9312 @item set print sevenbit-strings off
9313 Print full eight-bit characters. This allows the use of more
9314 international character sets, and is the default.
9316 @item show print sevenbit-strings
9317 Show whether or not @value{GDBN} is printing only seven-bit characters.
9319 @item set print union on
9320 @cindex unions in structures, printing
9321 Tell @value{GDBN} to print unions which are contained in structures
9322 and other unions. This is the default setting.
9324 @item set print union off
9325 Tell @value{GDBN} not to print unions which are contained in
9326 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9329 @item show print union
9330 Ask @value{GDBN} whether or not it will print unions which are contained in
9331 structures and other unions.
9333 For example, given the declarations
9336 typedef enum @{Tree, Bug@} Species;
9337 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9338 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9349 struct thing foo = @{Tree, @{Acorn@}@};
9353 with @code{set print union on} in effect @samp{p foo} would print
9356 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9360 and with @code{set print union off} in effect it would print
9363 $1 = @{it = Tree, form = @{...@}@}
9367 @code{set print union} affects programs written in C-like languages
9373 These settings are of interest when debugging C@t{++} programs:
9376 @cindex demangling C@t{++} names
9377 @item set print demangle
9378 @itemx set print demangle on
9379 Print C@t{++} names in their source form rather than in the encoded
9380 (``mangled'') form passed to the assembler and linker for type-safe
9381 linkage. The default is on.
9383 @item show print demangle
9384 Show whether C@t{++} names are printed in mangled or demangled form.
9386 @item set print asm-demangle
9387 @itemx set print asm-demangle on
9388 Print C@t{++} names in their source form rather than their mangled form, even
9389 in assembler code printouts such as instruction disassemblies.
9392 @item show print asm-demangle
9393 Show whether C@t{++} names in assembly listings are printed in mangled
9396 @cindex C@t{++} symbol decoding style
9397 @cindex symbol decoding style, C@t{++}
9398 @kindex set demangle-style
9399 @item set demangle-style @var{style}
9400 Choose among several encoding schemes used by different compilers to
9401 represent C@t{++} names. The choices for @var{style} are currently:
9405 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9406 This is the default.
9409 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9412 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9415 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9418 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9419 @strong{Warning:} this setting alone is not sufficient to allow
9420 debugging @code{cfront}-generated executables. @value{GDBN} would
9421 require further enhancement to permit that.
9424 If you omit @var{style}, you will see a list of possible formats.
9426 @item show demangle-style
9427 Display the encoding style currently in use for decoding C@t{++} symbols.
9429 @item set print object
9430 @itemx set print object on
9431 @cindex derived type of an object, printing
9432 @cindex display derived types
9433 When displaying a pointer to an object, identify the @emph{actual}
9434 (derived) type of the object rather than the @emph{declared} type, using
9435 the virtual function table. Note that the virtual function table is
9436 required---this feature can only work for objects that have run-time
9437 type identification; a single virtual method in the object's declared
9438 type is sufficient. Note that this setting is also taken into account when
9439 working with variable objects via MI (@pxref{GDB/MI}).
9441 @item set print object off
9442 Display only the declared type of objects, without reference to the
9443 virtual function table. This is the default setting.
9445 @item show print object
9446 Show whether actual, or declared, object types are displayed.
9448 @item set print static-members
9449 @itemx set print static-members on
9450 @cindex static members of C@t{++} objects
9451 Print static members when displaying a C@t{++} object. The default is on.
9453 @item set print static-members off
9454 Do not print static members when displaying a C@t{++} object.
9456 @item show print static-members
9457 Show whether C@t{++} static members are printed or not.
9459 @item set print pascal_static-members
9460 @itemx set print pascal_static-members on
9461 @cindex static members of Pascal objects
9462 @cindex Pascal objects, static members display
9463 Print static members when displaying a Pascal object. The default is on.
9465 @item set print pascal_static-members off
9466 Do not print static members when displaying a Pascal object.
9468 @item show print pascal_static-members
9469 Show whether Pascal static members are printed or not.
9471 @c These don't work with HP ANSI C++ yet.
9472 @item set print vtbl
9473 @itemx set print vtbl on
9474 @cindex pretty print C@t{++} virtual function tables
9475 @cindex virtual functions (C@t{++}) display
9476 @cindex VTBL display
9477 Pretty print C@t{++} virtual function tables. The default is off.
9478 (The @code{vtbl} commands do not work on programs compiled with the HP
9479 ANSI C@t{++} compiler (@code{aCC}).)
9481 @item set print vtbl off
9482 Do not pretty print C@t{++} virtual function tables.
9484 @item show print vtbl
9485 Show whether C@t{++} virtual function tables are pretty printed, or not.
9488 @node Pretty Printing
9489 @section Pretty Printing
9491 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9492 Python code. It greatly simplifies the display of complex objects. This
9493 mechanism works for both MI and the CLI.
9496 * Pretty-Printer Introduction:: Introduction to pretty-printers
9497 * Pretty-Printer Example:: An example pretty-printer
9498 * Pretty-Printer Commands:: Pretty-printer commands
9501 @node Pretty-Printer Introduction
9502 @subsection Pretty-Printer Introduction
9504 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9505 registered for the value. If there is then @value{GDBN} invokes the
9506 pretty-printer to print the value. Otherwise the value is printed normally.
9508 Pretty-printers are normally named. This makes them easy to manage.
9509 The @samp{info pretty-printer} command will list all the installed
9510 pretty-printers with their names.
9511 If a pretty-printer can handle multiple data types, then its
9512 @dfn{subprinters} are the printers for the individual data types.
9513 Each such subprinter has its own name.
9514 The format of the name is @var{printer-name};@var{subprinter-name}.
9516 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9517 Typically they are automatically loaded and registered when the corresponding
9518 debug information is loaded, thus making them available without having to
9519 do anything special.
9521 There are three places where a pretty-printer can be registered.
9525 Pretty-printers registered globally are available when debugging
9529 Pretty-printers registered with a program space are available only
9530 when debugging that program.
9531 @xref{Progspaces In Python}, for more details on program spaces in Python.
9534 Pretty-printers registered with an objfile are loaded and unloaded
9535 with the corresponding objfile (e.g., shared library).
9536 @xref{Objfiles In Python}, for more details on objfiles in Python.
9539 @xref{Selecting Pretty-Printers}, for further information on how
9540 pretty-printers are selected,
9542 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9545 @node Pretty-Printer Example
9546 @subsection Pretty-Printer Example
9548 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9551 (@value{GDBP}) print s
9553 static npos = 4294967295,
9555 <std::allocator<char>> = @{
9556 <__gnu_cxx::new_allocator<char>> = @{
9557 <No data fields>@}, <No data fields>
9559 members of std::basic_string<char, std::char_traits<char>,
9560 std::allocator<char> >::_Alloc_hider:
9561 _M_p = 0x804a014 "abcd"
9566 With a pretty-printer for @code{std::string} only the contents are printed:
9569 (@value{GDBP}) print s
9573 @node Pretty-Printer Commands
9574 @subsection Pretty-Printer Commands
9575 @cindex pretty-printer commands
9578 @kindex info pretty-printer
9579 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9580 Print the list of installed pretty-printers.
9581 This includes disabled pretty-printers, which are marked as such.
9583 @var{object-regexp} is a regular expression matching the objects
9584 whose pretty-printers to list.
9585 Objects can be @code{global}, the program space's file
9586 (@pxref{Progspaces In Python}),
9587 and the object files within that program space (@pxref{Objfiles In Python}).
9588 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9589 looks up a printer from these three objects.
9591 @var{name-regexp} is a regular expression matching the name of the printers
9594 @kindex disable pretty-printer
9595 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9596 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9597 A disabled pretty-printer is not forgotten, it may be enabled again later.
9599 @kindex enable pretty-printer
9600 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9601 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9606 Suppose we have three pretty-printers installed: one from library1.so
9607 named @code{foo} that prints objects of type @code{foo}, and
9608 another from library2.so named @code{bar} that prints two types of objects,
9609 @code{bar1} and @code{bar2}.
9612 (gdb) info pretty-printer
9619 (gdb) info pretty-printer library2
9624 (gdb) disable pretty-printer library1
9626 2 of 3 printers enabled
9627 (gdb) info pretty-printer
9634 (gdb) disable pretty-printer library2 bar:bar1
9636 1 of 3 printers enabled
9637 (gdb) info pretty-printer library2
9644 (gdb) disable pretty-printer library2 bar
9646 0 of 3 printers enabled
9647 (gdb) info pretty-printer library2
9656 Note that for @code{bar} the entire printer can be disabled,
9657 as can each individual subprinter.
9660 @section Value History
9662 @cindex value history
9663 @cindex history of values printed by @value{GDBN}
9664 Values printed by the @code{print} command are saved in the @value{GDBN}
9665 @dfn{value history}. This allows you to refer to them in other expressions.
9666 Values are kept until the symbol table is re-read or discarded
9667 (for example with the @code{file} or @code{symbol-file} commands).
9668 When the symbol table changes, the value history is discarded,
9669 since the values may contain pointers back to the types defined in the
9674 @cindex history number
9675 The values printed are given @dfn{history numbers} by which you can
9676 refer to them. These are successive integers starting with one.
9677 @code{print} shows you the history number assigned to a value by
9678 printing @samp{$@var{num} = } before the value; here @var{num} is the
9681 To refer to any previous value, use @samp{$} followed by the value's
9682 history number. The way @code{print} labels its output is designed to
9683 remind you of this. Just @code{$} refers to the most recent value in
9684 the history, and @code{$$} refers to the value before that.
9685 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9686 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9687 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9689 For example, suppose you have just printed a pointer to a structure and
9690 want to see the contents of the structure. It suffices to type
9696 If you have a chain of structures where the component @code{next} points
9697 to the next one, you can print the contents of the next one with this:
9704 You can print successive links in the chain by repeating this
9705 command---which you can do by just typing @key{RET}.
9707 Note that the history records values, not expressions. If the value of
9708 @code{x} is 4 and you type these commands:
9716 then the value recorded in the value history by the @code{print} command
9717 remains 4 even though the value of @code{x} has changed.
9722 Print the last ten values in the value history, with their item numbers.
9723 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9724 values} does not change the history.
9726 @item show values @var{n}
9727 Print ten history values centered on history item number @var{n}.
9730 Print ten history values just after the values last printed. If no more
9731 values are available, @code{show values +} produces no display.
9734 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9735 same effect as @samp{show values +}.
9737 @node Convenience Vars
9738 @section Convenience Variables
9740 @cindex convenience variables
9741 @cindex user-defined variables
9742 @value{GDBN} provides @dfn{convenience variables} that you can use within
9743 @value{GDBN} to hold on to a value and refer to it later. These variables
9744 exist entirely within @value{GDBN}; they are not part of your program, and
9745 setting a convenience variable has no direct effect on further execution
9746 of your program. That is why you can use them freely.
9748 Convenience variables are prefixed with @samp{$}. Any name preceded by
9749 @samp{$} can be used for a convenience variable, unless it is one of
9750 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9751 (Value history references, in contrast, are @emph{numbers} preceded
9752 by @samp{$}. @xref{Value History, ,Value History}.)
9754 You can save a value in a convenience variable with an assignment
9755 expression, just as you would set a variable in your program.
9759 set $foo = *object_ptr
9763 would save in @code{$foo} the value contained in the object pointed to by
9766 Using a convenience variable for the first time creates it, but its
9767 value is @code{void} until you assign a new value. You can alter the
9768 value with another assignment at any time.
9770 Convenience variables have no fixed types. You can assign a convenience
9771 variable any type of value, including structures and arrays, even if
9772 that variable already has a value of a different type. The convenience
9773 variable, when used as an expression, has the type of its current value.
9776 @kindex show convenience
9777 @cindex show all user variables and functions
9778 @item show convenience
9779 Print a list of convenience variables used so far, and their values,
9780 as well as a list of the convenience functions.
9781 Abbreviated @code{show conv}.
9783 @kindex init-if-undefined
9784 @cindex convenience variables, initializing
9785 @item init-if-undefined $@var{variable} = @var{expression}
9786 Set a convenience variable if it has not already been set. This is useful
9787 for user-defined commands that keep some state. It is similar, in concept,
9788 to using local static variables with initializers in C (except that
9789 convenience variables are global). It can also be used to allow users to
9790 override default values used in a command script.
9792 If the variable is already defined then the expression is not evaluated so
9793 any side-effects do not occur.
9796 One of the ways to use a convenience variable is as a counter to be
9797 incremented or a pointer to be advanced. For example, to print
9798 a field from successive elements of an array of structures:
9802 print bar[$i++]->contents
9806 Repeat that command by typing @key{RET}.
9808 Some convenience variables are created automatically by @value{GDBN} and given
9809 values likely to be useful.
9812 @vindex $_@r{, convenience variable}
9814 The variable @code{$_} is automatically set by the @code{x} command to
9815 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9816 commands which provide a default address for @code{x} to examine also
9817 set @code{$_} to that address; these commands include @code{info line}
9818 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9819 except when set by the @code{x} command, in which case it is a pointer
9820 to the type of @code{$__}.
9822 @vindex $__@r{, convenience variable}
9824 The variable @code{$__} is automatically set by the @code{x} command
9825 to the value found in the last address examined. Its type is chosen
9826 to match the format in which the data was printed.
9829 @vindex $_exitcode@r{, convenience variable}
9830 When the program being debugged terminates normally, @value{GDBN}
9831 automatically sets this variable to the exit code of the program, and
9832 resets @code{$_exitsignal} to @code{void}.
9835 @vindex $_exitsignal@r{, convenience variable}
9836 When the program being debugged dies due to an uncaught signal,
9837 @value{GDBN} automatically sets this variable to that signal's number,
9838 and resets @code{$_exitcode} to @code{void}.
9840 To distinguish between whether the program being debugged has exited
9841 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9842 @code{$_exitsignal} is not @code{void}), the convenience function
9843 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9844 Functions}). For example, considering the following source code:
9850 main (int argc, char *argv[])
9857 A valid way of telling whether the program being debugged has exited
9858 or signalled would be:
9861 (@value{GDBP}) define has_exited_or_signalled
9862 Type commands for definition of ``has_exited_or_signalled''.
9863 End with a line saying just ``end''.
9864 >if $_isvoid ($_exitsignal)
9865 >echo The program has exited\n
9867 >echo The program has signalled\n
9873 Program terminated with signal SIGALRM, Alarm clock.
9874 The program no longer exists.
9875 (@value{GDBP}) has_exited_or_signalled
9876 The program has signalled
9879 As can be seen, @value{GDBN} correctly informs that the program being
9880 debugged has signalled, since it calls @code{raise} and raises a
9881 @code{SIGALRM} signal. If the program being debugged had not called
9882 @code{raise}, then @value{GDBN} would report a normal exit:
9885 (@value{GDBP}) has_exited_or_signalled
9886 The program has exited
9890 The variable @code{$_exception} is set to the exception object being
9891 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9894 @itemx $_probe_arg0@dots{}$_probe_arg11
9895 Arguments to a static probe. @xref{Static Probe Points}.
9898 @vindex $_sdata@r{, inspect, convenience variable}
9899 The variable @code{$_sdata} contains extra collected static tracepoint
9900 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9901 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9902 if extra static tracepoint data has not been collected.
9905 @vindex $_siginfo@r{, convenience variable}
9906 The variable @code{$_siginfo} contains extra signal information
9907 (@pxref{extra signal information}). Note that @code{$_siginfo}
9908 could be empty, if the application has not yet received any signals.
9909 For example, it will be empty before you execute the @code{run} command.
9912 @vindex $_tlb@r{, convenience variable}
9913 The variable @code{$_tlb} is automatically set when debugging
9914 applications running on MS-Windows in native mode or connected to
9915 gdbserver that supports the @code{qGetTIBAddr} request.
9916 @xref{General Query Packets}.
9917 This variable contains the address of the thread information block.
9921 On HP-UX systems, if you refer to a function or variable name that
9922 begins with a dollar sign, @value{GDBN} searches for a user or system
9923 name first, before it searches for a convenience variable.
9925 @node Convenience Funs
9926 @section Convenience Functions
9928 @cindex convenience functions
9929 @value{GDBN} also supplies some @dfn{convenience functions}. These
9930 have a syntax similar to convenience variables. A convenience
9931 function can be used in an expression just like an ordinary function;
9932 however, a convenience function is implemented internally to
9935 These functions do not require @value{GDBN} to be configured with
9936 @code{Python} support, which means that they are always available.
9940 @item $_isvoid (@var{expr})
9941 @findex $_isvoid@r{, convenience function}
9942 Return one if the expression @var{expr} is @code{void}. Otherwise it
9945 A @code{void} expression is an expression where the type of the result
9946 is @code{void}. For example, you can examine a convenience variable
9947 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9951 (@value{GDBP}) print $_exitcode
9953 (@value{GDBP}) print $_isvoid ($_exitcode)
9956 Starting program: ./a.out
9957 [Inferior 1 (process 29572) exited normally]
9958 (@value{GDBP}) print $_exitcode
9960 (@value{GDBP}) print $_isvoid ($_exitcode)
9964 In the example above, we used @code{$_isvoid} to check whether
9965 @code{$_exitcode} is @code{void} before and after the execution of the
9966 program being debugged. Before the execution there is no exit code to
9967 be examined, therefore @code{$_exitcode} is @code{void}. After the
9968 execution the program being debugged returned zero, therefore
9969 @code{$_exitcode} is zero, which means that it is not @code{void}
9972 The @code{void} expression can also be a call of a function from the
9973 program being debugged. For example, given the following function:
9982 The result of calling it inside @value{GDBN} is @code{void}:
9985 (@value{GDBP}) print foo ()
9987 (@value{GDBP}) print $_isvoid (foo ())
9989 (@value{GDBP}) set $v = foo ()
9990 (@value{GDBP}) print $v
9992 (@value{GDBP}) print $_isvoid ($v)
9998 These functions require @value{GDBN} to be configured with
9999 @code{Python} support.
10003 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10004 @findex $_memeq@r{, convenience function}
10005 Returns one if the @var{length} bytes at the addresses given by
10006 @var{buf1} and @var{buf2} are equal.
10007 Otherwise it returns zero.
10009 @item $_regex(@var{str}, @var{regex})
10010 @findex $_regex@r{, convenience function}
10011 Returns one if the string @var{str} matches the regular expression
10012 @var{regex}. Otherwise it returns zero.
10013 The syntax of the regular expression is that specified by @code{Python}'s
10014 regular expression support.
10016 @item $_streq(@var{str1}, @var{str2})
10017 @findex $_streq@r{, convenience function}
10018 Returns one if the strings @var{str1} and @var{str2} are equal.
10019 Otherwise it returns zero.
10021 @item $_strlen(@var{str})
10022 @findex $_strlen@r{, convenience function}
10023 Returns the length of string @var{str}.
10027 @value{GDBN} provides the ability to list and get help on
10028 convenience functions.
10031 @item help function
10032 @kindex help function
10033 @cindex show all convenience functions
10034 Print a list of all convenience functions.
10041 You can refer to machine register contents, in expressions, as variables
10042 with names starting with @samp{$}. The names of registers are different
10043 for each machine; use @code{info registers} to see the names used on
10047 @kindex info registers
10048 @item info registers
10049 Print the names and values of all registers except floating-point
10050 and vector registers (in the selected stack frame).
10052 @kindex info all-registers
10053 @cindex floating point registers
10054 @item info all-registers
10055 Print the names and values of all registers, including floating-point
10056 and vector registers (in the selected stack frame).
10058 @item info registers @var{regname} @dots{}
10059 Print the @dfn{relativized} value of each specified register @var{regname}.
10060 As discussed in detail below, register values are normally relative to
10061 the selected stack frame. @var{regname} may be any register name valid on
10062 the machine you are using, with or without the initial @samp{$}.
10065 @cindex stack pointer register
10066 @cindex program counter register
10067 @cindex process status register
10068 @cindex frame pointer register
10069 @cindex standard registers
10070 @value{GDBN} has four ``standard'' register names that are available (in
10071 expressions) on most machines---whenever they do not conflict with an
10072 architecture's canonical mnemonics for registers. The register names
10073 @code{$pc} and @code{$sp} are used for the program counter register and
10074 the stack pointer. @code{$fp} is used for a register that contains a
10075 pointer to the current stack frame, and @code{$ps} is used for a
10076 register that contains the processor status. For example,
10077 you could print the program counter in hex with
10084 or print the instruction to be executed next with
10091 or add four to the stack pointer@footnote{This is a way of removing
10092 one word from the stack, on machines where stacks grow downward in
10093 memory (most machines, nowadays). This assumes that the innermost
10094 stack frame is selected; setting @code{$sp} is not allowed when other
10095 stack frames are selected. To pop entire frames off the stack,
10096 regardless of machine architecture, use @code{return};
10097 see @ref{Returning, ,Returning from a Function}.} with
10103 Whenever possible, these four standard register names are available on
10104 your machine even though the machine has different canonical mnemonics,
10105 so long as there is no conflict. The @code{info registers} command
10106 shows the canonical names. For example, on the SPARC, @code{info
10107 registers} displays the processor status register as @code{$psr} but you
10108 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10109 is an alias for the @sc{eflags} register.
10111 @value{GDBN} always considers the contents of an ordinary register as an
10112 integer when the register is examined in this way. Some machines have
10113 special registers which can hold nothing but floating point; these
10114 registers are considered to have floating point values. There is no way
10115 to refer to the contents of an ordinary register as floating point value
10116 (although you can @emph{print} it as a floating point value with
10117 @samp{print/f $@var{regname}}).
10119 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10120 means that the data format in which the register contents are saved by
10121 the operating system is not the same one that your program normally
10122 sees. For example, the registers of the 68881 floating point
10123 coprocessor are always saved in ``extended'' (raw) format, but all C
10124 programs expect to work with ``double'' (virtual) format. In such
10125 cases, @value{GDBN} normally works with the virtual format only (the format
10126 that makes sense for your program), but the @code{info registers} command
10127 prints the data in both formats.
10129 @cindex SSE registers (x86)
10130 @cindex MMX registers (x86)
10131 Some machines have special registers whose contents can be interpreted
10132 in several different ways. For example, modern x86-based machines
10133 have SSE and MMX registers that can hold several values packed
10134 together in several different formats. @value{GDBN} refers to such
10135 registers in @code{struct} notation:
10138 (@value{GDBP}) print $xmm1
10140 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10141 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10142 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10143 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10144 v4_int32 = @{0, 20657912, 11, 13@},
10145 v2_int64 = @{88725056443645952, 55834574859@},
10146 uint128 = 0x0000000d0000000b013b36f800000000
10151 To set values of such registers, you need to tell @value{GDBN} which
10152 view of the register you wish to change, as if you were assigning
10153 value to a @code{struct} member:
10156 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10159 Normally, register values are relative to the selected stack frame
10160 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10161 value that the register would contain if all stack frames farther in
10162 were exited and their saved registers restored. In order to see the
10163 true contents of hardware registers, you must select the innermost
10164 frame (with @samp{frame 0}).
10166 @cindex caller-saved registers
10167 @cindex call-clobbered registers
10168 @cindex volatile registers
10169 @cindex <not saved> values
10170 Usually ABIs reserve some registers as not needed to be saved by the
10171 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10172 registers). It may therefore not be possible for @value{GDBN} to know
10173 the value a register had before the call (in other words, in the outer
10174 frame), if the register value has since been changed by the callee.
10175 @value{GDBN} tries to deduce where the inner frame saved
10176 (``callee-saved'') registers, from the debug info, unwind info, or the
10177 machine code generated by your compiler. If some register is not
10178 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10179 its own knowledge of the ABI, or because the debug/unwind info
10180 explicitly says the register's value is undefined), @value{GDBN}
10181 displays @w{@samp{<not saved>}} as the register's value. With targets
10182 that @value{GDBN} has no knowledge of the register saving convention,
10183 if a register was not saved by the callee, then its value and location
10184 in the outer frame are assumed to be the same of the inner frame.
10185 This is usually harmless, because if the register is call-clobbered,
10186 the caller either does not care what is in the register after the
10187 call, or has code to restore the value that it does care about. Note,
10188 however, that if you change such a register in the outer frame, you
10189 may also be affecting the inner frame. Also, the more ``outer'' the
10190 frame is you're looking at, the more likely a call-clobbered
10191 register's value is to be wrong, in the sense that it doesn't actually
10192 represent the value the register had just before the call.
10194 @node Floating Point Hardware
10195 @section Floating Point Hardware
10196 @cindex floating point
10198 Depending on the configuration, @value{GDBN} may be able to give
10199 you more information about the status of the floating point hardware.
10204 Display hardware-dependent information about the floating
10205 point unit. The exact contents and layout vary depending on the
10206 floating point chip. Currently, @samp{info float} is supported on
10207 the ARM and x86 machines.
10211 @section Vector Unit
10212 @cindex vector unit
10214 Depending on the configuration, @value{GDBN} may be able to give you
10215 more information about the status of the vector unit.
10218 @kindex info vector
10220 Display information about the vector unit. The exact contents and
10221 layout vary depending on the hardware.
10224 @node OS Information
10225 @section Operating System Auxiliary Information
10226 @cindex OS information
10228 @value{GDBN} provides interfaces to useful OS facilities that can help
10229 you debug your program.
10231 @cindex auxiliary vector
10232 @cindex vector, auxiliary
10233 Some operating systems supply an @dfn{auxiliary vector} to programs at
10234 startup. This is akin to the arguments and environment that you
10235 specify for a program, but contains a system-dependent variety of
10236 binary values that tell system libraries important details about the
10237 hardware, operating system, and process. Each value's purpose is
10238 identified by an integer tag; the meanings are well-known but system-specific.
10239 Depending on the configuration and operating system facilities,
10240 @value{GDBN} may be able to show you this information. For remote
10241 targets, this functionality may further depend on the remote stub's
10242 support of the @samp{qXfer:auxv:read} packet, see
10243 @ref{qXfer auxiliary vector read}.
10248 Display the auxiliary vector of the inferior, which can be either a
10249 live process or a core dump file. @value{GDBN} prints each tag value
10250 numerically, and also shows names and text descriptions for recognized
10251 tags. Some values in the vector are numbers, some bit masks, and some
10252 pointers to strings or other data. @value{GDBN} displays each value in the
10253 most appropriate form for a recognized tag, and in hexadecimal for
10254 an unrecognized tag.
10257 On some targets, @value{GDBN} can access operating system-specific
10258 information and show it to you. The types of information available
10259 will differ depending on the type of operating system running on the
10260 target. The mechanism used to fetch the data is described in
10261 @ref{Operating System Information}. For remote targets, this
10262 functionality depends on the remote stub's support of the
10263 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10267 @item info os @var{infotype}
10269 Display OS information of the requested type.
10271 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10273 @anchor{linux info os infotypes}
10275 @kindex info os processes
10277 Display the list of processes on the target. For each process,
10278 @value{GDBN} prints the process identifier, the name of the user, the
10279 command corresponding to the process, and the list of processor cores
10280 that the process is currently running on. (To understand what these
10281 properties mean, for this and the following info types, please consult
10282 the general @sc{gnu}/Linux documentation.)
10284 @kindex info os procgroups
10286 Display the list of process groups on the target. For each process,
10287 @value{GDBN} prints the identifier of the process group that it belongs
10288 to, the command corresponding to the process group leader, the process
10289 identifier, and the command line of the process. The list is sorted
10290 first by the process group identifier, then by the process identifier,
10291 so that processes belonging to the same process group are grouped together
10292 and the process group leader is listed first.
10294 @kindex info os threads
10296 Display the list of threads running on the target. For each thread,
10297 @value{GDBN} prints the identifier of the process that the thread
10298 belongs to, the command of the process, the thread identifier, and the
10299 processor core that it is currently running on. The main thread of a
10300 process is not listed.
10302 @kindex info os files
10304 Display the list of open file descriptors on the target. For each
10305 file descriptor, @value{GDBN} prints the identifier of the process
10306 owning the descriptor, the command of the owning process, the value
10307 of the descriptor, and the target of the descriptor.
10309 @kindex info os sockets
10311 Display the list of Internet-domain sockets on the target. For each
10312 socket, @value{GDBN} prints the address and port of the local and
10313 remote endpoints, the current state of the connection, the creator of
10314 the socket, the IP address family of the socket, and the type of the
10317 @kindex info os shm
10319 Display the list of all System V shared-memory regions on the target.
10320 For each shared-memory region, @value{GDBN} prints the region key,
10321 the shared-memory identifier, the access permissions, the size of the
10322 region, the process that created the region, the process that last
10323 attached to or detached from the region, the current number of live
10324 attaches to the region, and the times at which the region was last
10325 attached to, detach from, and changed.
10327 @kindex info os semaphores
10329 Display the list of all System V semaphore sets on the target. For each
10330 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10331 set identifier, the access permissions, the number of semaphores in the
10332 set, the user and group of the owner and creator of the semaphore set,
10333 and the times at which the semaphore set was operated upon and changed.
10335 @kindex info os msg
10337 Display the list of all System V message queues on the target. For each
10338 message queue, @value{GDBN} prints the message queue key, the message
10339 queue identifier, the access permissions, the current number of bytes
10340 on the queue, the current number of messages on the queue, the processes
10341 that last sent and received a message on the queue, the user and group
10342 of the owner and creator of the message queue, the times at which a
10343 message was last sent and received on the queue, and the time at which
10344 the message queue was last changed.
10346 @kindex info os modules
10348 Display the list of all loaded kernel modules on the target. For each
10349 module, @value{GDBN} prints the module name, the size of the module in
10350 bytes, the number of times the module is used, the dependencies of the
10351 module, the status of the module, and the address of the loaded module
10356 If @var{infotype} is omitted, then list the possible values for
10357 @var{infotype} and the kind of OS information available for each
10358 @var{infotype}. If the target does not return a list of possible
10359 types, this command will report an error.
10362 @node Memory Region Attributes
10363 @section Memory Region Attributes
10364 @cindex memory region attributes
10366 @dfn{Memory region attributes} allow you to describe special handling
10367 required by regions of your target's memory. @value{GDBN} uses
10368 attributes to determine whether to allow certain types of memory
10369 accesses; whether to use specific width accesses; and whether to cache
10370 target memory. By default the description of memory regions is
10371 fetched from the target (if the current target supports this), but the
10372 user can override the fetched regions.
10374 Defined memory regions can be individually enabled and disabled. When a
10375 memory region is disabled, @value{GDBN} uses the default attributes when
10376 accessing memory in that region. Similarly, if no memory regions have
10377 been defined, @value{GDBN} uses the default attributes when accessing
10380 When a memory region is defined, it is given a number to identify it;
10381 to enable, disable, or remove a memory region, you specify that number.
10385 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10386 Define a memory region bounded by @var{lower} and @var{upper} with
10387 attributes @var{attributes}@dots{}, and add it to the list of regions
10388 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10389 case: it is treated as the target's maximum memory address.
10390 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10393 Discard any user changes to the memory regions and use target-supplied
10394 regions, if available, or no regions if the target does not support.
10397 @item delete mem @var{nums}@dots{}
10398 Remove memory regions @var{nums}@dots{} from the list of regions
10399 monitored by @value{GDBN}.
10401 @kindex disable mem
10402 @item disable mem @var{nums}@dots{}
10403 Disable monitoring of memory regions @var{nums}@dots{}.
10404 A disabled memory region is not forgotten.
10405 It may be enabled again later.
10408 @item enable mem @var{nums}@dots{}
10409 Enable monitoring of memory regions @var{nums}@dots{}.
10413 Print a table of all defined memory regions, with the following columns
10417 @item Memory Region Number
10418 @item Enabled or Disabled.
10419 Enabled memory regions are marked with @samp{y}.
10420 Disabled memory regions are marked with @samp{n}.
10423 The address defining the inclusive lower bound of the memory region.
10426 The address defining the exclusive upper bound of the memory region.
10429 The list of attributes set for this memory region.
10434 @subsection Attributes
10436 @subsubsection Memory Access Mode
10437 The access mode attributes set whether @value{GDBN} may make read or
10438 write accesses to a memory region.
10440 While these attributes prevent @value{GDBN} from performing invalid
10441 memory accesses, they do nothing to prevent the target system, I/O DMA,
10442 etc.@: from accessing memory.
10446 Memory is read only.
10448 Memory is write only.
10450 Memory is read/write. This is the default.
10453 @subsubsection Memory Access Size
10454 The access size attribute tells @value{GDBN} to use specific sized
10455 accesses in the memory region. Often memory mapped device registers
10456 require specific sized accesses. If no access size attribute is
10457 specified, @value{GDBN} may use accesses of any size.
10461 Use 8 bit memory accesses.
10463 Use 16 bit memory accesses.
10465 Use 32 bit memory accesses.
10467 Use 64 bit memory accesses.
10470 @c @subsubsection Hardware/Software Breakpoints
10471 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10472 @c will use hardware or software breakpoints for the internal breakpoints
10473 @c used by the step, next, finish, until, etc. commands.
10477 @c Always use hardware breakpoints
10478 @c @item swbreak (default)
10481 @subsubsection Data Cache
10482 The data cache attributes set whether @value{GDBN} will cache target
10483 memory. While this generally improves performance by reducing debug
10484 protocol overhead, it can lead to incorrect results because @value{GDBN}
10485 does not know about volatile variables or memory mapped device
10490 Enable @value{GDBN} to cache target memory.
10492 Disable @value{GDBN} from caching target memory. This is the default.
10495 @subsection Memory Access Checking
10496 @value{GDBN} can be instructed to refuse accesses to memory that is
10497 not explicitly described. This can be useful if accessing such
10498 regions has undesired effects for a specific target, or to provide
10499 better error checking. The following commands control this behaviour.
10502 @kindex set mem inaccessible-by-default
10503 @item set mem inaccessible-by-default [on|off]
10504 If @code{on} is specified, make @value{GDBN} treat memory not
10505 explicitly described by the memory ranges as non-existent and refuse accesses
10506 to such memory. The checks are only performed if there's at least one
10507 memory range defined. If @code{off} is specified, make @value{GDBN}
10508 treat the memory not explicitly described by the memory ranges as RAM.
10509 The default value is @code{on}.
10510 @kindex show mem inaccessible-by-default
10511 @item show mem inaccessible-by-default
10512 Show the current handling of accesses to unknown memory.
10516 @c @subsubsection Memory Write Verification
10517 @c The memory write verification attributes set whether @value{GDBN}
10518 @c will re-reads data after each write to verify the write was successful.
10522 @c @item noverify (default)
10525 @node Dump/Restore Files
10526 @section Copy Between Memory and a File
10527 @cindex dump/restore files
10528 @cindex append data to a file
10529 @cindex dump data to a file
10530 @cindex restore data from a file
10532 You can use the commands @code{dump}, @code{append}, and
10533 @code{restore} to copy data between target memory and a file. The
10534 @code{dump} and @code{append} commands write data to a file, and the
10535 @code{restore} command reads data from a file back into the inferior's
10536 memory. Files may be in binary, Motorola S-record, Intel hex, or
10537 Tektronix Hex format; however, @value{GDBN} can only append to binary
10543 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10544 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10545 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10546 or the value of @var{expr}, to @var{filename} in the given format.
10548 The @var{format} parameter may be any one of:
10555 Motorola S-record format.
10557 Tektronix Hex format.
10560 @value{GDBN} uses the same definitions of these formats as the
10561 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10562 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10566 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10567 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10568 Append the contents of memory from @var{start_addr} to @var{end_addr},
10569 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10570 (@value{GDBN} can only append data to files in raw binary form.)
10573 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10574 Restore the contents of file @var{filename} into memory. The
10575 @code{restore} command can automatically recognize any known @sc{bfd}
10576 file format, except for raw binary. To restore a raw binary file you
10577 must specify the optional keyword @code{binary} after the filename.
10579 If @var{bias} is non-zero, its value will be added to the addresses
10580 contained in the file. Binary files always start at address zero, so
10581 they will be restored at address @var{bias}. Other bfd files have
10582 a built-in location; they will be restored at offset @var{bias}
10583 from that location.
10585 If @var{start} and/or @var{end} are non-zero, then only data between
10586 file offset @var{start} and file offset @var{end} will be restored.
10587 These offsets are relative to the addresses in the file, before
10588 the @var{bias} argument is applied.
10592 @node Core File Generation
10593 @section How to Produce a Core File from Your Program
10594 @cindex dump core from inferior
10596 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10597 image of a running process and its process status (register values
10598 etc.). Its primary use is post-mortem debugging of a program that
10599 crashed while it ran outside a debugger. A program that crashes
10600 automatically produces a core file, unless this feature is disabled by
10601 the user. @xref{Files}, for information on invoking @value{GDBN} in
10602 the post-mortem debugging mode.
10604 Occasionally, you may wish to produce a core file of the program you
10605 are debugging in order to preserve a snapshot of its state.
10606 @value{GDBN} has a special command for that.
10610 @kindex generate-core-file
10611 @item generate-core-file [@var{file}]
10612 @itemx gcore [@var{file}]
10613 Produce a core dump of the inferior process. The optional argument
10614 @var{file} specifies the file name where to put the core dump. If not
10615 specified, the file name defaults to @file{core.@var{pid}}, where
10616 @var{pid} is the inferior process ID.
10618 Note that this command is implemented only for some systems (as of
10619 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10622 @node Character Sets
10623 @section Character Sets
10624 @cindex character sets
10626 @cindex translating between character sets
10627 @cindex host character set
10628 @cindex target character set
10630 If the program you are debugging uses a different character set to
10631 represent characters and strings than the one @value{GDBN} uses itself,
10632 @value{GDBN} can automatically translate between the character sets for
10633 you. The character set @value{GDBN} uses we call the @dfn{host
10634 character set}; the one the inferior program uses we call the
10635 @dfn{target character set}.
10637 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10638 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10639 remote protocol (@pxref{Remote Debugging}) to debug a program
10640 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10641 then the host character set is Latin-1, and the target character set is
10642 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10643 target-charset EBCDIC-US}, then @value{GDBN} translates between
10644 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10645 character and string literals in expressions.
10647 @value{GDBN} has no way to automatically recognize which character set
10648 the inferior program uses; you must tell it, using the @code{set
10649 target-charset} command, described below.
10651 Here are the commands for controlling @value{GDBN}'s character set
10655 @item set target-charset @var{charset}
10656 @kindex set target-charset
10657 Set the current target character set to @var{charset}. To display the
10658 list of supported target character sets, type
10659 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10661 @item set host-charset @var{charset}
10662 @kindex set host-charset
10663 Set the current host character set to @var{charset}.
10665 By default, @value{GDBN} uses a host character set appropriate to the
10666 system it is running on; you can override that default using the
10667 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10668 automatically determine the appropriate host character set. In this
10669 case, @value{GDBN} uses @samp{UTF-8}.
10671 @value{GDBN} can only use certain character sets as its host character
10672 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10673 @value{GDBN} will list the host character sets it supports.
10675 @item set charset @var{charset}
10676 @kindex set charset
10677 Set the current host and target character sets to @var{charset}. As
10678 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10679 @value{GDBN} will list the names of the character sets that can be used
10680 for both host and target.
10683 @kindex show charset
10684 Show the names of the current host and target character sets.
10686 @item show host-charset
10687 @kindex show host-charset
10688 Show the name of the current host character set.
10690 @item show target-charset
10691 @kindex show target-charset
10692 Show the name of the current target character set.
10694 @item set target-wide-charset @var{charset}
10695 @kindex set target-wide-charset
10696 Set the current target's wide character set to @var{charset}. This is
10697 the character set used by the target's @code{wchar_t} type. To
10698 display the list of supported wide character sets, type
10699 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10701 @item show target-wide-charset
10702 @kindex show target-wide-charset
10703 Show the name of the current target's wide character set.
10706 Here is an example of @value{GDBN}'s character set support in action.
10707 Assume that the following source code has been placed in the file
10708 @file{charset-test.c}:
10714 = @{72, 101, 108, 108, 111, 44, 32, 119,
10715 111, 114, 108, 100, 33, 10, 0@};
10716 char ibm1047_hello[]
10717 = @{200, 133, 147, 147, 150, 107, 64, 166,
10718 150, 153, 147, 132, 90, 37, 0@};
10722 printf ("Hello, world!\n");
10726 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10727 containing the string @samp{Hello, world!} followed by a newline,
10728 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10730 We compile the program, and invoke the debugger on it:
10733 $ gcc -g charset-test.c -o charset-test
10734 $ gdb -nw charset-test
10735 GNU gdb 2001-12-19-cvs
10736 Copyright 2001 Free Software Foundation, Inc.
10741 We can use the @code{show charset} command to see what character sets
10742 @value{GDBN} is currently using to interpret and display characters and
10746 (@value{GDBP}) show charset
10747 The current host and target character set is `ISO-8859-1'.
10751 For the sake of printing this manual, let's use @sc{ascii} as our
10752 initial character set:
10754 (@value{GDBP}) set charset ASCII
10755 (@value{GDBP}) show charset
10756 The current host and target character set is `ASCII'.
10760 Let's assume that @sc{ascii} is indeed the correct character set for our
10761 host system --- in other words, let's assume that if @value{GDBN} prints
10762 characters using the @sc{ascii} character set, our terminal will display
10763 them properly. Since our current target character set is also
10764 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10767 (@value{GDBP}) print ascii_hello
10768 $1 = 0x401698 "Hello, world!\n"
10769 (@value{GDBP}) print ascii_hello[0]
10774 @value{GDBN} uses the target character set for character and string
10775 literals you use in expressions:
10778 (@value{GDBP}) print '+'
10783 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10786 @value{GDBN} relies on the user to tell it which character set the
10787 target program uses. If we print @code{ibm1047_hello} while our target
10788 character set is still @sc{ascii}, we get jibberish:
10791 (@value{GDBP}) print ibm1047_hello
10792 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10793 (@value{GDBP}) print ibm1047_hello[0]
10798 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10799 @value{GDBN} tells us the character sets it supports:
10802 (@value{GDBP}) set target-charset
10803 ASCII EBCDIC-US IBM1047 ISO-8859-1
10804 (@value{GDBP}) set target-charset
10807 We can select @sc{ibm1047} as our target character set, and examine the
10808 program's strings again. Now the @sc{ascii} string is wrong, but
10809 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10810 target character set, @sc{ibm1047}, to the host character set,
10811 @sc{ascii}, and they display correctly:
10814 (@value{GDBP}) set target-charset IBM1047
10815 (@value{GDBP}) show charset
10816 The current host character set is `ASCII'.
10817 The current target character set is `IBM1047'.
10818 (@value{GDBP}) print ascii_hello
10819 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10820 (@value{GDBP}) print ascii_hello[0]
10822 (@value{GDBP}) print ibm1047_hello
10823 $8 = 0x4016a8 "Hello, world!\n"
10824 (@value{GDBP}) print ibm1047_hello[0]
10829 As above, @value{GDBN} uses the target character set for character and
10830 string literals you use in expressions:
10833 (@value{GDBP}) print '+'
10838 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10841 @node Caching Target Data
10842 @section Caching Data of Targets
10843 @cindex caching data of targets
10845 @value{GDBN} caches data exchanged between the debugger and a target.
10846 Each cache is associated with the address space of the inferior.
10847 @xref{Inferiors and Programs}, about inferior and address space.
10848 Such caching generally improves performance in remote debugging
10849 (@pxref{Remote Debugging}), because it reduces the overhead of the
10850 remote protocol by bundling memory reads and writes into large chunks.
10851 Unfortunately, simply caching everything would lead to incorrect results,
10852 since @value{GDBN} does not necessarily know anything about volatile
10853 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10854 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10856 Therefore, by default, @value{GDBN} only caches data
10857 known to be on the stack@footnote{In non-stop mode, it is moderately
10858 rare for a running thread to modify the stack of a stopped thread
10859 in a way that would interfere with a backtrace, and caching of
10860 stack reads provides a significant speed up of remote backtraces.} or
10861 in the code segment.
10862 Other regions of memory can be explicitly marked as
10863 cacheable; @pxref{Memory Region Attributes}.
10866 @kindex set remotecache
10867 @item set remotecache on
10868 @itemx set remotecache off
10869 This option no longer does anything; it exists for compatibility
10872 @kindex show remotecache
10873 @item show remotecache
10874 Show the current state of the obsolete remotecache flag.
10876 @kindex set stack-cache
10877 @item set stack-cache on
10878 @itemx set stack-cache off
10879 Enable or disable caching of stack accesses. When @code{on}, use
10880 caching. By default, this option is @code{on}.
10882 @kindex show stack-cache
10883 @item show stack-cache
10884 Show the current state of data caching for memory accesses.
10886 @kindex set code-cache
10887 @item set code-cache on
10888 @itemx set code-cache off
10889 Enable or disable caching of code segment accesses. When @code{on},
10890 use caching. By default, this option is @code{on}. This improves
10891 performance of disassembly in remote debugging.
10893 @kindex show code-cache
10894 @item show code-cache
10895 Show the current state of target memory cache for code segment
10898 @kindex info dcache
10899 @item info dcache @r{[}line@r{]}
10900 Print the information about the performance of data cache of the
10901 current inferior's address space. The information displayed
10902 includes the dcache width and depth, and for each cache line, its
10903 number, address, and how many times it was referenced. This
10904 command is useful for debugging the data cache operation.
10906 If a line number is specified, the contents of that line will be
10909 @item set dcache size @var{size}
10910 @cindex dcache size
10911 @kindex set dcache size
10912 Set maximum number of entries in dcache (dcache depth above).
10914 @item set dcache line-size @var{line-size}
10915 @cindex dcache line-size
10916 @kindex set dcache line-size
10917 Set number of bytes each dcache entry caches (dcache width above).
10918 Must be a power of 2.
10920 @item show dcache size
10921 @kindex show dcache size
10922 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10924 @item show dcache line-size
10925 @kindex show dcache line-size
10926 Show default size of dcache lines.
10930 @node Searching Memory
10931 @section Search Memory
10932 @cindex searching memory
10934 Memory can be searched for a particular sequence of bytes with the
10935 @code{find} command.
10939 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10940 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10941 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10942 etc. The search begins at address @var{start_addr} and continues for either
10943 @var{len} bytes or through to @var{end_addr} inclusive.
10946 @var{s} and @var{n} are optional parameters.
10947 They may be specified in either order, apart or together.
10950 @item @var{s}, search query size
10951 The size of each search query value.
10957 halfwords (two bytes)
10961 giant words (eight bytes)
10964 All values are interpreted in the current language.
10965 This means, for example, that if the current source language is C/C@t{++}
10966 then searching for the string ``hello'' includes the trailing '\0'.
10968 If the value size is not specified, it is taken from the
10969 value's type in the current language.
10970 This is useful when one wants to specify the search
10971 pattern as a mixture of types.
10972 Note that this means, for example, that in the case of C-like languages
10973 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10974 which is typically four bytes.
10976 @item @var{n}, maximum number of finds
10977 The maximum number of matches to print. The default is to print all finds.
10980 You can use strings as search values. Quote them with double-quotes
10982 The string value is copied into the search pattern byte by byte,
10983 regardless of the endianness of the target and the size specification.
10985 The address of each match found is printed as well as a count of the
10986 number of matches found.
10988 The address of the last value found is stored in convenience variable
10990 A count of the number of matches is stored in @samp{$numfound}.
10992 For example, if stopped at the @code{printf} in this function:
10998 static char hello[] = "hello-hello";
10999 static struct @{ char c; short s; int i; @}
11000 __attribute__ ((packed)) mixed
11001 = @{ 'c', 0x1234, 0x87654321 @};
11002 printf ("%s\n", hello);
11007 you get during debugging:
11010 (gdb) find &hello[0], +sizeof(hello), "hello"
11011 0x804956d <hello.1620+6>
11013 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11014 0x8049567 <hello.1620>
11015 0x804956d <hello.1620+6>
11017 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11018 0x8049567 <hello.1620>
11020 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11021 0x8049560 <mixed.1625>
11023 (gdb) print $numfound
11026 $2 = (void *) 0x8049560
11029 @node Optimized Code
11030 @chapter Debugging Optimized Code
11031 @cindex optimized code, debugging
11032 @cindex debugging optimized code
11034 Almost all compilers support optimization. With optimization
11035 disabled, the compiler generates assembly code that corresponds
11036 directly to your source code, in a simplistic way. As the compiler
11037 applies more powerful optimizations, the generated assembly code
11038 diverges from your original source code. With help from debugging
11039 information generated by the compiler, @value{GDBN} can map from
11040 the running program back to constructs from your original source.
11042 @value{GDBN} is more accurate with optimization disabled. If you
11043 can recompile without optimization, it is easier to follow the
11044 progress of your program during debugging. But, there are many cases
11045 where you may need to debug an optimized version.
11047 When you debug a program compiled with @samp{-g -O}, remember that the
11048 optimizer has rearranged your code; the debugger shows you what is
11049 really there. Do not be too surprised when the execution path does not
11050 exactly match your source file! An extreme example: if you define a
11051 variable, but never use it, @value{GDBN} never sees that
11052 variable---because the compiler optimizes it out of existence.
11054 Some things do not work as well with @samp{-g -O} as with just
11055 @samp{-g}, particularly on machines with instruction scheduling. If in
11056 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11057 please report it to us as a bug (including a test case!).
11058 @xref{Variables}, for more information about debugging optimized code.
11061 * Inline Functions:: How @value{GDBN} presents inlining
11062 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11065 @node Inline Functions
11066 @section Inline Functions
11067 @cindex inline functions, debugging
11069 @dfn{Inlining} is an optimization that inserts a copy of the function
11070 body directly at each call site, instead of jumping to a shared
11071 routine. @value{GDBN} displays inlined functions just like
11072 non-inlined functions. They appear in backtraces. You can view their
11073 arguments and local variables, step into them with @code{step}, skip
11074 them with @code{next}, and escape from them with @code{finish}.
11075 You can check whether a function was inlined by using the
11076 @code{info frame} command.
11078 For @value{GDBN} to support inlined functions, the compiler must
11079 record information about inlining in the debug information ---
11080 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11081 other compilers do also. @value{GDBN} only supports inlined functions
11082 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11083 do not emit two required attributes (@samp{DW_AT_call_file} and
11084 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11085 function calls with earlier versions of @value{NGCC}. It instead
11086 displays the arguments and local variables of inlined functions as
11087 local variables in the caller.
11089 The body of an inlined function is directly included at its call site;
11090 unlike a non-inlined function, there are no instructions devoted to
11091 the call. @value{GDBN} still pretends that the call site and the
11092 start of the inlined function are different instructions. Stepping to
11093 the call site shows the call site, and then stepping again shows
11094 the first line of the inlined function, even though no additional
11095 instructions are executed.
11097 This makes source-level debugging much clearer; you can see both the
11098 context of the call and then the effect of the call. Only stepping by
11099 a single instruction using @code{stepi} or @code{nexti} does not do
11100 this; single instruction steps always show the inlined body.
11102 There are some ways that @value{GDBN} does not pretend that inlined
11103 function calls are the same as normal calls:
11107 Setting breakpoints at the call site of an inlined function may not
11108 work, because the call site does not contain any code. @value{GDBN}
11109 may incorrectly move the breakpoint to the next line of the enclosing
11110 function, after the call. This limitation will be removed in a future
11111 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11112 or inside the inlined function instead.
11115 @value{GDBN} cannot locate the return value of inlined calls after
11116 using the @code{finish} command. This is a limitation of compiler-generated
11117 debugging information; after @code{finish}, you can step to the next line
11118 and print a variable where your program stored the return value.
11122 @node Tail Call Frames
11123 @section Tail Call Frames
11124 @cindex tail call frames, debugging
11126 Function @code{B} can call function @code{C} in its very last statement. In
11127 unoptimized compilation the call of @code{C} is immediately followed by return
11128 instruction at the end of @code{B} code. Optimizing compiler may replace the
11129 call and return in function @code{B} into one jump to function @code{C}
11130 instead. Such use of a jump instruction is called @dfn{tail call}.
11132 During execution of function @code{C}, there will be no indication in the
11133 function call stack frames that it was tail-called from @code{B}. If function
11134 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11135 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11136 some cases @value{GDBN} can determine that @code{C} was tail-called from
11137 @code{B}, and it will then create fictitious call frame for that, with the
11138 return address set up as if @code{B} called @code{C} normally.
11140 This functionality is currently supported only by DWARF 2 debugging format and
11141 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11142 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11145 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11146 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11150 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11152 Stack level 1, frame at 0x7fffffffda30:
11153 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11154 tail call frame, caller of frame at 0x7fffffffda30
11155 source language c++.
11156 Arglist at unknown address.
11157 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11160 The detection of all the possible code path executions can find them ambiguous.
11161 There is no execution history stored (possible @ref{Reverse Execution} is never
11162 used for this purpose) and the last known caller could have reached the known
11163 callee by multiple different jump sequences. In such case @value{GDBN} still
11164 tries to show at least all the unambiguous top tail callers and all the
11165 unambiguous bottom tail calees, if any.
11168 @anchor{set debug entry-values}
11169 @item set debug entry-values
11170 @kindex set debug entry-values
11171 When set to on, enables printing of analysis messages for both frame argument
11172 values at function entry and tail calls. It will show all the possible valid
11173 tail calls code paths it has considered. It will also print the intersection
11174 of them with the final unambiguous (possibly partial or even empty) code path
11177 @item show debug entry-values
11178 @kindex show debug entry-values
11179 Show the current state of analysis messages printing for both frame argument
11180 values at function entry and tail calls.
11183 The analysis messages for tail calls can for example show why the virtual tail
11184 call frame for function @code{c} has not been recognized (due to the indirect
11185 reference by variable @code{x}):
11188 static void __attribute__((noinline, noclone)) c (void);
11189 void (*x) (void) = c;
11190 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11191 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11192 int main (void) @{ x (); return 0; @}
11194 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11195 DW_TAG_GNU_call_site 0x40039a in main
11197 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11200 #1 0x000000000040039a in main () at t.c:5
11203 Another possibility is an ambiguous virtual tail call frames resolution:
11207 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11208 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11209 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11210 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11211 static void __attribute__((noinline, noclone)) b (void)
11212 @{ if (i) c (); else e (); @}
11213 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11214 int main (void) @{ a (); return 0; @}
11216 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11217 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11218 tailcall: reduced: 0x4004d2(a) |
11221 #1 0x00000000004004d2 in a () at t.c:8
11222 #2 0x0000000000400395 in main () at t.c:9
11225 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11226 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11228 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11229 @ifset HAVE_MAKEINFO_CLICK
11230 @set ARROW @click{}
11231 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11232 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11234 @ifclear HAVE_MAKEINFO_CLICK
11236 @set CALLSEQ1B @value{CALLSEQ1A}
11237 @set CALLSEQ2B @value{CALLSEQ2A}
11240 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11241 The code can have possible execution paths @value{CALLSEQ1B} or
11242 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11244 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11245 has found. It then finds another possible calling sequcen - that one is
11246 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11247 printed as the @code{reduced:} calling sequence. That one could have many
11248 futher @code{compare:} and @code{reduced:} statements as long as there remain
11249 any non-ambiguous sequence entries.
11251 For the frame of function @code{b} in both cases there are different possible
11252 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11253 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11254 therefore this one is displayed to the user while the ambiguous frames are
11257 There can be also reasons why printing of frame argument values at function
11262 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11263 static void __attribute__((noinline, noclone)) a (int i);
11264 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11265 static void __attribute__((noinline, noclone)) a (int i)
11266 @{ if (i) b (i - 1); else c (0); @}
11267 int main (void) @{ a (5); return 0; @}
11270 #0 c (i=i@@entry=0) at t.c:2
11271 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11272 function "a" at 0x400420 can call itself via tail calls
11273 i=<optimized out>) at t.c:6
11274 #2 0x000000000040036e in main () at t.c:7
11277 @value{GDBN} cannot find out from the inferior state if and how many times did
11278 function @code{a} call itself (via function @code{b}) as these calls would be
11279 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11280 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11281 prints @code{<optimized out>} instead.
11284 @chapter C Preprocessor Macros
11286 Some languages, such as C and C@t{++}, provide a way to define and invoke
11287 ``preprocessor macros'' which expand into strings of tokens.
11288 @value{GDBN} can evaluate expressions containing macro invocations, show
11289 the result of macro expansion, and show a macro's definition, including
11290 where it was defined.
11292 You may need to compile your program specially to provide @value{GDBN}
11293 with information about preprocessor macros. Most compilers do not
11294 include macros in their debugging information, even when you compile
11295 with the @option{-g} flag. @xref{Compilation}.
11297 A program may define a macro at one point, remove that definition later,
11298 and then provide a different definition after that. Thus, at different
11299 points in the program, a macro may have different definitions, or have
11300 no definition at all. If there is a current stack frame, @value{GDBN}
11301 uses the macros in scope at that frame's source code line. Otherwise,
11302 @value{GDBN} uses the macros in scope at the current listing location;
11305 Whenever @value{GDBN} evaluates an expression, it always expands any
11306 macro invocations present in the expression. @value{GDBN} also provides
11307 the following commands for working with macros explicitly.
11311 @kindex macro expand
11312 @cindex macro expansion, showing the results of preprocessor
11313 @cindex preprocessor macro expansion, showing the results of
11314 @cindex expanding preprocessor macros
11315 @item macro expand @var{expression}
11316 @itemx macro exp @var{expression}
11317 Show the results of expanding all preprocessor macro invocations in
11318 @var{expression}. Since @value{GDBN} simply expands macros, but does
11319 not parse the result, @var{expression} need not be a valid expression;
11320 it can be any string of tokens.
11323 @item macro expand-once @var{expression}
11324 @itemx macro exp1 @var{expression}
11325 @cindex expand macro once
11326 @i{(This command is not yet implemented.)} Show the results of
11327 expanding those preprocessor macro invocations that appear explicitly in
11328 @var{expression}. Macro invocations appearing in that expansion are
11329 left unchanged. This command allows you to see the effect of a
11330 particular macro more clearly, without being confused by further
11331 expansions. Since @value{GDBN} simply expands macros, but does not
11332 parse the result, @var{expression} need not be a valid expression; it
11333 can be any string of tokens.
11336 @cindex macro definition, showing
11337 @cindex definition of a macro, showing
11338 @cindex macros, from debug info
11339 @item info macro [-a|-all] [--] @var{macro}
11340 Show the current definition or all definitions of the named @var{macro},
11341 and describe the source location or compiler command-line where that
11342 definition was established. The optional double dash is to signify the end of
11343 argument processing and the beginning of @var{macro} for non C-like macros where
11344 the macro may begin with a hyphen.
11346 @kindex info macros
11347 @item info macros @var{linespec}
11348 Show all macro definitions that are in effect at the location specified
11349 by @var{linespec}, and describe the source location or compiler
11350 command-line where those definitions were established.
11352 @kindex macro define
11353 @cindex user-defined macros
11354 @cindex defining macros interactively
11355 @cindex macros, user-defined
11356 @item macro define @var{macro} @var{replacement-list}
11357 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11358 Introduce a definition for a preprocessor macro named @var{macro},
11359 invocations of which are replaced by the tokens given in
11360 @var{replacement-list}. The first form of this command defines an
11361 ``object-like'' macro, which takes no arguments; the second form
11362 defines a ``function-like'' macro, which takes the arguments given in
11365 A definition introduced by this command is in scope in every
11366 expression evaluated in @value{GDBN}, until it is removed with the
11367 @code{macro undef} command, described below. The definition overrides
11368 all definitions for @var{macro} present in the program being debugged,
11369 as well as any previous user-supplied definition.
11371 @kindex macro undef
11372 @item macro undef @var{macro}
11373 Remove any user-supplied definition for the macro named @var{macro}.
11374 This command only affects definitions provided with the @code{macro
11375 define} command, described above; it cannot remove definitions present
11376 in the program being debugged.
11380 List all the macros defined using the @code{macro define} command.
11383 @cindex macros, example of debugging with
11384 Here is a transcript showing the above commands in action. First, we
11385 show our source files:
11390 #include "sample.h"
11393 #define ADD(x) (M + x)
11398 printf ("Hello, world!\n");
11400 printf ("We're so creative.\n");
11402 printf ("Goodbye, world!\n");
11409 Now, we compile the program using the @sc{gnu} C compiler,
11410 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11411 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11412 and @option{-gdwarf-4}; we recommend always choosing the most recent
11413 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11414 includes information about preprocessor macros in the debugging
11418 $ gcc -gdwarf-2 -g3 sample.c -o sample
11422 Now, we start @value{GDBN} on our sample program:
11426 GNU gdb 2002-05-06-cvs
11427 Copyright 2002 Free Software Foundation, Inc.
11428 GDB is free software, @dots{}
11432 We can expand macros and examine their definitions, even when the
11433 program is not running. @value{GDBN} uses the current listing position
11434 to decide which macro definitions are in scope:
11437 (@value{GDBP}) list main
11440 5 #define ADD(x) (M + x)
11445 10 printf ("Hello, world!\n");
11447 12 printf ("We're so creative.\n");
11448 (@value{GDBP}) info macro ADD
11449 Defined at /home/jimb/gdb/macros/play/sample.c:5
11450 #define ADD(x) (M + x)
11451 (@value{GDBP}) info macro Q
11452 Defined at /home/jimb/gdb/macros/play/sample.h:1
11453 included at /home/jimb/gdb/macros/play/sample.c:2
11455 (@value{GDBP}) macro expand ADD(1)
11456 expands to: (42 + 1)
11457 (@value{GDBP}) macro expand-once ADD(1)
11458 expands to: once (M + 1)
11462 In the example above, note that @code{macro expand-once} expands only
11463 the macro invocation explicit in the original text --- the invocation of
11464 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11465 which was introduced by @code{ADD}.
11467 Once the program is running, @value{GDBN} uses the macro definitions in
11468 force at the source line of the current stack frame:
11471 (@value{GDBP}) break main
11472 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11474 Starting program: /home/jimb/gdb/macros/play/sample
11476 Breakpoint 1, main () at sample.c:10
11477 10 printf ("Hello, world!\n");
11481 At line 10, the definition of the macro @code{N} at line 9 is in force:
11484 (@value{GDBP}) info macro N
11485 Defined at /home/jimb/gdb/macros/play/sample.c:9
11487 (@value{GDBP}) macro expand N Q M
11488 expands to: 28 < 42
11489 (@value{GDBP}) print N Q M
11494 As we step over directives that remove @code{N}'s definition, and then
11495 give it a new definition, @value{GDBN} finds the definition (or lack
11496 thereof) in force at each point:
11499 (@value{GDBP}) next
11501 12 printf ("We're so creative.\n");
11502 (@value{GDBP}) info macro N
11503 The symbol `N' has no definition as a C/C++ preprocessor macro
11504 at /home/jimb/gdb/macros/play/sample.c:12
11505 (@value{GDBP}) next
11507 14 printf ("Goodbye, world!\n");
11508 (@value{GDBP}) info macro N
11509 Defined at /home/jimb/gdb/macros/play/sample.c:13
11511 (@value{GDBP}) macro expand N Q M
11512 expands to: 1729 < 42
11513 (@value{GDBP}) print N Q M
11518 In addition to source files, macros can be defined on the compilation command
11519 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11520 such a way, @value{GDBN} displays the location of their definition as line zero
11521 of the source file submitted to the compiler.
11524 (@value{GDBP}) info macro __STDC__
11525 Defined at /home/jimb/gdb/macros/play/sample.c:0
11532 @chapter Tracepoints
11533 @c This chapter is based on the documentation written by Michael
11534 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11536 @cindex tracepoints
11537 In some applications, it is not feasible for the debugger to interrupt
11538 the program's execution long enough for the developer to learn
11539 anything helpful about its behavior. If the program's correctness
11540 depends on its real-time behavior, delays introduced by a debugger
11541 might cause the program to change its behavior drastically, or perhaps
11542 fail, even when the code itself is correct. It is useful to be able
11543 to observe the program's behavior without interrupting it.
11545 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11546 specify locations in the program, called @dfn{tracepoints}, and
11547 arbitrary expressions to evaluate when those tracepoints are reached.
11548 Later, using the @code{tfind} command, you can examine the values
11549 those expressions had when the program hit the tracepoints. The
11550 expressions may also denote objects in memory---structures or arrays,
11551 for example---whose values @value{GDBN} should record; while visiting
11552 a particular tracepoint, you may inspect those objects as if they were
11553 in memory at that moment. However, because @value{GDBN} records these
11554 values without interacting with you, it can do so quickly and
11555 unobtrusively, hopefully not disturbing the program's behavior.
11557 The tracepoint facility is currently available only for remote
11558 targets. @xref{Targets}. In addition, your remote target must know
11559 how to collect trace data. This functionality is implemented in the
11560 remote stub; however, none of the stubs distributed with @value{GDBN}
11561 support tracepoints as of this writing. The format of the remote
11562 packets used to implement tracepoints are described in @ref{Tracepoint
11565 It is also possible to get trace data from a file, in a manner reminiscent
11566 of corefiles; you specify the filename, and use @code{tfind} to search
11567 through the file. @xref{Trace Files}, for more details.
11569 This chapter describes the tracepoint commands and features.
11572 * Set Tracepoints::
11573 * Analyze Collected Data::
11574 * Tracepoint Variables::
11578 @node Set Tracepoints
11579 @section Commands to Set Tracepoints
11581 Before running such a @dfn{trace experiment}, an arbitrary number of
11582 tracepoints can be set. A tracepoint is actually a special type of
11583 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11584 standard breakpoint commands. For instance, as with breakpoints,
11585 tracepoint numbers are successive integers starting from one, and many
11586 of the commands associated with tracepoints take the tracepoint number
11587 as their argument, to identify which tracepoint to work on.
11589 For each tracepoint, you can specify, in advance, some arbitrary set
11590 of data that you want the target to collect in the trace buffer when
11591 it hits that tracepoint. The collected data can include registers,
11592 local variables, or global data. Later, you can use @value{GDBN}
11593 commands to examine the values these data had at the time the
11594 tracepoint was hit.
11596 Tracepoints do not support every breakpoint feature. Ignore counts on
11597 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11598 commands when they are hit. Tracepoints may not be thread-specific
11601 @cindex fast tracepoints
11602 Some targets may support @dfn{fast tracepoints}, which are inserted in
11603 a different way (such as with a jump instead of a trap), that is
11604 faster but possibly restricted in where they may be installed.
11606 @cindex static tracepoints
11607 @cindex markers, static tracepoints
11608 @cindex probing markers, static tracepoints
11609 Regular and fast tracepoints are dynamic tracing facilities, meaning
11610 that they can be used to insert tracepoints at (almost) any location
11611 in the target. Some targets may also support controlling @dfn{static
11612 tracepoints} from @value{GDBN}. With static tracing, a set of
11613 instrumentation points, also known as @dfn{markers}, are embedded in
11614 the target program, and can be activated or deactivated by name or
11615 address. These are usually placed at locations which facilitate
11616 investigating what the target is actually doing. @value{GDBN}'s
11617 support for static tracing includes being able to list instrumentation
11618 points, and attach them with @value{GDBN} defined high level
11619 tracepoints that expose the whole range of convenience of
11620 @value{GDBN}'s tracepoints support. Namely, support for collecting
11621 registers values and values of global or local (to the instrumentation
11622 point) variables; tracepoint conditions and trace state variables.
11623 The act of installing a @value{GDBN} static tracepoint on an
11624 instrumentation point, or marker, is referred to as @dfn{probing} a
11625 static tracepoint marker.
11627 @code{gdbserver} supports tracepoints on some target systems.
11628 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11630 This section describes commands to set tracepoints and associated
11631 conditions and actions.
11634 * Create and Delete Tracepoints::
11635 * Enable and Disable Tracepoints::
11636 * Tracepoint Passcounts::
11637 * Tracepoint Conditions::
11638 * Trace State Variables::
11639 * Tracepoint Actions::
11640 * Listing Tracepoints::
11641 * Listing Static Tracepoint Markers::
11642 * Starting and Stopping Trace Experiments::
11643 * Tracepoint Restrictions::
11646 @node Create and Delete Tracepoints
11647 @subsection Create and Delete Tracepoints
11650 @cindex set tracepoint
11652 @item trace @var{location}
11653 The @code{trace} command is very similar to the @code{break} command.
11654 Its argument @var{location} can be a source line, a function name, or
11655 an address in the target program. @xref{Specify Location}. The
11656 @code{trace} command defines a tracepoint, which is a point in the
11657 target program where the debugger will briefly stop, collect some
11658 data, and then allow the program to continue. Setting a tracepoint or
11659 changing its actions takes effect immediately if the remote stub
11660 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11662 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11663 these changes don't take effect until the next @code{tstart}
11664 command, and once a trace experiment is running, further changes will
11665 not have any effect until the next trace experiment starts. In addition,
11666 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11667 address is not yet resolved. (This is similar to pending breakpoints.)
11668 Pending tracepoints are not downloaded to the target and not installed
11669 until they are resolved. The resolution of pending tracepoints requires
11670 @value{GDBN} support---when debugging with the remote target, and
11671 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11672 tracing}), pending tracepoints can not be resolved (and downloaded to
11673 the remote stub) while @value{GDBN} is disconnected.
11675 Here are some examples of using the @code{trace} command:
11678 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11680 (@value{GDBP}) @b{trace +2} // 2 lines forward
11682 (@value{GDBP}) @b{trace my_function} // first source line of function
11684 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11686 (@value{GDBP}) @b{trace *0x2117c4} // an address
11690 You can abbreviate @code{trace} as @code{tr}.
11692 @item trace @var{location} if @var{cond}
11693 Set a tracepoint with condition @var{cond}; evaluate the expression
11694 @var{cond} each time the tracepoint is reached, and collect data only
11695 if the value is nonzero---that is, if @var{cond} evaluates as true.
11696 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11697 information on tracepoint conditions.
11699 @item ftrace @var{location} [ if @var{cond} ]
11700 @cindex set fast tracepoint
11701 @cindex fast tracepoints, setting
11703 The @code{ftrace} command sets a fast tracepoint. For targets that
11704 support them, fast tracepoints will use a more efficient but possibly
11705 less general technique to trigger data collection, such as a jump
11706 instruction instead of a trap, or some sort of hardware support. It
11707 may not be possible to create a fast tracepoint at the desired
11708 location, in which case the command will exit with an explanatory
11711 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11714 On 32-bit x86-architecture systems, fast tracepoints normally need to
11715 be placed at an instruction that is 5 bytes or longer, but can be
11716 placed at 4-byte instructions if the low 64K of memory of the target
11717 program is available to install trampolines. Some Unix-type systems,
11718 such as @sc{gnu}/Linux, exclude low addresses from the program's
11719 address space; but for instance with the Linux kernel it is possible
11720 to let @value{GDBN} use this area by doing a @command{sysctl} command
11721 to set the @code{mmap_min_addr} kernel parameter, as in
11724 sudo sysctl -w vm.mmap_min_addr=32768
11728 which sets the low address to 32K, which leaves plenty of room for
11729 trampolines. The minimum address should be set to a page boundary.
11731 @item strace @var{location} [ if @var{cond} ]
11732 @cindex set static tracepoint
11733 @cindex static tracepoints, setting
11734 @cindex probe static tracepoint marker
11736 The @code{strace} command sets a static tracepoint. For targets that
11737 support it, setting a static tracepoint probes a static
11738 instrumentation point, or marker, found at @var{location}. It may not
11739 be possible to set a static tracepoint at the desired location, in
11740 which case the command will exit with an explanatory message.
11742 @value{GDBN} handles arguments to @code{strace} exactly as for
11743 @code{trace}, with the addition that the user can also specify
11744 @code{-m @var{marker}} as @var{location}. This probes the marker
11745 identified by the @var{marker} string identifier. This identifier
11746 depends on the static tracepoint backend library your program is
11747 using. You can find all the marker identifiers in the @samp{ID} field
11748 of the @code{info static-tracepoint-markers} command output.
11749 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11750 Markers}. For example, in the following small program using the UST
11756 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11761 the marker id is composed of joining the first two arguments to the
11762 @code{trace_mark} call with a slash, which translates to:
11765 (@value{GDBP}) info static-tracepoint-markers
11766 Cnt Enb ID Address What
11767 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11773 so you may probe the marker above with:
11776 (@value{GDBP}) strace -m ust/bar33
11779 Static tracepoints accept an extra collect action --- @code{collect
11780 $_sdata}. This collects arbitrary user data passed in the probe point
11781 call to the tracing library. In the UST example above, you'll see
11782 that the third argument to @code{trace_mark} is a printf-like format
11783 string. The user data is then the result of running that formating
11784 string against the following arguments. Note that @code{info
11785 static-tracepoint-markers} command output lists that format string in
11786 the @samp{Data:} field.
11788 You can inspect this data when analyzing the trace buffer, by printing
11789 the $_sdata variable like any other variable available to
11790 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11793 @cindex last tracepoint number
11794 @cindex recent tracepoint number
11795 @cindex tracepoint number
11796 The convenience variable @code{$tpnum} records the tracepoint number
11797 of the most recently set tracepoint.
11799 @kindex delete tracepoint
11800 @cindex tracepoint deletion
11801 @item delete tracepoint @r{[}@var{num}@r{]}
11802 Permanently delete one or more tracepoints. With no argument, the
11803 default is to delete all tracepoints. Note that the regular
11804 @code{delete} command can remove tracepoints also.
11809 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11811 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11815 You can abbreviate this command as @code{del tr}.
11818 @node Enable and Disable Tracepoints
11819 @subsection Enable and Disable Tracepoints
11821 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11824 @kindex disable tracepoint
11825 @item disable tracepoint @r{[}@var{num}@r{]}
11826 Disable tracepoint @var{num}, or all tracepoints if no argument
11827 @var{num} is given. A disabled tracepoint will have no effect during
11828 a trace experiment, but it is not forgotten. You can re-enable
11829 a disabled tracepoint using the @code{enable tracepoint} command.
11830 If the command is issued during a trace experiment and the debug target
11831 has support for disabling tracepoints during a trace experiment, then the
11832 change will be effective immediately. Otherwise, it will be applied to the
11833 next trace experiment.
11835 @kindex enable tracepoint
11836 @item enable tracepoint @r{[}@var{num}@r{]}
11837 Enable tracepoint @var{num}, or all tracepoints. If this command is
11838 issued during a trace experiment and the debug target supports enabling
11839 tracepoints during a trace experiment, then the enabled tracepoints will
11840 become effective immediately. Otherwise, they will become effective the
11841 next time a trace experiment is run.
11844 @node Tracepoint Passcounts
11845 @subsection Tracepoint Passcounts
11849 @cindex tracepoint pass count
11850 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11851 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11852 automatically stop a trace experiment. If a tracepoint's passcount is
11853 @var{n}, then the trace experiment will be automatically stopped on
11854 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11855 @var{num} is not specified, the @code{passcount} command sets the
11856 passcount of the most recently defined tracepoint. If no passcount is
11857 given, the trace experiment will run until stopped explicitly by the
11863 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11864 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11866 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11867 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11868 (@value{GDBP}) @b{trace foo}
11869 (@value{GDBP}) @b{pass 3}
11870 (@value{GDBP}) @b{trace bar}
11871 (@value{GDBP}) @b{pass 2}
11872 (@value{GDBP}) @b{trace baz}
11873 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11874 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11875 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11876 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11880 @node Tracepoint Conditions
11881 @subsection Tracepoint Conditions
11882 @cindex conditional tracepoints
11883 @cindex tracepoint conditions
11885 The simplest sort of tracepoint collects data every time your program
11886 reaches a specified place. You can also specify a @dfn{condition} for
11887 a tracepoint. A condition is just a Boolean expression in your
11888 programming language (@pxref{Expressions, ,Expressions}). A
11889 tracepoint with a condition evaluates the expression each time your
11890 program reaches it, and data collection happens only if the condition
11893 Tracepoint conditions can be specified when a tracepoint is set, by
11894 using @samp{if} in the arguments to the @code{trace} command.
11895 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11896 also be set or changed at any time with the @code{condition} command,
11897 just as with breakpoints.
11899 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11900 the conditional expression itself. Instead, @value{GDBN} encodes the
11901 expression into an agent expression (@pxref{Agent Expressions})
11902 suitable for execution on the target, independently of @value{GDBN}.
11903 Global variables become raw memory locations, locals become stack
11904 accesses, and so forth.
11906 For instance, suppose you have a function that is usually called
11907 frequently, but should not be called after an error has occurred. You
11908 could use the following tracepoint command to collect data about calls
11909 of that function that happen while the error code is propagating
11910 through the program; an unconditional tracepoint could end up
11911 collecting thousands of useless trace frames that you would have to
11915 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11918 @node Trace State Variables
11919 @subsection Trace State Variables
11920 @cindex trace state variables
11922 A @dfn{trace state variable} is a special type of variable that is
11923 created and managed by target-side code. The syntax is the same as
11924 that for GDB's convenience variables (a string prefixed with ``$''),
11925 but they are stored on the target. They must be created explicitly,
11926 using a @code{tvariable} command. They are always 64-bit signed
11929 Trace state variables are remembered by @value{GDBN}, and downloaded
11930 to the target along with tracepoint information when the trace
11931 experiment starts. There are no intrinsic limits on the number of
11932 trace state variables, beyond memory limitations of the target.
11934 @cindex convenience variables, and trace state variables
11935 Although trace state variables are managed by the target, you can use
11936 them in print commands and expressions as if they were convenience
11937 variables; @value{GDBN} will get the current value from the target
11938 while the trace experiment is running. Trace state variables share
11939 the same namespace as other ``$'' variables, which means that you
11940 cannot have trace state variables with names like @code{$23} or
11941 @code{$pc}, nor can you have a trace state variable and a convenience
11942 variable with the same name.
11946 @item tvariable $@var{name} [ = @var{expression} ]
11948 The @code{tvariable} command creates a new trace state variable named
11949 @code{$@var{name}}, and optionally gives it an initial value of
11950 @var{expression}. @var{expression} is evaluated when this command is
11951 entered; the result will be converted to an integer if possible,
11952 otherwise @value{GDBN} will report an error. A subsequent
11953 @code{tvariable} command specifying the same name does not create a
11954 variable, but instead assigns the supplied initial value to the
11955 existing variable of that name, overwriting any previous initial
11956 value. The default initial value is 0.
11958 @item info tvariables
11959 @kindex info tvariables
11960 List all the trace state variables along with their initial values.
11961 Their current values may also be displayed, if the trace experiment is
11964 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11965 @kindex delete tvariable
11966 Delete the given trace state variables, or all of them if no arguments
11971 @node Tracepoint Actions
11972 @subsection Tracepoint Action Lists
11976 @cindex tracepoint actions
11977 @item actions @r{[}@var{num}@r{]}
11978 This command will prompt for a list of actions to be taken when the
11979 tracepoint is hit. If the tracepoint number @var{num} is not
11980 specified, this command sets the actions for the one that was most
11981 recently defined (so that you can define a tracepoint and then say
11982 @code{actions} without bothering about its number). You specify the
11983 actions themselves on the following lines, one action at a time, and
11984 terminate the actions list with a line containing just @code{end}. So
11985 far, the only defined actions are @code{collect}, @code{teval}, and
11986 @code{while-stepping}.
11988 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11989 Commands, ,Breakpoint Command Lists}), except that only the defined
11990 actions are allowed; any other @value{GDBN} command is rejected.
11992 @cindex remove actions from a tracepoint
11993 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11994 and follow it immediately with @samp{end}.
11997 (@value{GDBP}) @b{collect @var{data}} // collect some data
11999 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12001 (@value{GDBP}) @b{end} // signals the end of actions.
12004 In the following example, the action list begins with @code{collect}
12005 commands indicating the things to be collected when the tracepoint is
12006 hit. Then, in order to single-step and collect additional data
12007 following the tracepoint, a @code{while-stepping} command is used,
12008 followed by the list of things to be collected after each step in a
12009 sequence of single steps. The @code{while-stepping} command is
12010 terminated by its own separate @code{end} command. Lastly, the action
12011 list is terminated by an @code{end} command.
12014 (@value{GDBP}) @b{trace foo}
12015 (@value{GDBP}) @b{actions}
12016 Enter actions for tracepoint 1, one per line:
12019 > while-stepping 12
12020 > collect $pc, arr[i]
12025 @kindex collect @r{(tracepoints)}
12026 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12027 Collect values of the given expressions when the tracepoint is hit.
12028 This command accepts a comma-separated list of any valid expressions.
12029 In addition to global, static, or local variables, the following
12030 special arguments are supported:
12034 Collect all registers.
12037 Collect all function arguments.
12040 Collect all local variables.
12043 Collect the return address. This is helpful if you want to see more
12047 Collects the number of arguments from the static probe at which the
12048 tracepoint is located.
12049 @xref{Static Probe Points}.
12051 @item $_probe_arg@var{n}
12052 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12053 from the static probe at which the tracepoint is located.
12054 @xref{Static Probe Points}.
12057 @vindex $_sdata@r{, collect}
12058 Collect static tracepoint marker specific data. Only available for
12059 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12060 Lists}. On the UST static tracepoints library backend, an
12061 instrumentation point resembles a @code{printf} function call. The
12062 tracing library is able to collect user specified data formatted to a
12063 character string using the format provided by the programmer that
12064 instrumented the program. Other backends have similar mechanisms.
12065 Here's an example of a UST marker call:
12068 const char master_name[] = "$your_name";
12069 trace_mark(channel1, marker1, "hello %s", master_name)
12072 In this case, collecting @code{$_sdata} collects the string
12073 @samp{hello $yourname}. When analyzing the trace buffer, you can
12074 inspect @samp{$_sdata} like any other variable available to
12078 You can give several consecutive @code{collect} commands, each one
12079 with a single argument, or one @code{collect} command with several
12080 arguments separated by commas; the effect is the same.
12082 The optional @var{mods} changes the usual handling of the arguments.
12083 @code{s} requests that pointers to chars be handled as strings, in
12084 particular collecting the contents of the memory being pointed at, up
12085 to the first zero. The upper bound is by default the value of the
12086 @code{print elements} variable; if @code{s} is followed by a decimal
12087 number, that is the upper bound instead. So for instance
12088 @samp{collect/s25 mystr} collects as many as 25 characters at
12091 The command @code{info scope} (@pxref{Symbols, info scope}) is
12092 particularly useful for figuring out what data to collect.
12094 @kindex teval @r{(tracepoints)}
12095 @item teval @var{expr1}, @var{expr2}, @dots{}
12096 Evaluate the given expressions when the tracepoint is hit. This
12097 command accepts a comma-separated list of expressions. The results
12098 are discarded, so this is mainly useful for assigning values to trace
12099 state variables (@pxref{Trace State Variables}) without adding those
12100 values to the trace buffer, as would be the case if the @code{collect}
12103 @kindex while-stepping @r{(tracepoints)}
12104 @item while-stepping @var{n}
12105 Perform @var{n} single-step instruction traces after the tracepoint,
12106 collecting new data after each step. The @code{while-stepping}
12107 command is followed by the list of what to collect while stepping
12108 (followed by its own @code{end} command):
12111 > while-stepping 12
12112 > collect $regs, myglobal
12118 Note that @code{$pc} is not automatically collected by
12119 @code{while-stepping}; you need to explicitly collect that register if
12120 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12123 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12124 @kindex set default-collect
12125 @cindex default collection action
12126 This variable is a list of expressions to collect at each tracepoint
12127 hit. It is effectively an additional @code{collect} action prepended
12128 to every tracepoint action list. The expressions are parsed
12129 individually for each tracepoint, so for instance a variable named
12130 @code{xyz} may be interpreted as a global for one tracepoint, and a
12131 local for another, as appropriate to the tracepoint's location.
12133 @item show default-collect
12134 @kindex show default-collect
12135 Show the list of expressions that are collected by default at each
12140 @node Listing Tracepoints
12141 @subsection Listing Tracepoints
12144 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12145 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12146 @cindex information about tracepoints
12147 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12148 Display information about the tracepoint @var{num}. If you don't
12149 specify a tracepoint number, displays information about all the
12150 tracepoints defined so far. The format is similar to that used for
12151 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12152 command, simply restricting itself to tracepoints.
12154 A tracepoint's listing may include additional information specific to
12159 its passcount as given by the @code{passcount @var{n}} command
12162 the state about installed on target of each location
12166 (@value{GDBP}) @b{info trace}
12167 Num Type Disp Enb Address What
12168 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12170 collect globfoo, $regs
12175 2 tracepoint keep y <MULTIPLE>
12177 2.1 y 0x0804859c in func4 at change-loc.h:35
12178 installed on target
12179 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12180 installed on target
12181 2.3 y <PENDING> set_tracepoint
12182 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12183 not installed on target
12188 This command can be abbreviated @code{info tp}.
12191 @node Listing Static Tracepoint Markers
12192 @subsection Listing Static Tracepoint Markers
12195 @kindex info static-tracepoint-markers
12196 @cindex information about static tracepoint markers
12197 @item info static-tracepoint-markers
12198 Display information about all static tracepoint markers defined in the
12201 For each marker, the following columns are printed:
12205 An incrementing counter, output to help readability. This is not a
12208 The marker ID, as reported by the target.
12209 @item Enabled or Disabled
12210 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12211 that are not enabled.
12213 Where the marker is in your program, as a memory address.
12215 Where the marker is in the source for your program, as a file and line
12216 number. If the debug information included in the program does not
12217 allow @value{GDBN} to locate the source of the marker, this column
12218 will be left blank.
12222 In addition, the following information may be printed for each marker:
12226 User data passed to the tracing library by the marker call. In the
12227 UST backend, this is the format string passed as argument to the
12229 @item Static tracepoints probing the marker
12230 The list of static tracepoints attached to the marker.
12234 (@value{GDBP}) info static-tracepoint-markers
12235 Cnt ID Enb Address What
12236 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12237 Data: number1 %d number2 %d
12238 Probed by static tracepoints: #2
12239 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12245 @node Starting and Stopping Trace Experiments
12246 @subsection Starting and Stopping Trace Experiments
12249 @kindex tstart [ @var{notes} ]
12250 @cindex start a new trace experiment
12251 @cindex collected data discarded
12253 This command starts the trace experiment, and begins collecting data.
12254 It has the side effect of discarding all the data collected in the
12255 trace buffer during the previous trace experiment. If any arguments
12256 are supplied, they are taken as a note and stored with the trace
12257 experiment's state. The notes may be arbitrary text, and are
12258 especially useful with disconnected tracing in a multi-user context;
12259 the notes can explain what the trace is doing, supply user contact
12260 information, and so forth.
12262 @kindex tstop [ @var{notes} ]
12263 @cindex stop a running trace experiment
12265 This command stops the trace experiment. If any arguments are
12266 supplied, they are recorded with the experiment as a note. This is
12267 useful if you are stopping a trace started by someone else, for
12268 instance if the trace is interfering with the system's behavior and
12269 needs to be stopped quickly.
12271 @strong{Note}: a trace experiment and data collection may stop
12272 automatically if any tracepoint's passcount is reached
12273 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12276 @cindex status of trace data collection
12277 @cindex trace experiment, status of
12279 This command displays the status of the current trace data
12283 Here is an example of the commands we described so far:
12286 (@value{GDBP}) @b{trace gdb_c_test}
12287 (@value{GDBP}) @b{actions}
12288 Enter actions for tracepoint #1, one per line.
12289 > collect $regs,$locals,$args
12290 > while-stepping 11
12294 (@value{GDBP}) @b{tstart}
12295 [time passes @dots{}]
12296 (@value{GDBP}) @b{tstop}
12299 @anchor{disconnected tracing}
12300 @cindex disconnected tracing
12301 You can choose to continue running the trace experiment even if
12302 @value{GDBN} disconnects from the target, voluntarily or
12303 involuntarily. For commands such as @code{detach}, the debugger will
12304 ask what you want to do with the trace. But for unexpected
12305 terminations (@value{GDBN} crash, network outage), it would be
12306 unfortunate to lose hard-won trace data, so the variable
12307 @code{disconnected-tracing} lets you decide whether the trace should
12308 continue running without @value{GDBN}.
12311 @item set disconnected-tracing on
12312 @itemx set disconnected-tracing off
12313 @kindex set disconnected-tracing
12314 Choose whether a tracing run should continue to run if @value{GDBN}
12315 has disconnected from the target. Note that @code{detach} or
12316 @code{quit} will ask you directly what to do about a running trace no
12317 matter what this variable's setting, so the variable is mainly useful
12318 for handling unexpected situations, such as loss of the network.
12320 @item show disconnected-tracing
12321 @kindex show disconnected-tracing
12322 Show the current choice for disconnected tracing.
12326 When you reconnect to the target, the trace experiment may or may not
12327 still be running; it might have filled the trace buffer in the
12328 meantime, or stopped for one of the other reasons. If it is running,
12329 it will continue after reconnection.
12331 Upon reconnection, the target will upload information about the
12332 tracepoints in effect. @value{GDBN} will then compare that
12333 information to the set of tracepoints currently defined, and attempt
12334 to match them up, allowing for the possibility that the numbers may
12335 have changed due to creation and deletion in the meantime. If one of
12336 the target's tracepoints does not match any in @value{GDBN}, the
12337 debugger will create a new tracepoint, so that you have a number with
12338 which to specify that tracepoint. This matching-up process is
12339 necessarily heuristic, and it may result in useless tracepoints being
12340 created; you may simply delete them if they are of no use.
12342 @cindex circular trace buffer
12343 If your target agent supports a @dfn{circular trace buffer}, then you
12344 can run a trace experiment indefinitely without filling the trace
12345 buffer; when space runs out, the agent deletes already-collected trace
12346 frames, oldest first, until there is enough room to continue
12347 collecting. This is especially useful if your tracepoints are being
12348 hit too often, and your trace gets terminated prematurely because the
12349 buffer is full. To ask for a circular trace buffer, simply set
12350 @samp{circular-trace-buffer} to on. You can set this at any time,
12351 including during tracing; if the agent can do it, it will change
12352 buffer handling on the fly, otherwise it will not take effect until
12356 @item set circular-trace-buffer on
12357 @itemx set circular-trace-buffer off
12358 @kindex set circular-trace-buffer
12359 Choose whether a tracing run should use a linear or circular buffer
12360 for trace data. A linear buffer will not lose any trace data, but may
12361 fill up prematurely, while a circular buffer will discard old trace
12362 data, but it will have always room for the latest tracepoint hits.
12364 @item show circular-trace-buffer
12365 @kindex show circular-trace-buffer
12366 Show the current choice for the trace buffer. Note that this may not
12367 match the agent's current buffer handling, nor is it guaranteed to
12368 match the setting that might have been in effect during a past run,
12369 for instance if you are looking at frames from a trace file.
12374 @item set trace-buffer-size @var{n}
12375 @itemx set trace-buffer-size unlimited
12376 @kindex set trace-buffer-size
12377 Request that the target use a trace buffer of @var{n} bytes. Not all
12378 targets will honor the request; they may have a compiled-in size for
12379 the trace buffer, or some other limitation. Set to a value of
12380 @code{unlimited} or @code{-1} to let the target use whatever size it
12381 likes. This is also the default.
12383 @item show trace-buffer-size
12384 @kindex show trace-buffer-size
12385 Show the current requested size for the trace buffer. Note that this
12386 will only match the actual size if the target supports size-setting,
12387 and was able to handle the requested size. For instance, if the
12388 target can only change buffer size between runs, this variable will
12389 not reflect the change until the next run starts. Use @code{tstatus}
12390 to get a report of the actual buffer size.
12394 @item set trace-user @var{text}
12395 @kindex set trace-user
12397 @item show trace-user
12398 @kindex show trace-user
12400 @item set trace-notes @var{text}
12401 @kindex set trace-notes
12402 Set the trace run's notes.
12404 @item show trace-notes
12405 @kindex show trace-notes
12406 Show the trace run's notes.
12408 @item set trace-stop-notes @var{text}
12409 @kindex set trace-stop-notes
12410 Set the trace run's stop notes. The handling of the note is as for
12411 @code{tstop} arguments; the set command is convenient way to fix a
12412 stop note that is mistaken or incomplete.
12414 @item show trace-stop-notes
12415 @kindex show trace-stop-notes
12416 Show the trace run's stop notes.
12420 @node Tracepoint Restrictions
12421 @subsection Tracepoint Restrictions
12423 @cindex tracepoint restrictions
12424 There are a number of restrictions on the use of tracepoints. As
12425 described above, tracepoint data gathering occurs on the target
12426 without interaction from @value{GDBN}. Thus the full capabilities of
12427 the debugger are not available during data gathering, and then at data
12428 examination time, you will be limited by only having what was
12429 collected. The following items describe some common problems, but it
12430 is not exhaustive, and you may run into additional difficulties not
12436 Tracepoint expressions are intended to gather objects (lvalues). Thus
12437 the full flexibility of GDB's expression evaluator is not available.
12438 You cannot call functions, cast objects to aggregate types, access
12439 convenience variables or modify values (except by assignment to trace
12440 state variables). Some language features may implicitly call
12441 functions (for instance Objective-C fields with accessors), and therefore
12442 cannot be collected either.
12445 Collection of local variables, either individually or in bulk with
12446 @code{$locals} or @code{$args}, during @code{while-stepping} may
12447 behave erratically. The stepping action may enter a new scope (for
12448 instance by stepping into a function), or the location of the variable
12449 may change (for instance it is loaded into a register). The
12450 tracepoint data recorded uses the location information for the
12451 variables that is correct for the tracepoint location. When the
12452 tracepoint is created, it is not possible, in general, to determine
12453 where the steps of a @code{while-stepping} sequence will advance the
12454 program---particularly if a conditional branch is stepped.
12457 Collection of an incompletely-initialized or partially-destroyed object
12458 may result in something that @value{GDBN} cannot display, or displays
12459 in a misleading way.
12462 When @value{GDBN} displays a pointer to character it automatically
12463 dereferences the pointer to also display characters of the string
12464 being pointed to. However, collecting the pointer during tracing does
12465 not automatically collect the string. You need to explicitly
12466 dereference the pointer and provide size information if you want to
12467 collect not only the pointer, but the memory pointed to. For example,
12468 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12472 It is not possible to collect a complete stack backtrace at a
12473 tracepoint. Instead, you may collect the registers and a few hundred
12474 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12475 (adjust to use the name of the actual stack pointer register on your
12476 target architecture, and the amount of stack you wish to capture).
12477 Then the @code{backtrace} command will show a partial backtrace when
12478 using a trace frame. The number of stack frames that can be examined
12479 depends on the sizes of the frames in the collected stack. Note that
12480 if you ask for a block so large that it goes past the bottom of the
12481 stack, the target agent may report an error trying to read from an
12485 If you do not collect registers at a tracepoint, @value{GDBN} can
12486 infer that the value of @code{$pc} must be the same as the address of
12487 the tracepoint and use that when you are looking at a trace frame
12488 for that tracepoint. However, this cannot work if the tracepoint has
12489 multiple locations (for instance if it was set in a function that was
12490 inlined), or if it has a @code{while-stepping} loop. In those cases
12491 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12496 @node Analyze Collected Data
12497 @section Using the Collected Data
12499 After the tracepoint experiment ends, you use @value{GDBN} commands
12500 for examining the trace data. The basic idea is that each tracepoint
12501 collects a trace @dfn{snapshot} every time it is hit and another
12502 snapshot every time it single-steps. All these snapshots are
12503 consecutively numbered from zero and go into a buffer, and you can
12504 examine them later. The way you examine them is to @dfn{focus} on a
12505 specific trace snapshot. When the remote stub is focused on a trace
12506 snapshot, it will respond to all @value{GDBN} requests for memory and
12507 registers by reading from the buffer which belongs to that snapshot,
12508 rather than from @emph{real} memory or registers of the program being
12509 debugged. This means that @strong{all} @value{GDBN} commands
12510 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12511 behave as if we were currently debugging the program state as it was
12512 when the tracepoint occurred. Any requests for data that are not in
12513 the buffer will fail.
12516 * tfind:: How to select a trace snapshot
12517 * tdump:: How to display all data for a snapshot
12518 * save tracepoints:: How to save tracepoints for a future run
12522 @subsection @code{tfind @var{n}}
12525 @cindex select trace snapshot
12526 @cindex find trace snapshot
12527 The basic command for selecting a trace snapshot from the buffer is
12528 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12529 counting from zero. If no argument @var{n} is given, the next
12530 snapshot is selected.
12532 Here are the various forms of using the @code{tfind} command.
12536 Find the first snapshot in the buffer. This is a synonym for
12537 @code{tfind 0} (since 0 is the number of the first snapshot).
12540 Stop debugging trace snapshots, resume @emph{live} debugging.
12543 Same as @samp{tfind none}.
12546 No argument means find the next trace snapshot.
12549 Find the previous trace snapshot before the current one. This permits
12550 retracing earlier steps.
12552 @item tfind tracepoint @var{num}
12553 Find the next snapshot associated with tracepoint @var{num}. Search
12554 proceeds forward from the last examined trace snapshot. If no
12555 argument @var{num} is given, it means find the next snapshot collected
12556 for the same tracepoint as the current snapshot.
12558 @item tfind pc @var{addr}
12559 Find the next snapshot associated with the value @var{addr} of the
12560 program counter. Search proceeds forward from the last examined trace
12561 snapshot. If no argument @var{addr} is given, it means find the next
12562 snapshot with the same value of PC as the current snapshot.
12564 @item tfind outside @var{addr1}, @var{addr2}
12565 Find the next snapshot whose PC is outside the given range of
12566 addresses (exclusive).
12568 @item tfind range @var{addr1}, @var{addr2}
12569 Find the next snapshot whose PC is between @var{addr1} and
12570 @var{addr2} (inclusive).
12572 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12573 Find the next snapshot associated with the source line @var{n}. If
12574 the optional argument @var{file} is given, refer to line @var{n} in
12575 that source file. Search proceeds forward from the last examined
12576 trace snapshot. If no argument @var{n} is given, it means find the
12577 next line other than the one currently being examined; thus saying
12578 @code{tfind line} repeatedly can appear to have the same effect as
12579 stepping from line to line in a @emph{live} debugging session.
12582 The default arguments for the @code{tfind} commands are specifically
12583 designed to make it easy to scan through the trace buffer. For
12584 instance, @code{tfind} with no argument selects the next trace
12585 snapshot, and @code{tfind -} with no argument selects the previous
12586 trace snapshot. So, by giving one @code{tfind} command, and then
12587 simply hitting @key{RET} repeatedly you can examine all the trace
12588 snapshots in order. Or, by saying @code{tfind -} and then hitting
12589 @key{RET} repeatedly you can examine the snapshots in reverse order.
12590 The @code{tfind line} command with no argument selects the snapshot
12591 for the next source line executed. The @code{tfind pc} command with
12592 no argument selects the next snapshot with the same program counter
12593 (PC) as the current frame. The @code{tfind tracepoint} command with
12594 no argument selects the next trace snapshot collected by the same
12595 tracepoint as the current one.
12597 In addition to letting you scan through the trace buffer manually,
12598 these commands make it easy to construct @value{GDBN} scripts that
12599 scan through the trace buffer and print out whatever collected data
12600 you are interested in. Thus, if we want to examine the PC, FP, and SP
12601 registers from each trace frame in the buffer, we can say this:
12604 (@value{GDBP}) @b{tfind start}
12605 (@value{GDBP}) @b{while ($trace_frame != -1)}
12606 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12607 $trace_frame, $pc, $sp, $fp
12611 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12612 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12613 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12614 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12615 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12616 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12617 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12618 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12619 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12620 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12621 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12624 Or, if we want to examine the variable @code{X} at each source line in
12628 (@value{GDBP}) @b{tfind start}
12629 (@value{GDBP}) @b{while ($trace_frame != -1)}
12630 > printf "Frame %d, X == %d\n", $trace_frame, X
12640 @subsection @code{tdump}
12642 @cindex dump all data collected at tracepoint
12643 @cindex tracepoint data, display
12645 This command takes no arguments. It prints all the data collected at
12646 the current trace snapshot.
12649 (@value{GDBP}) @b{trace 444}
12650 (@value{GDBP}) @b{actions}
12651 Enter actions for tracepoint #2, one per line:
12652 > collect $regs, $locals, $args, gdb_long_test
12655 (@value{GDBP}) @b{tstart}
12657 (@value{GDBP}) @b{tfind line 444}
12658 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12660 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12662 (@value{GDBP}) @b{tdump}
12663 Data collected at tracepoint 2, trace frame 1:
12664 d0 0xc4aa0085 -995491707
12668 d4 0x71aea3d 119204413
12671 d7 0x380035 3670069
12672 a0 0x19e24a 1696330
12673 a1 0x3000668 50333288
12675 a3 0x322000 3284992
12676 a4 0x3000698 50333336
12677 a5 0x1ad3cc 1758156
12678 fp 0x30bf3c 0x30bf3c
12679 sp 0x30bf34 0x30bf34
12681 pc 0x20b2c8 0x20b2c8
12685 p = 0x20e5b4 "gdb-test"
12692 gdb_long_test = 17 '\021'
12697 @code{tdump} works by scanning the tracepoint's current collection
12698 actions and printing the value of each expression listed. So
12699 @code{tdump} can fail, if after a run, you change the tracepoint's
12700 actions to mention variables that were not collected during the run.
12702 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12703 uses the collected value of @code{$pc} to distinguish between trace
12704 frames that were collected at the tracepoint hit, and frames that were
12705 collected while stepping. This allows it to correctly choose whether
12706 to display the basic list of collections, or the collections from the
12707 body of the while-stepping loop. However, if @code{$pc} was not collected,
12708 then @code{tdump} will always attempt to dump using the basic collection
12709 list, and may fail if a while-stepping frame does not include all the
12710 same data that is collected at the tracepoint hit.
12711 @c This is getting pretty arcane, example would be good.
12713 @node save tracepoints
12714 @subsection @code{save tracepoints @var{filename}}
12715 @kindex save tracepoints
12716 @kindex save-tracepoints
12717 @cindex save tracepoints for future sessions
12719 This command saves all current tracepoint definitions together with
12720 their actions and passcounts, into a file @file{@var{filename}}
12721 suitable for use in a later debugging session. To read the saved
12722 tracepoint definitions, use the @code{source} command (@pxref{Command
12723 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12724 alias for @w{@code{save tracepoints}}
12726 @node Tracepoint Variables
12727 @section Convenience Variables for Tracepoints
12728 @cindex tracepoint variables
12729 @cindex convenience variables for tracepoints
12732 @vindex $trace_frame
12733 @item (int) $trace_frame
12734 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12735 snapshot is selected.
12737 @vindex $tracepoint
12738 @item (int) $tracepoint
12739 The tracepoint for the current trace snapshot.
12741 @vindex $trace_line
12742 @item (int) $trace_line
12743 The line number for the current trace snapshot.
12745 @vindex $trace_file
12746 @item (char []) $trace_file
12747 The source file for the current trace snapshot.
12749 @vindex $trace_func
12750 @item (char []) $trace_func
12751 The name of the function containing @code{$tracepoint}.
12754 Note: @code{$trace_file} is not suitable for use in @code{printf},
12755 use @code{output} instead.
12757 Here's a simple example of using these convenience variables for
12758 stepping through all the trace snapshots and printing some of their
12759 data. Note that these are not the same as trace state variables,
12760 which are managed by the target.
12763 (@value{GDBP}) @b{tfind start}
12765 (@value{GDBP}) @b{while $trace_frame != -1}
12766 > output $trace_file
12767 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12773 @section Using Trace Files
12774 @cindex trace files
12776 In some situations, the target running a trace experiment may no
12777 longer be available; perhaps it crashed, or the hardware was needed
12778 for a different activity. To handle these cases, you can arrange to
12779 dump the trace data into a file, and later use that file as a source
12780 of trace data, via the @code{target tfile} command.
12785 @item tsave [ -r ] @var{filename}
12786 @itemx tsave [-ctf] @var{dirname}
12787 Save the trace data to @var{filename}. By default, this command
12788 assumes that @var{filename} refers to the host filesystem, so if
12789 necessary @value{GDBN} will copy raw trace data up from the target and
12790 then save it. If the target supports it, you can also supply the
12791 optional argument @code{-r} (``remote'') to direct the target to save
12792 the data directly into @var{filename} in its own filesystem, which may be
12793 more efficient if the trace buffer is very large. (Note, however, that
12794 @code{target tfile} can only read from files accessible to the host.)
12795 By default, this command will save trace frame in tfile format.
12796 You can supply the optional argument @code{-ctf} to save date in CTF
12797 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12798 that can be shared by multiple debugging and tracing tools. Please go to
12799 @indicateurl{http://www.efficios.com/ctf} to get more information.
12801 @kindex target tfile
12805 @item target tfile @var{filename}
12806 @itemx target ctf @var{dirname}
12807 Use the file named @var{filename} or directory named @var{dirname} as
12808 a source of trace data. Commands that examine data work as they do with
12809 a live target, but it is not possible to run any new trace experiments.
12810 @code{tstatus} will report the state of the trace run at the moment
12811 the data was saved, as well as the current trace frame you are examining.
12812 @var{filename} or @var{dirname} must be on a filesystem accessible to
12816 (@value{GDBP}) target ctf ctf.ctf
12817 (@value{GDBP}) tfind
12818 Found trace frame 0, tracepoint 2
12819 39 ++a; /* set tracepoint 1 here */
12820 (@value{GDBP}) tdump
12821 Data collected at tracepoint 2, trace frame 0:
12825 c = @{"123", "456", "789", "123", "456", "789"@}
12826 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12834 @chapter Debugging Programs That Use Overlays
12837 If your program is too large to fit completely in your target system's
12838 memory, you can sometimes use @dfn{overlays} to work around this
12839 problem. @value{GDBN} provides some support for debugging programs that
12843 * How Overlays Work:: A general explanation of overlays.
12844 * Overlay Commands:: Managing overlays in @value{GDBN}.
12845 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12846 mapped by asking the inferior.
12847 * Overlay Sample Program:: A sample program using overlays.
12850 @node How Overlays Work
12851 @section How Overlays Work
12852 @cindex mapped overlays
12853 @cindex unmapped overlays
12854 @cindex load address, overlay's
12855 @cindex mapped address
12856 @cindex overlay area
12858 Suppose you have a computer whose instruction address space is only 64
12859 kilobytes long, but which has much more memory which can be accessed by
12860 other means: special instructions, segment registers, or memory
12861 management hardware, for example. Suppose further that you want to
12862 adapt a program which is larger than 64 kilobytes to run on this system.
12864 One solution is to identify modules of your program which are relatively
12865 independent, and need not call each other directly; call these modules
12866 @dfn{overlays}. Separate the overlays from the main program, and place
12867 their machine code in the larger memory. Place your main program in
12868 instruction memory, but leave at least enough space there to hold the
12869 largest overlay as well.
12871 Now, to call a function located in an overlay, you must first copy that
12872 overlay's machine code from the large memory into the space set aside
12873 for it in the instruction memory, and then jump to its entry point
12876 @c NB: In the below the mapped area's size is greater or equal to the
12877 @c size of all overlays. This is intentional to remind the developer
12878 @c that overlays don't necessarily need to be the same size.
12882 Data Instruction Larger
12883 Address Space Address Space Address Space
12884 +-----------+ +-----------+ +-----------+
12886 +-----------+ +-----------+ +-----------+<-- overlay 1
12887 | program | | main | .----| overlay 1 | load address
12888 | variables | | program | | +-----------+
12889 | and heap | | | | | |
12890 +-----------+ | | | +-----------+<-- overlay 2
12891 | | +-----------+ | | | load address
12892 +-----------+ | | | .-| overlay 2 |
12894 mapped --->+-----------+ | | +-----------+
12895 address | | | | | |
12896 | overlay | <-' | | |
12897 | area | <---' +-----------+<-- overlay 3
12898 | | <---. | | load address
12899 +-----------+ `--| overlay 3 |
12906 @anchor{A code overlay}A code overlay
12910 The diagram (@pxref{A code overlay}) shows a system with separate data
12911 and instruction address spaces. To map an overlay, the program copies
12912 its code from the larger address space to the instruction address space.
12913 Since the overlays shown here all use the same mapped address, only one
12914 may be mapped at a time. For a system with a single address space for
12915 data and instructions, the diagram would be similar, except that the
12916 program variables and heap would share an address space with the main
12917 program and the overlay area.
12919 An overlay loaded into instruction memory and ready for use is called a
12920 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12921 instruction memory. An overlay not present (or only partially present)
12922 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12923 is its address in the larger memory. The mapped address is also called
12924 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12925 called the @dfn{load memory address}, or @dfn{LMA}.
12927 Unfortunately, overlays are not a completely transparent way to adapt a
12928 program to limited instruction memory. They introduce a new set of
12929 global constraints you must keep in mind as you design your program:
12934 Before calling or returning to a function in an overlay, your program
12935 must make sure that overlay is actually mapped. Otherwise, the call or
12936 return will transfer control to the right address, but in the wrong
12937 overlay, and your program will probably crash.
12940 If the process of mapping an overlay is expensive on your system, you
12941 will need to choose your overlays carefully to minimize their effect on
12942 your program's performance.
12945 The executable file you load onto your system must contain each
12946 overlay's instructions, appearing at the overlay's load address, not its
12947 mapped address. However, each overlay's instructions must be relocated
12948 and its symbols defined as if the overlay were at its mapped address.
12949 You can use GNU linker scripts to specify different load and relocation
12950 addresses for pieces of your program; see @ref{Overlay Description,,,
12951 ld.info, Using ld: the GNU linker}.
12954 The procedure for loading executable files onto your system must be able
12955 to load their contents into the larger address space as well as the
12956 instruction and data spaces.
12960 The overlay system described above is rather simple, and could be
12961 improved in many ways:
12966 If your system has suitable bank switch registers or memory management
12967 hardware, you could use those facilities to make an overlay's load area
12968 contents simply appear at their mapped address in instruction space.
12969 This would probably be faster than copying the overlay to its mapped
12970 area in the usual way.
12973 If your overlays are small enough, you could set aside more than one
12974 overlay area, and have more than one overlay mapped at a time.
12977 You can use overlays to manage data, as well as instructions. In
12978 general, data overlays are even less transparent to your design than
12979 code overlays: whereas code overlays only require care when you call or
12980 return to functions, data overlays require care every time you access
12981 the data. Also, if you change the contents of a data overlay, you
12982 must copy its contents back out to its load address before you can copy a
12983 different data overlay into the same mapped area.
12988 @node Overlay Commands
12989 @section Overlay Commands
12991 To use @value{GDBN}'s overlay support, each overlay in your program must
12992 correspond to a separate section of the executable file. The section's
12993 virtual memory address and load memory address must be the overlay's
12994 mapped and load addresses. Identifying overlays with sections allows
12995 @value{GDBN} to determine the appropriate address of a function or
12996 variable, depending on whether the overlay is mapped or not.
12998 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12999 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13004 Disable @value{GDBN}'s overlay support. When overlay support is
13005 disabled, @value{GDBN} assumes that all functions and variables are
13006 always present at their mapped addresses. By default, @value{GDBN}'s
13007 overlay support is disabled.
13009 @item overlay manual
13010 @cindex manual overlay debugging
13011 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13012 relies on you to tell it which overlays are mapped, and which are not,
13013 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13014 commands described below.
13016 @item overlay map-overlay @var{overlay}
13017 @itemx overlay map @var{overlay}
13018 @cindex map an overlay
13019 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13020 be the name of the object file section containing the overlay. When an
13021 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13022 functions and variables at their mapped addresses. @value{GDBN} assumes
13023 that any other overlays whose mapped ranges overlap that of
13024 @var{overlay} are now unmapped.
13026 @item overlay unmap-overlay @var{overlay}
13027 @itemx overlay unmap @var{overlay}
13028 @cindex unmap an overlay
13029 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13030 must be the name of the object file section containing the overlay.
13031 When an overlay is unmapped, @value{GDBN} assumes it can find the
13032 overlay's functions and variables at their load addresses.
13035 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13036 consults a data structure the overlay manager maintains in the inferior
13037 to see which overlays are mapped. For details, see @ref{Automatic
13038 Overlay Debugging}.
13040 @item overlay load-target
13041 @itemx overlay load
13042 @cindex reloading the overlay table
13043 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13044 re-reads the table @value{GDBN} automatically each time the inferior
13045 stops, so this command should only be necessary if you have changed the
13046 overlay mapping yourself using @value{GDBN}. This command is only
13047 useful when using automatic overlay debugging.
13049 @item overlay list-overlays
13050 @itemx overlay list
13051 @cindex listing mapped overlays
13052 Display a list of the overlays currently mapped, along with their mapped
13053 addresses, load addresses, and sizes.
13057 Normally, when @value{GDBN} prints a code address, it includes the name
13058 of the function the address falls in:
13061 (@value{GDBP}) print main
13062 $3 = @{int ()@} 0x11a0 <main>
13065 When overlay debugging is enabled, @value{GDBN} recognizes code in
13066 unmapped overlays, and prints the names of unmapped functions with
13067 asterisks around them. For example, if @code{foo} is a function in an
13068 unmapped overlay, @value{GDBN} prints it this way:
13071 (@value{GDBP}) overlay list
13072 No sections are mapped.
13073 (@value{GDBP}) print foo
13074 $5 = @{int (int)@} 0x100000 <*foo*>
13077 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13081 (@value{GDBP}) overlay list
13082 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13083 mapped at 0x1016 - 0x104a
13084 (@value{GDBP}) print foo
13085 $6 = @{int (int)@} 0x1016 <foo>
13088 When overlay debugging is enabled, @value{GDBN} can find the correct
13089 address for functions and variables in an overlay, whether or not the
13090 overlay is mapped. This allows most @value{GDBN} commands, like
13091 @code{break} and @code{disassemble}, to work normally, even on unmapped
13092 code. However, @value{GDBN}'s breakpoint support has some limitations:
13096 @cindex breakpoints in overlays
13097 @cindex overlays, setting breakpoints in
13098 You can set breakpoints in functions in unmapped overlays, as long as
13099 @value{GDBN} can write to the overlay at its load address.
13101 @value{GDBN} can not set hardware or simulator-based breakpoints in
13102 unmapped overlays. However, if you set a breakpoint at the end of your
13103 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13104 you are using manual overlay management), @value{GDBN} will re-set its
13105 breakpoints properly.
13109 @node Automatic Overlay Debugging
13110 @section Automatic Overlay Debugging
13111 @cindex automatic overlay debugging
13113 @value{GDBN} can automatically track which overlays are mapped and which
13114 are not, given some simple co-operation from the overlay manager in the
13115 inferior. If you enable automatic overlay debugging with the
13116 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13117 looks in the inferior's memory for certain variables describing the
13118 current state of the overlays.
13120 Here are the variables your overlay manager must define to support
13121 @value{GDBN}'s automatic overlay debugging:
13125 @item @code{_ovly_table}:
13126 This variable must be an array of the following structures:
13131 /* The overlay's mapped address. */
13134 /* The size of the overlay, in bytes. */
13135 unsigned long size;
13137 /* The overlay's load address. */
13140 /* Non-zero if the overlay is currently mapped;
13142 unsigned long mapped;
13146 @item @code{_novlys}:
13147 This variable must be a four-byte signed integer, holding the total
13148 number of elements in @code{_ovly_table}.
13152 To decide whether a particular overlay is mapped or not, @value{GDBN}
13153 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13154 @code{lma} members equal the VMA and LMA of the overlay's section in the
13155 executable file. When @value{GDBN} finds a matching entry, it consults
13156 the entry's @code{mapped} member to determine whether the overlay is
13159 In addition, your overlay manager may define a function called
13160 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13161 will silently set a breakpoint there. If the overlay manager then
13162 calls this function whenever it has changed the overlay table, this
13163 will enable @value{GDBN} to accurately keep track of which overlays
13164 are in program memory, and update any breakpoints that may be set
13165 in overlays. This will allow breakpoints to work even if the
13166 overlays are kept in ROM or other non-writable memory while they
13167 are not being executed.
13169 @node Overlay Sample Program
13170 @section Overlay Sample Program
13171 @cindex overlay example program
13173 When linking a program which uses overlays, you must place the overlays
13174 at their load addresses, while relocating them to run at their mapped
13175 addresses. To do this, you must write a linker script (@pxref{Overlay
13176 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13177 since linker scripts are specific to a particular host system, target
13178 architecture, and target memory layout, this manual cannot provide
13179 portable sample code demonstrating @value{GDBN}'s overlay support.
13181 However, the @value{GDBN} source distribution does contain an overlaid
13182 program, with linker scripts for a few systems, as part of its test
13183 suite. The program consists of the following files from
13184 @file{gdb/testsuite/gdb.base}:
13188 The main program file.
13190 A simple overlay manager, used by @file{overlays.c}.
13195 Overlay modules, loaded and used by @file{overlays.c}.
13198 Linker scripts for linking the test program on the @code{d10v-elf}
13199 and @code{m32r-elf} targets.
13202 You can build the test program using the @code{d10v-elf} GCC
13203 cross-compiler like this:
13206 $ d10v-elf-gcc -g -c overlays.c
13207 $ d10v-elf-gcc -g -c ovlymgr.c
13208 $ d10v-elf-gcc -g -c foo.c
13209 $ d10v-elf-gcc -g -c bar.c
13210 $ d10v-elf-gcc -g -c baz.c
13211 $ d10v-elf-gcc -g -c grbx.c
13212 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13213 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13216 The build process is identical for any other architecture, except that
13217 you must substitute the appropriate compiler and linker script for the
13218 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13222 @chapter Using @value{GDBN} with Different Languages
13225 Although programming languages generally have common aspects, they are
13226 rarely expressed in the same manner. For instance, in ANSI C,
13227 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13228 Modula-2, it is accomplished by @code{p^}. Values can also be
13229 represented (and displayed) differently. Hex numbers in C appear as
13230 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13232 @cindex working language
13233 Language-specific information is built into @value{GDBN} for some languages,
13234 allowing you to express operations like the above in your program's
13235 native language, and allowing @value{GDBN} to output values in a manner
13236 consistent with the syntax of your program's native language. The
13237 language you use to build expressions is called the @dfn{working
13241 * Setting:: Switching between source languages
13242 * Show:: Displaying the language
13243 * Checks:: Type and range checks
13244 * Supported Languages:: Supported languages
13245 * Unsupported Languages:: Unsupported languages
13249 @section Switching Between Source Languages
13251 There are two ways to control the working language---either have @value{GDBN}
13252 set it automatically, or select it manually yourself. You can use the
13253 @code{set language} command for either purpose. On startup, @value{GDBN}
13254 defaults to setting the language automatically. The working language is
13255 used to determine how expressions you type are interpreted, how values
13258 In addition to the working language, every source file that
13259 @value{GDBN} knows about has its own working language. For some object
13260 file formats, the compiler might indicate which language a particular
13261 source file is in. However, most of the time @value{GDBN} infers the
13262 language from the name of the file. The language of a source file
13263 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13264 show each frame appropriately for its own language. There is no way to
13265 set the language of a source file from within @value{GDBN}, but you can
13266 set the language associated with a filename extension. @xref{Show, ,
13267 Displaying the Language}.
13269 This is most commonly a problem when you use a program, such
13270 as @code{cfront} or @code{f2c}, that generates C but is written in
13271 another language. In that case, make the
13272 program use @code{#line} directives in its C output; that way
13273 @value{GDBN} will know the correct language of the source code of the original
13274 program, and will display that source code, not the generated C code.
13277 * Filenames:: Filename extensions and languages.
13278 * Manually:: Setting the working language manually
13279 * Automatically:: Having @value{GDBN} infer the source language
13283 @subsection List of Filename Extensions and Languages
13285 If a source file name ends in one of the following extensions, then
13286 @value{GDBN} infers that its language is the one indicated.
13304 C@t{++} source file
13310 Objective-C source file
13314 Fortran source file
13317 Modula-2 source file
13321 Assembler source file. This actually behaves almost like C, but
13322 @value{GDBN} does not skip over function prologues when stepping.
13325 In addition, you may set the language associated with a filename
13326 extension. @xref{Show, , Displaying the Language}.
13329 @subsection Setting the Working Language
13331 If you allow @value{GDBN} to set the language automatically,
13332 expressions are interpreted the same way in your debugging session and
13335 @kindex set language
13336 If you wish, you may set the language manually. To do this, issue the
13337 command @samp{set language @var{lang}}, where @var{lang} is the name of
13338 a language, such as
13339 @code{c} or @code{modula-2}.
13340 For a list of the supported languages, type @samp{set language}.
13342 Setting the language manually prevents @value{GDBN} from updating the working
13343 language automatically. This can lead to confusion if you try
13344 to debug a program when the working language is not the same as the
13345 source language, when an expression is acceptable to both
13346 languages---but means different things. For instance, if the current
13347 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13355 might not have the effect you intended. In C, this means to add
13356 @code{b} and @code{c} and place the result in @code{a}. The result
13357 printed would be the value of @code{a}. In Modula-2, this means to compare
13358 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13360 @node Automatically
13361 @subsection Having @value{GDBN} Infer the Source Language
13363 To have @value{GDBN} set the working language automatically, use
13364 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13365 then infers the working language. That is, when your program stops in a
13366 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13367 working language to the language recorded for the function in that
13368 frame. If the language for a frame is unknown (that is, if the function
13369 or block corresponding to the frame was defined in a source file that
13370 does not have a recognized extension), the current working language is
13371 not changed, and @value{GDBN} issues a warning.
13373 This may not seem necessary for most programs, which are written
13374 entirely in one source language. However, program modules and libraries
13375 written in one source language can be used by a main program written in
13376 a different source language. Using @samp{set language auto} in this
13377 case frees you from having to set the working language manually.
13380 @section Displaying the Language
13382 The following commands help you find out which language is the
13383 working language, and also what language source files were written in.
13386 @item show language
13387 @anchor{show language}
13388 @kindex show language
13389 Display the current working language. This is the
13390 language you can use with commands such as @code{print} to
13391 build and compute expressions that may involve variables in your program.
13394 @kindex info frame@r{, show the source language}
13395 Display the source language for this frame. This language becomes the
13396 working language if you use an identifier from this frame.
13397 @xref{Frame Info, ,Information about a Frame}, to identify the other
13398 information listed here.
13401 @kindex info source@r{, show the source language}
13402 Display the source language of this source file.
13403 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13404 information listed here.
13407 In unusual circumstances, you may have source files with extensions
13408 not in the standard list. You can then set the extension associated
13409 with a language explicitly:
13412 @item set extension-language @var{ext} @var{language}
13413 @kindex set extension-language
13414 Tell @value{GDBN} that source files with extension @var{ext} are to be
13415 assumed as written in the source language @var{language}.
13417 @item info extensions
13418 @kindex info extensions
13419 List all the filename extensions and the associated languages.
13423 @section Type and Range Checking
13425 Some languages are designed to guard you against making seemingly common
13426 errors through a series of compile- and run-time checks. These include
13427 checking the type of arguments to functions and operators and making
13428 sure mathematical overflows are caught at run time. Checks such as
13429 these help to ensure a program's correctness once it has been compiled
13430 by eliminating type mismatches and providing active checks for range
13431 errors when your program is running.
13433 By default @value{GDBN} checks for these errors according to the
13434 rules of the current source language. Although @value{GDBN} does not check
13435 the statements in your program, it can check expressions entered directly
13436 into @value{GDBN} for evaluation via the @code{print} command, for example.
13439 * Type Checking:: An overview of type checking
13440 * Range Checking:: An overview of range checking
13443 @cindex type checking
13444 @cindex checks, type
13445 @node Type Checking
13446 @subsection An Overview of Type Checking
13448 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13449 arguments to operators and functions have to be of the correct type,
13450 otherwise an error occurs. These checks prevent type mismatch
13451 errors from ever causing any run-time problems. For example,
13454 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13456 (@value{GDBP}) print obj.my_method (0)
13459 (@value{GDBP}) print obj.my_method (0x1234)
13460 Cannot resolve method klass::my_method to any overloaded instance
13463 The second example fails because in C@t{++} the integer constant
13464 @samp{0x1234} is not type-compatible with the pointer parameter type.
13466 For the expressions you use in @value{GDBN} commands, you can tell
13467 @value{GDBN} to not enforce strict type checking or
13468 to treat any mismatches as errors and abandon the expression;
13469 When type checking is disabled, @value{GDBN} successfully evaluates
13470 expressions like the second example above.
13472 Even if type checking is off, there may be other reasons
13473 related to type that prevent @value{GDBN} from evaluating an expression.
13474 For instance, @value{GDBN} does not know how to add an @code{int} and
13475 a @code{struct foo}. These particular type errors have nothing to do
13476 with the language in use and usually arise from expressions which make
13477 little sense to evaluate anyway.
13479 @value{GDBN} provides some additional commands for controlling type checking:
13481 @kindex set check type
13482 @kindex show check type
13484 @item set check type on
13485 @itemx set check type off
13486 Set strict type checking on or off. If any type mismatches occur in
13487 evaluating an expression while type checking is on, @value{GDBN} prints a
13488 message and aborts evaluation of the expression.
13490 @item show check type
13491 Show the current setting of type checking and whether @value{GDBN}
13492 is enforcing strict type checking rules.
13495 @cindex range checking
13496 @cindex checks, range
13497 @node Range Checking
13498 @subsection An Overview of Range Checking
13500 In some languages (such as Modula-2), it is an error to exceed the
13501 bounds of a type; this is enforced with run-time checks. Such range
13502 checking is meant to ensure program correctness by making sure
13503 computations do not overflow, or indices on an array element access do
13504 not exceed the bounds of the array.
13506 For expressions you use in @value{GDBN} commands, you can tell
13507 @value{GDBN} to treat range errors in one of three ways: ignore them,
13508 always treat them as errors and abandon the expression, or issue
13509 warnings but evaluate the expression anyway.
13511 A range error can result from numerical overflow, from exceeding an
13512 array index bound, or when you type a constant that is not a member
13513 of any type. Some languages, however, do not treat overflows as an
13514 error. In many implementations of C, mathematical overflow causes the
13515 result to ``wrap around'' to lower values---for example, if @var{m} is
13516 the largest integer value, and @var{s} is the smallest, then
13519 @var{m} + 1 @result{} @var{s}
13522 This, too, is specific to individual languages, and in some cases
13523 specific to individual compilers or machines. @xref{Supported Languages, ,
13524 Supported Languages}, for further details on specific languages.
13526 @value{GDBN} provides some additional commands for controlling the range checker:
13528 @kindex set check range
13529 @kindex show check range
13531 @item set check range auto
13532 Set range checking on or off based on the current working language.
13533 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13536 @item set check range on
13537 @itemx set check range off
13538 Set range checking on or off, overriding the default setting for the
13539 current working language. A warning is issued if the setting does not
13540 match the language default. If a range error occurs and range checking is on,
13541 then a message is printed and evaluation of the expression is aborted.
13543 @item set check range warn
13544 Output messages when the @value{GDBN} range checker detects a range error,
13545 but attempt to evaluate the expression anyway. Evaluating the
13546 expression may still be impossible for other reasons, such as accessing
13547 memory that the process does not own (a typical example from many Unix
13551 Show the current setting of the range checker, and whether or not it is
13552 being set automatically by @value{GDBN}.
13555 @node Supported Languages
13556 @section Supported Languages
13558 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13559 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13560 @c This is false ...
13561 Some @value{GDBN} features may be used in expressions regardless of the
13562 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13563 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13564 ,Expressions}) can be used with the constructs of any supported
13567 The following sections detail to what degree each source language is
13568 supported by @value{GDBN}. These sections are not meant to be language
13569 tutorials or references, but serve only as a reference guide to what the
13570 @value{GDBN} expression parser accepts, and what input and output
13571 formats should look like for different languages. There are many good
13572 books written on each of these languages; please look to these for a
13573 language reference or tutorial.
13576 * C:: C and C@t{++}
13579 * Objective-C:: Objective-C
13580 * OpenCL C:: OpenCL C
13581 * Fortran:: Fortran
13583 * Modula-2:: Modula-2
13588 @subsection C and C@t{++}
13590 @cindex C and C@t{++}
13591 @cindex expressions in C or C@t{++}
13593 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13594 to both languages. Whenever this is the case, we discuss those languages
13598 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13599 @cindex @sc{gnu} C@t{++}
13600 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13601 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13602 effectively, you must compile your C@t{++} programs with a supported
13603 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13604 compiler (@code{aCC}).
13607 * C Operators:: C and C@t{++} operators
13608 * C Constants:: C and C@t{++} constants
13609 * C Plus Plus Expressions:: C@t{++} expressions
13610 * C Defaults:: Default settings for C and C@t{++}
13611 * C Checks:: C and C@t{++} type and range checks
13612 * Debugging C:: @value{GDBN} and C
13613 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13614 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13618 @subsubsection C and C@t{++} Operators
13620 @cindex C and C@t{++} operators
13622 Operators must be defined on values of specific types. For instance,
13623 @code{+} is defined on numbers, but not on structures. Operators are
13624 often defined on groups of types.
13626 For the purposes of C and C@t{++}, the following definitions hold:
13631 @emph{Integral types} include @code{int} with any of its storage-class
13632 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13635 @emph{Floating-point types} include @code{float}, @code{double}, and
13636 @code{long double} (if supported by the target platform).
13639 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13642 @emph{Scalar types} include all of the above.
13647 The following operators are supported. They are listed here
13648 in order of increasing precedence:
13652 The comma or sequencing operator. Expressions in a comma-separated list
13653 are evaluated from left to right, with the result of the entire
13654 expression being the last expression evaluated.
13657 Assignment. The value of an assignment expression is the value
13658 assigned. Defined on scalar types.
13661 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13662 and translated to @w{@code{@var{a} = @var{a op b}}}.
13663 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13664 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13665 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13668 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13669 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13673 Logical @sc{or}. Defined on integral types.
13676 Logical @sc{and}. Defined on integral types.
13679 Bitwise @sc{or}. Defined on integral types.
13682 Bitwise exclusive-@sc{or}. Defined on integral types.
13685 Bitwise @sc{and}. Defined on integral types.
13688 Equality and inequality. Defined on scalar types. The value of these
13689 expressions is 0 for false and non-zero for true.
13691 @item <@r{, }>@r{, }<=@r{, }>=
13692 Less than, greater than, less than or equal, greater than or equal.
13693 Defined on scalar types. The value of these expressions is 0 for false
13694 and non-zero for true.
13697 left shift, and right shift. Defined on integral types.
13700 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13703 Addition and subtraction. Defined on integral types, floating-point types and
13706 @item *@r{, }/@r{, }%
13707 Multiplication, division, and modulus. Multiplication and division are
13708 defined on integral and floating-point types. Modulus is defined on
13712 Increment and decrement. When appearing before a variable, the
13713 operation is performed before the variable is used in an expression;
13714 when appearing after it, the variable's value is used before the
13715 operation takes place.
13718 Pointer dereferencing. Defined on pointer types. Same precedence as
13722 Address operator. Defined on variables. Same precedence as @code{++}.
13724 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13725 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13726 to examine the address
13727 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13731 Negative. Defined on integral and floating-point types. Same
13732 precedence as @code{++}.
13735 Logical negation. Defined on integral types. Same precedence as
13739 Bitwise complement operator. Defined on integral types. Same precedence as
13744 Structure member, and pointer-to-structure member. For convenience,
13745 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13746 pointer based on the stored type information.
13747 Defined on @code{struct} and @code{union} data.
13750 Dereferences of pointers to members.
13753 Array indexing. @code{@var{a}[@var{i}]} is defined as
13754 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13757 Function parameter list. Same precedence as @code{->}.
13760 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13761 and @code{class} types.
13764 Doubled colons also represent the @value{GDBN} scope operator
13765 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13769 If an operator is redefined in the user code, @value{GDBN} usually
13770 attempts to invoke the redefined version instead of using the operator's
13771 predefined meaning.
13774 @subsubsection C and C@t{++} Constants
13776 @cindex C and C@t{++} constants
13778 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13783 Integer constants are a sequence of digits. Octal constants are
13784 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13785 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13786 @samp{l}, specifying that the constant should be treated as a
13790 Floating point constants are a sequence of digits, followed by a decimal
13791 point, followed by a sequence of digits, and optionally followed by an
13792 exponent. An exponent is of the form:
13793 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13794 sequence of digits. The @samp{+} is optional for positive exponents.
13795 A floating-point constant may also end with a letter @samp{f} or
13796 @samp{F}, specifying that the constant should be treated as being of
13797 the @code{float} (as opposed to the default @code{double}) type; or with
13798 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13802 Enumerated constants consist of enumerated identifiers, or their
13803 integral equivalents.
13806 Character constants are a single character surrounded by single quotes
13807 (@code{'}), or a number---the ordinal value of the corresponding character
13808 (usually its @sc{ascii} value). Within quotes, the single character may
13809 be represented by a letter or by @dfn{escape sequences}, which are of
13810 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13811 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13812 @samp{@var{x}} is a predefined special character---for example,
13813 @samp{\n} for newline.
13815 Wide character constants can be written by prefixing a character
13816 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13817 form of @samp{x}. The target wide character set is used when
13818 computing the value of this constant (@pxref{Character Sets}).
13821 String constants are a sequence of character constants surrounded by
13822 double quotes (@code{"}). Any valid character constant (as described
13823 above) may appear. Double quotes within the string must be preceded by
13824 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13827 Wide string constants can be written by prefixing a string constant
13828 with @samp{L}, as in C. The target wide character set is used when
13829 computing the value of this constant (@pxref{Character Sets}).
13832 Pointer constants are an integral value. You can also write pointers
13833 to constants using the C operator @samp{&}.
13836 Array constants are comma-separated lists surrounded by braces @samp{@{}
13837 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13838 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13839 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13842 @node C Plus Plus Expressions
13843 @subsubsection C@t{++} Expressions
13845 @cindex expressions in C@t{++}
13846 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13848 @cindex debugging C@t{++} programs
13849 @cindex C@t{++} compilers
13850 @cindex debug formats and C@t{++}
13851 @cindex @value{NGCC} and C@t{++}
13853 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13854 the proper compiler and the proper debug format. Currently,
13855 @value{GDBN} works best when debugging C@t{++} code that is compiled
13856 with the most recent version of @value{NGCC} possible. The DWARF
13857 debugging format is preferred; @value{NGCC} defaults to this on most
13858 popular platforms. Other compilers and/or debug formats are likely to
13859 work badly or not at all when using @value{GDBN} to debug C@t{++}
13860 code. @xref{Compilation}.
13865 @cindex member functions
13867 Member function calls are allowed; you can use expressions like
13870 count = aml->GetOriginal(x, y)
13873 @vindex this@r{, inside C@t{++} member functions}
13874 @cindex namespace in C@t{++}
13876 While a member function is active (in the selected stack frame), your
13877 expressions have the same namespace available as the member function;
13878 that is, @value{GDBN} allows implicit references to the class instance
13879 pointer @code{this} following the same rules as C@t{++}. @code{using}
13880 declarations in the current scope are also respected by @value{GDBN}.
13882 @cindex call overloaded functions
13883 @cindex overloaded functions, calling
13884 @cindex type conversions in C@t{++}
13886 You can call overloaded functions; @value{GDBN} resolves the function
13887 call to the right definition, with some restrictions. @value{GDBN} does not
13888 perform overload resolution involving user-defined type conversions,
13889 calls to constructors, or instantiations of templates that do not exist
13890 in the program. It also cannot handle ellipsis argument lists or
13893 It does perform integral conversions and promotions, floating-point
13894 promotions, arithmetic conversions, pointer conversions, conversions of
13895 class objects to base classes, and standard conversions such as those of
13896 functions or arrays to pointers; it requires an exact match on the
13897 number of function arguments.
13899 Overload resolution is always performed, unless you have specified
13900 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13901 ,@value{GDBN} Features for C@t{++}}.
13903 You must specify @code{set overload-resolution off} in order to use an
13904 explicit function signature to call an overloaded function, as in
13906 p 'foo(char,int)'('x', 13)
13909 The @value{GDBN} command-completion facility can simplify this;
13910 see @ref{Completion, ,Command Completion}.
13912 @cindex reference declarations
13914 @value{GDBN} understands variables declared as C@t{++} references; you can use
13915 them in expressions just as you do in C@t{++} source---they are automatically
13918 In the parameter list shown when @value{GDBN} displays a frame, the values of
13919 reference variables are not displayed (unlike other variables); this
13920 avoids clutter, since references are often used for large structures.
13921 The @emph{address} of a reference variable is always shown, unless
13922 you have specified @samp{set print address off}.
13925 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13926 expressions can use it just as expressions in your program do. Since
13927 one scope may be defined in another, you can use @code{::} repeatedly if
13928 necessary, for example in an expression like
13929 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13930 resolving name scope by reference to source files, in both C and C@t{++}
13931 debugging (@pxref{Variables, ,Program Variables}).
13934 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13939 @subsubsection C and C@t{++} Defaults
13941 @cindex C and C@t{++} defaults
13943 If you allow @value{GDBN} to set range checking automatically, it
13944 defaults to @code{off} whenever the working language changes to
13945 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13946 selects the working language.
13948 If you allow @value{GDBN} to set the language automatically, it
13949 recognizes source files whose names end with @file{.c}, @file{.C}, or
13950 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13951 these files, it sets the working language to C or C@t{++}.
13952 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13953 for further details.
13956 @subsubsection C and C@t{++} Type and Range Checks
13958 @cindex C and C@t{++} checks
13960 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13961 checking is used. However, if you turn type checking off, @value{GDBN}
13962 will allow certain non-standard conversions, such as promoting integer
13963 constants to pointers.
13965 Range checking, if turned on, is done on mathematical operations. Array
13966 indices are not checked, since they are often used to index a pointer
13967 that is not itself an array.
13970 @subsubsection @value{GDBN} and C
13972 The @code{set print union} and @code{show print union} commands apply to
13973 the @code{union} type. When set to @samp{on}, any @code{union} that is
13974 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13975 appears as @samp{@{...@}}.
13977 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13978 with pointers and a memory allocation function. @xref{Expressions,
13981 @node Debugging C Plus Plus
13982 @subsubsection @value{GDBN} Features for C@t{++}
13984 @cindex commands for C@t{++}
13986 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13987 designed specifically for use with C@t{++}. Here is a summary:
13990 @cindex break in overloaded functions
13991 @item @r{breakpoint menus}
13992 When you want a breakpoint in a function whose name is overloaded,
13993 @value{GDBN} has the capability to display a menu of possible breakpoint
13994 locations to help you specify which function definition you want.
13995 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13997 @cindex overloading in C@t{++}
13998 @item rbreak @var{regex}
13999 Setting breakpoints using regular expressions is helpful for setting
14000 breakpoints on overloaded functions that are not members of any special
14002 @xref{Set Breaks, ,Setting Breakpoints}.
14004 @cindex C@t{++} exception handling
14006 @itemx catch rethrow
14008 Debug C@t{++} exception handling using these commands. @xref{Set
14009 Catchpoints, , Setting Catchpoints}.
14011 @cindex inheritance
14012 @item ptype @var{typename}
14013 Print inheritance relationships as well as other information for type
14015 @xref{Symbols, ,Examining the Symbol Table}.
14017 @item info vtbl @var{expression}.
14018 The @code{info vtbl} command can be used to display the virtual
14019 method tables of the object computed by @var{expression}. This shows
14020 one entry per virtual table; there may be multiple virtual tables when
14021 multiple inheritance is in use.
14023 @cindex C@t{++} symbol display
14024 @item set print demangle
14025 @itemx show print demangle
14026 @itemx set print asm-demangle
14027 @itemx show print asm-demangle
14028 Control whether C@t{++} symbols display in their source form, both when
14029 displaying code as C@t{++} source and when displaying disassemblies.
14030 @xref{Print Settings, ,Print Settings}.
14032 @item set print object
14033 @itemx show print object
14034 Choose whether to print derived (actual) or declared types of objects.
14035 @xref{Print Settings, ,Print Settings}.
14037 @item set print vtbl
14038 @itemx show print vtbl
14039 Control the format for printing virtual function tables.
14040 @xref{Print Settings, ,Print Settings}.
14041 (The @code{vtbl} commands do not work on programs compiled with the HP
14042 ANSI C@t{++} compiler (@code{aCC}).)
14044 @kindex set overload-resolution
14045 @cindex overloaded functions, overload resolution
14046 @item set overload-resolution on
14047 Enable overload resolution for C@t{++} expression evaluation. The default
14048 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14049 and searches for a function whose signature matches the argument types,
14050 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14051 Expressions, ,C@t{++} Expressions}, for details).
14052 If it cannot find a match, it emits a message.
14054 @item set overload-resolution off
14055 Disable overload resolution for C@t{++} expression evaluation. For
14056 overloaded functions that are not class member functions, @value{GDBN}
14057 chooses the first function of the specified name that it finds in the
14058 symbol table, whether or not its arguments are of the correct type. For
14059 overloaded functions that are class member functions, @value{GDBN}
14060 searches for a function whose signature @emph{exactly} matches the
14063 @kindex show overload-resolution
14064 @item show overload-resolution
14065 Show the current setting of overload resolution.
14067 @item @r{Overloaded symbol names}
14068 You can specify a particular definition of an overloaded symbol, using
14069 the same notation that is used to declare such symbols in C@t{++}: type
14070 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14071 also use the @value{GDBN} command-line word completion facilities to list the
14072 available choices, or to finish the type list for you.
14073 @xref{Completion,, Command Completion}, for details on how to do this.
14076 @node Decimal Floating Point
14077 @subsubsection Decimal Floating Point format
14078 @cindex decimal floating point format
14080 @value{GDBN} can examine, set and perform computations with numbers in
14081 decimal floating point format, which in the C language correspond to the
14082 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14083 specified by the extension to support decimal floating-point arithmetic.
14085 There are two encodings in use, depending on the architecture: BID (Binary
14086 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14087 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14090 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14091 to manipulate decimal floating point numbers, it is not possible to convert
14092 (using a cast, for example) integers wider than 32-bit to decimal float.
14094 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14095 point computations, error checking in decimal float operations ignores
14096 underflow, overflow and divide by zero exceptions.
14098 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14099 to inspect @code{_Decimal128} values stored in floating point registers.
14100 See @ref{PowerPC,,PowerPC} for more details.
14106 @value{GDBN} can be used to debug programs written in D and compiled with
14107 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14108 specific feature --- dynamic arrays.
14113 @cindex Go (programming language)
14114 @value{GDBN} can be used to debug programs written in Go and compiled with
14115 @file{gccgo} or @file{6g} compilers.
14117 Here is a summary of the Go-specific features and restrictions:
14120 @cindex current Go package
14121 @item The current Go package
14122 The name of the current package does not need to be specified when
14123 specifying global variables and functions.
14125 For example, given the program:
14129 var myglob = "Shall we?"
14135 When stopped inside @code{main} either of these work:
14139 (gdb) p main.myglob
14142 @cindex builtin Go types
14143 @item Builtin Go types
14144 The @code{string} type is recognized by @value{GDBN} and is printed
14147 @cindex builtin Go functions
14148 @item Builtin Go functions
14149 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14150 function and handles it internally.
14152 @cindex restrictions on Go expressions
14153 @item Restrictions on Go expressions
14154 All Go operators are supported except @code{&^}.
14155 The Go @code{_} ``blank identifier'' is not supported.
14156 Automatic dereferencing of pointers is not supported.
14160 @subsection Objective-C
14162 @cindex Objective-C
14163 This section provides information about some commands and command
14164 options that are useful for debugging Objective-C code. See also
14165 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14166 few more commands specific to Objective-C support.
14169 * Method Names in Commands::
14170 * The Print Command with Objective-C::
14173 @node Method Names in Commands
14174 @subsubsection Method Names in Commands
14176 The following commands have been extended to accept Objective-C method
14177 names as line specifications:
14179 @kindex clear@r{, and Objective-C}
14180 @kindex break@r{, and Objective-C}
14181 @kindex info line@r{, and Objective-C}
14182 @kindex jump@r{, and Objective-C}
14183 @kindex list@r{, and Objective-C}
14187 @item @code{info line}
14192 A fully qualified Objective-C method name is specified as
14195 -[@var{Class} @var{methodName}]
14198 where the minus sign is used to indicate an instance method and a
14199 plus sign (not shown) is used to indicate a class method. The class
14200 name @var{Class} and method name @var{methodName} are enclosed in
14201 brackets, similar to the way messages are specified in Objective-C
14202 source code. For example, to set a breakpoint at the @code{create}
14203 instance method of class @code{Fruit} in the program currently being
14207 break -[Fruit create]
14210 To list ten program lines around the @code{initialize} class method,
14214 list +[NSText initialize]
14217 In the current version of @value{GDBN}, the plus or minus sign is
14218 required. In future versions of @value{GDBN}, the plus or minus
14219 sign will be optional, but you can use it to narrow the search. It
14220 is also possible to specify just a method name:
14226 You must specify the complete method name, including any colons. If
14227 your program's source files contain more than one @code{create} method,
14228 you'll be presented with a numbered list of classes that implement that
14229 method. Indicate your choice by number, or type @samp{0} to exit if
14232 As another example, to clear a breakpoint established at the
14233 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14236 clear -[NSWindow makeKeyAndOrderFront:]
14239 @node The Print Command with Objective-C
14240 @subsubsection The Print Command With Objective-C
14241 @cindex Objective-C, print objects
14242 @kindex print-object
14243 @kindex po @r{(@code{print-object})}
14245 The print command has also been extended to accept methods. For example:
14248 print -[@var{object} hash]
14251 @cindex print an Objective-C object description
14252 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14254 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14255 and print the result. Also, an additional command has been added,
14256 @code{print-object} or @code{po} for short, which is meant to print
14257 the description of an object. However, this command may only work
14258 with certain Objective-C libraries that have a particular hook
14259 function, @code{_NSPrintForDebugger}, defined.
14262 @subsection OpenCL C
14265 This section provides information about @value{GDBN}s OpenCL C support.
14268 * OpenCL C Datatypes::
14269 * OpenCL C Expressions::
14270 * OpenCL C Operators::
14273 @node OpenCL C Datatypes
14274 @subsubsection OpenCL C Datatypes
14276 @cindex OpenCL C Datatypes
14277 @value{GDBN} supports the builtin scalar and vector datatypes specified
14278 by OpenCL 1.1. In addition the half- and double-precision floating point
14279 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14280 extensions are also known to @value{GDBN}.
14282 @node OpenCL C Expressions
14283 @subsubsection OpenCL C Expressions
14285 @cindex OpenCL C Expressions
14286 @value{GDBN} supports accesses to vector components including the access as
14287 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14288 supported by @value{GDBN} can be used as well.
14290 @node OpenCL C Operators
14291 @subsubsection OpenCL C Operators
14293 @cindex OpenCL C Operators
14294 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14298 @subsection Fortran
14299 @cindex Fortran-specific support in @value{GDBN}
14301 @value{GDBN} can be used to debug programs written in Fortran, but it
14302 currently supports only the features of Fortran 77 language.
14304 @cindex trailing underscore, in Fortran symbols
14305 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14306 among them) append an underscore to the names of variables and
14307 functions. When you debug programs compiled by those compilers, you
14308 will need to refer to variables and functions with a trailing
14312 * Fortran Operators:: Fortran operators and expressions
14313 * Fortran Defaults:: Default settings for Fortran
14314 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14317 @node Fortran Operators
14318 @subsubsection Fortran Operators and Expressions
14320 @cindex Fortran operators and expressions
14322 Operators must be defined on values of specific types. For instance,
14323 @code{+} is defined on numbers, but not on characters or other non-
14324 arithmetic types. Operators are often defined on groups of types.
14328 The exponentiation operator. It raises the first operand to the power
14332 The range operator. Normally used in the form of array(low:high) to
14333 represent a section of array.
14336 The access component operator. Normally used to access elements in derived
14337 types. Also suitable for unions. As unions aren't part of regular Fortran,
14338 this can only happen when accessing a register that uses a gdbarch-defined
14342 @node Fortran Defaults
14343 @subsubsection Fortran Defaults
14345 @cindex Fortran Defaults
14347 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14348 default uses case-insensitive matches for Fortran symbols. You can
14349 change that with the @samp{set case-insensitive} command, see
14350 @ref{Symbols}, for the details.
14352 @node Special Fortran Commands
14353 @subsubsection Special Fortran Commands
14355 @cindex Special Fortran commands
14357 @value{GDBN} has some commands to support Fortran-specific features,
14358 such as displaying common blocks.
14361 @cindex @code{COMMON} blocks, Fortran
14362 @kindex info common
14363 @item info common @r{[}@var{common-name}@r{]}
14364 This command prints the values contained in the Fortran @code{COMMON}
14365 block whose name is @var{common-name}. With no argument, the names of
14366 all @code{COMMON} blocks visible at the current program location are
14373 @cindex Pascal support in @value{GDBN}, limitations
14374 Debugging Pascal programs which use sets, subranges, file variables, or
14375 nested functions does not currently work. @value{GDBN} does not support
14376 entering expressions, printing values, or similar features using Pascal
14379 The Pascal-specific command @code{set print pascal_static-members}
14380 controls whether static members of Pascal objects are displayed.
14381 @xref{Print Settings, pascal_static-members}.
14384 @subsection Modula-2
14386 @cindex Modula-2, @value{GDBN} support
14388 The extensions made to @value{GDBN} to support Modula-2 only support
14389 output from the @sc{gnu} Modula-2 compiler (which is currently being
14390 developed). Other Modula-2 compilers are not currently supported, and
14391 attempting to debug executables produced by them is most likely
14392 to give an error as @value{GDBN} reads in the executable's symbol
14395 @cindex expressions in Modula-2
14397 * M2 Operators:: Built-in operators
14398 * Built-In Func/Proc:: Built-in functions and procedures
14399 * M2 Constants:: Modula-2 constants
14400 * M2 Types:: Modula-2 types
14401 * M2 Defaults:: Default settings for Modula-2
14402 * Deviations:: Deviations from standard Modula-2
14403 * M2 Checks:: Modula-2 type and range checks
14404 * M2 Scope:: The scope operators @code{::} and @code{.}
14405 * GDB/M2:: @value{GDBN} and Modula-2
14409 @subsubsection Operators
14410 @cindex Modula-2 operators
14412 Operators must be defined on values of specific types. For instance,
14413 @code{+} is defined on numbers, but not on structures. Operators are
14414 often defined on groups of types. For the purposes of Modula-2, the
14415 following definitions hold:
14420 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14424 @emph{Character types} consist of @code{CHAR} and its subranges.
14427 @emph{Floating-point types} consist of @code{REAL}.
14430 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14434 @emph{Scalar types} consist of all of the above.
14437 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14440 @emph{Boolean types} consist of @code{BOOLEAN}.
14444 The following operators are supported, and appear in order of
14445 increasing precedence:
14449 Function argument or array index separator.
14452 Assignment. The value of @var{var} @code{:=} @var{value} is
14456 Less than, greater than on integral, floating-point, or enumerated
14460 Less than or equal to, greater than or equal to
14461 on integral, floating-point and enumerated types, or set inclusion on
14462 set types. Same precedence as @code{<}.
14464 @item =@r{, }<>@r{, }#
14465 Equality and two ways of expressing inequality, valid on scalar types.
14466 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14467 available for inequality, since @code{#} conflicts with the script
14471 Set membership. Defined on set types and the types of their members.
14472 Same precedence as @code{<}.
14475 Boolean disjunction. Defined on boolean types.
14478 Boolean conjunction. Defined on boolean types.
14481 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14484 Addition and subtraction on integral and floating-point types, or union
14485 and difference on set types.
14488 Multiplication on integral and floating-point types, or set intersection
14492 Division on floating-point types, or symmetric set difference on set
14493 types. Same precedence as @code{*}.
14496 Integer division and remainder. Defined on integral types. Same
14497 precedence as @code{*}.
14500 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14503 Pointer dereferencing. Defined on pointer types.
14506 Boolean negation. Defined on boolean types. Same precedence as
14510 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14511 precedence as @code{^}.
14514 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14517 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14521 @value{GDBN} and Modula-2 scope operators.
14525 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14526 treats the use of the operator @code{IN}, or the use of operators
14527 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14528 @code{<=}, and @code{>=} on sets as an error.
14532 @node Built-In Func/Proc
14533 @subsubsection Built-in Functions and Procedures
14534 @cindex Modula-2 built-ins
14536 Modula-2 also makes available several built-in procedures and functions.
14537 In describing these, the following metavariables are used:
14542 represents an @code{ARRAY} variable.
14545 represents a @code{CHAR} constant or variable.
14548 represents a variable or constant of integral type.
14551 represents an identifier that belongs to a set. Generally used in the
14552 same function with the metavariable @var{s}. The type of @var{s} should
14553 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14556 represents a variable or constant of integral or floating-point type.
14559 represents a variable or constant of floating-point type.
14565 represents a variable.
14568 represents a variable or constant of one of many types. See the
14569 explanation of the function for details.
14572 All Modula-2 built-in procedures also return a result, described below.
14576 Returns the absolute value of @var{n}.
14579 If @var{c} is a lower case letter, it returns its upper case
14580 equivalent, otherwise it returns its argument.
14583 Returns the character whose ordinal value is @var{i}.
14586 Decrements the value in the variable @var{v} by one. Returns the new value.
14588 @item DEC(@var{v},@var{i})
14589 Decrements the value in the variable @var{v} by @var{i}. Returns the
14592 @item EXCL(@var{m},@var{s})
14593 Removes the element @var{m} from the set @var{s}. Returns the new
14596 @item FLOAT(@var{i})
14597 Returns the floating point equivalent of the integer @var{i}.
14599 @item HIGH(@var{a})
14600 Returns the index of the last member of @var{a}.
14603 Increments the value in the variable @var{v} by one. Returns the new value.
14605 @item INC(@var{v},@var{i})
14606 Increments the value in the variable @var{v} by @var{i}. Returns the
14609 @item INCL(@var{m},@var{s})
14610 Adds the element @var{m} to the set @var{s} if it is not already
14611 there. Returns the new set.
14614 Returns the maximum value of the type @var{t}.
14617 Returns the minimum value of the type @var{t}.
14620 Returns boolean TRUE if @var{i} is an odd number.
14623 Returns the ordinal value of its argument. For example, the ordinal
14624 value of a character is its @sc{ascii} value (on machines supporting the
14625 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14626 integral, character and enumerated types.
14628 @item SIZE(@var{x})
14629 Returns the size of its argument. @var{x} can be a variable or a type.
14631 @item TRUNC(@var{r})
14632 Returns the integral part of @var{r}.
14634 @item TSIZE(@var{x})
14635 Returns the size of its argument. @var{x} can be a variable or a type.
14637 @item VAL(@var{t},@var{i})
14638 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14642 @emph{Warning:} Sets and their operations are not yet supported, so
14643 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14647 @cindex Modula-2 constants
14649 @subsubsection Constants
14651 @value{GDBN} allows you to express the constants of Modula-2 in the following
14657 Integer constants are simply a sequence of digits. When used in an
14658 expression, a constant is interpreted to be type-compatible with the
14659 rest of the expression. Hexadecimal integers are specified by a
14660 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14663 Floating point constants appear as a sequence of digits, followed by a
14664 decimal point and another sequence of digits. An optional exponent can
14665 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14666 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14667 digits of the floating point constant must be valid decimal (base 10)
14671 Character constants consist of a single character enclosed by a pair of
14672 like quotes, either single (@code{'}) or double (@code{"}). They may
14673 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14674 followed by a @samp{C}.
14677 String constants consist of a sequence of characters enclosed by a
14678 pair of like quotes, either single (@code{'}) or double (@code{"}).
14679 Escape sequences in the style of C are also allowed. @xref{C
14680 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14684 Enumerated constants consist of an enumerated identifier.
14687 Boolean constants consist of the identifiers @code{TRUE} and
14691 Pointer constants consist of integral values only.
14694 Set constants are not yet supported.
14698 @subsubsection Modula-2 Types
14699 @cindex Modula-2 types
14701 Currently @value{GDBN} can print the following data types in Modula-2
14702 syntax: array types, record types, set types, pointer types, procedure
14703 types, enumerated types, subrange types and base types. You can also
14704 print the contents of variables declared using these type.
14705 This section gives a number of simple source code examples together with
14706 sample @value{GDBN} sessions.
14708 The first example contains the following section of code:
14717 and you can request @value{GDBN} to interrogate the type and value of
14718 @code{r} and @code{s}.
14721 (@value{GDBP}) print s
14723 (@value{GDBP}) ptype s
14725 (@value{GDBP}) print r
14727 (@value{GDBP}) ptype r
14732 Likewise if your source code declares @code{s} as:
14736 s: SET ['A'..'Z'] ;
14740 then you may query the type of @code{s} by:
14743 (@value{GDBP}) ptype s
14744 type = SET ['A'..'Z']
14748 Note that at present you cannot interactively manipulate set
14749 expressions using the debugger.
14751 The following example shows how you might declare an array in Modula-2
14752 and how you can interact with @value{GDBN} to print its type and contents:
14756 s: ARRAY [-10..10] OF CHAR ;
14760 (@value{GDBP}) ptype s
14761 ARRAY [-10..10] OF CHAR
14764 Note that the array handling is not yet complete and although the type
14765 is printed correctly, expression handling still assumes that all
14766 arrays have a lower bound of zero and not @code{-10} as in the example
14769 Here are some more type related Modula-2 examples:
14773 colour = (blue, red, yellow, green) ;
14774 t = [blue..yellow] ;
14782 The @value{GDBN} interaction shows how you can query the data type
14783 and value of a variable.
14786 (@value{GDBP}) print s
14788 (@value{GDBP}) ptype t
14789 type = [blue..yellow]
14793 In this example a Modula-2 array is declared and its contents
14794 displayed. Observe that the contents are written in the same way as
14795 their @code{C} counterparts.
14799 s: ARRAY [1..5] OF CARDINAL ;
14805 (@value{GDBP}) print s
14806 $1 = @{1, 0, 0, 0, 0@}
14807 (@value{GDBP}) ptype s
14808 type = ARRAY [1..5] OF CARDINAL
14811 The Modula-2 language interface to @value{GDBN} also understands
14812 pointer types as shown in this example:
14816 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14823 and you can request that @value{GDBN} describes the type of @code{s}.
14826 (@value{GDBP}) ptype s
14827 type = POINTER TO ARRAY [1..5] OF CARDINAL
14830 @value{GDBN} handles compound types as we can see in this example.
14831 Here we combine array types, record types, pointer types and subrange
14842 myarray = ARRAY myrange OF CARDINAL ;
14843 myrange = [-2..2] ;
14845 s: POINTER TO ARRAY myrange OF foo ;
14849 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14853 (@value{GDBP}) ptype s
14854 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14857 f3 : ARRAY [-2..2] OF CARDINAL;
14862 @subsubsection Modula-2 Defaults
14863 @cindex Modula-2 defaults
14865 If type and range checking are set automatically by @value{GDBN}, they
14866 both default to @code{on} whenever the working language changes to
14867 Modula-2. This happens regardless of whether you or @value{GDBN}
14868 selected the working language.
14870 If you allow @value{GDBN} to set the language automatically, then entering
14871 code compiled from a file whose name ends with @file{.mod} sets the
14872 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14873 Infer the Source Language}, for further details.
14876 @subsubsection Deviations from Standard Modula-2
14877 @cindex Modula-2, deviations from
14879 A few changes have been made to make Modula-2 programs easier to debug.
14880 This is done primarily via loosening its type strictness:
14884 Unlike in standard Modula-2, pointer constants can be formed by
14885 integers. This allows you to modify pointer variables during
14886 debugging. (In standard Modula-2, the actual address contained in a
14887 pointer variable is hidden from you; it can only be modified
14888 through direct assignment to another pointer variable or expression that
14889 returned a pointer.)
14892 C escape sequences can be used in strings and characters to represent
14893 non-printable characters. @value{GDBN} prints out strings with these
14894 escape sequences embedded. Single non-printable characters are
14895 printed using the @samp{CHR(@var{nnn})} format.
14898 The assignment operator (@code{:=}) returns the value of its right-hand
14902 All built-in procedures both modify @emph{and} return their argument.
14906 @subsubsection Modula-2 Type and Range Checks
14907 @cindex Modula-2 checks
14910 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14913 @c FIXME remove warning when type/range checks added
14915 @value{GDBN} considers two Modula-2 variables type equivalent if:
14919 They are of types that have been declared equivalent via a @code{TYPE
14920 @var{t1} = @var{t2}} statement
14923 They have been declared on the same line. (Note: This is true of the
14924 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14927 As long as type checking is enabled, any attempt to combine variables
14928 whose types are not equivalent is an error.
14930 Range checking is done on all mathematical operations, assignment, array
14931 index bounds, and all built-in functions and procedures.
14934 @subsubsection The Scope Operators @code{::} and @code{.}
14936 @cindex @code{.}, Modula-2 scope operator
14937 @cindex colon, doubled as scope operator
14939 @vindex colon-colon@r{, in Modula-2}
14940 @c Info cannot handle :: but TeX can.
14943 @vindex ::@r{, in Modula-2}
14946 There are a few subtle differences between the Modula-2 scope operator
14947 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14952 @var{module} . @var{id}
14953 @var{scope} :: @var{id}
14957 where @var{scope} is the name of a module or a procedure,
14958 @var{module} the name of a module, and @var{id} is any declared
14959 identifier within your program, except another module.
14961 Using the @code{::} operator makes @value{GDBN} search the scope
14962 specified by @var{scope} for the identifier @var{id}. If it is not
14963 found in the specified scope, then @value{GDBN} searches all scopes
14964 enclosing the one specified by @var{scope}.
14966 Using the @code{.} operator makes @value{GDBN} search the current scope for
14967 the identifier specified by @var{id} that was imported from the
14968 definition module specified by @var{module}. With this operator, it is
14969 an error if the identifier @var{id} was not imported from definition
14970 module @var{module}, or if @var{id} is not an identifier in
14974 @subsubsection @value{GDBN} and Modula-2
14976 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14977 Five subcommands of @code{set print} and @code{show print} apply
14978 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14979 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14980 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14981 analogue in Modula-2.
14983 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14984 with any language, is not useful with Modula-2. Its
14985 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14986 created in Modula-2 as they can in C or C@t{++}. However, because an
14987 address can be specified by an integral constant, the construct
14988 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14990 @cindex @code{#} in Modula-2
14991 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14992 interpreted as the beginning of a comment. Use @code{<>} instead.
14998 The extensions made to @value{GDBN} for Ada only support
14999 output from the @sc{gnu} Ada (GNAT) compiler.
15000 Other Ada compilers are not currently supported, and
15001 attempting to debug executables produced by them is most likely
15005 @cindex expressions in Ada
15007 * Ada Mode Intro:: General remarks on the Ada syntax
15008 and semantics supported by Ada mode
15010 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15011 * Additions to Ada:: Extensions of the Ada expression syntax.
15012 * Stopping Before Main Program:: Debugging the program during elaboration.
15013 * Ada Exceptions:: Ada Exceptions
15014 * Ada Tasks:: Listing and setting breakpoints in tasks.
15015 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15016 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15018 * Ada Glitches:: Known peculiarities of Ada mode.
15021 @node Ada Mode Intro
15022 @subsubsection Introduction
15023 @cindex Ada mode, general
15025 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15026 syntax, with some extensions.
15027 The philosophy behind the design of this subset is
15031 That @value{GDBN} should provide basic literals and access to operations for
15032 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15033 leaving more sophisticated computations to subprograms written into the
15034 program (which therefore may be called from @value{GDBN}).
15037 That type safety and strict adherence to Ada language restrictions
15038 are not particularly important to the @value{GDBN} user.
15041 That brevity is important to the @value{GDBN} user.
15044 Thus, for brevity, the debugger acts as if all names declared in
15045 user-written packages are directly visible, even if they are not visible
15046 according to Ada rules, thus making it unnecessary to fully qualify most
15047 names with their packages, regardless of context. Where this causes
15048 ambiguity, @value{GDBN} asks the user's intent.
15050 The debugger will start in Ada mode if it detects an Ada main program.
15051 As for other languages, it will enter Ada mode when stopped in a program that
15052 was translated from an Ada source file.
15054 While in Ada mode, you may use `@t{--}' for comments. This is useful
15055 mostly for documenting command files. The standard @value{GDBN} comment
15056 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15057 middle (to allow based literals).
15059 The debugger supports limited overloading. Given a subprogram call in which
15060 the function symbol has multiple definitions, it will use the number of
15061 actual parameters and some information about their types to attempt to narrow
15062 the set of definitions. It also makes very limited use of context, preferring
15063 procedures to functions in the context of the @code{call} command, and
15064 functions to procedures elsewhere.
15066 @node Omissions from Ada
15067 @subsubsection Omissions from Ada
15068 @cindex Ada, omissions from
15070 Here are the notable omissions from the subset:
15074 Only a subset of the attributes are supported:
15078 @t{'First}, @t{'Last}, and @t{'Length}
15079 on array objects (not on types and subtypes).
15082 @t{'Min} and @t{'Max}.
15085 @t{'Pos} and @t{'Val}.
15091 @t{'Range} on array objects (not subtypes), but only as the right
15092 operand of the membership (@code{in}) operator.
15095 @t{'Access}, @t{'Unchecked_Access}, and
15096 @t{'Unrestricted_Access} (a GNAT extension).
15104 @code{Characters.Latin_1} are not available and
15105 concatenation is not implemented. Thus, escape characters in strings are
15106 not currently available.
15109 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15110 equality of representations. They will generally work correctly
15111 for strings and arrays whose elements have integer or enumeration types.
15112 They may not work correctly for arrays whose element
15113 types have user-defined equality, for arrays of real values
15114 (in particular, IEEE-conformant floating point, because of negative
15115 zeroes and NaNs), and for arrays whose elements contain unused bits with
15116 indeterminate values.
15119 The other component-by-component array operations (@code{and}, @code{or},
15120 @code{xor}, @code{not}, and relational tests other than equality)
15121 are not implemented.
15124 @cindex array aggregates (Ada)
15125 @cindex record aggregates (Ada)
15126 @cindex aggregates (Ada)
15127 There is limited support for array and record aggregates. They are
15128 permitted only on the right sides of assignments, as in these examples:
15131 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15132 (@value{GDBP}) set An_Array := (1, others => 0)
15133 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15134 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15135 (@value{GDBP}) set A_Record := (1, "Peter", True);
15136 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15140 discriminant's value by assigning an aggregate has an
15141 undefined effect if that discriminant is used within the record.
15142 However, you can first modify discriminants by directly assigning to
15143 them (which normally would not be allowed in Ada), and then performing an
15144 aggregate assignment. For example, given a variable @code{A_Rec}
15145 declared to have a type such as:
15148 type Rec (Len : Small_Integer := 0) is record
15150 Vals : IntArray (1 .. Len);
15154 you can assign a value with a different size of @code{Vals} with two
15158 (@value{GDBP}) set A_Rec.Len := 4
15159 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15162 As this example also illustrates, @value{GDBN} is very loose about the usual
15163 rules concerning aggregates. You may leave out some of the
15164 components of an array or record aggregate (such as the @code{Len}
15165 component in the assignment to @code{A_Rec} above); they will retain their
15166 original values upon assignment. You may freely use dynamic values as
15167 indices in component associations. You may even use overlapping or
15168 redundant component associations, although which component values are
15169 assigned in such cases is not defined.
15172 Calls to dispatching subprograms are not implemented.
15175 The overloading algorithm is much more limited (i.e., less selective)
15176 than that of real Ada. It makes only limited use of the context in
15177 which a subexpression appears to resolve its meaning, and it is much
15178 looser in its rules for allowing type matches. As a result, some
15179 function calls will be ambiguous, and the user will be asked to choose
15180 the proper resolution.
15183 The @code{new} operator is not implemented.
15186 Entry calls are not implemented.
15189 Aside from printing, arithmetic operations on the native VAX floating-point
15190 formats are not supported.
15193 It is not possible to slice a packed array.
15196 The names @code{True} and @code{False}, when not part of a qualified name,
15197 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15199 Should your program
15200 redefine these names in a package or procedure (at best a dubious practice),
15201 you will have to use fully qualified names to access their new definitions.
15204 @node Additions to Ada
15205 @subsubsection Additions to Ada
15206 @cindex Ada, deviations from
15208 As it does for other languages, @value{GDBN} makes certain generic
15209 extensions to Ada (@pxref{Expressions}):
15213 If the expression @var{E} is a variable residing in memory (typically
15214 a local variable or array element) and @var{N} is a positive integer,
15215 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15216 @var{N}-1 adjacent variables following it in memory as an array. In
15217 Ada, this operator is generally not necessary, since its prime use is
15218 in displaying parts of an array, and slicing will usually do this in
15219 Ada. However, there are occasional uses when debugging programs in
15220 which certain debugging information has been optimized away.
15223 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15224 appears in function or file @var{B}.'' When @var{B} is a file name,
15225 you must typically surround it in single quotes.
15228 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15229 @var{type} that appears at address @var{addr}.''
15232 A name starting with @samp{$} is a convenience variable
15233 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15236 In addition, @value{GDBN} provides a few other shortcuts and outright
15237 additions specific to Ada:
15241 The assignment statement is allowed as an expression, returning
15242 its right-hand operand as its value. Thus, you may enter
15245 (@value{GDBP}) set x := y + 3
15246 (@value{GDBP}) print A(tmp := y + 1)
15250 The semicolon is allowed as an ``operator,'' returning as its value
15251 the value of its right-hand operand.
15252 This allows, for example,
15253 complex conditional breaks:
15256 (@value{GDBP}) break f
15257 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15261 Rather than use catenation and symbolic character names to introduce special
15262 characters into strings, one may instead use a special bracket notation,
15263 which is also used to print strings. A sequence of characters of the form
15264 @samp{["@var{XX}"]} within a string or character literal denotes the
15265 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15266 sequence of characters @samp{["""]} also denotes a single quotation mark
15267 in strings. For example,
15269 "One line.["0a"]Next line.["0a"]"
15272 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15276 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15277 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15281 (@value{GDBP}) print 'max(x, y)
15285 When printing arrays, @value{GDBN} uses positional notation when the
15286 array has a lower bound of 1, and uses a modified named notation otherwise.
15287 For example, a one-dimensional array of three integers with a lower bound
15288 of 3 might print as
15295 That is, in contrast to valid Ada, only the first component has a @code{=>}
15299 You may abbreviate attributes in expressions with any unique,
15300 multi-character subsequence of
15301 their names (an exact match gets preference).
15302 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15303 in place of @t{a'length}.
15306 @cindex quoting Ada internal identifiers
15307 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15308 to lower case. The GNAT compiler uses upper-case characters for
15309 some of its internal identifiers, which are normally of no interest to users.
15310 For the rare occasions when you actually have to look at them,
15311 enclose them in angle brackets to avoid the lower-case mapping.
15314 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15318 Printing an object of class-wide type or dereferencing an
15319 access-to-class-wide value will display all the components of the object's
15320 specific type (as indicated by its run-time tag). Likewise, component
15321 selection on such a value will operate on the specific type of the
15326 @node Stopping Before Main Program
15327 @subsubsection Stopping at the Very Beginning
15329 @cindex breakpointing Ada elaboration code
15330 It is sometimes necessary to debug the program during elaboration, and
15331 before reaching the main procedure.
15332 As defined in the Ada Reference
15333 Manual, the elaboration code is invoked from a procedure called
15334 @code{adainit}. To run your program up to the beginning of
15335 elaboration, simply use the following two commands:
15336 @code{tbreak adainit} and @code{run}.
15338 @node Ada Exceptions
15339 @subsubsection Ada Exceptions
15341 A command is provided to list all Ada exceptions:
15344 @kindex info exceptions
15345 @item info exceptions
15346 @itemx info exceptions @var{regexp}
15347 The @code{info exceptions} command allows you to list all Ada exceptions
15348 defined within the program being debugged, as well as their addresses.
15349 With a regular expression, @var{regexp}, as argument, only those exceptions
15350 whose names match @var{regexp} are listed.
15353 Below is a small example, showing how the command can be used, first
15354 without argument, and next with a regular expression passed as an
15358 (@value{GDBP}) info exceptions
15359 All defined Ada exceptions:
15360 constraint_error: 0x613da0
15361 program_error: 0x613d20
15362 storage_error: 0x613ce0
15363 tasking_error: 0x613ca0
15364 const.aint_global_e: 0x613b00
15365 (@value{GDBP}) info exceptions const.aint
15366 All Ada exceptions matching regular expression "const.aint":
15367 constraint_error: 0x613da0
15368 const.aint_global_e: 0x613b00
15371 It is also possible to ask @value{GDBN} to stop your program's execution
15372 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15375 @subsubsection Extensions for Ada Tasks
15376 @cindex Ada, tasking
15378 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15379 @value{GDBN} provides the following task-related commands:
15384 This command shows a list of current Ada tasks, as in the following example:
15391 (@value{GDBP}) info tasks
15392 ID TID P-ID Pri State Name
15393 1 8088000 0 15 Child Activation Wait main_task
15394 2 80a4000 1 15 Accept Statement b
15395 3 809a800 1 15 Child Activation Wait a
15396 * 4 80ae800 3 15 Runnable c
15401 In this listing, the asterisk before the last task indicates it to be the
15402 task currently being inspected.
15406 Represents @value{GDBN}'s internal task number.
15412 The parent's task ID (@value{GDBN}'s internal task number).
15415 The base priority of the task.
15418 Current state of the task.
15422 The task has been created but has not been activated. It cannot be
15426 The task is not blocked for any reason known to Ada. (It may be waiting
15427 for a mutex, though.) It is conceptually "executing" in normal mode.
15430 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15431 that were waiting on terminate alternatives have been awakened and have
15432 terminated themselves.
15434 @item Child Activation Wait
15435 The task is waiting for created tasks to complete activation.
15437 @item Accept Statement
15438 The task is waiting on an accept or selective wait statement.
15440 @item Waiting on entry call
15441 The task is waiting on an entry call.
15443 @item Async Select Wait
15444 The task is waiting to start the abortable part of an asynchronous
15448 The task is waiting on a select statement with only a delay
15451 @item Child Termination Wait
15452 The task is sleeping having completed a master within itself, and is
15453 waiting for the tasks dependent on that master to become terminated or
15454 waiting on a terminate Phase.
15456 @item Wait Child in Term Alt
15457 The task is sleeping waiting for tasks on terminate alternatives to
15458 finish terminating.
15460 @item Accepting RV with @var{taskno}
15461 The task is accepting a rendez-vous with the task @var{taskno}.
15465 Name of the task in the program.
15469 @kindex info task @var{taskno}
15470 @item info task @var{taskno}
15471 This command shows detailled informations on the specified task, as in
15472 the following example:
15477 (@value{GDBP}) info tasks
15478 ID TID P-ID Pri State Name
15479 1 8077880 0 15 Child Activation Wait main_task
15480 * 2 807c468 1 15 Runnable task_1
15481 (@value{GDBP}) info task 2
15482 Ada Task: 0x807c468
15485 Parent: 1 (main_task)
15491 @kindex task@r{ (Ada)}
15492 @cindex current Ada task ID
15493 This command prints the ID of the current task.
15499 (@value{GDBP}) info tasks
15500 ID TID P-ID Pri State Name
15501 1 8077870 0 15 Child Activation Wait main_task
15502 * 2 807c458 1 15 Runnable t
15503 (@value{GDBP}) task
15504 [Current task is 2]
15507 @item task @var{taskno}
15508 @cindex Ada task switching
15509 This command is like the @code{thread @var{threadno}}
15510 command (@pxref{Threads}). It switches the context of debugging
15511 from the current task to the given task.
15517 (@value{GDBP}) info tasks
15518 ID TID P-ID Pri State Name
15519 1 8077870 0 15 Child Activation Wait main_task
15520 * 2 807c458 1 15 Runnable t
15521 (@value{GDBP}) task 1
15522 [Switching to task 1]
15523 #0 0x8067726 in pthread_cond_wait ()
15525 #0 0x8067726 in pthread_cond_wait ()
15526 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15527 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15528 #3 0x806153e in system.tasking.stages.activate_tasks ()
15529 #4 0x804aacc in un () at un.adb:5
15532 @item break @var{linespec} task @var{taskno}
15533 @itemx break @var{linespec} task @var{taskno} if @dots{}
15534 @cindex breakpoints and tasks, in Ada
15535 @cindex task breakpoints, in Ada
15536 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15537 These commands are like the @code{break @dots{} thread @dots{}}
15538 command (@pxref{Thread Stops}).
15539 @var{linespec} specifies source lines, as described
15540 in @ref{Specify Location}.
15542 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15543 to specify that you only want @value{GDBN} to stop the program when a
15544 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15545 numeric task identifiers assigned by @value{GDBN}, shown in the first
15546 column of the @samp{info tasks} display.
15548 If you do not specify @samp{task @var{taskno}} when you set a
15549 breakpoint, the breakpoint applies to @emph{all} tasks of your
15552 You can use the @code{task} qualifier on conditional breakpoints as
15553 well; in this case, place @samp{task @var{taskno}} before the
15554 breakpoint condition (before the @code{if}).
15562 (@value{GDBP}) info tasks
15563 ID TID P-ID Pri State Name
15564 1 140022020 0 15 Child Activation Wait main_task
15565 2 140045060 1 15 Accept/Select Wait t2
15566 3 140044840 1 15 Runnable t1
15567 * 4 140056040 1 15 Runnable t3
15568 (@value{GDBP}) b 15 task 2
15569 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15570 (@value{GDBP}) cont
15575 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15577 (@value{GDBP}) info tasks
15578 ID TID P-ID Pri State Name
15579 1 140022020 0 15 Child Activation Wait main_task
15580 * 2 140045060 1 15 Runnable t2
15581 3 140044840 1 15 Runnable t1
15582 4 140056040 1 15 Delay Sleep t3
15586 @node Ada Tasks and Core Files
15587 @subsubsection Tasking Support when Debugging Core Files
15588 @cindex Ada tasking and core file debugging
15590 When inspecting a core file, as opposed to debugging a live program,
15591 tasking support may be limited or even unavailable, depending on
15592 the platform being used.
15593 For instance, on x86-linux, the list of tasks is available, but task
15594 switching is not supported. On Tru64, however, task switching will work
15597 On certain platforms, including Tru64, the debugger needs to perform some
15598 memory writes in order to provide Ada tasking support. When inspecting
15599 a core file, this means that the core file must be opened with read-write
15600 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15601 Under these circumstances, you should make a backup copy of the core
15602 file before inspecting it with @value{GDBN}.
15604 @node Ravenscar Profile
15605 @subsubsection Tasking Support when using the Ravenscar Profile
15606 @cindex Ravenscar Profile
15608 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15609 specifically designed for systems with safety-critical real-time
15613 @kindex set ravenscar task-switching on
15614 @cindex task switching with program using Ravenscar Profile
15615 @item set ravenscar task-switching on
15616 Allows task switching when debugging a program that uses the Ravenscar
15617 Profile. This is the default.
15619 @kindex set ravenscar task-switching off
15620 @item set ravenscar task-switching off
15621 Turn off task switching when debugging a program that uses the Ravenscar
15622 Profile. This is mostly intended to disable the code that adds support
15623 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15624 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15625 To be effective, this command should be run before the program is started.
15627 @kindex show ravenscar task-switching
15628 @item show ravenscar task-switching
15629 Show whether it is possible to switch from task to task in a program
15630 using the Ravenscar Profile.
15635 @subsubsection Known Peculiarities of Ada Mode
15636 @cindex Ada, problems
15638 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15639 we know of several problems with and limitations of Ada mode in
15641 some of which will be fixed with planned future releases of the debugger
15642 and the GNU Ada compiler.
15646 Static constants that the compiler chooses not to materialize as objects in
15647 storage are invisible to the debugger.
15650 Named parameter associations in function argument lists are ignored (the
15651 argument lists are treated as positional).
15654 Many useful library packages are currently invisible to the debugger.
15657 Fixed-point arithmetic, conversions, input, and output is carried out using
15658 floating-point arithmetic, and may give results that only approximate those on
15662 The GNAT compiler never generates the prefix @code{Standard} for any of
15663 the standard symbols defined by the Ada language. @value{GDBN} knows about
15664 this: it will strip the prefix from names when you use it, and will never
15665 look for a name you have so qualified among local symbols, nor match against
15666 symbols in other packages or subprograms. If you have
15667 defined entities anywhere in your program other than parameters and
15668 local variables whose simple names match names in @code{Standard},
15669 GNAT's lack of qualification here can cause confusion. When this happens,
15670 you can usually resolve the confusion
15671 by qualifying the problematic names with package
15672 @code{Standard} explicitly.
15675 Older versions of the compiler sometimes generate erroneous debugging
15676 information, resulting in the debugger incorrectly printing the value
15677 of affected entities. In some cases, the debugger is able to work
15678 around an issue automatically. In other cases, the debugger is able
15679 to work around the issue, but the work-around has to be specifically
15682 @kindex set ada trust-PAD-over-XVS
15683 @kindex show ada trust-PAD-over-XVS
15686 @item set ada trust-PAD-over-XVS on
15687 Configure GDB to strictly follow the GNAT encoding when computing the
15688 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15689 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15690 a complete description of the encoding used by the GNAT compiler).
15691 This is the default.
15693 @item set ada trust-PAD-over-XVS off
15694 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15695 sometimes prints the wrong value for certain entities, changing @code{ada
15696 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15697 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15698 @code{off}, but this incurs a slight performance penalty, so it is
15699 recommended to leave this setting to @code{on} unless necessary.
15703 @node Unsupported Languages
15704 @section Unsupported Languages
15706 @cindex unsupported languages
15707 @cindex minimal language
15708 In addition to the other fully-supported programming languages,
15709 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15710 It does not represent a real programming language, but provides a set
15711 of capabilities close to what the C or assembly languages provide.
15712 This should allow most simple operations to be performed while debugging
15713 an application that uses a language currently not supported by @value{GDBN}.
15715 If the language is set to @code{auto}, @value{GDBN} will automatically
15716 select this language if the current frame corresponds to an unsupported
15720 @chapter Examining the Symbol Table
15722 The commands described in this chapter allow you to inquire about the
15723 symbols (names of variables, functions and types) defined in your
15724 program. This information is inherent in the text of your program and
15725 does not change as your program executes. @value{GDBN} finds it in your
15726 program's symbol table, in the file indicated when you started @value{GDBN}
15727 (@pxref{File Options, ,Choosing Files}), or by one of the
15728 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15730 @cindex symbol names
15731 @cindex names of symbols
15732 @cindex quoting names
15733 Occasionally, you may need to refer to symbols that contain unusual
15734 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15735 most frequent case is in referring to static variables in other
15736 source files (@pxref{Variables,,Program Variables}). File names
15737 are recorded in object files as debugging symbols, but @value{GDBN} would
15738 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15739 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15740 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15747 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15750 @cindex case-insensitive symbol names
15751 @cindex case sensitivity in symbol names
15752 @kindex set case-sensitive
15753 @item set case-sensitive on
15754 @itemx set case-sensitive off
15755 @itemx set case-sensitive auto
15756 Normally, when @value{GDBN} looks up symbols, it matches their names
15757 with case sensitivity determined by the current source language.
15758 Occasionally, you may wish to control that. The command @code{set
15759 case-sensitive} lets you do that by specifying @code{on} for
15760 case-sensitive matches or @code{off} for case-insensitive ones. If
15761 you specify @code{auto}, case sensitivity is reset to the default
15762 suitable for the source language. The default is case-sensitive
15763 matches for all languages except for Fortran, for which the default is
15764 case-insensitive matches.
15766 @kindex show case-sensitive
15767 @item show case-sensitive
15768 This command shows the current setting of case sensitivity for symbols
15771 @kindex set print type methods
15772 @item set print type methods
15773 @itemx set print type methods on
15774 @itemx set print type methods off
15775 Normally, when @value{GDBN} prints a class, it displays any methods
15776 declared in that class. You can control this behavior either by
15777 passing the appropriate flag to @code{ptype}, or using @command{set
15778 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15779 display the methods; this is the default. Specifying @code{off} will
15780 cause @value{GDBN} to omit the methods.
15782 @kindex show print type methods
15783 @item show print type methods
15784 This command shows the current setting of method display when printing
15787 @kindex set print type typedefs
15788 @item set print type typedefs
15789 @itemx set print type typedefs on
15790 @itemx set print type typedefs off
15792 Normally, when @value{GDBN} prints a class, it displays any typedefs
15793 defined in that class. You can control this behavior either by
15794 passing the appropriate flag to @code{ptype}, or using @command{set
15795 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15796 display the typedef definitions; this is the default. Specifying
15797 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15798 Note that this controls whether the typedef definition itself is
15799 printed, not whether typedef names are substituted when printing other
15802 @kindex show print type typedefs
15803 @item show print type typedefs
15804 This command shows the current setting of typedef display when
15807 @kindex info address
15808 @cindex address of a symbol
15809 @item info address @var{symbol}
15810 Describe where the data for @var{symbol} is stored. For a register
15811 variable, this says which register it is kept in. For a non-register
15812 local variable, this prints the stack-frame offset at which the variable
15815 Note the contrast with @samp{print &@var{symbol}}, which does not work
15816 at all for a register variable, and for a stack local variable prints
15817 the exact address of the current instantiation of the variable.
15819 @kindex info symbol
15820 @cindex symbol from address
15821 @cindex closest symbol and offset for an address
15822 @item info symbol @var{addr}
15823 Print the name of a symbol which is stored at the address @var{addr}.
15824 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15825 nearest symbol and an offset from it:
15828 (@value{GDBP}) info symbol 0x54320
15829 _initialize_vx + 396 in section .text
15833 This is the opposite of the @code{info address} command. You can use
15834 it to find out the name of a variable or a function given its address.
15836 For dynamically linked executables, the name of executable or shared
15837 library containing the symbol is also printed:
15840 (@value{GDBP}) info symbol 0x400225
15841 _start + 5 in section .text of /tmp/a.out
15842 (@value{GDBP}) info symbol 0x2aaaac2811cf
15843 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15847 @item whatis[/@var{flags}] [@var{arg}]
15848 Print the data type of @var{arg}, which can be either an expression
15849 or a name of a data type. With no argument, print the data type of
15850 @code{$}, the last value in the value history.
15852 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15853 is not actually evaluated, and any side-effecting operations (such as
15854 assignments or function calls) inside it do not take place.
15856 If @var{arg} is a variable or an expression, @code{whatis} prints its
15857 literal type as it is used in the source code. If the type was
15858 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15859 the data type underlying the @code{typedef}. If the type of the
15860 variable or the expression is a compound data type, such as
15861 @code{struct} or @code{class}, @code{whatis} never prints their
15862 fields or methods. It just prints the @code{struct}/@code{class}
15863 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15864 such a compound data type, use @code{ptype}.
15866 If @var{arg} is a type name that was defined using @code{typedef},
15867 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15868 Unrolling means that @code{whatis} will show the underlying type used
15869 in the @code{typedef} declaration of @var{arg}. However, if that
15870 underlying type is also a @code{typedef}, @code{whatis} will not
15873 For C code, the type names may also have the form @samp{class
15874 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15875 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15877 @var{flags} can be used to modify how the type is displayed.
15878 Available flags are:
15882 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15883 parameters and typedefs defined in a class when printing the class'
15884 members. The @code{/r} flag disables this.
15887 Do not print methods defined in the class.
15890 Print methods defined in the class. This is the default, but the flag
15891 exists in case you change the default with @command{set print type methods}.
15894 Do not print typedefs defined in the class. Note that this controls
15895 whether the typedef definition itself is printed, not whether typedef
15896 names are substituted when printing other types.
15899 Print typedefs defined in the class. This is the default, but the flag
15900 exists in case you change the default with @command{set print type typedefs}.
15904 @item ptype[/@var{flags}] [@var{arg}]
15905 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15906 detailed description of the type, instead of just the name of the type.
15907 @xref{Expressions, ,Expressions}.
15909 Contrary to @code{whatis}, @code{ptype} always unrolls any
15910 @code{typedef}s in its argument declaration, whether the argument is
15911 a variable, expression, or a data type. This means that @code{ptype}
15912 of a variable or an expression will not print literally its type as
15913 present in the source code---use @code{whatis} for that. @code{typedef}s at
15914 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15915 fields, methods and inner @code{class typedef}s of @code{struct}s,
15916 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15918 For example, for this variable declaration:
15921 typedef double real_t;
15922 struct complex @{ real_t real; double imag; @};
15923 typedef struct complex complex_t;
15925 real_t *real_pointer_var;
15929 the two commands give this output:
15933 (@value{GDBP}) whatis var
15935 (@value{GDBP}) ptype var
15936 type = struct complex @{
15940 (@value{GDBP}) whatis complex_t
15941 type = struct complex
15942 (@value{GDBP}) whatis struct complex
15943 type = struct complex
15944 (@value{GDBP}) ptype struct complex
15945 type = struct complex @{
15949 (@value{GDBP}) whatis real_pointer_var
15951 (@value{GDBP}) ptype real_pointer_var
15957 As with @code{whatis}, using @code{ptype} without an argument refers to
15958 the type of @code{$}, the last value in the value history.
15960 @cindex incomplete type
15961 Sometimes, programs use opaque data types or incomplete specifications
15962 of complex data structure. If the debug information included in the
15963 program does not allow @value{GDBN} to display a full declaration of
15964 the data type, it will say @samp{<incomplete type>}. For example,
15965 given these declarations:
15969 struct foo *fooptr;
15973 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15976 (@value{GDBP}) ptype foo
15977 $1 = <incomplete type>
15981 ``Incomplete type'' is C terminology for data types that are not
15982 completely specified.
15985 @item info types @var{regexp}
15987 Print a brief description of all types whose names match the regular
15988 expression @var{regexp} (or all types in your program, if you supply
15989 no argument). Each complete typename is matched as though it were a
15990 complete line; thus, @samp{i type value} gives information on all
15991 types in your program whose names include the string @code{value}, but
15992 @samp{i type ^value$} gives information only on types whose complete
15993 name is @code{value}.
15995 This command differs from @code{ptype} in two ways: first, like
15996 @code{whatis}, it does not print a detailed description; second, it
15997 lists all source files where a type is defined.
15999 @kindex info type-printers
16000 @item info type-printers
16001 Versions of @value{GDBN} that ship with Python scripting enabled may
16002 have ``type printers'' available. When using @command{ptype} or
16003 @command{whatis}, these printers are consulted when the name of a type
16004 is needed. @xref{Type Printing API}, for more information on writing
16007 @code{info type-printers} displays all the available type printers.
16009 @kindex enable type-printer
16010 @kindex disable type-printer
16011 @item enable type-printer @var{name}@dots{}
16012 @item disable type-printer @var{name}@dots{}
16013 These commands can be used to enable or disable type printers.
16016 @cindex local variables
16017 @item info scope @var{location}
16018 List all the variables local to a particular scope. This command
16019 accepts a @var{location} argument---a function name, a source line, or
16020 an address preceded by a @samp{*}, and prints all the variables local
16021 to the scope defined by that location. (@xref{Specify Location}, for
16022 details about supported forms of @var{location}.) For example:
16025 (@value{GDBP}) @b{info scope command_line_handler}
16026 Scope for command_line_handler:
16027 Symbol rl is an argument at stack/frame offset 8, length 4.
16028 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16029 Symbol linelength is in static storage at address 0x150a1c, length 4.
16030 Symbol p is a local variable in register $esi, length 4.
16031 Symbol p1 is a local variable in register $ebx, length 4.
16032 Symbol nline is a local variable in register $edx, length 4.
16033 Symbol repeat is a local variable at frame offset -8, length 4.
16037 This command is especially useful for determining what data to collect
16038 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16041 @kindex info source
16043 Show information about the current source file---that is, the source file for
16044 the function containing the current point of execution:
16047 the name of the source file, and the directory containing it,
16049 the directory it was compiled in,
16051 its length, in lines,
16053 which programming language it is written in,
16055 whether the executable includes debugging information for that file, and
16056 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16058 whether the debugging information includes information about
16059 preprocessor macros.
16063 @kindex info sources
16065 Print the names of all source files in your program for which there is
16066 debugging information, organized into two lists: files whose symbols
16067 have already been read, and files whose symbols will be read when needed.
16069 @kindex info functions
16070 @item info functions
16071 Print the names and data types of all defined functions.
16073 @item info functions @var{regexp}
16074 Print the names and data types of all defined functions
16075 whose names contain a match for regular expression @var{regexp}.
16076 Thus, @samp{info fun step} finds all functions whose names
16077 include @code{step}; @samp{info fun ^step} finds those whose names
16078 start with @code{step}. If a function name contains characters
16079 that conflict with the regular expression language (e.g.@:
16080 @samp{operator*()}), they may be quoted with a backslash.
16082 @kindex info variables
16083 @item info variables
16084 Print the names and data types of all variables that are defined
16085 outside of functions (i.e.@: excluding local variables).
16087 @item info variables @var{regexp}
16088 Print the names and data types of all variables (except for local
16089 variables) whose names contain a match for regular expression
16092 @kindex info classes
16093 @cindex Objective-C, classes and selectors
16095 @itemx info classes @var{regexp}
16096 Display all Objective-C classes in your program, or
16097 (with the @var{regexp} argument) all those matching a particular regular
16100 @kindex info selectors
16101 @item info selectors
16102 @itemx info selectors @var{regexp}
16103 Display all Objective-C selectors in your program, or
16104 (with the @var{regexp} argument) all those matching a particular regular
16108 This was never implemented.
16109 @kindex info methods
16111 @itemx info methods @var{regexp}
16112 The @code{info methods} command permits the user to examine all defined
16113 methods within C@t{++} program, or (with the @var{regexp} argument) a
16114 specific set of methods found in the various C@t{++} classes. Many
16115 C@t{++} classes provide a large number of methods. Thus, the output
16116 from the @code{ptype} command can be overwhelming and hard to use. The
16117 @code{info-methods} command filters the methods, printing only those
16118 which match the regular-expression @var{regexp}.
16121 @cindex opaque data types
16122 @kindex set opaque-type-resolution
16123 @item set opaque-type-resolution on
16124 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16125 declared as a pointer to a @code{struct}, @code{class}, or
16126 @code{union}---for example, @code{struct MyType *}---that is used in one
16127 source file although the full declaration of @code{struct MyType} is in
16128 another source file. The default is on.
16130 A change in the setting of this subcommand will not take effect until
16131 the next time symbols for a file are loaded.
16133 @item set opaque-type-resolution off
16134 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16135 is printed as follows:
16137 @{<no data fields>@}
16140 @kindex show opaque-type-resolution
16141 @item show opaque-type-resolution
16142 Show whether opaque types are resolved or not.
16144 @kindex maint print symbols
16145 @cindex symbol dump
16146 @kindex maint print psymbols
16147 @cindex partial symbol dump
16148 @kindex maint print msymbols
16149 @cindex minimal symbol dump
16150 @item maint print symbols @var{filename}
16151 @itemx maint print psymbols @var{filename}
16152 @itemx maint print msymbols @var{filename}
16153 Write a dump of debugging symbol data into the file @var{filename}.
16154 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16155 symbols with debugging data are included. If you use @samp{maint print
16156 symbols}, @value{GDBN} includes all the symbols for which it has already
16157 collected full details: that is, @var{filename} reflects symbols for
16158 only those files whose symbols @value{GDBN} has read. You can use the
16159 command @code{info sources} to find out which files these are. If you
16160 use @samp{maint print psymbols} instead, the dump shows information about
16161 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16162 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16163 @samp{maint print msymbols} dumps just the minimal symbol information
16164 required for each object file from which @value{GDBN} has read some symbols.
16165 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16166 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16168 @kindex maint info symtabs
16169 @kindex maint info psymtabs
16170 @cindex listing @value{GDBN}'s internal symbol tables
16171 @cindex symbol tables, listing @value{GDBN}'s internal
16172 @cindex full symbol tables, listing @value{GDBN}'s internal
16173 @cindex partial symbol tables, listing @value{GDBN}'s internal
16174 @item maint info symtabs @r{[} @var{regexp} @r{]}
16175 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16177 List the @code{struct symtab} or @code{struct partial_symtab}
16178 structures whose names match @var{regexp}. If @var{regexp} is not
16179 given, list them all. The output includes expressions which you can
16180 copy into a @value{GDBN} debugging this one to examine a particular
16181 structure in more detail. For example:
16184 (@value{GDBP}) maint info psymtabs dwarf2read
16185 @{ objfile /home/gnu/build/gdb/gdb
16186 ((struct objfile *) 0x82e69d0)
16187 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16188 ((struct partial_symtab *) 0x8474b10)
16191 text addresses 0x814d3c8 -- 0x8158074
16192 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16193 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16194 dependencies (none)
16197 (@value{GDBP}) maint info symtabs
16201 We see that there is one partial symbol table whose filename contains
16202 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16203 and we see that @value{GDBN} has not read in any symtabs yet at all.
16204 If we set a breakpoint on a function, that will cause @value{GDBN} to
16205 read the symtab for the compilation unit containing that function:
16208 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16209 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16211 (@value{GDBP}) maint info symtabs
16212 @{ objfile /home/gnu/build/gdb/gdb
16213 ((struct objfile *) 0x82e69d0)
16214 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16215 ((struct symtab *) 0x86c1f38)
16218 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16219 linetable ((struct linetable *) 0x8370fa0)
16220 debugformat DWARF 2
16229 @chapter Altering Execution
16231 Once you think you have found an error in your program, you might want to
16232 find out for certain whether correcting the apparent error would lead to
16233 correct results in the rest of the run. You can find the answer by
16234 experiment, using the @value{GDBN} features for altering execution of the
16237 For example, you can store new values into variables or memory
16238 locations, give your program a signal, restart it at a different
16239 address, or even return prematurely from a function.
16242 * Assignment:: Assignment to variables
16243 * Jumping:: Continuing at a different address
16244 * Signaling:: Giving your program a signal
16245 * Returning:: Returning from a function
16246 * Calling:: Calling your program's functions
16247 * Patching:: Patching your program
16251 @section Assignment to Variables
16254 @cindex setting variables
16255 To alter the value of a variable, evaluate an assignment expression.
16256 @xref{Expressions, ,Expressions}. For example,
16263 stores the value 4 into the variable @code{x}, and then prints the
16264 value of the assignment expression (which is 4).
16265 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16266 information on operators in supported languages.
16268 @kindex set variable
16269 @cindex variables, setting
16270 If you are not interested in seeing the value of the assignment, use the
16271 @code{set} command instead of the @code{print} command. @code{set} is
16272 really the same as @code{print} except that the expression's value is
16273 not printed and is not put in the value history (@pxref{Value History,
16274 ,Value History}). The expression is evaluated only for its effects.
16276 If the beginning of the argument string of the @code{set} command
16277 appears identical to a @code{set} subcommand, use the @code{set
16278 variable} command instead of just @code{set}. This command is identical
16279 to @code{set} except for its lack of subcommands. For example, if your
16280 program has a variable @code{width}, you get an error if you try to set
16281 a new value with just @samp{set width=13}, because @value{GDBN} has the
16282 command @code{set width}:
16285 (@value{GDBP}) whatis width
16287 (@value{GDBP}) p width
16289 (@value{GDBP}) set width=47
16290 Invalid syntax in expression.
16294 The invalid expression, of course, is @samp{=47}. In
16295 order to actually set the program's variable @code{width}, use
16298 (@value{GDBP}) set var width=47
16301 Because the @code{set} command has many subcommands that can conflict
16302 with the names of program variables, it is a good idea to use the
16303 @code{set variable} command instead of just @code{set}. For example, if
16304 your program has a variable @code{g}, you run into problems if you try
16305 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16306 the command @code{set gnutarget}, abbreviated @code{set g}:
16310 (@value{GDBP}) whatis g
16314 (@value{GDBP}) set g=4
16318 The program being debugged has been started already.
16319 Start it from the beginning? (y or n) y
16320 Starting program: /home/smith/cc_progs/a.out
16321 "/home/smith/cc_progs/a.out": can't open to read symbols:
16322 Invalid bfd target.
16323 (@value{GDBP}) show g
16324 The current BFD target is "=4".
16329 The program variable @code{g} did not change, and you silently set the
16330 @code{gnutarget} to an invalid value. In order to set the variable
16334 (@value{GDBP}) set var g=4
16337 @value{GDBN} allows more implicit conversions in assignments than C; you can
16338 freely store an integer value into a pointer variable or vice versa,
16339 and you can convert any structure to any other structure that is the
16340 same length or shorter.
16341 @comment FIXME: how do structs align/pad in these conversions?
16342 @comment /doc@cygnus.com 18dec1990
16344 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16345 construct to generate a value of specified type at a specified address
16346 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16347 to memory location @code{0x83040} as an integer (which implies a certain size
16348 and representation in memory), and
16351 set @{int@}0x83040 = 4
16355 stores the value 4 into that memory location.
16358 @section Continuing at a Different Address
16360 Ordinarily, when you continue your program, you do so at the place where
16361 it stopped, with the @code{continue} command. You can instead continue at
16362 an address of your own choosing, with the following commands:
16366 @kindex j @r{(@code{jump})}
16367 @item jump @var{linespec}
16368 @itemx j @var{linespec}
16369 @itemx jump @var{location}
16370 @itemx j @var{location}
16371 Resume execution at line @var{linespec} or at address given by
16372 @var{location}. Execution stops again immediately if there is a
16373 breakpoint there. @xref{Specify Location}, for a description of the
16374 different forms of @var{linespec} and @var{location}. It is common
16375 practice to use the @code{tbreak} command in conjunction with
16376 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16378 The @code{jump} command does not change the current stack frame, or
16379 the stack pointer, or the contents of any memory location or any
16380 register other than the program counter. If line @var{linespec} is in
16381 a different function from the one currently executing, the results may
16382 be bizarre if the two functions expect different patterns of arguments or
16383 of local variables. For this reason, the @code{jump} command requests
16384 confirmation if the specified line is not in the function currently
16385 executing. However, even bizarre results are predictable if you are
16386 well acquainted with the machine-language code of your program.
16389 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16390 On many systems, you can get much the same effect as the @code{jump}
16391 command by storing a new value into the register @code{$pc}. The
16392 difference is that this does not start your program running; it only
16393 changes the address of where it @emph{will} run when you continue. For
16401 makes the next @code{continue} command or stepping command execute at
16402 address @code{0x485}, rather than at the address where your program stopped.
16403 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16405 The most common occasion to use the @code{jump} command is to back
16406 up---perhaps with more breakpoints set---over a portion of a program
16407 that has already executed, in order to examine its execution in more
16412 @section Giving your Program a Signal
16413 @cindex deliver a signal to a program
16417 @item signal @var{signal}
16418 Resume execution where your program stopped, but immediately give it the
16419 signal @var{signal}. @var{signal} can be the name or the number of a
16420 signal. For example, on many systems @code{signal 2} and @code{signal
16421 SIGINT} are both ways of sending an interrupt signal.
16423 Alternatively, if @var{signal} is zero, continue execution without
16424 giving a signal. This is useful when your program stopped on account of
16425 a signal and would ordinarily see the signal when resumed with the
16426 @code{continue} command; @samp{signal 0} causes it to resume without a
16429 @code{signal} does not repeat when you press @key{RET} a second time
16430 after executing the command.
16434 Invoking the @code{signal} command is not the same as invoking the
16435 @code{kill} utility from the shell. Sending a signal with @code{kill}
16436 causes @value{GDBN} to decide what to do with the signal depending on
16437 the signal handling tables (@pxref{Signals}). The @code{signal} command
16438 passes the signal directly to your program.
16442 @section Returning from a Function
16445 @cindex returning from a function
16448 @itemx return @var{expression}
16449 You can cancel execution of a function call with the @code{return}
16450 command. If you give an
16451 @var{expression} argument, its value is used as the function's return
16455 When you use @code{return}, @value{GDBN} discards the selected stack frame
16456 (and all frames within it). You can think of this as making the
16457 discarded frame return prematurely. If you wish to specify a value to
16458 be returned, give that value as the argument to @code{return}.
16460 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16461 Frame}), and any other frames inside of it, leaving its caller as the
16462 innermost remaining frame. That frame becomes selected. The
16463 specified value is stored in the registers used for returning values
16466 The @code{return} command does not resume execution; it leaves the
16467 program stopped in the state that would exist if the function had just
16468 returned. In contrast, the @code{finish} command (@pxref{Continuing
16469 and Stepping, ,Continuing and Stepping}) resumes execution until the
16470 selected stack frame returns naturally.
16472 @value{GDBN} needs to know how the @var{expression} argument should be set for
16473 the inferior. The concrete registers assignment depends on the OS ABI and the
16474 type being returned by the selected stack frame. For example it is common for
16475 OS ABI to return floating point values in FPU registers while integer values in
16476 CPU registers. Still some ABIs return even floating point values in CPU
16477 registers. Larger integer widths (such as @code{long long int}) also have
16478 specific placement rules. @value{GDBN} already knows the OS ABI from its
16479 current target so it needs to find out also the type being returned to make the
16480 assignment into the right register(s).
16482 Normally, the selected stack frame has debug info. @value{GDBN} will always
16483 use the debug info instead of the implicit type of @var{expression} when the
16484 debug info is available. For example, if you type @kbd{return -1}, and the
16485 function in the current stack frame is declared to return a @code{long long
16486 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16487 into a @code{long long int}:
16490 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16492 (@value{GDBP}) return -1
16493 Make func return now? (y or n) y
16494 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16495 43 printf ("result=%lld\n", func ());
16499 However, if the selected stack frame does not have a debug info, e.g., if the
16500 function was compiled without debug info, @value{GDBN} has to find out the type
16501 to return from user. Specifying a different type by mistake may set the value
16502 in different inferior registers than the caller code expects. For example,
16503 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16504 of a @code{long long int} result for a debug info less function (on 32-bit
16505 architectures). Therefore the user is required to specify the return type by
16506 an appropriate cast explicitly:
16509 Breakpoint 2, 0x0040050b in func ()
16510 (@value{GDBP}) return -1
16511 Return value type not available for selected stack frame.
16512 Please use an explicit cast of the value to return.
16513 (@value{GDBP}) return (long long int) -1
16514 Make selected stack frame return now? (y or n) y
16515 #0 0x00400526 in main ()
16520 @section Calling Program Functions
16523 @cindex calling functions
16524 @cindex inferior functions, calling
16525 @item print @var{expr}
16526 Evaluate the expression @var{expr} and display the resulting value.
16527 @var{expr} may include calls to functions in the program being
16531 @item call @var{expr}
16532 Evaluate the expression @var{expr} without displaying @code{void}
16535 You can use this variant of the @code{print} command if you want to
16536 execute a function from your program that does not return anything
16537 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16538 with @code{void} returned values that @value{GDBN} will otherwise
16539 print. If the result is not void, it is printed and saved in the
16543 It is possible for the function you call via the @code{print} or
16544 @code{call} command to generate a signal (e.g., if there's a bug in
16545 the function, or if you passed it incorrect arguments). What happens
16546 in that case is controlled by the @code{set unwindonsignal} command.
16548 Similarly, with a C@t{++} program it is possible for the function you
16549 call via the @code{print} or @code{call} command to generate an
16550 exception that is not handled due to the constraints of the dummy
16551 frame. In this case, any exception that is raised in the frame, but has
16552 an out-of-frame exception handler will not be found. GDB builds a
16553 dummy-frame for the inferior function call, and the unwinder cannot
16554 seek for exception handlers outside of this dummy-frame. What happens
16555 in that case is controlled by the
16556 @code{set unwind-on-terminating-exception} command.
16559 @item set unwindonsignal
16560 @kindex set unwindonsignal
16561 @cindex unwind stack in called functions
16562 @cindex call dummy stack unwinding
16563 Set unwinding of the stack if a signal is received while in a function
16564 that @value{GDBN} called in the program being debugged. If set to on,
16565 @value{GDBN} unwinds the stack it created for the call and restores
16566 the context to what it was before the call. If set to off (the
16567 default), @value{GDBN} stops in the frame where the signal was
16570 @item show unwindonsignal
16571 @kindex show unwindonsignal
16572 Show the current setting of stack unwinding in the functions called by
16575 @item set unwind-on-terminating-exception
16576 @kindex set unwind-on-terminating-exception
16577 @cindex unwind stack in called functions with unhandled exceptions
16578 @cindex call dummy stack unwinding on unhandled exception.
16579 Set unwinding of the stack if a C@t{++} exception is raised, but left
16580 unhandled while in a function that @value{GDBN} called in the program being
16581 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16582 it created for the call and restores the context to what it was before
16583 the call. If set to off, @value{GDBN} the exception is delivered to
16584 the default C@t{++} exception handler and the inferior terminated.
16586 @item show unwind-on-terminating-exception
16587 @kindex show unwind-on-terminating-exception
16588 Show the current setting of stack unwinding in the functions called by
16593 @cindex weak alias functions
16594 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16595 for another function. In such case, @value{GDBN} might not pick up
16596 the type information, including the types of the function arguments,
16597 which causes @value{GDBN} to call the inferior function incorrectly.
16598 As a result, the called function will function erroneously and may
16599 even crash. A solution to that is to use the name of the aliased
16603 @section Patching Programs
16605 @cindex patching binaries
16606 @cindex writing into executables
16607 @cindex writing into corefiles
16609 By default, @value{GDBN} opens the file containing your program's
16610 executable code (or the corefile) read-only. This prevents accidental
16611 alterations to machine code; but it also prevents you from intentionally
16612 patching your program's binary.
16614 If you'd like to be able to patch the binary, you can specify that
16615 explicitly with the @code{set write} command. For example, you might
16616 want to turn on internal debugging flags, or even to make emergency
16622 @itemx set write off
16623 If you specify @samp{set write on}, @value{GDBN} opens executable and
16624 core files for both reading and writing; if you specify @kbd{set write
16625 off} (the default), @value{GDBN} opens them read-only.
16627 If you have already loaded a file, you must load it again (using the
16628 @code{exec-file} or @code{core-file} command) after changing @code{set
16629 write}, for your new setting to take effect.
16633 Display whether executable files and core files are opened for writing
16634 as well as reading.
16638 @chapter @value{GDBN} Files
16640 @value{GDBN} needs to know the file name of the program to be debugged,
16641 both in order to read its symbol table and in order to start your
16642 program. To debug a core dump of a previous run, you must also tell
16643 @value{GDBN} the name of the core dump file.
16646 * Files:: Commands to specify files
16647 * Separate Debug Files:: Debugging information in separate files
16648 * MiniDebugInfo:: Debugging information in a special section
16649 * Index Files:: Index files speed up GDB
16650 * Symbol Errors:: Errors reading symbol files
16651 * Data Files:: GDB data files
16655 @section Commands to Specify Files
16657 @cindex symbol table
16658 @cindex core dump file
16660 You may want to specify executable and core dump file names. The usual
16661 way to do this is at start-up time, using the arguments to
16662 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16663 Out of @value{GDBN}}).
16665 Occasionally it is necessary to change to a different file during a
16666 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16667 specify a file you want to use. Or you are debugging a remote target
16668 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16669 Program}). In these situations the @value{GDBN} commands to specify
16670 new files are useful.
16673 @cindex executable file
16675 @item file @var{filename}
16676 Use @var{filename} as the program to be debugged. It is read for its
16677 symbols and for the contents of pure memory. It is also the program
16678 executed when you use the @code{run} command. If you do not specify a
16679 directory and the file is not found in the @value{GDBN} working directory,
16680 @value{GDBN} uses the environment variable @code{PATH} as a list of
16681 directories to search, just as the shell does when looking for a program
16682 to run. You can change the value of this variable, for both @value{GDBN}
16683 and your program, using the @code{path} command.
16685 @cindex unlinked object files
16686 @cindex patching object files
16687 You can load unlinked object @file{.o} files into @value{GDBN} using
16688 the @code{file} command. You will not be able to ``run'' an object
16689 file, but you can disassemble functions and inspect variables. Also,
16690 if the underlying BFD functionality supports it, you could use
16691 @kbd{gdb -write} to patch object files using this technique. Note
16692 that @value{GDBN} can neither interpret nor modify relocations in this
16693 case, so branches and some initialized variables will appear to go to
16694 the wrong place. But this feature is still handy from time to time.
16697 @code{file} with no argument makes @value{GDBN} discard any information it
16698 has on both executable file and the symbol table.
16701 @item exec-file @r{[} @var{filename} @r{]}
16702 Specify that the program to be run (but not the symbol table) is found
16703 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16704 if necessary to locate your program. Omitting @var{filename} means to
16705 discard information on the executable file.
16707 @kindex symbol-file
16708 @item symbol-file @r{[} @var{filename} @r{]}
16709 Read symbol table information from file @var{filename}. @code{PATH} is
16710 searched when necessary. Use the @code{file} command to get both symbol
16711 table and program to run from the same file.
16713 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16714 program's symbol table.
16716 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16717 some breakpoints and auto-display expressions. This is because they may
16718 contain pointers to the internal data recording symbols and data types,
16719 which are part of the old symbol table data being discarded inside
16722 @code{symbol-file} does not repeat if you press @key{RET} again after
16725 When @value{GDBN} is configured for a particular environment, it
16726 understands debugging information in whatever format is the standard
16727 generated for that environment; you may use either a @sc{gnu} compiler, or
16728 other compilers that adhere to the local conventions.
16729 Best results are usually obtained from @sc{gnu} compilers; for example,
16730 using @code{@value{NGCC}} you can generate debugging information for
16733 For most kinds of object files, with the exception of old SVR3 systems
16734 using COFF, the @code{symbol-file} command does not normally read the
16735 symbol table in full right away. Instead, it scans the symbol table
16736 quickly to find which source files and which symbols are present. The
16737 details are read later, one source file at a time, as they are needed.
16739 The purpose of this two-stage reading strategy is to make @value{GDBN}
16740 start up faster. For the most part, it is invisible except for
16741 occasional pauses while the symbol table details for a particular source
16742 file are being read. (The @code{set verbose} command can turn these
16743 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16744 Warnings and Messages}.)
16746 We have not implemented the two-stage strategy for COFF yet. When the
16747 symbol table is stored in COFF format, @code{symbol-file} reads the
16748 symbol table data in full right away. Note that ``stabs-in-COFF''
16749 still does the two-stage strategy, since the debug info is actually
16753 @cindex reading symbols immediately
16754 @cindex symbols, reading immediately
16755 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16756 @itemx file @r{[} -readnow @r{]} @var{filename}
16757 You can override the @value{GDBN} two-stage strategy for reading symbol
16758 tables by using the @samp{-readnow} option with any of the commands that
16759 load symbol table information, if you want to be sure @value{GDBN} has the
16760 entire symbol table available.
16762 @c FIXME: for now no mention of directories, since this seems to be in
16763 @c flux. 13mar1992 status is that in theory GDB would look either in
16764 @c current dir or in same dir as myprog; but issues like competing
16765 @c GDB's, or clutter in system dirs, mean that in practice right now
16766 @c only current dir is used. FFish says maybe a special GDB hierarchy
16767 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16771 @item core-file @r{[}@var{filename}@r{]}
16773 Specify the whereabouts of a core dump file to be used as the ``contents
16774 of memory''. Traditionally, core files contain only some parts of the
16775 address space of the process that generated them; @value{GDBN} can access the
16776 executable file itself for other parts.
16778 @code{core-file} with no argument specifies that no core file is
16781 Note that the core file is ignored when your program is actually running
16782 under @value{GDBN}. So, if you have been running your program and you
16783 wish to debug a core file instead, you must kill the subprocess in which
16784 the program is running. To do this, use the @code{kill} command
16785 (@pxref{Kill Process, ,Killing the Child Process}).
16787 @kindex add-symbol-file
16788 @cindex dynamic linking
16789 @item add-symbol-file @var{filename} @var{address}
16790 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16791 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16792 The @code{add-symbol-file} command reads additional symbol table
16793 information from the file @var{filename}. You would use this command
16794 when @var{filename} has been dynamically loaded (by some other means)
16795 into the program that is running. @var{address} should be the memory
16796 address at which the file has been loaded; @value{GDBN} cannot figure
16797 this out for itself. You can additionally specify an arbitrary number
16798 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16799 section name and base address for that section. You can specify any
16800 @var{address} as an expression.
16802 The symbol table of the file @var{filename} is added to the symbol table
16803 originally read with the @code{symbol-file} command. You can use the
16804 @code{add-symbol-file} command any number of times; the new symbol data
16805 thus read is kept in addition to the old.
16807 Changes can be reverted using the command @code{remove-symbol-file}.
16809 @cindex relocatable object files, reading symbols from
16810 @cindex object files, relocatable, reading symbols from
16811 @cindex reading symbols from relocatable object files
16812 @cindex symbols, reading from relocatable object files
16813 @cindex @file{.o} files, reading symbols from
16814 Although @var{filename} is typically a shared library file, an
16815 executable file, or some other object file which has been fully
16816 relocated for loading into a process, you can also load symbolic
16817 information from relocatable @file{.o} files, as long as:
16821 the file's symbolic information refers only to linker symbols defined in
16822 that file, not to symbols defined by other object files,
16824 every section the file's symbolic information refers to has actually
16825 been loaded into the inferior, as it appears in the file, and
16827 you can determine the address at which every section was loaded, and
16828 provide these to the @code{add-symbol-file} command.
16832 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16833 relocatable files into an already running program; such systems
16834 typically make the requirements above easy to meet. However, it's
16835 important to recognize that many native systems use complex link
16836 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16837 assembly, for example) that make the requirements difficult to meet. In
16838 general, one cannot assume that using @code{add-symbol-file} to read a
16839 relocatable object file's symbolic information will have the same effect
16840 as linking the relocatable object file into the program in the normal
16843 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16845 @kindex remove-symbol-file
16846 @item remove-symbol-file @var{filename}
16847 @item remove-symbol-file -a @var{address}
16848 Remove a symbol file added via the @code{add-symbol-file} command. The
16849 file to remove can be identified by its @var{filename} or by an @var{address}
16850 that lies within the boundaries of this symbol file in memory. Example:
16853 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16854 add symbol table from file "/home/user/gdb/mylib.so" at
16855 .text_addr = 0x7ffff7ff9480
16857 Reading symbols from /home/user/gdb/mylib.so...done.
16858 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16859 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16864 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16866 @kindex add-symbol-file-from-memory
16867 @cindex @code{syscall DSO}
16868 @cindex load symbols from memory
16869 @item add-symbol-file-from-memory @var{address}
16870 Load symbols from the given @var{address} in a dynamically loaded
16871 object file whose image is mapped directly into the inferior's memory.
16872 For example, the Linux kernel maps a @code{syscall DSO} into each
16873 process's address space; this DSO provides kernel-specific code for
16874 some system calls. The argument can be any expression whose
16875 evaluation yields the address of the file's shared object file header.
16876 For this command to work, you must have used @code{symbol-file} or
16877 @code{exec-file} commands in advance.
16879 @kindex add-shared-symbol-files
16881 @item add-shared-symbol-files @var{library-file}
16882 @itemx assf @var{library-file}
16883 The @code{add-shared-symbol-files} command can currently be used only
16884 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16885 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16886 @value{GDBN} automatically looks for shared libraries, however if
16887 @value{GDBN} does not find yours, you can invoke
16888 @code{add-shared-symbol-files}. It takes one argument: the shared
16889 library's file name. @code{assf} is a shorthand alias for
16890 @code{add-shared-symbol-files}.
16893 @item section @var{section} @var{addr}
16894 The @code{section} command changes the base address of the named
16895 @var{section} of the exec file to @var{addr}. This can be used if the
16896 exec file does not contain section addresses, (such as in the
16897 @code{a.out} format), or when the addresses specified in the file
16898 itself are wrong. Each section must be changed separately. The
16899 @code{info files} command, described below, lists all the sections and
16903 @kindex info target
16906 @code{info files} and @code{info target} are synonymous; both print the
16907 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16908 including the names of the executable and core dump files currently in
16909 use by @value{GDBN}, and the files from which symbols were loaded. The
16910 command @code{help target} lists all possible targets rather than
16913 @kindex maint info sections
16914 @item maint info sections
16915 Another command that can give you extra information about program sections
16916 is @code{maint info sections}. In addition to the section information
16917 displayed by @code{info files}, this command displays the flags and file
16918 offset of each section in the executable and core dump files. In addition,
16919 @code{maint info sections} provides the following command options (which
16920 may be arbitrarily combined):
16924 Display sections for all loaded object files, including shared libraries.
16925 @item @var{sections}
16926 Display info only for named @var{sections}.
16927 @item @var{section-flags}
16928 Display info only for sections for which @var{section-flags} are true.
16929 The section flags that @value{GDBN} currently knows about are:
16932 Section will have space allocated in the process when loaded.
16933 Set for all sections except those containing debug information.
16935 Section will be loaded from the file into the child process memory.
16936 Set for pre-initialized code and data, clear for @code{.bss} sections.
16938 Section needs to be relocated before loading.
16940 Section cannot be modified by the child process.
16942 Section contains executable code only.
16944 Section contains data only (no executable code).
16946 Section will reside in ROM.
16948 Section contains data for constructor/destructor lists.
16950 Section is not empty.
16952 An instruction to the linker to not output the section.
16953 @item COFF_SHARED_LIBRARY
16954 A notification to the linker that the section contains
16955 COFF shared library information.
16957 Section contains common symbols.
16960 @kindex set trust-readonly-sections
16961 @cindex read-only sections
16962 @item set trust-readonly-sections on
16963 Tell @value{GDBN} that readonly sections in your object file
16964 really are read-only (i.e.@: that their contents will not change).
16965 In that case, @value{GDBN} can fetch values from these sections
16966 out of the object file, rather than from the target program.
16967 For some targets (notably embedded ones), this can be a significant
16968 enhancement to debugging performance.
16970 The default is off.
16972 @item set trust-readonly-sections off
16973 Tell @value{GDBN} not to trust readonly sections. This means that
16974 the contents of the section might change while the program is running,
16975 and must therefore be fetched from the target when needed.
16977 @item show trust-readonly-sections
16978 Show the current setting of trusting readonly sections.
16981 All file-specifying commands allow both absolute and relative file names
16982 as arguments. @value{GDBN} always converts the file name to an absolute file
16983 name and remembers it that way.
16985 @cindex shared libraries
16986 @anchor{Shared Libraries}
16987 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16988 and IBM RS/6000 AIX shared libraries.
16990 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16991 shared libraries. @xref{Expat}.
16993 @value{GDBN} automatically loads symbol definitions from shared libraries
16994 when you use the @code{run} command, or when you examine a core file.
16995 (Before you issue the @code{run} command, @value{GDBN} does not understand
16996 references to a function in a shared library, however---unless you are
16997 debugging a core file).
16999 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17000 automatically loads the symbols at the time of the @code{shl_load} call.
17002 @c FIXME: some @value{GDBN} release may permit some refs to undef
17003 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17004 @c FIXME...lib; check this from time to time when updating manual
17006 There are times, however, when you may wish to not automatically load
17007 symbol definitions from shared libraries, such as when they are
17008 particularly large or there are many of them.
17010 To control the automatic loading of shared library symbols, use the
17014 @kindex set auto-solib-add
17015 @item set auto-solib-add @var{mode}
17016 If @var{mode} is @code{on}, symbols from all shared object libraries
17017 will be loaded automatically when the inferior begins execution, you
17018 attach to an independently started inferior, or when the dynamic linker
17019 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17020 is @code{off}, symbols must be loaded manually, using the
17021 @code{sharedlibrary} command. The default value is @code{on}.
17023 @cindex memory used for symbol tables
17024 If your program uses lots of shared libraries with debug info that
17025 takes large amounts of memory, you can decrease the @value{GDBN}
17026 memory footprint by preventing it from automatically loading the
17027 symbols from shared libraries. To that end, type @kbd{set
17028 auto-solib-add off} before running the inferior, then load each
17029 library whose debug symbols you do need with @kbd{sharedlibrary
17030 @var{regexp}}, where @var{regexp} is a regular expression that matches
17031 the libraries whose symbols you want to be loaded.
17033 @kindex show auto-solib-add
17034 @item show auto-solib-add
17035 Display the current autoloading mode.
17038 @cindex load shared library
17039 To explicitly load shared library symbols, use the @code{sharedlibrary}
17043 @kindex info sharedlibrary
17045 @item info share @var{regex}
17046 @itemx info sharedlibrary @var{regex}
17047 Print the names of the shared libraries which are currently loaded
17048 that match @var{regex}. If @var{regex} is omitted then print
17049 all shared libraries that are loaded.
17051 @kindex sharedlibrary
17053 @item sharedlibrary @var{regex}
17054 @itemx share @var{regex}
17055 Load shared object library symbols for files matching a
17056 Unix regular expression.
17057 As with files loaded automatically, it only loads shared libraries
17058 required by your program for a core file or after typing @code{run}. If
17059 @var{regex} is omitted all shared libraries required by your program are
17062 @item nosharedlibrary
17063 @kindex nosharedlibrary
17064 @cindex unload symbols from shared libraries
17065 Unload all shared object library symbols. This discards all symbols
17066 that have been loaded from all shared libraries. Symbols from shared
17067 libraries that were loaded by explicit user requests are not
17071 Sometimes you may wish that @value{GDBN} stops and gives you control
17072 when any of shared library events happen. The best way to do this is
17073 to use @code{catch load} and @code{catch unload} (@pxref{Set
17076 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17077 command for this. This command exists for historical reasons. It is
17078 less useful than setting a catchpoint, because it does not allow for
17079 conditions or commands as a catchpoint does.
17082 @item set stop-on-solib-events
17083 @kindex set stop-on-solib-events
17084 This command controls whether @value{GDBN} should give you control
17085 when the dynamic linker notifies it about some shared library event.
17086 The most common event of interest is loading or unloading of a new
17089 @item show stop-on-solib-events
17090 @kindex show stop-on-solib-events
17091 Show whether @value{GDBN} stops and gives you control when shared
17092 library events happen.
17095 Shared libraries are also supported in many cross or remote debugging
17096 configurations. @value{GDBN} needs to have access to the target's libraries;
17097 this can be accomplished either by providing copies of the libraries
17098 on the host system, or by asking @value{GDBN} to automatically retrieve the
17099 libraries from the target. If copies of the target libraries are
17100 provided, they need to be the same as the target libraries, although the
17101 copies on the target can be stripped as long as the copies on the host are
17104 @cindex where to look for shared libraries
17105 For remote debugging, you need to tell @value{GDBN} where the target
17106 libraries are, so that it can load the correct copies---otherwise, it
17107 may try to load the host's libraries. @value{GDBN} has two variables
17108 to specify the search directories for target libraries.
17111 @cindex prefix for shared library file names
17112 @cindex system root, alternate
17113 @kindex set solib-absolute-prefix
17114 @kindex set sysroot
17115 @item set sysroot @var{path}
17116 Use @var{path} as the system root for the program being debugged. Any
17117 absolute shared library paths will be prefixed with @var{path}; many
17118 runtime loaders store the absolute paths to the shared library in the
17119 target program's memory. If you use @code{set sysroot} to find shared
17120 libraries, they need to be laid out in the same way that they are on
17121 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17124 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17125 retrieve the target libraries from the remote system. This is only
17126 supported when using a remote target that supports the @code{remote get}
17127 command (@pxref{File Transfer,,Sending files to a remote system}).
17128 The part of @var{path} following the initial @file{remote:}
17129 (if present) is used as system root prefix on the remote file system.
17130 @footnote{If you want to specify a local system root using a directory
17131 that happens to be named @file{remote:}, you need to use some equivalent
17132 variant of the name like @file{./remote:}.}
17134 For targets with an MS-DOS based filesystem, such as MS-Windows and
17135 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17136 absolute file name with @var{path}. But first, on Unix hosts,
17137 @value{GDBN} converts all backslash directory separators into forward
17138 slashes, because the backslash is not a directory separator on Unix:
17141 c:\foo\bar.dll @result{} c:/foo/bar.dll
17144 Then, @value{GDBN} attempts prefixing the target file name with
17145 @var{path}, and looks for the resulting file name in the host file
17149 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17152 If that does not find the shared library, @value{GDBN} tries removing
17153 the @samp{:} character from the drive spec, both for convenience, and,
17154 for the case of the host file system not supporting file names with
17158 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17161 This makes it possible to have a system root that mirrors a target
17162 with more than one drive. E.g., you may want to setup your local
17163 copies of the target system shared libraries like so (note @samp{c} vs
17167 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17168 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17169 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17173 and point the system root at @file{/path/to/sysroot}, so that
17174 @value{GDBN} can find the correct copies of both
17175 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17177 If that still does not find the shared library, @value{GDBN} tries
17178 removing the whole drive spec from the target file name:
17181 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17184 This last lookup makes it possible to not care about the drive name,
17185 if you don't want or need to.
17187 The @code{set solib-absolute-prefix} command is an alias for @code{set
17190 @cindex default system root
17191 @cindex @samp{--with-sysroot}
17192 You can set the default system root by using the configure-time
17193 @samp{--with-sysroot} option. If the system root is inside
17194 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17195 @samp{--exec-prefix}), then the default system root will be updated
17196 automatically if the installed @value{GDBN} is moved to a new
17199 @kindex show sysroot
17201 Display the current shared library prefix.
17203 @kindex set solib-search-path
17204 @item set solib-search-path @var{path}
17205 If this variable is set, @var{path} is a colon-separated list of
17206 directories to search for shared libraries. @samp{solib-search-path}
17207 is used after @samp{sysroot} fails to locate the library, or if the
17208 path to the library is relative instead of absolute. If you want to
17209 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17210 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17211 finding your host's libraries. @samp{sysroot} is preferred; setting
17212 it to a nonexistent directory may interfere with automatic loading
17213 of shared library symbols.
17215 @kindex show solib-search-path
17216 @item show solib-search-path
17217 Display the current shared library search path.
17219 @cindex DOS file-name semantics of file names.
17220 @kindex set target-file-system-kind (unix|dos-based|auto)
17221 @kindex show target-file-system-kind
17222 @item set target-file-system-kind @var{kind}
17223 Set assumed file system kind for target reported file names.
17225 Shared library file names as reported by the target system may not
17226 make sense as is on the system @value{GDBN} is running on. For
17227 example, when remote debugging a target that has MS-DOS based file
17228 system semantics, from a Unix host, the target may be reporting to
17229 @value{GDBN} a list of loaded shared libraries with file names such as
17230 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17231 drive letters, so the @samp{c:\} prefix is not normally understood as
17232 indicating an absolute file name, and neither is the backslash
17233 normally considered a directory separator character. In that case,
17234 the native file system would interpret this whole absolute file name
17235 as a relative file name with no directory components. This would make
17236 it impossible to point @value{GDBN} at a copy of the remote target's
17237 shared libraries on the host using @code{set sysroot}, and impractical
17238 with @code{set solib-search-path}. Setting
17239 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17240 to interpret such file names similarly to how the target would, and to
17241 map them to file names valid on @value{GDBN}'s native file system
17242 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17243 to one of the supported file system kinds. In that case, @value{GDBN}
17244 tries to determine the appropriate file system variant based on the
17245 current target's operating system (@pxref{ABI, ,Configuring the
17246 Current ABI}). The supported file system settings are:
17250 Instruct @value{GDBN} to assume the target file system is of Unix
17251 kind. Only file names starting the forward slash (@samp{/}) character
17252 are considered absolute, and the directory separator character is also
17256 Instruct @value{GDBN} to assume the target file system is DOS based.
17257 File names starting with either a forward slash, or a drive letter
17258 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17259 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17260 considered directory separators.
17263 Instruct @value{GDBN} to use the file system kind associated with the
17264 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17265 This is the default.
17269 @cindex file name canonicalization
17270 @cindex base name differences
17271 When processing file names provided by the user, @value{GDBN}
17272 frequently needs to compare them to the file names recorded in the
17273 program's debug info. Normally, @value{GDBN} compares just the
17274 @dfn{base names} of the files as strings, which is reasonably fast
17275 even for very large programs. (The base name of a file is the last
17276 portion of its name, after stripping all the leading directories.)
17277 This shortcut in comparison is based upon the assumption that files
17278 cannot have more than one base name. This is usually true, but
17279 references to files that use symlinks or similar filesystem
17280 facilities violate that assumption. If your program records files
17281 using such facilities, or if you provide file names to @value{GDBN}
17282 using symlinks etc., you can set @code{basenames-may-differ} to
17283 @code{true} to instruct @value{GDBN} to completely canonicalize each
17284 pair of file names it needs to compare. This will make file-name
17285 comparisons accurate, but at a price of a significant slowdown.
17288 @item set basenames-may-differ
17289 @kindex set basenames-may-differ
17290 Set whether a source file may have multiple base names.
17292 @item show basenames-may-differ
17293 @kindex show basenames-may-differ
17294 Show whether a source file may have multiple base names.
17297 @node Separate Debug Files
17298 @section Debugging Information in Separate Files
17299 @cindex separate debugging information files
17300 @cindex debugging information in separate files
17301 @cindex @file{.debug} subdirectories
17302 @cindex debugging information directory, global
17303 @cindex global debugging information directories
17304 @cindex build ID, and separate debugging files
17305 @cindex @file{.build-id} directory
17307 @value{GDBN} allows you to put a program's debugging information in a
17308 file separate from the executable itself, in a way that allows
17309 @value{GDBN} to find and load the debugging information automatically.
17310 Since debugging information can be very large---sometimes larger
17311 than the executable code itself---some systems distribute debugging
17312 information for their executables in separate files, which users can
17313 install only when they need to debug a problem.
17315 @value{GDBN} supports two ways of specifying the separate debug info
17320 The executable contains a @dfn{debug link} that specifies the name of
17321 the separate debug info file. The separate debug file's name is
17322 usually @file{@var{executable}.debug}, where @var{executable} is the
17323 name of the corresponding executable file without leading directories
17324 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17325 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17326 checksum for the debug file, which @value{GDBN} uses to validate that
17327 the executable and the debug file came from the same build.
17330 The executable contains a @dfn{build ID}, a unique bit string that is
17331 also present in the corresponding debug info file. (This is supported
17332 only on some operating systems, notably those which use the ELF format
17333 for binary files and the @sc{gnu} Binutils.) For more details about
17334 this feature, see the description of the @option{--build-id}
17335 command-line option in @ref{Options, , Command Line Options, ld.info,
17336 The GNU Linker}. The debug info file's name is not specified
17337 explicitly by the build ID, but can be computed from the build ID, see
17341 Depending on the way the debug info file is specified, @value{GDBN}
17342 uses two different methods of looking for the debug file:
17346 For the ``debug link'' method, @value{GDBN} looks up the named file in
17347 the directory of the executable file, then in a subdirectory of that
17348 directory named @file{.debug}, and finally under each one of the global debug
17349 directories, in a subdirectory whose name is identical to the leading
17350 directories of the executable's absolute file name.
17353 For the ``build ID'' method, @value{GDBN} looks in the
17354 @file{.build-id} subdirectory of each one of the global debug directories for
17355 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17356 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17357 are the rest of the bit string. (Real build ID strings are 32 or more
17358 hex characters, not 10.)
17361 So, for example, suppose you ask @value{GDBN} to debug
17362 @file{/usr/bin/ls}, which has a debug link that specifies the
17363 file @file{ls.debug}, and a build ID whose value in hex is
17364 @code{abcdef1234}. If the list of the global debug directories includes
17365 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17366 debug information files, in the indicated order:
17370 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17372 @file{/usr/bin/ls.debug}
17374 @file{/usr/bin/.debug/ls.debug}
17376 @file{/usr/lib/debug/usr/bin/ls.debug}.
17379 @anchor{debug-file-directory}
17380 Global debugging info directories default to what is set by @value{GDBN}
17381 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17382 you can also set the global debugging info directories, and view the list
17383 @value{GDBN} is currently using.
17387 @kindex set debug-file-directory
17388 @item set debug-file-directory @var{directories}
17389 Set the directories which @value{GDBN} searches for separate debugging
17390 information files to @var{directory}. Multiple path components can be set
17391 concatenating them by a path separator.
17393 @kindex show debug-file-directory
17394 @item show debug-file-directory
17395 Show the directories @value{GDBN} searches for separate debugging
17400 @cindex @code{.gnu_debuglink} sections
17401 @cindex debug link sections
17402 A debug link is a special section of the executable file named
17403 @code{.gnu_debuglink}. The section must contain:
17407 A filename, with any leading directory components removed, followed by
17410 zero to three bytes of padding, as needed to reach the next four-byte
17411 boundary within the section, and
17413 a four-byte CRC checksum, stored in the same endianness used for the
17414 executable file itself. The checksum is computed on the debugging
17415 information file's full contents by the function given below, passing
17416 zero as the @var{crc} argument.
17419 Any executable file format can carry a debug link, as long as it can
17420 contain a section named @code{.gnu_debuglink} with the contents
17423 @cindex @code{.note.gnu.build-id} sections
17424 @cindex build ID sections
17425 The build ID is a special section in the executable file (and in other
17426 ELF binary files that @value{GDBN} may consider). This section is
17427 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17428 It contains unique identification for the built files---the ID remains
17429 the same across multiple builds of the same build tree. The default
17430 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17431 content for the build ID string. The same section with an identical
17432 value is present in the original built binary with symbols, in its
17433 stripped variant, and in the separate debugging information file.
17435 The debugging information file itself should be an ordinary
17436 executable, containing a full set of linker symbols, sections, and
17437 debugging information. The sections of the debugging information file
17438 should have the same names, addresses, and sizes as the original file,
17439 but they need not contain any data---much like a @code{.bss} section
17440 in an ordinary executable.
17442 The @sc{gnu} binary utilities (Binutils) package includes the
17443 @samp{objcopy} utility that can produce
17444 the separated executable / debugging information file pairs using the
17445 following commands:
17448 @kbd{objcopy --only-keep-debug foo foo.debug}
17453 These commands remove the debugging
17454 information from the executable file @file{foo} and place it in the file
17455 @file{foo.debug}. You can use the first, second or both methods to link the
17460 The debug link method needs the following additional command to also leave
17461 behind a debug link in @file{foo}:
17464 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17467 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17468 a version of the @code{strip} command such that the command @kbd{strip foo -f
17469 foo.debug} has the same functionality as the two @code{objcopy} commands and
17470 the @code{ln -s} command above, together.
17473 Build ID gets embedded into the main executable using @code{ld --build-id} or
17474 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17475 compatibility fixes for debug files separation are present in @sc{gnu} binary
17476 utilities (Binutils) package since version 2.18.
17481 @cindex CRC algorithm definition
17482 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17483 IEEE 802.3 using the polynomial:
17485 @c TexInfo requires naked braces for multi-digit exponents for Tex
17486 @c output, but this causes HTML output to barf. HTML has to be set using
17487 @c raw commands. So we end up having to specify this equation in 2
17492 <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>
17493 + <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
17499 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17500 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17504 The function is computed byte at a time, taking the least
17505 significant bit of each byte first. The initial pattern
17506 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17507 the final result is inverted to ensure trailing zeros also affect the
17510 @emph{Note:} This is the same CRC polynomial as used in handling the
17511 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17512 , @value{GDBN} Remote Serial Protocol}). However in the
17513 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17514 significant bit first, and the result is not inverted, so trailing
17515 zeros have no effect on the CRC value.
17517 To complete the description, we show below the code of the function
17518 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17519 initially supplied @code{crc} argument means that an initial call to
17520 this function passing in zero will start computing the CRC using
17523 @kindex gnu_debuglink_crc32
17526 gnu_debuglink_crc32 (unsigned long crc,
17527 unsigned char *buf, size_t len)
17529 static const unsigned long crc32_table[256] =
17531 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17532 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17533 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17534 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17535 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17536 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17537 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17538 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17539 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17540 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17541 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17542 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17543 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17544 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17545 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17546 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17547 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17548 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17549 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17550 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17551 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17552 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17553 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17554 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17555 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17556 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17557 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17558 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17559 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17560 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17561 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17562 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17563 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17564 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17565 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17566 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17567 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17568 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17569 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17570 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17571 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17572 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17573 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17574 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17575 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17576 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17577 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17578 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17579 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17580 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17581 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17584 unsigned char *end;
17586 crc = ~crc & 0xffffffff;
17587 for (end = buf + len; buf < end; ++buf)
17588 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17589 return ~crc & 0xffffffff;
17594 This computation does not apply to the ``build ID'' method.
17596 @node MiniDebugInfo
17597 @section Debugging information in a special section
17598 @cindex separate debug sections
17599 @cindex @samp{.gnu_debugdata} section
17601 Some systems ship pre-built executables and libraries that have a
17602 special @samp{.gnu_debugdata} section. This feature is called
17603 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17604 is used to supply extra symbols for backtraces.
17606 The intent of this section is to provide extra minimal debugging
17607 information for use in simple backtraces. It is not intended to be a
17608 replacement for full separate debugging information (@pxref{Separate
17609 Debug Files}). The example below shows the intended use; however,
17610 @value{GDBN} does not currently put restrictions on what sort of
17611 debugging information might be included in the section.
17613 @value{GDBN} has support for this extension. If the section exists,
17614 then it is used provided that no other source of debugging information
17615 can be found, and that @value{GDBN} was configured with LZMA support.
17617 This section can be easily created using @command{objcopy} and other
17618 standard utilities:
17621 # Extract the dynamic symbols from the main binary, there is no need
17622 # to also have these in the normal symbol table.
17623 nm -D @var{binary} --format=posix --defined-only \
17624 | awk '@{ print $1 @}' | sort > dynsyms
17626 # Extract all the text (i.e. function) symbols from the debuginfo.
17627 # (Note that we actually also accept "D" symbols, for the benefit
17628 # of platforms like PowerPC64 that use function descriptors.)
17629 nm @var{binary} --format=posix --defined-only \
17630 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17633 # Keep all the function symbols not already in the dynamic symbol
17635 comm -13 dynsyms funcsyms > keep_symbols
17637 # Separate full debug info into debug binary.
17638 objcopy --only-keep-debug @var{binary} debug
17640 # Copy the full debuginfo, keeping only a minimal set of symbols and
17641 # removing some unnecessary sections.
17642 objcopy -S --remove-section .gdb_index --remove-section .comment \
17643 --keep-symbols=keep_symbols debug mini_debuginfo
17645 # Drop the full debug info from the original binary.
17646 strip --strip-all -R .comment @var{binary}
17648 # Inject the compressed data into the .gnu_debugdata section of the
17651 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17655 @section Index Files Speed Up @value{GDBN}
17656 @cindex index files
17657 @cindex @samp{.gdb_index} section
17659 When @value{GDBN} finds a symbol file, it scans the symbols in the
17660 file in order to construct an internal symbol table. This lets most
17661 @value{GDBN} operations work quickly---at the cost of a delay early
17662 on. For large programs, this delay can be quite lengthy, so
17663 @value{GDBN} provides a way to build an index, which speeds up
17666 The index is stored as a section in the symbol file. @value{GDBN} can
17667 write the index to a file, then you can put it into the symbol file
17668 using @command{objcopy}.
17670 To create an index file, use the @code{save gdb-index} command:
17673 @item save gdb-index @var{directory}
17674 @kindex save gdb-index
17675 Create an index file for each symbol file currently known by
17676 @value{GDBN}. Each file is named after its corresponding symbol file,
17677 with @samp{.gdb-index} appended, and is written into the given
17681 Once you have created an index file you can merge it into your symbol
17682 file, here named @file{symfile}, using @command{objcopy}:
17685 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17686 --set-section-flags .gdb_index=readonly symfile symfile
17689 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17690 sections that have been deprecated. Usually they are deprecated because
17691 they are missing a new feature or have performance issues.
17692 To tell @value{GDBN} to use a deprecated index section anyway
17693 specify @code{set use-deprecated-index-sections on}.
17694 The default is @code{off}.
17695 This can speed up startup, but may result in some functionality being lost.
17696 @xref{Index Section Format}.
17698 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17699 must be done before gdb reads the file. The following will not work:
17702 $ gdb -ex "set use-deprecated-index-sections on" <program>
17705 Instead you must do, for example,
17708 $ gdb -iex "set use-deprecated-index-sections on" <program>
17711 There are currently some limitation on indices. They only work when
17712 for DWARF debugging information, not stabs. And, they do not
17713 currently work for programs using Ada.
17715 @node Symbol Errors
17716 @section Errors Reading Symbol Files
17718 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17719 such as symbol types it does not recognize, or known bugs in compiler
17720 output. By default, @value{GDBN} does not notify you of such problems, since
17721 they are relatively common and primarily of interest to people
17722 debugging compilers. If you are interested in seeing information
17723 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17724 only one message about each such type of problem, no matter how many
17725 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17726 to see how many times the problems occur, with the @code{set
17727 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17730 The messages currently printed, and their meanings, include:
17733 @item inner block not inside outer block in @var{symbol}
17735 The symbol information shows where symbol scopes begin and end
17736 (such as at the start of a function or a block of statements). This
17737 error indicates that an inner scope block is not fully contained
17738 in its outer scope blocks.
17740 @value{GDBN} circumvents the problem by treating the inner block as if it had
17741 the same scope as the outer block. In the error message, @var{symbol}
17742 may be shown as ``@code{(don't know)}'' if the outer block is not a
17745 @item block at @var{address} out of order
17747 The symbol information for symbol scope blocks should occur in
17748 order of increasing addresses. This error indicates that it does not
17751 @value{GDBN} does not circumvent this problem, and has trouble
17752 locating symbols in the source file whose symbols it is reading. (You
17753 can often determine what source file is affected by specifying
17754 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17757 @item bad block start address patched
17759 The symbol information for a symbol scope block has a start address
17760 smaller than the address of the preceding source line. This is known
17761 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17763 @value{GDBN} circumvents the problem by treating the symbol scope block as
17764 starting on the previous source line.
17766 @item bad string table offset in symbol @var{n}
17769 Symbol number @var{n} contains a pointer into the string table which is
17770 larger than the size of the string table.
17772 @value{GDBN} circumvents the problem by considering the symbol to have the
17773 name @code{foo}, which may cause other problems if many symbols end up
17776 @item unknown symbol type @code{0x@var{nn}}
17778 The symbol information contains new data types that @value{GDBN} does
17779 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17780 uncomprehended information, in hexadecimal.
17782 @value{GDBN} circumvents the error by ignoring this symbol information.
17783 This usually allows you to debug your program, though certain symbols
17784 are not accessible. If you encounter such a problem and feel like
17785 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17786 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17787 and examine @code{*bufp} to see the symbol.
17789 @item stub type has NULL name
17791 @value{GDBN} could not find the full definition for a struct or class.
17793 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17794 The symbol information for a C@t{++} member function is missing some
17795 information that recent versions of the compiler should have output for
17798 @item info mismatch between compiler and debugger
17800 @value{GDBN} could not parse a type specification output by the compiler.
17805 @section GDB Data Files
17807 @cindex prefix for data files
17808 @value{GDBN} will sometimes read an auxiliary data file. These files
17809 are kept in a directory known as the @dfn{data directory}.
17811 You can set the data directory's name, and view the name @value{GDBN}
17812 is currently using.
17815 @kindex set data-directory
17816 @item set data-directory @var{directory}
17817 Set the directory which @value{GDBN} searches for auxiliary data files
17818 to @var{directory}.
17820 @kindex show data-directory
17821 @item show data-directory
17822 Show the directory @value{GDBN} searches for auxiliary data files.
17825 @cindex default data directory
17826 @cindex @samp{--with-gdb-datadir}
17827 You can set the default data directory by using the configure-time
17828 @samp{--with-gdb-datadir} option. If the data directory is inside
17829 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17830 @samp{--exec-prefix}), then the default data directory will be updated
17831 automatically if the installed @value{GDBN} is moved to a new
17834 The data directory may also be specified with the
17835 @code{--data-directory} command line option.
17836 @xref{Mode Options}.
17839 @chapter Specifying a Debugging Target
17841 @cindex debugging target
17842 A @dfn{target} is the execution environment occupied by your program.
17844 Often, @value{GDBN} runs in the same host environment as your program;
17845 in that case, the debugging target is specified as a side effect when
17846 you use the @code{file} or @code{core} commands. When you need more
17847 flexibility---for example, running @value{GDBN} on a physically separate
17848 host, or controlling a standalone system over a serial port or a
17849 realtime system over a TCP/IP connection---you can use the @code{target}
17850 command to specify one of the target types configured for @value{GDBN}
17851 (@pxref{Target Commands, ,Commands for Managing Targets}).
17853 @cindex target architecture
17854 It is possible to build @value{GDBN} for several different @dfn{target
17855 architectures}. When @value{GDBN} is built like that, you can choose
17856 one of the available architectures with the @kbd{set architecture}
17860 @kindex set architecture
17861 @kindex show architecture
17862 @item set architecture @var{arch}
17863 This command sets the current target architecture to @var{arch}. The
17864 value of @var{arch} can be @code{"auto"}, in addition to one of the
17865 supported architectures.
17867 @item show architecture
17868 Show the current target architecture.
17870 @item set processor
17872 @kindex set processor
17873 @kindex show processor
17874 These are alias commands for, respectively, @code{set architecture}
17875 and @code{show architecture}.
17879 * Active Targets:: Active targets
17880 * Target Commands:: Commands for managing targets
17881 * Byte Order:: Choosing target byte order
17884 @node Active Targets
17885 @section Active Targets
17887 @cindex stacking targets
17888 @cindex active targets
17889 @cindex multiple targets
17891 There are multiple classes of targets such as: processes, executable files or
17892 recording sessions. Core files belong to the process class, making core file
17893 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17894 on multiple active targets, one in each class. This allows you to (for
17895 example) start a process and inspect its activity, while still having access to
17896 the executable file after the process finishes. Or if you start process
17897 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17898 presented a virtual layer of the recording target, while the process target
17899 remains stopped at the chronologically last point of the process execution.
17901 Use the @code{core-file} and @code{exec-file} commands to select a new core
17902 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17903 specify as a target a process that is already running, use the @code{attach}
17904 command (@pxref{Attach, ,Debugging an Already-running Process}).
17906 @node Target Commands
17907 @section Commands for Managing Targets
17910 @item target @var{type} @var{parameters}
17911 Connects the @value{GDBN} host environment to a target machine or
17912 process. A target is typically a protocol for talking to debugging
17913 facilities. You use the argument @var{type} to specify the type or
17914 protocol of the target machine.
17916 Further @var{parameters} are interpreted by the target protocol, but
17917 typically include things like device names or host names to connect
17918 with, process numbers, and baud rates.
17920 The @code{target} command does not repeat if you press @key{RET} again
17921 after executing the command.
17923 @kindex help target
17925 Displays the names of all targets available. To display targets
17926 currently selected, use either @code{info target} or @code{info files}
17927 (@pxref{Files, ,Commands to Specify Files}).
17929 @item help target @var{name}
17930 Describe a particular target, including any parameters necessary to
17933 @kindex set gnutarget
17934 @item set gnutarget @var{args}
17935 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17936 knows whether it is reading an @dfn{executable},
17937 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17938 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17939 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17942 @emph{Warning:} To specify a file format with @code{set gnutarget},
17943 you must know the actual BFD name.
17947 @xref{Files, , Commands to Specify Files}.
17949 @kindex show gnutarget
17950 @item show gnutarget
17951 Use the @code{show gnutarget} command to display what file format
17952 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17953 @value{GDBN} will determine the file format for each file automatically,
17954 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17957 @cindex common targets
17958 Here are some common targets (available, or not, depending on the GDB
17963 @item target exec @var{program}
17964 @cindex executable file target
17965 An executable file. @samp{target exec @var{program}} is the same as
17966 @samp{exec-file @var{program}}.
17968 @item target core @var{filename}
17969 @cindex core dump file target
17970 A core dump file. @samp{target core @var{filename}} is the same as
17971 @samp{core-file @var{filename}}.
17973 @item target remote @var{medium}
17974 @cindex remote target
17975 A remote system connected to @value{GDBN} via a serial line or network
17976 connection. This command tells @value{GDBN} to use its own remote
17977 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17979 For example, if you have a board connected to @file{/dev/ttya} on the
17980 machine running @value{GDBN}, you could say:
17983 target remote /dev/ttya
17986 @code{target remote} supports the @code{load} command. This is only
17987 useful if you have some other way of getting the stub to the target
17988 system, and you can put it somewhere in memory where it won't get
17989 clobbered by the download.
17991 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17992 @cindex built-in simulator target
17993 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18001 works; however, you cannot assume that a specific memory map, device
18002 drivers, or even basic I/O is available, although some simulators do
18003 provide these. For info about any processor-specific simulator details,
18004 see the appropriate section in @ref{Embedded Processors, ,Embedded
18009 Different targets are available on different configurations of @value{GDBN};
18010 your configuration may have more or fewer targets.
18012 Many remote targets require you to download the executable's code once
18013 you've successfully established a connection. You may wish to control
18014 various aspects of this process.
18019 @kindex set hash@r{, for remote monitors}
18020 @cindex hash mark while downloading
18021 This command controls whether a hash mark @samp{#} is displayed while
18022 downloading a file to the remote monitor. If on, a hash mark is
18023 displayed after each S-record is successfully downloaded to the
18027 @kindex show hash@r{, for remote monitors}
18028 Show the current status of displaying the hash mark.
18030 @item set debug monitor
18031 @kindex set debug monitor
18032 @cindex display remote monitor communications
18033 Enable or disable display of communications messages between
18034 @value{GDBN} and the remote monitor.
18036 @item show debug monitor
18037 @kindex show debug monitor
18038 Show the current status of displaying communications between
18039 @value{GDBN} and the remote monitor.
18044 @kindex load @var{filename}
18045 @item load @var{filename}
18047 Depending on what remote debugging facilities are configured into
18048 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18049 is meant to make @var{filename} (an executable) available for debugging
18050 on the remote system---by downloading, or dynamic linking, for example.
18051 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18052 the @code{add-symbol-file} command.
18054 If your @value{GDBN} does not have a @code{load} command, attempting to
18055 execute it gets the error message ``@code{You can't do that when your
18056 target is @dots{}}''
18058 The file is loaded at whatever address is specified in the executable.
18059 For some object file formats, you can specify the load address when you
18060 link the program; for other formats, like a.out, the object file format
18061 specifies a fixed address.
18062 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18064 Depending on the remote side capabilities, @value{GDBN} may be able to
18065 load programs into flash memory.
18067 @code{load} does not repeat if you press @key{RET} again after using it.
18071 @section Choosing Target Byte Order
18073 @cindex choosing target byte order
18074 @cindex target byte order
18076 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18077 offer the ability to run either big-endian or little-endian byte
18078 orders. Usually the executable or symbol will include a bit to
18079 designate the endian-ness, and you will not need to worry about
18080 which to use. However, you may still find it useful to adjust
18081 @value{GDBN}'s idea of processor endian-ness manually.
18085 @item set endian big
18086 Instruct @value{GDBN} to assume the target is big-endian.
18088 @item set endian little
18089 Instruct @value{GDBN} to assume the target is little-endian.
18091 @item set endian auto
18092 Instruct @value{GDBN} to use the byte order associated with the
18096 Display @value{GDBN}'s current idea of the target byte order.
18100 Note that these commands merely adjust interpretation of symbolic
18101 data on the host, and that they have absolutely no effect on the
18105 @node Remote Debugging
18106 @chapter Debugging Remote Programs
18107 @cindex remote debugging
18109 If you are trying to debug a program running on a machine that cannot run
18110 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18111 For example, you might use remote debugging on an operating system kernel,
18112 or on a small system which does not have a general purpose operating system
18113 powerful enough to run a full-featured debugger.
18115 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18116 to make this work with particular debugging targets. In addition,
18117 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18118 but not specific to any particular target system) which you can use if you
18119 write the remote stubs---the code that runs on the remote system to
18120 communicate with @value{GDBN}.
18122 Other remote targets may be available in your
18123 configuration of @value{GDBN}; use @code{help target} to list them.
18126 * Connecting:: Connecting to a remote target
18127 * File Transfer:: Sending files to a remote system
18128 * Server:: Using the gdbserver program
18129 * Remote Configuration:: Remote configuration
18130 * Remote Stub:: Implementing a remote stub
18134 @section Connecting to a Remote Target
18136 On the @value{GDBN} host machine, you will need an unstripped copy of
18137 your program, since @value{GDBN} needs symbol and debugging information.
18138 Start up @value{GDBN} as usual, using the name of the local copy of your
18139 program as the first argument.
18141 @cindex @code{target remote}
18142 @value{GDBN} can communicate with the target over a serial line, or
18143 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18144 each case, @value{GDBN} uses the same protocol for debugging your
18145 program; only the medium carrying the debugging packets varies. The
18146 @code{target remote} command establishes a connection to the target.
18147 Its arguments indicate which medium to use:
18151 @item target remote @var{serial-device}
18152 @cindex serial line, @code{target remote}
18153 Use @var{serial-device} to communicate with the target. For example,
18154 to use a serial line connected to the device named @file{/dev/ttyb}:
18157 target remote /dev/ttyb
18160 If you're using a serial line, you may want to give @value{GDBN} the
18161 @samp{--baud} option, or use the @code{set serial baud} command
18162 (@pxref{Remote Configuration, set serial baud}) before the
18163 @code{target} command.
18165 @item target remote @code{@var{host}:@var{port}}
18166 @itemx target remote @code{tcp:@var{host}:@var{port}}
18167 @cindex @acronym{TCP} port, @code{target remote}
18168 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18169 The @var{host} may be either a host name or a numeric @acronym{IP}
18170 address; @var{port} must be a decimal number. The @var{host} could be
18171 the target machine itself, if it is directly connected to the net, or
18172 it might be a terminal server which in turn has a serial line to the
18175 For example, to connect to port 2828 on a terminal server named
18179 target remote manyfarms:2828
18182 If your remote target is actually running on the same machine as your
18183 debugger session (e.g.@: a simulator for your target running on the
18184 same host), you can omit the hostname. For example, to connect to
18185 port 1234 on your local machine:
18188 target remote :1234
18192 Note that the colon is still required here.
18194 @item target remote @code{udp:@var{host}:@var{port}}
18195 @cindex @acronym{UDP} port, @code{target remote}
18196 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18197 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18200 target remote udp:manyfarms:2828
18203 When using a @acronym{UDP} connection for remote debugging, you should
18204 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18205 can silently drop packets on busy or unreliable networks, which will
18206 cause havoc with your debugging session.
18208 @item target remote | @var{command}
18209 @cindex pipe, @code{target remote} to
18210 Run @var{command} in the background and communicate with it using a
18211 pipe. The @var{command} is a shell command, to be parsed and expanded
18212 by the system's command shell, @code{/bin/sh}; it should expect remote
18213 protocol packets on its standard input, and send replies on its
18214 standard output. You could use this to run a stand-alone simulator
18215 that speaks the remote debugging protocol, to make net connections
18216 using programs like @code{ssh}, or for other similar tricks.
18218 If @var{command} closes its standard output (perhaps by exiting),
18219 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18220 program has already exited, this will have no effect.)
18224 Once the connection has been established, you can use all the usual
18225 commands to examine and change data. The remote program is already
18226 running; you can use @kbd{step} and @kbd{continue}, and you do not
18227 need to use @kbd{run}.
18229 @cindex interrupting remote programs
18230 @cindex remote programs, interrupting
18231 Whenever @value{GDBN} is waiting for the remote program, if you type the
18232 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18233 program. This may or may not succeed, depending in part on the hardware
18234 and the serial drivers the remote system uses. If you type the
18235 interrupt character once again, @value{GDBN} displays this prompt:
18238 Interrupted while waiting for the program.
18239 Give up (and stop debugging it)? (y or n)
18242 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18243 (If you decide you want to try again later, you can use @samp{target
18244 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18245 goes back to waiting.
18248 @kindex detach (remote)
18250 When you have finished debugging the remote program, you can use the
18251 @code{detach} command to release it from @value{GDBN} control.
18252 Detaching from the target normally resumes its execution, but the results
18253 will depend on your particular remote stub. After the @code{detach}
18254 command, @value{GDBN} is free to connect to another target.
18258 The @code{disconnect} command behaves like @code{detach}, except that
18259 the target is generally not resumed. It will wait for @value{GDBN}
18260 (this instance or another one) to connect and continue debugging. After
18261 the @code{disconnect} command, @value{GDBN} is again free to connect to
18264 @cindex send command to remote monitor
18265 @cindex extend @value{GDBN} for remote targets
18266 @cindex add new commands for external monitor
18268 @item monitor @var{cmd}
18269 This command allows you to send arbitrary commands directly to the
18270 remote monitor. Since @value{GDBN} doesn't care about the commands it
18271 sends like this, this command is the way to extend @value{GDBN}---you
18272 can add new commands that only the external monitor will understand
18276 @node File Transfer
18277 @section Sending files to a remote system
18278 @cindex remote target, file transfer
18279 @cindex file transfer
18280 @cindex sending files to remote systems
18282 Some remote targets offer the ability to transfer files over the same
18283 connection used to communicate with @value{GDBN}. This is convenient
18284 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18285 running @code{gdbserver} over a network interface. For other targets,
18286 e.g.@: embedded devices with only a single serial port, this may be
18287 the only way to upload or download files.
18289 Not all remote targets support these commands.
18293 @item remote put @var{hostfile} @var{targetfile}
18294 Copy file @var{hostfile} from the host system (the machine running
18295 @value{GDBN}) to @var{targetfile} on the target system.
18298 @item remote get @var{targetfile} @var{hostfile}
18299 Copy file @var{targetfile} from the target system to @var{hostfile}
18300 on the host system.
18302 @kindex remote delete
18303 @item remote delete @var{targetfile}
18304 Delete @var{targetfile} from the target system.
18309 @section Using the @code{gdbserver} Program
18312 @cindex remote connection without stubs
18313 @code{gdbserver} is a control program for Unix-like systems, which
18314 allows you to connect your program with a remote @value{GDBN} via
18315 @code{target remote}---but without linking in the usual debugging stub.
18317 @code{gdbserver} is not a complete replacement for the debugging stubs,
18318 because it requires essentially the same operating-system facilities
18319 that @value{GDBN} itself does. In fact, a system that can run
18320 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18321 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18322 because it is a much smaller program than @value{GDBN} itself. It is
18323 also easier to port than all of @value{GDBN}, so you may be able to get
18324 started more quickly on a new system by using @code{gdbserver}.
18325 Finally, if you develop code for real-time systems, you may find that
18326 the tradeoffs involved in real-time operation make it more convenient to
18327 do as much development work as possible on another system, for example
18328 by cross-compiling. You can use @code{gdbserver} to make a similar
18329 choice for debugging.
18331 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18332 or a TCP connection, using the standard @value{GDBN} remote serial
18336 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18337 Do not run @code{gdbserver} connected to any public network; a
18338 @value{GDBN} connection to @code{gdbserver} provides access to the
18339 target system with the same privileges as the user running
18343 @subsection Running @code{gdbserver}
18344 @cindex arguments, to @code{gdbserver}
18345 @cindex @code{gdbserver}, command-line arguments
18347 Run @code{gdbserver} on the target system. You need a copy of the
18348 program you want to debug, including any libraries it requires.
18349 @code{gdbserver} does not need your program's symbol table, so you can
18350 strip the program if necessary to save space. @value{GDBN} on the host
18351 system does all the symbol handling.
18353 To use the server, you must tell it how to communicate with @value{GDBN};
18354 the name of your program; and the arguments for your program. The usual
18358 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18361 @var{comm} is either a device name (to use a serial line), or a TCP
18362 hostname and portnumber, or @code{-} or @code{stdio} to use
18363 stdin/stdout of @code{gdbserver}.
18364 For example, to debug Emacs with the argument
18365 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18369 target> gdbserver /dev/com1 emacs foo.txt
18372 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18375 To use a TCP connection instead of a serial line:
18378 target> gdbserver host:2345 emacs foo.txt
18381 The only difference from the previous example is the first argument,
18382 specifying that you are communicating with the host @value{GDBN} via
18383 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18384 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18385 (Currently, the @samp{host} part is ignored.) You can choose any number
18386 you want for the port number as long as it does not conflict with any
18387 TCP ports already in use on the target system (for example, @code{23} is
18388 reserved for @code{telnet}).@footnote{If you choose a port number that
18389 conflicts with another service, @code{gdbserver} prints an error message
18390 and exits.} You must use the same port number with the host @value{GDBN}
18391 @code{target remote} command.
18393 The @code{stdio} connection is useful when starting @code{gdbserver}
18397 (gdb) target remote | ssh -T hostname gdbserver - hello
18400 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18401 and we don't want escape-character handling. Ssh does this by default when
18402 a command is provided, the flag is provided to make it explicit.
18403 You could elide it if you want to.
18405 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18406 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18407 display through a pipe connected to gdbserver.
18408 Both @code{stdout} and @code{stderr} use the same pipe.
18410 @subsubsection Attaching to a Running Program
18411 @cindex attach to a program, @code{gdbserver}
18412 @cindex @option{--attach}, @code{gdbserver} option
18414 On some targets, @code{gdbserver} can also attach to running programs.
18415 This is accomplished via the @code{--attach} argument. The syntax is:
18418 target> gdbserver --attach @var{comm} @var{pid}
18421 @var{pid} is the process ID of a currently running process. It isn't necessary
18422 to point @code{gdbserver} at a binary for the running process.
18425 You can debug processes by name instead of process ID if your target has the
18426 @code{pidof} utility:
18429 target> gdbserver --attach @var{comm} `pidof @var{program}`
18432 In case more than one copy of @var{program} is running, or @var{program}
18433 has multiple threads, most versions of @code{pidof} support the
18434 @code{-s} option to only return the first process ID.
18436 @subsubsection Multi-Process Mode for @code{gdbserver}
18437 @cindex @code{gdbserver}, multiple processes
18438 @cindex multiple processes with @code{gdbserver}
18440 When you connect to @code{gdbserver} using @code{target remote},
18441 @code{gdbserver} debugs the specified program only once. When the
18442 program exits, or you detach from it, @value{GDBN} closes the connection
18443 and @code{gdbserver} exits.
18445 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18446 enters multi-process mode. When the debugged program exits, or you
18447 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18448 though no program is running. The @code{run} and @code{attach}
18449 commands instruct @code{gdbserver} to run or attach to a new program.
18450 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18451 remote exec-file}) to select the program to run. Command line
18452 arguments are supported, except for wildcard expansion and I/O
18453 redirection (@pxref{Arguments}).
18455 @cindex @option{--multi}, @code{gdbserver} option
18456 To start @code{gdbserver} without supplying an initial command to run
18457 or process ID to attach, use the @option{--multi} command line option.
18458 Then you can connect using @kbd{target extended-remote} and start
18459 the program you want to debug.
18461 In multi-process mode @code{gdbserver} does not automatically exit unless you
18462 use the option @option{--once}. You can terminate it by using
18463 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18464 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18465 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18466 @option{--multi} option to @code{gdbserver} has no influence on that.
18468 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18470 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18472 @code{gdbserver} normally terminates after all of its debugged processes have
18473 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18474 extended-remote}, @code{gdbserver} stays running even with no processes left.
18475 @value{GDBN} normally terminates the spawned debugged process on its exit,
18476 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18477 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18478 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18479 stays running even in the @kbd{target remote} mode.
18481 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18482 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18483 completeness, at most one @value{GDBN} can be connected at a time.
18485 @cindex @option{--once}, @code{gdbserver} option
18486 By default, @code{gdbserver} keeps the listening TCP port open, so that
18487 subsequent connections are possible. However, if you start @code{gdbserver}
18488 with the @option{--once} option, it will stop listening for any further
18489 connection attempts after connecting to the first @value{GDBN} session. This
18490 means no further connections to @code{gdbserver} will be possible after the
18491 first one. It also means @code{gdbserver} will terminate after the first
18492 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18493 connections and even in the @kbd{target extended-remote} mode. The
18494 @option{--once} option allows reusing the same port number for connecting to
18495 multiple instances of @code{gdbserver} running on the same host, since each
18496 instance closes its port after the first connection.
18498 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18500 @cindex @option{--debug}, @code{gdbserver} option
18501 The @option{--debug} option tells @code{gdbserver} to display extra
18502 status information about the debugging process.
18503 @cindex @option{--remote-debug}, @code{gdbserver} option
18504 The @option{--remote-debug} option tells @code{gdbserver} to display
18505 remote protocol debug output. These options are intended for
18506 @code{gdbserver} development and for bug reports to the developers.
18508 @cindex @option{--wrapper}, @code{gdbserver} option
18509 The @option{--wrapper} option specifies a wrapper to launch programs
18510 for debugging. The option should be followed by the name of the
18511 wrapper, then any command-line arguments to pass to the wrapper, then
18512 @kbd{--} indicating the end of the wrapper arguments.
18514 @code{gdbserver} runs the specified wrapper program with a combined
18515 command line including the wrapper arguments, then the name of the
18516 program to debug, then any arguments to the program. The wrapper
18517 runs until it executes your program, and then @value{GDBN} gains control.
18519 You can use any program that eventually calls @code{execve} with
18520 its arguments as a wrapper. Several standard Unix utilities do
18521 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18522 with @code{exec "$@@"} will also work.
18524 For example, you can use @code{env} to pass an environment variable to
18525 the debugged program, without setting the variable in @code{gdbserver}'s
18529 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18532 @subsection Connecting to @code{gdbserver}
18534 Run @value{GDBN} on the host system.
18536 First make sure you have the necessary symbol files. Load symbols for
18537 your application using the @code{file} command before you connect. Use
18538 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18539 was compiled with the correct sysroot using @code{--with-sysroot}).
18541 The symbol file and target libraries must exactly match the executable
18542 and libraries on the target, with one exception: the files on the host
18543 system should not be stripped, even if the files on the target system
18544 are. Mismatched or missing files will lead to confusing results
18545 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18546 files may also prevent @code{gdbserver} from debugging multi-threaded
18549 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18550 For TCP connections, you must start up @code{gdbserver} prior to using
18551 the @code{target remote} command. Otherwise you may get an error whose
18552 text depends on the host system, but which usually looks something like
18553 @samp{Connection refused}. Don't use the @code{load}
18554 command in @value{GDBN} when using @code{gdbserver}, since the program is
18555 already on the target.
18557 @subsection Monitor Commands for @code{gdbserver}
18558 @cindex monitor commands, for @code{gdbserver}
18559 @anchor{Monitor Commands for gdbserver}
18561 During a @value{GDBN} session using @code{gdbserver}, you can use the
18562 @code{monitor} command to send special requests to @code{gdbserver}.
18563 Here are the available commands.
18567 List the available monitor commands.
18569 @item monitor set debug 0
18570 @itemx monitor set debug 1
18571 Disable or enable general debugging messages.
18573 @item monitor set remote-debug 0
18574 @itemx monitor set remote-debug 1
18575 Disable or enable specific debugging messages associated with the remote
18576 protocol (@pxref{Remote Protocol}).
18578 @item monitor set libthread-db-search-path [PATH]
18579 @cindex gdbserver, search path for @code{libthread_db}
18580 When this command is issued, @var{path} is a colon-separated list of
18581 directories to search for @code{libthread_db} (@pxref{Threads,,set
18582 libthread-db-search-path}). If you omit @var{path},
18583 @samp{libthread-db-search-path} will be reset to its default value.
18585 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18586 not supported in @code{gdbserver}.
18589 Tell gdbserver to exit immediately. This command should be followed by
18590 @code{disconnect} to close the debugging session. @code{gdbserver} will
18591 detach from any attached processes and kill any processes it created.
18592 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18593 of a multi-process mode debug session.
18597 @subsection Tracepoints support in @code{gdbserver}
18598 @cindex tracepoints support in @code{gdbserver}
18600 On some targets, @code{gdbserver} supports tracepoints, fast
18601 tracepoints and static tracepoints.
18603 For fast or static tracepoints to work, a special library called the
18604 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18605 This library is built and distributed as an integral part of
18606 @code{gdbserver}. In addition, support for static tracepoints
18607 requires building the in-process agent library with static tracepoints
18608 support. At present, the UST (LTTng Userspace Tracer,
18609 @url{http://lttng.org/ust}) tracing engine is supported. This support
18610 is automatically available if UST development headers are found in the
18611 standard include path when @code{gdbserver} is built, or if
18612 @code{gdbserver} was explicitly configured using @option{--with-ust}
18613 to point at such headers. You can explicitly disable the support
18614 using @option{--with-ust=no}.
18616 There are several ways to load the in-process agent in your program:
18619 @item Specifying it as dependency at link time
18621 You can link your program dynamically with the in-process agent
18622 library. On most systems, this is accomplished by adding
18623 @code{-linproctrace} to the link command.
18625 @item Using the system's preloading mechanisms
18627 You can force loading the in-process agent at startup time by using
18628 your system's support for preloading shared libraries. Many Unixes
18629 support the concept of preloading user defined libraries. In most
18630 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18631 in the environment. See also the description of @code{gdbserver}'s
18632 @option{--wrapper} command line option.
18634 @item Using @value{GDBN} to force loading the agent at run time
18636 On some systems, you can force the inferior to load a shared library,
18637 by calling a dynamic loader function in the inferior that takes care
18638 of dynamically looking up and loading a shared library. On most Unix
18639 systems, the function is @code{dlopen}. You'll use the @code{call}
18640 command for that. For example:
18643 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18646 Note that on most Unix systems, for the @code{dlopen} function to be
18647 available, the program needs to be linked with @code{-ldl}.
18650 On systems that have a userspace dynamic loader, like most Unix
18651 systems, when you connect to @code{gdbserver} using @code{target
18652 remote}, you'll find that the program is stopped at the dynamic
18653 loader's entry point, and no shared library has been loaded in the
18654 program's address space yet, including the in-process agent. In that
18655 case, before being able to use any of the fast or static tracepoints
18656 features, you need to let the loader run and load the shared
18657 libraries. The simplest way to do that is to run the program to the
18658 main procedure. E.g., if debugging a C or C@t{++} program, start
18659 @code{gdbserver} like so:
18662 $ gdbserver :9999 myprogram
18665 Start GDB and connect to @code{gdbserver} like so, and run to main:
18669 (@value{GDBP}) target remote myhost:9999
18670 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18671 (@value{GDBP}) b main
18672 (@value{GDBP}) continue
18675 The in-process tracing agent library should now be loaded into the
18676 process; you can confirm it with the @code{info sharedlibrary}
18677 command, which will list @file{libinproctrace.so} as loaded in the
18678 process. You are now ready to install fast tracepoints, list static
18679 tracepoint markers, probe static tracepoints markers, and start
18682 @node Remote Configuration
18683 @section Remote Configuration
18686 @kindex show remote
18687 This section documents the configuration options available when
18688 debugging remote programs. For the options related to the File I/O
18689 extensions of the remote protocol, see @ref{system,
18690 system-call-allowed}.
18693 @item set remoteaddresssize @var{bits}
18694 @cindex address size for remote targets
18695 @cindex bits in remote address
18696 Set the maximum size of address in a memory packet to the specified
18697 number of bits. @value{GDBN} will mask off the address bits above
18698 that number, when it passes addresses to the remote target. The
18699 default value is the number of bits in the target's address.
18701 @item show remoteaddresssize
18702 Show the current value of remote address size in bits.
18704 @item set serial baud @var{n}
18705 @cindex baud rate for remote targets
18706 Set the baud rate for the remote serial I/O to @var{n} baud. The
18707 value is used to set the speed of the serial port used for debugging
18710 @item show serial baud
18711 Show the current speed of the remote connection.
18713 @item set remotebreak
18714 @cindex interrupt remote programs
18715 @cindex BREAK signal instead of Ctrl-C
18716 @anchor{set remotebreak}
18717 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18718 when you type @kbd{Ctrl-c} to interrupt the program running
18719 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18720 character instead. The default is off, since most remote systems
18721 expect to see @samp{Ctrl-C} as the interrupt signal.
18723 @item show remotebreak
18724 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18725 interrupt the remote program.
18727 @item set remoteflow on
18728 @itemx set remoteflow off
18729 @kindex set remoteflow
18730 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18731 on the serial port used to communicate to the remote target.
18733 @item show remoteflow
18734 @kindex show remoteflow
18735 Show the current setting of hardware flow control.
18737 @item set remotelogbase @var{base}
18738 Set the base (a.k.a.@: radix) of logging serial protocol
18739 communications to @var{base}. Supported values of @var{base} are:
18740 @code{ascii}, @code{octal}, and @code{hex}. The default is
18743 @item show remotelogbase
18744 Show the current setting of the radix for logging remote serial
18747 @item set remotelogfile @var{file}
18748 @cindex record serial communications on file
18749 Record remote serial communications on the named @var{file}. The
18750 default is not to record at all.
18752 @item show remotelogfile.
18753 Show the current setting of the file name on which to record the
18754 serial communications.
18756 @item set remotetimeout @var{num}
18757 @cindex timeout for serial communications
18758 @cindex remote timeout
18759 Set the timeout limit to wait for the remote target to respond to
18760 @var{num} seconds. The default is 2 seconds.
18762 @item show remotetimeout
18763 Show the current number of seconds to wait for the remote target
18766 @cindex limit hardware breakpoints and watchpoints
18767 @cindex remote target, limit break- and watchpoints
18768 @anchor{set remote hardware-watchpoint-limit}
18769 @anchor{set remote hardware-breakpoint-limit}
18770 @item set remote hardware-watchpoint-limit @var{limit}
18771 @itemx set remote hardware-breakpoint-limit @var{limit}
18772 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18773 watchpoints. A limit of -1, the default, is treated as unlimited.
18775 @cindex limit hardware watchpoints length
18776 @cindex remote target, limit watchpoints length
18777 @anchor{set remote hardware-watchpoint-length-limit}
18778 @item set remote hardware-watchpoint-length-limit @var{limit}
18779 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18780 a remote hardware watchpoint. A limit of -1, the default, is treated
18783 @item show remote hardware-watchpoint-length-limit
18784 Show the current limit (in bytes) of the maximum length of
18785 a remote hardware watchpoint.
18787 @item set remote exec-file @var{filename}
18788 @itemx show remote exec-file
18789 @anchor{set remote exec-file}
18790 @cindex executable file, for remote target
18791 Select the file used for @code{run} with @code{target
18792 extended-remote}. This should be set to a filename valid on the
18793 target system. If it is not set, the target will use a default
18794 filename (e.g.@: the last program run).
18796 @item set remote interrupt-sequence
18797 @cindex interrupt remote programs
18798 @cindex select Ctrl-C, BREAK or BREAK-g
18799 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18800 @samp{BREAK-g} as the
18801 sequence to the remote target in order to interrupt the execution.
18802 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18803 is high level of serial line for some certain time.
18804 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18805 It is @code{BREAK} signal followed by character @code{g}.
18807 @item show interrupt-sequence
18808 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18809 is sent by @value{GDBN} to interrupt the remote program.
18810 @code{BREAK-g} is BREAK signal followed by @code{g} and
18811 also known as Magic SysRq g.
18813 @item set remote interrupt-on-connect
18814 @cindex send interrupt-sequence on start
18815 Specify whether interrupt-sequence is sent to remote target when
18816 @value{GDBN} connects to it. This is mostly needed when you debug
18817 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18818 which is known as Magic SysRq g in order to connect @value{GDBN}.
18820 @item show interrupt-on-connect
18821 Show whether interrupt-sequence is sent
18822 to remote target when @value{GDBN} connects to it.
18826 @item set tcp auto-retry on
18827 @cindex auto-retry, for remote TCP target
18828 Enable auto-retry for remote TCP connections. This is useful if the remote
18829 debugging agent is launched in parallel with @value{GDBN}; there is a race
18830 condition because the agent may not become ready to accept the connection
18831 before @value{GDBN} attempts to connect. When auto-retry is
18832 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18833 to establish the connection using the timeout specified by
18834 @code{set tcp connect-timeout}.
18836 @item set tcp auto-retry off
18837 Do not auto-retry failed TCP connections.
18839 @item show tcp auto-retry
18840 Show the current auto-retry setting.
18842 @item set tcp connect-timeout @var{seconds}
18843 @itemx set tcp connect-timeout unlimited
18844 @cindex connection timeout, for remote TCP target
18845 @cindex timeout, for remote target connection
18846 Set the timeout for establishing a TCP connection to the remote target to
18847 @var{seconds}. The timeout affects both polling to retry failed connections
18848 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18849 that are merely slow to complete, and represents an approximate cumulative
18850 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18851 @value{GDBN} will keep attempting to establish a connection forever,
18852 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18854 @item show tcp connect-timeout
18855 Show the current connection timeout setting.
18858 @cindex remote packets, enabling and disabling
18859 The @value{GDBN} remote protocol autodetects the packets supported by
18860 your debugging stub. If you need to override the autodetection, you
18861 can use these commands to enable or disable individual packets. Each
18862 packet can be set to @samp{on} (the remote target supports this
18863 packet), @samp{off} (the remote target does not support this packet),
18864 or @samp{auto} (detect remote target support for this packet). They
18865 all default to @samp{auto}. For more information about each packet,
18866 see @ref{Remote Protocol}.
18868 During normal use, you should not have to use any of these commands.
18869 If you do, that may be a bug in your remote debugging stub, or a bug
18870 in @value{GDBN}. You may want to report the problem to the
18871 @value{GDBN} developers.
18873 For each packet @var{name}, the command to enable or disable the
18874 packet is @code{set remote @var{name}-packet}. The available settings
18877 @multitable @columnfractions 0.28 0.32 0.25
18880 @tab Related Features
18882 @item @code{fetch-register}
18884 @tab @code{info registers}
18886 @item @code{set-register}
18890 @item @code{binary-download}
18892 @tab @code{load}, @code{set}
18894 @item @code{read-aux-vector}
18895 @tab @code{qXfer:auxv:read}
18896 @tab @code{info auxv}
18898 @item @code{symbol-lookup}
18899 @tab @code{qSymbol}
18900 @tab Detecting multiple threads
18902 @item @code{attach}
18903 @tab @code{vAttach}
18906 @item @code{verbose-resume}
18908 @tab Stepping or resuming multiple threads
18914 @item @code{software-breakpoint}
18918 @item @code{hardware-breakpoint}
18922 @item @code{write-watchpoint}
18926 @item @code{read-watchpoint}
18930 @item @code{access-watchpoint}
18934 @item @code{target-features}
18935 @tab @code{qXfer:features:read}
18936 @tab @code{set architecture}
18938 @item @code{library-info}
18939 @tab @code{qXfer:libraries:read}
18940 @tab @code{info sharedlibrary}
18942 @item @code{memory-map}
18943 @tab @code{qXfer:memory-map:read}
18944 @tab @code{info mem}
18946 @item @code{read-sdata-object}
18947 @tab @code{qXfer:sdata:read}
18948 @tab @code{print $_sdata}
18950 @item @code{read-spu-object}
18951 @tab @code{qXfer:spu:read}
18952 @tab @code{info spu}
18954 @item @code{write-spu-object}
18955 @tab @code{qXfer:spu:write}
18956 @tab @code{info spu}
18958 @item @code{read-siginfo-object}
18959 @tab @code{qXfer:siginfo:read}
18960 @tab @code{print $_siginfo}
18962 @item @code{write-siginfo-object}
18963 @tab @code{qXfer:siginfo:write}
18964 @tab @code{set $_siginfo}
18966 @item @code{threads}
18967 @tab @code{qXfer:threads:read}
18968 @tab @code{info threads}
18970 @item @code{get-thread-local-@*storage-address}
18971 @tab @code{qGetTLSAddr}
18972 @tab Displaying @code{__thread} variables
18974 @item @code{get-thread-information-block-address}
18975 @tab @code{qGetTIBAddr}
18976 @tab Display MS-Windows Thread Information Block.
18978 @item @code{search-memory}
18979 @tab @code{qSearch:memory}
18982 @item @code{supported-packets}
18983 @tab @code{qSupported}
18984 @tab Remote communications parameters
18986 @item @code{pass-signals}
18987 @tab @code{QPassSignals}
18988 @tab @code{handle @var{signal}}
18990 @item @code{program-signals}
18991 @tab @code{QProgramSignals}
18992 @tab @code{handle @var{signal}}
18994 @item @code{hostio-close-packet}
18995 @tab @code{vFile:close}
18996 @tab @code{remote get}, @code{remote put}
18998 @item @code{hostio-open-packet}
18999 @tab @code{vFile:open}
19000 @tab @code{remote get}, @code{remote put}
19002 @item @code{hostio-pread-packet}
19003 @tab @code{vFile:pread}
19004 @tab @code{remote get}, @code{remote put}
19006 @item @code{hostio-pwrite-packet}
19007 @tab @code{vFile:pwrite}
19008 @tab @code{remote get}, @code{remote put}
19010 @item @code{hostio-unlink-packet}
19011 @tab @code{vFile:unlink}
19012 @tab @code{remote delete}
19014 @item @code{hostio-readlink-packet}
19015 @tab @code{vFile:readlink}
19018 @item @code{noack-packet}
19019 @tab @code{QStartNoAckMode}
19020 @tab Packet acknowledgment
19022 @item @code{osdata}
19023 @tab @code{qXfer:osdata:read}
19024 @tab @code{info os}
19026 @item @code{query-attached}
19027 @tab @code{qAttached}
19028 @tab Querying remote process attach state.
19030 @item @code{trace-buffer-size}
19031 @tab @code{QTBuffer:size}
19032 @tab @code{set trace-buffer-size}
19034 @item @code{trace-status}
19035 @tab @code{qTStatus}
19036 @tab @code{tstatus}
19038 @item @code{traceframe-info}
19039 @tab @code{qXfer:traceframe-info:read}
19040 @tab Traceframe info
19042 @item @code{install-in-trace}
19043 @tab @code{InstallInTrace}
19044 @tab Install tracepoint in tracing
19046 @item @code{disable-randomization}
19047 @tab @code{QDisableRandomization}
19048 @tab @code{set disable-randomization}
19050 @item @code{conditional-breakpoints-packet}
19051 @tab @code{Z0 and Z1}
19052 @tab @code{Support for target-side breakpoint condition evaluation}
19056 @section Implementing a Remote Stub
19058 @cindex debugging stub, example
19059 @cindex remote stub, example
19060 @cindex stub example, remote debugging
19061 The stub files provided with @value{GDBN} implement the target side of the
19062 communication protocol, and the @value{GDBN} side is implemented in the
19063 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19064 these subroutines to communicate, and ignore the details. (If you're
19065 implementing your own stub file, you can still ignore the details: start
19066 with one of the existing stub files. @file{sparc-stub.c} is the best
19067 organized, and therefore the easiest to read.)
19069 @cindex remote serial debugging, overview
19070 To debug a program running on another machine (the debugging
19071 @dfn{target} machine), you must first arrange for all the usual
19072 prerequisites for the program to run by itself. For example, for a C
19077 A startup routine to set up the C runtime environment; these usually
19078 have a name like @file{crt0}. The startup routine may be supplied by
19079 your hardware supplier, or you may have to write your own.
19082 A C subroutine library to support your program's
19083 subroutine calls, notably managing input and output.
19086 A way of getting your program to the other machine---for example, a
19087 download program. These are often supplied by the hardware
19088 manufacturer, but you may have to write your own from hardware
19092 The next step is to arrange for your program to use a serial port to
19093 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19094 machine). In general terms, the scheme looks like this:
19098 @value{GDBN} already understands how to use this protocol; when everything
19099 else is set up, you can simply use the @samp{target remote} command
19100 (@pxref{Targets,,Specifying a Debugging Target}).
19102 @item On the target,
19103 you must link with your program a few special-purpose subroutines that
19104 implement the @value{GDBN} remote serial protocol. The file containing these
19105 subroutines is called a @dfn{debugging stub}.
19107 On certain remote targets, you can use an auxiliary program
19108 @code{gdbserver} instead of linking a stub into your program.
19109 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19112 The debugging stub is specific to the architecture of the remote
19113 machine; for example, use @file{sparc-stub.c} to debug programs on
19116 @cindex remote serial stub list
19117 These working remote stubs are distributed with @value{GDBN}:
19122 @cindex @file{i386-stub.c}
19125 For Intel 386 and compatible architectures.
19128 @cindex @file{m68k-stub.c}
19129 @cindex Motorola 680x0
19131 For Motorola 680x0 architectures.
19134 @cindex @file{sh-stub.c}
19137 For Renesas SH architectures.
19140 @cindex @file{sparc-stub.c}
19142 For @sc{sparc} architectures.
19144 @item sparcl-stub.c
19145 @cindex @file{sparcl-stub.c}
19148 For Fujitsu @sc{sparclite} architectures.
19152 The @file{README} file in the @value{GDBN} distribution may list other
19153 recently added stubs.
19156 * Stub Contents:: What the stub can do for you
19157 * Bootstrapping:: What you must do for the stub
19158 * Debug Session:: Putting it all together
19161 @node Stub Contents
19162 @subsection What the Stub Can Do for You
19164 @cindex remote serial stub
19165 The debugging stub for your architecture supplies these three
19169 @item set_debug_traps
19170 @findex set_debug_traps
19171 @cindex remote serial stub, initialization
19172 This routine arranges for @code{handle_exception} to run when your
19173 program stops. You must call this subroutine explicitly in your
19174 program's startup code.
19176 @item handle_exception
19177 @findex handle_exception
19178 @cindex remote serial stub, main routine
19179 This is the central workhorse, but your program never calls it
19180 explicitly---the setup code arranges for @code{handle_exception} to
19181 run when a trap is triggered.
19183 @code{handle_exception} takes control when your program stops during
19184 execution (for example, on a breakpoint), and mediates communications
19185 with @value{GDBN} on the host machine. This is where the communications
19186 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19187 representative on the target machine. It begins by sending summary
19188 information on the state of your program, then continues to execute,
19189 retrieving and transmitting any information @value{GDBN} needs, until you
19190 execute a @value{GDBN} command that makes your program resume; at that point,
19191 @code{handle_exception} returns control to your own code on the target
19195 @cindex @code{breakpoint} subroutine, remote
19196 Use this auxiliary subroutine to make your program contain a
19197 breakpoint. Depending on the particular situation, this may be the only
19198 way for @value{GDBN} to get control. For instance, if your target
19199 machine has some sort of interrupt button, you won't need to call this;
19200 pressing the interrupt button transfers control to
19201 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19202 simply receiving characters on the serial port may also trigger a trap;
19203 again, in that situation, you don't need to call @code{breakpoint} from
19204 your own program---simply running @samp{target remote} from the host
19205 @value{GDBN} session gets control.
19207 Call @code{breakpoint} if none of these is true, or if you simply want
19208 to make certain your program stops at a predetermined point for the
19209 start of your debugging session.
19212 @node Bootstrapping
19213 @subsection What You Must Do for the Stub
19215 @cindex remote stub, support routines
19216 The debugging stubs that come with @value{GDBN} are set up for a particular
19217 chip architecture, but they have no information about the rest of your
19218 debugging target machine.
19220 First of all you need to tell the stub how to communicate with the
19224 @item int getDebugChar()
19225 @findex getDebugChar
19226 Write this subroutine to read a single character from the serial port.
19227 It may be identical to @code{getchar} for your target system; a
19228 different name is used to allow you to distinguish the two if you wish.
19230 @item void putDebugChar(int)
19231 @findex putDebugChar
19232 Write this subroutine to write a single character to the serial port.
19233 It may be identical to @code{putchar} for your target system; a
19234 different name is used to allow you to distinguish the two if you wish.
19237 @cindex control C, and remote debugging
19238 @cindex interrupting remote targets
19239 If you want @value{GDBN} to be able to stop your program while it is
19240 running, you need to use an interrupt-driven serial driver, and arrange
19241 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19242 character). That is the character which @value{GDBN} uses to tell the
19243 remote system to stop.
19245 Getting the debugging target to return the proper status to @value{GDBN}
19246 probably requires changes to the standard stub; one quick and dirty way
19247 is to just execute a breakpoint instruction (the ``dirty'' part is that
19248 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19250 Other routines you need to supply are:
19253 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19254 @findex exceptionHandler
19255 Write this function to install @var{exception_address} in the exception
19256 handling tables. You need to do this because the stub does not have any
19257 way of knowing what the exception handling tables on your target system
19258 are like (for example, the processor's table might be in @sc{rom},
19259 containing entries which point to a table in @sc{ram}).
19260 @var{exception_number} is the exception number which should be changed;
19261 its meaning is architecture-dependent (for example, different numbers
19262 might represent divide by zero, misaligned access, etc). When this
19263 exception occurs, control should be transferred directly to
19264 @var{exception_address}, and the processor state (stack, registers,
19265 and so on) should be just as it is when a processor exception occurs. So if
19266 you want to use a jump instruction to reach @var{exception_address}, it
19267 should be a simple jump, not a jump to subroutine.
19269 For the 386, @var{exception_address} should be installed as an interrupt
19270 gate so that interrupts are masked while the handler runs. The gate
19271 should be at privilege level 0 (the most privileged level). The
19272 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19273 help from @code{exceptionHandler}.
19275 @item void flush_i_cache()
19276 @findex flush_i_cache
19277 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19278 instruction cache, if any, on your target machine. If there is no
19279 instruction cache, this subroutine may be a no-op.
19281 On target machines that have instruction caches, @value{GDBN} requires this
19282 function to make certain that the state of your program is stable.
19286 You must also make sure this library routine is available:
19289 @item void *memset(void *, int, int)
19291 This is the standard library function @code{memset} that sets an area of
19292 memory to a known value. If you have one of the free versions of
19293 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19294 either obtain it from your hardware manufacturer, or write your own.
19297 If you do not use the GNU C compiler, you may need other standard
19298 library subroutines as well; this varies from one stub to another,
19299 but in general the stubs are likely to use any of the common library
19300 subroutines which @code{@value{NGCC}} generates as inline code.
19303 @node Debug Session
19304 @subsection Putting it All Together
19306 @cindex remote serial debugging summary
19307 In summary, when your program is ready to debug, you must follow these
19312 Make sure you have defined the supporting low-level routines
19313 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19315 @code{getDebugChar}, @code{putDebugChar},
19316 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19320 Insert these lines in your program's startup code, before the main
19321 procedure is called:
19328 On some machines, when a breakpoint trap is raised, the hardware
19329 automatically makes the PC point to the instruction after the
19330 breakpoint. If your machine doesn't do that, you may need to adjust
19331 @code{handle_exception} to arrange for it to return to the instruction
19332 after the breakpoint on this first invocation, so that your program
19333 doesn't keep hitting the initial breakpoint instead of making
19337 For the 680x0 stub only, you need to provide a variable called
19338 @code{exceptionHook}. Normally you just use:
19341 void (*exceptionHook)() = 0;
19345 but if before calling @code{set_debug_traps}, you set it to point to a
19346 function in your program, that function is called when
19347 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19348 error). The function indicated by @code{exceptionHook} is called with
19349 one parameter: an @code{int} which is the exception number.
19352 Compile and link together: your program, the @value{GDBN} debugging stub for
19353 your target architecture, and the supporting subroutines.
19356 Make sure you have a serial connection between your target machine and
19357 the @value{GDBN} host, and identify the serial port on the host.
19360 @c The "remote" target now provides a `load' command, so we should
19361 @c document that. FIXME.
19362 Download your program to your target machine (or get it there by
19363 whatever means the manufacturer provides), and start it.
19366 Start @value{GDBN} on the host, and connect to the target
19367 (@pxref{Connecting,,Connecting to a Remote Target}).
19371 @node Configurations
19372 @chapter Configuration-Specific Information
19374 While nearly all @value{GDBN} commands are available for all native and
19375 cross versions of the debugger, there are some exceptions. This chapter
19376 describes things that are only available in certain configurations.
19378 There are three major categories of configurations: native
19379 configurations, where the host and target are the same, embedded
19380 operating system configurations, which are usually the same for several
19381 different processor architectures, and bare embedded processors, which
19382 are quite different from each other.
19387 * Embedded Processors::
19394 This section describes details specific to particular native
19399 * BSD libkvm Interface:: Debugging BSD kernel memory images
19400 * SVR4 Process Information:: SVR4 process information
19401 * DJGPP Native:: Features specific to the DJGPP port
19402 * Cygwin Native:: Features specific to the Cygwin port
19403 * Hurd Native:: Features specific to @sc{gnu} Hurd
19404 * Darwin:: Features specific to Darwin
19410 On HP-UX systems, if you refer to a function or variable name that
19411 begins with a dollar sign, @value{GDBN} searches for a user or system
19412 name first, before it searches for a convenience variable.
19415 @node BSD libkvm Interface
19416 @subsection BSD libkvm Interface
19419 @cindex kernel memory image
19420 @cindex kernel crash dump
19422 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19423 interface that provides a uniform interface for accessing kernel virtual
19424 memory images, including live systems and crash dumps. @value{GDBN}
19425 uses this interface to allow you to debug live kernels and kernel crash
19426 dumps on many native BSD configurations. This is implemented as a
19427 special @code{kvm} debugging target. For debugging a live system, load
19428 the currently running kernel into @value{GDBN} and connect to the
19432 (@value{GDBP}) @b{target kvm}
19435 For debugging crash dumps, provide the file name of the crash dump as an
19439 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19442 Once connected to the @code{kvm} target, the following commands are
19448 Set current context from the @dfn{Process Control Block} (PCB) address.
19451 Set current context from proc address. This command isn't available on
19452 modern FreeBSD systems.
19455 @node SVR4 Process Information
19456 @subsection SVR4 Process Information
19458 @cindex examine process image
19459 @cindex process info via @file{/proc}
19461 Many versions of SVR4 and compatible systems provide a facility called
19462 @samp{/proc} that can be used to examine the image of a running
19463 process using file-system subroutines.
19465 If @value{GDBN} is configured for an operating system with this
19466 facility, the command @code{info proc} is available to report
19467 information about the process running your program, or about any
19468 process running on your system. This includes, as of this writing,
19469 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19470 not HP-UX, for example.
19472 This command may also work on core files that were created on a system
19473 that has the @samp{/proc} facility.
19479 @itemx info proc @var{process-id}
19480 Summarize available information about any running process. If a
19481 process ID is specified by @var{process-id}, display information about
19482 that process; otherwise display information about the program being
19483 debugged. The summary includes the debugged process ID, the command
19484 line used to invoke it, its current working directory, and its
19485 executable file's absolute file name.
19487 On some systems, @var{process-id} can be of the form
19488 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19489 within a process. If the optional @var{pid} part is missing, it means
19490 a thread from the process being debugged (the leading @samp{/} still
19491 needs to be present, or else @value{GDBN} will interpret the number as
19492 a process ID rather than a thread ID).
19494 @item info proc cmdline
19495 @cindex info proc cmdline
19496 Show the original command line of the process. This command is
19497 specific to @sc{gnu}/Linux.
19499 @item info proc cwd
19500 @cindex info proc cwd
19501 Show the current working directory of the process. This command is
19502 specific to @sc{gnu}/Linux.
19504 @item info proc exe
19505 @cindex info proc exe
19506 Show the name of executable of the process. This command is specific
19509 @item info proc mappings
19510 @cindex memory address space mappings
19511 Report the memory address space ranges accessible in the program, with
19512 information on whether the process has read, write, or execute access
19513 rights to each range. On @sc{gnu}/Linux systems, each memory range
19514 includes the object file which is mapped to that range, instead of the
19515 memory access rights to that range.
19517 @item info proc stat
19518 @itemx info proc status
19519 @cindex process detailed status information
19520 These subcommands are specific to @sc{gnu}/Linux systems. They show
19521 the process-related information, including the user ID and group ID;
19522 how many threads are there in the process; its virtual memory usage;
19523 the signals that are pending, blocked, and ignored; its TTY; its
19524 consumption of system and user time; its stack size; its @samp{nice}
19525 value; etc. For more information, see the @samp{proc} man page
19526 (type @kbd{man 5 proc} from your shell prompt).
19528 @item info proc all
19529 Show all the information about the process described under all of the
19530 above @code{info proc} subcommands.
19533 @comment These sub-options of 'info proc' were not included when
19534 @comment procfs.c was re-written. Keep their descriptions around
19535 @comment against the day when someone finds the time to put them back in.
19536 @kindex info proc times
19537 @item info proc times
19538 Starting time, user CPU time, and system CPU time for your program and
19541 @kindex info proc id
19543 Report on the process IDs related to your program: its own process ID,
19544 the ID of its parent, the process group ID, and the session ID.
19547 @item set procfs-trace
19548 @kindex set procfs-trace
19549 @cindex @code{procfs} API calls
19550 This command enables and disables tracing of @code{procfs} API calls.
19552 @item show procfs-trace
19553 @kindex show procfs-trace
19554 Show the current state of @code{procfs} API call tracing.
19556 @item set procfs-file @var{file}
19557 @kindex set procfs-file
19558 Tell @value{GDBN} to write @code{procfs} API trace to the named
19559 @var{file}. @value{GDBN} appends the trace info to the previous
19560 contents of the file. The default is to display the trace on the
19563 @item show procfs-file
19564 @kindex show procfs-file
19565 Show the file to which @code{procfs} API trace is written.
19567 @item proc-trace-entry
19568 @itemx proc-trace-exit
19569 @itemx proc-untrace-entry
19570 @itemx proc-untrace-exit
19571 @kindex proc-trace-entry
19572 @kindex proc-trace-exit
19573 @kindex proc-untrace-entry
19574 @kindex proc-untrace-exit
19575 These commands enable and disable tracing of entries into and exits
19576 from the @code{syscall} interface.
19579 @kindex info pidlist
19580 @cindex process list, QNX Neutrino
19581 For QNX Neutrino only, this command displays the list of all the
19582 processes and all the threads within each process.
19585 @kindex info meminfo
19586 @cindex mapinfo list, QNX Neutrino
19587 For QNX Neutrino only, this command displays the list of all mapinfos.
19591 @subsection Features for Debugging @sc{djgpp} Programs
19592 @cindex @sc{djgpp} debugging
19593 @cindex native @sc{djgpp} debugging
19594 @cindex MS-DOS-specific commands
19597 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19598 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19599 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19600 top of real-mode DOS systems and their emulations.
19602 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19603 defines a few commands specific to the @sc{djgpp} port. This
19604 subsection describes those commands.
19609 This is a prefix of @sc{djgpp}-specific commands which print
19610 information about the target system and important OS structures.
19613 @cindex MS-DOS system info
19614 @cindex free memory information (MS-DOS)
19615 @item info dos sysinfo
19616 This command displays assorted information about the underlying
19617 platform: the CPU type and features, the OS version and flavor, the
19618 DPMI version, and the available conventional and DPMI memory.
19623 @cindex segment descriptor tables
19624 @cindex descriptor tables display
19626 @itemx info dos ldt
19627 @itemx info dos idt
19628 These 3 commands display entries from, respectively, Global, Local,
19629 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19630 tables are data structures which store a descriptor for each segment
19631 that is currently in use. The segment's selector is an index into a
19632 descriptor table; the table entry for that index holds the
19633 descriptor's base address and limit, and its attributes and access
19636 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19637 segment (used for both data and the stack), and a DOS segment (which
19638 allows access to DOS/BIOS data structures and absolute addresses in
19639 conventional memory). However, the DPMI host will usually define
19640 additional segments in order to support the DPMI environment.
19642 @cindex garbled pointers
19643 These commands allow to display entries from the descriptor tables.
19644 Without an argument, all entries from the specified table are
19645 displayed. An argument, which should be an integer expression, means
19646 display a single entry whose index is given by the argument. For
19647 example, here's a convenient way to display information about the
19648 debugged program's data segment:
19651 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19652 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19656 This comes in handy when you want to see whether a pointer is outside
19657 the data segment's limit (i.e.@: @dfn{garbled}).
19659 @cindex page tables display (MS-DOS)
19661 @itemx info dos pte
19662 These two commands display entries from, respectively, the Page
19663 Directory and the Page Tables. Page Directories and Page Tables are
19664 data structures which control how virtual memory addresses are mapped
19665 into physical addresses. A Page Table includes an entry for every
19666 page of memory that is mapped into the program's address space; there
19667 may be several Page Tables, each one holding up to 4096 entries. A
19668 Page Directory has up to 4096 entries, one each for every Page Table
19669 that is currently in use.
19671 Without an argument, @kbd{info dos pde} displays the entire Page
19672 Directory, and @kbd{info dos pte} displays all the entries in all of
19673 the Page Tables. An argument, an integer expression, given to the
19674 @kbd{info dos pde} command means display only that entry from the Page
19675 Directory table. An argument given to the @kbd{info dos pte} command
19676 means display entries from a single Page Table, the one pointed to by
19677 the specified entry in the Page Directory.
19679 @cindex direct memory access (DMA) on MS-DOS
19680 These commands are useful when your program uses @dfn{DMA} (Direct
19681 Memory Access), which needs physical addresses to program the DMA
19684 These commands are supported only with some DPMI servers.
19686 @cindex physical address from linear address
19687 @item info dos address-pte @var{addr}
19688 This command displays the Page Table entry for a specified linear
19689 address. The argument @var{addr} is a linear address which should
19690 already have the appropriate segment's base address added to it,
19691 because this command accepts addresses which may belong to @emph{any}
19692 segment. For example, here's how to display the Page Table entry for
19693 the page where a variable @code{i} is stored:
19696 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19697 @exdent @code{Page Table entry for address 0x11a00d30:}
19698 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19702 This says that @code{i} is stored at offset @code{0xd30} from the page
19703 whose physical base address is @code{0x02698000}, and shows all the
19704 attributes of that page.
19706 Note that you must cast the addresses of variables to a @code{char *},
19707 since otherwise the value of @code{__djgpp_base_address}, the base
19708 address of all variables and functions in a @sc{djgpp} program, will
19709 be added using the rules of C pointer arithmetics: if @code{i} is
19710 declared an @code{int}, @value{GDBN} will add 4 times the value of
19711 @code{__djgpp_base_address} to the address of @code{i}.
19713 Here's another example, it displays the Page Table entry for the
19717 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19718 @exdent @code{Page Table entry for address 0x29110:}
19719 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19723 (The @code{+ 3} offset is because the transfer buffer's address is the
19724 3rd member of the @code{_go32_info_block} structure.) The output
19725 clearly shows that this DPMI server maps the addresses in conventional
19726 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19727 linear (@code{0x29110}) addresses are identical.
19729 This command is supported only with some DPMI servers.
19732 @cindex DOS serial data link, remote debugging
19733 In addition to native debugging, the DJGPP port supports remote
19734 debugging via a serial data link. The following commands are specific
19735 to remote serial debugging in the DJGPP port of @value{GDBN}.
19738 @kindex set com1base
19739 @kindex set com1irq
19740 @kindex set com2base
19741 @kindex set com2irq
19742 @kindex set com3base
19743 @kindex set com3irq
19744 @kindex set com4base
19745 @kindex set com4irq
19746 @item set com1base @var{addr}
19747 This command sets the base I/O port address of the @file{COM1} serial
19750 @item set com1irq @var{irq}
19751 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19752 for the @file{COM1} serial port.
19754 There are similar commands @samp{set com2base}, @samp{set com3irq},
19755 etc.@: for setting the port address and the @code{IRQ} lines for the
19758 @kindex show com1base
19759 @kindex show com1irq
19760 @kindex show com2base
19761 @kindex show com2irq
19762 @kindex show com3base
19763 @kindex show com3irq
19764 @kindex show com4base
19765 @kindex show com4irq
19766 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19767 display the current settings of the base address and the @code{IRQ}
19768 lines used by the COM ports.
19771 @kindex info serial
19772 @cindex DOS serial port status
19773 This command prints the status of the 4 DOS serial ports. For each
19774 port, it prints whether it's active or not, its I/O base address and
19775 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19776 counts of various errors encountered so far.
19780 @node Cygwin Native
19781 @subsection Features for Debugging MS Windows PE Executables
19782 @cindex MS Windows debugging
19783 @cindex native Cygwin debugging
19784 @cindex Cygwin-specific commands
19786 @value{GDBN} supports native debugging of MS Windows programs, including
19787 DLLs with and without symbolic debugging information.
19789 @cindex Ctrl-BREAK, MS-Windows
19790 @cindex interrupt debuggee on MS-Windows
19791 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19792 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19793 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19794 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19795 sequence, which can be used to interrupt the debuggee even if it
19798 There are various additional Cygwin-specific commands, described in
19799 this section. Working with DLLs that have no debugging symbols is
19800 described in @ref{Non-debug DLL Symbols}.
19805 This is a prefix of MS Windows-specific commands which print
19806 information about the target system and important OS structures.
19808 @item info w32 selector
19809 This command displays information returned by
19810 the Win32 API @code{GetThreadSelectorEntry} function.
19811 It takes an optional argument that is evaluated to
19812 a long value to give the information about this given selector.
19813 Without argument, this command displays information
19814 about the six segment registers.
19816 @item info w32 thread-information-block
19817 This command displays thread specific information stored in the
19818 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19819 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19823 This is a Cygwin-specific alias of @code{info shared}.
19825 @kindex dll-symbols
19827 This command loads symbols from a dll similarly to
19828 add-sym command but without the need to specify a base address.
19830 @kindex set cygwin-exceptions
19831 @cindex debugging the Cygwin DLL
19832 @cindex Cygwin DLL, debugging
19833 @item set cygwin-exceptions @var{mode}
19834 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19835 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19836 @value{GDBN} will delay recognition of exceptions, and may ignore some
19837 exceptions which seem to be caused by internal Cygwin DLL
19838 ``bookkeeping''. This option is meant primarily for debugging the
19839 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19840 @value{GDBN} users with false @code{SIGSEGV} signals.
19842 @kindex show cygwin-exceptions
19843 @item show cygwin-exceptions
19844 Displays whether @value{GDBN} will break on exceptions that happen
19845 inside the Cygwin DLL itself.
19847 @kindex set new-console
19848 @item set new-console @var{mode}
19849 If @var{mode} is @code{on} the debuggee will
19850 be started in a new console on next start.
19851 If @var{mode} is @code{off}, the debuggee will
19852 be started in the same console as the debugger.
19854 @kindex show new-console
19855 @item show new-console
19856 Displays whether a new console is used
19857 when the debuggee is started.
19859 @kindex set new-group
19860 @item set new-group @var{mode}
19861 This boolean value controls whether the debuggee should
19862 start a new group or stay in the same group as the debugger.
19863 This affects the way the Windows OS handles
19866 @kindex show new-group
19867 @item show new-group
19868 Displays current value of new-group boolean.
19870 @kindex set debugevents
19871 @item set debugevents
19872 This boolean value adds debug output concerning kernel events related
19873 to the debuggee seen by the debugger. This includes events that
19874 signal thread and process creation and exit, DLL loading and
19875 unloading, console interrupts, and debugging messages produced by the
19876 Windows @code{OutputDebugString} API call.
19878 @kindex set debugexec
19879 @item set debugexec
19880 This boolean value adds debug output concerning execute events
19881 (such as resume thread) seen by the debugger.
19883 @kindex set debugexceptions
19884 @item set debugexceptions
19885 This boolean value adds debug output concerning exceptions in the
19886 debuggee seen by the debugger.
19888 @kindex set debugmemory
19889 @item set debugmemory
19890 This boolean value adds debug output concerning debuggee memory reads
19891 and writes by the debugger.
19895 This boolean values specifies whether the debuggee is called
19896 via a shell or directly (default value is on).
19900 Displays if the debuggee will be started with a shell.
19905 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19908 @node Non-debug DLL Symbols
19909 @subsubsection Support for DLLs without Debugging Symbols
19910 @cindex DLLs with no debugging symbols
19911 @cindex Minimal symbols and DLLs
19913 Very often on windows, some of the DLLs that your program relies on do
19914 not include symbolic debugging information (for example,
19915 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19916 symbols in a DLL, it relies on the minimal amount of symbolic
19917 information contained in the DLL's export table. This section
19918 describes working with such symbols, known internally to @value{GDBN} as
19919 ``minimal symbols''.
19921 Note that before the debugged program has started execution, no DLLs
19922 will have been loaded. The easiest way around this problem is simply to
19923 start the program --- either by setting a breakpoint or letting the
19924 program run once to completion. It is also possible to force
19925 @value{GDBN} to load a particular DLL before starting the executable ---
19926 see the shared library information in @ref{Files}, or the
19927 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19928 explicitly loading symbols from a DLL with no debugging information will
19929 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19930 which may adversely affect symbol lookup performance.
19932 @subsubsection DLL Name Prefixes
19934 In keeping with the naming conventions used by the Microsoft debugging
19935 tools, DLL export symbols are made available with a prefix based on the
19936 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19937 also entered into the symbol table, so @code{CreateFileA} is often
19938 sufficient. In some cases there will be name clashes within a program
19939 (particularly if the executable itself includes full debugging symbols)
19940 necessitating the use of the fully qualified name when referring to the
19941 contents of the DLL. Use single-quotes around the name to avoid the
19942 exclamation mark (``!'') being interpreted as a language operator.
19944 Note that the internal name of the DLL may be all upper-case, even
19945 though the file name of the DLL is lower-case, or vice-versa. Since
19946 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19947 some confusion. If in doubt, try the @code{info functions} and
19948 @code{info variables} commands or even @code{maint print msymbols}
19949 (@pxref{Symbols}). Here's an example:
19952 (@value{GDBP}) info function CreateFileA
19953 All functions matching regular expression "CreateFileA":
19955 Non-debugging symbols:
19956 0x77e885f4 CreateFileA
19957 0x77e885f4 KERNEL32!CreateFileA
19961 (@value{GDBP}) info function !
19962 All functions matching regular expression "!":
19964 Non-debugging symbols:
19965 0x6100114c cygwin1!__assert
19966 0x61004034 cygwin1!_dll_crt0@@0
19967 0x61004240 cygwin1!dll_crt0(per_process *)
19971 @subsubsection Working with Minimal Symbols
19973 Symbols extracted from a DLL's export table do not contain very much
19974 type information. All that @value{GDBN} can do is guess whether a symbol
19975 refers to a function or variable depending on the linker section that
19976 contains the symbol. Also note that the actual contents of the memory
19977 contained in a DLL are not available unless the program is running. This
19978 means that you cannot examine the contents of a variable or disassemble
19979 a function within a DLL without a running program.
19981 Variables are generally treated as pointers and dereferenced
19982 automatically. For this reason, it is often necessary to prefix a
19983 variable name with the address-of operator (``&'') and provide explicit
19984 type information in the command. Here's an example of the type of
19988 (@value{GDBP}) print 'cygwin1!__argv'
19993 (@value{GDBP}) x 'cygwin1!__argv'
19994 0x10021610: "\230y\""
19997 And two possible solutions:
20000 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20001 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20005 (@value{GDBP}) x/2x &'cygwin1!__argv'
20006 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20007 (@value{GDBP}) x/x 0x10021608
20008 0x10021608: 0x0022fd98
20009 (@value{GDBP}) x/s 0x0022fd98
20010 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20013 Setting a break point within a DLL is possible even before the program
20014 starts execution. However, under these circumstances, @value{GDBN} can't
20015 examine the initial instructions of the function in order to skip the
20016 function's frame set-up code. You can work around this by using ``*&''
20017 to set the breakpoint at a raw memory address:
20020 (@value{GDBP}) break *&'python22!PyOS_Readline'
20021 Breakpoint 1 at 0x1e04eff0
20024 The author of these extensions is not entirely convinced that setting a
20025 break point within a shared DLL like @file{kernel32.dll} is completely
20029 @subsection Commands Specific to @sc{gnu} Hurd Systems
20030 @cindex @sc{gnu} Hurd debugging
20032 This subsection describes @value{GDBN} commands specific to the
20033 @sc{gnu} Hurd native debugging.
20038 @kindex set signals@r{, Hurd command}
20039 @kindex set sigs@r{, Hurd command}
20040 This command toggles the state of inferior signal interception by
20041 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20042 affected by this command. @code{sigs} is a shorthand alias for
20047 @kindex show signals@r{, Hurd command}
20048 @kindex show sigs@r{, Hurd command}
20049 Show the current state of intercepting inferior's signals.
20051 @item set signal-thread
20052 @itemx set sigthread
20053 @kindex set signal-thread
20054 @kindex set sigthread
20055 This command tells @value{GDBN} which thread is the @code{libc} signal
20056 thread. That thread is run when a signal is delivered to a running
20057 process. @code{set sigthread} is the shorthand alias of @code{set
20060 @item show signal-thread
20061 @itemx show sigthread
20062 @kindex show signal-thread
20063 @kindex show sigthread
20064 These two commands show which thread will run when the inferior is
20065 delivered a signal.
20068 @kindex set stopped@r{, Hurd command}
20069 This commands tells @value{GDBN} that the inferior process is stopped,
20070 as with the @code{SIGSTOP} signal. The stopped process can be
20071 continued by delivering a signal to it.
20074 @kindex show stopped@r{, Hurd command}
20075 This command shows whether @value{GDBN} thinks the debuggee is
20078 @item set exceptions
20079 @kindex set exceptions@r{, Hurd command}
20080 Use this command to turn off trapping of exceptions in the inferior.
20081 When exception trapping is off, neither breakpoints nor
20082 single-stepping will work. To restore the default, set exception
20085 @item show exceptions
20086 @kindex show exceptions@r{, Hurd command}
20087 Show the current state of trapping exceptions in the inferior.
20089 @item set task pause
20090 @kindex set task@r{, Hurd commands}
20091 @cindex task attributes (@sc{gnu} Hurd)
20092 @cindex pause current task (@sc{gnu} Hurd)
20093 This command toggles task suspension when @value{GDBN} has control.
20094 Setting it to on takes effect immediately, and the task is suspended
20095 whenever @value{GDBN} gets control. Setting it to off will take
20096 effect the next time the inferior is continued. If this option is set
20097 to off, you can use @code{set thread default pause on} or @code{set
20098 thread pause on} (see below) to pause individual threads.
20100 @item show task pause
20101 @kindex show task@r{, Hurd commands}
20102 Show the current state of task suspension.
20104 @item set task detach-suspend-count
20105 @cindex task suspend count
20106 @cindex detach from task, @sc{gnu} Hurd
20107 This command sets the suspend count the task will be left with when
20108 @value{GDBN} detaches from it.
20110 @item show task detach-suspend-count
20111 Show the suspend count the task will be left with when detaching.
20113 @item set task exception-port
20114 @itemx set task excp
20115 @cindex task exception port, @sc{gnu} Hurd
20116 This command sets the task exception port to which @value{GDBN} will
20117 forward exceptions. The argument should be the value of the @dfn{send
20118 rights} of the task. @code{set task excp} is a shorthand alias.
20120 @item set noninvasive
20121 @cindex noninvasive task options
20122 This command switches @value{GDBN} to a mode that is the least
20123 invasive as far as interfering with the inferior is concerned. This
20124 is the same as using @code{set task pause}, @code{set exceptions}, and
20125 @code{set signals} to values opposite to the defaults.
20127 @item info send-rights
20128 @itemx info receive-rights
20129 @itemx info port-rights
20130 @itemx info port-sets
20131 @itemx info dead-names
20134 @cindex send rights, @sc{gnu} Hurd
20135 @cindex receive rights, @sc{gnu} Hurd
20136 @cindex port rights, @sc{gnu} Hurd
20137 @cindex port sets, @sc{gnu} Hurd
20138 @cindex dead names, @sc{gnu} Hurd
20139 These commands display information about, respectively, send rights,
20140 receive rights, port rights, port sets, and dead names of a task.
20141 There are also shorthand aliases: @code{info ports} for @code{info
20142 port-rights} and @code{info psets} for @code{info port-sets}.
20144 @item set thread pause
20145 @kindex set thread@r{, Hurd command}
20146 @cindex thread properties, @sc{gnu} Hurd
20147 @cindex pause current thread (@sc{gnu} Hurd)
20148 This command toggles current thread suspension when @value{GDBN} has
20149 control. Setting it to on takes effect immediately, and the current
20150 thread is suspended whenever @value{GDBN} gets control. Setting it to
20151 off will take effect the next time the inferior is continued.
20152 Normally, this command has no effect, since when @value{GDBN} has
20153 control, the whole task is suspended. However, if you used @code{set
20154 task pause off} (see above), this command comes in handy to suspend
20155 only the current thread.
20157 @item show thread pause
20158 @kindex show thread@r{, Hurd command}
20159 This command shows the state of current thread suspension.
20161 @item set thread run
20162 This command sets whether the current thread is allowed to run.
20164 @item show thread run
20165 Show whether the current thread is allowed to run.
20167 @item set thread detach-suspend-count
20168 @cindex thread suspend count, @sc{gnu} Hurd
20169 @cindex detach from thread, @sc{gnu} Hurd
20170 This command sets the suspend count @value{GDBN} will leave on a
20171 thread when detaching. This number is relative to the suspend count
20172 found by @value{GDBN} when it notices the thread; use @code{set thread
20173 takeover-suspend-count} to force it to an absolute value.
20175 @item show thread detach-suspend-count
20176 Show the suspend count @value{GDBN} will leave on the thread when
20179 @item set thread exception-port
20180 @itemx set thread excp
20181 Set the thread exception port to which to forward exceptions. This
20182 overrides the port set by @code{set task exception-port} (see above).
20183 @code{set thread excp} is the shorthand alias.
20185 @item set thread takeover-suspend-count
20186 Normally, @value{GDBN}'s thread suspend counts are relative to the
20187 value @value{GDBN} finds when it notices each thread. This command
20188 changes the suspend counts to be absolute instead.
20190 @item set thread default
20191 @itemx show thread default
20192 @cindex thread default settings, @sc{gnu} Hurd
20193 Each of the above @code{set thread} commands has a @code{set thread
20194 default} counterpart (e.g., @code{set thread default pause}, @code{set
20195 thread default exception-port}, etc.). The @code{thread default}
20196 variety of commands sets the default thread properties for all
20197 threads; you can then change the properties of individual threads with
20198 the non-default commands.
20205 @value{GDBN} provides the following commands specific to the Darwin target:
20208 @item set debug darwin @var{num}
20209 @kindex set debug darwin
20210 When set to a non zero value, enables debugging messages specific to
20211 the Darwin support. Higher values produce more verbose output.
20213 @item show debug darwin
20214 @kindex show debug darwin
20215 Show the current state of Darwin messages.
20217 @item set debug mach-o @var{num}
20218 @kindex set debug mach-o
20219 When set to a non zero value, enables debugging messages while
20220 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20221 file format used on Darwin for object and executable files.) Higher
20222 values produce more verbose output. This is a command to diagnose
20223 problems internal to @value{GDBN} and should not be needed in normal
20226 @item show debug mach-o
20227 @kindex show debug mach-o
20228 Show the current state of Mach-O file messages.
20230 @item set mach-exceptions on
20231 @itemx set mach-exceptions off
20232 @kindex set mach-exceptions
20233 On Darwin, faults are first reported as a Mach exception and are then
20234 mapped to a Posix signal. Use this command to turn on trapping of
20235 Mach exceptions in the inferior. This might be sometimes useful to
20236 better understand the cause of a fault. The default is off.
20238 @item show mach-exceptions
20239 @kindex show mach-exceptions
20240 Show the current state of exceptions trapping.
20245 @section Embedded Operating Systems
20247 This section describes configurations involving the debugging of
20248 embedded operating systems that are available for several different
20252 * VxWorks:: Using @value{GDBN} with VxWorks
20255 @value{GDBN} includes the ability to debug programs running on
20256 various real-time operating systems.
20259 @subsection Using @value{GDBN} with VxWorks
20265 @kindex target vxworks
20266 @item target vxworks @var{machinename}
20267 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20268 is the target system's machine name or IP address.
20272 On VxWorks, @code{load} links @var{filename} dynamically on the
20273 current target system as well as adding its symbols in @value{GDBN}.
20275 @value{GDBN} enables developers to spawn and debug tasks running on networked
20276 VxWorks targets from a Unix host. Already-running tasks spawned from
20277 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20278 both the Unix host and on the VxWorks target. The program
20279 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20280 installed with the name @code{vxgdb}, to distinguish it from a
20281 @value{GDBN} for debugging programs on the host itself.)
20284 @item VxWorks-timeout @var{args}
20285 @kindex vxworks-timeout
20286 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20287 This option is set by the user, and @var{args} represents the number of
20288 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20289 your VxWorks target is a slow software simulator or is on the far side
20290 of a thin network line.
20293 The following information on connecting to VxWorks was current when
20294 this manual was produced; newer releases of VxWorks may use revised
20297 @findex INCLUDE_RDB
20298 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20299 to include the remote debugging interface routines in the VxWorks
20300 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20301 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20302 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20303 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20304 information on configuring and remaking VxWorks, see the manufacturer's
20306 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20308 Once you have included @file{rdb.a} in your VxWorks system image and set
20309 your Unix execution search path to find @value{GDBN}, you are ready to
20310 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20311 @code{vxgdb}, depending on your installation).
20313 @value{GDBN} comes up showing the prompt:
20320 * VxWorks Connection:: Connecting to VxWorks
20321 * VxWorks Download:: VxWorks download
20322 * VxWorks Attach:: Running tasks
20325 @node VxWorks Connection
20326 @subsubsection Connecting to VxWorks
20328 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20329 network. To connect to a target whose host name is ``@code{tt}'', type:
20332 (vxgdb) target vxworks tt
20336 @value{GDBN} displays messages like these:
20339 Attaching remote machine across net...
20344 @value{GDBN} then attempts to read the symbol tables of any object modules
20345 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20346 these files by searching the directories listed in the command search
20347 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20348 to find an object file, it displays a message such as:
20351 prog.o: No such file or directory.
20354 When this happens, add the appropriate directory to the search path with
20355 the @value{GDBN} command @code{path}, and execute the @code{target}
20358 @node VxWorks Download
20359 @subsubsection VxWorks Download
20361 @cindex download to VxWorks
20362 If you have connected to the VxWorks target and you want to debug an
20363 object that has not yet been loaded, you can use the @value{GDBN}
20364 @code{load} command to download a file from Unix to VxWorks
20365 incrementally. The object file given as an argument to the @code{load}
20366 command is actually opened twice: first by the VxWorks target in order
20367 to download the code, then by @value{GDBN} in order to read the symbol
20368 table. This can lead to problems if the current working directories on
20369 the two systems differ. If both systems have NFS mounted the same
20370 filesystems, you can avoid these problems by using absolute paths.
20371 Otherwise, it is simplest to set the working directory on both systems
20372 to the directory in which the object file resides, and then to reference
20373 the file by its name, without any path. For instance, a program
20374 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20375 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20376 program, type this on VxWorks:
20379 -> cd "@var{vxpath}/vw/demo/rdb"
20383 Then, in @value{GDBN}, type:
20386 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20387 (vxgdb) load prog.o
20390 @value{GDBN} displays a response similar to this:
20393 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20396 You can also use the @code{load} command to reload an object module
20397 after editing and recompiling the corresponding source file. Note that
20398 this makes @value{GDBN} delete all currently-defined breakpoints,
20399 auto-displays, and convenience variables, and to clear the value
20400 history. (This is necessary in order to preserve the integrity of
20401 debugger's data structures that reference the target system's symbol
20404 @node VxWorks Attach
20405 @subsubsection Running Tasks
20407 @cindex running VxWorks tasks
20408 You can also attach to an existing task using the @code{attach} command as
20412 (vxgdb) attach @var{task}
20416 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20417 or suspended when you attach to it. Running tasks are suspended at
20418 the time of attachment.
20420 @node Embedded Processors
20421 @section Embedded Processors
20423 This section goes into details specific to particular embedded
20426 @cindex send command to simulator
20427 Whenever a specific embedded processor has a simulator, @value{GDBN}
20428 allows to send an arbitrary command to the simulator.
20431 @item sim @var{command}
20432 @kindex sim@r{, a command}
20433 Send an arbitrary @var{command} string to the simulator. Consult the
20434 documentation for the specific simulator in use for information about
20435 acceptable commands.
20441 * M32R/D:: Renesas M32R/D
20442 * M68K:: Motorola M68K
20443 * MicroBlaze:: Xilinx MicroBlaze
20444 * MIPS Embedded:: MIPS Embedded
20445 * PowerPC Embedded:: PowerPC Embedded
20446 * PA:: HP PA Embedded
20447 * Sparclet:: Tsqware Sparclet
20448 * Sparclite:: Fujitsu Sparclite
20449 * Z8000:: Zilog Z8000
20452 * Super-H:: Renesas Super-H
20461 @item target rdi @var{dev}
20462 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20463 use this target to communicate with both boards running the Angel
20464 monitor, or with the EmbeddedICE JTAG debug device.
20467 @item target rdp @var{dev}
20472 @value{GDBN} provides the following ARM-specific commands:
20475 @item set arm disassembler
20477 This commands selects from a list of disassembly styles. The
20478 @code{"std"} style is the standard style.
20480 @item show arm disassembler
20482 Show the current disassembly style.
20484 @item set arm apcs32
20485 @cindex ARM 32-bit mode
20486 This command toggles ARM operation mode between 32-bit and 26-bit.
20488 @item show arm apcs32
20489 Display the current usage of the ARM 32-bit mode.
20491 @item set arm fpu @var{fputype}
20492 This command sets the ARM floating-point unit (FPU) type. The
20493 argument @var{fputype} can be one of these:
20497 Determine the FPU type by querying the OS ABI.
20499 Software FPU, with mixed-endian doubles on little-endian ARM
20502 GCC-compiled FPA co-processor.
20504 Software FPU with pure-endian doubles.
20510 Show the current type of the FPU.
20513 This command forces @value{GDBN} to use the specified ABI.
20516 Show the currently used ABI.
20518 @item set arm fallback-mode (arm|thumb|auto)
20519 @value{GDBN} uses the symbol table, when available, to determine
20520 whether instructions are ARM or Thumb. This command controls
20521 @value{GDBN}'s default behavior when the symbol table is not
20522 available. The default is @samp{auto}, which causes @value{GDBN} to
20523 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20526 @item show arm fallback-mode
20527 Show the current fallback instruction mode.
20529 @item set arm force-mode (arm|thumb|auto)
20530 This command overrides use of the symbol table to determine whether
20531 instructions are ARM or Thumb. The default is @samp{auto}, which
20532 causes @value{GDBN} to use the symbol table and then the setting
20533 of @samp{set arm fallback-mode}.
20535 @item show arm force-mode
20536 Show the current forced instruction mode.
20538 @item set debug arm
20539 Toggle whether to display ARM-specific debugging messages from the ARM
20540 target support subsystem.
20542 @item show debug arm
20543 Show whether ARM-specific debugging messages are enabled.
20546 The following commands are available when an ARM target is debugged
20547 using the RDI interface:
20550 @item rdilogfile @r{[}@var{file}@r{]}
20552 @cindex ADP (Angel Debugger Protocol) logging
20553 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20554 With an argument, sets the log file to the specified @var{file}. With
20555 no argument, show the current log file name. The default log file is
20558 @item rdilogenable @r{[}@var{arg}@r{]}
20559 @kindex rdilogenable
20560 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20561 enables logging, with an argument 0 or @code{"no"} disables it. With
20562 no arguments displays the current setting. When logging is enabled,
20563 ADP packets exchanged between @value{GDBN} and the RDI target device
20564 are logged to a file.
20566 @item set rdiromatzero
20567 @kindex set rdiromatzero
20568 @cindex ROM at zero address, RDI
20569 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20570 vector catching is disabled, so that zero address can be used. If off
20571 (the default), vector catching is enabled. For this command to take
20572 effect, it needs to be invoked prior to the @code{target rdi} command.
20574 @item show rdiromatzero
20575 @kindex show rdiromatzero
20576 Show the current setting of ROM at zero address.
20578 @item set rdiheartbeat
20579 @kindex set rdiheartbeat
20580 @cindex RDI heartbeat
20581 Enable or disable RDI heartbeat packets. It is not recommended to
20582 turn on this option, since it confuses ARM and EPI JTAG interface, as
20583 well as the Angel monitor.
20585 @item show rdiheartbeat
20586 @kindex show rdiheartbeat
20587 Show the setting of RDI heartbeat packets.
20591 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20592 The @value{GDBN} ARM simulator accepts the following optional arguments.
20595 @item --swi-support=@var{type}
20596 Tell the simulator which SWI interfaces to support.
20597 @var{type} may be a comma separated list of the following values.
20598 The default value is @code{all}.
20611 @subsection Renesas M32R/D and M32R/SDI
20614 @kindex target m32r
20615 @item target m32r @var{dev}
20616 Renesas M32R/D ROM monitor.
20618 @kindex target m32rsdi
20619 @item target m32rsdi @var{dev}
20620 Renesas M32R SDI server, connected via parallel port to the board.
20623 The following @value{GDBN} commands are specific to the M32R monitor:
20626 @item set download-path @var{path}
20627 @kindex set download-path
20628 @cindex find downloadable @sc{srec} files (M32R)
20629 Set the default path for finding downloadable @sc{srec} files.
20631 @item show download-path
20632 @kindex show download-path
20633 Show the default path for downloadable @sc{srec} files.
20635 @item set board-address @var{addr}
20636 @kindex set board-address
20637 @cindex M32-EVA target board address
20638 Set the IP address for the M32R-EVA target board.
20640 @item show board-address
20641 @kindex show board-address
20642 Show the current IP address of the target board.
20644 @item set server-address @var{addr}
20645 @kindex set server-address
20646 @cindex download server address (M32R)
20647 Set the IP address for the download server, which is the @value{GDBN}'s
20650 @item show server-address
20651 @kindex show server-address
20652 Display the IP address of the download server.
20654 @item upload @r{[}@var{file}@r{]}
20655 @kindex upload@r{, M32R}
20656 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20657 upload capability. If no @var{file} argument is given, the current
20658 executable file is uploaded.
20660 @item tload @r{[}@var{file}@r{]}
20661 @kindex tload@r{, M32R}
20662 Test the @code{upload} command.
20665 The following commands are available for M32R/SDI:
20670 @cindex reset SDI connection, M32R
20671 This command resets the SDI connection.
20675 This command shows the SDI connection status.
20678 @kindex debug_chaos
20679 @cindex M32R/Chaos debugging
20680 Instructs the remote that M32R/Chaos debugging is to be used.
20682 @item use_debug_dma
20683 @kindex use_debug_dma
20684 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20687 @kindex use_mon_code
20688 Instructs the remote to use the MON_CODE method of accessing memory.
20691 @kindex use_ib_break
20692 Instructs the remote to set breakpoints by IB break.
20694 @item use_dbt_break
20695 @kindex use_dbt_break
20696 Instructs the remote to set breakpoints by DBT.
20702 The Motorola m68k configuration includes ColdFire support, and a
20703 target command for the following ROM monitor.
20707 @kindex target dbug
20708 @item target dbug @var{dev}
20709 dBUG ROM monitor for Motorola ColdFire.
20714 @subsection MicroBlaze
20715 @cindex Xilinx MicroBlaze
20716 @cindex XMD, Xilinx Microprocessor Debugger
20718 The MicroBlaze is a soft-core processor supported on various Xilinx
20719 FPGAs, such as Spartan or Virtex series. Boards with these processors
20720 usually have JTAG ports which connect to a host system running the Xilinx
20721 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20722 This host system is used to download the configuration bitstream to
20723 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20724 communicates with the target board using the JTAG interface and
20725 presents a @code{gdbserver} interface to the board. By default
20726 @code{xmd} uses port @code{1234}. (While it is possible to change
20727 this default port, it requires the use of undocumented @code{xmd}
20728 commands. Contact Xilinx support if you need to do this.)
20730 Use these GDB commands to connect to the MicroBlaze target processor.
20733 @item target remote :1234
20734 Use this command to connect to the target if you are running @value{GDBN}
20735 on the same system as @code{xmd}.
20737 @item target remote @var{xmd-host}:1234
20738 Use this command to connect to the target if it is connected to @code{xmd}
20739 running on a different system named @var{xmd-host}.
20742 Use this command to download a program to the MicroBlaze target.
20744 @item set debug microblaze @var{n}
20745 Enable MicroBlaze-specific debugging messages if non-zero.
20747 @item show debug microblaze @var{n}
20748 Show MicroBlaze-specific debugging level.
20751 @node MIPS Embedded
20752 @subsection @acronym{MIPS} Embedded
20754 @cindex @acronym{MIPS} boards
20755 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20756 @acronym{MIPS} board attached to a serial line. This is available when
20757 you configure @value{GDBN} with @samp{--target=mips-elf}.
20760 Use these @value{GDBN} commands to specify the connection to your target board:
20763 @item target mips @var{port}
20764 @kindex target mips @var{port}
20765 To run a program on the board, start up @code{@value{GDBP}} with the
20766 name of your program as the argument. To connect to the board, use the
20767 command @samp{target mips @var{port}}, where @var{port} is the name of
20768 the serial port connected to the board. If the program has not already
20769 been downloaded to the board, you may use the @code{load} command to
20770 download it. You can then use all the usual @value{GDBN} commands.
20772 For example, this sequence connects to the target board through a serial
20773 port, and loads and runs a program called @var{prog} through the
20777 host$ @value{GDBP} @var{prog}
20778 @value{GDBN} is free software and @dots{}
20779 (@value{GDBP}) target mips /dev/ttyb
20780 (@value{GDBP}) load @var{prog}
20784 @item target mips @var{hostname}:@var{portnumber}
20785 On some @value{GDBN} host configurations, you can specify a TCP
20786 connection (for instance, to a serial line managed by a terminal
20787 concentrator) instead of a serial port, using the syntax
20788 @samp{@var{hostname}:@var{portnumber}}.
20790 @item target pmon @var{port}
20791 @kindex target pmon @var{port}
20794 @item target ddb @var{port}
20795 @kindex target ddb @var{port}
20796 NEC's DDB variant of PMON for Vr4300.
20798 @item target lsi @var{port}
20799 @kindex target lsi @var{port}
20800 LSI variant of PMON.
20802 @kindex target r3900
20803 @item target r3900 @var{dev}
20804 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20806 @kindex target array
20807 @item target array @var{dev}
20808 Array Tech LSI33K RAID controller board.
20814 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20817 @item set mipsfpu double
20818 @itemx set mipsfpu single
20819 @itemx set mipsfpu none
20820 @itemx set mipsfpu auto
20821 @itemx show mipsfpu
20822 @kindex set mipsfpu
20823 @kindex show mipsfpu
20824 @cindex @acronym{MIPS} remote floating point
20825 @cindex floating point, @acronym{MIPS} remote
20826 If your target board does not support the @acronym{MIPS} floating point
20827 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20828 need this, you may wish to put the command in your @value{GDBN} init
20829 file). This tells @value{GDBN} how to find the return value of
20830 functions which return floating point values. It also allows
20831 @value{GDBN} to avoid saving the floating point registers when calling
20832 functions on the board. If you are using a floating point coprocessor
20833 with only single precision floating point support, as on the @sc{r4650}
20834 processor, use the command @samp{set mipsfpu single}. The default
20835 double precision floating point coprocessor may be selected using
20836 @samp{set mipsfpu double}.
20838 In previous versions the only choices were double precision or no
20839 floating point, so @samp{set mipsfpu on} will select double precision
20840 and @samp{set mipsfpu off} will select no floating point.
20842 As usual, you can inquire about the @code{mipsfpu} variable with
20843 @samp{show mipsfpu}.
20845 @item set timeout @var{seconds}
20846 @itemx set retransmit-timeout @var{seconds}
20847 @itemx show timeout
20848 @itemx show retransmit-timeout
20849 @cindex @code{timeout}, @acronym{MIPS} protocol
20850 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20851 @kindex set timeout
20852 @kindex show timeout
20853 @kindex set retransmit-timeout
20854 @kindex show retransmit-timeout
20855 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20856 remote protocol, with the @code{set timeout @var{seconds}} command. The
20857 default is 5 seconds. Similarly, you can control the timeout used while
20858 waiting for an acknowledgment of a packet with the @code{set
20859 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20860 You can inspect both values with @code{show timeout} and @code{show
20861 retransmit-timeout}. (These commands are @emph{only} available when
20862 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20864 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20865 is waiting for your program to stop. In that case, @value{GDBN} waits
20866 forever because it has no way of knowing how long the program is going
20867 to run before stopping.
20869 @item set syn-garbage-limit @var{num}
20870 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20871 @cindex synchronize with remote @acronym{MIPS} target
20872 Limit the maximum number of characters @value{GDBN} should ignore when
20873 it tries to synchronize with the remote target. The default is 10
20874 characters. Setting the limit to -1 means there's no limit.
20876 @item show syn-garbage-limit
20877 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20878 Show the current limit on the number of characters to ignore when
20879 trying to synchronize with the remote system.
20881 @item set monitor-prompt @var{prompt}
20882 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20883 @cindex remote monitor prompt
20884 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20885 remote monitor. The default depends on the target:
20895 @item show monitor-prompt
20896 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20897 Show the current strings @value{GDBN} expects as the prompt from the
20900 @item set monitor-warnings
20901 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20902 Enable or disable monitor warnings about hardware breakpoints. This
20903 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20904 display warning messages whose codes are returned by the @code{lsi}
20905 PMON monitor for breakpoint commands.
20907 @item show monitor-warnings
20908 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20909 Show the current setting of printing monitor warnings.
20911 @item pmon @var{command}
20912 @kindex pmon@r{, @acronym{MIPS} remote}
20913 @cindex send PMON command
20914 This command allows sending an arbitrary @var{command} string to the
20915 monitor. The monitor must be in debug mode for this to work.
20918 @node PowerPC Embedded
20919 @subsection PowerPC Embedded
20921 @cindex DVC register
20922 @value{GDBN} supports using the DVC (Data Value Compare) register to
20923 implement in hardware simple hardware watchpoint conditions of the form:
20926 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20927 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20930 The DVC register will be automatically used when @value{GDBN} detects
20931 such pattern in a condition expression, and the created watchpoint uses one
20932 debug register (either the @code{exact-watchpoints} option is on and the
20933 variable is scalar, or the variable has a length of one byte). This feature
20934 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20937 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20938 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20939 in which case watchpoints using only one debug register are created when
20940 watching variables of scalar types.
20942 You can create an artificial array to watch an arbitrary memory
20943 region using one of the following commands (@pxref{Expressions}):
20946 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20947 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20950 PowerPC embedded processors support masked watchpoints. See the discussion
20951 about the @code{mask} argument in @ref{Set Watchpoints}.
20953 @cindex ranged breakpoint
20954 PowerPC embedded processors support hardware accelerated
20955 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20956 the inferior whenever it executes an instruction at any address within
20957 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20958 use the @code{break-range} command.
20960 @value{GDBN} provides the following PowerPC-specific commands:
20963 @kindex break-range
20964 @item break-range @var{start-location}, @var{end-location}
20965 Set a breakpoint for an address range.
20966 @var{start-location} and @var{end-location} can specify a function name,
20967 a line number, an offset of lines from the current line or from the start
20968 location, or an address of an instruction (see @ref{Specify Location},
20969 for a list of all the possible ways to specify a @var{location}.)
20970 The breakpoint will stop execution of the inferior whenever it
20971 executes an instruction at any address within the specified range,
20972 (including @var{start-location} and @var{end-location}.)
20974 @kindex set powerpc
20975 @item set powerpc soft-float
20976 @itemx show powerpc soft-float
20977 Force @value{GDBN} to use (or not use) a software floating point calling
20978 convention. By default, @value{GDBN} selects the calling convention based
20979 on the selected architecture and the provided executable file.
20981 @item set powerpc vector-abi
20982 @itemx show powerpc vector-abi
20983 Force @value{GDBN} to use the specified calling convention for vector
20984 arguments and return values. The valid options are @samp{auto};
20985 @samp{generic}, to avoid vector registers even if they are present;
20986 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20987 registers. By default, @value{GDBN} selects the calling convention
20988 based on the selected architecture and the provided executable file.
20990 @item set powerpc exact-watchpoints
20991 @itemx show powerpc exact-watchpoints
20992 Allow @value{GDBN} to use only one debug register when watching a variable
20993 of scalar type, thus assuming that the variable is accessed through the
20994 address of its first byte.
20996 @kindex target dink32
20997 @item target dink32 @var{dev}
20998 DINK32 ROM monitor.
21000 @kindex target ppcbug
21001 @item target ppcbug @var{dev}
21002 @kindex target ppcbug1
21003 @item target ppcbug1 @var{dev}
21004 PPCBUG ROM monitor for PowerPC.
21007 @item target sds @var{dev}
21008 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21011 @cindex SDS protocol
21012 The following commands specific to the SDS protocol are supported
21016 @item set sdstimeout @var{nsec}
21017 @kindex set sdstimeout
21018 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21019 default is 2 seconds.
21021 @item show sdstimeout
21022 @kindex show sdstimeout
21023 Show the current value of the SDS timeout.
21025 @item sds @var{command}
21026 @kindex sds@r{, a command}
21027 Send the specified @var{command} string to the SDS monitor.
21032 @subsection HP PA Embedded
21036 @kindex target op50n
21037 @item target op50n @var{dev}
21038 OP50N monitor, running on an OKI HPPA board.
21040 @kindex target w89k
21041 @item target w89k @var{dev}
21042 W89K monitor, running on a Winbond HPPA board.
21047 @subsection Tsqware Sparclet
21051 @value{GDBN} enables developers to debug tasks running on
21052 Sparclet targets from a Unix host.
21053 @value{GDBN} uses code that runs on
21054 both the Unix host and on the Sparclet target. The program
21055 @code{@value{GDBP}} is installed and executed on the Unix host.
21058 @item remotetimeout @var{args}
21059 @kindex remotetimeout
21060 @value{GDBN} supports the option @code{remotetimeout}.
21061 This option is set by the user, and @var{args} represents the number of
21062 seconds @value{GDBN} waits for responses.
21065 @cindex compiling, on Sparclet
21066 When compiling for debugging, include the options @samp{-g} to get debug
21067 information and @samp{-Ttext} to relocate the program to where you wish to
21068 load it on the target. You may also want to add the options @samp{-n} or
21069 @samp{-N} in order to reduce the size of the sections. Example:
21072 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21075 You can use @code{objdump} to verify that the addresses are what you intended:
21078 sparclet-aout-objdump --headers --syms prog
21081 @cindex running, on Sparclet
21083 your Unix execution search path to find @value{GDBN}, you are ready to
21084 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21085 (or @code{sparclet-aout-gdb}, depending on your installation).
21087 @value{GDBN} comes up showing the prompt:
21094 * Sparclet File:: Setting the file to debug
21095 * Sparclet Connection:: Connecting to Sparclet
21096 * Sparclet Download:: Sparclet download
21097 * Sparclet Execution:: Running and debugging
21100 @node Sparclet File
21101 @subsubsection Setting File to Debug
21103 The @value{GDBN} command @code{file} lets you choose with program to debug.
21106 (gdbslet) file prog
21110 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21111 @value{GDBN} locates
21112 the file by searching the directories listed in the command search
21114 If the file was compiled with debug information (option @samp{-g}), source
21115 files will be searched as well.
21116 @value{GDBN} locates
21117 the source files by searching the directories listed in the directory search
21118 path (@pxref{Environment, ,Your Program's Environment}).
21120 to find a file, it displays a message such as:
21123 prog: No such file or directory.
21126 When this happens, add the appropriate directories to the search paths with
21127 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21128 @code{target} command again.
21130 @node Sparclet Connection
21131 @subsubsection Connecting to Sparclet
21133 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21134 To connect to a target on serial port ``@code{ttya}'', type:
21137 (gdbslet) target sparclet /dev/ttya
21138 Remote target sparclet connected to /dev/ttya
21139 main () at ../prog.c:3
21143 @value{GDBN} displays messages like these:
21149 @node Sparclet Download
21150 @subsubsection Sparclet Download
21152 @cindex download to Sparclet
21153 Once connected to the Sparclet target,
21154 you can use the @value{GDBN}
21155 @code{load} command to download the file from the host to the target.
21156 The file name and load offset should be given as arguments to the @code{load}
21158 Since the file format is aout, the program must be loaded to the starting
21159 address. You can use @code{objdump} to find out what this value is. The load
21160 offset is an offset which is added to the VMA (virtual memory address)
21161 of each of the file's sections.
21162 For instance, if the program
21163 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21164 and bss at 0x12010170, in @value{GDBN}, type:
21167 (gdbslet) load prog 0x12010000
21168 Loading section .text, size 0xdb0 vma 0x12010000
21171 If the code is loaded at a different address then what the program was linked
21172 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21173 to tell @value{GDBN} where to map the symbol table.
21175 @node Sparclet Execution
21176 @subsubsection Running and Debugging
21178 @cindex running and debugging Sparclet programs
21179 You can now begin debugging the task using @value{GDBN}'s execution control
21180 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21181 manual for the list of commands.
21185 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21187 Starting program: prog
21188 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21189 3 char *symarg = 0;
21191 4 char *execarg = "hello!";
21196 @subsection Fujitsu Sparclite
21200 @kindex target sparclite
21201 @item target sparclite @var{dev}
21202 Fujitsu sparclite boards, used only for the purpose of loading.
21203 You must use an additional command to debug the program.
21204 For example: target remote @var{dev} using @value{GDBN} standard
21210 @subsection Zilog Z8000
21213 @cindex simulator, Z8000
21214 @cindex Zilog Z8000 simulator
21216 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21219 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21220 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21221 segmented variant). The simulator recognizes which architecture is
21222 appropriate by inspecting the object code.
21225 @item target sim @var{args}
21227 @kindex target sim@r{, with Z8000}
21228 Debug programs on a simulated CPU. If the simulator supports setup
21229 options, specify them via @var{args}.
21233 After specifying this target, you can debug programs for the simulated
21234 CPU in the same style as programs for your host computer; use the
21235 @code{file} command to load a new program image, the @code{run} command
21236 to run your program, and so on.
21238 As well as making available all the usual machine registers
21239 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21240 additional items of information as specially named registers:
21245 Counts clock-ticks in the simulator.
21248 Counts instructions run in the simulator.
21251 Execution time in 60ths of a second.
21255 You can refer to these values in @value{GDBN} expressions with the usual
21256 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21257 conditional breakpoint that suspends only after at least 5000
21258 simulated clock ticks.
21261 @subsection Atmel AVR
21264 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21265 following AVR-specific commands:
21268 @item info io_registers
21269 @kindex info io_registers@r{, AVR}
21270 @cindex I/O registers (Atmel AVR)
21271 This command displays information about the AVR I/O registers. For
21272 each register, @value{GDBN} prints its number and value.
21279 When configured for debugging CRIS, @value{GDBN} provides the
21280 following CRIS-specific commands:
21283 @item set cris-version @var{ver}
21284 @cindex CRIS version
21285 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21286 The CRIS version affects register names and sizes. This command is useful in
21287 case autodetection of the CRIS version fails.
21289 @item show cris-version
21290 Show the current CRIS version.
21292 @item set cris-dwarf2-cfi
21293 @cindex DWARF-2 CFI and CRIS
21294 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21295 Change to @samp{off} when using @code{gcc-cris} whose version is below
21298 @item show cris-dwarf2-cfi
21299 Show the current state of using DWARF-2 CFI.
21301 @item set cris-mode @var{mode}
21303 Set the current CRIS mode to @var{mode}. It should only be changed when
21304 debugging in guru mode, in which case it should be set to
21305 @samp{guru} (the default is @samp{normal}).
21307 @item show cris-mode
21308 Show the current CRIS mode.
21312 @subsection Renesas Super-H
21315 For the Renesas Super-H processor, @value{GDBN} provides these
21319 @item set sh calling-convention @var{convention}
21320 @kindex set sh calling-convention
21321 Set the calling-convention used when calling functions from @value{GDBN}.
21322 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21323 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21324 convention. If the DWARF-2 information of the called function specifies
21325 that the function follows the Renesas calling convention, the function
21326 is called using the Renesas calling convention. If the calling convention
21327 is set to @samp{renesas}, the Renesas calling convention is always used,
21328 regardless of the DWARF-2 information. This can be used to override the
21329 default of @samp{gcc} if debug information is missing, or the compiler
21330 does not emit the DWARF-2 calling convention entry for a function.
21332 @item show sh calling-convention
21333 @kindex show sh calling-convention
21334 Show the current calling convention setting.
21339 @node Architectures
21340 @section Architectures
21342 This section describes characteristics of architectures that affect
21343 all uses of @value{GDBN} with the architecture, both native and cross.
21350 * HPPA:: HP PA architecture
21351 * SPU:: Cell Broadband Engine SPU architecture
21357 @subsection AArch64
21358 @cindex AArch64 support
21360 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21361 following special commands:
21364 @item set debug aarch64
21365 @kindex set debug aarch64
21366 This command determines whether AArch64 architecture-specific debugging
21367 messages are to be displayed.
21369 @item show debug aarch64
21370 Show whether AArch64 debugging messages are displayed.
21375 @subsection x86 Architecture-specific Issues
21378 @item set struct-convention @var{mode}
21379 @kindex set struct-convention
21380 @cindex struct return convention
21381 @cindex struct/union returned in registers
21382 Set the convention used by the inferior to return @code{struct}s and
21383 @code{union}s from functions to @var{mode}. Possible values of
21384 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21385 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21386 are returned on the stack, while @code{"reg"} means that a
21387 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21388 be returned in a register.
21390 @item show struct-convention
21391 @kindex show struct-convention
21392 Show the current setting of the convention to return @code{struct}s
21396 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21397 @cindex Intel(R) Memory Protection Extensions (MPX).
21399 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21400 @footnote{The register named with capital letters represent the architecture
21401 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21402 which are the lower bound and upper bound. Bounds are effective addresses or
21403 memory locations. The upper bounds are architecturally represented in 1's
21404 complement form. A bound having lower bound = 0, and upper bound = 0
21405 (1's complement of all bits set) will allow access to the entire address space.
21407 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21408 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21409 display the upper bound performing the complement of one operation on the
21410 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21411 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21412 can also be noted that the upper bounds are inclusive.
21414 As an example, assume that the register BND0 holds bounds for a pointer having
21415 access allowed for the range between 0x32 and 0x71. The values present on
21416 bnd0raw and bnd registers are presented as follows:
21419 bnd0raw = @{0x32, 0xffffffff8e@}
21420 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21423 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21424 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21425 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21426 Python, the display includes the memory size, in bits, accessible to
21432 See the following section.
21435 @subsection @acronym{MIPS}
21437 @cindex stack on Alpha
21438 @cindex stack on @acronym{MIPS}
21439 @cindex Alpha stack
21440 @cindex @acronym{MIPS} stack
21441 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21442 sometimes requires @value{GDBN} to search backward in the object code to
21443 find the beginning of a function.
21445 @cindex response time, @acronym{MIPS} debugging
21446 To improve response time (especially for embedded applications, where
21447 @value{GDBN} may be restricted to a slow serial line for this search)
21448 you may want to limit the size of this search, using one of these
21452 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21453 @item set heuristic-fence-post @var{limit}
21454 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21455 search for the beginning of a function. A value of @var{0} (the
21456 default) means there is no limit. However, except for @var{0}, the
21457 larger the limit the more bytes @code{heuristic-fence-post} must search
21458 and therefore the longer it takes to run. You should only need to use
21459 this command when debugging a stripped executable.
21461 @item show heuristic-fence-post
21462 Display the current limit.
21466 These commands are available @emph{only} when @value{GDBN} is configured
21467 for debugging programs on Alpha or @acronym{MIPS} processors.
21469 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21473 @item set mips abi @var{arg}
21474 @kindex set mips abi
21475 @cindex set ABI for @acronym{MIPS}
21476 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21477 values of @var{arg} are:
21481 The default ABI associated with the current binary (this is the
21491 @item show mips abi
21492 @kindex show mips abi
21493 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21495 @item set mips compression @var{arg}
21496 @kindex set mips compression
21497 @cindex code compression, @acronym{MIPS}
21498 Tell @value{GDBN} which @acronym{MIPS} compressed
21499 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21500 inferior. @value{GDBN} uses this for code disassembly and other
21501 internal interpretation purposes. This setting is only referred to
21502 when no executable has been associated with the debugging session or
21503 the executable does not provide information about the encoding it uses.
21504 Otherwise this setting is automatically updated from information
21505 provided by the executable.
21507 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21508 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21509 executables containing @acronym{MIPS16} code frequently are not
21510 identified as such.
21512 This setting is ``sticky''; that is, it retains its value across
21513 debugging sessions until reset either explicitly with this command or
21514 implicitly from an executable.
21516 The compiler and/or assembler typically add symbol table annotations to
21517 identify functions compiled for the @acronym{MIPS16} or
21518 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21519 are present, @value{GDBN} uses them in preference to the global
21520 compressed @acronym{ISA} encoding setting.
21522 @item show mips compression
21523 @kindex show mips compression
21524 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21525 @value{GDBN} to debug the inferior.
21528 @itemx show mipsfpu
21529 @xref{MIPS Embedded, set mipsfpu}.
21531 @item set mips mask-address @var{arg}
21532 @kindex set mips mask-address
21533 @cindex @acronym{MIPS} addresses, masking
21534 This command determines whether the most-significant 32 bits of 64-bit
21535 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21536 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21537 setting, which lets @value{GDBN} determine the correct value.
21539 @item show mips mask-address
21540 @kindex show mips mask-address
21541 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21544 @item set remote-mips64-transfers-32bit-regs
21545 @kindex set remote-mips64-transfers-32bit-regs
21546 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21547 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21548 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21549 and 64 bits for other registers, set this option to @samp{on}.
21551 @item show remote-mips64-transfers-32bit-regs
21552 @kindex show remote-mips64-transfers-32bit-regs
21553 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21555 @item set debug mips
21556 @kindex set debug mips
21557 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21558 target code in @value{GDBN}.
21560 @item show debug mips
21561 @kindex show debug mips
21562 Show the current setting of @acronym{MIPS} debugging messages.
21568 @cindex HPPA support
21570 When @value{GDBN} is debugging the HP PA architecture, it provides the
21571 following special commands:
21574 @item set debug hppa
21575 @kindex set debug hppa
21576 This command determines whether HPPA architecture-specific debugging
21577 messages are to be displayed.
21579 @item show debug hppa
21580 Show whether HPPA debugging messages are displayed.
21582 @item maint print unwind @var{address}
21583 @kindex maint print unwind@r{, HPPA}
21584 This command displays the contents of the unwind table entry at the
21585 given @var{address}.
21591 @subsection Cell Broadband Engine SPU architecture
21592 @cindex Cell Broadband Engine
21595 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21596 it provides the following special commands:
21599 @item info spu event
21601 Display SPU event facility status. Shows current event mask
21602 and pending event status.
21604 @item info spu signal
21605 Display SPU signal notification facility status. Shows pending
21606 signal-control word and signal notification mode of both signal
21607 notification channels.
21609 @item info spu mailbox
21610 Display SPU mailbox facility status. Shows all pending entries,
21611 in order of processing, in each of the SPU Write Outbound,
21612 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21615 Display MFC DMA status. Shows all pending commands in the MFC
21616 DMA queue. For each entry, opcode, tag, class IDs, effective
21617 and local store addresses and transfer size are shown.
21619 @item info spu proxydma
21620 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21621 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21622 and local store addresses and transfer size are shown.
21626 When @value{GDBN} is debugging a combined PowerPC/SPU application
21627 on the Cell Broadband Engine, it provides in addition the following
21631 @item set spu stop-on-load @var{arg}
21633 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21634 will give control to the user when a new SPE thread enters its @code{main}
21635 function. The default is @code{off}.
21637 @item show spu stop-on-load
21639 Show whether to stop for new SPE threads.
21641 @item set spu auto-flush-cache @var{arg}
21642 Set whether to automatically flush the software-managed cache. When set to
21643 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21644 cache to be flushed whenever SPE execution stops. This provides a consistent
21645 view of PowerPC memory that is accessed via the cache. If an application
21646 does not use the software-managed cache, this option has no effect.
21648 @item show spu auto-flush-cache
21649 Show whether to automatically flush the software-managed cache.
21654 @subsection PowerPC
21655 @cindex PowerPC architecture
21657 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21658 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21659 numbers stored in the floating point registers. These values must be stored
21660 in two consecutive registers, always starting at an even register like
21661 @code{f0} or @code{f2}.
21663 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21664 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21665 @code{f2} and @code{f3} for @code{$dl1} and so on.
21667 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21668 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21671 @subsection Nios II
21672 @cindex Nios II architecture
21674 When @value{GDBN} is debugging the Nios II architecture,
21675 it provides the following special commands:
21679 @item set debug nios2
21680 @kindex set debug nios2
21681 This command turns on and off debugging messages for the Nios II
21682 target code in @value{GDBN}.
21684 @item show debug nios2
21685 @kindex show debug nios2
21686 Show the current setting of Nios II debugging messages.
21689 @node Controlling GDB
21690 @chapter Controlling @value{GDBN}
21692 You can alter the way @value{GDBN} interacts with you by using the
21693 @code{set} command. For commands controlling how @value{GDBN} displays
21694 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21699 * Editing:: Command editing
21700 * Command History:: Command history
21701 * Screen Size:: Screen size
21702 * Numbers:: Numbers
21703 * ABI:: Configuring the current ABI
21704 * Auto-loading:: Automatically loading associated files
21705 * Messages/Warnings:: Optional warnings and messages
21706 * Debugging Output:: Optional messages about internal happenings
21707 * Other Misc Settings:: Other Miscellaneous Settings
21715 @value{GDBN} indicates its readiness to read a command by printing a string
21716 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21717 can change the prompt string with the @code{set prompt} command. For
21718 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21719 the prompt in one of the @value{GDBN} sessions so that you can always tell
21720 which one you are talking to.
21722 @emph{Note:} @code{set prompt} does not add a space for you after the
21723 prompt you set. This allows you to set a prompt which ends in a space
21724 or a prompt that does not.
21728 @item set prompt @var{newprompt}
21729 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21731 @kindex show prompt
21733 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21736 Versions of @value{GDBN} that ship with Python scripting enabled have
21737 prompt extensions. The commands for interacting with these extensions
21741 @kindex set extended-prompt
21742 @item set extended-prompt @var{prompt}
21743 Set an extended prompt that allows for substitutions.
21744 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21745 substitution. Any escape sequences specified as part of the prompt
21746 string are replaced with the corresponding strings each time the prompt
21752 set extended-prompt Current working directory: \w (gdb)
21755 Note that when an extended-prompt is set, it takes control of the
21756 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21758 @kindex show extended-prompt
21759 @item show extended-prompt
21760 Prints the extended prompt. Any escape sequences specified as part of
21761 the prompt string with @code{set extended-prompt}, are replaced with the
21762 corresponding strings each time the prompt is displayed.
21766 @section Command Editing
21768 @cindex command line editing
21770 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21771 @sc{gnu} library provides consistent behavior for programs which provide a
21772 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21773 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21774 substitution, and a storage and recall of command history across
21775 debugging sessions.
21777 You may control the behavior of command line editing in @value{GDBN} with the
21778 command @code{set}.
21781 @kindex set editing
21784 @itemx set editing on
21785 Enable command line editing (enabled by default).
21787 @item set editing off
21788 Disable command line editing.
21790 @kindex show editing
21792 Show whether command line editing is enabled.
21795 @ifset SYSTEM_READLINE
21796 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21798 @ifclear SYSTEM_READLINE
21799 @xref{Command Line Editing},
21801 for more details about the Readline
21802 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21803 encouraged to read that chapter.
21805 @node Command History
21806 @section Command History
21807 @cindex command history
21809 @value{GDBN} can keep track of the commands you type during your
21810 debugging sessions, so that you can be certain of precisely what
21811 happened. Use these commands to manage the @value{GDBN} command
21814 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21815 package, to provide the history facility.
21816 @ifset SYSTEM_READLINE
21817 @xref{Using History Interactively, , , history, GNU History Library},
21819 @ifclear SYSTEM_READLINE
21820 @xref{Using History Interactively},
21822 for the detailed description of the History library.
21824 To issue a command to @value{GDBN} without affecting certain aspects of
21825 the state which is seen by users, prefix it with @samp{server }
21826 (@pxref{Server Prefix}). This
21827 means that this command will not affect the command history, nor will it
21828 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21829 pressed on a line by itself.
21831 @cindex @code{server}, command prefix
21832 The server prefix does not affect the recording of values into the value
21833 history; to print a value without recording it into the value history,
21834 use the @code{output} command instead of the @code{print} command.
21836 Here is the description of @value{GDBN} commands related to command
21840 @cindex history substitution
21841 @cindex history file
21842 @kindex set history filename
21843 @cindex @env{GDBHISTFILE}, environment variable
21844 @item set history filename @var{fname}
21845 Set the name of the @value{GDBN} command history file to @var{fname}.
21846 This is the file where @value{GDBN} reads an initial command history
21847 list, and where it writes the command history from this session when it
21848 exits. You can access this list through history expansion or through
21849 the history command editing characters listed below. This file defaults
21850 to the value of the environment variable @code{GDBHISTFILE}, or to
21851 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21854 @cindex save command history
21855 @kindex set history save
21856 @item set history save
21857 @itemx set history save on
21858 Record command history in a file, whose name may be specified with the
21859 @code{set history filename} command. By default, this option is disabled.
21861 @item set history save off
21862 Stop recording command history in a file.
21864 @cindex history size
21865 @kindex set history size
21866 @cindex @env{HISTSIZE}, environment variable
21867 @item set history size @var{size}
21868 @itemx set history size unlimited
21869 Set the number of commands which @value{GDBN} keeps in its history list.
21870 This defaults to the value of the environment variable
21871 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21872 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21873 history list is unlimited.
21876 History expansion assigns special meaning to the character @kbd{!}.
21877 @ifset SYSTEM_READLINE
21878 @xref{Event Designators, , , history, GNU History Library},
21880 @ifclear SYSTEM_READLINE
21881 @xref{Event Designators},
21885 @cindex history expansion, turn on/off
21886 Since @kbd{!} is also the logical not operator in C, history expansion
21887 is off by default. If you decide to enable history expansion with the
21888 @code{set history expansion on} command, you may sometimes need to
21889 follow @kbd{!} (when it is used as logical not, in an expression) with
21890 a space or a tab to prevent it from being expanded. The readline
21891 history facilities do not attempt substitution on the strings
21892 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21894 The commands to control history expansion are:
21897 @item set history expansion on
21898 @itemx set history expansion
21899 @kindex set history expansion
21900 Enable history expansion. History expansion is off by default.
21902 @item set history expansion off
21903 Disable history expansion.
21906 @kindex show history
21908 @itemx show history filename
21909 @itemx show history save
21910 @itemx show history size
21911 @itemx show history expansion
21912 These commands display the state of the @value{GDBN} history parameters.
21913 @code{show history} by itself displays all four states.
21918 @kindex show commands
21919 @cindex show last commands
21920 @cindex display command history
21921 @item show commands
21922 Display the last ten commands in the command history.
21924 @item show commands @var{n}
21925 Print ten commands centered on command number @var{n}.
21927 @item show commands +
21928 Print ten commands just after the commands last printed.
21932 @section Screen Size
21933 @cindex size of screen
21934 @cindex pauses in output
21936 Certain commands to @value{GDBN} may produce large amounts of
21937 information output to the screen. To help you read all of it,
21938 @value{GDBN} pauses and asks you for input at the end of each page of
21939 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21940 to discard the remaining output. Also, the screen width setting
21941 determines when to wrap lines of output. Depending on what is being
21942 printed, @value{GDBN} tries to break the line at a readable place,
21943 rather than simply letting it overflow onto the following line.
21945 Normally @value{GDBN} knows the size of the screen from the terminal
21946 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21947 together with the value of the @code{TERM} environment variable and the
21948 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21949 you can override it with the @code{set height} and @code{set
21956 @kindex show height
21957 @item set height @var{lpp}
21958 @itemx set height unlimited
21960 @itemx set width @var{cpl}
21961 @itemx set width unlimited
21963 These @code{set} commands specify a screen height of @var{lpp} lines and
21964 a screen width of @var{cpl} characters. The associated @code{show}
21965 commands display the current settings.
21967 If you specify a height of either @code{unlimited} or zero lines,
21968 @value{GDBN} does not pause during output no matter how long the
21969 output is. This is useful if output is to a file or to an editor
21972 Likewise, you can specify @samp{set width unlimited} or @samp{set
21973 width 0} to prevent @value{GDBN} from wrapping its output.
21975 @item set pagination on
21976 @itemx set pagination off
21977 @kindex set pagination
21978 Turn the output pagination on or off; the default is on. Turning
21979 pagination off is the alternative to @code{set height unlimited}. Note that
21980 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21981 Options, -batch}) also automatically disables pagination.
21983 @item show pagination
21984 @kindex show pagination
21985 Show the current pagination mode.
21990 @cindex number representation
21991 @cindex entering numbers
21993 You can always enter numbers in octal, decimal, or hexadecimal in
21994 @value{GDBN} by the usual conventions: octal numbers begin with
21995 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21996 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21997 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21998 10; likewise, the default display for numbers---when no particular
21999 format is specified---is base 10. You can change the default base for
22000 both input and output with the commands described below.
22003 @kindex set input-radix
22004 @item set input-radix @var{base}
22005 Set the default base for numeric input. Supported choices
22006 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22007 specified either unambiguously or using the current input radix; for
22011 set input-radix 012
22012 set input-radix 10.
22013 set input-radix 0xa
22017 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22018 leaves the input radix unchanged, no matter what it was, since
22019 @samp{10}, being without any leading or trailing signs of its base, is
22020 interpreted in the current radix. Thus, if the current radix is 16,
22021 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22024 @kindex set output-radix
22025 @item set output-radix @var{base}
22026 Set the default base for numeric display. Supported choices
22027 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22028 specified either unambiguously or using the current input radix.
22030 @kindex show input-radix
22031 @item show input-radix
22032 Display the current default base for numeric input.
22034 @kindex show output-radix
22035 @item show output-radix
22036 Display the current default base for numeric display.
22038 @item set radix @r{[}@var{base}@r{]}
22042 These commands set and show the default base for both input and output
22043 of numbers. @code{set radix} sets the radix of input and output to
22044 the same base; without an argument, it resets the radix back to its
22045 default value of 10.
22050 @section Configuring the Current ABI
22052 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22053 application automatically. However, sometimes you need to override its
22054 conclusions. Use these commands to manage @value{GDBN}'s view of the
22060 @cindex Newlib OS ABI and its influence on the longjmp handling
22062 One @value{GDBN} configuration can debug binaries for multiple operating
22063 system targets, either via remote debugging or native emulation.
22064 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22065 but you can override its conclusion using the @code{set osabi} command.
22066 One example where this is useful is in debugging of binaries which use
22067 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22068 not have the same identifying marks that the standard C library for your
22071 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22072 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22073 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22074 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22078 Show the OS ABI currently in use.
22081 With no argument, show the list of registered available OS ABI's.
22083 @item set osabi @var{abi}
22084 Set the current OS ABI to @var{abi}.
22087 @cindex float promotion
22089 Generally, the way that an argument of type @code{float} is passed to a
22090 function depends on whether the function is prototyped. For a prototyped
22091 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22092 according to the architecture's convention for @code{float}. For unprototyped
22093 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22094 @code{double} and then passed.
22096 Unfortunately, some forms of debug information do not reliably indicate whether
22097 a function is prototyped. If @value{GDBN} calls a function that is not marked
22098 as prototyped, it consults @kbd{set coerce-float-to-double}.
22101 @kindex set coerce-float-to-double
22102 @item set coerce-float-to-double
22103 @itemx set coerce-float-to-double on
22104 Arguments of type @code{float} will be promoted to @code{double} when passed
22105 to an unprototyped function. This is the default setting.
22107 @item set coerce-float-to-double off
22108 Arguments of type @code{float} will be passed directly to unprototyped
22111 @kindex show coerce-float-to-double
22112 @item show coerce-float-to-double
22113 Show the current setting of promoting @code{float} to @code{double}.
22117 @kindex show cp-abi
22118 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22119 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22120 used to build your application. @value{GDBN} only fully supports
22121 programs with a single C@t{++} ABI; if your program contains code using
22122 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22123 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22124 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22125 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22126 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22127 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22132 Show the C@t{++} ABI currently in use.
22135 With no argument, show the list of supported C@t{++} ABI's.
22137 @item set cp-abi @var{abi}
22138 @itemx set cp-abi auto
22139 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22143 @section Automatically loading associated files
22144 @cindex auto-loading
22146 @value{GDBN} sometimes reads files with commands and settings automatically,
22147 without being explicitly told so by the user. We call this feature
22148 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22149 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22150 results or introduce security risks (e.g., if the file comes from untrusted
22154 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22155 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22157 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22158 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22161 There are various kinds of files @value{GDBN} can automatically load.
22162 In addition to these files, @value{GDBN} supports auto-loading code written
22163 in various extension languages. @xref{Auto-loading extensions}.
22165 Note that loading of these associated files (including the local @file{.gdbinit}
22166 file) requires accordingly configured @code{auto-load safe-path}
22167 (@pxref{Auto-loading safe path}).
22169 For these reasons, @value{GDBN} includes commands and options to let you
22170 control when to auto-load files and which files should be auto-loaded.
22173 @anchor{set auto-load off}
22174 @kindex set auto-load off
22175 @item set auto-load off
22176 Globally disable loading of all auto-loaded files.
22177 You may want to use this command with the @samp{-iex} option
22178 (@pxref{Option -init-eval-command}) such as:
22180 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22183 Be aware that system init file (@pxref{System-wide configuration})
22184 and init files from your home directory (@pxref{Home Directory Init File})
22185 still get read (as they come from generally trusted directories).
22186 To prevent @value{GDBN} from auto-loading even those init files, use the
22187 @option{-nx} option (@pxref{Mode Options}), in addition to
22188 @code{set auto-load no}.
22190 @anchor{show auto-load}
22191 @kindex show auto-load
22192 @item show auto-load
22193 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22197 (gdb) show auto-load
22198 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22199 libthread-db: Auto-loading of inferior specific libthread_db is on.
22200 local-gdbinit: Auto-loading of .gdbinit script from current directory
22202 python-scripts: Auto-loading of Python scripts is on.
22203 safe-path: List of directories from which it is safe to auto-load files
22204 is $debugdir:$datadir/auto-load.
22205 scripts-directory: List of directories from which to load auto-loaded scripts
22206 is $debugdir:$datadir/auto-load.
22209 @anchor{info auto-load}
22210 @kindex info auto-load
22211 @item info auto-load
22212 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22216 (gdb) info auto-load
22219 Yes /home/user/gdb/gdb-gdb.gdb
22220 libthread-db: No auto-loaded libthread-db.
22221 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22225 Yes /home/user/gdb/gdb-gdb.py
22229 These are @value{GDBN} control commands for the auto-loading:
22231 @multitable @columnfractions .5 .5
22232 @item @xref{set auto-load off}.
22233 @tab Disable auto-loading globally.
22234 @item @xref{show auto-load}.
22235 @tab Show setting of all kinds of files.
22236 @item @xref{info auto-load}.
22237 @tab Show state of all kinds of files.
22238 @item @xref{set auto-load gdb-scripts}.
22239 @tab Control for @value{GDBN} command scripts.
22240 @item @xref{show auto-load gdb-scripts}.
22241 @tab Show setting of @value{GDBN} command scripts.
22242 @item @xref{info auto-load gdb-scripts}.
22243 @tab Show state of @value{GDBN} command scripts.
22244 @item @xref{set auto-load python-scripts}.
22245 @tab Control for @value{GDBN} Python scripts.
22246 @item @xref{show auto-load python-scripts}.
22247 @tab Show setting of @value{GDBN} Python scripts.
22248 @item @xref{info auto-load python-scripts}.
22249 @tab Show state of @value{GDBN} Python scripts.
22250 @item @xref{set auto-load scripts-directory}.
22251 @tab Control for @value{GDBN} auto-loaded scripts location.
22252 @item @xref{show auto-load scripts-directory}.
22253 @tab Show @value{GDBN} auto-loaded scripts location.
22254 @item @xref{set auto-load local-gdbinit}.
22255 @tab Control for init file in the current directory.
22256 @item @xref{show auto-load local-gdbinit}.
22257 @tab Show setting of init file in the current directory.
22258 @item @xref{info auto-load local-gdbinit}.
22259 @tab Show state of init file in the current directory.
22260 @item @xref{set auto-load libthread-db}.
22261 @tab Control for thread debugging library.
22262 @item @xref{show auto-load libthread-db}.
22263 @tab Show setting of thread debugging library.
22264 @item @xref{info auto-load libthread-db}.
22265 @tab Show state of thread debugging library.
22266 @item @xref{set auto-load safe-path}.
22267 @tab Control directories trusted for automatic loading.
22268 @item @xref{show auto-load safe-path}.
22269 @tab Show directories trusted for automatic loading.
22270 @item @xref{add-auto-load-safe-path}.
22271 @tab Add directory trusted for automatic loading.
22274 @node Init File in the Current Directory
22275 @subsection Automatically loading init file in the current directory
22276 @cindex auto-loading init file in the current directory
22278 By default, @value{GDBN} reads and executes the canned sequences of commands
22279 from init file (if any) in the current working directory,
22280 see @ref{Init File in the Current Directory during Startup}.
22282 Note that loading of this local @file{.gdbinit} file also requires accordingly
22283 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22286 @anchor{set auto-load local-gdbinit}
22287 @kindex set auto-load local-gdbinit
22288 @item set auto-load local-gdbinit [on|off]
22289 Enable or disable the auto-loading of canned sequences of commands
22290 (@pxref{Sequences}) found in init file in the current directory.
22292 @anchor{show auto-load local-gdbinit}
22293 @kindex show auto-load local-gdbinit
22294 @item show auto-load local-gdbinit
22295 Show whether auto-loading of canned sequences of commands from init file in the
22296 current directory is enabled or disabled.
22298 @anchor{info auto-load local-gdbinit}
22299 @kindex info auto-load local-gdbinit
22300 @item info auto-load local-gdbinit
22301 Print whether canned sequences of commands from init file in the
22302 current directory have been auto-loaded.
22305 @node libthread_db.so.1 file
22306 @subsection Automatically loading thread debugging library
22307 @cindex auto-loading libthread_db.so.1
22309 This feature is currently present only on @sc{gnu}/Linux native hosts.
22311 @value{GDBN} reads in some cases thread debugging library from places specific
22312 to the inferior (@pxref{set libthread-db-search-path}).
22314 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22315 without checking this @samp{set auto-load libthread-db} switch as system
22316 libraries have to be trusted in general. In all other cases of
22317 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22318 auto-load libthread-db} is enabled before trying to open such thread debugging
22321 Note that loading of this debugging library also requires accordingly configured
22322 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22325 @anchor{set auto-load libthread-db}
22326 @kindex set auto-load libthread-db
22327 @item set auto-load libthread-db [on|off]
22328 Enable or disable the auto-loading of inferior specific thread debugging library.
22330 @anchor{show auto-load libthread-db}
22331 @kindex show auto-load libthread-db
22332 @item show auto-load libthread-db
22333 Show whether auto-loading of inferior specific thread debugging library is
22334 enabled or disabled.
22336 @anchor{info auto-load libthread-db}
22337 @kindex info auto-load libthread-db
22338 @item info auto-load libthread-db
22339 Print the list of all loaded inferior specific thread debugging libraries and
22340 for each such library print list of inferior @var{pid}s using it.
22343 @node Auto-loading safe path
22344 @subsection Security restriction for auto-loading
22345 @cindex auto-loading safe-path
22347 As the files of inferior can come from untrusted source (such as submitted by
22348 an application user) @value{GDBN} does not always load any files automatically.
22349 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22350 directories trusted for loading files not explicitly requested by user.
22351 Each directory can also be a shell wildcard pattern.
22353 If the path is not set properly you will see a warning and the file will not
22358 Reading symbols from /home/user/gdb/gdb...done.
22359 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22360 declined by your `auto-load safe-path' set
22361 to "$debugdir:$datadir/auto-load".
22362 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22363 declined by your `auto-load safe-path' set
22364 to "$debugdir:$datadir/auto-load".
22368 To instruct @value{GDBN} to go ahead and use the init files anyway,
22369 invoke @value{GDBN} like this:
22372 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22375 The list of trusted directories is controlled by the following commands:
22378 @anchor{set auto-load safe-path}
22379 @kindex set auto-load safe-path
22380 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22381 Set the list of directories (and their subdirectories) trusted for automatic
22382 loading and execution of scripts. You can also enter a specific trusted file.
22383 Each directory can also be a shell wildcard pattern; wildcards do not match
22384 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22385 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22386 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22387 its default value as specified during @value{GDBN} compilation.
22389 The list of directories uses path separator (@samp{:} on GNU and Unix
22390 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22391 to the @env{PATH} environment variable.
22393 @anchor{show auto-load safe-path}
22394 @kindex show auto-load safe-path
22395 @item show auto-load safe-path
22396 Show the list of directories trusted for automatic loading and execution of
22399 @anchor{add-auto-load-safe-path}
22400 @kindex add-auto-load-safe-path
22401 @item add-auto-load-safe-path
22402 Add an entry (or list of entries) the list of directories trusted for automatic
22403 loading and execution of scripts. Multiple entries may be delimited by the
22404 host platform path separator in use.
22407 This variable defaults to what @code{--with-auto-load-dir} has been configured
22408 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22409 substitution applies the same as for @ref{set auto-load scripts-directory}.
22410 The default @code{set auto-load safe-path} value can be also overriden by
22411 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22413 Setting this variable to @file{/} disables this security protection,
22414 corresponding @value{GDBN} configuration option is
22415 @option{--without-auto-load-safe-path}.
22416 This variable is supposed to be set to the system directories writable by the
22417 system superuser only. Users can add their source directories in init files in
22418 their home directories (@pxref{Home Directory Init File}). See also deprecated
22419 init file in the current directory
22420 (@pxref{Init File in the Current Directory during Startup}).
22422 To force @value{GDBN} to load the files it declined to load in the previous
22423 example, you could use one of the following ways:
22426 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22427 Specify this trusted directory (or a file) as additional component of the list.
22428 You have to specify also any existing directories displayed by
22429 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22431 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22432 Specify this directory as in the previous case but just for a single
22433 @value{GDBN} session.
22435 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22436 Disable auto-loading safety for a single @value{GDBN} session.
22437 This assumes all the files you debug during this @value{GDBN} session will come
22438 from trusted sources.
22440 @item @kbd{./configure --without-auto-load-safe-path}
22441 During compilation of @value{GDBN} you may disable any auto-loading safety.
22442 This assumes all the files you will ever debug with this @value{GDBN} come from
22446 On the other hand you can also explicitly forbid automatic files loading which
22447 also suppresses any such warning messages:
22450 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22451 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22453 @item @file{~/.gdbinit}: @samp{set auto-load no}
22454 Disable auto-loading globally for the user
22455 (@pxref{Home Directory Init File}). While it is improbable, you could also
22456 use system init file instead (@pxref{System-wide configuration}).
22459 This setting applies to the file names as entered by user. If no entry matches
22460 @value{GDBN} tries as a last resort to also resolve all the file names into
22461 their canonical form (typically resolving symbolic links) and compare the
22462 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22463 own before starting the comparison so a canonical form of directories is
22464 recommended to be entered.
22466 @node Auto-loading verbose mode
22467 @subsection Displaying files tried for auto-load
22468 @cindex auto-loading verbose mode
22470 For better visibility of all the file locations where you can place scripts to
22471 be auto-loaded with inferior --- or to protect yourself against accidental
22472 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22473 all the files attempted to be loaded. Both existing and non-existing files may
22476 For example the list of directories from which it is safe to auto-load files
22477 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22478 may not be too obvious while setting it up.
22481 (gdb) set debug auto-load on
22482 (gdb) file ~/src/t/true
22483 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22484 for objfile "/tmp/true".
22485 auto-load: Updating directories of "/usr:/opt".
22486 auto-load: Using directory "/usr".
22487 auto-load: Using directory "/opt".
22488 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22489 by your `auto-load safe-path' set to "/usr:/opt".
22493 @anchor{set debug auto-load}
22494 @kindex set debug auto-load
22495 @item set debug auto-load [on|off]
22496 Set whether to print the filenames attempted to be auto-loaded.
22498 @anchor{show debug auto-load}
22499 @kindex show debug auto-load
22500 @item show debug auto-load
22501 Show whether printing of the filenames attempted to be auto-loaded is turned
22505 @node Messages/Warnings
22506 @section Optional Warnings and Messages
22508 @cindex verbose operation
22509 @cindex optional warnings
22510 By default, @value{GDBN} is silent about its inner workings. If you are
22511 running on a slow machine, you may want to use the @code{set verbose}
22512 command. This makes @value{GDBN} tell you when it does a lengthy
22513 internal operation, so you will not think it has crashed.
22515 Currently, the messages controlled by @code{set verbose} are those
22516 which announce that the symbol table for a source file is being read;
22517 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22520 @kindex set verbose
22521 @item set verbose on
22522 Enables @value{GDBN} output of certain informational messages.
22524 @item set verbose off
22525 Disables @value{GDBN} output of certain informational messages.
22527 @kindex show verbose
22529 Displays whether @code{set verbose} is on or off.
22532 By default, if @value{GDBN} encounters bugs in the symbol table of an
22533 object file, it is silent; but if you are debugging a compiler, you may
22534 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22539 @kindex set complaints
22540 @item set complaints @var{limit}
22541 Permits @value{GDBN} to output @var{limit} complaints about each type of
22542 unusual symbols before becoming silent about the problem. Set
22543 @var{limit} to zero to suppress all complaints; set it to a large number
22544 to prevent complaints from being suppressed.
22546 @kindex show complaints
22547 @item show complaints
22548 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22552 @anchor{confirmation requests}
22553 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22554 lot of stupid questions to confirm certain commands. For example, if
22555 you try to run a program which is already running:
22559 The program being debugged has been started already.
22560 Start it from the beginning? (y or n)
22563 If you are willing to unflinchingly face the consequences of your own
22564 commands, you can disable this ``feature'':
22568 @kindex set confirm
22570 @cindex confirmation
22571 @cindex stupid questions
22572 @item set confirm off
22573 Disables confirmation requests. Note that running @value{GDBN} with
22574 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22575 automatically disables confirmation requests.
22577 @item set confirm on
22578 Enables confirmation requests (the default).
22580 @kindex show confirm
22582 Displays state of confirmation requests.
22586 @cindex command tracing
22587 If you need to debug user-defined commands or sourced files you may find it
22588 useful to enable @dfn{command tracing}. In this mode each command will be
22589 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22590 quantity denoting the call depth of each command.
22593 @kindex set trace-commands
22594 @cindex command scripts, debugging
22595 @item set trace-commands on
22596 Enable command tracing.
22597 @item set trace-commands off
22598 Disable command tracing.
22599 @item show trace-commands
22600 Display the current state of command tracing.
22603 @node Debugging Output
22604 @section Optional Messages about Internal Happenings
22605 @cindex optional debugging messages
22607 @value{GDBN} has commands that enable optional debugging messages from
22608 various @value{GDBN} subsystems; normally these commands are of
22609 interest to @value{GDBN} maintainers, or when reporting a bug. This
22610 section documents those commands.
22613 @kindex set exec-done-display
22614 @item set exec-done-display
22615 Turns on or off the notification of asynchronous commands'
22616 completion. When on, @value{GDBN} will print a message when an
22617 asynchronous command finishes its execution. The default is off.
22618 @kindex show exec-done-display
22619 @item show exec-done-display
22620 Displays the current setting of asynchronous command completion
22623 @cindex ARM AArch64
22624 @item set debug aarch64
22625 Turns on or off display of debugging messages related to ARM AArch64.
22626 The default is off.
22628 @item show debug aarch64
22629 Displays the current state of displaying debugging messages related to
22631 @cindex gdbarch debugging info
22632 @cindex architecture debugging info
22633 @item set debug arch
22634 Turns on or off display of gdbarch debugging info. The default is off
22635 @item show debug arch
22636 Displays the current state of displaying gdbarch debugging info.
22637 @item set debug aix-solib
22638 @cindex AIX shared library debugging
22639 Control display of debugging messages from the AIX shared library
22640 support module. The default is off.
22641 @item show debug aix-thread
22642 Show the current state of displaying AIX shared library debugging messages.
22643 @item set debug aix-thread
22644 @cindex AIX threads
22645 Display debugging messages about inner workings of the AIX thread
22647 @item show debug aix-thread
22648 Show the current state of AIX thread debugging info display.
22649 @item set debug check-physname
22651 Check the results of the ``physname'' computation. When reading DWARF
22652 debugging information for C@t{++}, @value{GDBN} attempts to compute
22653 each entity's name. @value{GDBN} can do this computation in two
22654 different ways, depending on exactly what information is present.
22655 When enabled, this setting causes @value{GDBN} to compute the names
22656 both ways and display any discrepancies.
22657 @item show debug check-physname
22658 Show the current state of ``physname'' checking.
22659 @item set debug coff-pe-read
22660 @cindex COFF/PE exported symbols
22661 Control display of debugging messages related to reading of COFF/PE
22662 exported symbols. The default is off.
22663 @item show debug coff-pe-read
22664 Displays the current state of displaying debugging messages related to
22665 reading of COFF/PE exported symbols.
22666 @item set debug dwarf2-die
22667 @cindex DWARF2 DIEs
22668 Dump DWARF2 DIEs after they are read in.
22669 The value is the number of nesting levels to print.
22670 A value of zero turns off the display.
22671 @item show debug dwarf2-die
22672 Show the current state of DWARF2 DIE debugging.
22673 @item set debug dwarf2-read
22674 @cindex DWARF2 Reading
22675 Turns on or off display of debugging messages related to reading
22676 DWARF debug info. The default is 0 (off).
22677 A value of 1 provides basic information.
22678 A value greater than 1 provides more verbose information.
22679 @item show debug dwarf2-read
22680 Show the current state of DWARF2 reader debugging.
22681 @item set debug displaced
22682 @cindex displaced stepping debugging info
22683 Turns on or off display of @value{GDBN} debugging info for the
22684 displaced stepping support. The default is off.
22685 @item show debug displaced
22686 Displays the current state of displaying @value{GDBN} debugging info
22687 related to displaced stepping.
22688 @item set debug event
22689 @cindex event debugging info
22690 Turns on or off display of @value{GDBN} event debugging info. The
22692 @item show debug event
22693 Displays the current state of displaying @value{GDBN} event debugging
22695 @item set debug expression
22696 @cindex expression debugging info
22697 Turns on or off display of debugging info about @value{GDBN}
22698 expression parsing. The default is off.
22699 @item show debug expression
22700 Displays the current state of displaying debugging info about
22701 @value{GDBN} expression parsing.
22702 @item set debug frame
22703 @cindex frame debugging info
22704 Turns on or off display of @value{GDBN} frame debugging info. The
22706 @item show debug frame
22707 Displays the current state of displaying @value{GDBN} frame debugging
22709 @item set debug gnu-nat
22710 @cindex @sc{gnu}/Hurd debug messages
22711 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22712 @item show debug gnu-nat
22713 Show the current state of @sc{gnu}/Hurd debugging messages.
22714 @item set debug infrun
22715 @cindex inferior debugging info
22716 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22717 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22718 for implementing operations such as single-stepping the inferior.
22719 @item show debug infrun
22720 Displays the current state of @value{GDBN} inferior debugging.
22721 @item set debug jit
22722 @cindex just-in-time compilation, debugging messages
22723 Turns on or off debugging messages from JIT debug support.
22724 @item show debug jit
22725 Displays the current state of @value{GDBN} JIT debugging.
22726 @item set debug lin-lwp
22727 @cindex @sc{gnu}/Linux LWP debug messages
22728 @cindex Linux lightweight processes
22729 Turns on or off debugging messages from the Linux LWP debug support.
22730 @item show debug lin-lwp
22731 Show the current state of Linux LWP debugging messages.
22732 @item set debug mach-o
22733 @cindex Mach-O symbols processing
22734 Control display of debugging messages related to Mach-O symbols
22735 processing. The default is off.
22736 @item show debug mach-o
22737 Displays the current state of displaying debugging messages related to
22738 reading of COFF/PE exported symbols.
22739 @item set debug notification
22740 @cindex remote async notification debugging info
22741 Turns on or off debugging messages about remote async notification.
22742 The default is off.
22743 @item show debug notification
22744 Displays the current state of remote async notification debugging messages.
22745 @item set debug observer
22746 @cindex observer debugging info
22747 Turns on or off display of @value{GDBN} observer debugging. This
22748 includes info such as the notification of observable events.
22749 @item show debug observer
22750 Displays the current state of observer debugging.
22751 @item set debug overload
22752 @cindex C@t{++} overload debugging info
22753 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22754 info. This includes info such as ranking of functions, etc. The default
22756 @item show debug overload
22757 Displays the current state of displaying @value{GDBN} C@t{++} overload
22759 @cindex expression parser, debugging info
22760 @cindex debug expression parser
22761 @item set debug parser
22762 Turns on or off the display of expression parser debugging output.
22763 Internally, this sets the @code{yydebug} variable in the expression
22764 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22765 details. The default is off.
22766 @item show debug parser
22767 Show the current state of expression parser debugging.
22768 @cindex packets, reporting on stdout
22769 @cindex serial connections, debugging
22770 @cindex debug remote protocol
22771 @cindex remote protocol debugging
22772 @cindex display remote packets
22773 @item set debug remote
22774 Turns on or off display of reports on all packets sent back and forth across
22775 the serial line to the remote machine. The info is printed on the
22776 @value{GDBN} standard output stream. The default is off.
22777 @item show debug remote
22778 Displays the state of display of remote packets.
22779 @item set debug serial
22780 Turns on or off display of @value{GDBN} serial debugging info. The
22782 @item show debug serial
22783 Displays the current state of displaying @value{GDBN} serial debugging
22785 @item set debug solib-frv
22786 @cindex FR-V shared-library debugging
22787 Turns on or off debugging messages for FR-V shared-library code.
22788 @item show debug solib-frv
22789 Display the current state of FR-V shared-library code debugging
22791 @item set debug symfile
22792 @cindex symbol file functions
22793 Turns on or off display of debugging messages related to symbol file functions.
22794 The default is off. @xref{Files}.
22795 @item show debug symfile
22796 Show the current state of symbol file debugging messages.
22797 @item set debug symtab-create
22798 @cindex symbol table creation
22799 Turns on or off display of debugging messages related to symbol table creation.
22800 The default is 0 (off).
22801 A value of 1 provides basic information.
22802 A value greater than 1 provides more verbose information.
22803 @item show debug symtab-create
22804 Show the current state of symbol table creation debugging.
22805 @item set debug target
22806 @cindex target debugging info
22807 Turns on or off display of @value{GDBN} target debugging info. This info
22808 includes what is going on at the target level of GDB, as it happens. The
22809 default is 0. Set it to 1 to track events, and to 2 to also track the
22810 value of large memory transfers. Changes to this flag do not take effect
22811 until the next time you connect to a target or use the @code{run} command.
22812 @item show debug target
22813 Displays the current state of displaying @value{GDBN} target debugging
22815 @item set debug timestamp
22816 @cindex timestampping debugging info
22817 Turns on or off display of timestamps with @value{GDBN} debugging info.
22818 When enabled, seconds and microseconds are displayed before each debugging
22820 @item show debug timestamp
22821 Displays the current state of displaying timestamps with @value{GDBN}
22823 @item set debugvarobj
22824 @cindex variable object debugging info
22825 Turns on or off display of @value{GDBN} variable object debugging
22826 info. The default is off.
22827 @item show debugvarobj
22828 Displays the current state of displaying @value{GDBN} variable object
22830 @item set debug xml
22831 @cindex XML parser debugging
22832 Turns on or off debugging messages for built-in XML parsers.
22833 @item show debug xml
22834 Displays the current state of XML debugging messages.
22837 @node Other Misc Settings
22838 @section Other Miscellaneous Settings
22839 @cindex miscellaneous settings
22842 @kindex set interactive-mode
22843 @item set interactive-mode
22844 If @code{on}, forces @value{GDBN} to assume that GDB was started
22845 in a terminal. In practice, this means that @value{GDBN} should wait
22846 for the user to answer queries generated by commands entered at
22847 the command prompt. If @code{off}, forces @value{GDBN} to operate
22848 in the opposite mode, and it uses the default answers to all queries.
22849 If @code{auto} (the default), @value{GDBN} tries to determine whether
22850 its standard input is a terminal, and works in interactive-mode if it
22851 is, non-interactively otherwise.
22853 In the vast majority of cases, the debugger should be able to guess
22854 correctly which mode should be used. But this setting can be useful
22855 in certain specific cases, such as running a MinGW @value{GDBN}
22856 inside a cygwin window.
22858 @kindex show interactive-mode
22859 @item show interactive-mode
22860 Displays whether the debugger is operating in interactive mode or not.
22863 @node Extending GDB
22864 @chapter Extending @value{GDBN}
22865 @cindex extending GDB
22867 @value{GDBN} provides several mechanisms for extension.
22868 @value{GDBN} also provides the ability to automatically load
22869 extensions when it reads a file for debugging. This allows the
22870 user to automatically customize @value{GDBN} for the program
22874 * Sequences:: Canned Sequences of @value{GDBN} Commands
22875 * Python:: Extending @value{GDBN} using Python
22876 * Auto-loading extensions:: Automatically loading extensions
22877 * Aliases:: Creating new spellings of existing commands
22880 To facilitate the use of extension languages, @value{GDBN} is capable
22881 of evaluating the contents of a file. When doing so, @value{GDBN}
22882 can recognize which extension language is being used by looking at
22883 the filename extension. Files with an unrecognized filename extension
22884 are always treated as a @value{GDBN} Command Files.
22885 @xref{Command Files,, Command files}.
22887 You can control how @value{GDBN} evaluates these files with the following
22891 @kindex set script-extension
22892 @kindex show script-extension
22893 @item set script-extension off
22894 All scripts are always evaluated as @value{GDBN} Command Files.
22896 @item set script-extension soft
22897 The debugger determines the scripting language based on filename
22898 extension. If this scripting language is supported, @value{GDBN}
22899 evaluates the script using that language. Otherwise, it evaluates
22900 the file as a @value{GDBN} Command File.
22902 @item set script-extension strict
22903 The debugger determines the scripting language based on filename
22904 extension, and evaluates the script using that language. If the
22905 language is not supported, then the evaluation fails.
22907 @item show script-extension
22908 Display the current value of the @code{script-extension} option.
22913 @section Canned Sequences of Commands
22915 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22916 Command Lists}), @value{GDBN} provides two ways to store sequences of
22917 commands for execution as a unit: user-defined commands and command
22921 * Define:: How to define your own commands
22922 * Hooks:: Hooks for user-defined commands
22923 * Command Files:: How to write scripts of commands to be stored in a file
22924 * Output:: Commands for controlled output
22925 * Auto-loading sequences:: Controlling auto-loaded command files
22929 @subsection User-defined Commands
22931 @cindex user-defined command
22932 @cindex arguments, to user-defined commands
22933 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22934 which you assign a new name as a command. This is done with the
22935 @code{define} command. User commands may accept up to 10 arguments
22936 separated by whitespace. Arguments are accessed within the user command
22937 via @code{$arg0@dots{}$arg9}. A trivial example:
22941 print $arg0 + $arg1 + $arg2
22946 To execute the command use:
22953 This defines the command @code{adder}, which prints the sum of
22954 its three arguments. Note the arguments are text substitutions, so they may
22955 reference variables, use complex expressions, or even perform inferior
22958 @cindex argument count in user-defined commands
22959 @cindex how many arguments (user-defined commands)
22960 In addition, @code{$argc} may be used to find out how many arguments have
22961 been passed. This expands to a number in the range 0@dots{}10.
22966 print $arg0 + $arg1
22969 print $arg0 + $arg1 + $arg2
22977 @item define @var{commandname}
22978 Define a command named @var{commandname}. If there is already a command
22979 by that name, you are asked to confirm that you want to redefine it.
22980 @var{commandname} may be a bare command name consisting of letters,
22981 numbers, dashes, and underscores. It may also start with any predefined
22982 prefix command. For example, @samp{define target my-target} creates
22983 a user-defined @samp{target my-target} command.
22985 The definition of the command is made up of other @value{GDBN} command lines,
22986 which are given following the @code{define} command. The end of these
22987 commands is marked by a line containing @code{end}.
22990 @kindex end@r{ (user-defined commands)}
22991 @item document @var{commandname}
22992 Document the user-defined command @var{commandname}, so that it can be
22993 accessed by @code{help}. The command @var{commandname} must already be
22994 defined. This command reads lines of documentation just as @code{define}
22995 reads the lines of the command definition, ending with @code{end}.
22996 After the @code{document} command is finished, @code{help} on command
22997 @var{commandname} displays the documentation you have written.
22999 You may use the @code{document} command again to change the
23000 documentation of a command. Redefining the command with @code{define}
23001 does not change the documentation.
23003 @kindex dont-repeat
23004 @cindex don't repeat command
23006 Used inside a user-defined command, this tells @value{GDBN} that this
23007 command should not be repeated when the user hits @key{RET}
23008 (@pxref{Command Syntax, repeat last command}).
23010 @kindex help user-defined
23011 @item help user-defined
23012 List all user-defined commands and all python commands defined in class
23013 COMAND_USER. The first line of the documentation or docstring is
23018 @itemx show user @var{commandname}
23019 Display the @value{GDBN} commands used to define @var{commandname} (but
23020 not its documentation). If no @var{commandname} is given, display the
23021 definitions for all user-defined commands.
23022 This does not work for user-defined python commands.
23024 @cindex infinite recursion in user-defined commands
23025 @kindex show max-user-call-depth
23026 @kindex set max-user-call-depth
23027 @item show max-user-call-depth
23028 @itemx set max-user-call-depth
23029 The value of @code{max-user-call-depth} controls how many recursion
23030 levels are allowed in user-defined commands before @value{GDBN} suspects an
23031 infinite recursion and aborts the command.
23032 This does not apply to user-defined python commands.
23035 In addition to the above commands, user-defined commands frequently
23036 use control flow commands, described in @ref{Command Files}.
23038 When user-defined commands are executed, the
23039 commands of the definition are not printed. An error in any command
23040 stops execution of the user-defined command.
23042 If used interactively, commands that would ask for confirmation proceed
23043 without asking when used inside a user-defined command. Many @value{GDBN}
23044 commands that normally print messages to say what they are doing omit the
23045 messages when used in a user-defined command.
23048 @subsection User-defined Command Hooks
23049 @cindex command hooks
23050 @cindex hooks, for commands
23051 @cindex hooks, pre-command
23054 You may define @dfn{hooks}, which are a special kind of user-defined
23055 command. Whenever you run the command @samp{foo}, if the user-defined
23056 command @samp{hook-foo} exists, it is executed (with no arguments)
23057 before that command.
23059 @cindex hooks, post-command
23061 A hook may also be defined which is run after the command you executed.
23062 Whenever you run the command @samp{foo}, if the user-defined command
23063 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23064 that command. Post-execution hooks may exist simultaneously with
23065 pre-execution hooks, for the same command.
23067 It is valid for a hook to call the command which it hooks. If this
23068 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23070 @c It would be nice if hookpost could be passed a parameter indicating
23071 @c if the command it hooks executed properly or not. FIXME!
23073 @kindex stop@r{, a pseudo-command}
23074 In addition, a pseudo-command, @samp{stop} exists. Defining
23075 (@samp{hook-stop}) makes the associated commands execute every time
23076 execution stops in your program: before breakpoint commands are run,
23077 displays are printed, or the stack frame is printed.
23079 For example, to ignore @code{SIGALRM} signals while
23080 single-stepping, but treat them normally during normal execution,
23085 handle SIGALRM nopass
23089 handle SIGALRM pass
23092 define hook-continue
23093 handle SIGALRM pass
23097 As a further example, to hook at the beginning and end of the @code{echo}
23098 command, and to add extra text to the beginning and end of the message,
23106 define hookpost-echo
23110 (@value{GDBP}) echo Hello World
23111 <<<---Hello World--->>>
23116 You can define a hook for any single-word command in @value{GDBN}, but
23117 not for command aliases; you should define a hook for the basic command
23118 name, e.g.@: @code{backtrace} rather than @code{bt}.
23119 @c FIXME! So how does Joe User discover whether a command is an alias
23121 You can hook a multi-word command by adding @code{hook-} or
23122 @code{hookpost-} to the last word of the command, e.g.@:
23123 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23125 If an error occurs during the execution of your hook, execution of
23126 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23127 (before the command that you actually typed had a chance to run).
23129 If you try to define a hook which does not match any known command, you
23130 get a warning from the @code{define} command.
23132 @node Command Files
23133 @subsection Command Files
23135 @cindex command files
23136 @cindex scripting commands
23137 A command file for @value{GDBN} is a text file made of lines that are
23138 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23139 also be included. An empty line in a command file does nothing; it
23140 does not mean to repeat the last command, as it would from the
23143 You can request the execution of a command file with the @code{source}
23144 command. Note that the @code{source} command is also used to evaluate
23145 scripts that are not Command Files. The exact behavior can be configured
23146 using the @code{script-extension} setting.
23147 @xref{Extending GDB,, Extending GDB}.
23151 @cindex execute commands from a file
23152 @item source [-s] [-v] @var{filename}
23153 Execute the command file @var{filename}.
23156 The lines in a command file are generally executed sequentially,
23157 unless the order of execution is changed by one of the
23158 @emph{flow-control commands} described below. The commands are not
23159 printed as they are executed. An error in any command terminates
23160 execution of the command file and control is returned to the console.
23162 @value{GDBN} first searches for @var{filename} in the current directory.
23163 If the file is not found there, and @var{filename} does not specify a
23164 directory, then @value{GDBN} also looks for the file on the source search path
23165 (specified with the @samp{directory} command);
23166 except that @file{$cdir} is not searched because the compilation directory
23167 is not relevant to scripts.
23169 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23170 on the search path even if @var{filename} specifies a directory.
23171 The search is done by appending @var{filename} to each element of the
23172 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23173 and the search path contains @file{/home/user} then @value{GDBN} will
23174 look for the script @file{/home/user/mylib/myscript}.
23175 The search is also done if @var{filename} is an absolute path.
23176 For example, if @var{filename} is @file{/tmp/myscript} and
23177 the search path contains @file{/home/user} then @value{GDBN} will
23178 look for the script @file{/home/user/tmp/myscript}.
23179 For DOS-like systems, if @var{filename} contains a drive specification,
23180 it is stripped before concatenation. For example, if @var{filename} is
23181 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23182 will look for the script @file{c:/tmp/myscript}.
23184 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23185 each command as it is executed. The option must be given before
23186 @var{filename}, and is interpreted as part of the filename anywhere else.
23188 Commands that would ask for confirmation if used interactively proceed
23189 without asking when used in a command file. Many @value{GDBN} commands that
23190 normally print messages to say what they are doing omit the messages
23191 when called from command files.
23193 @value{GDBN} also accepts command input from standard input. In this
23194 mode, normal output goes to standard output and error output goes to
23195 standard error. Errors in a command file supplied on standard input do
23196 not terminate execution of the command file---execution continues with
23200 gdb < cmds > log 2>&1
23203 (The syntax above will vary depending on the shell used.) This example
23204 will execute commands from the file @file{cmds}. All output and errors
23205 would be directed to @file{log}.
23207 Since commands stored on command files tend to be more general than
23208 commands typed interactively, they frequently need to deal with
23209 complicated situations, such as different or unexpected values of
23210 variables and symbols, changes in how the program being debugged is
23211 built, etc. @value{GDBN} provides a set of flow-control commands to
23212 deal with these complexities. Using these commands, you can write
23213 complex scripts that loop over data structures, execute commands
23214 conditionally, etc.
23221 This command allows to include in your script conditionally executed
23222 commands. The @code{if} command takes a single argument, which is an
23223 expression to evaluate. It is followed by a series of commands that
23224 are executed only if the expression is true (its value is nonzero).
23225 There can then optionally be an @code{else} line, followed by a series
23226 of commands that are only executed if the expression was false. The
23227 end of the list is marked by a line containing @code{end}.
23231 This command allows to write loops. Its syntax is similar to
23232 @code{if}: the command takes a single argument, which is an expression
23233 to evaluate, and must be followed by the commands to execute, one per
23234 line, terminated by an @code{end}. These commands are called the
23235 @dfn{body} of the loop. The commands in the body of @code{while} are
23236 executed repeatedly as long as the expression evaluates to true.
23240 This command exits the @code{while} loop in whose body it is included.
23241 Execution of the script continues after that @code{while}s @code{end}
23244 @kindex loop_continue
23245 @item loop_continue
23246 This command skips the execution of the rest of the body of commands
23247 in the @code{while} loop in whose body it is included. Execution
23248 branches to the beginning of the @code{while} loop, where it evaluates
23249 the controlling expression.
23251 @kindex end@r{ (if/else/while commands)}
23253 Terminate the block of commands that are the body of @code{if},
23254 @code{else}, or @code{while} flow-control commands.
23259 @subsection Commands for Controlled Output
23261 During the execution of a command file or a user-defined command, normal
23262 @value{GDBN} output is suppressed; the only output that appears is what is
23263 explicitly printed by the commands in the definition. This section
23264 describes three commands useful for generating exactly the output you
23269 @item echo @var{text}
23270 @c I do not consider backslash-space a standard C escape sequence
23271 @c because it is not in ANSI.
23272 Print @var{text}. Nonprinting characters can be included in
23273 @var{text} using C escape sequences, such as @samp{\n} to print a
23274 newline. @strong{No newline is printed unless you specify one.}
23275 In addition to the standard C escape sequences, a backslash followed
23276 by a space stands for a space. This is useful for displaying a
23277 string with spaces at the beginning or the end, since leading and
23278 trailing spaces are otherwise trimmed from all arguments.
23279 To print @samp{@w{ }and foo =@w{ }}, use the command
23280 @samp{echo \@w{ }and foo = \@w{ }}.
23282 A backslash at the end of @var{text} can be used, as in C, to continue
23283 the command onto subsequent lines. For example,
23286 echo This is some text\n\
23287 which is continued\n\
23288 onto several lines.\n
23291 produces the same output as
23294 echo This is some text\n
23295 echo which is continued\n
23296 echo onto several lines.\n
23300 @item output @var{expression}
23301 Print the value of @var{expression} and nothing but that value: no
23302 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23303 value history either. @xref{Expressions, ,Expressions}, for more information
23306 @item output/@var{fmt} @var{expression}
23307 Print the value of @var{expression} in format @var{fmt}. You can use
23308 the same formats as for @code{print}. @xref{Output Formats,,Output
23309 Formats}, for more information.
23312 @item printf @var{template}, @var{expressions}@dots{}
23313 Print the values of one or more @var{expressions} under the control of
23314 the string @var{template}. To print several values, make
23315 @var{expressions} be a comma-separated list of individual expressions,
23316 which may be either numbers or pointers. Their values are printed as
23317 specified by @var{template}, exactly as a C program would do by
23318 executing the code below:
23321 printf (@var{template}, @var{expressions}@dots{});
23324 As in @code{C} @code{printf}, ordinary characters in @var{template}
23325 are printed verbatim, while @dfn{conversion specification} introduced
23326 by the @samp{%} character cause subsequent @var{expressions} to be
23327 evaluated, their values converted and formatted according to type and
23328 style information encoded in the conversion specifications, and then
23331 For example, you can print two values in hex like this:
23334 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23337 @code{printf} supports all the standard @code{C} conversion
23338 specifications, including the flags and modifiers between the @samp{%}
23339 character and the conversion letter, with the following exceptions:
23343 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23346 The modifier @samp{*} is not supported for specifying precision or
23350 The @samp{'} flag (for separation of digits into groups according to
23351 @code{LC_NUMERIC'}) is not supported.
23354 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23358 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23361 The conversion letters @samp{a} and @samp{A} are not supported.
23365 Note that the @samp{ll} type modifier is supported only if the
23366 underlying @code{C} implementation used to build @value{GDBN} supports
23367 the @code{long long int} type, and the @samp{L} type modifier is
23368 supported only if @code{long double} type is available.
23370 As in @code{C}, @code{printf} supports simple backslash-escape
23371 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23372 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23373 single character. Octal and hexadecimal escape sequences are not
23376 Additionally, @code{printf} supports conversion specifications for DFP
23377 (@dfn{Decimal Floating Point}) types using the following length modifiers
23378 together with a floating point specifier.
23383 @samp{H} for printing @code{Decimal32} types.
23386 @samp{D} for printing @code{Decimal64} types.
23389 @samp{DD} for printing @code{Decimal128} types.
23392 If the underlying @code{C} implementation used to build @value{GDBN} has
23393 support for the three length modifiers for DFP types, other modifiers
23394 such as width and precision will also be available for @value{GDBN} to use.
23396 In case there is no such @code{C} support, no additional modifiers will be
23397 available and the value will be printed in the standard way.
23399 Here's an example of printing DFP types using the above conversion letters:
23401 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23405 @item eval @var{template}, @var{expressions}@dots{}
23406 Convert the values of one or more @var{expressions} under the control of
23407 the string @var{template} to a command line, and call it.
23411 @node Auto-loading sequences
23412 @subsection Controlling auto-loading native @value{GDBN} scripts
23413 @cindex native script auto-loading
23415 When a new object file is read (for example, due to the @code{file}
23416 command, or because the inferior has loaded a shared library),
23417 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23418 @xref{Auto-loading extensions}.
23420 Auto-loading can be enabled or disabled,
23421 and the list of auto-loaded scripts can be printed.
23424 @anchor{set auto-load gdb-scripts}
23425 @kindex set auto-load gdb-scripts
23426 @item set auto-load gdb-scripts [on|off]
23427 Enable or disable the auto-loading of canned sequences of commands scripts.
23429 @anchor{show auto-load gdb-scripts}
23430 @kindex show auto-load gdb-scripts
23431 @item show auto-load gdb-scripts
23432 Show whether auto-loading of canned sequences of commands scripts is enabled or
23435 @anchor{info auto-load gdb-scripts}
23436 @kindex info auto-load gdb-scripts
23437 @cindex print list of auto-loaded canned sequences of commands scripts
23438 @item info auto-load gdb-scripts [@var{regexp}]
23439 Print the list of all canned sequences of commands scripts that @value{GDBN}
23443 If @var{regexp} is supplied only canned sequences of commands scripts with
23444 matching names are printed.
23447 @section Extending @value{GDBN} using Python
23448 @cindex python scripting
23449 @cindex scripting with python
23451 You can extend @value{GDBN} using the @uref{http://www.python.org/,
23452 Python programming language}. This feature is available only if
23453 @value{GDBN} was configured using @option{--with-python}.
23455 @cindex python directory
23456 Python scripts used by @value{GDBN} should be installed in
23457 @file{@var{data-directory}/python}, where @var{data-directory} is
23458 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23459 This directory, known as the @dfn{python directory},
23460 is automatically added to the Python Search Path in order to allow
23461 the Python interpreter to locate all scripts installed at this location.
23463 Additionally, @value{GDBN} commands and convenience functions which
23464 are written in Python and are located in the
23465 @file{@var{data-directory}/python/gdb/command} or
23466 @file{@var{data-directory}/python/gdb/function} directories are
23467 automatically imported when @value{GDBN} starts.
23470 * Python Commands:: Accessing Python from @value{GDBN}.
23471 * Python API:: Accessing @value{GDBN} from Python.
23472 * Python Auto-loading:: Automatically loading Python code.
23473 * Python modules:: Python modules provided by @value{GDBN}.
23476 @node Python Commands
23477 @subsection Python Commands
23478 @cindex python commands
23479 @cindex commands to access python
23481 @value{GDBN} provides two commands for accessing the Python interpreter,
23482 and one related setting:
23485 @kindex python-interactive
23487 @item python-interactive @r{[}@var{command}@r{]}
23488 @itemx pi @r{[}@var{command}@r{]}
23489 Without an argument, the @code{python-interactive} command can be used
23490 to start an interactive Python prompt. To return to @value{GDBN},
23491 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23493 Alternatively, a single-line Python command can be given as an
23494 argument and evaluated. If the command is an expression, the result
23495 will be printed; otherwise, nothing will be printed. For example:
23498 (@value{GDBP}) python-interactive 2 + 3
23504 @item python @r{[}@var{command}@r{]}
23505 @itemx py @r{[}@var{command}@r{]}
23506 The @code{python} command can be used to evaluate Python code.
23508 If given an argument, the @code{python} command will evaluate the
23509 argument as a Python command. For example:
23512 (@value{GDBP}) python print 23
23516 If you do not provide an argument to @code{python}, it will act as a
23517 multi-line command, like @code{define}. In this case, the Python
23518 script is made up of subsequent command lines, given after the
23519 @code{python} command. This command list is terminated using a line
23520 containing @code{end}. For example:
23523 (@value{GDBP}) python
23525 End with a line saying just "end".
23531 @kindex set python print-stack
23532 @item set python print-stack
23533 By default, @value{GDBN} will print only the message component of a
23534 Python exception when an error occurs in a Python script. This can be
23535 controlled using @code{set python print-stack}: if @code{full}, then
23536 full Python stack printing is enabled; if @code{none}, then Python stack
23537 and message printing is disabled; if @code{message}, the default, only
23538 the message component of the error is printed.
23541 It is also possible to execute a Python script from the @value{GDBN}
23545 @item source @file{script-name}
23546 The script name must end with @samp{.py} and @value{GDBN} must be configured
23547 to recognize the script language based on filename extension using
23548 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23550 @item python execfile ("script-name")
23551 This method is based on the @code{execfile} Python built-in function,
23552 and thus is always available.
23556 @subsection Python API
23558 @cindex programming in python
23560 You can get quick online help for @value{GDBN}'s Python API by issuing
23561 the command @w{@kbd{python help (gdb)}}.
23563 Functions and methods which have two or more optional arguments allow
23564 them to be specified using keyword syntax. This allows passing some
23565 optional arguments while skipping others. Example:
23566 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23569 * Basic Python:: Basic Python Functions.
23570 * Exception Handling:: How Python exceptions are translated.
23571 * Values From Inferior:: Python representation of values.
23572 * Types In Python:: Python representation of types.
23573 * Pretty Printing API:: Pretty-printing values.
23574 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23575 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23576 * Type Printing API:: Pretty-printing types.
23577 * Frame Filter API:: Filtering Frames.
23578 * Frame Decorator API:: Decorating Frames.
23579 * Writing a Frame Filter:: Writing a Frame Filter.
23580 * Inferiors In Python:: Python representation of inferiors (processes)
23581 * Events In Python:: Listening for events from @value{GDBN}.
23582 * Threads In Python:: Accessing inferior threads from Python.
23583 * Commands In Python:: Implementing new commands in Python.
23584 * Parameters In Python:: Adding new @value{GDBN} parameters.
23585 * Functions In Python:: Writing new convenience functions.
23586 * Progspaces In Python:: Program spaces.
23587 * Objfiles In Python:: Object files.
23588 * Frames In Python:: Accessing inferior stack frames from Python.
23589 * Blocks In Python:: Accessing blocks from Python.
23590 * Symbols In Python:: Python representation of symbols.
23591 * Symbol Tables In Python:: Python representation of symbol tables.
23592 * Line Tables In Python:: Python representation of line tables.
23593 * Breakpoints In Python:: Manipulating breakpoints using Python.
23594 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23596 * Lazy Strings In Python:: Python representation of lazy strings.
23597 * Architectures In Python:: Python representation of architectures.
23601 @subsubsection Basic Python
23603 @cindex python stdout
23604 @cindex python pagination
23605 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23606 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23607 A Python program which outputs to one of these streams may have its
23608 output interrupted by the user (@pxref{Screen Size}). In this
23609 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23611 Some care must be taken when writing Python code to run in
23612 @value{GDBN}. Two things worth noting in particular:
23616 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23617 Python code must not override these, or even change the options using
23618 @code{sigaction}. If your program changes the handling of these
23619 signals, @value{GDBN} will most likely stop working correctly. Note
23620 that it is unfortunately common for GUI toolkits to install a
23621 @code{SIGCHLD} handler.
23624 @value{GDBN} takes care to mark its internal file descriptors as
23625 close-on-exec. However, this cannot be done in a thread-safe way on
23626 all platforms. Your Python programs should be aware of this and
23627 should both create new file descriptors with the close-on-exec flag
23628 set and arrange to close unneeded file descriptors before starting a
23632 @cindex python functions
23633 @cindex python module
23635 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23636 methods and classes added by @value{GDBN} are placed in this module.
23637 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23638 use in all scripts evaluated by the @code{python} command.
23640 @findex gdb.PYTHONDIR
23641 @defvar gdb.PYTHONDIR
23642 A string containing the python directory (@pxref{Python}).
23645 @findex gdb.execute
23646 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23647 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23648 If a GDB exception happens while @var{command} runs, it is
23649 translated as described in @ref{Exception Handling,,Exception Handling}.
23651 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23652 command as having originated from the user invoking it interactively.
23653 It must be a boolean value. If omitted, it defaults to @code{False}.
23655 By default, any output produced by @var{command} is sent to
23656 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23657 @code{True}, then output will be collected by @code{gdb.execute} and
23658 returned as a string. The default is @code{False}, in which case the
23659 return value is @code{None}. If @var{to_string} is @code{True}, the
23660 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23661 and height, and its pagination will be disabled; @pxref{Screen Size}.
23664 @findex gdb.breakpoints
23665 @defun gdb.breakpoints ()
23666 Return a sequence holding all of @value{GDBN}'s breakpoints.
23667 @xref{Breakpoints In Python}, for more information.
23670 @findex gdb.parameter
23671 @defun gdb.parameter (parameter)
23672 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23673 string naming the parameter to look up; @var{parameter} may contain
23674 spaces if the parameter has a multi-part name. For example,
23675 @samp{print object} is a valid parameter name.
23677 If the named parameter does not exist, this function throws a
23678 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23679 parameter's value is converted to a Python value of the appropriate
23680 type, and returned.
23683 @findex gdb.history
23684 @defun gdb.history (number)
23685 Return a value from @value{GDBN}'s value history (@pxref{Value
23686 History}). @var{number} indicates which history element to return.
23687 If @var{number} is negative, then @value{GDBN} will take its absolute value
23688 and count backward from the last element (i.e., the most recent element) to
23689 find the value to return. If @var{number} is zero, then @value{GDBN} will
23690 return the most recent element. If the element specified by @var{number}
23691 doesn't exist in the value history, a @code{gdb.error} exception will be
23694 If no exception is raised, the return value is always an instance of
23695 @code{gdb.Value} (@pxref{Values From Inferior}).
23698 @findex gdb.parse_and_eval
23699 @defun gdb.parse_and_eval (expression)
23700 Parse @var{expression} as an expression in the current language,
23701 evaluate it, and return the result as a @code{gdb.Value}.
23702 @var{expression} must be a string.
23704 This function can be useful when implementing a new command
23705 (@pxref{Commands In Python}), as it provides a way to parse the
23706 command's argument as an expression. It is also useful simply to
23707 compute values, for example, it is the only way to get the value of a
23708 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23711 @findex gdb.find_pc_line
23712 @defun gdb.find_pc_line (pc)
23713 Return the @code{gdb.Symtab_and_line} object corresponding to the
23714 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23715 value of @var{pc} is passed as an argument, then the @code{symtab} and
23716 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23717 will be @code{None} and 0 respectively.
23720 @findex gdb.post_event
23721 @defun gdb.post_event (event)
23722 Put @var{event}, a callable object taking no arguments, into
23723 @value{GDBN}'s internal event queue. This callable will be invoked at
23724 some later point, during @value{GDBN}'s event processing. Events
23725 posted using @code{post_event} will be run in the order in which they
23726 were posted; however, there is no way to know when they will be
23727 processed relative to other events inside @value{GDBN}.
23729 @value{GDBN} is not thread-safe. If your Python program uses multiple
23730 threads, you must be careful to only call @value{GDBN}-specific
23731 functions in the main @value{GDBN} thread. @code{post_event} ensures
23735 (@value{GDBP}) python
23739 > def __init__(self, message):
23740 > self.message = message;
23741 > def __call__(self):
23742 > gdb.write(self.message)
23744 >class MyThread1 (threading.Thread):
23746 > gdb.post_event(Writer("Hello "))
23748 >class MyThread2 (threading.Thread):
23750 > gdb.post_event(Writer("World\n"))
23752 >MyThread1().start()
23753 >MyThread2().start()
23755 (@value{GDBP}) Hello World
23760 @defun gdb.write (string @r{[}, stream{]})
23761 Print a string to @value{GDBN}'s paginated output stream. The
23762 optional @var{stream} determines the stream to print to. The default
23763 stream is @value{GDBN}'s standard output stream. Possible stream
23770 @value{GDBN}'s standard output stream.
23775 @value{GDBN}'s standard error stream.
23780 @value{GDBN}'s log stream (@pxref{Logging Output}).
23783 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23784 call this function and will automatically direct the output to the
23789 @defun gdb.flush ()
23790 Flush the buffer of a @value{GDBN} paginated stream so that the
23791 contents are displayed immediately. @value{GDBN} will flush the
23792 contents of a stream automatically when it encounters a newline in the
23793 buffer. The optional @var{stream} determines the stream to flush. The
23794 default stream is @value{GDBN}'s standard output stream. Possible
23801 @value{GDBN}'s standard output stream.
23806 @value{GDBN}'s standard error stream.
23811 @value{GDBN}'s log stream (@pxref{Logging Output}).
23815 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23816 call this function for the relevant stream.
23819 @findex gdb.target_charset
23820 @defun gdb.target_charset ()
23821 Return the name of the current target character set (@pxref{Character
23822 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23823 that @samp{auto} is never returned.
23826 @findex gdb.target_wide_charset
23827 @defun gdb.target_wide_charset ()
23828 Return the name of the current target wide character set
23829 (@pxref{Character Sets}). This differs from
23830 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23834 @findex gdb.solib_name
23835 @defun gdb.solib_name (address)
23836 Return the name of the shared library holding the given @var{address}
23837 as a string, or @code{None}.
23840 @findex gdb.decode_line
23841 @defun gdb.decode_line @r{[}expression@r{]}
23842 Return locations of the line specified by @var{expression}, or of the
23843 current line if no argument was given. This function returns a Python
23844 tuple containing two elements. The first element contains a string
23845 holding any unparsed section of @var{expression} (or @code{None} if
23846 the expression has been fully parsed). The second element contains
23847 either @code{None} or another tuple that contains all the locations
23848 that match the expression represented as @code{gdb.Symtab_and_line}
23849 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23850 provided, it is decoded the way that @value{GDBN}'s inbuilt
23851 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23854 @defun gdb.prompt_hook (current_prompt)
23855 @anchor{prompt_hook}
23857 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23858 assigned to this operation before a prompt is displayed by
23861 The parameter @code{current_prompt} contains the current @value{GDBN}
23862 prompt. This method must return a Python string, or @code{None}. If
23863 a string is returned, the @value{GDBN} prompt will be set to that
23864 string. If @code{None} is returned, @value{GDBN} will continue to use
23865 the current prompt.
23867 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23868 such as those used by readline for command input, and annotation
23869 related prompts are prohibited from being changed.
23872 @node Exception Handling
23873 @subsubsection Exception Handling
23874 @cindex python exceptions
23875 @cindex exceptions, python
23877 When executing the @code{python} command, Python exceptions
23878 uncaught within the Python code are translated to calls to
23879 @value{GDBN} error-reporting mechanism. If the command that called
23880 @code{python} does not handle the error, @value{GDBN} will
23881 terminate it and print an error message containing the Python
23882 exception name, the associated value, and the Python call stack
23883 backtrace at the point where the exception was raised. Example:
23886 (@value{GDBP}) python print foo
23887 Traceback (most recent call last):
23888 File "<string>", line 1, in <module>
23889 NameError: name 'foo' is not defined
23892 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23893 Python code are converted to Python exceptions. The type of the
23894 Python exception depends on the error.
23898 This is the base class for most exceptions generated by @value{GDBN}.
23899 It is derived from @code{RuntimeError}, for compatibility with earlier
23900 versions of @value{GDBN}.
23902 If an error occurring in @value{GDBN} does not fit into some more
23903 specific category, then the generated exception will have this type.
23905 @item gdb.MemoryError
23906 This is a subclass of @code{gdb.error} which is thrown when an
23907 operation tried to access invalid memory in the inferior.
23909 @item KeyboardInterrupt
23910 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23911 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23914 In all cases, your exception handler will see the @value{GDBN} error
23915 message as its value and the Python call stack backtrace at the Python
23916 statement closest to where the @value{GDBN} error occured as the
23919 @findex gdb.GdbError
23920 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23921 it is useful to be able to throw an exception that doesn't cause a
23922 traceback to be printed. For example, the user may have invoked the
23923 command incorrectly. Use the @code{gdb.GdbError} exception
23924 to handle this case. Example:
23928 >class HelloWorld (gdb.Command):
23929 > """Greet the whole world."""
23930 > def __init__ (self):
23931 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23932 > def invoke (self, args, from_tty):
23933 > argv = gdb.string_to_argv (args)
23934 > if len (argv) != 0:
23935 > raise gdb.GdbError ("hello-world takes no arguments")
23936 > print "Hello, World!"
23939 (gdb) hello-world 42
23940 hello-world takes no arguments
23943 @node Values From Inferior
23944 @subsubsection Values From Inferior
23945 @cindex values from inferior, with Python
23946 @cindex python, working with values from inferior
23948 @cindex @code{gdb.Value}
23949 @value{GDBN} provides values it obtains from the inferior program in
23950 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23951 for its internal bookkeeping of the inferior's values, and for
23952 fetching values when necessary.
23954 Inferior values that are simple scalars can be used directly in
23955 Python expressions that are valid for the value's data type. Here's
23956 an example for an integer or floating-point value @code{some_val}:
23963 As result of this, @code{bar} will also be a @code{gdb.Value} object
23964 whose values are of the same type as those of @code{some_val}.
23966 Inferior values that are structures or instances of some class can
23967 be accessed using the Python @dfn{dictionary syntax}. For example, if
23968 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23969 can access its @code{foo} element with:
23972 bar = some_val['foo']
23975 @cindex getting structure elements using gdb.Field objects as subscripts
23976 Again, @code{bar} will also be a @code{gdb.Value} object. Structure
23977 elements can also be accessed by using @code{gdb.Field} objects as
23978 subscripts (@pxref{Types In Python}, for more information on
23979 @code{gdb.Field} objects). For example, if @code{foo_field} is a
23980 @code{gdb.Field} object corresponding to element @code{foo} of the above
23981 structure, then @code{bar} can also be accessed as follows:
23984 bar = some_val[foo_field]
23987 A @code{gdb.Value} that represents a function can be executed via
23988 inferior function call. Any arguments provided to the call must match
23989 the function's prototype, and must be provided in the order specified
23992 For example, @code{some_val} is a @code{gdb.Value} instance
23993 representing a function that takes two integers as arguments. To
23994 execute this function, call it like so:
23997 result = some_val (10,20)
24000 Any values returned from a function call will be stored as a
24003 The following attributes are provided:
24005 @defvar Value.address
24006 If this object is addressable, this read-only attribute holds a
24007 @code{gdb.Value} object representing the address. Otherwise,
24008 this attribute holds @code{None}.
24011 @cindex optimized out value in Python
24012 @defvar Value.is_optimized_out
24013 This read-only boolean attribute is true if the compiler optimized out
24014 this value, thus it is not available for fetching from the inferior.
24018 The type of this @code{gdb.Value}. The value of this attribute is a
24019 @code{gdb.Type} object (@pxref{Types In Python}).
24022 @defvar Value.dynamic_type
24023 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
24024 type information (@acronym{RTTI}) to determine the dynamic type of the
24025 value. If this value is of class type, it will return the class in
24026 which the value is embedded, if any. If this value is of pointer or
24027 reference to a class type, it will compute the dynamic type of the
24028 referenced object, and return a pointer or reference to that type,
24029 respectively. In all other cases, it will return the value's static
24032 Note that this feature will only work when debugging a C@t{++} program
24033 that includes @acronym{RTTI} for the object in question. Otherwise,
24034 it will just return the static type of the value as in @kbd{ptype foo}
24035 (@pxref{Symbols, ptype}).
24038 @defvar Value.is_lazy
24039 The value of this read-only boolean attribute is @code{True} if this
24040 @code{gdb.Value} has not yet been fetched from the inferior.
24041 @value{GDBN} does not fetch values until necessary, for efficiency.
24045 myval = gdb.parse_and_eval ('somevar')
24048 The value of @code{somevar} is not fetched at this time. It will be
24049 fetched when the value is needed, or when the @code{fetch_lazy}
24053 The following methods are provided:
24055 @defun Value.__init__ (@var{val})
24056 Many Python values can be converted directly to a @code{gdb.Value} via
24057 this object initializer. Specifically:
24060 @item Python boolean
24061 A Python boolean is converted to the boolean type from the current
24064 @item Python integer
24065 A Python integer is converted to the C @code{long} type for the
24066 current architecture.
24069 A Python long is converted to the C @code{long long} type for the
24070 current architecture.
24073 A Python float is converted to the C @code{double} type for the
24074 current architecture.
24076 @item Python string
24077 A Python string is converted to a target string, using the current
24080 @item @code{gdb.Value}
24081 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24083 @item @code{gdb.LazyString}
24084 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24085 Python}), then the lazy string's @code{value} method is called, and
24086 its result is used.
24090 @defun Value.cast (type)
24091 Return a new instance of @code{gdb.Value} that is the result of
24092 casting this instance to the type described by @var{type}, which must
24093 be a @code{gdb.Type} object. If the cast cannot be performed for some
24094 reason, this method throws an exception.
24097 @defun Value.dereference ()
24098 For pointer data types, this method returns a new @code{gdb.Value} object
24099 whose contents is the object pointed to by the pointer. For example, if
24100 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24107 then you can use the corresponding @code{gdb.Value} to access what
24108 @code{foo} points to like this:
24111 bar = foo.dereference ()
24114 The result @code{bar} will be a @code{gdb.Value} object holding the
24115 value pointed to by @code{foo}.
24117 A similar function @code{Value.referenced_value} exists which also
24118 returns @code{gdb.Value} objects corresonding to the values pointed to
24119 by pointer values (and additionally, values referenced by reference
24120 values). However, the behavior of @code{Value.dereference}
24121 differs from @code{Value.referenced_value} by the fact that the
24122 behavior of @code{Value.dereference} is identical to applying the C
24123 unary operator @code{*} on a given value. For example, consider a
24124 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24128 typedef int *intptr;
24132 intptr &ptrref = ptr;
24135 Though @code{ptrref} is a reference value, one can apply the method
24136 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24137 to it and obtain a @code{gdb.Value} which is identical to that
24138 corresponding to @code{val}. However, if you apply the method
24139 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24140 object identical to that corresponding to @code{ptr}.
24143 py_ptrref = gdb.parse_and_eval ("ptrref")
24144 py_val = py_ptrref.dereference ()
24145 py_ptr = py_ptrref.referenced_value ()
24148 The @code{gdb.Value} object @code{py_val} is identical to that
24149 corresponding to @code{val}, and @code{py_ptr} is identical to that
24150 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24151 be applied whenever the C unary operator @code{*} can be applied
24152 to the corresponding C value. For those cases where applying both
24153 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24154 the results obtained need not be identical (as we have seen in the above
24155 example). The results are however identical when applied on
24156 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24157 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24160 @defun Value.referenced_value ()
24161 For pointer or reference data types, this method returns a new
24162 @code{gdb.Value} object corresponding to the value referenced by the
24163 pointer/reference value. For pointer data types,
24164 @code{Value.dereference} and @code{Value.referenced_value} produce
24165 identical results. The difference between these methods is that
24166 @code{Value.dereference} cannot get the values referenced by reference
24167 values. For example, consider a reference to an @code{int}, declared
24168 in your C@t{++} program as
24176 then applying @code{Value.dereference} to the @code{gdb.Value} object
24177 corresponding to @code{ref} will result in an error, while applying
24178 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24179 identical to that corresponding to @code{val}.
24182 py_ref = gdb.parse_and_eval ("ref")
24183 er_ref = py_ref.dereference () # Results in error
24184 py_val = py_ref.referenced_value () # Returns the referenced value
24187 The @code{gdb.Value} object @code{py_val} is identical to that
24188 corresponding to @code{val}.
24191 @defun Value.dynamic_cast (type)
24192 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24193 operator were used. Consult a C@t{++} reference for details.
24196 @defun Value.reinterpret_cast (type)
24197 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24198 operator were used. Consult a C@t{++} reference for details.
24201 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24202 If this @code{gdb.Value} represents a string, then this method
24203 converts the contents to a Python string. Otherwise, this method will
24204 throw an exception.
24206 Strings are recognized in a language-specific way; whether a given
24207 @code{gdb.Value} represents a string is determined by the current
24210 For C-like languages, a value is a string if it is a pointer to or an
24211 array of characters or ints. The string is assumed to be terminated
24212 by a zero of the appropriate width. However if the optional length
24213 argument is given, the string will be converted to that given length,
24214 ignoring any embedded zeros that the string may contain.
24216 If the optional @var{encoding} argument is given, it must be a string
24217 naming the encoding of the string in the @code{gdb.Value}, such as
24218 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24219 the same encodings as the corresponding argument to Python's
24220 @code{string.decode} method, and the Python codec machinery will be used
24221 to convert the string. If @var{encoding} is not given, or if
24222 @var{encoding} is the empty string, then either the @code{target-charset}
24223 (@pxref{Character Sets}) will be used, or a language-specific encoding
24224 will be used, if the current language is able to supply one.
24226 The optional @var{errors} argument is the same as the corresponding
24227 argument to Python's @code{string.decode} method.
24229 If the optional @var{length} argument is given, the string will be
24230 fetched and converted to the given length.
24233 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24234 If this @code{gdb.Value} represents a string, then this method
24235 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24236 In Python}). Otherwise, this method will throw an exception.
24238 If the optional @var{encoding} argument is given, it must be a string
24239 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24240 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24241 @var{encoding} argument is an encoding that @value{GDBN} does
24242 recognize, @value{GDBN} will raise an error.
24244 When a lazy string is printed, the @value{GDBN} encoding machinery is
24245 used to convert the string during printing. If the optional
24246 @var{encoding} argument is not provided, or is an empty string,
24247 @value{GDBN} will automatically select the encoding most suitable for
24248 the string type. For further information on encoding in @value{GDBN}
24249 please see @ref{Character Sets}.
24251 If the optional @var{length} argument is given, the string will be
24252 fetched and encoded to the length of characters specified. If
24253 the @var{length} argument is not provided, the string will be fetched
24254 and encoded until a null of appropriate width is found.
24257 @defun Value.fetch_lazy ()
24258 If the @code{gdb.Value} object is currently a lazy value
24259 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24260 fetched from the inferior. Any errors that occur in the process
24261 will produce a Python exception.
24263 If the @code{gdb.Value} object is not a lazy value, this method
24266 This method does not return a value.
24270 @node Types In Python
24271 @subsubsection Types In Python
24272 @cindex types in Python
24273 @cindex Python, working with types
24276 @value{GDBN} represents types from the inferior using the class
24279 The following type-related functions are available in the @code{gdb}
24282 @findex gdb.lookup_type
24283 @defun gdb.lookup_type (name @r{[}, block@r{]})
24284 This function looks up a type by name. @var{name} is the name of the
24285 type to look up. It must be a string.
24287 If @var{block} is given, then @var{name} is looked up in that scope.
24288 Otherwise, it is searched for globally.
24290 Ordinarily, this function will return an instance of @code{gdb.Type}.
24291 If the named type cannot be found, it will throw an exception.
24294 If the type is a structure or class type, or an enum type, the fields
24295 of that type can be accessed using the Python @dfn{dictionary syntax}.
24296 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24297 a structure type, you can access its @code{foo} field with:
24300 bar = some_type['foo']
24303 @code{bar} will be a @code{gdb.Field} object; see below under the
24304 description of the @code{Type.fields} method for a description of the
24305 @code{gdb.Field} class.
24307 An instance of @code{Type} has the following attributes:
24310 The type code for this type. The type code will be one of the
24311 @code{TYPE_CODE_} constants defined below.
24315 The name of this type. If this type has no name, then @code{None}
24319 @defvar Type.sizeof
24320 The size of this type, in target @code{char} units. Usually, a
24321 target's @code{char} type will be an 8-bit byte. However, on some
24322 unusual platforms, this type may have a different size.
24326 The tag name for this type. The tag name is the name after
24327 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24328 languages have this concept. If this type has no tag name, then
24329 @code{None} is returned.
24332 The following methods are provided:
24334 @defun Type.fields ()
24335 For structure and union types, this method returns the fields. Range
24336 types have two fields, the minimum and maximum values. Enum types
24337 have one field per enum constant. Function and method types have one
24338 field per parameter. The base types of C@t{++} classes are also
24339 represented as fields. If the type has no fields, or does not fit
24340 into one of these categories, an empty sequence will be returned.
24342 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24345 This attribute is not available for @code{enum} or @code{static}
24346 (as in C@t{++} or Java) fields. The value is the position, counting
24347 in bits, from the start of the containing type.
24350 This attribute is only available for @code{enum} fields, and its value
24351 is the enumeration member's integer representation.
24354 The name of the field, or @code{None} for anonymous fields.
24357 This is @code{True} if the field is artificial, usually meaning that
24358 it was provided by the compiler and not the user. This attribute is
24359 always provided, and is @code{False} if the field is not artificial.
24361 @item is_base_class
24362 This is @code{True} if the field represents a base class of a C@t{++}
24363 structure. This attribute is always provided, and is @code{False}
24364 if the field is not a base class of the type that is the argument of
24365 @code{fields}, or if that type was not a C@t{++} class.
24368 If the field is packed, or is a bitfield, then this will have a
24369 non-zero value, which is the size of the field in bits. Otherwise,
24370 this will be zero; in this case the field's size is given by its type.
24373 The type of the field. This is usually an instance of @code{Type},
24374 but it can be @code{None} in some situations.
24377 The type which contains this field. This is an instance of
24382 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24383 Return a new @code{gdb.Type} object which represents an array of this
24384 type. If one argument is given, it is the inclusive upper bound of
24385 the array; in this case the lower bound is zero. If two arguments are
24386 given, the first argument is the lower bound of the array, and the
24387 second argument is the upper bound of the array. An array's length
24388 must not be negative, but the bounds can be.
24391 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24392 Return a new @code{gdb.Type} object which represents a vector of this
24393 type. If one argument is given, it is the inclusive upper bound of
24394 the vector; in this case the lower bound is zero. If two arguments are
24395 given, the first argument is the lower bound of the vector, and the
24396 second argument is the upper bound of the vector. A vector's length
24397 must not be negative, but the bounds can be.
24399 The difference between an @code{array} and a @code{vector} is that
24400 arrays behave like in C: when used in expressions they decay to a pointer
24401 to the first element whereas vectors are treated as first class values.
24404 @defun Type.const ()
24405 Return a new @code{gdb.Type} object which represents a
24406 @code{const}-qualified variant of this type.
24409 @defun Type.volatile ()
24410 Return a new @code{gdb.Type} object which represents a
24411 @code{volatile}-qualified variant of this type.
24414 @defun Type.unqualified ()
24415 Return a new @code{gdb.Type} object which represents an unqualified
24416 variant of this type. That is, the result is neither @code{const} nor
24420 @defun Type.range ()
24421 Return a Python @code{Tuple} object that contains two elements: the
24422 low bound of the argument type and the high bound of that type. If
24423 the type does not have a range, @value{GDBN} will raise a
24424 @code{gdb.error} exception (@pxref{Exception Handling}).
24427 @defun Type.reference ()
24428 Return a new @code{gdb.Type} object which represents a reference to this
24432 @defun Type.pointer ()
24433 Return a new @code{gdb.Type} object which represents a pointer to this
24437 @defun Type.strip_typedefs ()
24438 Return a new @code{gdb.Type} that represents the real type,
24439 after removing all layers of typedefs.
24442 @defun Type.target ()
24443 Return a new @code{gdb.Type} object which represents the target type
24446 For a pointer type, the target type is the type of the pointed-to
24447 object. For an array type (meaning C-like arrays), the target type is
24448 the type of the elements of the array. For a function or method type,
24449 the target type is the type of the return value. For a complex type,
24450 the target type is the type of the elements. For a typedef, the
24451 target type is the aliased type.
24453 If the type does not have a target, this method will throw an
24457 @defun Type.template_argument (n @r{[}, block@r{]})
24458 If this @code{gdb.Type} is an instantiation of a template, this will
24459 return a new @code{gdb.Type} which represents the type of the
24460 @var{n}th template argument.
24462 If this @code{gdb.Type} is not a template type, this will throw an
24463 exception. Ordinarily, only C@t{++} code will have template types.
24465 If @var{block} is given, then @var{name} is looked up in that scope.
24466 Otherwise, it is searched for globally.
24470 Each type has a code, which indicates what category this type falls
24471 into. The available type categories are represented by constants
24472 defined in the @code{gdb} module:
24475 @findex TYPE_CODE_PTR
24476 @findex gdb.TYPE_CODE_PTR
24477 @item gdb.TYPE_CODE_PTR
24478 The type is a pointer.
24480 @findex TYPE_CODE_ARRAY
24481 @findex gdb.TYPE_CODE_ARRAY
24482 @item gdb.TYPE_CODE_ARRAY
24483 The type is an array.
24485 @findex TYPE_CODE_STRUCT
24486 @findex gdb.TYPE_CODE_STRUCT
24487 @item gdb.TYPE_CODE_STRUCT
24488 The type is a structure.
24490 @findex TYPE_CODE_UNION
24491 @findex gdb.TYPE_CODE_UNION
24492 @item gdb.TYPE_CODE_UNION
24493 The type is a union.
24495 @findex TYPE_CODE_ENUM
24496 @findex gdb.TYPE_CODE_ENUM
24497 @item gdb.TYPE_CODE_ENUM
24498 The type is an enum.
24500 @findex TYPE_CODE_FLAGS
24501 @findex gdb.TYPE_CODE_FLAGS
24502 @item gdb.TYPE_CODE_FLAGS
24503 A bit flags type, used for things such as status registers.
24505 @findex TYPE_CODE_FUNC
24506 @findex gdb.TYPE_CODE_FUNC
24507 @item gdb.TYPE_CODE_FUNC
24508 The type is a function.
24510 @findex TYPE_CODE_INT
24511 @findex gdb.TYPE_CODE_INT
24512 @item gdb.TYPE_CODE_INT
24513 The type is an integer type.
24515 @findex TYPE_CODE_FLT
24516 @findex gdb.TYPE_CODE_FLT
24517 @item gdb.TYPE_CODE_FLT
24518 A floating point type.
24520 @findex TYPE_CODE_VOID
24521 @findex gdb.TYPE_CODE_VOID
24522 @item gdb.TYPE_CODE_VOID
24523 The special type @code{void}.
24525 @findex TYPE_CODE_SET
24526 @findex gdb.TYPE_CODE_SET
24527 @item gdb.TYPE_CODE_SET
24530 @findex TYPE_CODE_RANGE
24531 @findex gdb.TYPE_CODE_RANGE
24532 @item gdb.TYPE_CODE_RANGE
24533 A range type, that is, an integer type with bounds.
24535 @findex TYPE_CODE_STRING
24536 @findex gdb.TYPE_CODE_STRING
24537 @item gdb.TYPE_CODE_STRING
24538 A string type. Note that this is only used for certain languages with
24539 language-defined string types; C strings are not represented this way.
24541 @findex TYPE_CODE_BITSTRING
24542 @findex gdb.TYPE_CODE_BITSTRING
24543 @item gdb.TYPE_CODE_BITSTRING
24544 A string of bits. It is deprecated.
24546 @findex TYPE_CODE_ERROR
24547 @findex gdb.TYPE_CODE_ERROR
24548 @item gdb.TYPE_CODE_ERROR
24549 An unknown or erroneous type.
24551 @findex TYPE_CODE_METHOD
24552 @findex gdb.TYPE_CODE_METHOD
24553 @item gdb.TYPE_CODE_METHOD
24554 A method type, as found in C@t{++} or Java.
24556 @findex TYPE_CODE_METHODPTR
24557 @findex gdb.TYPE_CODE_METHODPTR
24558 @item gdb.TYPE_CODE_METHODPTR
24559 A pointer-to-member-function.
24561 @findex TYPE_CODE_MEMBERPTR
24562 @findex gdb.TYPE_CODE_MEMBERPTR
24563 @item gdb.TYPE_CODE_MEMBERPTR
24564 A pointer-to-member.
24566 @findex TYPE_CODE_REF
24567 @findex gdb.TYPE_CODE_REF
24568 @item gdb.TYPE_CODE_REF
24571 @findex TYPE_CODE_CHAR
24572 @findex gdb.TYPE_CODE_CHAR
24573 @item gdb.TYPE_CODE_CHAR
24576 @findex TYPE_CODE_BOOL
24577 @findex gdb.TYPE_CODE_BOOL
24578 @item gdb.TYPE_CODE_BOOL
24581 @findex TYPE_CODE_COMPLEX
24582 @findex gdb.TYPE_CODE_COMPLEX
24583 @item gdb.TYPE_CODE_COMPLEX
24584 A complex float type.
24586 @findex TYPE_CODE_TYPEDEF
24587 @findex gdb.TYPE_CODE_TYPEDEF
24588 @item gdb.TYPE_CODE_TYPEDEF
24589 A typedef to some other type.
24591 @findex TYPE_CODE_NAMESPACE
24592 @findex gdb.TYPE_CODE_NAMESPACE
24593 @item gdb.TYPE_CODE_NAMESPACE
24594 A C@t{++} namespace.
24596 @findex TYPE_CODE_DECFLOAT
24597 @findex gdb.TYPE_CODE_DECFLOAT
24598 @item gdb.TYPE_CODE_DECFLOAT
24599 A decimal floating point type.
24601 @findex TYPE_CODE_INTERNAL_FUNCTION
24602 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24603 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24604 A function internal to @value{GDBN}. This is the type used to represent
24605 convenience functions.
24608 Further support for types is provided in the @code{gdb.types}
24609 Python module (@pxref{gdb.types}).
24611 @node Pretty Printing API
24612 @subsubsection Pretty Printing API
24614 An example output is provided (@pxref{Pretty Printing}).
24616 A pretty-printer is just an object that holds a value and implements a
24617 specific interface, defined here.
24619 @defun pretty_printer.children (self)
24620 @value{GDBN} will call this method on a pretty-printer to compute the
24621 children of the pretty-printer's value.
24623 This method must return an object conforming to the Python iterator
24624 protocol. Each item returned by the iterator must be a tuple holding
24625 two elements. The first element is the ``name'' of the child; the
24626 second element is the child's value. The value can be any Python
24627 object which is convertible to a @value{GDBN} value.
24629 This method is optional. If it does not exist, @value{GDBN} will act
24630 as though the value has no children.
24633 @defun pretty_printer.display_hint (self)
24634 The CLI may call this method and use its result to change the
24635 formatting of a value. The result will also be supplied to an MI
24636 consumer as a @samp{displayhint} attribute of the variable being
24639 This method is optional. If it does exist, this method must return a
24642 Some display hints are predefined by @value{GDBN}:
24646 Indicate that the object being printed is ``array-like''. The CLI
24647 uses this to respect parameters such as @code{set print elements} and
24648 @code{set print array}.
24651 Indicate that the object being printed is ``map-like'', and that the
24652 children of this value can be assumed to alternate between keys and
24656 Indicate that the object being printed is ``string-like''. If the
24657 printer's @code{to_string} method returns a Python string of some
24658 kind, then @value{GDBN} will call its internal language-specific
24659 string-printing function to format the string. For the CLI this means
24660 adding quotation marks, possibly escaping some characters, respecting
24661 @code{set print elements}, and the like.
24665 @defun pretty_printer.to_string (self)
24666 @value{GDBN} will call this method to display the string
24667 representation of the value passed to the object's constructor.
24669 When printing from the CLI, if the @code{to_string} method exists,
24670 then @value{GDBN} will prepend its result to the values returned by
24671 @code{children}. Exactly how this formatting is done is dependent on
24672 the display hint, and may change as more hints are added. Also,
24673 depending on the print settings (@pxref{Print Settings}), the CLI may
24674 print just the result of @code{to_string} in a stack trace, omitting
24675 the result of @code{children}.
24677 If this method returns a string, it is printed verbatim.
24679 Otherwise, if this method returns an instance of @code{gdb.Value},
24680 then @value{GDBN} prints this value. This may result in a call to
24681 another pretty-printer.
24683 If instead the method returns a Python value which is convertible to a
24684 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24685 the resulting value. Again, this may result in a call to another
24686 pretty-printer. Python scalars (integers, floats, and booleans) and
24687 strings are convertible to @code{gdb.Value}; other types are not.
24689 Finally, if this method returns @code{None} then no further operations
24690 are peformed in this method and nothing is printed.
24692 If the result is not one of these types, an exception is raised.
24695 @value{GDBN} provides a function which can be used to look up the
24696 default pretty-printer for a @code{gdb.Value}:
24698 @findex gdb.default_visualizer
24699 @defun gdb.default_visualizer (value)
24700 This function takes a @code{gdb.Value} object as an argument. If a
24701 pretty-printer for this value exists, then it is returned. If no such
24702 printer exists, then this returns @code{None}.
24705 @node Selecting Pretty-Printers
24706 @subsubsection Selecting Pretty-Printers
24708 The Python list @code{gdb.pretty_printers} contains an array of
24709 functions or callable objects that have been registered via addition
24710 as a pretty-printer. Printers in this list are called @code{global}
24711 printers, they're available when debugging all inferiors.
24712 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24713 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24716 Each function on these lists is passed a single @code{gdb.Value}
24717 argument and should return a pretty-printer object conforming to the
24718 interface definition above (@pxref{Pretty Printing API}). If a function
24719 cannot create a pretty-printer for the value, it should return
24722 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24723 @code{gdb.Objfile} in the current program space and iteratively calls
24724 each enabled lookup routine in the list for that @code{gdb.Objfile}
24725 until it receives a pretty-printer object.
24726 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24727 searches the pretty-printer list of the current program space,
24728 calling each enabled function until an object is returned.
24729 After these lists have been exhausted, it tries the global
24730 @code{gdb.pretty_printers} list, again calling each enabled function until an
24731 object is returned.
24733 The order in which the objfiles are searched is not specified. For a
24734 given list, functions are always invoked from the head of the list,
24735 and iterated over sequentially until the end of the list, or a printer
24736 object is returned.
24738 For various reasons a pretty-printer may not work.
24739 For example, the underlying data structure may have changed and
24740 the pretty-printer is out of date.
24742 The consequences of a broken pretty-printer are severe enough that
24743 @value{GDBN} provides support for enabling and disabling individual
24744 printers. For example, if @code{print frame-arguments} is on,
24745 a backtrace can become highly illegible if any argument is printed
24746 with a broken printer.
24748 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24749 attribute to the registered function or callable object. If this attribute
24750 is present and its value is @code{False}, the printer is disabled, otherwise
24751 the printer is enabled.
24753 @node Writing a Pretty-Printer
24754 @subsubsection Writing a Pretty-Printer
24755 @cindex writing a pretty-printer
24757 A pretty-printer consists of two parts: a lookup function to detect
24758 if the type is supported, and the printer itself.
24760 Here is an example showing how a @code{std::string} printer might be
24761 written. @xref{Pretty Printing API}, for details on the API this class
24765 class StdStringPrinter(object):
24766 "Print a std::string"
24768 def __init__(self, val):
24771 def to_string(self):
24772 return self.val['_M_dataplus']['_M_p']
24774 def display_hint(self):
24778 And here is an example showing how a lookup function for the printer
24779 example above might be written.
24782 def str_lookup_function(val):
24783 lookup_tag = val.type.tag
24784 if lookup_tag == None:
24786 regex = re.compile("^std::basic_string<char,.*>$")
24787 if regex.match(lookup_tag):
24788 return StdStringPrinter(val)
24792 The example lookup function extracts the value's type, and attempts to
24793 match it to a type that it can pretty-print. If it is a type the
24794 printer can pretty-print, it will return a printer object. If not, it
24795 returns @code{None}.
24797 We recommend that you put your core pretty-printers into a Python
24798 package. If your pretty-printers are for use with a library, we
24799 further recommend embedding a version number into the package name.
24800 This practice will enable @value{GDBN} to load multiple versions of
24801 your pretty-printers at the same time, because they will have
24804 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24805 can be evaluated multiple times without changing its meaning. An
24806 ideal auto-load file will consist solely of @code{import}s of your
24807 printer modules, followed by a call to a register pretty-printers with
24808 the current objfile.
24810 Taken as a whole, this approach will scale nicely to multiple
24811 inferiors, each potentially using a different library version.
24812 Embedding a version number in the Python package name will ensure that
24813 @value{GDBN} is able to load both sets of printers simultaneously.
24814 Then, because the search for pretty-printers is done by objfile, and
24815 because your auto-loaded code took care to register your library's
24816 printers with a specific objfile, @value{GDBN} will find the correct
24817 printers for the specific version of the library used by each
24820 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24821 this code might appear in @code{gdb.libstdcxx.v6}:
24824 def register_printers(objfile):
24825 objfile.pretty_printers.append(str_lookup_function)
24829 And then the corresponding contents of the auto-load file would be:
24832 import gdb.libstdcxx.v6
24833 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24836 The previous example illustrates a basic pretty-printer.
24837 There are a few things that can be improved on.
24838 The printer doesn't have a name, making it hard to identify in a
24839 list of installed printers. The lookup function has a name, but
24840 lookup functions can have arbitrary, even identical, names.
24842 Second, the printer only handles one type, whereas a library typically has
24843 several types. One could install a lookup function for each desired type
24844 in the library, but one could also have a single lookup function recognize
24845 several types. The latter is the conventional way this is handled.
24846 If a pretty-printer can handle multiple data types, then its
24847 @dfn{subprinters} are the printers for the individual data types.
24849 The @code{gdb.printing} module provides a formal way of solving these
24850 problems (@pxref{gdb.printing}).
24851 Here is another example that handles multiple types.
24853 These are the types we are going to pretty-print:
24856 struct foo @{ int a, b; @};
24857 struct bar @{ struct foo x, y; @};
24860 Here are the printers:
24864 """Print a foo object."""
24866 def __init__(self, val):
24869 def to_string(self):
24870 return ("a=<" + str(self.val["a"]) +
24871 "> b=<" + str(self.val["b"]) + ">")
24874 """Print a bar object."""
24876 def __init__(self, val):
24879 def to_string(self):
24880 return ("x=<" + str(self.val["x"]) +
24881 "> y=<" + str(self.val["y"]) + ">")
24884 This example doesn't need a lookup function, that is handled by the
24885 @code{gdb.printing} module. Instead a function is provided to build up
24886 the object that handles the lookup.
24889 import gdb.printing
24891 def build_pretty_printer():
24892 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24894 pp.add_printer('foo', '^foo$', fooPrinter)
24895 pp.add_printer('bar', '^bar$', barPrinter)
24899 And here is the autoload support:
24902 import gdb.printing
24904 gdb.printing.register_pretty_printer(
24905 gdb.current_objfile(),
24906 my_library.build_pretty_printer())
24909 Finally, when this printer is loaded into @value{GDBN}, here is the
24910 corresponding output of @samp{info pretty-printer}:
24913 (gdb) info pretty-printer
24920 @node Type Printing API
24921 @subsubsection Type Printing API
24922 @cindex type printing API for Python
24924 @value{GDBN} provides a way for Python code to customize type display.
24925 This is mainly useful for substituting canonical typedef names for
24928 @cindex type printer
24929 A @dfn{type printer} is just a Python object conforming to a certain
24930 protocol. A simple base class implementing the protocol is provided;
24931 see @ref{gdb.types}. A type printer must supply at least:
24933 @defivar type_printer enabled
24934 A boolean which is True if the printer is enabled, and False
24935 otherwise. This is manipulated by the @code{enable type-printer}
24936 and @code{disable type-printer} commands.
24939 @defivar type_printer name
24940 The name of the type printer. This must be a string. This is used by
24941 the @code{enable type-printer} and @code{disable type-printer}
24945 @defmethod type_printer instantiate (self)
24946 This is called by @value{GDBN} at the start of type-printing. It is
24947 only called if the type printer is enabled. This method must return a
24948 new object that supplies a @code{recognize} method, as described below.
24952 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24953 will compute a list of type recognizers. This is done by iterating
24954 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24955 followed by the per-progspace type printers (@pxref{Progspaces In
24956 Python}), and finally the global type printers.
24958 @value{GDBN} will call the @code{instantiate} method of each enabled
24959 type printer. If this method returns @code{None}, then the result is
24960 ignored; otherwise, it is appended to the list of recognizers.
24962 Then, when @value{GDBN} is going to display a type name, it iterates
24963 over the list of recognizers. For each one, it calls the recognition
24964 function, stopping if the function returns a non-@code{None} value.
24965 The recognition function is defined as:
24967 @defmethod type_recognizer recognize (self, type)
24968 If @var{type} is not recognized, return @code{None}. Otherwise,
24969 return a string which is to be printed as the name of @var{type}.
24970 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24974 @value{GDBN} uses this two-pass approach so that type printers can
24975 efficiently cache information without holding on to it too long. For
24976 example, it can be convenient to look up type information in a type
24977 printer and hold it for a recognizer's lifetime; if a single pass were
24978 done then type printers would have to make use of the event system in
24979 order to avoid holding information that could become stale as the
24982 @node Frame Filter API
24983 @subsubsection Filtering Frames.
24984 @cindex frame filters api
24986 Frame filters are Python objects that manipulate the visibility of a
24987 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24990 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24991 commands (@pxref{GDB/MI}), those that return a collection of frames
24992 are affected. The commands that work with frame filters are:
24994 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24995 @code{-stack-list-frames}
24996 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24997 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24998 -stack-list-variables command}), @code{-stack-list-arguments}
24999 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
25000 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
25001 -stack-list-locals command}).
25003 A frame filter works by taking an iterator as an argument, applying
25004 actions to the contents of that iterator, and returning another
25005 iterator (or, possibly, the same iterator it was provided in the case
25006 where the filter does not perform any operations). Typically, frame
25007 filters utilize tools such as the Python's @code{itertools} module to
25008 work with and create new iterators from the source iterator.
25009 Regardless of how a filter chooses to apply actions, it must not alter
25010 the underlying @value{GDBN} frame or frames, or attempt to alter the
25011 call-stack within @value{GDBN}. This preserves data integrity within
25012 @value{GDBN}. Frame filters are executed on a priority basis and care
25013 should be taken that some frame filters may have been executed before,
25014 and that some frame filters will be executed after.
25016 An important consideration when designing frame filters, and well
25017 worth reflecting upon, is that frame filters should avoid unwinding
25018 the call stack if possible. Some stacks can run very deep, into the
25019 tens of thousands in some cases. To search every frame when a frame
25020 filter executes may be too expensive at that step. The frame filter
25021 cannot know how many frames it has to iterate over, and it may have to
25022 iterate through them all. This ends up duplicating effort as
25023 @value{GDBN} performs this iteration when it prints the frames. If
25024 the filter can defer unwinding frames until frame decorators are
25025 executed, after the last filter has executed, it should. @xref{Frame
25026 Decorator API}, for more information on decorators. Also, there are
25027 examples for both frame decorators and filters in later chapters.
25028 @xref{Writing a Frame Filter}, for more information.
25030 The Python dictionary @code{gdb.frame_filters} contains key/object
25031 pairings that comprise a frame filter. Frame filters in this
25032 dictionary are called @code{global} frame filters, and they are
25033 available when debugging all inferiors. These frame filters must
25034 register with the dictionary directly. In addition to the
25035 @code{global} dictionary, there are other dictionaries that are loaded
25036 with different inferiors via auto-loading (@pxref{Python
25037 Auto-loading}). The two other areas where frame filter dictionaries
25038 can be found are: @code{gdb.Progspace} which contains a
25039 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
25040 object which also contains a @code{frame_filters} dictionary
25043 When a command is executed from @value{GDBN} that is compatible with
25044 frame filters, @value{GDBN} combines the @code{global},
25045 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
25046 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
25047 several frames, and thus several object files, might be in use.
25048 @value{GDBN} then prunes any frame filter whose @code{enabled}
25049 attribute is @code{False}. This pruned list is then sorted according
25050 to the @code{priority} attribute in each filter.
25052 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
25053 creates an iterator which wraps each frame in the call stack in a
25054 @code{FrameDecorator} object, and calls each filter in order. The
25055 output from the previous filter will always be the input to the next
25058 Frame filters have a mandatory interface which each frame filter must
25059 implement, defined here:
25061 @defun FrameFilter.filter (iterator)
25062 @value{GDBN} will call this method on a frame filter when it has
25063 reached the order in the priority list for that filter.
25065 For example, if there are four frame filters:
25076 The order that the frame filters will be called is:
25079 Filter3 -> Filter2 -> Filter1 -> Filter4
25082 Note that the output from @code{Filter3} is passed to the input of
25083 @code{Filter2}, and so on.
25085 This @code{filter} method is passed a Python iterator. This iterator
25086 contains a sequence of frame decorators that wrap each
25087 @code{gdb.Frame}, or a frame decorator that wraps another frame
25088 decorator. The first filter that is executed in the sequence of frame
25089 filters will receive an iterator entirely comprised of default
25090 @code{FrameDecorator} objects. However, after each frame filter is
25091 executed, the previous frame filter may have wrapped some or all of
25092 the frame decorators with their own frame decorator. As frame
25093 decorators must also conform to a mandatory interface, these
25094 decorators can be assumed to act in a uniform manner (@pxref{Frame
25097 This method must return an object conforming to the Python iterator
25098 protocol. Each item in the iterator must be an object conforming to
25099 the frame decorator interface. If a frame filter does not wish to
25100 perform any operations on this iterator, it should return that
25101 iterator untouched.
25103 This method is not optional. If it does not exist, @value{GDBN} will
25104 raise and print an error.
25107 @defvar FrameFilter.name
25108 The @code{name} attribute must be Python string which contains the
25109 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25110 Management}). This attribute may contain any combination of letters
25111 or numbers. Care should be taken to ensure that it is unique. This
25112 attribute is mandatory.
25115 @defvar FrameFilter.enabled
25116 The @code{enabled} attribute must be Python boolean. This attribute
25117 indicates to @value{GDBN} whether the frame filter is enabled, and
25118 should be considered when frame filters are executed. If
25119 @code{enabled} is @code{True}, then the frame filter will be executed
25120 when any of the backtrace commands detailed earlier in this chapter
25121 are executed. If @code{enabled} is @code{False}, then the frame
25122 filter will not be executed. This attribute is mandatory.
25125 @defvar FrameFilter.priority
25126 The @code{priority} attribute must be Python integer. This attribute
25127 controls the order of execution in relation to other frame filters.
25128 There are no imposed limits on the range of @code{priority} other than
25129 it must be a valid integer. The higher the @code{priority} attribute,
25130 the sooner the frame filter will be executed in relation to other
25131 frame filters. Although @code{priority} can be negative, it is
25132 recommended practice to assume zero is the lowest priority that a
25133 frame filter can be assigned. Frame filters that have the same
25134 priority are executed in unsorted order in that priority slot. This
25135 attribute is mandatory.
25138 @node Frame Decorator API
25139 @subsubsection Decorating Frames.
25140 @cindex frame decorator api
25142 Frame decorators are sister objects to frame filters (@pxref{Frame
25143 Filter API}). Frame decorators are applied by a frame filter and can
25144 only be used in conjunction with frame filters.
25146 The purpose of a frame decorator is to customize the printed content
25147 of each @code{gdb.Frame} in commands where frame filters are executed.
25148 This concept is called decorating a frame. Frame decorators decorate
25149 a @code{gdb.Frame} with Python code contained within each API call.
25150 This separates the actual data contained in a @code{gdb.Frame} from
25151 the decorated data produced by a frame decorator. This abstraction is
25152 necessary to maintain integrity of the data contained in each
25155 Frame decorators have a mandatory interface, defined below.
25157 @value{GDBN} already contains a frame decorator called
25158 @code{FrameDecorator}. This contains substantial amounts of
25159 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25160 recommended that other frame decorators inherit and extend this
25161 object, and only to override the methods needed.
25163 @defun FrameDecorator.elided (self)
25165 The @code{elided} method groups frames together in a hierarchical
25166 system. An example would be an interpreter, where multiple low-level
25167 frames make up a single call in the interpreted language. In this
25168 example, the frame filter would elide the low-level frames and present
25169 a single high-level frame, representing the call in the interpreted
25170 language, to the user.
25172 The @code{elided} function must return an iterable and this iterable
25173 must contain the frames that are being elided wrapped in a suitable
25174 frame decorator. If no frames are being elided this function may
25175 return an empty iterable, or @code{None}. Elided frames are indented
25176 from normal frames in a @code{CLI} backtrace, or in the case of
25177 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25180 It is the frame filter's task to also filter out the elided frames from
25181 the source iterator. This will avoid printing the frame twice.
25184 @defun FrameDecorator.function (self)
25186 This method returns the name of the function in the frame that is to
25189 This method must return a Python string describing the function, or
25192 If this function returns @code{None}, @value{GDBN} will not print any
25193 data for this field.
25196 @defun FrameDecorator.address (self)
25198 This method returns the address of the frame that is to be printed.
25200 This method must return a Python numeric integer type of sufficient
25201 size to describe the address of the frame, or @code{None}.
25203 If this function returns a @code{None}, @value{GDBN} will not print
25204 any data for this field.
25207 @defun FrameDecorator.filename (self)
25209 This method returns the filename and path associated with this frame.
25211 This method must return a Python string containing the filename and
25212 the path to the object file backing the frame, or @code{None}.
25214 If this function returns a @code{None}, @value{GDBN} will not print
25215 any data for this field.
25218 @defun FrameDecorator.line (self):
25220 This method returns the line number associated with the current
25221 position within the function addressed by this frame.
25223 This method must return a Python integer type, or @code{None}.
25225 If this function returns a @code{None}, @value{GDBN} will not print
25226 any data for this field.
25229 @defun FrameDecorator.frame_args (self)
25230 @anchor{frame_args}
25232 This method must return an iterable, or @code{None}. Returning an
25233 empty iterable, or @code{None} means frame arguments will not be
25234 printed for this frame. This iterable must contain objects that
25235 implement two methods, described here.
25237 This object must implement a @code{argument} method which takes a
25238 single @code{self} parameter and must return a @code{gdb.Symbol}
25239 (@pxref{Symbols In Python}), or a Python string. The object must also
25240 implement a @code{value} method which takes a single @code{self}
25241 parameter and must return a @code{gdb.Value} (@pxref{Values From
25242 Inferior}), a Python value, or @code{None}. If the @code{value}
25243 method returns @code{None}, and the @code{argument} method returns a
25244 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25245 the @code{gdb.Symbol} automatically.
25250 class SymValueWrapper():
25252 def __init__(self, symbol, value):
25262 class SomeFrameDecorator()
25265 def frame_args(self):
25268 block = self.inferior_frame.block()
25272 # Iterate over all symbols in a block. Only add
25273 # symbols that are arguments.
25275 if not sym.is_argument:
25277 args.append(SymValueWrapper(sym,None))
25279 # Add example synthetic argument.
25280 args.append(SymValueWrapper(``foo'', 42))
25286 @defun FrameDecorator.frame_locals (self)
25288 This method must return an iterable or @code{None}. Returning an
25289 empty iterable, or @code{None} means frame local arguments will not be
25290 printed for this frame.
25292 The object interface, the description of the various strategies for
25293 reading frame locals, and the example are largely similar to those
25294 described in the @code{frame_args} function, (@pxref{frame_args,,The
25295 frame filter frame_args function}). Below is a modified example:
25298 class SomeFrameDecorator()
25301 def frame_locals(self):
25304 block = self.inferior_frame.block()
25308 # Iterate over all symbols in a block. Add all
25309 # symbols, except arguments.
25311 if sym.is_argument:
25313 vars.append(SymValueWrapper(sym,None))
25315 # Add an example of a synthetic local variable.
25316 vars.append(SymValueWrapper(``bar'', 99))
25322 @defun FrameDecorator.inferior_frame (self):
25324 This method must return the underlying @code{gdb.Frame} that this
25325 frame decorator is decorating. @value{GDBN} requires the underlying
25326 frame for internal frame information to determine how to print certain
25327 values when printing a frame.
25330 @node Writing a Frame Filter
25331 @subsubsection Writing a Frame Filter
25332 @cindex writing a frame filter
25334 There are three basic elements that a frame filter must implement: it
25335 must correctly implement the documented interface (@pxref{Frame Filter
25336 API}), it must register itself with @value{GDBN}, and finally, it must
25337 decide if it is to work on the data provided by @value{GDBN}. In all
25338 cases, whether it works on the iterator or not, each frame filter must
25339 return an iterator. A bare-bones frame filter follows the pattern in
25340 the following example.
25345 class FrameFilter():
25347 def __init__(self):
25348 # Frame filter attribute creation.
25350 # 'name' is the name of the filter that GDB will display.
25352 # 'priority' is the priority of the filter relative to other
25355 # 'enabled' is a boolean that indicates whether this filter is
25356 # enabled and should be executed.
25359 self.priority = 100
25360 self.enabled = True
25362 # Register this frame filter with the global frame_filters
25364 gdb.frame_filters[self.name] = self
25366 def filter(self, frame_iter):
25367 # Just return the iterator.
25371 The frame filter in the example above implements the three
25372 requirements for all frame filters. It implements the API, self
25373 registers, and makes a decision on the iterator (in this case, it just
25374 returns the iterator untouched).
25376 The first step is attribute creation and assignment, and as shown in
25377 the comments the filter assigns the following attributes: @code{name},
25378 @code{priority} and whether the filter should be enabled with the
25379 @code{enabled} attribute.
25381 The second step is registering the frame filter with the dictionary or
25382 dictionaries that the frame filter has interest in. As shown in the
25383 comments, this filter just registers itself with the global dictionary
25384 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25385 is a dictionary that is initialized in the @code{gdb} module when
25386 @value{GDBN} starts. What dictionary a filter registers with is an
25387 important consideration. Generally, if a filter is specific to a set
25388 of code, it should be registered either in the @code{objfile} or
25389 @code{progspace} dictionaries as they are specific to the program
25390 currently loaded in @value{GDBN}. The global dictionary is always
25391 present in @value{GDBN} and is never unloaded. Any filters registered
25392 with the global dictionary will exist until @value{GDBN} exits. To
25393 avoid filters that may conflict, it is generally better to register
25394 frame filters against the dictionaries that more closely align with
25395 the usage of the filter currently in question. @xref{Python
25396 Auto-loading}, for further information on auto-loading Python scripts.
25398 @value{GDBN} takes a hands-off approach to frame filter registration,
25399 therefore it is the frame filter's responsibility to ensure
25400 registration has occurred, and that any exceptions are handled
25401 appropriately. In particular, you may wish to handle exceptions
25402 relating to Python dictionary key uniqueness. It is mandatory that
25403 the dictionary key is the same as frame filter's @code{name}
25404 attribute. When a user manages frame filters (@pxref{Frame Filter
25405 Management}), the names @value{GDBN} will display are those contained
25406 in the @code{name} attribute.
25408 The final step of this example is the implementation of the
25409 @code{filter} method. As shown in the example comments, we define the
25410 @code{filter} method and note that the method must take an iterator,
25411 and also must return an iterator. In this bare-bones example, the
25412 frame filter is not very useful as it just returns the iterator
25413 untouched. However this is a valid operation for frame filters that
25414 have the @code{enabled} attribute set, but decide not to operate on
25417 In the next example, the frame filter operates on all frames and
25418 utilizes a frame decorator to perform some work on the frames.
25419 @xref{Frame Decorator API}, for further information on the frame
25420 decorator interface.
25422 This example works on inlined frames. It highlights frames which are
25423 inlined by tagging them with an ``[inlined]'' tag. By applying a
25424 frame decorator to all frames with the Python @code{itertools imap}
25425 method, the example defers actions to the frame decorator. Frame
25426 decorators are only processed when @value{GDBN} prints the backtrace.
25428 This introduces a new decision making topic: whether to perform
25429 decision making operations at the filtering step, or at the printing
25430 step. In this example's approach, it does not perform any filtering
25431 decisions at the filtering step beyond mapping a frame decorator to
25432 each frame. This allows the actual decision making to be performed
25433 when each frame is printed. This is an important consideration, and
25434 well worth reflecting upon when designing a frame filter. An issue
25435 that frame filters should avoid is unwinding the stack if possible.
25436 Some stacks can run very deep, into the tens of thousands in some
25437 cases. To search every frame to determine if it is inlined ahead of
25438 time may be too expensive at the filtering step. The frame filter
25439 cannot know how many frames it has to iterate over, and it would have
25440 to iterate through them all. This ends up duplicating effort as
25441 @value{GDBN} performs this iteration when it prints the frames.
25443 In this example decision making can be deferred to the printing step.
25444 As each frame is printed, the frame decorator can examine each frame
25445 in turn when @value{GDBN} iterates. From a performance viewpoint,
25446 this is the most appropriate decision to make as it avoids duplicating
25447 the effort that the printing step would undertake anyway. Also, if
25448 there are many frame filters unwinding the stack during filtering, it
25449 can substantially delay the printing of the backtrace which will
25450 result in large memory usage, and a poor user experience.
25453 class InlineFilter():
25455 def __init__(self):
25456 self.name = "InlinedFrameFilter"
25457 self.priority = 100
25458 self.enabled = True
25459 gdb.frame_filters[self.name] = self
25461 def filter(self, frame_iter):
25462 frame_iter = itertools.imap(InlinedFrameDecorator,
25467 This frame filter is somewhat similar to the earlier example, except
25468 that the @code{filter} method applies a frame decorator object called
25469 @code{InlinedFrameDecorator} to each element in the iterator. The
25470 @code{imap} Python method is light-weight. It does not proactively
25471 iterate over the iterator, but rather creates a new iterator which
25472 wraps the existing one.
25474 Below is the frame decorator for this example.
25477 class InlinedFrameDecorator(FrameDecorator):
25479 def __init__(self, fobj):
25480 super(InlinedFrameDecorator, self).__init__(fobj)
25482 def function(self):
25483 frame = fobj.inferior_frame()
25484 name = str(frame.name())
25486 if frame.type() == gdb.INLINE_FRAME:
25487 name = name + " [inlined]"
25492 This frame decorator only defines and overrides the @code{function}
25493 method. It lets the supplied @code{FrameDecorator}, which is shipped
25494 with @value{GDBN}, perform the other work associated with printing
25497 The combination of these two objects create this output from a
25501 #0 0x004004e0 in bar () at inline.c:11
25502 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25503 #2 0x00400566 in main () at inline.c:31
25506 So in the case of this example, a frame decorator is applied to all
25507 frames, regardless of whether they may be inlined or not. As
25508 @value{GDBN} iterates over the iterator produced by the frame filters,
25509 @value{GDBN} executes each frame decorator which then makes a decision
25510 on what to print in the @code{function} callback. Using a strategy
25511 like this is a way to defer decisions on the frame content to printing
25514 @subheading Eliding Frames
25516 It might be that the above example is not desirable for representing
25517 inlined frames, and a hierarchical approach may be preferred. If we
25518 want to hierarchically represent frames, the @code{elided} frame
25519 decorator interface might be preferable.
25521 This example approaches the issue with the @code{elided} method. This
25522 example is quite long, but very simplistic. It is out-of-scope for
25523 this section to write a complete example that comprehensively covers
25524 all approaches of finding and printing inlined frames. However, this
25525 example illustrates the approach an author might use.
25527 This example comprises of three sections.
25530 class InlineFrameFilter():
25532 def __init__(self):
25533 self.name = "InlinedFrameFilter"
25534 self.priority = 100
25535 self.enabled = True
25536 gdb.frame_filters[self.name] = self
25538 def filter(self, frame_iter):
25539 return ElidingInlineIterator(frame_iter)
25542 This frame filter is very similar to the other examples. The only
25543 difference is this frame filter is wrapping the iterator provided to
25544 it (@code{frame_iter}) with a custom iterator called
25545 @code{ElidingInlineIterator}. This again defers actions to when
25546 @value{GDBN} prints the backtrace, as the iterator is not traversed
25549 The iterator for this example is as follows. It is in this section of
25550 the example where decisions are made on the content of the backtrace.
25553 class ElidingInlineIterator:
25554 def __init__(self, ii):
25555 self.input_iterator = ii
25557 def __iter__(self):
25561 frame = next(self.input_iterator)
25563 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25567 eliding_frame = next(self.input_iterator)
25568 except StopIteration:
25570 return ElidingFrameDecorator(eliding_frame, [frame])
25573 This iterator implements the Python iterator protocol. When the
25574 @code{next} function is called (when @value{GDBN} prints each frame),
25575 the iterator checks if this frame decorator, @code{frame}, is wrapping
25576 an inlined frame. If it is not, it returns the existing frame decorator
25577 untouched. If it is wrapping an inlined frame, it assumes that the
25578 inlined frame was contained within the next oldest frame,
25579 @code{eliding_frame}, which it fetches. It then creates and returns a
25580 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25581 elided frame, and the eliding frame.
25584 class ElidingInlineDecorator(FrameDecorator):
25586 def __init__(self, frame, elided_frames):
25587 super(ElidingInlineDecorator, self).__init__(frame)
25589 self.elided_frames = elided_frames
25592 return iter(self.elided_frames)
25595 This frame decorator overrides one function and returns the inlined
25596 frame in the @code{elided} method. As before it lets
25597 @code{FrameDecorator} do the rest of the work involved in printing
25598 this frame. This produces the following output.
25601 #0 0x004004e0 in bar () at inline.c:11
25602 #2 0x00400529 in main () at inline.c:25
25603 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25606 In that output, @code{max} which has been inlined into @code{main} is
25607 printed hierarchically. Another approach would be to combine the
25608 @code{function} method, and the @code{elided} method to both print a
25609 marker in the inlined frame, and also show the hierarchical
25612 @node Inferiors In Python
25613 @subsubsection Inferiors In Python
25614 @cindex inferiors in Python
25616 @findex gdb.Inferior
25617 Programs which are being run under @value{GDBN} are called inferiors
25618 (@pxref{Inferiors and Programs}). Python scripts can access
25619 information about and manipulate inferiors controlled by @value{GDBN}
25620 via objects of the @code{gdb.Inferior} class.
25622 The following inferior-related functions are available in the @code{gdb}
25625 @defun gdb.inferiors ()
25626 Return a tuple containing all inferior objects.
25629 @defun gdb.selected_inferior ()
25630 Return an object representing the current inferior.
25633 A @code{gdb.Inferior} object has the following attributes:
25635 @defvar Inferior.num
25636 ID of inferior, as assigned by GDB.
25639 @defvar Inferior.pid
25640 Process ID of the inferior, as assigned by the underlying operating
25644 @defvar Inferior.was_attached
25645 Boolean signaling whether the inferior was created using `attach', or
25646 started by @value{GDBN} itself.
25649 A @code{gdb.Inferior} object has the following methods:
25651 @defun Inferior.is_valid ()
25652 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25653 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25654 if the inferior no longer exists within @value{GDBN}. All other
25655 @code{gdb.Inferior} methods will throw an exception if it is invalid
25656 at the time the method is called.
25659 @defun Inferior.threads ()
25660 This method returns a tuple holding all the threads which are valid
25661 when it is called. If there are no valid threads, the method will
25662 return an empty tuple.
25665 @findex Inferior.read_memory
25666 @defun Inferior.read_memory (address, length)
25667 Read @var{length} bytes of memory from the inferior, starting at
25668 @var{address}. Returns a buffer object, which behaves much like an array
25669 or a string. It can be modified and given to the
25670 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25671 value is a @code{memoryview} object.
25674 @findex Inferior.write_memory
25675 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25676 Write the contents of @var{buffer} to the inferior, starting at
25677 @var{address}. The @var{buffer} parameter must be a Python object
25678 which supports the buffer protocol, i.e., a string, an array or the
25679 object returned from @code{Inferior.read_memory}. If given, @var{length}
25680 determines the number of bytes from @var{buffer} to be written.
25683 @findex gdb.search_memory
25684 @defun Inferior.search_memory (address, length, pattern)
25685 Search a region of the inferior memory starting at @var{address} with
25686 the given @var{length} using the search pattern supplied in
25687 @var{pattern}. The @var{pattern} 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{gdb.read_memory}. Returns a Python @code{Long}
25690 containing the address where the pattern was found, or @code{None} if
25691 the pattern could not be found.
25694 @node Events In Python
25695 @subsubsection Events In Python
25696 @cindex inferior events in Python
25698 @value{GDBN} provides a general event facility so that Python code can be
25699 notified of various state changes, particularly changes that occur in
25702 An @dfn{event} is just an object that describes some state change. The
25703 type of the object and its attributes will vary depending on the details
25704 of the change. All the existing events are described below.
25706 In order to be notified of an event, you must register an event handler
25707 with an @dfn{event registry}. An event registry is an object in the
25708 @code{gdb.events} module which dispatches particular events. A registry
25709 provides methods to register and unregister event handlers:
25711 @defun EventRegistry.connect (object)
25712 Add the given callable @var{object} to the registry. This object will be
25713 called when an event corresponding to this registry occurs.
25716 @defun EventRegistry.disconnect (object)
25717 Remove the given @var{object} from the registry. Once removed, the object
25718 will no longer receive notifications of events.
25721 Here is an example:
25724 def exit_handler (event):
25725 print "event type: exit"
25726 print "exit code: %d" % (event.exit_code)
25728 gdb.events.exited.connect (exit_handler)
25731 In the above example we connect our handler @code{exit_handler} to the
25732 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25733 called when the inferior exits. The argument @dfn{event} in this example is
25734 of type @code{gdb.ExitedEvent}. As you can see in the example the
25735 @code{ExitedEvent} object has an attribute which indicates the exit code of
25738 The following is a listing of the event registries that are available and
25739 details of the events they emit:
25744 Emits @code{gdb.ThreadEvent}.
25746 Some events can be thread specific when @value{GDBN} is running in non-stop
25747 mode. When represented in Python, these events all extend
25748 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25749 events which are emitted by this or other modules might extend this event.
25750 Examples of these events are @code{gdb.BreakpointEvent} and
25751 @code{gdb.ContinueEvent}.
25753 @defvar ThreadEvent.inferior_thread
25754 In non-stop mode this attribute will be set to the specific thread which was
25755 involved in the emitted event. Otherwise, it will be set to @code{None}.
25758 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25760 This event indicates that the inferior has been continued after a stop. For
25761 inherited attribute refer to @code{gdb.ThreadEvent} above.
25763 @item events.exited
25764 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25765 @code{events.ExitedEvent} has two attributes:
25766 @defvar ExitedEvent.exit_code
25767 An integer representing the exit code, if available, which the inferior
25768 has returned. (The exit code could be unavailable if, for example,
25769 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25770 the attribute does not exist.
25772 @defvar ExitedEvent inferior
25773 A reference to the inferior which triggered the @code{exited} event.
25777 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25779 Indicates that the inferior has stopped. All events emitted by this registry
25780 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25781 will indicate the stopped thread when @value{GDBN} is running in non-stop
25782 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25784 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25786 This event indicates that the inferior or one of its threads has received as
25787 signal. @code{gdb.SignalEvent} has the following attributes:
25789 @defvar SignalEvent.stop_signal
25790 A string representing the signal received by the inferior. A list of possible
25791 signal values can be obtained by running the command @code{info signals} in
25792 the @value{GDBN} command prompt.
25795 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25797 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25798 been hit, and has the following attributes:
25800 @defvar BreakpointEvent.breakpoints
25801 A sequence containing references to all the breakpoints (type
25802 @code{gdb.Breakpoint}) that were hit.
25803 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25805 @defvar BreakpointEvent.breakpoint
25806 A reference to the first breakpoint that was hit.
25807 This function is maintained for backward compatibility and is now deprecated
25808 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25811 @item events.new_objfile
25812 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25813 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25815 @defvar NewObjFileEvent.new_objfile
25816 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25817 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25822 @node Threads In Python
25823 @subsubsection Threads In Python
25824 @cindex threads in python
25826 @findex gdb.InferiorThread
25827 Python scripts can access information about, and manipulate inferior threads
25828 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25830 The following thread-related functions are available in the @code{gdb}
25833 @findex gdb.selected_thread
25834 @defun gdb.selected_thread ()
25835 This function returns the thread object for the selected thread. If there
25836 is no selected thread, this will return @code{None}.
25839 A @code{gdb.InferiorThread} object has the following attributes:
25841 @defvar InferiorThread.name
25842 The name of the thread. If the user specified a name using
25843 @code{thread name}, then this returns that name. Otherwise, if an
25844 OS-supplied name is available, then it is returned. Otherwise, this
25845 returns @code{None}.
25847 This attribute can be assigned to. The new value must be a string
25848 object, which sets the new name, or @code{None}, which removes any
25849 user-specified thread name.
25852 @defvar InferiorThread.num
25853 ID of the thread, as assigned by GDB.
25856 @defvar InferiorThread.ptid
25857 ID of the thread, as assigned by the operating system. This attribute is a
25858 tuple containing three integers. The first is the Process ID (PID); the second
25859 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25860 Either the LWPID or TID may be 0, which indicates that the operating system
25861 does not use that identifier.
25864 A @code{gdb.InferiorThread} object has the following methods:
25866 @defun InferiorThread.is_valid ()
25867 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25868 @code{False} if not. A @code{gdb.InferiorThread} object will become
25869 invalid if the thread exits, or the inferior that the thread belongs
25870 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25871 exception if it is invalid at the time the method is called.
25874 @defun InferiorThread.switch ()
25875 This changes @value{GDBN}'s currently selected thread to the one represented
25879 @defun InferiorThread.is_stopped ()
25880 Return a Boolean indicating whether the thread is stopped.
25883 @defun InferiorThread.is_running ()
25884 Return a Boolean indicating whether the thread is running.
25887 @defun InferiorThread.is_exited ()
25888 Return a Boolean indicating whether the thread is exited.
25891 @node Commands In Python
25892 @subsubsection Commands In Python
25894 @cindex commands in python
25895 @cindex python commands
25896 You can implement new @value{GDBN} CLI commands in Python. A CLI
25897 command is implemented using an instance of the @code{gdb.Command}
25898 class, most commonly using a subclass.
25900 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25901 The object initializer for @code{Command} registers the new command
25902 with @value{GDBN}. This initializer is normally invoked from the
25903 subclass' own @code{__init__} method.
25905 @var{name} is the name of the command. If @var{name} consists of
25906 multiple words, then the initial words are looked for as prefix
25907 commands. In this case, if one of the prefix commands does not exist,
25908 an exception is raised.
25910 There is no support for multi-line commands.
25912 @var{command_class} should be one of the @samp{COMMAND_} constants
25913 defined below. This argument tells @value{GDBN} how to categorize the
25914 new command in the help system.
25916 @var{completer_class} is an optional argument. If given, it should be
25917 one of the @samp{COMPLETE_} constants defined below. This argument
25918 tells @value{GDBN} how to perform completion for this command. If not
25919 given, @value{GDBN} will attempt to complete using the object's
25920 @code{complete} method (see below); if no such method is found, an
25921 error will occur when completion is attempted.
25923 @var{prefix} is an optional argument. If @code{True}, then the new
25924 command is a prefix command; sub-commands of this command may be
25927 The help text for the new command is taken from the Python
25928 documentation string for the command's class, if there is one. If no
25929 documentation string is provided, the default value ``This command is
25930 not documented.'' is used.
25933 @cindex don't repeat Python command
25934 @defun Command.dont_repeat ()
25935 By default, a @value{GDBN} command is repeated when the user enters a
25936 blank line at the command prompt. A command can suppress this
25937 behavior by invoking the @code{dont_repeat} method. This is similar
25938 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25941 @defun Command.invoke (argument, from_tty)
25942 This method is called by @value{GDBN} when this command is invoked.
25944 @var{argument} is a string. It is the argument to the command, after
25945 leading and trailing whitespace has been stripped.
25947 @var{from_tty} is a boolean argument. When true, this means that the
25948 command was entered by the user at the terminal; when false it means
25949 that the command came from elsewhere.
25951 If this method throws an exception, it is turned into a @value{GDBN}
25952 @code{error} call. Otherwise, the return value is ignored.
25954 @findex gdb.string_to_argv
25955 To break @var{argument} up into an argv-like string use
25956 @code{gdb.string_to_argv}. This function behaves identically to
25957 @value{GDBN}'s internal argument lexer @code{buildargv}.
25958 It is recommended to use this for consistency.
25959 Arguments are separated by spaces and may be quoted.
25963 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25964 ['1', '2 "3', '4 "5', "6 '7"]
25969 @cindex completion of Python commands
25970 @defun Command.complete (text, word)
25971 This method is called by @value{GDBN} when the user attempts
25972 completion on this command. All forms of completion are handled by
25973 this method, that is, the @key{TAB} and @key{M-?} key bindings
25974 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25977 The arguments @var{text} and @var{word} are both strings. @var{text}
25978 holds the complete command line up to the cursor's location.
25979 @var{word} holds the last word of the command line; this is computed
25980 using a word-breaking heuristic.
25982 The @code{complete} method can return several values:
25985 If the return value is a sequence, the contents of the sequence are
25986 used as the completions. It is up to @code{complete} to ensure that the
25987 contents actually do complete the word. A zero-length sequence is
25988 allowed, it means that there were no completions available. Only
25989 string elements of the sequence are used; other elements in the
25990 sequence are ignored.
25993 If the return value is one of the @samp{COMPLETE_} constants defined
25994 below, then the corresponding @value{GDBN}-internal completion
25995 function is invoked, and its result is used.
25998 All other results are treated as though there were no available
26003 When a new command is registered, it must be declared as a member of
26004 some general class of commands. This is used to classify top-level
26005 commands in the on-line help system; note that prefix commands are not
26006 listed under their own category but rather that of their top-level
26007 command. The available classifications are represented by constants
26008 defined in the @code{gdb} module:
26011 @findex COMMAND_NONE
26012 @findex gdb.COMMAND_NONE
26013 @item gdb.COMMAND_NONE
26014 The command does not belong to any particular class. A command in
26015 this category will not be displayed in any of the help categories.
26017 @findex COMMAND_RUNNING
26018 @findex gdb.COMMAND_RUNNING
26019 @item gdb.COMMAND_RUNNING
26020 The command is related to running the inferior. For example,
26021 @code{start}, @code{step}, and @code{continue} are in this category.
26022 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
26023 commands in this category.
26025 @findex COMMAND_DATA
26026 @findex gdb.COMMAND_DATA
26027 @item gdb.COMMAND_DATA
26028 The command is related to data or variables. For example,
26029 @code{call}, @code{find}, and @code{print} are in this category. Type
26030 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
26033 @findex COMMAND_STACK
26034 @findex gdb.COMMAND_STACK
26035 @item gdb.COMMAND_STACK
26036 The command has to do with manipulation of the stack. For example,
26037 @code{backtrace}, @code{frame}, and @code{return} are in this
26038 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
26039 list of commands in this category.
26041 @findex COMMAND_FILES
26042 @findex gdb.COMMAND_FILES
26043 @item gdb.COMMAND_FILES
26044 This class is used for file-related commands. For example,
26045 @code{file}, @code{list} and @code{section} are in this category.
26046 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
26047 commands in this category.
26049 @findex COMMAND_SUPPORT
26050 @findex gdb.COMMAND_SUPPORT
26051 @item gdb.COMMAND_SUPPORT
26052 This should be used for ``support facilities'', generally meaning
26053 things that are useful to the user when interacting with @value{GDBN},
26054 but not related to the state of the inferior. For example,
26055 @code{help}, @code{make}, and @code{shell} are in this category. Type
26056 @kbd{help support} at the @value{GDBN} prompt to see a list of
26057 commands in this category.
26059 @findex COMMAND_STATUS
26060 @findex gdb.COMMAND_STATUS
26061 @item gdb.COMMAND_STATUS
26062 The command is an @samp{info}-related command, that is, related to the
26063 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
26064 and @code{show} are in this category. Type @kbd{help status} at the
26065 @value{GDBN} prompt to see a list of commands in this category.
26067 @findex COMMAND_BREAKPOINTS
26068 @findex gdb.COMMAND_BREAKPOINTS
26069 @item gdb.COMMAND_BREAKPOINTS
26070 The command has to do with breakpoints. For example, @code{break},
26071 @code{clear}, and @code{delete} are in this category. Type @kbd{help
26072 breakpoints} at the @value{GDBN} prompt to see a list of commands in
26075 @findex COMMAND_TRACEPOINTS
26076 @findex gdb.COMMAND_TRACEPOINTS
26077 @item gdb.COMMAND_TRACEPOINTS
26078 The command has to do with tracepoints. For example, @code{trace},
26079 @code{actions}, and @code{tfind} are in this category. Type
26080 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
26081 commands in this category.
26083 @findex COMMAND_USER
26084 @findex gdb.COMMAND_USER
26085 @item gdb.COMMAND_USER
26086 The command is a general purpose command for the user, and typically
26087 does not fit in one of the other categories.
26088 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26089 a list of commands in this category, as well as the list of gdb macros
26090 (@pxref{Sequences}).
26092 @findex COMMAND_OBSCURE
26093 @findex gdb.COMMAND_OBSCURE
26094 @item gdb.COMMAND_OBSCURE
26095 The command is only used in unusual circumstances, or is not of
26096 general interest to users. For example, @code{checkpoint},
26097 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26098 obscure} at the @value{GDBN} prompt to see a list of commands in this
26101 @findex COMMAND_MAINTENANCE
26102 @findex gdb.COMMAND_MAINTENANCE
26103 @item gdb.COMMAND_MAINTENANCE
26104 The command is only useful to @value{GDBN} maintainers. The
26105 @code{maintenance} and @code{flushregs} commands are in this category.
26106 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26107 commands in this category.
26110 A new command can use a predefined completion function, either by
26111 specifying it via an argument at initialization, or by returning it
26112 from the @code{complete} method. These predefined completion
26113 constants are all defined in the @code{gdb} module:
26116 @findex COMPLETE_NONE
26117 @findex gdb.COMPLETE_NONE
26118 @item gdb.COMPLETE_NONE
26119 This constant means that no completion should be done.
26121 @findex COMPLETE_FILENAME
26122 @findex gdb.COMPLETE_FILENAME
26123 @item gdb.COMPLETE_FILENAME
26124 This constant means that filename completion should be performed.
26126 @findex COMPLETE_LOCATION
26127 @findex gdb.COMPLETE_LOCATION
26128 @item gdb.COMPLETE_LOCATION
26129 This constant means that location completion should be done.
26130 @xref{Specify Location}.
26132 @findex COMPLETE_COMMAND
26133 @findex gdb.COMPLETE_COMMAND
26134 @item gdb.COMPLETE_COMMAND
26135 This constant means that completion should examine @value{GDBN}
26138 @findex COMPLETE_SYMBOL
26139 @findex gdb.COMPLETE_SYMBOL
26140 @item gdb.COMPLETE_SYMBOL
26141 This constant means that completion should be done using symbol names
26144 @findex COMPLETE_EXPRESSION
26145 @findex gdb.COMPLETE_EXPRESSION
26146 @item gdb.COMPLETE_EXPRESSION
26147 This constant means that completion should be done on expressions.
26148 Often this means completing on symbol names, but some language
26149 parsers also have support for completing on field names.
26152 The following code snippet shows how a trivial CLI command can be
26153 implemented in Python:
26156 class HelloWorld (gdb.Command):
26157 """Greet the whole world."""
26159 def __init__ (self):
26160 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26162 def invoke (self, arg, from_tty):
26163 print "Hello, World!"
26168 The last line instantiates the class, and is necessary to trigger the
26169 registration of the command with @value{GDBN}. Depending on how the
26170 Python code is read into @value{GDBN}, you may need to import the
26171 @code{gdb} module explicitly.
26173 @node Parameters In Python
26174 @subsubsection Parameters In Python
26176 @cindex parameters in python
26177 @cindex python parameters
26178 @tindex gdb.Parameter
26180 You can implement new @value{GDBN} parameters using Python. A new
26181 parameter is implemented as an instance of the @code{gdb.Parameter}
26184 Parameters are exposed to the user via the @code{set} and
26185 @code{show} commands. @xref{Help}.
26187 There are many parameters that already exist and can be set in
26188 @value{GDBN}. Two examples are: @code{set follow fork} and
26189 @code{set charset}. Setting these parameters influences certain
26190 behavior in @value{GDBN}. Similarly, you can define parameters that
26191 can be used to influence behavior in custom Python scripts and commands.
26193 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26194 The object initializer for @code{Parameter} registers the new
26195 parameter with @value{GDBN}. This initializer is normally invoked
26196 from the subclass' own @code{__init__} method.
26198 @var{name} is the name of the new parameter. If @var{name} consists
26199 of multiple words, then the initial words are looked for as prefix
26200 parameters. An example of this can be illustrated with the
26201 @code{set print} set of parameters. If @var{name} is
26202 @code{print foo}, then @code{print} will be searched as the prefix
26203 parameter. In this case the parameter can subsequently be accessed in
26204 @value{GDBN} as @code{set print foo}.
26206 If @var{name} consists of multiple words, and no prefix parameter group
26207 can be found, an exception is raised.
26209 @var{command-class} should be one of the @samp{COMMAND_} constants
26210 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26211 categorize the new parameter in the help system.
26213 @var{parameter-class} should be one of the @samp{PARAM_} constants
26214 defined below. This argument tells @value{GDBN} the type of the new
26215 parameter; this information is used for input validation and
26218 If @var{parameter-class} is @code{PARAM_ENUM}, then
26219 @var{enum-sequence} must be a sequence of strings. These strings
26220 represent the possible values for the parameter.
26222 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26223 of a fourth argument will cause an exception to be thrown.
26225 The help text for the new parameter is taken from the Python
26226 documentation string for the parameter's class, if there is one. If
26227 there is no documentation string, a default value is used.
26230 @defvar Parameter.set_doc
26231 If this attribute exists, and is a string, then its value is used as
26232 the help text for this parameter's @code{set} command. The value is
26233 examined when @code{Parameter.__init__} is invoked; subsequent changes
26237 @defvar Parameter.show_doc
26238 If this attribute exists, and is a string, then its value is used as
26239 the help text for this parameter's @code{show} command. The value is
26240 examined when @code{Parameter.__init__} is invoked; subsequent changes
26244 @defvar Parameter.value
26245 The @code{value} attribute holds the underlying value of the
26246 parameter. It can be read and assigned to just as any other
26247 attribute. @value{GDBN} does validation when assignments are made.
26250 There are two methods that should be implemented in any
26251 @code{Parameter} class. These are:
26253 @defun Parameter.get_set_string (self)
26254 @value{GDBN} will call this method when a @var{parameter}'s value has
26255 been changed via the @code{set} API (for example, @kbd{set foo off}).
26256 The @code{value} attribute has already been populated with the new
26257 value and may be used in output. This method must return a string.
26260 @defun Parameter.get_show_string (self, svalue)
26261 @value{GDBN} will call this method when a @var{parameter}'s
26262 @code{show} API has been invoked (for example, @kbd{show foo}). The
26263 argument @code{svalue} receives the string representation of the
26264 current value. This method must return a string.
26267 When a new parameter is defined, its type must be specified. The
26268 available types are represented by constants defined in the @code{gdb}
26272 @findex PARAM_BOOLEAN
26273 @findex gdb.PARAM_BOOLEAN
26274 @item gdb.PARAM_BOOLEAN
26275 The value is a plain boolean. The Python boolean values, @code{True}
26276 and @code{False} are the only valid values.
26278 @findex PARAM_AUTO_BOOLEAN
26279 @findex gdb.PARAM_AUTO_BOOLEAN
26280 @item gdb.PARAM_AUTO_BOOLEAN
26281 The value has three possible states: true, false, and @samp{auto}. In
26282 Python, true and false are represented using boolean constants, and
26283 @samp{auto} is represented using @code{None}.
26285 @findex PARAM_UINTEGER
26286 @findex gdb.PARAM_UINTEGER
26287 @item gdb.PARAM_UINTEGER
26288 The value is an unsigned integer. The value of 0 should be
26289 interpreted to mean ``unlimited''.
26291 @findex PARAM_INTEGER
26292 @findex gdb.PARAM_INTEGER
26293 @item gdb.PARAM_INTEGER
26294 The value is a signed integer. The value of 0 should be interpreted
26295 to mean ``unlimited''.
26297 @findex PARAM_STRING
26298 @findex gdb.PARAM_STRING
26299 @item gdb.PARAM_STRING
26300 The value is a string. When the user modifies the string, any escape
26301 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26302 translated into corresponding characters and encoded into the current
26305 @findex PARAM_STRING_NOESCAPE
26306 @findex gdb.PARAM_STRING_NOESCAPE
26307 @item gdb.PARAM_STRING_NOESCAPE
26308 The value is a string. When the user modifies the string, escapes are
26309 passed through untranslated.
26311 @findex PARAM_OPTIONAL_FILENAME
26312 @findex gdb.PARAM_OPTIONAL_FILENAME
26313 @item gdb.PARAM_OPTIONAL_FILENAME
26314 The value is a either a filename (a string), or @code{None}.
26316 @findex PARAM_FILENAME
26317 @findex gdb.PARAM_FILENAME
26318 @item gdb.PARAM_FILENAME
26319 The value is a filename. This is just like
26320 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26322 @findex PARAM_ZINTEGER
26323 @findex gdb.PARAM_ZINTEGER
26324 @item gdb.PARAM_ZINTEGER
26325 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26326 is interpreted as itself.
26329 @findex gdb.PARAM_ENUM
26330 @item gdb.PARAM_ENUM
26331 The value is a string, which must be one of a collection string
26332 constants provided when the parameter is created.
26335 @node Functions In Python
26336 @subsubsection Writing new convenience functions
26338 @cindex writing convenience functions
26339 @cindex convenience functions in python
26340 @cindex python convenience functions
26341 @tindex gdb.Function
26343 You can implement new convenience functions (@pxref{Convenience Vars})
26344 in Python. A convenience function is an instance of a subclass of the
26345 class @code{gdb.Function}.
26347 @defun Function.__init__ (name)
26348 The initializer for @code{Function} registers the new function with
26349 @value{GDBN}. The argument @var{name} is the name of the function,
26350 a string. The function will be visible to the user as a convenience
26351 variable of type @code{internal function}, whose name is the same as
26352 the given @var{name}.
26354 The documentation for the new function is taken from the documentation
26355 string for the new class.
26358 @defun Function.invoke (@var{*args})
26359 When a convenience function is evaluated, its arguments are converted
26360 to instances of @code{gdb.Value}, and then the function's
26361 @code{invoke} method is called. Note that @value{GDBN} does not
26362 predetermine the arity of convenience functions. Instead, all
26363 available arguments are passed to @code{invoke}, following the
26364 standard Python calling convention. In particular, a convenience
26365 function can have default values for parameters without ill effect.
26367 The return value of this method is used as its value in the enclosing
26368 expression. If an ordinary Python value is returned, it is converted
26369 to a @code{gdb.Value} following the usual rules.
26372 The following code snippet shows how a trivial convenience function can
26373 be implemented in Python:
26376 class Greet (gdb.Function):
26377 """Return string to greet someone.
26378 Takes a name as argument."""
26380 def __init__ (self):
26381 super (Greet, self).__init__ ("greet")
26383 def invoke (self, name):
26384 return "Hello, %s!" % name.string ()
26389 The last line instantiates the class, and is necessary to trigger the
26390 registration of the function with @value{GDBN}. Depending on how the
26391 Python code is read into @value{GDBN}, you may need to import the
26392 @code{gdb} module explicitly.
26394 Now you can use the function in an expression:
26397 (gdb) print $greet("Bob")
26401 @node Progspaces In Python
26402 @subsubsection Program Spaces In Python
26404 @cindex progspaces in python
26405 @tindex gdb.Progspace
26407 A program space, or @dfn{progspace}, represents a symbolic view
26408 of an address space.
26409 It consists of all of the objfiles of the program.
26410 @xref{Objfiles In Python}.
26411 @xref{Inferiors and Programs, program spaces}, for more details
26412 about program spaces.
26414 The following progspace-related functions are available in the
26417 @findex gdb.current_progspace
26418 @defun gdb.current_progspace ()
26419 This function returns the program space of the currently selected inferior.
26420 @xref{Inferiors and Programs}.
26423 @findex gdb.progspaces
26424 @defun gdb.progspaces ()
26425 Return a sequence of all the progspaces currently known to @value{GDBN}.
26428 Each progspace is represented by an instance of the @code{gdb.Progspace}
26431 @defvar Progspace.filename
26432 The file name of the progspace as a string.
26435 @defvar Progspace.pretty_printers
26436 The @code{pretty_printers} attribute is a list of functions. It is
26437 used to look up pretty-printers. A @code{Value} is passed to each
26438 function in order; if the function returns @code{None}, then the
26439 search continues. Otherwise, the return value should be an object
26440 which is used to format the value. @xref{Pretty Printing API}, for more
26444 @defvar Progspace.type_printers
26445 The @code{type_printers} attribute is a list of type printer objects.
26446 @xref{Type Printing API}, for more information.
26449 @defvar Progspace.frame_filters
26450 The @code{frame_filters} attribute is a dictionary of frame filter
26451 objects. @xref{Frame Filter API}, for more information.
26454 @node Objfiles In Python
26455 @subsubsection Objfiles In Python
26457 @cindex objfiles in python
26458 @tindex gdb.Objfile
26460 @value{GDBN} loads symbols for an inferior from various
26461 symbol-containing files (@pxref{Files}). These include the primary
26462 executable file, any shared libraries used by the inferior, and any
26463 separate debug info files (@pxref{Separate Debug Files}).
26464 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26466 The following objfile-related functions are available in the
26469 @findex gdb.current_objfile
26470 @defun gdb.current_objfile ()
26471 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26472 sets the ``current objfile'' to the corresponding objfile. This
26473 function returns the current objfile. If there is no current objfile,
26474 this function returns @code{None}.
26477 @findex gdb.objfiles
26478 @defun gdb.objfiles ()
26479 Return a sequence of all the objfiles current known to @value{GDBN}.
26480 @xref{Objfiles In Python}.
26483 Each objfile is represented by an instance of the @code{gdb.Objfile}
26486 @defvar Objfile.filename
26487 The file name of the objfile as a string.
26490 @defvar Objfile.pretty_printers
26491 The @code{pretty_printers} attribute is a list of functions. It is
26492 used to look up pretty-printers. A @code{Value} is passed to each
26493 function in order; if the function returns @code{None}, then the
26494 search continues. Otherwise, the return value should be an object
26495 which is used to format the value. @xref{Pretty Printing API}, for more
26499 @defvar Objfile.type_printers
26500 The @code{type_printers} attribute is a list of type printer objects.
26501 @xref{Type Printing API}, for more information.
26504 @defvar Objfile.frame_filters
26505 The @code{frame_filters} attribute is a dictionary of frame filter
26506 objects. @xref{Frame Filter API}, for more information.
26509 A @code{gdb.Objfile} object has the following methods:
26511 @defun Objfile.is_valid ()
26512 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26513 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26514 if the object file it refers to is not loaded in @value{GDBN} any
26515 longer. All other @code{gdb.Objfile} methods will throw an exception
26516 if it is invalid at the time the method is called.
26519 @node Frames In Python
26520 @subsubsection Accessing inferior stack frames from Python.
26522 @cindex frames in python
26523 When the debugged program stops, @value{GDBN} is able to analyze its call
26524 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26525 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26526 while its corresponding frame exists in the inferior's stack. If you try
26527 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26528 exception (@pxref{Exception Handling}).
26530 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26534 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26538 The following frame-related functions are available in the @code{gdb} module:
26540 @findex gdb.selected_frame
26541 @defun gdb.selected_frame ()
26542 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26545 @findex gdb.newest_frame
26546 @defun gdb.newest_frame ()
26547 Return the newest frame object for the selected thread.
26550 @defun gdb.frame_stop_reason_string (reason)
26551 Return a string explaining the reason why @value{GDBN} stopped unwinding
26552 frames, as expressed by the given @var{reason} code (an integer, see the
26553 @code{unwind_stop_reason} method further down in this section).
26556 A @code{gdb.Frame} object has the following methods:
26558 @defun Frame.is_valid ()
26559 Returns true if the @code{gdb.Frame} object is valid, false if not.
26560 A frame object can become invalid if the frame it refers to doesn't
26561 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26562 an exception if it is invalid at the time the method is called.
26565 @defun Frame.name ()
26566 Returns the function name of the frame, or @code{None} if it can't be
26570 @defun Frame.architecture ()
26571 Returns the @code{gdb.Architecture} object corresponding to the frame's
26572 architecture. @xref{Architectures In Python}.
26575 @defun Frame.type ()
26576 Returns the type of the frame. The value can be one of:
26578 @item gdb.NORMAL_FRAME
26579 An ordinary stack frame.
26581 @item gdb.DUMMY_FRAME
26582 A fake stack frame that was created by @value{GDBN} when performing an
26583 inferior function call.
26585 @item gdb.INLINE_FRAME
26586 A frame representing an inlined function. The function was inlined
26587 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26589 @item gdb.TAILCALL_FRAME
26590 A frame representing a tail call. @xref{Tail Call Frames}.
26592 @item gdb.SIGTRAMP_FRAME
26593 A signal trampoline frame. This is the frame created by the OS when
26594 it calls into a signal handler.
26596 @item gdb.ARCH_FRAME
26597 A fake stack frame representing a cross-architecture call.
26599 @item gdb.SENTINEL_FRAME
26600 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26605 @defun Frame.unwind_stop_reason ()
26606 Return an integer representing the reason why it's not possible to find
26607 more frames toward the outermost frame. Use
26608 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26609 function to a string. The value can be one of:
26612 @item gdb.FRAME_UNWIND_NO_REASON
26613 No particular reason (older frames should be available).
26615 @item gdb.FRAME_UNWIND_NULL_ID
26616 The previous frame's analyzer returns an invalid result. This is no
26617 longer used by @value{GDBN}, and is kept only for backward
26620 @item gdb.FRAME_UNWIND_OUTERMOST
26621 This frame is the outermost.
26623 @item gdb.FRAME_UNWIND_UNAVAILABLE
26624 Cannot unwind further, because that would require knowing the
26625 values of registers or memory that have not been collected.
26627 @item gdb.FRAME_UNWIND_INNER_ID
26628 This frame ID looks like it ought to belong to a NEXT frame,
26629 but we got it for a PREV frame. Normally, this is a sign of
26630 unwinder failure. It could also indicate stack corruption.
26632 @item gdb.FRAME_UNWIND_SAME_ID
26633 This frame has the same ID as the previous one. That means
26634 that unwinding further would almost certainly give us another
26635 frame with exactly the same ID, so break the chain. Normally,
26636 this is a sign of unwinder failure. It could also indicate
26639 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26640 The frame unwinder did not find any saved PC, but we needed
26641 one to unwind further.
26643 @item gdb.FRAME_UNWIND_FIRST_ERROR
26644 Any stop reason greater or equal to this value indicates some kind
26645 of error. This special value facilitates writing code that tests
26646 for errors in unwinding in a way that will work correctly even if
26647 the list of the other values is modified in future @value{GDBN}
26648 versions. Using it, you could write:
26650 reason = gdb.selected_frame().unwind_stop_reason ()
26651 reason_str = gdb.frame_stop_reason_string (reason)
26652 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26653 print "An error occured: %s" % reason_str
26660 Returns the frame's resume address.
26663 @defun Frame.block ()
26664 Return the frame's code block. @xref{Blocks In Python}.
26667 @defun Frame.function ()
26668 Return the symbol for the function corresponding to this frame.
26669 @xref{Symbols In Python}.
26672 @defun Frame.older ()
26673 Return the frame that called this frame.
26676 @defun Frame.newer ()
26677 Return the frame called by this frame.
26680 @defun Frame.find_sal ()
26681 Return the frame's symtab and line object.
26682 @xref{Symbol Tables In Python}.
26685 @defun Frame.read_var (variable @r{[}, block@r{]})
26686 Return the value of @var{variable} in this frame. If the optional
26687 argument @var{block} is provided, search for the variable from that
26688 block; otherwise start at the frame's current block (which is
26689 determined by the frame's current program counter). @var{variable}
26690 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26691 @code{gdb.Block} object.
26694 @defun Frame.select ()
26695 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26699 @node Blocks In Python
26700 @subsubsection Accessing blocks from Python.
26702 @cindex blocks in python
26705 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26706 roughly to a scope in the source code. Blocks are organized
26707 hierarchically, and are represented individually in Python as a
26708 @code{gdb.Block}. Blocks rely on debugging information being
26711 A frame has a block. Please see @ref{Frames In Python}, for a more
26712 in-depth discussion of frames.
26714 The outermost block is known as the @dfn{global block}. The global
26715 block typically holds public global variables and functions.
26717 The block nested just inside the global block is the @dfn{static
26718 block}. The static block typically holds file-scoped variables and
26721 @value{GDBN} provides a method to get a block's superblock, but there
26722 is currently no way to examine the sub-blocks of a block, or to
26723 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26726 Here is a short example that should help explain blocks:
26729 /* This is in the global block. */
26732 /* This is in the static block. */
26733 static int file_scope;
26735 /* 'function' is in the global block, and 'argument' is
26736 in a block nested inside of 'function'. */
26737 int function (int argument)
26739 /* 'local' is in a block inside 'function'. It may or may
26740 not be in the same block as 'argument'. */
26744 /* 'inner' is in a block whose superblock is the one holding
26748 /* If this call is expanded by the compiler, you may see
26749 a nested block here whose function is 'inline_function'
26750 and whose superblock is the one holding 'inner'. */
26751 inline_function ();
26756 A @code{gdb.Block} is iterable. The iterator returns the symbols
26757 (@pxref{Symbols In Python}) local to the block. Python programs
26758 should not assume that a specific block object will always contain a
26759 given symbol, since changes in @value{GDBN} features and
26760 infrastructure may cause symbols move across blocks in a symbol
26763 The following block-related functions are available in the @code{gdb}
26766 @findex gdb.block_for_pc
26767 @defun gdb.block_for_pc (pc)
26768 Return the innermost @code{gdb.Block} containing the given @var{pc}
26769 value. If the block cannot be found for the @var{pc} value specified,
26770 the function will return @code{None}.
26773 A @code{gdb.Block} object has the following methods:
26775 @defun Block.is_valid ()
26776 Returns @code{True} if the @code{gdb.Block} object is valid,
26777 @code{False} if not. A block object can become invalid if the block it
26778 refers to doesn't exist anymore in the inferior. All other
26779 @code{gdb.Block} methods will throw an exception if it is invalid at
26780 the time the method is called. The block's validity is also checked
26781 during iteration over symbols of the block.
26784 A @code{gdb.Block} object has the following attributes:
26786 @defvar Block.start
26787 The start address of the block. This attribute is not writable.
26791 The end address of the block. This attribute is not writable.
26794 @defvar Block.function
26795 The name of the block represented as a @code{gdb.Symbol}. If the
26796 block is not named, then this attribute holds @code{None}. This
26797 attribute is not writable.
26799 For ordinary function blocks, the superblock is the static block.
26800 However, you should note that it is possible for a function block to
26801 have a superblock that is not the static block -- for instance this
26802 happens for an inlined function.
26805 @defvar Block.superblock
26806 The block containing this block. If this parent block does not exist,
26807 this attribute holds @code{None}. This attribute is not writable.
26810 @defvar Block.global_block
26811 The global block associated with this block. This attribute is not
26815 @defvar Block.static_block
26816 The static block associated with this block. This attribute is not
26820 @defvar Block.is_global
26821 @code{True} if the @code{gdb.Block} object is a global block,
26822 @code{False} if not. This attribute is not
26826 @defvar Block.is_static
26827 @code{True} if the @code{gdb.Block} object is a static block,
26828 @code{False} if not. This attribute is not writable.
26831 @node Symbols In Python
26832 @subsubsection Python representation of Symbols.
26834 @cindex symbols in python
26837 @value{GDBN} represents every variable, function and type as an
26838 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26839 Similarly, Python represents these symbols in @value{GDBN} with the
26840 @code{gdb.Symbol} object.
26842 The following symbol-related functions are available in the @code{gdb}
26845 @findex gdb.lookup_symbol
26846 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26847 This function searches for a symbol by name. The search scope can be
26848 restricted to the parameters defined in the optional domain and block
26851 @var{name} is the name of the symbol. It must be a string. The
26852 optional @var{block} argument restricts the search to symbols visible
26853 in that @var{block}. The @var{block} argument must be a
26854 @code{gdb.Block} object. If omitted, the block for the current frame
26855 is used. The optional @var{domain} argument restricts
26856 the search to the domain type. The @var{domain} argument must be a
26857 domain constant defined in the @code{gdb} module and described later
26860 The result is a tuple of two elements.
26861 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26863 If the symbol is found, the second element is @code{True} if the symbol
26864 is a field of a method's object (e.g., @code{this} in C@t{++}),
26865 otherwise it is @code{False}.
26866 If the symbol is not found, the second element is @code{False}.
26869 @findex gdb.lookup_global_symbol
26870 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26871 This function searches for a global symbol by name.
26872 The search scope can be restricted to by the domain argument.
26874 @var{name} is the name of the symbol. It must be a string.
26875 The optional @var{domain} argument restricts the search to the domain type.
26876 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26877 module and described later in this chapter.
26879 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26883 A @code{gdb.Symbol} object has the following attributes:
26885 @defvar Symbol.type
26886 The type of the symbol or @code{None} if no type is recorded.
26887 This attribute is represented as a @code{gdb.Type} object.
26888 @xref{Types In Python}. This attribute is not writable.
26891 @defvar Symbol.symtab
26892 The symbol table in which the symbol appears. This attribute is
26893 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26894 Python}. This attribute is not writable.
26897 @defvar Symbol.line
26898 The line number in the source code at which the symbol was defined.
26899 This is an integer.
26902 @defvar Symbol.name
26903 The name of the symbol as a string. This attribute is not writable.
26906 @defvar Symbol.linkage_name
26907 The name of the symbol, as used by the linker (i.e., may be mangled).
26908 This attribute is not writable.
26911 @defvar Symbol.print_name
26912 The name of the symbol in a form suitable for output. This is either
26913 @code{name} or @code{linkage_name}, depending on whether the user
26914 asked @value{GDBN} to display demangled or mangled names.
26917 @defvar Symbol.addr_class
26918 The address class of the symbol. This classifies how to find the value
26919 of a symbol. Each address class is a constant defined in the
26920 @code{gdb} module and described later in this chapter.
26923 @defvar Symbol.needs_frame
26924 This is @code{True} if evaluating this symbol's value requires a frame
26925 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26926 local variables will require a frame, but other symbols will not.
26929 @defvar Symbol.is_argument
26930 @code{True} if the symbol is an argument of a function.
26933 @defvar Symbol.is_constant
26934 @code{True} if the symbol is a constant.
26937 @defvar Symbol.is_function
26938 @code{True} if the symbol is a function or a method.
26941 @defvar Symbol.is_variable
26942 @code{True} if the symbol is a variable.
26945 A @code{gdb.Symbol} object has the following methods:
26947 @defun Symbol.is_valid ()
26948 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26949 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26950 the symbol it refers to does not exist in @value{GDBN} any longer.
26951 All other @code{gdb.Symbol} methods will throw an exception if it is
26952 invalid at the time the method is called.
26955 @defun Symbol.value (@r{[}frame@r{]})
26956 Compute the value of the symbol, as a @code{gdb.Value}. For
26957 functions, this computes the address of the function, cast to the
26958 appropriate type. If the symbol requires a frame in order to compute
26959 its value, then @var{frame} must be given. If @var{frame} is not
26960 given, or if @var{frame} is invalid, then this method will throw an
26964 The available domain categories in @code{gdb.Symbol} are represented
26965 as constants in the @code{gdb} module:
26968 @findex SYMBOL_UNDEF_DOMAIN
26969 @findex gdb.SYMBOL_UNDEF_DOMAIN
26970 @item gdb.SYMBOL_UNDEF_DOMAIN
26971 This is used when a domain has not been discovered or none of the
26972 following domains apply. This usually indicates an error either
26973 in the symbol information or in @value{GDBN}'s handling of symbols.
26974 @findex SYMBOL_VAR_DOMAIN
26975 @findex gdb.SYMBOL_VAR_DOMAIN
26976 @item gdb.SYMBOL_VAR_DOMAIN
26977 This domain contains variables, function names, typedef names and enum
26979 @findex SYMBOL_STRUCT_DOMAIN
26980 @findex gdb.SYMBOL_STRUCT_DOMAIN
26981 @item gdb.SYMBOL_STRUCT_DOMAIN
26982 This domain holds struct, union and enum type names.
26983 @findex SYMBOL_LABEL_DOMAIN
26984 @findex gdb.SYMBOL_LABEL_DOMAIN
26985 @item gdb.SYMBOL_LABEL_DOMAIN
26986 This domain contains names of labels (for gotos).
26987 @findex SYMBOL_VARIABLES_DOMAIN
26988 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26989 @item gdb.SYMBOL_VARIABLES_DOMAIN
26990 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26991 contains everything minus functions and types.
26992 @findex SYMBOL_FUNCTIONS_DOMAIN
26993 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26994 @item gdb.SYMBOL_FUNCTION_DOMAIN
26995 This domain contains all functions.
26996 @findex SYMBOL_TYPES_DOMAIN
26997 @findex gdb.SYMBOL_TYPES_DOMAIN
26998 @item gdb.SYMBOL_TYPES_DOMAIN
26999 This domain contains all types.
27002 The available address class categories in @code{gdb.Symbol} are represented
27003 as constants in the @code{gdb} module:
27006 @findex SYMBOL_LOC_UNDEF
27007 @findex gdb.SYMBOL_LOC_UNDEF
27008 @item gdb.SYMBOL_LOC_UNDEF
27009 If this is returned by address class, it indicates an error either in
27010 the symbol information or in @value{GDBN}'s handling of symbols.
27011 @findex SYMBOL_LOC_CONST
27012 @findex gdb.SYMBOL_LOC_CONST
27013 @item gdb.SYMBOL_LOC_CONST
27014 Value is constant int.
27015 @findex SYMBOL_LOC_STATIC
27016 @findex gdb.SYMBOL_LOC_STATIC
27017 @item gdb.SYMBOL_LOC_STATIC
27018 Value is at a fixed address.
27019 @findex SYMBOL_LOC_REGISTER
27020 @findex gdb.SYMBOL_LOC_REGISTER
27021 @item gdb.SYMBOL_LOC_REGISTER
27022 Value is in a register.
27023 @findex SYMBOL_LOC_ARG
27024 @findex gdb.SYMBOL_LOC_ARG
27025 @item gdb.SYMBOL_LOC_ARG
27026 Value is an argument. This value is at the offset stored within the
27027 symbol inside the frame's argument list.
27028 @findex SYMBOL_LOC_REF_ARG
27029 @findex gdb.SYMBOL_LOC_REF_ARG
27030 @item gdb.SYMBOL_LOC_REF_ARG
27031 Value address is stored in the frame's argument list. Just like
27032 @code{LOC_ARG} except that the value's address is stored at the
27033 offset, not the value itself.
27034 @findex SYMBOL_LOC_REGPARM_ADDR
27035 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
27036 @item gdb.SYMBOL_LOC_REGPARM_ADDR
27037 Value is a specified register. Just like @code{LOC_REGISTER} except
27038 the register holds the address of the argument instead of the argument
27040 @findex SYMBOL_LOC_LOCAL
27041 @findex gdb.SYMBOL_LOC_LOCAL
27042 @item gdb.SYMBOL_LOC_LOCAL
27043 Value is a local variable.
27044 @findex SYMBOL_LOC_TYPEDEF
27045 @findex gdb.SYMBOL_LOC_TYPEDEF
27046 @item gdb.SYMBOL_LOC_TYPEDEF
27047 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
27049 @findex SYMBOL_LOC_BLOCK
27050 @findex gdb.SYMBOL_LOC_BLOCK
27051 @item gdb.SYMBOL_LOC_BLOCK
27053 @findex SYMBOL_LOC_CONST_BYTES
27054 @findex gdb.SYMBOL_LOC_CONST_BYTES
27055 @item gdb.SYMBOL_LOC_CONST_BYTES
27056 Value is a byte-sequence.
27057 @findex SYMBOL_LOC_UNRESOLVED
27058 @findex gdb.SYMBOL_LOC_UNRESOLVED
27059 @item gdb.SYMBOL_LOC_UNRESOLVED
27060 Value is at a fixed address, but the address of the variable has to be
27061 determined from the minimal symbol table whenever the variable is
27063 @findex SYMBOL_LOC_OPTIMIZED_OUT
27064 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
27065 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
27066 The value does not actually exist in the program.
27067 @findex SYMBOL_LOC_COMPUTED
27068 @findex gdb.SYMBOL_LOC_COMPUTED
27069 @item gdb.SYMBOL_LOC_COMPUTED
27070 The value's address is a computed location.
27073 @node Symbol Tables In Python
27074 @subsubsection Symbol table representation in Python.
27076 @cindex symbol tables in python
27078 @tindex gdb.Symtab_and_line
27080 Access to symbol table data maintained by @value{GDBN} on the inferior
27081 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
27082 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
27083 from the @code{find_sal} method in @code{gdb.Frame} object.
27084 @xref{Frames In Python}.
27086 For more information on @value{GDBN}'s symbol table management, see
27087 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27089 A @code{gdb.Symtab_and_line} object has the following attributes:
27091 @defvar Symtab_and_line.symtab
27092 The symbol table object (@code{gdb.Symtab}) for this frame.
27093 This attribute is not writable.
27096 @defvar Symtab_and_line.pc
27097 Indicates the start of the address range occupied by code for the
27098 current source line. This attribute is not writable.
27101 @defvar Symtab_and_line.last
27102 Indicates the end of the address range occupied by code for the current
27103 source line. This attribute is not writable.
27106 @defvar Symtab_and_line.line
27107 Indicates the current line number for this object. This
27108 attribute is not writable.
27111 A @code{gdb.Symtab_and_line} object has the following methods:
27113 @defun Symtab_and_line.is_valid ()
27114 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27115 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27116 invalid if the Symbol table and line object it refers to does not
27117 exist in @value{GDBN} any longer. All other
27118 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27119 invalid at the time the method is called.
27122 A @code{gdb.Symtab} object has the following attributes:
27124 @defvar Symtab.filename
27125 The symbol table's source filename. This attribute is not writable.
27128 @defvar Symtab.objfile
27129 The symbol table's backing object file. @xref{Objfiles In Python}.
27130 This attribute is not writable.
27133 A @code{gdb.Symtab} object has the following methods:
27135 @defun Symtab.is_valid ()
27136 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27137 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27138 the symbol table it refers to does not exist in @value{GDBN} any
27139 longer. All other @code{gdb.Symtab} methods will throw an exception
27140 if it is invalid at the time the method is called.
27143 @defun Symtab.fullname ()
27144 Return the symbol table's source absolute file name.
27147 @defun Symtab.global_block ()
27148 Return the global block of the underlying symbol table.
27149 @xref{Blocks In Python}.
27152 @defun Symtab.static_block ()
27153 Return the static block of the underlying symbol table.
27154 @xref{Blocks In Python}.
27157 @defun Symtab.linetable ()
27158 Return the line table associated with the symbol table.
27159 @xref{Line Tables In Python}.
27162 @node Line Tables In Python
27163 @subsubsection Manipulating line tables using Python
27165 @cindex line tables in python
27166 @tindex gdb.LineTable
27168 Python code can request and inspect line table information from a
27169 symbol table that is loaded in @value{GDBN}. A line table is a
27170 mapping of source lines to their executable locations in memory. To
27171 acquire the line table information for a particular symbol table, use
27172 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27174 A @code{gdb.LineTable} is iterable. The iterator returns
27175 @code{LineTableEntry} objects that correspond to the source line and
27176 address for each line table entry. @code{LineTableEntry} objects have
27177 the following attributes:
27179 @defvar LineTableEntry.line
27180 The source line number for this line table entry. This number
27181 corresponds to the actual line of source. This attribute is not
27185 @defvar LineTableEntry.pc
27186 The address that is associated with the line table entry where the
27187 executable code for that source line resides in memory. This
27188 attribute is not writable.
27191 As there can be multiple addresses for a single source line, you may
27192 receive multiple @code{LineTableEntry} objects with matching
27193 @code{line} attributes, but with different @code{pc} attributes. The
27194 iterator is sorted in ascending @code{pc} order. Here is a small
27195 example illustrating iterating over a line table.
27198 symtab = gdb.selected_frame().find_sal().symtab
27199 linetable = symtab.linetable()
27200 for line in linetable:
27201 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27204 This will have the following output:
27207 Line: 33 Address: 0x4005c8L
27208 Line: 37 Address: 0x4005caL
27209 Line: 39 Address: 0x4005d2L
27210 Line: 40 Address: 0x4005f8L
27211 Line: 42 Address: 0x4005ffL
27212 Line: 44 Address: 0x400608L
27213 Line: 42 Address: 0x40060cL
27214 Line: 45 Address: 0x400615L
27217 In addition to being able to iterate over a @code{LineTable}, it also
27218 has the following direct access methods:
27220 @defun LineTable.line (line)
27221 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27222 entries in the line table for the given @var{line}. @var{line} refers
27223 to the source code line. If there are no entries for that source code
27224 @var{line}, the Python @code{None} is returned.
27227 @defun LineTable.has_line (line)
27228 Return a Python @code{Boolean} indicating whether there is an entry in
27229 the line table for this source line. Return @code{True} if an entry
27230 is found, or @code{False} if not.
27233 @defun LineTable.source_lines ()
27234 Return a Python @code{List} of the source line numbers in the symbol
27235 table. Only lines with executable code locations are returned. The
27236 contents of the @code{List} will just be the source line entries
27237 represented as Python @code{Long} values.
27240 @node Breakpoints In Python
27241 @subsubsection Manipulating breakpoints using Python
27243 @cindex breakpoints in python
27244 @tindex gdb.Breakpoint
27246 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27249 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27250 Create a new breakpoint. @var{spec} is a string naming the location
27251 of the breakpoint, or an expression that defines a watchpoint. The
27252 contents can be any location recognized by the @code{break} command,
27253 or in the case of a watchpoint, by the @code{watch} command. The
27254 optional @var{type} denotes the breakpoint to create from the types
27255 defined later in this chapter. This argument can be either:
27256 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27257 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27258 argument allows the breakpoint to become invisible to the user. The
27259 breakpoint will neither be reported when created, nor will it be
27260 listed in the output from @code{info breakpoints} (but will be listed
27261 with the @code{maint info breakpoints} command). The optional
27262 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27263 Temporary breakpoints are deleted after they have been hit. Any
27264 further access to the Python breakpoint after it has been hit will
27265 result in a runtime error (as that breakpoint has now been
27266 automatically deleted). The optional @var{wp_class} argument defines
27267 the class of watchpoint to create, if @var{type} is
27268 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27269 is assumed to be a @code{gdb.WP_WRITE} class.
27272 @defun Breakpoint.stop (self)
27273 The @code{gdb.Breakpoint} class can be sub-classed and, in
27274 particular, you may choose to implement the @code{stop} method.
27275 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27276 it will be called when the inferior reaches any location of a
27277 breakpoint which instantiates that sub-class. If the method returns
27278 @code{True}, the inferior will be stopped at the location of the
27279 breakpoint, otherwise the inferior will continue.
27281 If there are multiple breakpoints at the same location with a
27282 @code{stop} method, each one will be called regardless of the
27283 return status of the previous. This ensures that all @code{stop}
27284 methods have a chance to execute at that location. In this scenario
27285 if one of the methods returns @code{True} but the others return
27286 @code{False}, the inferior will still be stopped.
27288 You should not alter the execution state of the inferior (i.e.@:, step,
27289 next, etc.), alter the current frame context (i.e.@:, change the current
27290 active frame), or alter, add or delete any breakpoint. As a general
27291 rule, you should not alter any data within @value{GDBN} or the inferior
27294 Example @code{stop} implementation:
27297 class MyBreakpoint (gdb.Breakpoint):
27299 inf_val = gdb.parse_and_eval("foo")
27306 The available watchpoint types represented by constants are defined in the
27311 @findex gdb.WP_READ
27313 Read only watchpoint.
27316 @findex gdb.WP_WRITE
27318 Write only watchpoint.
27321 @findex gdb.WP_ACCESS
27322 @item gdb.WP_ACCESS
27323 Read/Write watchpoint.
27326 @defun Breakpoint.is_valid ()
27327 Return @code{True} if this @code{Breakpoint} object is valid,
27328 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27329 if the user deletes the breakpoint. In this case, the object still
27330 exists, but the underlying breakpoint does not. In the cases of
27331 watchpoint scope, the watchpoint remains valid even if execution of the
27332 inferior leaves the scope of that watchpoint.
27335 @defun Breakpoint.delete
27336 Permanently deletes the @value{GDBN} breakpoint. This also
27337 invalidates the Python @code{Breakpoint} object. Any further access
27338 to this object's attributes or methods will raise an error.
27341 @defvar Breakpoint.enabled
27342 This attribute is @code{True} if the breakpoint is enabled, and
27343 @code{False} otherwise. This attribute is writable.
27346 @defvar Breakpoint.silent
27347 This attribute is @code{True} if the breakpoint is silent, and
27348 @code{False} otherwise. This attribute is writable.
27350 Note that a breakpoint can also be silent if it has commands and the
27351 first command is @code{silent}. This is not reported by the
27352 @code{silent} attribute.
27355 @defvar Breakpoint.thread
27356 If the breakpoint is thread-specific, this attribute holds the thread
27357 id. If the breakpoint is not thread-specific, this attribute is
27358 @code{None}. This attribute is writable.
27361 @defvar Breakpoint.task
27362 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27363 id. If the breakpoint is not task-specific (or the underlying
27364 language is not Ada), this attribute is @code{None}. This attribute
27368 @defvar Breakpoint.ignore_count
27369 This attribute holds the ignore count for the breakpoint, an integer.
27370 This attribute is writable.
27373 @defvar Breakpoint.number
27374 This attribute holds the breakpoint's number --- the identifier used by
27375 the user to manipulate the breakpoint. This attribute is not writable.
27378 @defvar Breakpoint.type
27379 This attribute holds the breakpoint's type --- the identifier used to
27380 determine the actual breakpoint type or use-case. This attribute is not
27384 @defvar Breakpoint.visible
27385 This attribute tells whether the breakpoint is visible to the user
27386 when set, or when the @samp{info breakpoints} command is run. This
27387 attribute is not writable.
27390 @defvar Breakpoint.temporary
27391 This attribute indicates whether the breakpoint was created as a
27392 temporary breakpoint. Temporary breakpoints are automatically deleted
27393 after that breakpoint has been hit. Access to this attribute, and all
27394 other attributes and functions other than the @code{is_valid}
27395 function, will result in an error after the breakpoint has been hit
27396 (as it has been automatically deleted). This attribute is not
27400 The available types are represented by constants defined in the @code{gdb}
27404 @findex BP_BREAKPOINT
27405 @findex gdb.BP_BREAKPOINT
27406 @item gdb.BP_BREAKPOINT
27407 Normal code breakpoint.
27409 @findex BP_WATCHPOINT
27410 @findex gdb.BP_WATCHPOINT
27411 @item gdb.BP_WATCHPOINT
27412 Watchpoint breakpoint.
27414 @findex BP_HARDWARE_WATCHPOINT
27415 @findex gdb.BP_HARDWARE_WATCHPOINT
27416 @item gdb.BP_HARDWARE_WATCHPOINT
27417 Hardware assisted watchpoint.
27419 @findex BP_READ_WATCHPOINT
27420 @findex gdb.BP_READ_WATCHPOINT
27421 @item gdb.BP_READ_WATCHPOINT
27422 Hardware assisted read watchpoint.
27424 @findex BP_ACCESS_WATCHPOINT
27425 @findex gdb.BP_ACCESS_WATCHPOINT
27426 @item gdb.BP_ACCESS_WATCHPOINT
27427 Hardware assisted access watchpoint.
27430 @defvar Breakpoint.hit_count
27431 This attribute holds the hit count for the breakpoint, an integer.
27432 This attribute is writable, but currently it can only be set to zero.
27435 @defvar Breakpoint.location
27436 This attribute holds the location of the breakpoint, as specified by
27437 the user. It is a string. If the breakpoint does not have a location
27438 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27439 attribute is not writable.
27442 @defvar Breakpoint.expression
27443 This attribute holds a breakpoint expression, as specified by
27444 the user. It is a string. If the breakpoint does not have an
27445 expression (the breakpoint is not a watchpoint) the attribute's value
27446 is @code{None}. This attribute is not writable.
27449 @defvar Breakpoint.condition
27450 This attribute holds the condition of the breakpoint, as specified by
27451 the user. It is a string. If there is no condition, this attribute's
27452 value is @code{None}. This attribute is writable.
27455 @defvar Breakpoint.commands
27456 This attribute holds the commands attached to the breakpoint. If
27457 there are commands, this attribute's value is a string holding all the
27458 commands, separated by newlines. If there are no commands, this
27459 attribute is @code{None}. This attribute is not writable.
27462 @node Finish Breakpoints in Python
27463 @subsubsection Finish Breakpoints
27465 @cindex python finish breakpoints
27466 @tindex gdb.FinishBreakpoint
27468 A finish breakpoint is a temporary breakpoint set at the return address of
27469 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27470 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27471 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27472 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27473 Finish breakpoints are thread specific and must be create with the right
27476 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27477 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27478 object @var{frame}. If @var{frame} is not provided, this defaults to the
27479 newest frame. The optional @var{internal} argument allows the breakpoint to
27480 become invisible to the user. @xref{Breakpoints In Python}, for further
27481 details about this argument.
27484 @defun FinishBreakpoint.out_of_scope (self)
27485 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27486 @code{return} command, @dots{}), a function may not properly terminate, and
27487 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27488 situation, the @code{out_of_scope} callback will be triggered.
27490 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27494 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27496 print "normal finish"
27499 def out_of_scope ():
27500 print "abnormal finish"
27504 @defvar FinishBreakpoint.return_value
27505 When @value{GDBN} is stopped at a finish breakpoint and the frame
27506 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27507 attribute will contain a @code{gdb.Value} object corresponding to the return
27508 value of the function. The value will be @code{None} if the function return
27509 type is @code{void} or if the return value was not computable. This attribute
27513 @node Lazy Strings In Python
27514 @subsubsection Python representation of lazy strings.
27516 @cindex lazy strings in python
27517 @tindex gdb.LazyString
27519 A @dfn{lazy string} is a string whose contents is not retrieved or
27520 encoded until it is needed.
27522 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27523 @code{address} that points to a region of memory, an @code{encoding}
27524 that will be used to encode that region of memory, and a @code{length}
27525 to delimit the region of memory that represents the string. The
27526 difference between a @code{gdb.LazyString} and a string wrapped within
27527 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27528 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27529 retrieved and encoded during printing, while a @code{gdb.Value}
27530 wrapping a string is immediately retrieved and encoded on creation.
27532 A @code{gdb.LazyString} object has the following functions:
27534 @defun LazyString.value ()
27535 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27536 will point to the string in memory, but will lose all the delayed
27537 retrieval, encoding and handling that @value{GDBN} applies to a
27538 @code{gdb.LazyString}.
27541 @defvar LazyString.address
27542 This attribute holds the address of the string. This attribute is not
27546 @defvar LazyString.length
27547 This attribute holds the length of the string in characters. If the
27548 length is -1, then the string will be fetched and encoded up to the
27549 first null of appropriate width. This attribute is not writable.
27552 @defvar LazyString.encoding
27553 This attribute holds the encoding that will be applied to the string
27554 when the string is printed by @value{GDBN}. If the encoding is not
27555 set, or contains an empty string, then @value{GDBN} will select the
27556 most appropriate encoding when the string is printed. This attribute
27560 @defvar LazyString.type
27561 This attribute holds the type that is represented by the lazy string's
27562 type. For a lazy string this will always be a pointer type. To
27563 resolve this to the lazy string's character type, use the type's
27564 @code{target} method. @xref{Types In Python}. This attribute is not
27568 @node Architectures In Python
27569 @subsubsection Python representation of architectures
27570 @cindex Python architectures
27572 @value{GDBN} uses architecture specific parameters and artifacts in a
27573 number of its various computations. An architecture is represented
27574 by an instance of the @code{gdb.Architecture} class.
27576 A @code{gdb.Architecture} class has the following methods:
27578 @defun Architecture.name ()
27579 Return the name (string value) of the architecture.
27582 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27583 Return a list of disassembled instructions starting from the memory
27584 address @var{start_pc}. The optional arguments @var{end_pc} and
27585 @var{count} determine the number of instructions in the returned list.
27586 If both the optional arguments @var{end_pc} and @var{count} are
27587 specified, then a list of at most @var{count} disassembled instructions
27588 whose start address falls in the closed memory address interval from
27589 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27590 specified, but @var{count} is specified, then @var{count} number of
27591 instructions starting from the address @var{start_pc} are returned. If
27592 @var{count} is not specified but @var{end_pc} is specified, then all
27593 instructions whose start address falls in the closed memory address
27594 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27595 @var{end_pc} nor @var{count} are specified, then a single instruction at
27596 @var{start_pc} is returned. For all of these cases, each element of the
27597 returned list is a Python @code{dict} with the following string keys:
27602 The value corresponding to this key is a Python long integer capturing
27603 the memory address of the instruction.
27606 The value corresponding to this key is a string value which represents
27607 the instruction with assembly language mnemonics. The assembly
27608 language flavor used is the same as that specified by the current CLI
27609 variable @code{disassembly-flavor}. @xref{Machine Code}.
27612 The value corresponding to this key is the length (integer value) of the
27613 instruction in bytes.
27618 @node Python Auto-loading
27619 @subsection Python Auto-loading
27620 @cindex Python auto-loading
27622 When a new object file is read (for example, due to the @code{file}
27623 command, or because the inferior has loaded a shared library),
27624 @value{GDBN} will look for Python support scripts in several ways:
27625 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
27626 @xref{Auto-loading extensions}.
27628 The auto-loading feature is useful for supplying application-specific
27629 debugging commands and scripts.
27631 Auto-loading can be enabled or disabled,
27632 and the list of auto-loaded scripts can be printed.
27635 @anchor{set auto-load python-scripts}
27636 @kindex set auto-load python-scripts
27637 @item set auto-load python-scripts [on|off]
27638 Enable or disable the auto-loading of Python scripts.
27640 @anchor{show auto-load python-scripts}
27641 @kindex show auto-load python-scripts
27642 @item show auto-load python-scripts
27643 Show whether auto-loading of Python scripts is enabled or disabled.
27645 @anchor{info auto-load python-scripts}
27646 @kindex info auto-load python-scripts
27647 @cindex print list of auto-loaded Python scripts
27648 @item info auto-load python-scripts [@var{regexp}]
27649 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27651 Also printed is the list of Python scripts that were mentioned in
27652 the @code{.debug_gdb_scripts} section and were not found
27653 (@pxref{dotdebug_gdb_scripts section}).
27654 This is useful because their names are not printed when @value{GDBN}
27655 tries to load them and fails. There may be many of them, and printing
27656 an error message for each one is problematic.
27658 If @var{regexp} is supplied only Python scripts with matching names are printed.
27663 (gdb) info auto-load python-scripts
27665 Yes py-section-script.py
27666 full name: /tmp/py-section-script.py
27667 No my-foo-pretty-printers.py
27671 When reading an auto-loaded file, @value{GDBN} sets the
27672 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27673 function (@pxref{Objfiles In Python}). This can be useful for
27674 registering objfile-specific pretty-printers and frame-filters.
27676 @node Python modules
27677 @subsection Python modules
27678 @cindex python modules
27680 @value{GDBN} comes with several modules to assist writing Python code.
27683 * gdb.printing:: Building and registering pretty-printers.
27684 * gdb.types:: Utilities for working with types.
27685 * gdb.prompt:: Utilities for prompt value substitution.
27689 @subsubsection gdb.printing
27690 @cindex gdb.printing
27692 This module provides a collection of utilities for working with
27696 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27697 This class specifies the API that makes @samp{info pretty-printer},
27698 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27699 Pretty-printers should generally inherit from this class.
27701 @item SubPrettyPrinter (@var{name})
27702 For printers that handle multiple types, this class specifies the
27703 corresponding API for the subprinters.
27705 @item RegexpCollectionPrettyPrinter (@var{name})
27706 Utility class for handling multiple printers, all recognized via
27707 regular expressions.
27708 @xref{Writing a Pretty-Printer}, for an example.
27710 @item FlagEnumerationPrinter (@var{name})
27711 A pretty-printer which handles printing of @code{enum} values. Unlike
27712 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27713 work properly when there is some overlap between the enumeration
27714 constants. @var{name} is the name of the printer and also the name of
27715 the @code{enum} type to look up.
27717 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27718 Register @var{printer} with the pretty-printer list of @var{obj}.
27719 If @var{replace} is @code{True} then any existing copy of the printer
27720 is replaced. Otherwise a @code{RuntimeError} exception is raised
27721 if a printer with the same name already exists.
27725 @subsubsection gdb.types
27728 This module provides a collection of utilities for working with
27729 @code{gdb.Type} objects.
27732 @item get_basic_type (@var{type})
27733 Return @var{type} with const and volatile qualifiers stripped,
27734 and with typedefs and C@t{++} references converted to the underlying type.
27739 typedef const int const_int;
27741 const_int& foo_ref (foo);
27742 int main () @{ return 0; @}
27749 (gdb) python import gdb.types
27750 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27751 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27755 @item has_field (@var{type}, @var{field})
27756 Return @code{True} if @var{type}, assumed to be a type with fields
27757 (e.g., a structure or union), has field @var{field}.
27759 @item make_enum_dict (@var{enum_type})
27760 Return a Python @code{dictionary} type produced from @var{enum_type}.
27762 @item deep_items (@var{type})
27763 Returns a Python iterator similar to the standard
27764 @code{gdb.Type.iteritems} method, except that the iterator returned
27765 by @code{deep_items} will recursively traverse anonymous struct or
27766 union fields. For example:
27780 Then in @value{GDBN}:
27782 (@value{GDBP}) python import gdb.types
27783 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27784 (@value{GDBP}) python print struct_a.keys ()
27786 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27787 @{['a', 'b0', 'b1']@}
27790 @item get_type_recognizers ()
27791 Return a list of the enabled type recognizers for the current context.
27792 This is called by @value{GDBN} during the type-printing process
27793 (@pxref{Type Printing API}).
27795 @item apply_type_recognizers (recognizers, type_obj)
27796 Apply the type recognizers, @var{recognizers}, to the type object
27797 @var{type_obj}. If any recognizer returns a string, return that
27798 string. Otherwise, return @code{None}. This is called by
27799 @value{GDBN} during the type-printing process (@pxref{Type Printing
27802 @item register_type_printer (locus, printer)
27803 This is a convenience function to register a type printer.
27804 @var{printer} is the type printer to register. It must implement the
27805 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27806 which case the printer is registered with that objfile; a
27807 @code{gdb.Progspace}, in which case the printer is registered with
27808 that progspace; or @code{None}, in which case the printer is
27809 registered globally.
27812 This is a base class that implements the type printer protocol. Type
27813 printers are encouraged, but not required, to derive from this class.
27814 It defines a constructor:
27816 @defmethod TypePrinter __init__ (self, name)
27817 Initialize the type printer with the given name. The new printer
27818 starts in the enabled state.
27824 @subsubsection gdb.prompt
27827 This module provides a method for prompt value-substitution.
27830 @item substitute_prompt (@var{string})
27831 Return @var{string} with escape sequences substituted by values. Some
27832 escape sequences take arguments. You can specify arguments inside
27833 ``@{@}'' immediately following the escape sequence.
27835 The escape sequences you can pass to this function are:
27839 Substitute a backslash.
27841 Substitute an ESC character.
27843 Substitute the selected frame; an argument names a frame parameter.
27845 Substitute a newline.
27847 Substitute a parameter's value; the argument names the parameter.
27849 Substitute a carriage return.
27851 Substitute the selected thread; an argument names a thread parameter.
27853 Substitute the version of GDB.
27855 Substitute the current working directory.
27857 Begin a sequence of non-printing characters. These sequences are
27858 typically used with the ESC character, and are not counted in the string
27859 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27860 blue-colored ``(gdb)'' prompt where the length is five.
27862 End a sequence of non-printing characters.
27868 substitute_prompt (``frame: \f,
27869 print arguments: \p@{print frame-arguments@}'')
27872 @exdent will return the string:
27875 "frame: main, print arguments: scalars"
27879 @node Auto-loading extensions
27880 @section Auto-loading extensions
27881 @cindex auto-loading extensions
27883 @value{GDBN} provides two mechanisms for automatically loading extensions
27884 when a new object file is read (for example, due to the @code{file}
27885 command, or because the inferior has loaded a shared library):
27886 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
27887 section of modern file formats like ELF.
27890 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
27891 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
27892 * Which flavor to choose?::
27895 The auto-loading feature is useful for supplying application-specific
27896 debugging commands and features.
27898 Auto-loading can be enabled or disabled,
27899 and the list of auto-loaded scripts can be printed.
27900 See the @samp{auto-loading} section of each extension language
27901 for more information.
27902 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27903 For Python files see @ref{Python Auto-loading}.
27905 Note that loading of this script file also requires accordingly configured
27906 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27908 @node objfile-gdbdotext file
27909 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27910 @cindex @file{@var{objfile}-gdb.gdb}
27911 @cindex @file{@var{objfile}-gdb.py}
27912 @cindex @file{@var{objfile}-gdb.scm}
27914 When a new object file is read, @value{GDBN} looks for a file named
27915 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27916 where @var{objfile} is the object file's name and
27917 where @var{ext} is the file extension for the extension language:
27920 @item @file{@var{objfile}-gdb.gdb}
27921 GDB's own command language
27922 @item @file{@var{objfile}-gdb.py}
27926 @var{script-name} is formed by ensuring that the file name of @var{objfile}
27927 is absolute, following all symlinks, and resolving @code{.} and @code{..}
27928 components, and appending the @file{-gdb.@var{ext}} suffix.
27929 If this file exists and is readable, @value{GDBN} will evaluate it as a
27930 script in the specified extension language.
27932 If this file does not exist, then @value{GDBN} will look for
27933 @var{script-name} file in all of the directories as specified below.
27935 Note that loading of these files requires an accordingly configured
27936 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27938 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27939 scripts normally according to its @file{.exe} filename. But if no scripts are
27940 found @value{GDBN} also tries script filenames matching the object file without
27941 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27942 is attempted on any platform. This makes the script filenames compatible
27943 between Unix and MS-Windows hosts.
27946 @anchor{set auto-load scripts-directory}
27947 @kindex set auto-load scripts-directory
27948 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27949 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27950 may be delimited by the host platform path separator in use
27951 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27953 Each entry here needs to be covered also by the security setting
27954 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27956 @anchor{with-auto-load-dir}
27957 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27958 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27959 configuration option @option{--with-auto-load-dir}.
27961 Any reference to @file{$debugdir} will get replaced by
27962 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27963 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27964 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27965 @file{$datadir} must be placed as a directory component --- either alone or
27966 delimited by @file{/} or @file{\} directory separators, depending on the host
27969 The list of directories uses path separator (@samp{:} on GNU and Unix
27970 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27971 to the @env{PATH} environment variable.
27973 @anchor{show auto-load scripts-directory}
27974 @kindex show auto-load scripts-directory
27975 @item show auto-load scripts-directory
27976 Show @value{GDBN} auto-loaded scripts location.
27979 @value{GDBN} does not track which files it has already auto-loaded this way.
27980 @value{GDBN} will load the associated script every time the corresponding
27981 @var{objfile} is opened.
27982 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
27983 is evaluated more than once.
27985 @node dotdebug_gdb_scripts section
27986 @subsection The @code{.debug_gdb_scripts} section
27987 @cindex @code{.debug_gdb_scripts} section
27989 For systems using file formats like ELF and COFF,
27990 when @value{GDBN} loads a new object file
27991 it will look for a special section named @code{.debug_gdb_scripts}.
27992 If this section exists, its contents is a list of NUL-terminated names
27993 of scripts to load. Each entry begins with a non-NULL prefix byte that
27994 specifies the kind of entry, typically the extension language.
27996 @value{GDBN} will look for each specified script file first in the
27997 current directory and then along the source search path
27998 (@pxref{Source Path, ,Specifying Source Directories}),
27999 except that @file{$cdir} is not searched, since the compilation
28000 directory is not relevant to scripts.
28002 Entries can be placed in section @code{.debug_gdb_scripts} with,
28003 for example, this GCC macro for Python scripts.
28006 /* Note: The "MS" section flags are to remove duplicates. */
28007 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28009 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28010 .byte 1 /* Python */\n\
28011 .asciz \"" script_name "\"\n\
28017 Then one can reference the macro in a header or source file like this:
28020 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28023 The script name may include directories if desired.
28025 Note that loading of this script file also requires accordingly configured
28026 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28028 If the macro invocation is put in a header, any application or library
28029 using this header will get a reference to the specified script,
28030 and with the use of @code{"MS"} attributes on the section, the linker
28031 will remove duplicates.
28033 @node Which flavor to choose?
28034 @subsection Which flavor to choose?
28036 Given the multiple ways of auto-loading extensions, it might not always
28037 be clear which one to choose. This section provides some guidance.
28040 Benefits of the @file{-gdb.@var{ext}} way:
28044 Can be used with file formats that don't support multiple sections.
28047 Ease of finding scripts for public libraries.
28049 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28050 in the source search path.
28051 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28052 isn't a source directory in which to find the script.
28055 Doesn't require source code additions.
28059 Benefits of the @code{.debug_gdb_scripts} way:
28063 Works with static linking.
28065 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28066 trigger their loading. When an application is statically linked the only
28067 objfile available is the executable, and it is cumbersome to attach all the
28068 scripts from all the input libraries to the executable's
28069 @file{-gdb.@var{ext}} script.
28072 Works with classes that are entirely inlined.
28074 Some classes can be entirely inlined, and thus there may not be an associated
28075 shared library to attach a @file{-gdb.@var{ext}} script to.
28078 Scripts needn't be copied out of the source tree.
28080 In some circumstances, apps can be built out of large collections of internal
28081 libraries, and the build infrastructure necessary to install the
28082 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28083 cumbersome. It may be easier to specify the scripts in the
28084 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28085 top of the source tree to the source search path.
28089 @section Creating new spellings of existing commands
28090 @cindex aliases for commands
28092 It is often useful to define alternate spellings of existing commands.
28093 For example, if a new @value{GDBN} command defined in Python has
28094 a long name to type, it is handy to have an abbreviated version of it
28095 that involves less typing.
28097 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28098 of the @samp{step} command even though it is otherwise an ambiguous
28099 abbreviation of other commands like @samp{set} and @samp{show}.
28101 Aliases are also used to provide shortened or more common versions
28102 of multi-word commands. For example, @value{GDBN} provides the
28103 @samp{tty} alias of the @samp{set inferior-tty} command.
28105 You can define a new alias with the @samp{alias} command.
28110 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
28114 @var{ALIAS} specifies the name of the new alias.
28115 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
28118 @var{COMMAND} specifies the name of an existing command
28119 that is being aliased.
28121 The @samp{-a} option specifies that the new alias is an abbreviation
28122 of the command. Abbreviations are not shown in command
28123 lists displayed by the @samp{help} command.
28125 The @samp{--} option specifies the end of options,
28126 and is useful when @var{ALIAS} begins with a dash.
28128 Here is a simple example showing how to make an abbreviation
28129 of a command so that there is less to type.
28130 Suppose you were tired of typing @samp{disas}, the current
28131 shortest unambiguous abbreviation of the @samp{disassemble} command
28132 and you wanted an even shorter version named @samp{di}.
28133 The following will accomplish this.
28136 (gdb) alias -a di = disas
28139 Note that aliases are different from user-defined commands.
28140 With a user-defined command, you also need to write documentation
28141 for it with the @samp{document} command.
28142 An alias automatically picks up the documentation of the existing command.
28144 Here is an example where we make @samp{elms} an abbreviation of
28145 @samp{elements} in the @samp{set print elements} command.
28146 This is to show that you can make an abbreviation of any part
28150 (gdb) alias -a set print elms = set print elements
28151 (gdb) alias -a show print elms = show print elements
28152 (gdb) set p elms 20
28154 Limit on string chars or array elements to print is 200.
28157 Note that if you are defining an alias of a @samp{set} command,
28158 and you want to have an alias for the corresponding @samp{show}
28159 command, then you need to define the latter separately.
28161 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28162 @var{ALIAS}, just as they are normally.
28165 (gdb) alias -a set pr elms = set p ele
28168 Finally, here is an example showing the creation of a one word
28169 alias for a more complex command.
28170 This creates alias @samp{spe} of the command @samp{set print elements}.
28173 (gdb) alias spe = set print elements
28178 @chapter Command Interpreters
28179 @cindex command interpreters
28181 @value{GDBN} supports multiple command interpreters, and some command
28182 infrastructure to allow users or user interface writers to switch
28183 between interpreters or run commands in other interpreters.
28185 @value{GDBN} currently supports two command interpreters, the console
28186 interpreter (sometimes called the command-line interpreter or @sc{cli})
28187 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28188 describes both of these interfaces in great detail.
28190 By default, @value{GDBN} will start with the console interpreter.
28191 However, the user may choose to start @value{GDBN} with another
28192 interpreter by specifying the @option{-i} or @option{--interpreter}
28193 startup options. Defined interpreters include:
28197 @cindex console interpreter
28198 The traditional console or command-line interpreter. This is the most often
28199 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28200 @value{GDBN} will use this interpreter.
28203 @cindex mi interpreter
28204 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28205 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28206 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28210 @cindex mi2 interpreter
28211 The current @sc{gdb/mi} interface.
28214 @cindex mi1 interpreter
28215 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28219 @cindex invoke another interpreter
28220 The interpreter being used by @value{GDBN} may not be dynamically
28221 switched at runtime. Although possible, this could lead to a very
28222 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28223 enters the command "interpreter-set console" in a console view,
28224 @value{GDBN} would switch to using the console interpreter, rendering
28225 the IDE inoperable!
28227 @kindex interpreter-exec
28228 Although you may only choose a single interpreter at startup, you may execute
28229 commands in any interpreter from the current interpreter using the appropriate
28230 command. If you are running the console interpreter, simply use the
28231 @code{interpreter-exec} command:
28234 interpreter-exec mi "-data-list-register-names"
28237 @sc{gdb/mi} has a similar command, although it is only available in versions of
28238 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28241 @chapter @value{GDBN} Text User Interface
28243 @cindex Text User Interface
28246 * TUI Overview:: TUI overview
28247 * TUI Keys:: TUI key bindings
28248 * TUI Single Key Mode:: TUI single key mode
28249 * TUI Commands:: TUI-specific commands
28250 * TUI Configuration:: TUI configuration variables
28253 The @value{GDBN} Text User Interface (TUI) is a terminal
28254 interface which uses the @code{curses} library to show the source
28255 file, the assembly output, the program registers and @value{GDBN}
28256 commands in separate text windows. The TUI mode is supported only
28257 on platforms where a suitable version of the @code{curses} library
28260 The TUI mode is enabled by default when you invoke @value{GDBN} as
28261 @samp{@value{GDBP} -tui}.
28262 You can also switch in and out of TUI mode while @value{GDBN} runs by
28263 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28264 @xref{TUI Keys, ,TUI Key Bindings}.
28267 @section TUI Overview
28269 In TUI mode, @value{GDBN} can display several text windows:
28273 This window is the @value{GDBN} command window with the @value{GDBN}
28274 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28275 managed using readline.
28278 The source window shows the source file of the program. The current
28279 line and active breakpoints are displayed in this window.
28282 The assembly window shows the disassembly output of the program.
28285 This window shows the processor registers. Registers are highlighted
28286 when their values change.
28289 The source and assembly windows show the current program position
28290 by highlighting the current line and marking it with a @samp{>} marker.
28291 Breakpoints are indicated with two markers. The first marker
28292 indicates the breakpoint type:
28296 Breakpoint which was hit at least once.
28299 Breakpoint which was never hit.
28302 Hardware breakpoint which was hit at least once.
28305 Hardware breakpoint which was never hit.
28308 The second marker indicates whether the breakpoint is enabled or not:
28312 Breakpoint is enabled.
28315 Breakpoint is disabled.
28318 The source, assembly and register windows are updated when the current
28319 thread changes, when the frame changes, or when the program counter
28322 These windows are not all visible at the same time. The command
28323 window is always visible. The others can be arranged in several
28334 source and assembly,
28337 source and registers, or
28340 assembly and registers.
28343 A status line above the command window shows the following information:
28347 Indicates the current @value{GDBN} target.
28348 (@pxref{Targets, ,Specifying a Debugging Target}).
28351 Gives the current process or thread number.
28352 When no process is being debugged, this field is set to @code{No process}.
28355 Gives the current function name for the selected frame.
28356 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28357 When there is no symbol corresponding to the current program counter,
28358 the string @code{??} is displayed.
28361 Indicates the current line number for the selected frame.
28362 When the current line number is not known, the string @code{??} is displayed.
28365 Indicates the current program counter address.
28369 @section TUI Key Bindings
28370 @cindex TUI key bindings
28372 The TUI installs several key bindings in the readline keymaps
28373 @ifset SYSTEM_READLINE
28374 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28376 @ifclear SYSTEM_READLINE
28377 (@pxref{Command Line Editing}).
28379 The following key bindings are installed for both TUI mode and the
28380 @value{GDBN} standard mode.
28389 Enter or leave the TUI mode. When leaving the TUI mode,
28390 the curses window management stops and @value{GDBN} operates using
28391 its standard mode, writing on the terminal directly. When reentering
28392 the TUI mode, control is given back to the curses windows.
28393 The screen is then refreshed.
28397 Use a TUI layout with only one window. The layout will
28398 either be @samp{source} or @samp{assembly}. When the TUI mode
28399 is not active, it will switch to the TUI mode.
28401 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28405 Use a TUI layout with at least two windows. When the current
28406 layout already has two windows, the next layout with two windows is used.
28407 When a new layout is chosen, one window will always be common to the
28408 previous layout and the new one.
28410 Think of it as the Emacs @kbd{C-x 2} binding.
28414 Change the active window. The TUI associates several key bindings
28415 (like scrolling and arrow keys) with the active window. This command
28416 gives the focus to the next TUI window.
28418 Think of it as the Emacs @kbd{C-x o} binding.
28422 Switch in and out of the TUI SingleKey mode that binds single
28423 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28426 The following key bindings only work in the TUI mode:
28431 Scroll the active window one page up.
28435 Scroll the active window one page down.
28439 Scroll the active window one line up.
28443 Scroll the active window one line down.
28447 Scroll the active window one column left.
28451 Scroll the active window one column right.
28455 Refresh the screen.
28458 Because the arrow keys scroll the active window in the TUI mode, they
28459 are not available for their normal use by readline unless the command
28460 window has the focus. When another window is active, you must use
28461 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28462 and @kbd{C-f} to control the command window.
28464 @node TUI Single Key Mode
28465 @section TUI Single Key Mode
28466 @cindex TUI single key mode
28468 The TUI also provides a @dfn{SingleKey} mode, which binds several
28469 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28470 switch into this mode, where the following key bindings are used:
28473 @kindex c @r{(SingleKey TUI key)}
28477 @kindex d @r{(SingleKey TUI key)}
28481 @kindex f @r{(SingleKey TUI key)}
28485 @kindex n @r{(SingleKey TUI key)}
28489 @kindex q @r{(SingleKey TUI key)}
28491 exit the SingleKey mode.
28493 @kindex r @r{(SingleKey TUI key)}
28497 @kindex s @r{(SingleKey TUI key)}
28501 @kindex u @r{(SingleKey TUI key)}
28505 @kindex v @r{(SingleKey TUI key)}
28509 @kindex w @r{(SingleKey TUI key)}
28514 Other keys temporarily switch to the @value{GDBN} command prompt.
28515 The key that was pressed is inserted in the editing buffer so that
28516 it is possible to type most @value{GDBN} commands without interaction
28517 with the TUI SingleKey mode. Once the command is entered the TUI
28518 SingleKey mode is restored. The only way to permanently leave
28519 this mode is by typing @kbd{q} or @kbd{C-x s}.
28523 @section TUI-specific Commands
28524 @cindex TUI commands
28526 The TUI has specific commands to control the text windows.
28527 These commands are always available, even when @value{GDBN} is not in
28528 the TUI mode. When @value{GDBN} is in the standard mode, most
28529 of these commands will automatically switch to the TUI mode.
28531 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28532 terminal, or @value{GDBN} has been started with the machine interface
28533 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28534 these commands will fail with an error, because it would not be
28535 possible or desirable to enable curses window management.
28540 List and give the size of all displayed windows.
28544 Display the next layout.
28547 Display the previous layout.
28550 Display the source window only.
28553 Display the assembly window only.
28556 Display the source and assembly window.
28559 Display the register window together with the source or assembly window.
28563 Make the next window active for scrolling.
28566 Make the previous window active for scrolling.
28569 Make the source window active for scrolling.
28572 Make the assembly window active for scrolling.
28575 Make the register window active for scrolling.
28578 Make the command window active for scrolling.
28582 Refresh the screen. This is similar to typing @kbd{C-L}.
28584 @item tui reg float
28586 Show the floating point registers in the register window.
28588 @item tui reg general
28589 Show the general registers in the register window.
28592 Show the next register group. The list of register groups as well as
28593 their order is target specific. The predefined register groups are the
28594 following: @code{general}, @code{float}, @code{system}, @code{vector},
28595 @code{all}, @code{save}, @code{restore}.
28597 @item tui reg system
28598 Show the system registers in the register window.
28602 Update the source window and the current execution point.
28604 @item winheight @var{name} +@var{count}
28605 @itemx winheight @var{name} -@var{count}
28607 Change the height of the window @var{name} by @var{count}
28608 lines. Positive counts increase the height, while negative counts
28611 @item tabset @var{nchars}
28613 Set the width of tab stops to be @var{nchars} characters.
28616 @node TUI Configuration
28617 @section TUI Configuration Variables
28618 @cindex TUI configuration variables
28620 Several configuration variables control the appearance of TUI windows.
28623 @item set tui border-kind @var{kind}
28624 @kindex set tui border-kind
28625 Select the border appearance for the source, assembly and register windows.
28626 The possible values are the following:
28629 Use a space character to draw the border.
28632 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28635 Use the Alternate Character Set to draw the border. The border is
28636 drawn using character line graphics if the terminal supports them.
28639 @item set tui border-mode @var{mode}
28640 @kindex set tui border-mode
28641 @itemx set tui active-border-mode @var{mode}
28642 @kindex set tui active-border-mode
28643 Select the display attributes for the borders of the inactive windows
28644 or the active window. The @var{mode} can be one of the following:
28647 Use normal attributes to display the border.
28653 Use reverse video mode.
28656 Use half bright mode.
28658 @item half-standout
28659 Use half bright and standout mode.
28662 Use extra bright or bold mode.
28664 @item bold-standout
28665 Use extra bright or bold and standout mode.
28670 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28673 @cindex @sc{gnu} Emacs
28674 A special interface allows you to use @sc{gnu} Emacs to view (and
28675 edit) the source files for the program you are debugging with
28678 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28679 executable file you want to debug as an argument. This command starts
28680 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28681 created Emacs buffer.
28682 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28684 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28689 All ``terminal'' input and output goes through an Emacs buffer, called
28692 This applies both to @value{GDBN} commands and their output, and to the input
28693 and output done by the program you are debugging.
28695 This is useful because it means that you can copy the text of previous
28696 commands and input them again; you can even use parts of the output
28699 All the facilities of Emacs' Shell mode are available for interacting
28700 with your program. In particular, you can send signals the usual
28701 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28705 @value{GDBN} displays source code through Emacs.
28707 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28708 source file for that frame and puts an arrow (@samp{=>}) at the
28709 left margin of the current line. Emacs uses a separate buffer for
28710 source display, and splits the screen to show both your @value{GDBN} session
28713 Explicit @value{GDBN} @code{list} or search commands still produce output as
28714 usual, but you probably have no reason to use them from Emacs.
28717 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28718 a graphical mode, enabled by default, which provides further buffers
28719 that can control the execution and describe the state of your program.
28720 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28722 If you specify an absolute file name when prompted for the @kbd{M-x
28723 gdb} argument, then Emacs sets your current working directory to where
28724 your program resides. If you only specify the file name, then Emacs
28725 sets your current working directory to the directory associated
28726 with the previous buffer. In this case, @value{GDBN} may find your
28727 program by searching your environment's @code{PATH} variable, but on
28728 some operating systems it might not find the source. So, although the
28729 @value{GDBN} input and output session proceeds normally, the auxiliary
28730 buffer does not display the current source and line of execution.
28732 The initial working directory of @value{GDBN} is printed on the top
28733 line of the GUD buffer and this serves as a default for the commands
28734 that specify files for @value{GDBN} to operate on. @xref{Files,
28735 ,Commands to Specify Files}.
28737 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28738 need to call @value{GDBN} by a different name (for example, if you
28739 keep several configurations around, with different names) you can
28740 customize the Emacs variable @code{gud-gdb-command-name} to run the
28743 In the GUD buffer, you can use these special Emacs commands in
28744 addition to the standard Shell mode commands:
28748 Describe the features of Emacs' GUD Mode.
28751 Execute to another source line, like the @value{GDBN} @code{step} command; also
28752 update the display window to show the current file and location.
28755 Execute to next source line in this function, skipping all function
28756 calls, like the @value{GDBN} @code{next} command. Then update the display window
28757 to show the current file and location.
28760 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28761 display window accordingly.
28764 Execute until exit from the selected stack frame, like the @value{GDBN}
28765 @code{finish} command.
28768 Continue execution of your program, like the @value{GDBN} @code{continue}
28772 Go up the number of frames indicated by the numeric argument
28773 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28774 like the @value{GDBN} @code{up} command.
28777 Go down the number of frames indicated by the numeric argument, like the
28778 @value{GDBN} @code{down} command.
28781 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28782 tells @value{GDBN} to set a breakpoint on the source line point is on.
28784 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28785 separate frame which shows a backtrace when the GUD buffer is current.
28786 Move point to any frame in the stack and type @key{RET} to make it
28787 become the current frame and display the associated source in the
28788 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28789 selected frame become the current one. In graphical mode, the
28790 speedbar displays watch expressions.
28792 If you accidentally delete the source-display buffer, an easy way to get
28793 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28794 request a frame display; when you run under Emacs, this recreates
28795 the source buffer if necessary to show you the context of the current
28798 The source files displayed in Emacs are in ordinary Emacs buffers
28799 which are visiting the source files in the usual way. You can edit
28800 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28801 communicates with Emacs in terms of line numbers. If you add or
28802 delete lines from the text, the line numbers that @value{GDBN} knows cease
28803 to correspond properly with the code.
28805 A more detailed description of Emacs' interaction with @value{GDBN} is
28806 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28810 @chapter The @sc{gdb/mi} Interface
28812 @unnumberedsec Function and Purpose
28814 @cindex @sc{gdb/mi}, its purpose
28815 @sc{gdb/mi} is a line based machine oriented text interface to
28816 @value{GDBN} and is activated by specifying using the
28817 @option{--interpreter} command line option (@pxref{Mode Options}). It
28818 is specifically intended to support the development of systems which
28819 use the debugger as just one small component of a larger system.
28821 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28822 in the form of a reference manual.
28824 Note that @sc{gdb/mi} is still under construction, so some of the
28825 features described below are incomplete and subject to change
28826 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28828 @unnumberedsec Notation and Terminology
28830 @cindex notational conventions, for @sc{gdb/mi}
28831 This chapter uses the following notation:
28835 @code{|} separates two alternatives.
28838 @code{[ @var{something} ]} indicates that @var{something} is optional:
28839 it may or may not be given.
28842 @code{( @var{group} )*} means that @var{group} inside the parentheses
28843 may repeat zero or more times.
28846 @code{( @var{group} )+} means that @var{group} inside the parentheses
28847 may repeat one or more times.
28850 @code{"@var{string}"} means a literal @var{string}.
28854 @heading Dependencies
28858 * GDB/MI General Design::
28859 * GDB/MI Command Syntax::
28860 * GDB/MI Compatibility with CLI::
28861 * GDB/MI Development and Front Ends::
28862 * GDB/MI Output Records::
28863 * GDB/MI Simple Examples::
28864 * GDB/MI Command Description Format::
28865 * GDB/MI Breakpoint Commands::
28866 * GDB/MI Catchpoint Commands::
28867 * GDB/MI Program Context::
28868 * GDB/MI Thread Commands::
28869 * GDB/MI Ada Tasking Commands::
28870 * GDB/MI Program Execution::
28871 * GDB/MI Stack Manipulation::
28872 * GDB/MI Variable Objects::
28873 * GDB/MI Data Manipulation::
28874 * GDB/MI Tracepoint Commands::
28875 * GDB/MI Symbol Query::
28876 * GDB/MI File Commands::
28878 * GDB/MI Kod Commands::
28879 * GDB/MI Memory Overlay Commands::
28880 * GDB/MI Signal Handling Commands::
28882 * GDB/MI Target Manipulation::
28883 * GDB/MI File Transfer Commands::
28884 * GDB/MI Ada Exceptions Commands::
28885 * GDB/MI Support Commands::
28886 * GDB/MI Miscellaneous Commands::
28889 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28890 @node GDB/MI General Design
28891 @section @sc{gdb/mi} General Design
28892 @cindex GDB/MI General Design
28894 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28895 parts---commands sent to @value{GDBN}, responses to those commands
28896 and notifications. Each command results in exactly one response,
28897 indicating either successful completion of the command, or an error.
28898 For the commands that do not resume the target, the response contains the
28899 requested information. For the commands that resume the target, the
28900 response only indicates whether the target was successfully resumed.
28901 Notifications is the mechanism for reporting changes in the state of the
28902 target, or in @value{GDBN} state, that cannot conveniently be associated with
28903 a command and reported as part of that command response.
28905 The important examples of notifications are:
28909 Exec notifications. These are used to report changes in
28910 target state---when a target is resumed, or stopped. It would not
28911 be feasible to include this information in response of resuming
28912 commands, because one resume commands can result in multiple events in
28913 different threads. Also, quite some time may pass before any event
28914 happens in the target, while a frontend needs to know whether the resuming
28915 command itself was successfully executed.
28918 Console output, and status notifications. Console output
28919 notifications are used to report output of CLI commands, as well as
28920 diagnostics for other commands. Status notifications are used to
28921 report the progress of a long-running operation. Naturally, including
28922 this information in command response would mean no output is produced
28923 until the command is finished, which is undesirable.
28926 General notifications. Commands may have various side effects on
28927 the @value{GDBN} or target state beyond their official purpose. For example,
28928 a command may change the selected thread. Although such changes can
28929 be included in command response, using notification allows for more
28930 orthogonal frontend design.
28934 There's no guarantee that whenever an MI command reports an error,
28935 @value{GDBN} or the target are in any specific state, and especially,
28936 the state is not reverted to the state before the MI command was
28937 processed. Therefore, whenever an MI command results in an error,
28938 we recommend that the frontend refreshes all the information shown in
28939 the user interface.
28943 * Context management::
28944 * Asynchronous and non-stop modes::
28948 @node Context management
28949 @subsection Context management
28951 @subsubsection Threads and Frames
28953 In most cases when @value{GDBN} accesses the target, this access is
28954 done in context of a specific thread and frame (@pxref{Frames}).
28955 Often, even when accessing global data, the target requires that a thread
28956 be specified. The CLI interface maintains the selected thread and frame,
28957 and supplies them to target on each command. This is convenient,
28958 because a command line user would not want to specify that information
28959 explicitly on each command, and because user interacts with
28960 @value{GDBN} via a single terminal, so no confusion is possible as
28961 to what thread and frame are the current ones.
28963 In the case of MI, the concept of selected thread and frame is less
28964 useful. First, a frontend can easily remember this information
28965 itself. Second, a graphical frontend can have more than one window,
28966 each one used for debugging a different thread, and the frontend might
28967 want to access additional threads for internal purposes. This
28968 increases the risk that by relying on implicitly selected thread, the
28969 frontend may be operating on a wrong one. Therefore, each MI command
28970 should explicitly specify which thread and frame to operate on. To
28971 make it possible, each MI command accepts the @samp{--thread} and
28972 @samp{--frame} options, the value to each is @value{GDBN} identifier
28973 for thread and frame to operate on.
28975 Usually, each top-level window in a frontend allows the user to select
28976 a thread and a frame, and remembers the user selection for further
28977 operations. However, in some cases @value{GDBN} may suggest that the
28978 current thread be changed. For example, when stopping on a breakpoint
28979 it is reasonable to switch to the thread where breakpoint is hit. For
28980 another example, if the user issues the CLI @samp{thread} command via
28981 the frontend, it is desirable to change the frontend's selected thread to the
28982 one specified by user. @value{GDBN} communicates the suggestion to
28983 change current thread using the @samp{=thread-selected} notification.
28984 No such notification is available for the selected frame at the moment.
28986 Note that historically, MI shares the selected thread with CLI, so
28987 frontends used the @code{-thread-select} to execute commands in the
28988 right context. However, getting this to work right is cumbersome. The
28989 simplest way is for frontend to emit @code{-thread-select} command
28990 before every command. This doubles the number of commands that need
28991 to be sent. The alternative approach is to suppress @code{-thread-select}
28992 if the selected thread in @value{GDBN} is supposed to be identical to the
28993 thread the frontend wants to operate on. However, getting this
28994 optimization right can be tricky. In particular, if the frontend
28995 sends several commands to @value{GDBN}, and one of the commands changes the
28996 selected thread, then the behaviour of subsequent commands will
28997 change. So, a frontend should either wait for response from such
28998 problematic commands, or explicitly add @code{-thread-select} for
28999 all subsequent commands. No frontend is known to do this exactly
29000 right, so it is suggested to just always pass the @samp{--thread} and
29001 @samp{--frame} options.
29003 @subsubsection Language
29005 The execution of several commands depends on which language is selected.
29006 By default, the current language (@pxref{show language}) is used.
29007 But for commands known to be language-sensitive, it is recommended
29008 to use the @samp{--language} option. This option takes one argument,
29009 which is the name of the language to use while executing the command.
29013 -data-evaluate-expression --language c "sizeof (void*)"
29018 The valid language names are the same names accepted by the
29019 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29020 @samp{local} or @samp{unknown}.
29022 @node Asynchronous and non-stop modes
29023 @subsection Asynchronous command execution and non-stop mode
29025 On some targets, @value{GDBN} is capable of processing MI commands
29026 even while the target is running. This is called @dfn{asynchronous
29027 command execution} (@pxref{Background Execution}). The frontend may
29028 specify a preferrence for asynchronous execution using the
29029 @code{-gdb-set target-async 1} command, which should be emitted before
29030 either running the executable or attaching to the target. After the
29031 frontend has started the executable or attached to the target, it can
29032 find if asynchronous execution is enabled using the
29033 @code{-list-target-features} command.
29035 Even if @value{GDBN} can accept a command while target is running,
29036 many commands that access the target do not work when the target is
29037 running. Therefore, asynchronous command execution is most useful
29038 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29039 it is possible to examine the state of one thread, while other threads
29042 When a given thread is running, MI commands that try to access the
29043 target in the context of that thread may not work, or may work only on
29044 some targets. In particular, commands that try to operate on thread's
29045 stack will not work, on any target. Commands that read memory, or
29046 modify breakpoints, may work or not work, depending on the target. Note
29047 that even commands that operate on global state, such as @code{print},
29048 @code{set}, and breakpoint commands, still access the target in the
29049 context of a specific thread, so frontend should try to find a
29050 stopped thread and perform the operation on that thread (using the
29051 @samp{--thread} option).
29053 Which commands will work in the context of a running thread is
29054 highly target dependent. However, the two commands
29055 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29056 to find the state of a thread, will always work.
29058 @node Thread groups
29059 @subsection Thread groups
29060 @value{GDBN} may be used to debug several processes at the same time.
29061 On some platfroms, @value{GDBN} may support debugging of several
29062 hardware systems, each one having several cores with several different
29063 processes running on each core. This section describes the MI
29064 mechanism to support such debugging scenarios.
29066 The key observation is that regardless of the structure of the
29067 target, MI can have a global list of threads, because most commands that
29068 accept the @samp{--thread} option do not need to know what process that
29069 thread belongs to. Therefore, it is not necessary to introduce
29070 neither additional @samp{--process} option, nor an notion of the
29071 current process in the MI interface. The only strictly new feature
29072 that is required is the ability to find how the threads are grouped
29075 To allow the user to discover such grouping, and to support arbitrary
29076 hierarchy of machines/cores/processes, MI introduces the concept of a
29077 @dfn{thread group}. Thread group is a collection of threads and other
29078 thread groups. A thread group always has a string identifier, a type,
29079 and may have additional attributes specific to the type. A new
29080 command, @code{-list-thread-groups}, returns the list of top-level
29081 thread groups, which correspond to processes that @value{GDBN} is
29082 debugging at the moment. By passing an identifier of a thread group
29083 to the @code{-list-thread-groups} command, it is possible to obtain
29084 the members of specific thread group.
29086 To allow the user to easily discover processes, and other objects, he
29087 wishes to debug, a concept of @dfn{available thread group} is
29088 introduced. Available thread group is an thread group that
29089 @value{GDBN} is not debugging, but that can be attached to, using the
29090 @code{-target-attach} command. The list of available top-level thread
29091 groups can be obtained using @samp{-list-thread-groups --available}.
29092 In general, the content of a thread group may be only retrieved only
29093 after attaching to that thread group.
29095 Thread groups are related to inferiors (@pxref{Inferiors and
29096 Programs}). Each inferior corresponds to a thread group of a special
29097 type @samp{process}, and some additional operations are permitted on
29098 such thread groups.
29100 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29101 @node GDB/MI Command Syntax
29102 @section @sc{gdb/mi} Command Syntax
29105 * GDB/MI Input Syntax::
29106 * GDB/MI Output Syntax::
29109 @node GDB/MI Input Syntax
29110 @subsection @sc{gdb/mi} Input Syntax
29112 @cindex input syntax for @sc{gdb/mi}
29113 @cindex @sc{gdb/mi}, input syntax
29115 @item @var{command} @expansion{}
29116 @code{@var{cli-command} | @var{mi-command}}
29118 @item @var{cli-command} @expansion{}
29119 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29120 @var{cli-command} is any existing @value{GDBN} CLI command.
29122 @item @var{mi-command} @expansion{}
29123 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29124 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29126 @item @var{token} @expansion{}
29127 "any sequence of digits"
29129 @item @var{option} @expansion{}
29130 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29132 @item @var{parameter} @expansion{}
29133 @code{@var{non-blank-sequence} | @var{c-string}}
29135 @item @var{operation} @expansion{}
29136 @emph{any of the operations described in this chapter}
29138 @item @var{non-blank-sequence} @expansion{}
29139 @emph{anything, provided it doesn't contain special characters such as
29140 "-", @var{nl}, """ and of course " "}
29142 @item @var{c-string} @expansion{}
29143 @code{""" @var{seven-bit-iso-c-string-content} """}
29145 @item @var{nl} @expansion{}
29154 The CLI commands are still handled by the @sc{mi} interpreter; their
29155 output is described below.
29158 The @code{@var{token}}, when present, is passed back when the command
29162 Some @sc{mi} commands accept optional arguments as part of the parameter
29163 list. Each option is identified by a leading @samp{-} (dash) and may be
29164 followed by an optional argument parameter. Options occur first in the
29165 parameter list and can be delimited from normal parameters using
29166 @samp{--} (this is useful when some parameters begin with a dash).
29173 We want easy access to the existing CLI syntax (for debugging).
29176 We want it to be easy to spot a @sc{mi} operation.
29179 @node GDB/MI Output Syntax
29180 @subsection @sc{gdb/mi} Output Syntax
29182 @cindex output syntax of @sc{gdb/mi}
29183 @cindex @sc{gdb/mi}, output syntax
29184 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29185 followed, optionally, by a single result record. This result record
29186 is for the most recent command. The sequence of output records is
29187 terminated by @samp{(gdb)}.
29189 If an input command was prefixed with a @code{@var{token}} then the
29190 corresponding output for that command will also be prefixed by that same
29194 @item @var{output} @expansion{}
29195 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29197 @item @var{result-record} @expansion{}
29198 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29200 @item @var{out-of-band-record} @expansion{}
29201 @code{@var{async-record} | @var{stream-record}}
29203 @item @var{async-record} @expansion{}
29204 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29206 @item @var{exec-async-output} @expansion{}
29207 @code{[ @var{token} ] "*" @var{async-output}}
29209 @item @var{status-async-output} @expansion{}
29210 @code{[ @var{token} ] "+" @var{async-output}}
29212 @item @var{notify-async-output} @expansion{}
29213 @code{[ @var{token} ] "=" @var{async-output}}
29215 @item @var{async-output} @expansion{}
29216 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
29218 @item @var{result-class} @expansion{}
29219 @code{"done" | "running" | "connected" | "error" | "exit"}
29221 @item @var{async-class} @expansion{}
29222 @code{"stopped" | @var{others}} (where @var{others} will be added
29223 depending on the needs---this is still in development).
29225 @item @var{result} @expansion{}
29226 @code{ @var{variable} "=" @var{value}}
29228 @item @var{variable} @expansion{}
29229 @code{ @var{string} }
29231 @item @var{value} @expansion{}
29232 @code{ @var{const} | @var{tuple} | @var{list} }
29234 @item @var{const} @expansion{}
29235 @code{@var{c-string}}
29237 @item @var{tuple} @expansion{}
29238 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29240 @item @var{list} @expansion{}
29241 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29242 @var{result} ( "," @var{result} )* "]" }
29244 @item @var{stream-record} @expansion{}
29245 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29247 @item @var{console-stream-output} @expansion{}
29248 @code{"~" @var{c-string}}
29250 @item @var{target-stream-output} @expansion{}
29251 @code{"@@" @var{c-string}}
29253 @item @var{log-stream-output} @expansion{}
29254 @code{"&" @var{c-string}}
29256 @item @var{nl} @expansion{}
29259 @item @var{token} @expansion{}
29260 @emph{any sequence of digits}.
29268 All output sequences end in a single line containing a period.
29271 The @code{@var{token}} is from the corresponding request. Note that
29272 for all async output, while the token is allowed by the grammar and
29273 may be output by future versions of @value{GDBN} for select async
29274 output messages, it is generally omitted. Frontends should treat
29275 all async output as reporting general changes in the state of the
29276 target and there should be no need to associate async output to any
29280 @cindex status output in @sc{gdb/mi}
29281 @var{status-async-output} contains on-going status information about the
29282 progress of a slow operation. It can be discarded. All status output is
29283 prefixed by @samp{+}.
29286 @cindex async output in @sc{gdb/mi}
29287 @var{exec-async-output} contains asynchronous state change on the target
29288 (stopped, started, disappeared). All async output is prefixed by
29292 @cindex notify output in @sc{gdb/mi}
29293 @var{notify-async-output} contains supplementary information that the
29294 client should handle (e.g., a new breakpoint information). All notify
29295 output is prefixed by @samp{=}.
29298 @cindex console output in @sc{gdb/mi}
29299 @var{console-stream-output} is output that should be displayed as is in the
29300 console. It is the textual response to a CLI command. All the console
29301 output is prefixed by @samp{~}.
29304 @cindex target output in @sc{gdb/mi}
29305 @var{target-stream-output} is the output produced by the target program.
29306 All the target output is prefixed by @samp{@@}.
29309 @cindex log output in @sc{gdb/mi}
29310 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29311 instance messages that should be displayed as part of an error log. All
29312 the log output is prefixed by @samp{&}.
29315 @cindex list output in @sc{gdb/mi}
29316 New @sc{gdb/mi} commands should only output @var{lists} containing
29322 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29323 details about the various output records.
29325 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29326 @node GDB/MI Compatibility with CLI
29327 @section @sc{gdb/mi} Compatibility with CLI
29329 @cindex compatibility, @sc{gdb/mi} and CLI
29330 @cindex @sc{gdb/mi}, compatibility with CLI
29332 For the developers convenience CLI commands can be entered directly,
29333 but there may be some unexpected behaviour. For example, commands
29334 that query the user will behave as if the user replied yes, breakpoint
29335 command lists are not executed and some CLI commands, such as
29336 @code{if}, @code{when} and @code{define}, prompt for further input with
29337 @samp{>}, which is not valid MI output.
29339 This feature may be removed at some stage in the future and it is
29340 recommended that front ends use the @code{-interpreter-exec} command
29341 (@pxref{-interpreter-exec}).
29343 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29344 @node GDB/MI Development and Front Ends
29345 @section @sc{gdb/mi} Development and Front Ends
29346 @cindex @sc{gdb/mi} development
29348 The application which takes the MI output and presents the state of the
29349 program being debugged to the user is called a @dfn{front end}.
29351 Although @sc{gdb/mi} is still incomplete, it is currently being used
29352 by a variety of front ends to @value{GDBN}. This makes it difficult
29353 to introduce new functionality without breaking existing usage. This
29354 section tries to minimize the problems by describing how the protocol
29357 Some changes in MI need not break a carefully designed front end, and
29358 for these the MI version will remain unchanged. The following is a
29359 list of changes that may occur within one level, so front ends should
29360 parse MI output in a way that can handle them:
29364 New MI commands may be added.
29367 New fields may be added to the output of any MI command.
29370 The range of values for fields with specified values, e.g.,
29371 @code{in_scope} (@pxref{-var-update}) may be extended.
29373 @c The format of field's content e.g type prefix, may change so parse it
29374 @c at your own risk. Yes, in general?
29376 @c The order of fields may change? Shouldn't really matter but it might
29377 @c resolve inconsistencies.
29380 If the changes are likely to break front ends, the MI version level
29381 will be increased by one. This will allow the front end to parse the
29382 output according to the MI version. Apart from mi0, new versions of
29383 @value{GDBN} will not support old versions of MI and it will be the
29384 responsibility of the front end to work with the new one.
29386 @c Starting with mi3, add a new command -mi-version that prints the MI
29389 The best way to avoid unexpected changes in MI that might break your front
29390 end is to make your project known to @value{GDBN} developers and
29391 follow development on @email{gdb@@sourceware.org} and
29392 @email{gdb-patches@@sourceware.org}.
29393 @cindex mailing lists
29395 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29396 @node GDB/MI Output Records
29397 @section @sc{gdb/mi} Output Records
29400 * GDB/MI Result Records::
29401 * GDB/MI Stream Records::
29402 * GDB/MI Async Records::
29403 * GDB/MI Breakpoint Information::
29404 * GDB/MI Frame Information::
29405 * GDB/MI Thread Information::
29406 * GDB/MI Ada Exception Information::
29409 @node GDB/MI Result Records
29410 @subsection @sc{gdb/mi} Result Records
29412 @cindex result records in @sc{gdb/mi}
29413 @cindex @sc{gdb/mi}, result records
29414 In addition to a number of out-of-band notifications, the response to a
29415 @sc{gdb/mi} command includes one of the following result indications:
29419 @item "^done" [ "," @var{results} ]
29420 The synchronous operation was successful, @code{@var{results}} are the return
29425 This result record is equivalent to @samp{^done}. Historically, it
29426 was output instead of @samp{^done} if the command has resumed the
29427 target. This behaviour is maintained for backward compatibility, but
29428 all frontends should treat @samp{^done} and @samp{^running}
29429 identically and rely on the @samp{*running} output record to determine
29430 which threads are resumed.
29434 @value{GDBN} has connected to a remote target.
29436 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29438 The operation failed. The @code{msg=@var{c-string}} variable contains
29439 the corresponding error message.
29441 If present, the @code{code=@var{c-string}} variable provides an error
29442 code on which consumers can rely on to detect the corresponding
29443 error condition. At present, only one error code is defined:
29446 @item "undefined-command"
29447 Indicates that the command causing the error does not exist.
29452 @value{GDBN} has terminated.
29456 @node GDB/MI Stream Records
29457 @subsection @sc{gdb/mi} Stream Records
29459 @cindex @sc{gdb/mi}, stream records
29460 @cindex stream records in @sc{gdb/mi}
29461 @value{GDBN} internally maintains a number of output streams: the console, the
29462 target, and the log. The output intended for each of these streams is
29463 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29465 Each stream record begins with a unique @dfn{prefix character} which
29466 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29467 Syntax}). In addition to the prefix, each stream record contains a
29468 @code{@var{string-output}}. This is either raw text (with an implicit new
29469 line) or a quoted C string (which does not contain an implicit newline).
29472 @item "~" @var{string-output}
29473 The console output stream contains text that should be displayed in the
29474 CLI console window. It contains the textual responses to CLI commands.
29476 @item "@@" @var{string-output}
29477 The target output stream contains any textual output from the running
29478 target. This is only present when GDB's event loop is truly
29479 asynchronous, which is currently only the case for remote targets.
29481 @item "&" @var{string-output}
29482 The log stream contains debugging messages being produced by @value{GDBN}'s
29486 @node GDB/MI Async Records
29487 @subsection @sc{gdb/mi} Async Records
29489 @cindex async records in @sc{gdb/mi}
29490 @cindex @sc{gdb/mi}, async records
29491 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29492 additional changes that have occurred. Those changes can either be a
29493 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29494 target activity (e.g., target stopped).
29496 The following is the list of possible async records:
29500 @item *running,thread-id="@var{thread}"
29501 The target is now running. The @var{thread} field tells which
29502 specific thread is now running, and can be @samp{all} if all threads
29503 are running. The frontend should assume that no interaction with a
29504 running thread is possible after this notification is produced.
29505 The frontend should not assume that this notification is output
29506 only once for any command. @value{GDBN} may emit this notification
29507 several times, either for different threads, because it cannot resume
29508 all threads together, or even for a single thread, if the thread must
29509 be stepped though some code before letting it run freely.
29511 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29512 The target has stopped. The @var{reason} field can have one of the
29516 @item breakpoint-hit
29517 A breakpoint was reached.
29518 @item watchpoint-trigger
29519 A watchpoint was triggered.
29520 @item read-watchpoint-trigger
29521 A read watchpoint was triggered.
29522 @item access-watchpoint-trigger
29523 An access watchpoint was triggered.
29524 @item function-finished
29525 An -exec-finish or similar CLI command was accomplished.
29526 @item location-reached
29527 An -exec-until or similar CLI command was accomplished.
29528 @item watchpoint-scope
29529 A watchpoint has gone out of scope.
29530 @item end-stepping-range
29531 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29532 similar CLI command was accomplished.
29533 @item exited-signalled
29534 The inferior exited because of a signal.
29536 The inferior exited.
29537 @item exited-normally
29538 The inferior exited normally.
29539 @item signal-received
29540 A signal was received by the inferior.
29542 The inferior has stopped due to a library being loaded or unloaded.
29543 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29544 set or when a @code{catch load} or @code{catch unload} catchpoint is
29545 in use (@pxref{Set Catchpoints}).
29547 The inferior has forked. This is reported when @code{catch fork}
29548 (@pxref{Set Catchpoints}) has been used.
29550 The inferior has vforked. This is reported in when @code{catch vfork}
29551 (@pxref{Set Catchpoints}) has been used.
29552 @item syscall-entry
29553 The inferior entered a system call. This is reported when @code{catch
29554 syscall} (@pxref{Set Catchpoints}) has been used.
29555 @item syscall-entry
29556 The inferior returned from a system call. This is reported when
29557 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29559 The inferior called @code{exec}. This is reported when @code{catch exec}
29560 (@pxref{Set Catchpoints}) has been used.
29563 The @var{id} field identifies the thread that directly caused the stop
29564 -- for example by hitting a breakpoint. Depending on whether all-stop
29565 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29566 stop all threads, or only the thread that directly triggered the stop.
29567 If all threads are stopped, the @var{stopped} field will have the
29568 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29569 field will be a list of thread identifiers. Presently, this list will
29570 always include a single thread, but frontend should be prepared to see
29571 several threads in the list. The @var{core} field reports the
29572 processor core on which the stop event has happened. This field may be absent
29573 if such information is not available.
29575 @item =thread-group-added,id="@var{id}"
29576 @itemx =thread-group-removed,id="@var{id}"
29577 A thread group was either added or removed. The @var{id} field
29578 contains the @value{GDBN} identifier of the thread group. When a thread
29579 group is added, it generally might not be associated with a running
29580 process. When a thread group is removed, its id becomes invalid and
29581 cannot be used in any way.
29583 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29584 A thread group became associated with a running program,
29585 either because the program was just started or the thread group
29586 was attached to a program. The @var{id} field contains the
29587 @value{GDBN} identifier of the thread group. The @var{pid} field
29588 contains process identifier, specific to the operating system.
29590 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29591 A thread group is no longer associated with a running program,
29592 either because the program has exited, or because it was detached
29593 from. The @var{id} field contains the @value{GDBN} identifier of the
29594 thread group. @var{code} is the exit code of the inferior; it exists
29595 only when the inferior exited with some code.
29597 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29598 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29599 A thread either was created, or has exited. The @var{id} field
29600 contains the @value{GDBN} identifier of the thread. The @var{gid}
29601 field identifies the thread group this thread belongs to.
29603 @item =thread-selected,id="@var{id}"
29604 Informs that the selected thread was changed as result of the last
29605 command. This notification is not emitted as result of @code{-thread-select}
29606 command but is emitted whenever an MI command that is not documented
29607 to change the selected thread actually changes it. In particular,
29608 invoking, directly or indirectly (via user-defined command), the CLI
29609 @code{thread} command, will generate this notification.
29611 We suggest that in response to this notification, front ends
29612 highlight the selected thread and cause subsequent commands to apply to
29615 @item =library-loaded,...
29616 Reports that a new library file was loaded by the program. This
29617 notification has 4 fields---@var{id}, @var{target-name},
29618 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29619 opaque identifier of the library. For remote debugging case,
29620 @var{target-name} and @var{host-name} fields give the name of the
29621 library file on the target, and on the host respectively. For native
29622 debugging, both those fields have the same value. The
29623 @var{symbols-loaded} field is emitted only for backward compatibility
29624 and should not be relied on to convey any useful information. The
29625 @var{thread-group} field, if present, specifies the id of the thread
29626 group in whose context the library was loaded. If the field is
29627 absent, it means the library was loaded in the context of all present
29630 @item =library-unloaded,...
29631 Reports that a library was unloaded by the program. This notification
29632 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29633 the same meaning as for the @code{=library-loaded} notification.
29634 The @var{thread-group} field, if present, specifies the id of the
29635 thread group in whose context the library was unloaded. If the field is
29636 absent, it means the library was unloaded in the context of all present
29639 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29640 @itemx =traceframe-changed,end
29641 Reports that the trace frame was changed and its new number is
29642 @var{tfnum}. The number of the tracepoint associated with this trace
29643 frame is @var{tpnum}.
29645 @item =tsv-created,name=@var{name},initial=@var{initial}
29646 Reports that the new trace state variable @var{name} is created with
29647 initial value @var{initial}.
29649 @item =tsv-deleted,name=@var{name}
29650 @itemx =tsv-deleted
29651 Reports that the trace state variable @var{name} is deleted or all
29652 trace state variables are deleted.
29654 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29655 Reports that the trace state variable @var{name} is modified with
29656 the initial value @var{initial}. The current value @var{current} of
29657 trace state variable is optional and is reported if the current
29658 value of trace state variable is known.
29660 @item =breakpoint-created,bkpt=@{...@}
29661 @itemx =breakpoint-modified,bkpt=@{...@}
29662 @itemx =breakpoint-deleted,id=@var{number}
29663 Reports that a breakpoint was created, modified, or deleted,
29664 respectively. Only user-visible breakpoints are reported to the MI
29667 The @var{bkpt} argument is of the same form as returned by the various
29668 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29669 @var{number} is the ordinal number of the breakpoint.
29671 Note that if a breakpoint is emitted in the result record of a
29672 command, then it will not also be emitted in an async record.
29674 @item =record-started,thread-group="@var{id}"
29675 @itemx =record-stopped,thread-group="@var{id}"
29676 Execution log recording was either started or stopped on an
29677 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29678 group corresponding to the affected inferior.
29680 @item =cmd-param-changed,param=@var{param},value=@var{value}
29681 Reports that a parameter of the command @code{set @var{param}} is
29682 changed to @var{value}. In the multi-word @code{set} command,
29683 the @var{param} is the whole parameter list to @code{set} command.
29684 For example, In command @code{set check type on}, @var{param}
29685 is @code{check type} and @var{value} is @code{on}.
29687 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29688 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29689 written in an inferior. The @var{id} is the identifier of the
29690 thread group corresponding to the affected inferior. The optional
29691 @code{type="code"} part is reported if the memory written to holds
29695 @node GDB/MI Breakpoint Information
29696 @subsection @sc{gdb/mi} Breakpoint Information
29698 When @value{GDBN} reports information about a breakpoint, a
29699 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29704 The breakpoint number. For a breakpoint that represents one location
29705 of a multi-location breakpoint, this will be a dotted pair, like
29709 The type of the breakpoint. For ordinary breakpoints this will be
29710 @samp{breakpoint}, but many values are possible.
29713 If the type of the breakpoint is @samp{catchpoint}, then this
29714 indicates the exact type of catchpoint.
29717 This is the breakpoint disposition---either @samp{del}, meaning that
29718 the breakpoint will be deleted at the next stop, or @samp{keep},
29719 meaning that the breakpoint will not be deleted.
29722 This indicates whether the breakpoint is enabled, in which case the
29723 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29724 Note that this is not the same as the field @code{enable}.
29727 The address of the breakpoint. This may be a hexidecimal number,
29728 giving the address; or the string @samp{<PENDING>}, for a pending
29729 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29730 multiple locations. This field will not be present if no address can
29731 be determined. For example, a watchpoint does not have an address.
29734 If known, the function in which the breakpoint appears.
29735 If not known, this field is not present.
29738 The name of the source file which contains this function, if known.
29739 If not known, this field is not present.
29742 The full file name of the source file which contains this function, if
29743 known. If not known, this field is not present.
29746 The line number at which this breakpoint appears, if known.
29747 If not known, this field is not present.
29750 If the source file is not known, this field may be provided. If
29751 provided, this holds the address of the breakpoint, possibly followed
29755 If this breakpoint is pending, this field is present and holds the
29756 text used to set the breakpoint, as entered by the user.
29759 Where this breakpoint's condition is evaluated, either @samp{host} or
29763 If this is a thread-specific breakpoint, then this identifies the
29764 thread in which the breakpoint can trigger.
29767 If this breakpoint is restricted to a particular Ada task, then this
29768 field will hold the task identifier.
29771 If the breakpoint is conditional, this is the condition expression.
29774 The ignore count of the breakpoint.
29777 The enable count of the breakpoint.
29779 @item traceframe-usage
29782 @item static-tracepoint-marker-string-id
29783 For a static tracepoint, the name of the static tracepoint marker.
29786 For a masked watchpoint, this is the mask.
29789 A tracepoint's pass count.
29791 @item original-location
29792 The location of the breakpoint as originally specified by the user.
29793 This field is optional.
29796 The number of times the breakpoint has been hit.
29799 This field is only given for tracepoints. This is either @samp{y},
29800 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29804 Some extra data, the exact contents of which are type-dependent.
29808 For example, here is what the output of @code{-break-insert}
29809 (@pxref{GDB/MI Breakpoint Commands}) might be:
29812 -> -break-insert main
29813 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29814 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29815 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29820 @node GDB/MI Frame Information
29821 @subsection @sc{gdb/mi} Frame Information
29823 Response from many MI commands includes an information about stack
29824 frame. This information is a tuple that may have the following
29829 The level of the stack frame. The innermost frame has the level of
29830 zero. This field is always present.
29833 The name of the function corresponding to the frame. This field may
29834 be absent if @value{GDBN} is unable to determine the function name.
29837 The code address for the frame. This field is always present.
29840 The name of the source files that correspond to the frame's code
29841 address. This field may be absent.
29844 The source line corresponding to the frames' code address. This field
29848 The name of the binary file (either executable or shared library) the
29849 corresponds to the frame's code address. This field may be absent.
29853 @node GDB/MI Thread Information
29854 @subsection @sc{gdb/mi} Thread Information
29856 Whenever @value{GDBN} has to report an information about a thread, it
29857 uses a tuple with the following fields:
29861 The numeric id assigned to the thread by @value{GDBN}. This field is
29865 Target-specific string identifying the thread. This field is always present.
29868 Additional information about the thread provided by the target.
29869 It is supposed to be human-readable and not interpreted by the
29870 frontend. This field is optional.
29873 Either @samp{stopped} or @samp{running}, depending on whether the
29874 thread is presently running. This field is always present.
29877 The value of this field is an integer number of the processor core the
29878 thread was last seen on. This field is optional.
29881 @node GDB/MI Ada Exception Information
29882 @subsection @sc{gdb/mi} Ada Exception Information
29884 Whenever a @code{*stopped} record is emitted because the program
29885 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29886 @value{GDBN} provides the name of the exception that was raised via
29887 the @code{exception-name} field.
29889 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29890 @node GDB/MI Simple Examples
29891 @section Simple Examples of @sc{gdb/mi} Interaction
29892 @cindex @sc{gdb/mi}, simple examples
29894 This subsection presents several simple examples of interaction using
29895 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29896 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29897 the output received from @sc{gdb/mi}.
29899 Note the line breaks shown in the examples are here only for
29900 readability, they don't appear in the real output.
29902 @subheading Setting a Breakpoint
29904 Setting a breakpoint generates synchronous output which contains detailed
29905 information of the breakpoint.
29908 -> -break-insert main
29909 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29910 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29911 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29916 @subheading Program Execution
29918 Program execution generates asynchronous records and MI gives the
29919 reason that execution stopped.
29925 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29926 frame=@{addr="0x08048564",func="main",
29927 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29928 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29933 <- *stopped,reason="exited-normally"
29937 @subheading Quitting @value{GDBN}
29939 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29947 Please note that @samp{^exit} is printed immediately, but it might
29948 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29949 performs necessary cleanups, including killing programs being debugged
29950 or disconnecting from debug hardware, so the frontend should wait till
29951 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29952 fails to exit in reasonable time.
29954 @subheading A Bad Command
29956 Here's what happens if you pass a non-existent command:
29960 <- ^error,msg="Undefined MI command: rubbish"
29965 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29966 @node GDB/MI Command Description Format
29967 @section @sc{gdb/mi} Command Description Format
29969 The remaining sections describe blocks of commands. Each block of
29970 commands is laid out in a fashion similar to this section.
29972 @subheading Motivation
29974 The motivation for this collection of commands.
29976 @subheading Introduction
29978 A brief introduction to this collection of commands as a whole.
29980 @subheading Commands
29982 For each command in the block, the following is described:
29984 @subsubheading Synopsis
29987 -command @var{args}@dots{}
29990 @subsubheading Result
29992 @subsubheading @value{GDBN} Command
29994 The corresponding @value{GDBN} CLI command(s), if any.
29996 @subsubheading Example
29998 Example(s) formatted for readability. Some of the described commands have
29999 not been implemented yet and these are labeled N.A.@: (not available).
30002 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30003 @node GDB/MI Breakpoint Commands
30004 @section @sc{gdb/mi} Breakpoint Commands
30006 @cindex breakpoint commands for @sc{gdb/mi}
30007 @cindex @sc{gdb/mi}, breakpoint commands
30008 This section documents @sc{gdb/mi} commands for manipulating
30011 @subheading The @code{-break-after} Command
30012 @findex -break-after
30014 @subsubheading Synopsis
30017 -break-after @var{number} @var{count}
30020 The breakpoint number @var{number} is not in effect until it has been
30021 hit @var{count} times. To see how this is reflected in the output of
30022 the @samp{-break-list} command, see the description of the
30023 @samp{-break-list} command below.
30025 @subsubheading @value{GDBN} Command
30027 The corresponding @value{GDBN} command is @samp{ignore}.
30029 @subsubheading Example
30034 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30035 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30036 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30044 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30045 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30046 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30047 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30048 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30049 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30050 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30051 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30052 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30053 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30058 @subheading The @code{-break-catch} Command
30059 @findex -break-catch
30062 @subheading The @code{-break-commands} Command
30063 @findex -break-commands
30065 @subsubheading Synopsis
30068 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30071 Specifies the CLI commands that should be executed when breakpoint
30072 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30073 are the commands. If no command is specified, any previously-set
30074 commands are cleared. @xref{Break Commands}. Typical use of this
30075 functionality is tracing a program, that is, printing of values of
30076 some variables whenever breakpoint is hit and then continuing.
30078 @subsubheading @value{GDBN} Command
30080 The corresponding @value{GDBN} command is @samp{commands}.
30082 @subsubheading Example
30087 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30088 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30089 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30092 -break-commands 1 "print v" "continue"
30097 @subheading The @code{-break-condition} Command
30098 @findex -break-condition
30100 @subsubheading Synopsis
30103 -break-condition @var{number} @var{expr}
30106 Breakpoint @var{number} will stop the program only if the condition in
30107 @var{expr} is true. The condition becomes part of the
30108 @samp{-break-list} output (see the description of the @samp{-break-list}
30111 @subsubheading @value{GDBN} Command
30113 The corresponding @value{GDBN} command is @samp{condition}.
30115 @subsubheading Example
30119 -break-condition 1 1
30123 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30124 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30125 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30126 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30127 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30128 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30129 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30130 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30131 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30132 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30136 @subheading The @code{-break-delete} Command
30137 @findex -break-delete
30139 @subsubheading Synopsis
30142 -break-delete ( @var{breakpoint} )+
30145 Delete the breakpoint(s) whose number(s) are specified in the argument
30146 list. This is obviously reflected in the breakpoint list.
30148 @subsubheading @value{GDBN} Command
30150 The corresponding @value{GDBN} command is @samp{delete}.
30152 @subsubheading Example
30160 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30161 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30162 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30163 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30164 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30165 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30166 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30171 @subheading The @code{-break-disable} Command
30172 @findex -break-disable
30174 @subsubheading Synopsis
30177 -break-disable ( @var{breakpoint} )+
30180 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30181 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30183 @subsubheading @value{GDBN} Command
30185 The corresponding @value{GDBN} command is @samp{disable}.
30187 @subsubheading Example
30195 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30196 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30197 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30198 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30199 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30200 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30201 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30202 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30203 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30204 line="5",thread-groups=["i1"],times="0"@}]@}
30208 @subheading The @code{-break-enable} Command
30209 @findex -break-enable
30211 @subsubheading Synopsis
30214 -break-enable ( @var{breakpoint} )+
30217 Enable (previously disabled) @var{breakpoint}(s).
30219 @subsubheading @value{GDBN} Command
30221 The corresponding @value{GDBN} command is @samp{enable}.
30223 @subsubheading Example
30231 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30232 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30233 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30234 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30235 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30236 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30237 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30238 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30239 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30240 line="5",thread-groups=["i1"],times="0"@}]@}
30244 @subheading The @code{-break-info} Command
30245 @findex -break-info
30247 @subsubheading Synopsis
30250 -break-info @var{breakpoint}
30254 Get information about a single breakpoint.
30256 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30257 Information}, for details on the format of each breakpoint in the
30260 @subsubheading @value{GDBN} Command
30262 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30264 @subsubheading Example
30267 @subheading The @code{-break-insert} Command
30268 @findex -break-insert
30270 @subsubheading Synopsis
30273 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30274 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30275 [ -p @var{thread-id} ] [ @var{location} ]
30279 If specified, @var{location}, can be one of:
30286 @item filename:linenum
30287 @item filename:function
30291 The possible optional parameters of this command are:
30295 Insert a temporary breakpoint.
30297 Insert a hardware breakpoint.
30299 If @var{location} cannot be parsed (for example if it
30300 refers to unknown files or functions), create a pending
30301 breakpoint. Without this flag, @value{GDBN} will report
30302 an error, and won't create a breakpoint, if @var{location}
30305 Create a disabled breakpoint.
30307 Create a tracepoint. @xref{Tracepoints}. When this parameter
30308 is used together with @samp{-h}, a fast tracepoint is created.
30309 @item -c @var{condition}
30310 Make the breakpoint conditional on @var{condition}.
30311 @item -i @var{ignore-count}
30312 Initialize the @var{ignore-count}.
30313 @item -p @var{thread-id}
30314 Restrict the breakpoint to the specified @var{thread-id}.
30317 @subsubheading Result
30319 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30320 resulting breakpoint.
30322 Note: this format is open to change.
30323 @c An out-of-band breakpoint instead of part of the result?
30325 @subsubheading @value{GDBN} Command
30327 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30328 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30330 @subsubheading Example
30335 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30336 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30339 -break-insert -t foo
30340 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30341 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30345 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30346 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30347 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30348 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30349 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30350 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30351 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30352 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30353 addr="0x0001072c", func="main",file="recursive2.c",
30354 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30356 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30357 addr="0x00010774",func="foo",file="recursive2.c",
30358 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30361 @c -break-insert -r foo.*
30362 @c ~int foo(int, int);
30363 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30364 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30369 @subheading The @code{-dprintf-insert} Command
30370 @findex -dprintf-insert
30372 @subsubheading Synopsis
30375 -dprintf-insert [ -t ] [ -f ] [ -d ]
30376 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30377 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30382 If specified, @var{location}, can be one of:
30385 @item @var{function}
30388 @c @item @var{linenum}
30389 @item @var{filename}:@var{linenum}
30390 @item @var{filename}:function
30391 @item *@var{address}
30394 The possible optional parameters of this command are:
30398 Insert a temporary breakpoint.
30400 If @var{location} cannot be parsed (for example, if it
30401 refers to unknown files or functions), create a pending
30402 breakpoint. Without this flag, @value{GDBN} will report
30403 an error, and won't create a breakpoint, if @var{location}
30406 Create a disabled breakpoint.
30407 @item -c @var{condition}
30408 Make the breakpoint conditional on @var{condition}.
30409 @item -i @var{ignore-count}
30410 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30411 to @var{ignore-count}.
30412 @item -p @var{thread-id}
30413 Restrict the breakpoint to the specified @var{thread-id}.
30416 @subsubheading Result
30418 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30419 resulting breakpoint.
30421 @c An out-of-band breakpoint instead of part of the result?
30423 @subsubheading @value{GDBN} Command
30425 The corresponding @value{GDBN} command is @samp{dprintf}.
30427 @subsubheading Example
30431 4-dprintf-insert foo "At foo entry\n"
30432 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30433 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30434 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30435 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30436 original-location="foo"@}
30438 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30439 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30440 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30441 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30442 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30443 original-location="mi-dprintf.c:26"@}
30447 @subheading The @code{-break-list} Command
30448 @findex -break-list
30450 @subsubheading Synopsis
30456 Displays the list of inserted breakpoints, showing the following fields:
30460 number of the breakpoint
30462 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30464 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30467 is the breakpoint enabled or no: @samp{y} or @samp{n}
30469 memory location at which the breakpoint is set
30471 logical location of the breakpoint, expressed by function name, file
30473 @item Thread-groups
30474 list of thread groups to which this breakpoint applies
30476 number of times the breakpoint has been hit
30479 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30480 @code{body} field is an empty list.
30482 @subsubheading @value{GDBN} Command
30484 The corresponding @value{GDBN} command is @samp{info break}.
30486 @subsubheading Example
30491 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30492 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30493 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30494 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30495 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30496 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30497 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30498 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30499 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30501 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30502 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30503 line="13",thread-groups=["i1"],times="0"@}]@}
30507 Here's an example of the result when there are no breakpoints:
30512 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30513 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30514 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30515 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30516 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30517 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30518 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30523 @subheading The @code{-break-passcount} Command
30524 @findex -break-passcount
30526 @subsubheading Synopsis
30529 -break-passcount @var{tracepoint-number} @var{passcount}
30532 Set the passcount for tracepoint @var{tracepoint-number} to
30533 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30534 is not a tracepoint, error is emitted. This corresponds to CLI
30535 command @samp{passcount}.
30537 @subheading The @code{-break-watch} Command
30538 @findex -break-watch
30540 @subsubheading Synopsis
30543 -break-watch [ -a | -r ]
30546 Create a watchpoint. With the @samp{-a} option it will create an
30547 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30548 read from or on a write to the memory location. With the @samp{-r}
30549 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30550 trigger only when the memory location is accessed for reading. Without
30551 either of the options, the watchpoint created is a regular watchpoint,
30552 i.e., it will trigger when the memory location is accessed for writing.
30553 @xref{Set Watchpoints, , Setting Watchpoints}.
30555 Note that @samp{-break-list} will report a single list of watchpoints and
30556 breakpoints inserted.
30558 @subsubheading @value{GDBN} Command
30560 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30563 @subsubheading Example
30565 Setting a watchpoint on a variable in the @code{main} function:
30570 ^done,wpt=@{number="2",exp="x"@}
30575 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30576 value=@{old="-268439212",new="55"@},
30577 frame=@{func="main",args=[],file="recursive2.c",
30578 fullname="/home/foo/bar/recursive2.c",line="5"@}
30582 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30583 the program execution twice: first for the variable changing value, then
30584 for the watchpoint going out of scope.
30589 ^done,wpt=@{number="5",exp="C"@}
30594 *stopped,reason="watchpoint-trigger",
30595 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30596 frame=@{func="callee4",args=[],
30597 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30598 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30603 *stopped,reason="watchpoint-scope",wpnum="5",
30604 frame=@{func="callee3",args=[@{name="strarg",
30605 value="0x11940 \"A string argument.\""@}],
30606 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30607 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30611 Listing breakpoints and watchpoints, at different points in the program
30612 execution. Note that once the watchpoint goes out of scope, it is
30618 ^done,wpt=@{number="2",exp="C"@}
30621 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30622 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30623 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30624 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30625 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30626 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30627 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30628 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30629 addr="0x00010734",func="callee4",
30630 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30631 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30633 bkpt=@{number="2",type="watchpoint",disp="keep",
30634 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30639 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30640 value=@{old="-276895068",new="3"@},
30641 frame=@{func="callee4",args=[],
30642 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30643 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30646 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30647 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30648 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30649 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30650 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30651 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30652 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30653 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30654 addr="0x00010734",func="callee4",
30655 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30656 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30658 bkpt=@{number="2",type="watchpoint",disp="keep",
30659 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30663 ^done,reason="watchpoint-scope",wpnum="2",
30664 frame=@{func="callee3",args=[@{name="strarg",
30665 value="0x11940 \"A string argument.\""@}],
30666 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30667 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30670 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30671 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30672 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30673 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30674 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30675 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30676 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30677 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30678 addr="0x00010734",func="callee4",
30679 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30680 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30681 thread-groups=["i1"],times="1"@}]@}
30686 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30687 @node GDB/MI Catchpoint Commands
30688 @section @sc{gdb/mi} Catchpoint Commands
30690 This section documents @sc{gdb/mi} commands for manipulating
30694 * Shared Library GDB/MI Catchpoint Commands::
30695 * Ada Exception GDB/MI Catchpoint Commands::
30698 @node Shared Library GDB/MI Catchpoint Commands
30699 @subsection Shared Library @sc{gdb/mi} Catchpoints
30701 @subheading The @code{-catch-load} Command
30702 @findex -catch-load
30704 @subsubheading Synopsis
30707 -catch-load [ -t ] [ -d ] @var{regexp}
30710 Add a catchpoint for library load events. If the @samp{-t} option is used,
30711 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30712 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30713 in a disabled state. The @samp{regexp} argument is a regular
30714 expression used to match the name of the loaded library.
30717 @subsubheading @value{GDBN} Command
30719 The corresponding @value{GDBN} command is @samp{catch load}.
30721 @subsubheading Example
30724 -catch-load -t foo.so
30725 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30726 what="load of library matching foo.so",catch-type="load",times="0"@}
30731 @subheading The @code{-catch-unload} Command
30732 @findex -catch-unload
30734 @subsubheading Synopsis
30737 -catch-unload [ -t ] [ -d ] @var{regexp}
30740 Add a catchpoint for library unload events. If the @samp{-t} option is
30741 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30742 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30743 created in a disabled state. The @samp{regexp} argument is a regular
30744 expression used to match the name of the unloaded library.
30746 @subsubheading @value{GDBN} Command
30748 The corresponding @value{GDBN} command is @samp{catch unload}.
30750 @subsubheading Example
30753 -catch-unload -d bar.so
30754 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30755 what="load of library matching bar.so",catch-type="unload",times="0"@}
30759 @node Ada Exception GDB/MI Catchpoint Commands
30760 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30762 The following @sc{gdb/mi} commands can be used to create catchpoints
30763 that stop the execution when Ada exceptions are being raised.
30765 @subheading The @code{-catch-assert} Command
30766 @findex -catch-assert
30768 @subsubheading Synopsis
30771 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30774 Add a catchpoint for failed Ada assertions.
30776 The possible optional parameters for this command are:
30779 @item -c @var{condition}
30780 Make the catchpoint conditional on @var{condition}.
30782 Create a disabled catchpoint.
30784 Create a temporary catchpoint.
30787 @subsubheading @value{GDBN} Command
30789 The corresponding @value{GDBN} command is @samp{catch assert}.
30791 @subsubheading Example
30795 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30796 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30797 thread-groups=["i1"],times="0",
30798 original-location="__gnat_debug_raise_assert_failure"@}
30802 @subheading The @code{-catch-exception} Command
30803 @findex -catch-exception
30805 @subsubheading Synopsis
30808 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30812 Add a catchpoint stopping when Ada exceptions are raised.
30813 By default, the command stops the program when any Ada exception
30814 gets raised. But it is also possible, by using some of the
30815 optional parameters described below, to create more selective
30818 The possible optional parameters for this command are:
30821 @item -c @var{condition}
30822 Make the catchpoint conditional on @var{condition}.
30824 Create a disabled catchpoint.
30825 @item -e @var{exception-name}
30826 Only stop when @var{exception-name} is raised. This option cannot
30827 be used combined with @samp{-u}.
30829 Create a temporary catchpoint.
30831 Stop only when an unhandled exception gets raised. This option
30832 cannot be used combined with @samp{-e}.
30835 @subsubheading @value{GDBN} Command
30837 The corresponding @value{GDBN} commands are @samp{catch exception}
30838 and @samp{catch exception unhandled}.
30840 @subsubheading Example
30843 -catch-exception -e Program_Error
30844 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30845 enabled="y",addr="0x0000000000404874",
30846 what="`Program_Error' Ada exception", thread-groups=["i1"],
30847 times="0",original-location="__gnat_debug_raise_exception"@}
30851 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30852 @node GDB/MI Program Context
30853 @section @sc{gdb/mi} Program Context
30855 @subheading The @code{-exec-arguments} Command
30856 @findex -exec-arguments
30859 @subsubheading Synopsis
30862 -exec-arguments @var{args}
30865 Set the inferior program arguments, to be used in the next
30868 @subsubheading @value{GDBN} Command
30870 The corresponding @value{GDBN} command is @samp{set args}.
30872 @subsubheading Example
30876 -exec-arguments -v word
30883 @subheading The @code{-exec-show-arguments} Command
30884 @findex -exec-show-arguments
30886 @subsubheading Synopsis
30889 -exec-show-arguments
30892 Print the arguments of the program.
30894 @subsubheading @value{GDBN} Command
30896 The corresponding @value{GDBN} command is @samp{show args}.
30898 @subsubheading Example
30903 @subheading The @code{-environment-cd} Command
30904 @findex -environment-cd
30906 @subsubheading Synopsis
30909 -environment-cd @var{pathdir}
30912 Set @value{GDBN}'s working directory.
30914 @subsubheading @value{GDBN} Command
30916 The corresponding @value{GDBN} command is @samp{cd}.
30918 @subsubheading Example
30922 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30928 @subheading The @code{-environment-directory} Command
30929 @findex -environment-directory
30931 @subsubheading Synopsis
30934 -environment-directory [ -r ] [ @var{pathdir} ]+
30937 Add directories @var{pathdir} to beginning of search path for source files.
30938 If the @samp{-r} option is used, the search path is reset to the default
30939 search path. If directories @var{pathdir} are supplied in addition to the
30940 @samp{-r} option, the search path is first reset and then addition
30942 Multiple directories may be specified, separated by blanks. Specifying
30943 multiple directories in a single command
30944 results in the directories added to the beginning of the
30945 search path in the same order they were presented in the command.
30946 If blanks are needed as
30947 part of a directory name, double-quotes should be used around
30948 the name. In the command output, the path will show up separated
30949 by the system directory-separator character. The directory-separator
30950 character must not be used
30951 in any directory name.
30952 If no directories are specified, the current search path is displayed.
30954 @subsubheading @value{GDBN} Command
30956 The corresponding @value{GDBN} command is @samp{dir}.
30958 @subsubheading Example
30962 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30963 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30965 -environment-directory ""
30966 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30968 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30969 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30971 -environment-directory -r
30972 ^done,source-path="$cdir:$cwd"
30977 @subheading The @code{-environment-path} Command
30978 @findex -environment-path
30980 @subsubheading Synopsis
30983 -environment-path [ -r ] [ @var{pathdir} ]+
30986 Add directories @var{pathdir} to beginning of search path for object files.
30987 If the @samp{-r} option is used, the search path is reset to the original
30988 search path that existed at gdb start-up. If directories @var{pathdir} are
30989 supplied in addition to the
30990 @samp{-r} option, the search path is first reset and then addition
30992 Multiple directories may be specified, separated by blanks. Specifying
30993 multiple directories in a single command
30994 results in the directories added to the beginning of the
30995 search path in the same order they were presented in the command.
30996 If blanks are needed as
30997 part of a directory name, double-quotes should be used around
30998 the name. In the command output, the path will show up separated
30999 by the system directory-separator character. The directory-separator
31000 character must not be used
31001 in any directory name.
31002 If no directories are specified, the current path is displayed.
31005 @subsubheading @value{GDBN} Command
31007 The corresponding @value{GDBN} command is @samp{path}.
31009 @subsubheading Example
31014 ^done,path="/usr/bin"
31016 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31017 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31019 -environment-path -r /usr/local/bin
31020 ^done,path="/usr/local/bin:/usr/bin"
31025 @subheading The @code{-environment-pwd} Command
31026 @findex -environment-pwd
31028 @subsubheading Synopsis
31034 Show the current working directory.
31036 @subsubheading @value{GDBN} Command
31038 The corresponding @value{GDBN} command is @samp{pwd}.
31040 @subsubheading Example
31045 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31049 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31050 @node GDB/MI Thread Commands
31051 @section @sc{gdb/mi} Thread Commands
31054 @subheading The @code{-thread-info} Command
31055 @findex -thread-info
31057 @subsubheading Synopsis
31060 -thread-info [ @var{thread-id} ]
31063 Reports information about either a specific thread, if
31064 the @var{thread-id} parameter is present, or about all
31065 threads. When printing information about all threads,
31066 also reports the current thread.
31068 @subsubheading @value{GDBN} Command
31070 The @samp{info thread} command prints the same information
31073 @subsubheading Result
31075 The result is a list of threads. The following attributes are
31076 defined for a given thread:
31080 This field exists only for the current thread. It has the value @samp{*}.
31083 The identifier that @value{GDBN} uses to refer to the thread.
31086 The identifier that the target uses to refer to the thread.
31089 Extra information about the thread, in a target-specific format. This
31093 The name of the thread. If the user specified a name using the
31094 @code{thread name} command, then this name is given. Otherwise, if
31095 @value{GDBN} can extract the thread name from the target, then that
31096 name is given. If @value{GDBN} cannot find the thread name, then this
31100 The stack frame currently executing in the thread.
31103 The thread's state. The @samp{state} field may have the following
31108 The thread is stopped. Frame information is available for stopped
31112 The thread is running. There's no frame information for running
31118 If @value{GDBN} can find the CPU core on which this thread is running,
31119 then this field is the core identifier. This field is optional.
31123 @subsubheading Example
31128 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31129 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31130 args=[]@},state="running"@},
31131 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31132 frame=@{level="0",addr="0x0804891f",func="foo",
31133 args=[@{name="i",value="10"@}],
31134 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
31135 state="running"@}],
31136 current-thread-id="1"
31140 @subheading The @code{-thread-list-ids} Command
31141 @findex -thread-list-ids
31143 @subsubheading Synopsis
31149 Produces a list of the currently known @value{GDBN} thread ids. At the
31150 end of the list it also prints the total number of such threads.
31152 This command is retained for historical reasons, the
31153 @code{-thread-info} command should be used instead.
31155 @subsubheading @value{GDBN} Command
31157 Part of @samp{info threads} supplies the same information.
31159 @subsubheading Example
31164 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31165 current-thread-id="1",number-of-threads="3"
31170 @subheading The @code{-thread-select} Command
31171 @findex -thread-select
31173 @subsubheading Synopsis
31176 -thread-select @var{threadnum}
31179 Make @var{threadnum} the current thread. It prints the number of the new
31180 current thread, and the topmost frame for that thread.
31182 This command is deprecated in favor of explicitly using the
31183 @samp{--thread} option to each command.
31185 @subsubheading @value{GDBN} Command
31187 The corresponding @value{GDBN} command is @samp{thread}.
31189 @subsubheading Example
31196 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31197 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31201 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31202 number-of-threads="3"
31205 ^done,new-thread-id="3",
31206 frame=@{level="0",func="vprintf",
31207 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31208 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31213 @node GDB/MI Ada Tasking Commands
31214 @section @sc{gdb/mi} Ada Tasking Commands
31216 @subheading The @code{-ada-task-info} Command
31217 @findex -ada-task-info
31219 @subsubheading Synopsis
31222 -ada-task-info [ @var{task-id} ]
31225 Reports information about either a specific Ada task, if the
31226 @var{task-id} parameter is present, or about all Ada tasks.
31228 @subsubheading @value{GDBN} Command
31230 The @samp{info tasks} command prints the same information
31231 about all Ada tasks (@pxref{Ada Tasks}).
31233 @subsubheading Result
31235 The result is a table of Ada tasks. The following columns are
31236 defined for each Ada task:
31240 This field exists only for the current thread. It has the value @samp{*}.
31243 The identifier that @value{GDBN} uses to refer to the Ada task.
31246 The identifier that the target uses to refer to the Ada task.
31249 The identifier of the thread corresponding to the Ada task.
31251 This field should always exist, as Ada tasks are always implemented
31252 on top of a thread. But if @value{GDBN} cannot find this corresponding
31253 thread for any reason, the field is omitted.
31256 This field exists only when the task was created by another task.
31257 In this case, it provides the ID of the parent task.
31260 The base priority of the task.
31263 The current state of the task. For a detailed description of the
31264 possible states, see @ref{Ada Tasks}.
31267 The name of the task.
31271 @subsubheading Example
31275 ^done,tasks=@{nr_rows="3",nr_cols="8",
31276 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31277 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31278 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31279 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31280 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31281 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31282 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31283 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31284 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31285 state="Child Termination Wait",name="main_task"@}]@}
31289 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31290 @node GDB/MI Program Execution
31291 @section @sc{gdb/mi} Program Execution
31293 These are the asynchronous commands which generate the out-of-band
31294 record @samp{*stopped}. Currently @value{GDBN} only really executes
31295 asynchronously with remote targets and this interaction is mimicked in
31298 @subheading The @code{-exec-continue} Command
31299 @findex -exec-continue
31301 @subsubheading Synopsis
31304 -exec-continue [--reverse] [--all|--thread-group N]
31307 Resumes the execution of the inferior program, which will continue
31308 to execute until it reaches a debugger stop event. If the
31309 @samp{--reverse} option is specified, execution resumes in reverse until
31310 it reaches a stop event. Stop events may include
31313 breakpoints or watchpoints
31315 signals or exceptions
31317 the end of the process (or its beginning under @samp{--reverse})
31319 the end or beginning of a replay log if one is being used.
31321 In all-stop mode (@pxref{All-Stop
31322 Mode}), may resume only one thread, or all threads, depending on the
31323 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31324 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31325 ignored in all-stop mode. If the @samp{--thread-group} options is
31326 specified, then all threads in that thread group are resumed.
31328 @subsubheading @value{GDBN} Command
31330 The corresponding @value{GDBN} corresponding is @samp{continue}.
31332 @subsubheading Example
31339 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31340 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31346 @subheading The @code{-exec-finish} Command
31347 @findex -exec-finish
31349 @subsubheading Synopsis
31352 -exec-finish [--reverse]
31355 Resumes the execution of the inferior program until the current
31356 function is exited. Displays the results returned by the function.
31357 If the @samp{--reverse} option is specified, resumes the reverse
31358 execution of the inferior program until the point where current
31359 function was called.
31361 @subsubheading @value{GDBN} Command
31363 The corresponding @value{GDBN} command is @samp{finish}.
31365 @subsubheading Example
31367 Function returning @code{void}.
31374 *stopped,reason="function-finished",frame=@{func="main",args=[],
31375 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31379 Function returning other than @code{void}. The name of the internal
31380 @value{GDBN} variable storing the result is printed, together with the
31387 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31388 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31389 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31390 gdb-result-var="$1",return-value="0"
31395 @subheading The @code{-exec-interrupt} Command
31396 @findex -exec-interrupt
31398 @subsubheading Synopsis
31401 -exec-interrupt [--all|--thread-group N]
31404 Interrupts the background execution of the target. Note how the token
31405 associated with the stop message is the one for the execution command
31406 that has been interrupted. The token for the interrupt itself only
31407 appears in the @samp{^done} output. If the user is trying to
31408 interrupt a non-running program, an error message will be printed.
31410 Note that when asynchronous execution is enabled, this command is
31411 asynchronous just like other execution commands. That is, first the
31412 @samp{^done} response will be printed, and the target stop will be
31413 reported after that using the @samp{*stopped} notification.
31415 In non-stop mode, only the context thread is interrupted by default.
31416 All threads (in all inferiors) will be interrupted if the
31417 @samp{--all} option is specified. If the @samp{--thread-group}
31418 option is specified, all threads in that group will be interrupted.
31420 @subsubheading @value{GDBN} Command
31422 The corresponding @value{GDBN} command is @samp{interrupt}.
31424 @subsubheading Example
31435 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31436 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31437 fullname="/home/foo/bar/try.c",line="13"@}
31442 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31446 @subheading The @code{-exec-jump} Command
31449 @subsubheading Synopsis
31452 -exec-jump @var{location}
31455 Resumes execution of the inferior program at the location specified by
31456 parameter. @xref{Specify Location}, for a description of the
31457 different forms of @var{location}.
31459 @subsubheading @value{GDBN} Command
31461 The corresponding @value{GDBN} command is @samp{jump}.
31463 @subsubheading Example
31466 -exec-jump foo.c:10
31467 *running,thread-id="all"
31472 @subheading The @code{-exec-next} Command
31475 @subsubheading Synopsis
31478 -exec-next [--reverse]
31481 Resumes execution of the inferior program, stopping when the beginning
31482 of the next source line is reached.
31484 If the @samp{--reverse} option is specified, resumes reverse execution
31485 of the inferior program, stopping at the beginning of the previous
31486 source line. If you issue this command on the first line of a
31487 function, it will take you back to the caller of that function, to the
31488 source line where the function was called.
31491 @subsubheading @value{GDBN} Command
31493 The corresponding @value{GDBN} command is @samp{next}.
31495 @subsubheading Example
31501 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31506 @subheading The @code{-exec-next-instruction} Command
31507 @findex -exec-next-instruction
31509 @subsubheading Synopsis
31512 -exec-next-instruction [--reverse]
31515 Executes one machine instruction. If the instruction is a function
31516 call, continues until the function returns. If the program stops at an
31517 instruction in the middle of a source line, the address will be
31520 If the @samp{--reverse} option is specified, resumes reverse execution
31521 of the inferior program, stopping at the previous instruction. If the
31522 previously executed instruction was a return from another function,
31523 it will continue to execute in reverse until the call to that function
31524 (from the current stack frame) is reached.
31526 @subsubheading @value{GDBN} Command
31528 The corresponding @value{GDBN} command is @samp{nexti}.
31530 @subsubheading Example
31534 -exec-next-instruction
31538 *stopped,reason="end-stepping-range",
31539 addr="0x000100d4",line="5",file="hello.c"
31544 @subheading The @code{-exec-return} Command
31545 @findex -exec-return
31547 @subsubheading Synopsis
31553 Makes current function return immediately. Doesn't execute the inferior.
31554 Displays the new current frame.
31556 @subsubheading @value{GDBN} Command
31558 The corresponding @value{GDBN} command is @samp{return}.
31560 @subsubheading Example
31564 200-break-insert callee4
31565 200^done,bkpt=@{number="1",addr="0x00010734",
31566 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31571 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31572 frame=@{func="callee4",args=[],
31573 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31574 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31580 111^done,frame=@{level="0",func="callee3",
31581 args=[@{name="strarg",
31582 value="0x11940 \"A string argument.\""@}],
31583 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31584 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31589 @subheading The @code{-exec-run} Command
31592 @subsubheading Synopsis
31595 -exec-run [ --all | --thread-group N ] [ --start ]
31598 Starts execution of the inferior from the beginning. The inferior
31599 executes until either a breakpoint is encountered or the program
31600 exits. In the latter case the output will include an exit code, if
31601 the program has exited exceptionally.
31603 When neither the @samp{--all} nor the @samp{--thread-group} option
31604 is specified, the current inferior is started. If the
31605 @samp{--thread-group} option is specified, it should refer to a thread
31606 group of type @samp{process}, and that thread group will be started.
31607 If the @samp{--all} option is specified, then all inferiors will be started.
31609 Using the @samp{--start} option instructs the debugger to stop
31610 the execution at the start of the inferior's main subprogram,
31611 following the same behavior as the @code{start} command
31612 (@pxref{Starting}).
31614 @subsubheading @value{GDBN} Command
31616 The corresponding @value{GDBN} command is @samp{run}.
31618 @subsubheading Examples
31623 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31628 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31629 frame=@{func="main",args=[],file="recursive2.c",
31630 fullname="/home/foo/bar/recursive2.c",line="4"@}
31635 Program exited normally:
31643 *stopped,reason="exited-normally"
31648 Program exited exceptionally:
31656 *stopped,reason="exited",exit-code="01"
31660 Another way the program can terminate is if it receives a signal such as
31661 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31665 *stopped,reason="exited-signalled",signal-name="SIGINT",
31666 signal-meaning="Interrupt"
31670 @c @subheading -exec-signal
31673 @subheading The @code{-exec-step} Command
31676 @subsubheading Synopsis
31679 -exec-step [--reverse]
31682 Resumes execution of the inferior program, stopping when the beginning
31683 of the next source line is reached, if the next source line is not a
31684 function call. If it is, stop at the first instruction of the called
31685 function. If the @samp{--reverse} option is specified, resumes reverse
31686 execution of the inferior program, stopping at the beginning of the
31687 previously executed source line.
31689 @subsubheading @value{GDBN} Command
31691 The corresponding @value{GDBN} command is @samp{step}.
31693 @subsubheading Example
31695 Stepping into a function:
31701 *stopped,reason="end-stepping-range",
31702 frame=@{func="foo",args=[@{name="a",value="10"@},
31703 @{name="b",value="0"@}],file="recursive2.c",
31704 fullname="/home/foo/bar/recursive2.c",line="11"@}
31714 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31719 @subheading The @code{-exec-step-instruction} Command
31720 @findex -exec-step-instruction
31722 @subsubheading Synopsis
31725 -exec-step-instruction [--reverse]
31728 Resumes the inferior which executes one machine instruction. If the
31729 @samp{--reverse} option is specified, resumes reverse execution of the
31730 inferior program, stopping at the previously executed instruction.
31731 The output, once @value{GDBN} has stopped, will vary depending on
31732 whether we have stopped in the middle of a source line or not. In the
31733 former case, the address at which the program stopped will be printed
31736 @subsubheading @value{GDBN} Command
31738 The corresponding @value{GDBN} command is @samp{stepi}.
31740 @subsubheading Example
31744 -exec-step-instruction
31748 *stopped,reason="end-stepping-range",
31749 frame=@{func="foo",args=[],file="try.c",
31750 fullname="/home/foo/bar/try.c",line="10"@}
31752 -exec-step-instruction
31756 *stopped,reason="end-stepping-range",
31757 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31758 fullname="/home/foo/bar/try.c",line="10"@}
31763 @subheading The @code{-exec-until} Command
31764 @findex -exec-until
31766 @subsubheading Synopsis
31769 -exec-until [ @var{location} ]
31772 Executes the inferior until the @var{location} specified in the
31773 argument is reached. If there is no argument, the inferior executes
31774 until a source line greater than the current one is reached. The
31775 reason for stopping in this case will be @samp{location-reached}.
31777 @subsubheading @value{GDBN} Command
31779 The corresponding @value{GDBN} command is @samp{until}.
31781 @subsubheading Example
31785 -exec-until recursive2.c:6
31789 *stopped,reason="location-reached",frame=@{func="main",args=[],
31790 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31795 @subheading -file-clear
31796 Is this going away????
31799 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31800 @node GDB/MI Stack Manipulation
31801 @section @sc{gdb/mi} Stack Manipulation Commands
31803 @subheading The @code{-enable-frame-filters} Command
31804 @findex -enable-frame-filters
31807 -enable-frame-filters
31810 @value{GDBN} allows Python-based frame filters to affect the output of
31811 the MI commands relating to stack traces. As there is no way to
31812 implement this in a fully backward-compatible way, a front end must
31813 request that this functionality be enabled.
31815 Once enabled, this feature cannot be disabled.
31817 Note that if Python support has not been compiled into @value{GDBN},
31818 this command will still succeed (and do nothing).
31820 @subheading The @code{-stack-info-frame} Command
31821 @findex -stack-info-frame
31823 @subsubheading Synopsis
31829 Get info on the selected frame.
31831 @subsubheading @value{GDBN} Command
31833 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31834 (without arguments).
31836 @subsubheading Example
31841 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31842 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31843 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31847 @subheading The @code{-stack-info-depth} Command
31848 @findex -stack-info-depth
31850 @subsubheading Synopsis
31853 -stack-info-depth [ @var{max-depth} ]
31856 Return the depth of the stack. If the integer argument @var{max-depth}
31857 is specified, do not count beyond @var{max-depth} frames.
31859 @subsubheading @value{GDBN} Command
31861 There's no equivalent @value{GDBN} command.
31863 @subsubheading Example
31865 For a stack with frame levels 0 through 11:
31872 -stack-info-depth 4
31875 -stack-info-depth 12
31878 -stack-info-depth 11
31881 -stack-info-depth 13
31886 @anchor{-stack-list-arguments}
31887 @subheading The @code{-stack-list-arguments} Command
31888 @findex -stack-list-arguments
31890 @subsubheading Synopsis
31893 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31894 [ @var{low-frame} @var{high-frame} ]
31897 Display a list of the arguments for the frames between @var{low-frame}
31898 and @var{high-frame} (inclusive). If @var{low-frame} and
31899 @var{high-frame} are not provided, list the arguments for the whole
31900 call stack. If the two arguments are equal, show the single frame
31901 at the corresponding level. It is an error if @var{low-frame} is
31902 larger than the actual number of frames. On the other hand,
31903 @var{high-frame} may be larger than the actual number of frames, in
31904 which case only existing frames will be returned.
31906 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31907 the variables; if it is 1 or @code{--all-values}, print also their
31908 values; and if it is 2 or @code{--simple-values}, print the name,
31909 type and value for simple data types, and the name and type for arrays,
31910 structures and unions. If the option @code{--no-frame-filters} is
31911 supplied, then Python frame filters will not be executed.
31913 If the @code{--skip-unavailable} option is specified, arguments that
31914 are not available are not listed. Partially available arguments
31915 are still displayed, however.
31917 Use of this command to obtain arguments in a single frame is
31918 deprecated in favor of the @samp{-stack-list-variables} command.
31920 @subsubheading @value{GDBN} Command
31922 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31923 @samp{gdb_get_args} command which partially overlaps with the
31924 functionality of @samp{-stack-list-arguments}.
31926 @subsubheading Example
31933 frame=@{level="0",addr="0x00010734",func="callee4",
31934 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31935 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31936 frame=@{level="1",addr="0x0001076c",func="callee3",
31937 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31938 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31939 frame=@{level="2",addr="0x0001078c",func="callee2",
31940 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31941 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31942 frame=@{level="3",addr="0x000107b4",func="callee1",
31943 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31944 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31945 frame=@{level="4",addr="0x000107e0",func="main",
31946 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31947 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31949 -stack-list-arguments 0
31952 frame=@{level="0",args=[]@},
31953 frame=@{level="1",args=[name="strarg"]@},
31954 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31955 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31956 frame=@{level="4",args=[]@}]
31958 -stack-list-arguments 1
31961 frame=@{level="0",args=[]@},
31963 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31964 frame=@{level="2",args=[
31965 @{name="intarg",value="2"@},
31966 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31967 @{frame=@{level="3",args=[
31968 @{name="intarg",value="2"@},
31969 @{name="strarg",value="0x11940 \"A string argument.\""@},
31970 @{name="fltarg",value="3.5"@}]@},
31971 frame=@{level="4",args=[]@}]
31973 -stack-list-arguments 0 2 2
31974 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31976 -stack-list-arguments 1 2 2
31977 ^done,stack-args=[frame=@{level="2",
31978 args=[@{name="intarg",value="2"@},
31979 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31983 @c @subheading -stack-list-exception-handlers
31986 @anchor{-stack-list-frames}
31987 @subheading The @code{-stack-list-frames} Command
31988 @findex -stack-list-frames
31990 @subsubheading Synopsis
31993 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31996 List the frames currently on the stack. For each frame it displays the
32001 The frame number, 0 being the topmost frame, i.e., the innermost function.
32003 The @code{$pc} value for that frame.
32007 File name of the source file where the function lives.
32008 @item @var{fullname}
32009 The full file name of the source file where the function lives.
32011 Line number corresponding to the @code{$pc}.
32013 The shared library where this function is defined. This is only given
32014 if the frame's function is not known.
32017 If invoked without arguments, this command prints a backtrace for the
32018 whole stack. If given two integer arguments, it shows the frames whose
32019 levels are between the two arguments (inclusive). If the two arguments
32020 are equal, it shows the single frame at the corresponding level. It is
32021 an error if @var{low-frame} is larger than the actual number of
32022 frames. On the other hand, @var{high-frame} may be larger than the
32023 actual number of frames, in which case only existing frames will be
32024 returned. If the option @code{--no-frame-filters} is supplied, then
32025 Python frame filters will not be executed.
32027 @subsubheading @value{GDBN} Command
32029 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32031 @subsubheading Example
32033 Full stack backtrace:
32039 [frame=@{level="0",addr="0x0001076c",func="foo",
32040 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
32041 frame=@{level="1",addr="0x000107a4",func="foo",
32042 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32043 frame=@{level="2",addr="0x000107a4",func="foo",
32044 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32045 frame=@{level="3",addr="0x000107a4",func="foo",
32046 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32047 frame=@{level="4",addr="0x000107a4",func="foo",
32048 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32049 frame=@{level="5",addr="0x000107a4",func="foo",
32050 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32051 frame=@{level="6",addr="0x000107a4",func="foo",
32052 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32053 frame=@{level="7",addr="0x000107a4",func="foo",
32054 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32055 frame=@{level="8",addr="0x000107a4",func="foo",
32056 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32057 frame=@{level="9",addr="0x000107a4",func="foo",
32058 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32059 frame=@{level="10",addr="0x000107a4",func="foo",
32060 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32061 frame=@{level="11",addr="0x00010738",func="main",
32062 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
32066 Show frames between @var{low_frame} and @var{high_frame}:
32070 -stack-list-frames 3 5
32072 [frame=@{level="3",addr="0x000107a4",func="foo",
32073 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32074 frame=@{level="4",addr="0x000107a4",func="foo",
32075 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32076 frame=@{level="5",addr="0x000107a4",func="foo",
32077 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32081 Show a single frame:
32085 -stack-list-frames 3 3
32087 [frame=@{level="3",addr="0x000107a4",func="foo",
32088 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32093 @subheading The @code{-stack-list-locals} Command
32094 @findex -stack-list-locals
32095 @anchor{-stack-list-locals}
32097 @subsubheading Synopsis
32100 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32103 Display the local variable names for the selected frame. If
32104 @var{print-values} is 0 or @code{--no-values}, print only the names of
32105 the variables; if it is 1 or @code{--all-values}, print also their
32106 values; and if it is 2 or @code{--simple-values}, print the name,
32107 type and value for simple data types, and the name and type for arrays,
32108 structures and unions. In this last case, a frontend can immediately
32109 display the value of simple data types and create variable objects for
32110 other data types when the user wishes to explore their values in
32111 more detail. If the option @code{--no-frame-filters} is supplied, then
32112 Python frame filters will not be executed.
32114 If the @code{--skip-unavailable} option is specified, local variables
32115 that are not available are not listed. Partially available local
32116 variables are still displayed, however.
32118 This command is deprecated in favor of the
32119 @samp{-stack-list-variables} command.
32121 @subsubheading @value{GDBN} Command
32123 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32125 @subsubheading Example
32129 -stack-list-locals 0
32130 ^done,locals=[name="A",name="B",name="C"]
32132 -stack-list-locals --all-values
32133 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32134 @{name="C",value="@{1, 2, 3@}"@}]
32135 -stack-list-locals --simple-values
32136 ^done,locals=[@{name="A",type="int",value="1"@},
32137 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32141 @anchor{-stack-list-variables}
32142 @subheading The @code{-stack-list-variables} Command
32143 @findex -stack-list-variables
32145 @subsubheading Synopsis
32148 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32151 Display the names of local variables and function arguments for the selected frame. If
32152 @var{print-values} is 0 or @code{--no-values}, print only the names of
32153 the variables; if it is 1 or @code{--all-values}, print also their
32154 values; and if it is 2 or @code{--simple-values}, print the name,
32155 type and value for simple data types, and the name and type for arrays,
32156 structures and unions. If the option @code{--no-frame-filters} is
32157 supplied, then Python frame filters will not be executed.
32159 If the @code{--skip-unavailable} option is specified, local variables
32160 and arguments that are not available are not listed. Partially
32161 available arguments and local variables are still displayed, however.
32163 @subsubheading Example
32167 -stack-list-variables --thread 1 --frame 0 --all-values
32168 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32173 @subheading The @code{-stack-select-frame} Command
32174 @findex -stack-select-frame
32176 @subsubheading Synopsis
32179 -stack-select-frame @var{framenum}
32182 Change the selected frame. Select a different frame @var{framenum} on
32185 This command in deprecated in favor of passing the @samp{--frame}
32186 option to every command.
32188 @subsubheading @value{GDBN} Command
32190 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32191 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32193 @subsubheading Example
32197 -stack-select-frame 2
32202 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32203 @node GDB/MI Variable Objects
32204 @section @sc{gdb/mi} Variable Objects
32208 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32210 For the implementation of a variable debugger window (locals, watched
32211 expressions, etc.), we are proposing the adaptation of the existing code
32212 used by @code{Insight}.
32214 The two main reasons for that are:
32218 It has been proven in practice (it is already on its second generation).
32221 It will shorten development time (needless to say how important it is
32225 The original interface was designed to be used by Tcl code, so it was
32226 slightly changed so it could be used through @sc{gdb/mi}. This section
32227 describes the @sc{gdb/mi} operations that will be available and gives some
32228 hints about their use.
32230 @emph{Note}: In addition to the set of operations described here, we
32231 expect the @sc{gui} implementation of a variable window to require, at
32232 least, the following operations:
32235 @item @code{-gdb-show} @code{output-radix}
32236 @item @code{-stack-list-arguments}
32237 @item @code{-stack-list-locals}
32238 @item @code{-stack-select-frame}
32243 @subheading Introduction to Variable Objects
32245 @cindex variable objects in @sc{gdb/mi}
32247 Variable objects are "object-oriented" MI interface for examining and
32248 changing values of expressions. Unlike some other MI interfaces that
32249 work with expressions, variable objects are specifically designed for
32250 simple and efficient presentation in the frontend. A variable object
32251 is identified by string name. When a variable object is created, the
32252 frontend specifies the expression for that variable object. The
32253 expression can be a simple variable, or it can be an arbitrary complex
32254 expression, and can even involve CPU registers. After creating a
32255 variable object, the frontend can invoke other variable object
32256 operations---for example to obtain or change the value of a variable
32257 object, or to change display format.
32259 Variable objects have hierarchical tree structure. Any variable object
32260 that corresponds to a composite type, such as structure in C, has
32261 a number of child variable objects, for example corresponding to each
32262 element of a structure. A child variable object can itself have
32263 children, recursively. Recursion ends when we reach
32264 leaf variable objects, which always have built-in types. Child variable
32265 objects are created only by explicit request, so if a frontend
32266 is not interested in the children of a particular variable object, no
32267 child will be created.
32269 For a leaf variable object it is possible to obtain its value as a
32270 string, or set the value from a string. String value can be also
32271 obtained for a non-leaf variable object, but it's generally a string
32272 that only indicates the type of the object, and does not list its
32273 contents. Assignment to a non-leaf variable object is not allowed.
32275 A frontend does not need to read the values of all variable objects each time
32276 the program stops. Instead, MI provides an update command that lists all
32277 variable objects whose values has changed since the last update
32278 operation. This considerably reduces the amount of data that must
32279 be transferred to the frontend. As noted above, children variable
32280 objects are created on demand, and only leaf variable objects have a
32281 real value. As result, gdb will read target memory only for leaf
32282 variables that frontend has created.
32284 The automatic update is not always desirable. For example, a frontend
32285 might want to keep a value of some expression for future reference,
32286 and never update it. For another example, fetching memory is
32287 relatively slow for embedded targets, so a frontend might want
32288 to disable automatic update for the variables that are either not
32289 visible on the screen, or ``closed''. This is possible using so
32290 called ``frozen variable objects''. Such variable objects are never
32291 implicitly updated.
32293 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32294 fixed variable object, the expression is parsed when the variable
32295 object is created, including associating identifiers to specific
32296 variables. The meaning of expression never changes. For a floating
32297 variable object the values of variables whose names appear in the
32298 expressions are re-evaluated every time in the context of the current
32299 frame. Consider this example:
32304 struct work_state state;
32311 If a fixed variable object for the @code{state} variable is created in
32312 this function, and we enter the recursive call, the variable
32313 object will report the value of @code{state} in the top-level
32314 @code{do_work} invocation. On the other hand, a floating variable
32315 object will report the value of @code{state} in the current frame.
32317 If an expression specified when creating a fixed variable object
32318 refers to a local variable, the variable object becomes bound to the
32319 thread and frame in which the variable object is created. When such
32320 variable object is updated, @value{GDBN} makes sure that the
32321 thread/frame combination the variable object is bound to still exists,
32322 and re-evaluates the variable object in context of that thread/frame.
32324 The following is the complete set of @sc{gdb/mi} operations defined to
32325 access this functionality:
32327 @multitable @columnfractions .4 .6
32328 @item @strong{Operation}
32329 @tab @strong{Description}
32331 @item @code{-enable-pretty-printing}
32332 @tab enable Python-based pretty-printing
32333 @item @code{-var-create}
32334 @tab create a variable object
32335 @item @code{-var-delete}
32336 @tab delete the variable object and/or its children
32337 @item @code{-var-set-format}
32338 @tab set the display format of this variable
32339 @item @code{-var-show-format}
32340 @tab show the display format of this variable
32341 @item @code{-var-info-num-children}
32342 @tab tells how many children this object has
32343 @item @code{-var-list-children}
32344 @tab return a list of the object's children
32345 @item @code{-var-info-type}
32346 @tab show the type of this variable object
32347 @item @code{-var-info-expression}
32348 @tab print parent-relative expression that this variable object represents
32349 @item @code{-var-info-path-expression}
32350 @tab print full expression that this variable object represents
32351 @item @code{-var-show-attributes}
32352 @tab is this variable editable? does it exist here?
32353 @item @code{-var-evaluate-expression}
32354 @tab get the value of this variable
32355 @item @code{-var-assign}
32356 @tab set the value of this variable
32357 @item @code{-var-update}
32358 @tab update the variable and its children
32359 @item @code{-var-set-frozen}
32360 @tab set frozeness attribute
32361 @item @code{-var-set-update-range}
32362 @tab set range of children to display on update
32365 In the next subsection we describe each operation in detail and suggest
32366 how it can be used.
32368 @subheading Description And Use of Operations on Variable Objects
32370 @subheading The @code{-enable-pretty-printing} Command
32371 @findex -enable-pretty-printing
32374 -enable-pretty-printing
32377 @value{GDBN} allows Python-based visualizers to affect the output of the
32378 MI variable object commands. However, because there was no way to
32379 implement this in a fully backward-compatible way, a front end must
32380 request that this functionality be enabled.
32382 Once enabled, this feature cannot be disabled.
32384 Note that if Python support has not been compiled into @value{GDBN},
32385 this command will still succeed (and do nothing).
32387 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32388 may work differently in future versions of @value{GDBN}.
32390 @subheading The @code{-var-create} Command
32391 @findex -var-create
32393 @subsubheading Synopsis
32396 -var-create @{@var{name} | "-"@}
32397 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32400 This operation creates a variable object, which allows the monitoring of
32401 a variable, the result of an expression, a memory cell or a CPU
32404 The @var{name} parameter is the string by which the object can be
32405 referenced. It must be unique. If @samp{-} is specified, the varobj
32406 system will generate a string ``varNNNNNN'' automatically. It will be
32407 unique provided that one does not specify @var{name} of that format.
32408 The command fails if a duplicate name is found.
32410 The frame under which the expression should be evaluated can be
32411 specified by @var{frame-addr}. A @samp{*} indicates that the current
32412 frame should be used. A @samp{@@} indicates that a floating variable
32413 object must be created.
32415 @var{expression} is any expression valid on the current language set (must not
32416 begin with a @samp{*}), or one of the following:
32420 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32423 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32426 @samp{$@var{regname}} --- a CPU register name
32429 @cindex dynamic varobj
32430 A varobj's contents may be provided by a Python-based pretty-printer. In this
32431 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32432 have slightly different semantics in some cases. If the
32433 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32434 will never create a dynamic varobj. This ensures backward
32435 compatibility for existing clients.
32437 @subsubheading Result
32439 This operation returns attributes of the newly-created varobj. These
32444 The name of the varobj.
32447 The number of children of the varobj. This number is not necessarily
32448 reliable for a dynamic varobj. Instead, you must examine the
32449 @samp{has_more} attribute.
32452 The varobj's scalar value. For a varobj whose type is some sort of
32453 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32454 will not be interesting.
32457 The varobj's type. This is a string representation of the type, as
32458 would be printed by the @value{GDBN} CLI. If @samp{print object}
32459 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32460 @emph{actual} (derived) type of the object is shown rather than the
32461 @emph{declared} one.
32464 If a variable object is bound to a specific thread, then this is the
32465 thread's identifier.
32468 For a dynamic varobj, this indicates whether there appear to be any
32469 children available. For a non-dynamic varobj, this will be 0.
32472 This attribute will be present and have the value @samp{1} if the
32473 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32474 then this attribute will not be present.
32477 A dynamic varobj can supply a display hint to the front end. The
32478 value comes directly from the Python pretty-printer object's
32479 @code{display_hint} method. @xref{Pretty Printing API}.
32482 Typical output will look like this:
32485 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32486 has_more="@var{has_more}"
32490 @subheading The @code{-var-delete} Command
32491 @findex -var-delete
32493 @subsubheading Synopsis
32496 -var-delete [ -c ] @var{name}
32499 Deletes a previously created variable object and all of its children.
32500 With the @samp{-c} option, just deletes the children.
32502 Returns an error if the object @var{name} is not found.
32505 @subheading The @code{-var-set-format} Command
32506 @findex -var-set-format
32508 @subsubheading Synopsis
32511 -var-set-format @var{name} @var{format-spec}
32514 Sets the output format for the value of the object @var{name} to be
32517 @anchor{-var-set-format}
32518 The syntax for the @var{format-spec} is as follows:
32521 @var{format-spec} @expansion{}
32522 @{binary | decimal | hexadecimal | octal | natural@}
32525 The natural format is the default format choosen automatically
32526 based on the variable type (like decimal for an @code{int}, hex
32527 for pointers, etc.).
32529 For a variable with children, the format is set only on the
32530 variable itself, and the children are not affected.
32532 @subheading The @code{-var-show-format} Command
32533 @findex -var-show-format
32535 @subsubheading Synopsis
32538 -var-show-format @var{name}
32541 Returns the format used to display the value of the object @var{name}.
32544 @var{format} @expansion{}
32549 @subheading The @code{-var-info-num-children} Command
32550 @findex -var-info-num-children
32552 @subsubheading Synopsis
32555 -var-info-num-children @var{name}
32558 Returns the number of children of a variable object @var{name}:
32564 Note that this number is not completely reliable for a dynamic varobj.
32565 It will return the current number of children, but more children may
32569 @subheading The @code{-var-list-children} Command
32570 @findex -var-list-children
32572 @subsubheading Synopsis
32575 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32577 @anchor{-var-list-children}
32579 Return a list of the children of the specified variable object and
32580 create variable objects for them, if they do not already exist. With
32581 a single argument or if @var{print-values} has a value of 0 or
32582 @code{--no-values}, print only the names of the variables; if
32583 @var{print-values} is 1 or @code{--all-values}, also print their
32584 values; and if it is 2 or @code{--simple-values} print the name and
32585 value for simple data types and just the name for arrays, structures
32588 @var{from} and @var{to}, if specified, indicate the range of children
32589 to report. If @var{from} or @var{to} is less than zero, the range is
32590 reset and all children will be reported. Otherwise, children starting
32591 at @var{from} (zero-based) and up to and excluding @var{to} will be
32594 If a child range is requested, it will only affect the current call to
32595 @code{-var-list-children}, but not future calls to @code{-var-update}.
32596 For this, you must instead use @code{-var-set-update-range}. The
32597 intent of this approach is to enable a front end to implement any
32598 update approach it likes; for example, scrolling a view may cause the
32599 front end to request more children with @code{-var-list-children}, and
32600 then the front end could call @code{-var-set-update-range} with a
32601 different range to ensure that future updates are restricted to just
32604 For each child the following results are returned:
32609 Name of the variable object created for this child.
32612 The expression to be shown to the user by the front end to designate this child.
32613 For example this may be the name of a structure member.
32615 For a dynamic varobj, this value cannot be used to form an
32616 expression. There is no way to do this at all with a dynamic varobj.
32618 For C/C@t{++} structures there are several pseudo children returned to
32619 designate access qualifiers. For these pseudo children @var{exp} is
32620 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32621 type and value are not present.
32623 A dynamic varobj will not report the access qualifying
32624 pseudo-children, regardless of the language. This information is not
32625 available at all with a dynamic varobj.
32628 Number of children this child has. For a dynamic varobj, this will be
32632 The type of the child. If @samp{print object}
32633 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32634 @emph{actual} (derived) type of the object is shown rather than the
32635 @emph{declared} one.
32638 If values were requested, this is the value.
32641 If this variable object is associated with a thread, this is the thread id.
32642 Otherwise this result is not present.
32645 If the variable object is frozen, this variable will be present with a value of 1.
32648 A dynamic varobj can supply a display hint to the front end. The
32649 value comes directly from the Python pretty-printer object's
32650 @code{display_hint} method. @xref{Pretty Printing API}.
32653 This attribute will be present and have the value @samp{1} if the
32654 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32655 then this attribute will not be present.
32659 The result may have its own attributes:
32663 A dynamic varobj can supply a display hint to the front end. The
32664 value comes directly from the Python pretty-printer object's
32665 @code{display_hint} method. @xref{Pretty Printing API}.
32668 This is an integer attribute which is nonzero if there are children
32669 remaining after the end of the selected range.
32672 @subsubheading Example
32676 -var-list-children n
32677 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32678 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32680 -var-list-children --all-values n
32681 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32682 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32686 @subheading The @code{-var-info-type} Command
32687 @findex -var-info-type
32689 @subsubheading Synopsis
32692 -var-info-type @var{name}
32695 Returns the type of the specified variable @var{name}. The type is
32696 returned as a string in the same format as it is output by the
32700 type=@var{typename}
32704 @subheading The @code{-var-info-expression} Command
32705 @findex -var-info-expression
32707 @subsubheading Synopsis
32710 -var-info-expression @var{name}
32713 Returns a string that is suitable for presenting this
32714 variable object in user interface. The string is generally
32715 not valid expression in the current language, and cannot be evaluated.
32717 For example, if @code{a} is an array, and variable object
32718 @code{A} was created for @code{a}, then we'll get this output:
32721 (gdb) -var-info-expression A.1
32722 ^done,lang="C",exp="1"
32726 Here, the value of @code{lang} is the language name, which can be
32727 found in @ref{Supported Languages}.
32729 Note that the output of the @code{-var-list-children} command also
32730 includes those expressions, so the @code{-var-info-expression} command
32733 @subheading The @code{-var-info-path-expression} Command
32734 @findex -var-info-path-expression
32736 @subsubheading Synopsis
32739 -var-info-path-expression @var{name}
32742 Returns an expression that can be evaluated in the current
32743 context and will yield the same value that a variable object has.
32744 Compare this with the @code{-var-info-expression} command, which
32745 result can be used only for UI presentation. Typical use of
32746 the @code{-var-info-path-expression} command is creating a
32747 watchpoint from a variable object.
32749 This command is currently not valid for children of a dynamic varobj,
32750 and will give an error when invoked on one.
32752 For example, suppose @code{C} is a C@t{++} class, derived from class
32753 @code{Base}, and that the @code{Base} class has a member called
32754 @code{m_size}. Assume a variable @code{c} is has the type of
32755 @code{C} and a variable object @code{C} was created for variable
32756 @code{c}. Then, we'll get this output:
32758 (gdb) -var-info-path-expression C.Base.public.m_size
32759 ^done,path_expr=((Base)c).m_size)
32762 @subheading The @code{-var-show-attributes} Command
32763 @findex -var-show-attributes
32765 @subsubheading Synopsis
32768 -var-show-attributes @var{name}
32771 List attributes of the specified variable object @var{name}:
32774 status=@var{attr} [ ( ,@var{attr} )* ]
32778 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32780 @subheading The @code{-var-evaluate-expression} Command
32781 @findex -var-evaluate-expression
32783 @subsubheading Synopsis
32786 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32789 Evaluates the expression that is represented by the specified variable
32790 object and returns its value as a string. The format of the string
32791 can be specified with the @samp{-f} option. The possible values of
32792 this option are the same as for @code{-var-set-format}
32793 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32794 the current display format will be used. The current display format
32795 can be changed using the @code{-var-set-format} command.
32801 Note that one must invoke @code{-var-list-children} for a variable
32802 before the value of a child variable can be evaluated.
32804 @subheading The @code{-var-assign} Command
32805 @findex -var-assign
32807 @subsubheading Synopsis
32810 -var-assign @var{name} @var{expression}
32813 Assigns the value of @var{expression} to the variable object specified
32814 by @var{name}. The object must be @samp{editable}. If the variable's
32815 value is altered by the assign, the variable will show up in any
32816 subsequent @code{-var-update} list.
32818 @subsubheading Example
32826 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32830 @subheading The @code{-var-update} Command
32831 @findex -var-update
32833 @subsubheading Synopsis
32836 -var-update [@var{print-values}] @{@var{name} | "*"@}
32839 Reevaluate the expressions corresponding to the variable object
32840 @var{name} and all its direct and indirect children, and return the
32841 list of variable objects whose values have changed; @var{name} must
32842 be a root variable object. Here, ``changed'' means that the result of
32843 @code{-var-evaluate-expression} before and after the
32844 @code{-var-update} is different. If @samp{*} is used as the variable
32845 object names, all existing variable objects are updated, except
32846 for frozen ones (@pxref{-var-set-frozen}). The option
32847 @var{print-values} determines whether both names and values, or just
32848 names are printed. The possible values of this option are the same
32849 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32850 recommended to use the @samp{--all-values} option, to reduce the
32851 number of MI commands needed on each program stop.
32853 With the @samp{*} parameter, if a variable object is bound to a
32854 currently running thread, it will not be updated, without any
32857 If @code{-var-set-update-range} was previously used on a varobj, then
32858 only the selected range of children will be reported.
32860 @code{-var-update} reports all the changed varobjs in a tuple named
32863 Each item in the change list is itself a tuple holding:
32867 The name of the varobj.
32870 If values were requested for this update, then this field will be
32871 present and will hold the value of the varobj.
32874 @anchor{-var-update}
32875 This field is a string which may take one of three values:
32879 The variable object's current value is valid.
32882 The variable object does not currently hold a valid value but it may
32883 hold one in the future if its associated expression comes back into
32887 The variable object no longer holds a valid value.
32888 This can occur when the executable file being debugged has changed,
32889 either through recompilation or by using the @value{GDBN} @code{file}
32890 command. The front end should normally choose to delete these variable
32894 In the future new values may be added to this list so the front should
32895 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32898 This is only present if the varobj is still valid. If the type
32899 changed, then this will be the string @samp{true}; otherwise it will
32902 When a varobj's type changes, its children are also likely to have
32903 become incorrect. Therefore, the varobj's children are automatically
32904 deleted when this attribute is @samp{true}. Also, the varobj's update
32905 range, when set using the @code{-var-set-update-range} command, is
32909 If the varobj's type changed, then this field will be present and will
32912 @item new_num_children
32913 For a dynamic varobj, if the number of children changed, or if the
32914 type changed, this will be the new number of children.
32916 The @samp{numchild} field in other varobj responses is generally not
32917 valid for a dynamic varobj -- it will show the number of children that
32918 @value{GDBN} knows about, but because dynamic varobjs lazily
32919 instantiate their children, this will not reflect the number of
32920 children which may be available.
32922 The @samp{new_num_children} attribute only reports changes to the
32923 number of children known by @value{GDBN}. This is the only way to
32924 detect whether an update has removed children (which necessarily can
32925 only happen at the end of the update range).
32928 The display hint, if any.
32931 This is an integer value, which will be 1 if there are more children
32932 available outside the varobj's update range.
32935 This attribute will be present and have the value @samp{1} if the
32936 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32937 then this attribute will not be present.
32940 If new children were added to a dynamic varobj within the selected
32941 update range (as set by @code{-var-set-update-range}), then they will
32942 be listed in this attribute.
32945 @subsubheading Example
32952 -var-update --all-values var1
32953 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32954 type_changed="false"@}]
32958 @subheading The @code{-var-set-frozen} Command
32959 @findex -var-set-frozen
32960 @anchor{-var-set-frozen}
32962 @subsubheading Synopsis
32965 -var-set-frozen @var{name} @var{flag}
32968 Set the frozenness flag on the variable object @var{name}. The
32969 @var{flag} parameter should be either @samp{1} to make the variable
32970 frozen or @samp{0} to make it unfrozen. If a variable object is
32971 frozen, then neither itself, nor any of its children, are
32972 implicitly updated by @code{-var-update} of
32973 a parent variable or by @code{-var-update *}. Only
32974 @code{-var-update} of the variable itself will update its value and
32975 values of its children. After a variable object is unfrozen, it is
32976 implicitly updated by all subsequent @code{-var-update} operations.
32977 Unfreezing a variable does not update it, only subsequent
32978 @code{-var-update} does.
32980 @subsubheading Example
32984 -var-set-frozen V 1
32989 @subheading The @code{-var-set-update-range} command
32990 @findex -var-set-update-range
32991 @anchor{-var-set-update-range}
32993 @subsubheading Synopsis
32996 -var-set-update-range @var{name} @var{from} @var{to}
32999 Set the range of children to be returned by future invocations of
33000 @code{-var-update}.
33002 @var{from} and @var{to} indicate the range of children to report. If
33003 @var{from} or @var{to} is less than zero, the range is reset and all
33004 children will be reported. Otherwise, children starting at @var{from}
33005 (zero-based) and up to and excluding @var{to} will be reported.
33007 @subsubheading Example
33011 -var-set-update-range V 1 2
33015 @subheading The @code{-var-set-visualizer} command
33016 @findex -var-set-visualizer
33017 @anchor{-var-set-visualizer}
33019 @subsubheading Synopsis
33022 -var-set-visualizer @var{name} @var{visualizer}
33025 Set a visualizer for the variable object @var{name}.
33027 @var{visualizer} is the visualizer to use. The special value
33028 @samp{None} means to disable any visualizer in use.
33030 If not @samp{None}, @var{visualizer} must be a Python expression.
33031 This expression must evaluate to a callable object which accepts a
33032 single argument. @value{GDBN} will call this object with the value of
33033 the varobj @var{name} as an argument (this is done so that the same
33034 Python pretty-printing code can be used for both the CLI and MI).
33035 When called, this object must return an object which conforms to the
33036 pretty-printing interface (@pxref{Pretty Printing API}).
33038 The pre-defined function @code{gdb.default_visualizer} may be used to
33039 select a visualizer by following the built-in process
33040 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33041 a varobj is created, and so ordinarily is not needed.
33043 This feature is only available if Python support is enabled. The MI
33044 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33045 can be used to check this.
33047 @subsubheading Example
33049 Resetting the visualizer:
33053 -var-set-visualizer V None
33057 Reselecting the default (type-based) visualizer:
33061 -var-set-visualizer V gdb.default_visualizer
33065 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33066 can be used to instantiate this class for a varobj:
33070 -var-set-visualizer V "lambda val: SomeClass()"
33074 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33075 @node GDB/MI Data Manipulation
33076 @section @sc{gdb/mi} Data Manipulation
33078 @cindex data manipulation, in @sc{gdb/mi}
33079 @cindex @sc{gdb/mi}, data manipulation
33080 This section describes the @sc{gdb/mi} commands that manipulate data:
33081 examine memory and registers, evaluate expressions, etc.
33083 @c REMOVED FROM THE INTERFACE.
33084 @c @subheading -data-assign
33085 @c Change the value of a program variable. Plenty of side effects.
33086 @c @subsubheading GDB Command
33088 @c @subsubheading Example
33091 @subheading The @code{-data-disassemble} Command
33092 @findex -data-disassemble
33094 @subsubheading Synopsis
33098 [ -s @var{start-addr} -e @var{end-addr} ]
33099 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33107 @item @var{start-addr}
33108 is the beginning address (or @code{$pc})
33109 @item @var{end-addr}
33111 @item @var{filename}
33112 is the name of the file to disassemble
33113 @item @var{linenum}
33114 is the line number to disassemble around
33116 is the number of disassembly lines to be produced. If it is -1,
33117 the whole function will be disassembled, in case no @var{end-addr} is
33118 specified. If @var{end-addr} is specified as a non-zero value, and
33119 @var{lines} is lower than the number of disassembly lines between
33120 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33121 displayed; if @var{lines} is higher than the number of lines between
33122 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33125 is either 0 (meaning only disassembly), 1 (meaning mixed source and
33126 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
33127 mixed source and disassembly with raw opcodes).
33130 @subsubheading Result
33132 The result of the @code{-data-disassemble} command will be a list named
33133 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33134 used with the @code{-data-disassemble} command.
33136 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33141 The address at which this instruction was disassembled.
33144 The name of the function this instruction is within.
33147 The decimal offset in bytes from the start of @samp{func-name}.
33150 The text disassembly for this @samp{address}.
33153 This field is only present for mode 2. This contains the raw opcode
33154 bytes for the @samp{inst} field.
33158 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33159 @samp{src_and_asm_line}, each of which has the following fields:
33163 The line number within @samp{file}.
33166 The file name from the compilation unit. This might be an absolute
33167 file name or a relative file name depending on the compile command
33171 Absolute file name of @samp{file}. It is converted to a canonical form
33172 using the source file search path
33173 (@pxref{Source Path, ,Specifying Source Directories})
33174 and after resolving all the symbolic links.
33176 If the source file is not found this field will contain the path as
33177 present in the debug information.
33179 @item line_asm_insn
33180 This is a list of tuples containing the disassembly for @samp{line} in
33181 @samp{file}. The fields of each tuple are the same as for
33182 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33183 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33188 Note that whatever included in the @samp{inst} field, is not
33189 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33192 @subsubheading @value{GDBN} Command
33194 The corresponding @value{GDBN} command is @samp{disassemble}.
33196 @subsubheading Example
33198 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33202 -data-disassemble -s $pc -e "$pc + 20" -- 0
33205 @{address="0x000107c0",func-name="main",offset="4",
33206 inst="mov 2, %o0"@},
33207 @{address="0x000107c4",func-name="main",offset="8",
33208 inst="sethi %hi(0x11800), %o2"@},
33209 @{address="0x000107c8",func-name="main",offset="12",
33210 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33211 @{address="0x000107cc",func-name="main",offset="16",
33212 inst="sethi %hi(0x11800), %o2"@},
33213 @{address="0x000107d0",func-name="main",offset="20",
33214 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33218 Disassemble the whole @code{main} function. Line 32 is part of
33222 -data-disassemble -f basics.c -l 32 -- 0
33224 @{address="0x000107bc",func-name="main",offset="0",
33225 inst="save %sp, -112, %sp"@},
33226 @{address="0x000107c0",func-name="main",offset="4",
33227 inst="mov 2, %o0"@},
33228 @{address="0x000107c4",func-name="main",offset="8",
33229 inst="sethi %hi(0x11800), %o2"@},
33231 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33232 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33236 Disassemble 3 instructions from the start of @code{main}:
33240 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33242 @{address="0x000107bc",func-name="main",offset="0",
33243 inst="save %sp, -112, %sp"@},
33244 @{address="0x000107c0",func-name="main",offset="4",
33245 inst="mov 2, %o0"@},
33246 @{address="0x000107c4",func-name="main",offset="8",
33247 inst="sethi %hi(0x11800), %o2"@}]
33251 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33255 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33257 src_and_asm_line=@{line="31",
33258 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33259 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33260 line_asm_insn=[@{address="0x000107bc",
33261 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33262 src_and_asm_line=@{line="32",
33263 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33264 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33265 line_asm_insn=[@{address="0x000107c0",
33266 func-name="main",offset="4",inst="mov 2, %o0"@},
33267 @{address="0x000107c4",func-name="main",offset="8",
33268 inst="sethi %hi(0x11800), %o2"@}]@}]
33273 @subheading The @code{-data-evaluate-expression} Command
33274 @findex -data-evaluate-expression
33276 @subsubheading Synopsis
33279 -data-evaluate-expression @var{expr}
33282 Evaluate @var{expr} as an expression. The expression could contain an
33283 inferior function call. The function call will execute synchronously.
33284 If the expression contains spaces, it must be enclosed in double quotes.
33286 @subsubheading @value{GDBN} Command
33288 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33289 @samp{call}. In @code{gdbtk} only, there's a corresponding
33290 @samp{gdb_eval} command.
33292 @subsubheading Example
33294 In the following example, the numbers that precede the commands are the
33295 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33296 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33300 211-data-evaluate-expression A
33303 311-data-evaluate-expression &A
33304 311^done,value="0xefffeb7c"
33306 411-data-evaluate-expression A+3
33309 511-data-evaluate-expression "A + 3"
33315 @subheading The @code{-data-list-changed-registers} Command
33316 @findex -data-list-changed-registers
33318 @subsubheading Synopsis
33321 -data-list-changed-registers
33324 Display a list of the registers that have changed.
33326 @subsubheading @value{GDBN} Command
33328 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33329 has the corresponding command @samp{gdb_changed_register_list}.
33331 @subsubheading Example
33333 On a PPC MBX board:
33341 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33342 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33345 -data-list-changed-registers
33346 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33347 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33348 "24","25","26","27","28","30","31","64","65","66","67","69"]
33353 @subheading The @code{-data-list-register-names} Command
33354 @findex -data-list-register-names
33356 @subsubheading Synopsis
33359 -data-list-register-names [ ( @var{regno} )+ ]
33362 Show a list of register names for the current target. If no arguments
33363 are given, it shows a list of the names of all the registers. If
33364 integer numbers are given as arguments, it will print a list of the
33365 names of the registers corresponding to the arguments. To ensure
33366 consistency between a register name and its number, the output list may
33367 include empty register names.
33369 @subsubheading @value{GDBN} Command
33371 @value{GDBN} does not have a command which corresponds to
33372 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33373 corresponding command @samp{gdb_regnames}.
33375 @subsubheading Example
33377 For the PPC MBX board:
33380 -data-list-register-names
33381 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33382 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33383 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33384 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33385 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33386 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33387 "", "pc","ps","cr","lr","ctr","xer"]
33389 -data-list-register-names 1 2 3
33390 ^done,register-names=["r1","r2","r3"]
33394 @subheading The @code{-data-list-register-values} Command
33395 @findex -data-list-register-values
33397 @subsubheading Synopsis
33400 -data-list-register-values
33401 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33404 Display the registers' contents. @var{fmt} is the format according to
33405 which the registers' contents are to be returned, followed by an optional
33406 list of numbers specifying the registers to display. A missing list of
33407 numbers indicates that the contents of all the registers must be
33408 returned. The @code{--skip-unavailable} option indicates that only
33409 the available registers are to be returned.
33411 Allowed formats for @var{fmt} are:
33428 @subsubheading @value{GDBN} Command
33430 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33431 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33433 @subsubheading Example
33435 For a PPC MBX board (note: line breaks are for readability only, they
33436 don't appear in the actual output):
33440 -data-list-register-values r 64 65
33441 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33442 @{number="65",value="0x00029002"@}]
33444 -data-list-register-values x
33445 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33446 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33447 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33448 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33449 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33450 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33451 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33452 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33453 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33454 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33455 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33456 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33457 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33458 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33459 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33460 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33461 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33462 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33463 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33464 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33465 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33466 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33467 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33468 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33469 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33470 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33471 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33472 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33473 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33474 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33475 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33476 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33477 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33478 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33479 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33480 @{number="69",value="0x20002b03"@}]
33485 @subheading The @code{-data-read-memory} Command
33486 @findex -data-read-memory
33488 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33490 @subsubheading Synopsis
33493 -data-read-memory [ -o @var{byte-offset} ]
33494 @var{address} @var{word-format} @var{word-size}
33495 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33502 @item @var{address}
33503 An expression specifying the address of the first memory word to be
33504 read. Complex expressions containing embedded white space should be
33505 quoted using the C convention.
33507 @item @var{word-format}
33508 The format to be used to print the memory words. The notation is the
33509 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33512 @item @var{word-size}
33513 The size of each memory word in bytes.
33515 @item @var{nr-rows}
33516 The number of rows in the output table.
33518 @item @var{nr-cols}
33519 The number of columns in the output table.
33522 If present, indicates that each row should include an @sc{ascii} dump. The
33523 value of @var{aschar} is used as a padding character when a byte is not a
33524 member of the printable @sc{ascii} character set (printable @sc{ascii}
33525 characters are those whose code is between 32 and 126, inclusively).
33527 @item @var{byte-offset}
33528 An offset to add to the @var{address} before fetching memory.
33531 This command displays memory contents as a table of @var{nr-rows} by
33532 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33533 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33534 (returned as @samp{total-bytes}). Should less than the requested number
33535 of bytes be returned by the target, the missing words are identified
33536 using @samp{N/A}. The number of bytes read from the target is returned
33537 in @samp{nr-bytes} and the starting address used to read memory in
33540 The address of the next/previous row or page is available in
33541 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33544 @subsubheading @value{GDBN} Command
33546 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33547 @samp{gdb_get_mem} memory read command.
33549 @subsubheading Example
33551 Read six bytes of memory starting at @code{bytes+6} but then offset by
33552 @code{-6} bytes. Format as three rows of two columns. One byte per
33553 word. Display each word in hex.
33557 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33558 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33559 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33560 prev-page="0x0000138a",memory=[
33561 @{addr="0x00001390",data=["0x00","0x01"]@},
33562 @{addr="0x00001392",data=["0x02","0x03"]@},
33563 @{addr="0x00001394",data=["0x04","0x05"]@}]
33567 Read two bytes of memory starting at address @code{shorts + 64} and
33568 display as a single word formatted in decimal.
33572 5-data-read-memory shorts+64 d 2 1 1
33573 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33574 next-row="0x00001512",prev-row="0x0000150e",
33575 next-page="0x00001512",prev-page="0x0000150e",memory=[
33576 @{addr="0x00001510",data=["128"]@}]
33580 Read thirty two bytes of memory starting at @code{bytes+16} and format
33581 as eight rows of four columns. Include a string encoding with @samp{x}
33582 used as the non-printable character.
33586 4-data-read-memory bytes+16 x 1 8 4 x
33587 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33588 next-row="0x000013c0",prev-row="0x0000139c",
33589 next-page="0x000013c0",prev-page="0x00001380",memory=[
33590 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33591 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33592 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33593 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33594 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33595 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33596 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33597 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33601 @subheading The @code{-data-read-memory-bytes} Command
33602 @findex -data-read-memory-bytes
33604 @subsubheading Synopsis
33607 -data-read-memory-bytes [ -o @var{byte-offset} ]
33608 @var{address} @var{count}
33615 @item @var{address}
33616 An expression specifying the address of the first memory word to be
33617 read. Complex expressions containing embedded white space should be
33618 quoted using the C convention.
33621 The number of bytes to read. This should be an integer literal.
33623 @item @var{byte-offset}
33624 The offsets in bytes relative to @var{address} at which to start
33625 reading. This should be an integer literal. This option is provided
33626 so that a frontend is not required to first evaluate address and then
33627 perform address arithmetics itself.
33631 This command attempts to read all accessible memory regions in the
33632 specified range. First, all regions marked as unreadable in the memory
33633 map (if one is defined) will be skipped. @xref{Memory Region
33634 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33635 regions. For each one, if reading full region results in an errors,
33636 @value{GDBN} will try to read a subset of the region.
33638 In general, every single byte in the region may be readable or not,
33639 and the only way to read every readable byte is to try a read at
33640 every address, which is not practical. Therefore, @value{GDBN} will
33641 attempt to read all accessible bytes at either beginning or the end
33642 of the region, using a binary division scheme. This heuristic works
33643 well for reading accross a memory map boundary. Note that if a region
33644 has a readable range that is neither at the beginning or the end,
33645 @value{GDBN} will not read it.
33647 The result record (@pxref{GDB/MI Result Records}) that is output of
33648 the command includes a field named @samp{memory} whose content is a
33649 list of tuples. Each tuple represent a successfully read memory block
33650 and has the following fields:
33654 The start address of the memory block, as hexadecimal literal.
33657 The end address of the memory block, as hexadecimal literal.
33660 The offset of the memory block, as hexadecimal literal, relative to
33661 the start address passed to @code{-data-read-memory-bytes}.
33664 The contents of the memory block, in hex.
33670 @subsubheading @value{GDBN} Command
33672 The corresponding @value{GDBN} command is @samp{x}.
33674 @subsubheading Example
33678 -data-read-memory-bytes &a 10
33679 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33681 contents="01000000020000000300"@}]
33686 @subheading The @code{-data-write-memory-bytes} Command
33687 @findex -data-write-memory-bytes
33689 @subsubheading Synopsis
33692 -data-write-memory-bytes @var{address} @var{contents}
33693 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33700 @item @var{address}
33701 An expression specifying the address of the first memory word to be
33702 read. Complex expressions containing embedded white space should be
33703 quoted using the C convention.
33705 @item @var{contents}
33706 The hex-encoded bytes to write.
33709 Optional argument indicating the number of bytes to be written. If @var{count}
33710 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33711 write @var{contents} until it fills @var{count} bytes.
33715 @subsubheading @value{GDBN} Command
33717 There's no corresponding @value{GDBN} command.
33719 @subsubheading Example
33723 -data-write-memory-bytes &a "aabbccdd"
33730 -data-write-memory-bytes &a "aabbccdd" 16e
33735 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33736 @node GDB/MI Tracepoint Commands
33737 @section @sc{gdb/mi} Tracepoint Commands
33739 The commands defined in this section implement MI support for
33740 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33742 @subheading The @code{-trace-find} Command
33743 @findex -trace-find
33745 @subsubheading Synopsis
33748 -trace-find @var{mode} [@var{parameters}@dots{}]
33751 Find a trace frame using criteria defined by @var{mode} and
33752 @var{parameters}. The following table lists permissible
33753 modes and their parameters. For details of operation, see @ref{tfind}.
33758 No parameters are required. Stops examining trace frames.
33761 An integer is required as parameter. Selects tracepoint frame with
33764 @item tracepoint-number
33765 An integer is required as parameter. Finds next
33766 trace frame that corresponds to tracepoint with the specified number.
33769 An address is required as parameter. Finds
33770 next trace frame that corresponds to any tracepoint at the specified
33773 @item pc-inside-range
33774 Two addresses are required as parameters. Finds next trace
33775 frame that corresponds to a tracepoint at an address inside the
33776 specified range. Both bounds are considered to be inside the range.
33778 @item pc-outside-range
33779 Two addresses are required as parameters. Finds
33780 next trace frame that corresponds to a tracepoint at an address outside
33781 the specified range. Both bounds are considered to be inside the range.
33784 Line specification is required as parameter. @xref{Specify Location}.
33785 Finds next trace frame that corresponds to a tracepoint at
33786 the specified location.
33790 If @samp{none} was passed as @var{mode}, the response does not
33791 have fields. Otherwise, the response may have the following fields:
33795 This field has either @samp{0} or @samp{1} as the value, depending
33796 on whether a matching tracepoint was found.
33799 The index of the found traceframe. This field is present iff
33800 the @samp{found} field has value of @samp{1}.
33803 The index of the found tracepoint. This field is present iff
33804 the @samp{found} field has value of @samp{1}.
33807 The information about the frame corresponding to the found trace
33808 frame. This field is present only if a trace frame was found.
33809 @xref{GDB/MI Frame Information}, for description of this field.
33813 @subsubheading @value{GDBN} Command
33815 The corresponding @value{GDBN} command is @samp{tfind}.
33817 @subheading -trace-define-variable
33818 @findex -trace-define-variable
33820 @subsubheading Synopsis
33823 -trace-define-variable @var{name} [ @var{value} ]
33826 Create trace variable @var{name} if it does not exist. If
33827 @var{value} is specified, sets the initial value of the specified
33828 trace variable to that value. Note that the @var{name} should start
33829 with the @samp{$} character.
33831 @subsubheading @value{GDBN} Command
33833 The corresponding @value{GDBN} command is @samp{tvariable}.
33835 @subheading The @code{-trace-frame-collected} Command
33836 @findex -trace-frame-collected
33838 @subsubheading Synopsis
33841 -trace-frame-collected
33842 [--var-print-values @var{var_pval}]
33843 [--comp-print-values @var{comp_pval}]
33844 [--registers-format @var{regformat}]
33845 [--memory-contents]
33848 This command returns the set of collected objects, register names,
33849 trace state variable names, memory ranges and computed expressions
33850 that have been collected at a particular trace frame. The optional
33851 parameters to the command affect the output format in different ways.
33852 See the output description table below for more details.
33854 The reported names can be used in the normal manner to create
33855 varobjs and inspect the objects themselves. The items returned by
33856 this command are categorized so that it is clear which is a variable,
33857 which is a register, which is a trace state variable, which is a
33858 memory range and which is a computed expression.
33860 For instance, if the actions were
33862 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33863 collect *(int*)0xaf02bef0@@40
33867 the object collected in its entirety would be @code{myVar}. The
33868 object @code{myArray} would be partially collected, because only the
33869 element at index @code{myIndex} would be collected. The remaining
33870 objects would be computed expressions.
33872 An example output would be:
33876 -trace-frame-collected
33878 explicit-variables=[@{name="myVar",value="1"@}],
33879 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33880 @{name="myObj.field",value="0"@},
33881 @{name="myPtr->field",value="1"@},
33882 @{name="myCount + 2",value="3"@},
33883 @{name="$tvar1 + 1",value="43970027"@}],
33884 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33885 @{number="1",value="0x0"@},
33886 @{number="2",value="0x4"@},
33888 @{number="125",value="0x0"@}],
33889 tvars=[@{name="$tvar1",current="43970026"@}],
33890 memory=[@{address="0x0000000000602264",length="4"@},
33891 @{address="0x0000000000615bc0",length="4"@}]
33898 @item explicit-variables
33899 The set of objects that have been collected in their entirety (as
33900 opposed to collecting just a few elements of an array or a few struct
33901 members). For each object, its name and value are printed.
33902 The @code{--var-print-values} option affects how or whether the value
33903 field is output. If @var{var_pval} is 0, then print only the names;
33904 if it is 1, print also their values; and if it is 2, print the name,
33905 type and value for simple data types, and the name and type for
33906 arrays, structures and unions.
33908 @item computed-expressions
33909 The set of computed expressions that have been collected at the
33910 current trace frame. The @code{--comp-print-values} option affects
33911 this set like the @code{--var-print-values} option affects the
33912 @code{explicit-variables} set. See above.
33915 The registers that have been collected at the current trace frame.
33916 For each register collected, the name and current value are returned.
33917 The value is formatted according to the @code{--registers-format}
33918 option. See the @command{-data-list-register-values} command for a
33919 list of the allowed formats. The default is @samp{x}.
33922 The trace state variables that have been collected at the current
33923 trace frame. For each trace state variable collected, the name and
33924 current value are returned.
33927 The set of memory ranges that have been collected at the current trace
33928 frame. Its content is a list of tuples. Each tuple represents a
33929 collected memory range and has the following fields:
33933 The start address of the memory range, as hexadecimal literal.
33936 The length of the memory range, as decimal literal.
33939 The contents of the memory block, in hex. This field is only present
33940 if the @code{--memory-contents} option is specified.
33946 @subsubheading @value{GDBN} Command
33948 There is no corresponding @value{GDBN} command.
33950 @subsubheading Example
33952 @subheading -trace-list-variables
33953 @findex -trace-list-variables
33955 @subsubheading Synopsis
33958 -trace-list-variables
33961 Return a table of all defined trace variables. Each element of the
33962 table has the following fields:
33966 The name of the trace variable. This field is always present.
33969 The initial value. This is a 64-bit signed integer. This
33970 field is always present.
33973 The value the trace variable has at the moment. This is a 64-bit
33974 signed integer. This field is absent iff current value is
33975 not defined, for example if the trace was never run, or is
33980 @subsubheading @value{GDBN} Command
33982 The corresponding @value{GDBN} command is @samp{tvariables}.
33984 @subsubheading Example
33988 -trace-list-variables
33989 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33990 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33991 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33992 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33993 body=[variable=@{name="$trace_timestamp",initial="0"@}
33994 variable=@{name="$foo",initial="10",current="15"@}]@}
33998 @subheading -trace-save
33999 @findex -trace-save
34001 @subsubheading Synopsis
34004 -trace-save [-r ] @var{filename}
34007 Saves the collected trace data to @var{filename}. Without the
34008 @samp{-r} option, the data is downloaded from the target and saved
34009 in a local file. With the @samp{-r} option the target is asked
34010 to perform the save.
34012 @subsubheading @value{GDBN} Command
34014 The corresponding @value{GDBN} command is @samp{tsave}.
34017 @subheading -trace-start
34018 @findex -trace-start
34020 @subsubheading Synopsis
34026 Starts a tracing experiments. The result of this command does not
34029 @subsubheading @value{GDBN} Command
34031 The corresponding @value{GDBN} command is @samp{tstart}.
34033 @subheading -trace-status
34034 @findex -trace-status
34036 @subsubheading Synopsis
34042 Obtains the status of a tracing experiment. The result may include
34043 the following fields:
34048 May have a value of either @samp{0}, when no tracing operations are
34049 supported, @samp{1}, when all tracing operations are supported, or
34050 @samp{file} when examining trace file. In the latter case, examining
34051 of trace frame is possible but new tracing experiement cannot be
34052 started. This field is always present.
34055 May have a value of either @samp{0} or @samp{1} depending on whether
34056 tracing experiement is in progress on target. This field is present
34057 if @samp{supported} field is not @samp{0}.
34060 Report the reason why the tracing was stopped last time. This field
34061 may be absent iff tracing was never stopped on target yet. The
34062 value of @samp{request} means the tracing was stopped as result of
34063 the @code{-trace-stop} command. The value of @samp{overflow} means
34064 the tracing buffer is full. The value of @samp{disconnection} means
34065 tracing was automatically stopped when @value{GDBN} has disconnected.
34066 The value of @samp{passcount} means tracing was stopped when a
34067 tracepoint was passed a maximal number of times for that tracepoint.
34068 This field is present if @samp{supported} field is not @samp{0}.
34070 @item stopping-tracepoint
34071 The number of tracepoint whose passcount as exceeded. This field is
34072 present iff the @samp{stop-reason} field has the value of
34076 @itemx frames-created
34077 The @samp{frames} field is a count of the total number of trace frames
34078 in the trace buffer, while @samp{frames-created} is the total created
34079 during the run, including ones that were discarded, such as when a
34080 circular trace buffer filled up. Both fields are optional.
34084 These fields tell the current size of the tracing buffer and the
34085 remaining space. These fields are optional.
34088 The value of the circular trace buffer flag. @code{1} means that the
34089 trace buffer is circular and old trace frames will be discarded if
34090 necessary to make room, @code{0} means that the trace buffer is linear
34094 The value of the disconnected tracing flag. @code{1} means that
34095 tracing will continue after @value{GDBN} disconnects, @code{0} means
34096 that the trace run will stop.
34099 The filename of the trace file being examined. This field is
34100 optional, and only present when examining a trace file.
34104 @subsubheading @value{GDBN} Command
34106 The corresponding @value{GDBN} command is @samp{tstatus}.
34108 @subheading -trace-stop
34109 @findex -trace-stop
34111 @subsubheading Synopsis
34117 Stops a tracing experiment. The result of this command has the same
34118 fields as @code{-trace-status}, except that the @samp{supported} and
34119 @samp{running} fields are not output.
34121 @subsubheading @value{GDBN} Command
34123 The corresponding @value{GDBN} command is @samp{tstop}.
34126 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34127 @node GDB/MI Symbol Query
34128 @section @sc{gdb/mi} Symbol Query Commands
34132 @subheading The @code{-symbol-info-address} Command
34133 @findex -symbol-info-address
34135 @subsubheading Synopsis
34138 -symbol-info-address @var{symbol}
34141 Describe where @var{symbol} is stored.
34143 @subsubheading @value{GDBN} Command
34145 The corresponding @value{GDBN} command is @samp{info address}.
34147 @subsubheading Example
34151 @subheading The @code{-symbol-info-file} Command
34152 @findex -symbol-info-file
34154 @subsubheading Synopsis
34160 Show the file for the symbol.
34162 @subsubheading @value{GDBN} Command
34164 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34165 @samp{gdb_find_file}.
34167 @subsubheading Example
34171 @subheading The @code{-symbol-info-function} Command
34172 @findex -symbol-info-function
34174 @subsubheading Synopsis
34177 -symbol-info-function
34180 Show which function the symbol lives in.
34182 @subsubheading @value{GDBN} Command
34184 @samp{gdb_get_function} in @code{gdbtk}.
34186 @subsubheading Example
34190 @subheading The @code{-symbol-info-line} Command
34191 @findex -symbol-info-line
34193 @subsubheading Synopsis
34199 Show the core addresses of the code for a source line.
34201 @subsubheading @value{GDBN} Command
34203 The corresponding @value{GDBN} command is @samp{info line}.
34204 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34206 @subsubheading Example
34210 @subheading The @code{-symbol-info-symbol} Command
34211 @findex -symbol-info-symbol
34213 @subsubheading Synopsis
34216 -symbol-info-symbol @var{addr}
34219 Describe what symbol is at location @var{addr}.
34221 @subsubheading @value{GDBN} Command
34223 The corresponding @value{GDBN} command is @samp{info symbol}.
34225 @subsubheading Example
34229 @subheading The @code{-symbol-list-functions} Command
34230 @findex -symbol-list-functions
34232 @subsubheading Synopsis
34235 -symbol-list-functions
34238 List the functions in the executable.
34240 @subsubheading @value{GDBN} Command
34242 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34243 @samp{gdb_search} in @code{gdbtk}.
34245 @subsubheading Example
34250 @subheading The @code{-symbol-list-lines} Command
34251 @findex -symbol-list-lines
34253 @subsubheading Synopsis
34256 -symbol-list-lines @var{filename}
34259 Print the list of lines that contain code and their associated program
34260 addresses for the given source filename. The entries are sorted in
34261 ascending PC order.
34263 @subsubheading @value{GDBN} Command
34265 There is no corresponding @value{GDBN} command.
34267 @subsubheading Example
34270 -symbol-list-lines basics.c
34271 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34277 @subheading The @code{-symbol-list-types} Command
34278 @findex -symbol-list-types
34280 @subsubheading Synopsis
34286 List all the type names.
34288 @subsubheading @value{GDBN} Command
34290 The corresponding commands are @samp{info types} in @value{GDBN},
34291 @samp{gdb_search} in @code{gdbtk}.
34293 @subsubheading Example
34297 @subheading The @code{-symbol-list-variables} Command
34298 @findex -symbol-list-variables
34300 @subsubheading Synopsis
34303 -symbol-list-variables
34306 List all the global and static variable names.
34308 @subsubheading @value{GDBN} Command
34310 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34312 @subsubheading Example
34316 @subheading The @code{-symbol-locate} Command
34317 @findex -symbol-locate
34319 @subsubheading Synopsis
34325 @subsubheading @value{GDBN} Command
34327 @samp{gdb_loc} in @code{gdbtk}.
34329 @subsubheading Example
34333 @subheading The @code{-symbol-type} Command
34334 @findex -symbol-type
34336 @subsubheading Synopsis
34339 -symbol-type @var{variable}
34342 Show type of @var{variable}.
34344 @subsubheading @value{GDBN} Command
34346 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34347 @samp{gdb_obj_variable}.
34349 @subsubheading Example
34354 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34355 @node GDB/MI File Commands
34356 @section @sc{gdb/mi} File Commands
34358 This section describes the GDB/MI commands to specify executable file names
34359 and to read in and obtain symbol table information.
34361 @subheading The @code{-file-exec-and-symbols} Command
34362 @findex -file-exec-and-symbols
34364 @subsubheading Synopsis
34367 -file-exec-and-symbols @var{file}
34370 Specify the executable file to be debugged. This file is the one from
34371 which the symbol table is also read. If no file is specified, the
34372 command clears the executable and symbol information. If breakpoints
34373 are set when using this command with no arguments, @value{GDBN} will produce
34374 error messages. Otherwise, no output is produced, except a completion
34377 @subsubheading @value{GDBN} Command
34379 The corresponding @value{GDBN} command is @samp{file}.
34381 @subsubheading Example
34385 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34391 @subheading The @code{-file-exec-file} Command
34392 @findex -file-exec-file
34394 @subsubheading Synopsis
34397 -file-exec-file @var{file}
34400 Specify the executable file to be debugged. Unlike
34401 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34402 from this file. If used without argument, @value{GDBN} clears the information
34403 about the executable file. No output is produced, except a completion
34406 @subsubheading @value{GDBN} Command
34408 The corresponding @value{GDBN} command is @samp{exec-file}.
34410 @subsubheading Example
34414 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34421 @subheading The @code{-file-list-exec-sections} Command
34422 @findex -file-list-exec-sections
34424 @subsubheading Synopsis
34427 -file-list-exec-sections
34430 List the sections of the current executable file.
34432 @subsubheading @value{GDBN} Command
34434 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34435 information as this command. @code{gdbtk} has a corresponding command
34436 @samp{gdb_load_info}.
34438 @subsubheading Example
34443 @subheading The @code{-file-list-exec-source-file} Command
34444 @findex -file-list-exec-source-file
34446 @subsubheading Synopsis
34449 -file-list-exec-source-file
34452 List the line number, the current source file, and the absolute path
34453 to the current source file for the current executable. The macro
34454 information field has a value of @samp{1} or @samp{0} depending on
34455 whether or not the file includes preprocessor macro information.
34457 @subsubheading @value{GDBN} Command
34459 The @value{GDBN} equivalent is @samp{info source}
34461 @subsubheading Example
34465 123-file-list-exec-source-file
34466 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34471 @subheading The @code{-file-list-exec-source-files} Command
34472 @findex -file-list-exec-source-files
34474 @subsubheading Synopsis
34477 -file-list-exec-source-files
34480 List the source files for the current executable.
34482 It will always output both the filename and fullname (absolute file
34483 name) of a source file.
34485 @subsubheading @value{GDBN} Command
34487 The @value{GDBN} equivalent is @samp{info sources}.
34488 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34490 @subsubheading Example
34493 -file-list-exec-source-files
34495 @{file=foo.c,fullname=/home/foo.c@},
34496 @{file=/home/bar.c,fullname=/home/bar.c@},
34497 @{file=gdb_could_not_find_fullpath.c@}]
34502 @subheading The @code{-file-list-shared-libraries} Command
34503 @findex -file-list-shared-libraries
34505 @subsubheading Synopsis
34508 -file-list-shared-libraries
34511 List the shared libraries in the program.
34513 @subsubheading @value{GDBN} Command
34515 The corresponding @value{GDBN} command is @samp{info shared}.
34517 @subsubheading Example
34521 @subheading The @code{-file-list-symbol-files} Command
34522 @findex -file-list-symbol-files
34524 @subsubheading Synopsis
34527 -file-list-symbol-files
34532 @subsubheading @value{GDBN} Command
34534 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34536 @subsubheading Example
34541 @subheading The @code{-file-symbol-file} Command
34542 @findex -file-symbol-file
34544 @subsubheading Synopsis
34547 -file-symbol-file @var{file}
34550 Read symbol table info from the specified @var{file} argument. When
34551 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34552 produced, except for a completion notification.
34554 @subsubheading @value{GDBN} Command
34556 The corresponding @value{GDBN} command is @samp{symbol-file}.
34558 @subsubheading Example
34562 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34568 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34569 @node GDB/MI Memory Overlay Commands
34570 @section @sc{gdb/mi} Memory Overlay Commands
34572 The memory overlay commands are not implemented.
34574 @c @subheading -overlay-auto
34576 @c @subheading -overlay-list-mapping-state
34578 @c @subheading -overlay-list-overlays
34580 @c @subheading -overlay-map
34582 @c @subheading -overlay-off
34584 @c @subheading -overlay-on
34586 @c @subheading -overlay-unmap
34588 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34589 @node GDB/MI Signal Handling Commands
34590 @section @sc{gdb/mi} Signal Handling Commands
34592 Signal handling commands are not implemented.
34594 @c @subheading -signal-handle
34596 @c @subheading -signal-list-handle-actions
34598 @c @subheading -signal-list-signal-types
34602 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34603 @node GDB/MI Target Manipulation
34604 @section @sc{gdb/mi} Target Manipulation Commands
34607 @subheading The @code{-target-attach} Command
34608 @findex -target-attach
34610 @subsubheading Synopsis
34613 -target-attach @var{pid} | @var{gid} | @var{file}
34616 Attach to a process @var{pid} or a file @var{file} outside of
34617 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34618 group, the id previously returned by
34619 @samp{-list-thread-groups --available} must be used.
34621 @subsubheading @value{GDBN} Command
34623 The corresponding @value{GDBN} command is @samp{attach}.
34625 @subsubheading Example
34629 =thread-created,id="1"
34630 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34636 @subheading The @code{-target-compare-sections} Command
34637 @findex -target-compare-sections
34639 @subsubheading Synopsis
34642 -target-compare-sections [ @var{section} ]
34645 Compare data of section @var{section} on target to the exec file.
34646 Without the argument, all sections are compared.
34648 @subsubheading @value{GDBN} Command
34650 The @value{GDBN} equivalent is @samp{compare-sections}.
34652 @subsubheading Example
34657 @subheading The @code{-target-detach} Command
34658 @findex -target-detach
34660 @subsubheading Synopsis
34663 -target-detach [ @var{pid} | @var{gid} ]
34666 Detach from the remote target which normally resumes its execution.
34667 If either @var{pid} or @var{gid} is specified, detaches from either
34668 the specified process, or specified thread group. There's no output.
34670 @subsubheading @value{GDBN} Command
34672 The corresponding @value{GDBN} command is @samp{detach}.
34674 @subsubheading Example
34684 @subheading The @code{-target-disconnect} Command
34685 @findex -target-disconnect
34687 @subsubheading Synopsis
34693 Disconnect from the remote target. There's no output and the target is
34694 generally not resumed.
34696 @subsubheading @value{GDBN} Command
34698 The corresponding @value{GDBN} command is @samp{disconnect}.
34700 @subsubheading Example
34710 @subheading The @code{-target-download} Command
34711 @findex -target-download
34713 @subsubheading Synopsis
34719 Loads the executable onto the remote target.
34720 It prints out an update message every half second, which includes the fields:
34724 The name of the section.
34726 The size of what has been sent so far for that section.
34728 The size of the section.
34730 The total size of what was sent so far (the current and the previous sections).
34732 The size of the overall executable to download.
34736 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34737 @sc{gdb/mi} Output Syntax}).
34739 In addition, it prints the name and size of the sections, as they are
34740 downloaded. These messages include the following fields:
34744 The name of the section.
34746 The size of the section.
34748 The size of the overall executable to download.
34752 At the end, a summary is printed.
34754 @subsubheading @value{GDBN} Command
34756 The corresponding @value{GDBN} command is @samp{load}.
34758 @subsubheading Example
34760 Note: each status message appears on a single line. Here the messages
34761 have been broken down so that they can fit onto a page.
34766 +download,@{section=".text",section-size="6668",total-size="9880"@}
34767 +download,@{section=".text",section-sent="512",section-size="6668",
34768 total-sent="512",total-size="9880"@}
34769 +download,@{section=".text",section-sent="1024",section-size="6668",
34770 total-sent="1024",total-size="9880"@}
34771 +download,@{section=".text",section-sent="1536",section-size="6668",
34772 total-sent="1536",total-size="9880"@}
34773 +download,@{section=".text",section-sent="2048",section-size="6668",
34774 total-sent="2048",total-size="9880"@}
34775 +download,@{section=".text",section-sent="2560",section-size="6668",
34776 total-sent="2560",total-size="9880"@}
34777 +download,@{section=".text",section-sent="3072",section-size="6668",
34778 total-sent="3072",total-size="9880"@}
34779 +download,@{section=".text",section-sent="3584",section-size="6668",
34780 total-sent="3584",total-size="9880"@}
34781 +download,@{section=".text",section-sent="4096",section-size="6668",
34782 total-sent="4096",total-size="9880"@}
34783 +download,@{section=".text",section-sent="4608",section-size="6668",
34784 total-sent="4608",total-size="9880"@}
34785 +download,@{section=".text",section-sent="5120",section-size="6668",
34786 total-sent="5120",total-size="9880"@}
34787 +download,@{section=".text",section-sent="5632",section-size="6668",
34788 total-sent="5632",total-size="9880"@}
34789 +download,@{section=".text",section-sent="6144",section-size="6668",
34790 total-sent="6144",total-size="9880"@}
34791 +download,@{section=".text",section-sent="6656",section-size="6668",
34792 total-sent="6656",total-size="9880"@}
34793 +download,@{section=".init",section-size="28",total-size="9880"@}
34794 +download,@{section=".fini",section-size="28",total-size="9880"@}
34795 +download,@{section=".data",section-size="3156",total-size="9880"@}
34796 +download,@{section=".data",section-sent="512",section-size="3156",
34797 total-sent="7236",total-size="9880"@}
34798 +download,@{section=".data",section-sent="1024",section-size="3156",
34799 total-sent="7748",total-size="9880"@}
34800 +download,@{section=".data",section-sent="1536",section-size="3156",
34801 total-sent="8260",total-size="9880"@}
34802 +download,@{section=".data",section-sent="2048",section-size="3156",
34803 total-sent="8772",total-size="9880"@}
34804 +download,@{section=".data",section-sent="2560",section-size="3156",
34805 total-sent="9284",total-size="9880"@}
34806 +download,@{section=".data",section-sent="3072",section-size="3156",
34807 total-sent="9796",total-size="9880"@}
34808 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34815 @subheading The @code{-target-exec-status} Command
34816 @findex -target-exec-status
34818 @subsubheading Synopsis
34821 -target-exec-status
34824 Provide information on the state of the target (whether it is running or
34825 not, for instance).
34827 @subsubheading @value{GDBN} Command
34829 There's no equivalent @value{GDBN} command.
34831 @subsubheading Example
34835 @subheading The @code{-target-list-available-targets} Command
34836 @findex -target-list-available-targets
34838 @subsubheading Synopsis
34841 -target-list-available-targets
34844 List the possible targets to connect to.
34846 @subsubheading @value{GDBN} Command
34848 The corresponding @value{GDBN} command is @samp{help target}.
34850 @subsubheading Example
34854 @subheading The @code{-target-list-current-targets} Command
34855 @findex -target-list-current-targets
34857 @subsubheading Synopsis
34860 -target-list-current-targets
34863 Describe the current target.
34865 @subsubheading @value{GDBN} Command
34867 The corresponding information is printed by @samp{info file} (among
34870 @subsubheading Example
34874 @subheading The @code{-target-list-parameters} Command
34875 @findex -target-list-parameters
34877 @subsubheading Synopsis
34880 -target-list-parameters
34886 @subsubheading @value{GDBN} Command
34890 @subsubheading Example
34894 @subheading The @code{-target-select} Command
34895 @findex -target-select
34897 @subsubheading Synopsis
34900 -target-select @var{type} @var{parameters @dots{}}
34903 Connect @value{GDBN} to the remote target. This command takes two args:
34907 The type of target, for instance @samp{remote}, etc.
34908 @item @var{parameters}
34909 Device names, host names and the like. @xref{Target Commands, ,
34910 Commands for Managing Targets}, for more details.
34913 The output is a connection notification, followed by the address at
34914 which the target program is, in the following form:
34917 ^connected,addr="@var{address}",func="@var{function name}",
34918 args=[@var{arg list}]
34921 @subsubheading @value{GDBN} Command
34923 The corresponding @value{GDBN} command is @samp{target}.
34925 @subsubheading Example
34929 -target-select remote /dev/ttya
34930 ^connected,addr="0xfe00a300",func="??",args=[]
34934 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34935 @node GDB/MI File Transfer Commands
34936 @section @sc{gdb/mi} File Transfer Commands
34939 @subheading The @code{-target-file-put} Command
34940 @findex -target-file-put
34942 @subsubheading Synopsis
34945 -target-file-put @var{hostfile} @var{targetfile}
34948 Copy file @var{hostfile} from the host system (the machine running
34949 @value{GDBN}) to @var{targetfile} on the target system.
34951 @subsubheading @value{GDBN} Command
34953 The corresponding @value{GDBN} command is @samp{remote put}.
34955 @subsubheading Example
34959 -target-file-put localfile remotefile
34965 @subheading The @code{-target-file-get} Command
34966 @findex -target-file-get
34968 @subsubheading Synopsis
34971 -target-file-get @var{targetfile} @var{hostfile}
34974 Copy file @var{targetfile} from the target system to @var{hostfile}
34975 on the host system.
34977 @subsubheading @value{GDBN} Command
34979 The corresponding @value{GDBN} command is @samp{remote get}.
34981 @subsubheading Example
34985 -target-file-get remotefile localfile
34991 @subheading The @code{-target-file-delete} Command
34992 @findex -target-file-delete
34994 @subsubheading Synopsis
34997 -target-file-delete @var{targetfile}
35000 Delete @var{targetfile} from the target system.
35002 @subsubheading @value{GDBN} Command
35004 The corresponding @value{GDBN} command is @samp{remote delete}.
35006 @subsubheading Example
35010 -target-file-delete remotefile
35016 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35017 @node GDB/MI Ada Exceptions Commands
35018 @section Ada Exceptions @sc{gdb/mi} Commands
35020 @subheading The @code{-info-ada-exceptions} Command
35021 @findex -info-ada-exceptions
35023 @subsubheading Synopsis
35026 -info-ada-exceptions [ @var{regexp}]
35029 List all Ada exceptions defined within the program being debugged.
35030 With a regular expression @var{regexp}, only those exceptions whose
35031 names match @var{regexp} are listed.
35033 @subsubheading @value{GDBN} Command
35035 The corresponding @value{GDBN} command is @samp{info exceptions}.
35037 @subsubheading Result
35039 The result is a table of Ada exceptions. The following columns are
35040 defined for each exception:
35044 The name of the exception.
35047 The address of the exception.
35051 @subsubheading Example
35054 -info-ada-exceptions aint
35055 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
35056 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
35057 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
35058 body=[@{name="constraint_error",address="0x0000000000613da0"@},
35059 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
35062 @subheading Catching Ada Exceptions
35064 The commands describing how to ask @value{GDBN} to stop when a program
35065 raises an exception are described at @ref{Ada Exception GDB/MI
35066 Catchpoint Commands}.
35069 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35070 @node GDB/MI Support Commands
35071 @section @sc{gdb/mi} Support Commands
35073 Since new commands and features get regularly added to @sc{gdb/mi},
35074 some commands are available to help front-ends query the debugger
35075 about support for these capabilities. Similarly, it is also possible
35076 to query @value{GDBN} about target support of certain features.
35078 @subheading The @code{-info-gdb-mi-command} Command
35079 @cindex @code{-info-gdb-mi-command}
35080 @findex -info-gdb-mi-command
35082 @subsubheading Synopsis
35085 -info-gdb-mi-command @var{cmd_name}
35088 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35090 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35091 is technically not part of the command name (@pxref{GDB/MI Input
35092 Syntax}), and thus should be omitted in @var{cmd_name}. However,
35093 for ease of use, this command also accepts the form with the leading
35096 @subsubheading @value{GDBN} Command
35098 There is no corresponding @value{GDBN} command.
35100 @subsubheading Result
35102 The result is a tuple. There is currently only one field:
35106 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
35107 @code{"false"} otherwise.
35111 @subsubheading Example
35113 Here is an example where the @sc{gdb/mi} command does not exist:
35116 -info-gdb-mi-command unsupported-command
35117 ^done,command=@{exists="false"@}
35121 And here is an example where the @sc{gdb/mi} command is known
35125 -info-gdb-mi-command symbol-list-lines
35126 ^done,command=@{exists="true"@}
35129 @subheading The @code{-list-features} Command
35130 @findex -list-features
35131 @cindex supported @sc{gdb/mi} features, list
35133 Returns a list of particular features of the MI protocol that
35134 this version of gdb implements. A feature can be a command,
35135 or a new field in an output of some command, or even an
35136 important bugfix. While a frontend can sometimes detect presence
35137 of a feature at runtime, it is easier to perform detection at debugger
35140 The command returns a list of strings, with each string naming an
35141 available feature. Each returned string is just a name, it does not
35142 have any internal structure. The list of possible feature names
35148 (gdb) -list-features
35149 ^done,result=["feature1","feature2"]
35152 The current list of features is:
35155 @item frozen-varobjs
35156 Indicates support for the @code{-var-set-frozen} command, as well
35157 as possible presense of the @code{frozen} field in the output
35158 of @code{-varobj-create}.
35159 @item pending-breakpoints
35160 Indicates support for the @option{-f} option to the @code{-break-insert}
35163 Indicates Python scripting support, Python-based
35164 pretty-printing commands, and possible presence of the
35165 @samp{display_hint} field in the output of @code{-var-list-children}
35167 Indicates support for the @code{-thread-info} command.
35168 @item data-read-memory-bytes
35169 Indicates support for the @code{-data-read-memory-bytes} and the
35170 @code{-data-write-memory-bytes} commands.
35171 @item breakpoint-notifications
35172 Indicates that changes to breakpoints and breakpoints created via the
35173 CLI will be announced via async records.
35174 @item ada-task-info
35175 Indicates support for the @code{-ada-task-info} command.
35176 @item language-option
35177 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35178 option (@pxref{Context management}).
35179 @item info-gdb-mi-command
35180 Indicates support for the @code{-info-gdb-mi-command} command.
35181 @item undefined-command-error-code
35182 Indicates support for the "undefined-command" error code in error result
35183 records, produced when trying to execute an undefined @sc{gdb/mi} command
35184 (@pxref{GDB/MI Result Records}).
35185 @item exec-run-start-option
35186 Indicates that the @code{-exec-run} command supports the @option{--start}
35187 option (@pxref{GDB/MI Program Execution}).
35190 @subheading The @code{-list-target-features} Command
35191 @findex -list-target-features
35193 Returns a list of particular features that are supported by the
35194 target. Those features affect the permitted MI commands, but
35195 unlike the features reported by the @code{-list-features} command, the
35196 features depend on which target GDB is using at the moment. Whenever
35197 a target can change, due to commands such as @code{-target-select},
35198 @code{-target-attach} or @code{-exec-run}, the list of target features
35199 may change, and the frontend should obtain it again.
35203 (gdb) -list-target-features
35204 ^done,result=["async"]
35207 The current list of features is:
35211 Indicates that the target is capable of asynchronous command
35212 execution, which means that @value{GDBN} will accept further commands
35213 while the target is running.
35216 Indicates that the target is capable of reverse execution.
35217 @xref{Reverse Execution}, for more information.
35221 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35222 @node GDB/MI Miscellaneous Commands
35223 @section Miscellaneous @sc{gdb/mi} Commands
35225 @c @subheading -gdb-complete
35227 @subheading The @code{-gdb-exit} Command
35230 @subsubheading Synopsis
35236 Exit @value{GDBN} immediately.
35238 @subsubheading @value{GDBN} Command
35240 Approximately corresponds to @samp{quit}.
35242 @subsubheading Example
35252 @subheading The @code{-exec-abort} Command
35253 @findex -exec-abort
35255 @subsubheading Synopsis
35261 Kill the inferior running program.
35263 @subsubheading @value{GDBN} Command
35265 The corresponding @value{GDBN} command is @samp{kill}.
35267 @subsubheading Example
35272 @subheading The @code{-gdb-set} Command
35275 @subsubheading Synopsis
35281 Set an internal @value{GDBN} variable.
35282 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35284 @subsubheading @value{GDBN} Command
35286 The corresponding @value{GDBN} command is @samp{set}.
35288 @subsubheading Example
35298 @subheading The @code{-gdb-show} Command
35301 @subsubheading Synopsis
35307 Show the current value of a @value{GDBN} variable.
35309 @subsubheading @value{GDBN} Command
35311 The corresponding @value{GDBN} command is @samp{show}.
35313 @subsubheading Example
35322 @c @subheading -gdb-source
35325 @subheading The @code{-gdb-version} Command
35326 @findex -gdb-version
35328 @subsubheading Synopsis
35334 Show version information for @value{GDBN}. Used mostly in testing.
35336 @subsubheading @value{GDBN} Command
35338 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35339 default shows this information when you start an interactive session.
35341 @subsubheading Example
35343 @c This example modifies the actual output from GDB to avoid overfull
35349 ~Copyright 2000 Free Software Foundation, Inc.
35350 ~GDB is free software, covered by the GNU General Public License, and
35351 ~you are welcome to change it and/or distribute copies of it under
35352 ~ certain conditions.
35353 ~Type "show copying" to see the conditions.
35354 ~There is absolutely no warranty for GDB. Type "show warranty" for
35356 ~This GDB was configured as
35357 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35362 @subheading The @code{-list-thread-groups} Command
35363 @findex -list-thread-groups
35365 @subheading Synopsis
35368 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35371 Lists thread groups (@pxref{Thread groups}). When a single thread
35372 group is passed as the argument, lists the children of that group.
35373 When several thread group are passed, lists information about those
35374 thread groups. Without any parameters, lists information about all
35375 top-level thread groups.
35377 Normally, thread groups that are being debugged are reported.
35378 With the @samp{--available} option, @value{GDBN} reports thread groups
35379 available on the target.
35381 The output of this command may have either a @samp{threads} result or
35382 a @samp{groups} result. The @samp{thread} result has a list of tuples
35383 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35384 Information}). The @samp{groups} result has a list of tuples as value,
35385 each tuple describing a thread group. If top-level groups are
35386 requested (that is, no parameter is passed), or when several groups
35387 are passed, the output always has a @samp{groups} result. The format
35388 of the @samp{group} result is described below.
35390 To reduce the number of roundtrips it's possible to list thread groups
35391 together with their children, by passing the @samp{--recurse} option
35392 and the recursion depth. Presently, only recursion depth of 1 is
35393 permitted. If this option is present, then every reported thread group
35394 will also include its children, either as @samp{group} or
35395 @samp{threads} field.
35397 In general, any combination of option and parameters is permitted, with
35398 the following caveats:
35402 When a single thread group is passed, the output will typically
35403 be the @samp{threads} result. Because threads may not contain
35404 anything, the @samp{recurse} option will be ignored.
35407 When the @samp{--available} option is passed, limited information may
35408 be available. In particular, the list of threads of a process might
35409 be inaccessible. Further, specifying specific thread groups might
35410 not give any performance advantage over listing all thread groups.
35411 The frontend should assume that @samp{-list-thread-groups --available}
35412 is always an expensive operation and cache the results.
35416 The @samp{groups} result is a list of tuples, where each tuple may
35417 have the following fields:
35421 Identifier of the thread group. This field is always present.
35422 The identifier is an opaque string; frontends should not try to
35423 convert it to an integer, even though it might look like one.
35426 The type of the thread group. At present, only @samp{process} is a
35430 The target-specific process identifier. This field is only present
35431 for thread groups of type @samp{process} and only if the process exists.
35434 The number of children this thread group has. This field may be
35435 absent for an available thread group.
35438 This field has a list of tuples as value, each tuple describing a
35439 thread. It may be present if the @samp{--recurse} option is
35440 specified, and it's actually possible to obtain the threads.
35443 This field is a list of integers, each identifying a core that one
35444 thread of the group is running on. This field may be absent if
35445 such information is not available.
35448 The name of the executable file that corresponds to this thread group.
35449 The field is only present for thread groups of type @samp{process},
35450 and only if there is a corresponding executable file.
35454 @subheading Example
35458 -list-thread-groups
35459 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35460 -list-thread-groups 17
35461 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35462 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35463 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35464 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35465 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35466 -list-thread-groups --available
35467 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35468 -list-thread-groups --available --recurse 1
35469 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35470 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35471 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35472 -list-thread-groups --available --recurse 1 17 18
35473 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35474 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35475 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35478 @subheading The @code{-info-os} Command
35481 @subsubheading Synopsis
35484 -info-os [ @var{type} ]
35487 If no argument is supplied, the command returns a table of available
35488 operating-system-specific information types. If one of these types is
35489 supplied as an argument @var{type}, then the command returns a table
35490 of data of that type.
35492 The types of information available depend on the target operating
35495 @subsubheading @value{GDBN} Command
35497 The corresponding @value{GDBN} command is @samp{info os}.
35499 @subsubheading Example
35501 When run on a @sc{gnu}/Linux system, the output will look something
35507 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35508 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35509 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35510 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35511 body=[item=@{col0="processes",col1="Listing of all processes",
35512 col2="Processes"@},
35513 item=@{col0="procgroups",col1="Listing of all process groups",
35514 col2="Process groups"@},
35515 item=@{col0="threads",col1="Listing of all threads",
35517 item=@{col0="files",col1="Listing of all file descriptors",
35518 col2="File descriptors"@},
35519 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35521 item=@{col0="shm",col1="Listing of all shared-memory regions",
35522 col2="Shared-memory regions"@},
35523 item=@{col0="semaphores",col1="Listing of all semaphores",
35524 col2="Semaphores"@},
35525 item=@{col0="msg",col1="Listing of all message queues",
35526 col2="Message queues"@},
35527 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35528 col2="Kernel modules"@}]@}
35531 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35532 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35533 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35534 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35535 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35536 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35537 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35538 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35540 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35541 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35545 (Note that the MI output here includes a @code{"Title"} column that
35546 does not appear in command-line @code{info os}; this column is useful
35547 for MI clients that want to enumerate the types of data, such as in a
35548 popup menu, but is needless clutter on the command line, and
35549 @code{info os} omits it.)
35551 @subheading The @code{-add-inferior} Command
35552 @findex -add-inferior
35554 @subheading Synopsis
35560 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35561 inferior is not associated with any executable. Such association may
35562 be established with the @samp{-file-exec-and-symbols} command
35563 (@pxref{GDB/MI File Commands}). The command response has a single
35564 field, @samp{inferior}, whose value is the identifier of the
35565 thread group corresponding to the new inferior.
35567 @subheading Example
35572 ^done,inferior="i3"
35575 @subheading The @code{-interpreter-exec} Command
35576 @findex -interpreter-exec
35578 @subheading Synopsis
35581 -interpreter-exec @var{interpreter} @var{command}
35583 @anchor{-interpreter-exec}
35585 Execute the specified @var{command} in the given @var{interpreter}.
35587 @subheading @value{GDBN} Command
35589 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35591 @subheading Example
35595 -interpreter-exec console "break main"
35596 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35597 &"During symbol reading, bad structure-type format.\n"
35598 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35603 @subheading The @code{-inferior-tty-set} Command
35604 @findex -inferior-tty-set
35606 @subheading Synopsis
35609 -inferior-tty-set /dev/pts/1
35612 Set terminal for future runs of the program being debugged.
35614 @subheading @value{GDBN} Command
35616 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35618 @subheading Example
35622 -inferior-tty-set /dev/pts/1
35627 @subheading The @code{-inferior-tty-show} Command
35628 @findex -inferior-tty-show
35630 @subheading Synopsis
35636 Show terminal for future runs of program being debugged.
35638 @subheading @value{GDBN} Command
35640 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35642 @subheading Example
35646 -inferior-tty-set /dev/pts/1
35650 ^done,inferior_tty_terminal="/dev/pts/1"
35654 @subheading The @code{-enable-timings} Command
35655 @findex -enable-timings
35657 @subheading Synopsis
35660 -enable-timings [yes | no]
35663 Toggle the printing of the wallclock, user and system times for an MI
35664 command as a field in its output. This command is to help frontend
35665 developers optimize the performance of their code. No argument is
35666 equivalent to @samp{yes}.
35668 @subheading @value{GDBN} Command
35672 @subheading Example
35680 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35681 addr="0x080484ed",func="main",file="myprog.c",
35682 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35684 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35692 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35693 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35694 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35695 fullname="/home/nickrob/myprog.c",line="73"@}
35700 @chapter @value{GDBN} Annotations
35702 This chapter describes annotations in @value{GDBN}. Annotations were
35703 designed to interface @value{GDBN} to graphical user interfaces or other
35704 similar programs which want to interact with @value{GDBN} at a
35705 relatively high level.
35707 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35711 This is Edition @value{EDITION}, @value{DATE}.
35715 * Annotations Overview:: What annotations are; the general syntax.
35716 * Server Prefix:: Issuing a command without affecting user state.
35717 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35718 * Errors:: Annotations for error messages.
35719 * Invalidation:: Some annotations describe things now invalid.
35720 * Annotations for Running::
35721 Whether the program is running, how it stopped, etc.
35722 * Source Annotations:: Annotations describing source code.
35725 @node Annotations Overview
35726 @section What is an Annotation?
35727 @cindex annotations
35729 Annotations start with a newline character, two @samp{control-z}
35730 characters, and the name of the annotation. If there is no additional
35731 information associated with this annotation, the name of the annotation
35732 is followed immediately by a newline. If there is additional
35733 information, the name of the annotation is followed by a space, the
35734 additional information, and a newline. The additional information
35735 cannot contain newline characters.
35737 Any output not beginning with a newline and two @samp{control-z}
35738 characters denotes literal output from @value{GDBN}. Currently there is
35739 no need for @value{GDBN} to output a newline followed by two
35740 @samp{control-z} characters, but if there was such a need, the
35741 annotations could be extended with an @samp{escape} annotation which
35742 means those three characters as output.
35744 The annotation @var{level}, which is specified using the
35745 @option{--annotate} command line option (@pxref{Mode Options}), controls
35746 how much information @value{GDBN} prints together with its prompt,
35747 values of expressions, source lines, and other types of output. Level 0
35748 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35749 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35750 for programs that control @value{GDBN}, and level 2 annotations have
35751 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35752 Interface, annotate, GDB's Obsolete Annotations}).
35755 @kindex set annotate
35756 @item set annotate @var{level}
35757 The @value{GDBN} command @code{set annotate} sets the level of
35758 annotations to the specified @var{level}.
35760 @item show annotate
35761 @kindex show annotate
35762 Show the current annotation level.
35765 This chapter describes level 3 annotations.
35767 A simple example of starting up @value{GDBN} with annotations is:
35770 $ @kbd{gdb --annotate=3}
35772 Copyright 2003 Free Software Foundation, Inc.
35773 GDB is free software, covered by the GNU General Public License,
35774 and you are welcome to change it and/or distribute copies of it
35775 under certain conditions.
35776 Type "show copying" to see the conditions.
35777 There is absolutely no warranty for GDB. Type "show warranty"
35779 This GDB was configured as "i386-pc-linux-gnu"
35790 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35791 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35792 denotes a @samp{control-z} character) are annotations; the rest is
35793 output from @value{GDBN}.
35795 @node Server Prefix
35796 @section The Server Prefix
35797 @cindex server prefix
35799 If you prefix a command with @samp{server } then it will not affect
35800 the command history, nor will it affect @value{GDBN}'s notion of which
35801 command to repeat if @key{RET} is pressed on a line by itself. This
35802 means that commands can be run behind a user's back by a front-end in
35803 a transparent manner.
35805 The @code{server } prefix does not affect the recording of values into
35806 the value history; to print a value without recording it into the
35807 value history, use the @code{output} command instead of the
35808 @code{print} command.
35810 Using this prefix also disables confirmation requests
35811 (@pxref{confirmation requests}).
35814 @section Annotation for @value{GDBN} Input
35816 @cindex annotations for prompts
35817 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35818 to know when to send output, when the output from a given command is
35821 Different kinds of input each have a different @dfn{input type}. Each
35822 input type has three annotations: a @code{pre-} annotation, which
35823 denotes the beginning of any prompt which is being output, a plain
35824 annotation, which denotes the end of the prompt, and then a @code{post-}
35825 annotation which denotes the end of any echo which may (or may not) be
35826 associated with the input. For example, the @code{prompt} input type
35827 features the following annotations:
35835 The input types are
35838 @findex pre-prompt annotation
35839 @findex prompt annotation
35840 @findex post-prompt annotation
35842 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35844 @findex pre-commands annotation
35845 @findex commands annotation
35846 @findex post-commands annotation
35848 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35849 command. The annotations are repeated for each command which is input.
35851 @findex pre-overload-choice annotation
35852 @findex overload-choice annotation
35853 @findex post-overload-choice annotation
35854 @item overload-choice
35855 When @value{GDBN} wants the user to select between various overloaded functions.
35857 @findex pre-query annotation
35858 @findex query annotation
35859 @findex post-query annotation
35861 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35863 @findex pre-prompt-for-continue annotation
35864 @findex prompt-for-continue annotation
35865 @findex post-prompt-for-continue annotation
35866 @item prompt-for-continue
35867 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35868 expect this to work well; instead use @code{set height 0} to disable
35869 prompting. This is because the counting of lines is buggy in the
35870 presence of annotations.
35875 @cindex annotations for errors, warnings and interrupts
35877 @findex quit annotation
35882 This annotation occurs right before @value{GDBN} responds to an interrupt.
35884 @findex error annotation
35889 This annotation occurs right before @value{GDBN} responds to an error.
35891 Quit and error annotations indicate that any annotations which @value{GDBN} was
35892 in the middle of may end abruptly. For example, if a
35893 @code{value-history-begin} annotation is followed by a @code{error}, one
35894 cannot expect to receive the matching @code{value-history-end}. One
35895 cannot expect not to receive it either, however; an error annotation
35896 does not necessarily mean that @value{GDBN} is immediately returning all the way
35899 @findex error-begin annotation
35900 A quit or error annotation may be preceded by
35906 Any output between that and the quit or error annotation is the error
35909 Warning messages are not yet annotated.
35910 @c If we want to change that, need to fix warning(), type_error(),
35911 @c range_error(), and possibly other places.
35914 @section Invalidation Notices
35916 @cindex annotations for invalidation messages
35917 The following annotations say that certain pieces of state may have
35921 @findex frames-invalid annotation
35922 @item ^Z^Zframes-invalid
35924 The frames (for example, output from the @code{backtrace} command) may
35927 @findex breakpoints-invalid annotation
35928 @item ^Z^Zbreakpoints-invalid
35930 The breakpoints may have changed. For example, the user just added or
35931 deleted a breakpoint.
35934 @node Annotations for Running
35935 @section Running the Program
35936 @cindex annotations for running programs
35938 @findex starting annotation
35939 @findex stopping annotation
35940 When the program starts executing due to a @value{GDBN} command such as
35941 @code{step} or @code{continue},
35947 is output. When the program stops,
35953 is output. Before the @code{stopped} annotation, a variety of
35954 annotations describe how the program stopped.
35957 @findex exited annotation
35958 @item ^Z^Zexited @var{exit-status}
35959 The program exited, and @var{exit-status} is the exit status (zero for
35960 successful exit, otherwise nonzero).
35962 @findex signalled annotation
35963 @findex signal-name annotation
35964 @findex signal-name-end annotation
35965 @findex signal-string annotation
35966 @findex signal-string-end annotation
35967 @item ^Z^Zsignalled
35968 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35969 annotation continues:
35975 ^Z^Zsignal-name-end
35979 ^Z^Zsignal-string-end
35984 where @var{name} is the name of the signal, such as @code{SIGILL} or
35985 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35986 as @code{Illegal Instruction} or @code{Segmentation fault}.
35987 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35988 user's benefit and have no particular format.
35990 @findex signal annotation
35992 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35993 just saying that the program received the signal, not that it was
35994 terminated with it.
35996 @findex breakpoint annotation
35997 @item ^Z^Zbreakpoint @var{number}
35998 The program hit breakpoint number @var{number}.
36000 @findex watchpoint annotation
36001 @item ^Z^Zwatchpoint @var{number}
36002 The program hit watchpoint number @var{number}.
36005 @node Source Annotations
36006 @section Displaying Source
36007 @cindex annotations for source display
36009 @findex source annotation
36010 The following annotation is used instead of displaying source code:
36013 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
36016 where @var{filename} is an absolute file name indicating which source
36017 file, @var{line} is the line number within that file (where 1 is the
36018 first line in the file), @var{character} is the character position
36019 within the file (where 0 is the first character in the file) (for most
36020 debug formats this will necessarily point to the beginning of a line),
36021 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
36022 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
36023 @var{addr} is the address in the target program associated with the
36024 source which is being displayed. @var{addr} is in the form @samp{0x}
36025 followed by one or more lowercase hex digits (note that this does not
36026 depend on the language).
36028 @node JIT Interface
36029 @chapter JIT Compilation Interface
36030 @cindex just-in-time compilation
36031 @cindex JIT compilation interface
36033 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
36034 interface. A JIT compiler is a program or library that generates native
36035 executable code at runtime and executes it, usually in order to achieve good
36036 performance while maintaining platform independence.
36038 Programs that use JIT compilation are normally difficult to debug because
36039 portions of their code are generated at runtime, instead of being loaded from
36040 object files, which is where @value{GDBN} normally finds the program's symbols
36041 and debug information. In order to debug programs that use JIT compilation,
36042 @value{GDBN} has an interface that allows the program to register in-memory
36043 symbol files with @value{GDBN} at runtime.
36045 If you are using @value{GDBN} to debug a program that uses this interface, then
36046 it should work transparently so long as you have not stripped the binary. If
36047 you are developing a JIT compiler, then the interface is documented in the rest
36048 of this chapter. At this time, the only known client of this interface is the
36051 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
36052 JIT compiler communicates with @value{GDBN} by writing data into a global
36053 variable and calling a fuction at a well-known symbol. When @value{GDBN}
36054 attaches, it reads a linked list of symbol files from the global variable to
36055 find existing code, and puts a breakpoint in the function so that it can find
36056 out about additional code.
36059 * Declarations:: Relevant C struct declarations
36060 * Registering Code:: Steps to register code
36061 * Unregistering Code:: Steps to unregister code
36062 * Custom Debug Info:: Emit debug information in a custom format
36066 @section JIT Declarations
36068 These are the relevant struct declarations that a C program should include to
36069 implement the interface:
36079 struct jit_code_entry
36081 struct jit_code_entry *next_entry;
36082 struct jit_code_entry *prev_entry;
36083 const char *symfile_addr;
36084 uint64_t symfile_size;
36087 struct jit_descriptor
36090 /* This type should be jit_actions_t, but we use uint32_t
36091 to be explicit about the bitwidth. */
36092 uint32_t action_flag;
36093 struct jit_code_entry *relevant_entry;
36094 struct jit_code_entry *first_entry;
36097 /* GDB puts a breakpoint in this function. */
36098 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
36100 /* Make sure to specify the version statically, because the
36101 debugger may check the version before we can set it. */
36102 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
36105 If the JIT is multi-threaded, then it is important that the JIT synchronize any
36106 modifications to this global data properly, which can easily be done by putting
36107 a global mutex around modifications to these structures.
36109 @node Registering Code
36110 @section Registering Code
36112 To register code with @value{GDBN}, the JIT should follow this protocol:
36116 Generate an object file in memory with symbols and other desired debug
36117 information. The file must include the virtual addresses of the sections.
36120 Create a code entry for the file, which gives the start and size of the symbol
36124 Add it to the linked list in the JIT descriptor.
36127 Point the relevant_entry field of the descriptor at the entry.
36130 Set @code{action_flag} to @code{JIT_REGISTER} and call
36131 @code{__jit_debug_register_code}.
36134 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
36135 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
36136 new code. However, the linked list must still be maintained in order to allow
36137 @value{GDBN} to attach to a running process and still find the symbol files.
36139 @node Unregistering Code
36140 @section Unregistering Code
36142 If code is freed, then the JIT should use the following protocol:
36146 Remove the code entry corresponding to the code from the linked list.
36149 Point the @code{relevant_entry} field of the descriptor at the code entry.
36152 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
36153 @code{__jit_debug_register_code}.
36156 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
36157 and the JIT will leak the memory used for the associated symbol files.
36159 @node Custom Debug Info
36160 @section Custom Debug Info
36161 @cindex custom JIT debug info
36162 @cindex JIT debug info reader
36164 Generating debug information in platform-native file formats (like ELF
36165 or COFF) may be an overkill for JIT compilers; especially if all the
36166 debug info is used for is displaying a meaningful backtrace. The
36167 issue can be resolved by having the JIT writers decide on a debug info
36168 format and also provide a reader that parses the debug info generated
36169 by the JIT compiler. This section gives a brief overview on writing
36170 such a parser. More specific details can be found in the source file
36171 @file{gdb/jit-reader.in}, which is also installed as a header at
36172 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
36174 The reader is implemented as a shared object (so this functionality is
36175 not available on platforms which don't allow loading shared objects at
36176 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36177 @code{jit-reader-unload} are provided, to be used to load and unload
36178 the readers from a preconfigured directory. Once loaded, the shared
36179 object is used the parse the debug information emitted by the JIT
36183 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36184 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36187 @node Using JIT Debug Info Readers
36188 @subsection Using JIT Debug Info Readers
36189 @kindex jit-reader-load
36190 @kindex jit-reader-unload
36192 Readers can be loaded and unloaded using the @code{jit-reader-load}
36193 and @code{jit-reader-unload} commands.
36196 @item jit-reader-load @var{reader}
36197 Load the JIT reader named @var{reader}. @var{reader} is a shared
36198 object specified as either an absolute or a relative file name. In
36199 the latter case, @value{GDBN} will try to load the reader from a
36200 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36201 system (here @var{libdir} is the system library directory, often
36202 @file{/usr/local/lib}).
36204 Only one reader can be active at a time; trying to load a second
36205 reader when one is already loaded will result in @value{GDBN}
36206 reporting an error. A new JIT reader can be loaded by first unloading
36207 the current one using @code{jit-reader-unload} and then invoking
36208 @code{jit-reader-load}.
36210 @item jit-reader-unload
36211 Unload the currently loaded JIT reader.
36215 @node Writing JIT Debug Info Readers
36216 @subsection Writing JIT Debug Info Readers
36217 @cindex writing JIT debug info readers
36219 As mentioned, a reader is essentially a shared object conforming to a
36220 certain ABI. This ABI is described in @file{jit-reader.h}.
36222 @file{jit-reader.h} defines the structures, macros and functions
36223 required to write a reader. It is installed (along with
36224 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36225 the system include directory.
36227 Readers need to be released under a GPL compatible license. A reader
36228 can be declared as released under such a license by placing the macro
36229 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36231 The entry point for readers is the symbol @code{gdb_init_reader},
36232 which is expected to be a function with the prototype
36234 @findex gdb_init_reader
36236 extern struct gdb_reader_funcs *gdb_init_reader (void);
36239 @cindex @code{struct gdb_reader_funcs}
36241 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36242 functions. These functions are executed to read the debug info
36243 generated by the JIT compiler (@code{read}), to unwind stack frames
36244 (@code{unwind}) and to create canonical frame IDs
36245 (@code{get_Frame_id}). It also has a callback that is called when the
36246 reader is being unloaded (@code{destroy}). The struct looks like this
36249 struct gdb_reader_funcs
36251 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36252 int reader_version;
36254 /* For use by the reader. */
36257 gdb_read_debug_info *read;
36258 gdb_unwind_frame *unwind;
36259 gdb_get_frame_id *get_frame_id;
36260 gdb_destroy_reader *destroy;
36264 @cindex @code{struct gdb_symbol_callbacks}
36265 @cindex @code{struct gdb_unwind_callbacks}
36267 The callbacks are provided with another set of callbacks by
36268 @value{GDBN} to do their job. For @code{read}, these callbacks are
36269 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36270 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36271 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36272 files and new symbol tables inside those object files. @code{struct
36273 gdb_unwind_callbacks} has callbacks to read registers off the current
36274 frame and to write out the values of the registers in the previous
36275 frame. Both have a callback (@code{target_read}) to read bytes off the
36276 target's address space.
36278 @node In-Process Agent
36279 @chapter In-Process Agent
36280 @cindex debugging agent
36281 The traditional debugging model is conceptually low-speed, but works fine,
36282 because most bugs can be reproduced in debugging-mode execution. However,
36283 as multi-core or many-core processors are becoming mainstream, and
36284 multi-threaded programs become more and more popular, there should be more
36285 and more bugs that only manifest themselves at normal-mode execution, for
36286 example, thread races, because debugger's interference with the program's
36287 timing may conceal the bugs. On the other hand, in some applications,
36288 it is not feasible for the debugger to interrupt the program's execution
36289 long enough for the developer to learn anything helpful about its behavior.
36290 If the program's correctness depends on its real-time behavior, delays
36291 introduced by a debugger might cause the program to fail, even when the
36292 code itself is correct. It is useful to be able to observe the program's
36293 behavior without interrupting it.
36295 Therefore, traditional debugging model is too intrusive to reproduce
36296 some bugs. In order to reduce the interference with the program, we can
36297 reduce the number of operations performed by debugger. The
36298 @dfn{In-Process Agent}, a shared library, is running within the same
36299 process with inferior, and is able to perform some debugging operations
36300 itself. As a result, debugger is only involved when necessary, and
36301 performance of debugging can be improved accordingly. Note that
36302 interference with program can be reduced but can't be removed completely,
36303 because the in-process agent will still stop or slow down the program.
36305 The in-process agent can interpret and execute Agent Expressions
36306 (@pxref{Agent Expressions}) during performing debugging operations. The
36307 agent expressions can be used for different purposes, such as collecting
36308 data in tracepoints, and condition evaluation in breakpoints.
36310 @anchor{Control Agent}
36311 You can control whether the in-process agent is used as an aid for
36312 debugging with the following commands:
36315 @kindex set agent on
36317 Causes the in-process agent to perform some operations on behalf of the
36318 debugger. Just which operations requested by the user will be done
36319 by the in-process agent depends on the its capabilities. For example,
36320 if you request to evaluate breakpoint conditions in the in-process agent,
36321 and the in-process agent has such capability as well, then breakpoint
36322 conditions will be evaluated in the in-process agent.
36324 @kindex set agent off
36325 @item set agent off
36326 Disables execution of debugging operations by the in-process agent. All
36327 of the operations will be performed by @value{GDBN}.
36331 Display the current setting of execution of debugging operations by
36332 the in-process agent.
36336 * In-Process Agent Protocol::
36339 @node In-Process Agent Protocol
36340 @section In-Process Agent Protocol
36341 @cindex in-process agent protocol
36343 The in-process agent is able to communicate with both @value{GDBN} and
36344 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36345 used for communications between @value{GDBN} or GDBserver and the IPA.
36346 In general, @value{GDBN} or GDBserver sends commands
36347 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36348 in-process agent replies back with the return result of the command, or
36349 some other information. The data sent to in-process agent is composed
36350 of primitive data types, such as 4-byte or 8-byte type, and composite
36351 types, which are called objects (@pxref{IPA Protocol Objects}).
36354 * IPA Protocol Objects::
36355 * IPA Protocol Commands::
36358 @node IPA Protocol Objects
36359 @subsection IPA Protocol Objects
36360 @cindex ipa protocol objects
36362 The commands sent to and results received from agent may contain some
36363 complex data types called @dfn{objects}.
36365 The in-process agent is running on the same machine with @value{GDBN}
36366 or GDBserver, so it doesn't have to handle as much differences between
36367 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36368 However, there are still some differences of two ends in two processes:
36372 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36373 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36375 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36376 GDBserver is compiled with one, and in-process agent is compiled with
36380 Here are the IPA Protocol Objects:
36384 agent expression object. It represents an agent expression
36385 (@pxref{Agent Expressions}).
36386 @anchor{agent expression object}
36388 tracepoint action object. It represents a tracepoint action
36389 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36390 memory, static trace data and to evaluate expression.
36391 @anchor{tracepoint action object}
36393 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36394 @anchor{tracepoint object}
36398 The following table describes important attributes of each IPA protocol
36401 @multitable @columnfractions .30 .20 .50
36402 @headitem Name @tab Size @tab Description
36403 @item @emph{agent expression object} @tab @tab
36404 @item length @tab 4 @tab length of bytes code
36405 @item byte code @tab @var{length} @tab contents of byte code
36406 @item @emph{tracepoint action for collecting memory} @tab @tab
36407 @item 'M' @tab 1 @tab type of tracepoint action
36408 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36409 address of the lowest byte to collect, otherwise @var{addr} is the offset
36410 of @var{basereg} for memory collecting.
36411 @item len @tab 8 @tab length of memory for collecting
36412 @item basereg @tab 4 @tab the register number containing the starting
36413 memory address for collecting.
36414 @item @emph{tracepoint action for collecting registers} @tab @tab
36415 @item 'R' @tab 1 @tab type of tracepoint action
36416 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36417 @item 'L' @tab 1 @tab type of tracepoint action
36418 @item @emph{tracepoint action for expression evaluation} @tab @tab
36419 @item 'X' @tab 1 @tab type of tracepoint action
36420 @item agent expression @tab length of @tab @ref{agent expression object}
36421 @item @emph{tracepoint object} @tab @tab
36422 @item number @tab 4 @tab number of tracepoint
36423 @item address @tab 8 @tab address of tracepoint inserted on
36424 @item type @tab 4 @tab type of tracepoint
36425 @item enabled @tab 1 @tab enable or disable of tracepoint
36426 @item step_count @tab 8 @tab step
36427 @item pass_count @tab 8 @tab pass
36428 @item numactions @tab 4 @tab number of tracepoint actions
36429 @item hit count @tab 8 @tab hit count
36430 @item trace frame usage @tab 8 @tab trace frame usage
36431 @item compiled_cond @tab 8 @tab compiled condition
36432 @item orig_size @tab 8 @tab orig size
36433 @item condition @tab 4 if condition is NULL otherwise length of
36434 @ref{agent expression object}
36435 @tab zero if condition is NULL, otherwise is
36436 @ref{agent expression object}
36437 @item actions @tab variable
36438 @tab numactions number of @ref{tracepoint action object}
36441 @node IPA Protocol Commands
36442 @subsection IPA Protocol Commands
36443 @cindex ipa protocol commands
36445 The spaces in each command are delimiters to ease reading this commands
36446 specification. They don't exist in real commands.
36450 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36451 Installs a new fast tracepoint described by @var{tracepoint_object}
36452 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36453 head of @dfn{jumppad}, which is used to jump to data collection routine
36458 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36459 @var{target_address} is address of tracepoint in the inferior.
36460 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36461 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36462 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36463 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36470 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36471 is about to kill inferiors.
36479 @item probe_marker_at:@var{address}
36480 Asks in-process agent to probe the marker at @var{address}.
36487 @item unprobe_marker_at:@var{address}
36488 Asks in-process agent to unprobe the marker at @var{address}.
36492 @chapter Reporting Bugs in @value{GDBN}
36493 @cindex bugs in @value{GDBN}
36494 @cindex reporting bugs in @value{GDBN}
36496 Your bug reports play an essential role in making @value{GDBN} reliable.
36498 Reporting a bug may help you by bringing a solution to your problem, or it
36499 may not. But in any case the principal function of a bug report is to help
36500 the entire community by making the next version of @value{GDBN} work better. Bug
36501 reports are your contribution to the maintenance of @value{GDBN}.
36503 In order for a bug report to serve its purpose, you must include the
36504 information that enables us to fix the bug.
36507 * Bug Criteria:: Have you found a bug?
36508 * Bug Reporting:: How to report bugs
36512 @section Have You Found a Bug?
36513 @cindex bug criteria
36515 If you are not sure whether you have found a bug, here are some guidelines:
36518 @cindex fatal signal
36519 @cindex debugger crash
36520 @cindex crash of debugger
36522 If the debugger gets a fatal signal, for any input whatever, that is a
36523 @value{GDBN} bug. Reliable debuggers never crash.
36525 @cindex error on valid input
36527 If @value{GDBN} produces an error message for valid input, that is a
36528 bug. (Note that if you're cross debugging, the problem may also be
36529 somewhere in the connection to the target.)
36531 @cindex invalid input
36533 If @value{GDBN} does not produce an error message for invalid input,
36534 that is a bug. However, you should note that your idea of
36535 ``invalid input'' might be our idea of ``an extension'' or ``support
36536 for traditional practice''.
36539 If you are an experienced user of debugging tools, your suggestions
36540 for improvement of @value{GDBN} are welcome in any case.
36543 @node Bug Reporting
36544 @section How to Report Bugs
36545 @cindex bug reports
36546 @cindex @value{GDBN} bugs, reporting
36548 A number of companies and individuals offer support for @sc{gnu} products.
36549 If you obtained @value{GDBN} from a support organization, we recommend you
36550 contact that organization first.
36552 You can find contact information for many support companies and
36553 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36555 @c should add a web page ref...
36558 @ifset BUGURL_DEFAULT
36559 In any event, we also recommend that you submit bug reports for
36560 @value{GDBN}. The preferred method is to submit them directly using
36561 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36562 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36565 @strong{Do not send bug reports to @samp{info-gdb}, or to
36566 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36567 not want to receive bug reports. Those that do have arranged to receive
36570 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36571 serves as a repeater. The mailing list and the newsgroup carry exactly
36572 the same messages. Often people think of posting bug reports to the
36573 newsgroup instead of mailing them. This appears to work, but it has one
36574 problem which can be crucial: a newsgroup posting often lacks a mail
36575 path back to the sender. Thus, if we need to ask for more information,
36576 we may be unable to reach you. For this reason, it is better to send
36577 bug reports to the mailing list.
36579 @ifclear BUGURL_DEFAULT
36580 In any event, we also recommend that you submit bug reports for
36581 @value{GDBN} to @value{BUGURL}.
36585 The fundamental principle of reporting bugs usefully is this:
36586 @strong{report all the facts}. If you are not sure whether to state a
36587 fact or leave it out, state it!
36589 Often people omit facts because they think they know what causes the
36590 problem and assume that some details do not matter. Thus, you might
36591 assume that the name of the variable you use in an example does not matter.
36592 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36593 stray memory reference which happens to fetch from the location where that
36594 name is stored in memory; perhaps, if the name were different, the contents
36595 of that location would fool the debugger into doing the right thing despite
36596 the bug. Play it safe and give a specific, complete example. That is the
36597 easiest thing for you to do, and the most helpful.
36599 Keep in mind that the purpose of a bug report is to enable us to fix the
36600 bug. It may be that the bug has been reported previously, but neither
36601 you nor we can know that unless your bug report is complete and
36604 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36605 bell?'' Those bug reports are useless, and we urge everyone to
36606 @emph{refuse to respond to them} except to chide the sender to report
36609 To enable us to fix the bug, you should include all these things:
36613 The version of @value{GDBN}. @value{GDBN} announces it if you start
36614 with no arguments; you can also print it at any time using @code{show
36617 Without this, we will not know whether there is any point in looking for
36618 the bug in the current version of @value{GDBN}.
36621 The type of machine you are using, and the operating system name and
36625 The details of the @value{GDBN} build-time configuration.
36626 @value{GDBN} shows these details if you invoke it with the
36627 @option{--configuration} command-line option, or if you type
36628 @code{show configuration} at @value{GDBN}'s prompt.
36631 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36632 ``@value{GCC}--2.8.1''.
36635 What compiler (and its version) was used to compile the program you are
36636 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36637 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36638 to get this information; for other compilers, see the documentation for
36642 The command arguments you gave the compiler to compile your example and
36643 observe the bug. For example, did you use @samp{-O}? To guarantee
36644 you will not omit something important, list them all. A copy of the
36645 Makefile (or the output from make) is sufficient.
36647 If we were to try to guess the arguments, we would probably guess wrong
36648 and then we might not encounter the bug.
36651 A complete input script, and all necessary source files, that will
36655 A description of what behavior you observe that you believe is
36656 incorrect. For example, ``It gets a fatal signal.''
36658 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36659 will certainly notice it. But if the bug is incorrect output, we might
36660 not notice unless it is glaringly wrong. You might as well not give us
36661 a chance to make a mistake.
36663 Even if the problem you experience is a fatal signal, you should still
36664 say so explicitly. Suppose something strange is going on, such as, your
36665 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36666 the C library on your system. (This has happened!) Your copy might
36667 crash and ours would not. If you told us to expect a crash, then when
36668 ours fails to crash, we would know that the bug was not happening for
36669 us. If you had not told us to expect a crash, then we would not be able
36670 to draw any conclusion from our observations.
36673 @cindex recording a session script
36674 To collect all this information, you can use a session recording program
36675 such as @command{script}, which is available on many Unix systems.
36676 Just run your @value{GDBN} session inside @command{script} and then
36677 include the @file{typescript} file with your bug report.
36679 Another way to record a @value{GDBN} session is to run @value{GDBN}
36680 inside Emacs and then save the entire buffer to a file.
36683 If you wish to suggest changes to the @value{GDBN} source, send us context
36684 diffs. If you even discuss something in the @value{GDBN} source, refer to
36685 it by context, not by line number.
36687 The line numbers in our development sources will not match those in your
36688 sources. Your line numbers would convey no useful information to us.
36692 Here are some things that are not necessary:
36696 A description of the envelope of the bug.
36698 Often people who encounter a bug spend a lot of time investigating
36699 which changes to the input file will make the bug go away and which
36700 changes will not affect it.
36702 This is often time consuming and not very useful, because the way we
36703 will find the bug is by running a single example under the debugger
36704 with breakpoints, not by pure deduction from a series of examples.
36705 We recommend that you save your time for something else.
36707 Of course, if you can find a simpler example to report @emph{instead}
36708 of the original one, that is a convenience for us. Errors in the
36709 output will be easier to spot, running under the debugger will take
36710 less time, and so on.
36712 However, simplification is not vital; if you do not want to do this,
36713 report the bug anyway and send us the entire test case you used.
36716 A patch for the bug.
36718 A patch for the bug does help us if it is a good one. But do not omit
36719 the necessary information, such as the test case, on the assumption that
36720 a patch is all we need. We might see problems with your patch and decide
36721 to fix the problem another way, or we might not understand it at all.
36723 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36724 construct an example that will make the program follow a certain path
36725 through the code. If you do not send us the example, we will not be able
36726 to construct one, so we will not be able to verify that the bug is fixed.
36728 And if we cannot understand what bug you are trying to fix, or why your
36729 patch should be an improvement, we will not install it. A test case will
36730 help us to understand.
36733 A guess about what the bug is or what it depends on.
36735 Such guesses are usually wrong. Even we cannot guess right about such
36736 things without first using the debugger to find the facts.
36739 @c The readline documentation is distributed with the readline code
36740 @c and consists of the two following files:
36743 @c Use -I with makeinfo to point to the appropriate directory,
36744 @c environment var TEXINPUTS with TeX.
36745 @ifclear SYSTEM_READLINE
36746 @include rluser.texi
36747 @include hsuser.texi
36751 @appendix In Memoriam
36753 The @value{GDBN} project mourns the loss of the following long-time
36758 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36759 to Free Software in general. Outside of @value{GDBN}, he was known in
36760 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36762 @item Michael Snyder
36763 Michael was one of the Global Maintainers of the @value{GDBN} project,
36764 with contributions recorded as early as 1996, until 2011. In addition
36765 to his day to day participation, he was a large driving force behind
36766 adding Reverse Debugging to @value{GDBN}.
36769 Beyond their technical contributions to the project, they were also
36770 enjoyable members of the Free Software Community. We will miss them.
36772 @node Formatting Documentation
36773 @appendix Formatting Documentation
36775 @cindex @value{GDBN} reference card
36776 @cindex reference card
36777 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36778 for printing with PostScript or Ghostscript, in the @file{gdb}
36779 subdirectory of the main source directory@footnote{In
36780 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36781 release.}. If you can use PostScript or Ghostscript with your printer,
36782 you can print the reference card immediately with @file{refcard.ps}.
36784 The release also includes the source for the reference card. You
36785 can format it, using @TeX{}, by typing:
36791 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36792 mode on US ``letter'' size paper;
36793 that is, on a sheet 11 inches wide by 8.5 inches
36794 high. You will need to specify this form of printing as an option to
36795 your @sc{dvi} output program.
36797 @cindex documentation
36799 All the documentation for @value{GDBN} comes as part of the machine-readable
36800 distribution. The documentation is written in Texinfo format, which is
36801 a documentation system that uses a single source file to produce both
36802 on-line information and a printed manual. You can use one of the Info
36803 formatting commands to create the on-line version of the documentation
36804 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36806 @value{GDBN} includes an already formatted copy of the on-line Info
36807 version of this manual in the @file{gdb} subdirectory. The main Info
36808 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36809 subordinate files matching @samp{gdb.info*} in the same directory. If
36810 necessary, you can print out these files, or read them with any editor;
36811 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36812 Emacs or the standalone @code{info} program, available as part of the
36813 @sc{gnu} Texinfo distribution.
36815 If you want to format these Info files yourself, you need one of the
36816 Info formatting programs, such as @code{texinfo-format-buffer} or
36819 If you have @code{makeinfo} installed, and are in the top level
36820 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36821 version @value{GDBVN}), you can make the Info file by typing:
36828 If you want to typeset and print copies of this manual, you need @TeX{},
36829 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36830 Texinfo definitions file.
36832 @TeX{} is a typesetting program; it does not print files directly, but
36833 produces output files called @sc{dvi} files. To print a typeset
36834 document, you need a program to print @sc{dvi} files. If your system
36835 has @TeX{} installed, chances are it has such a program. The precise
36836 command to use depends on your system; @kbd{lpr -d} is common; another
36837 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36838 require a file name without any extension or a @samp{.dvi} extension.
36840 @TeX{} also requires a macro definitions file called
36841 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36842 written in Texinfo format. On its own, @TeX{} cannot either read or
36843 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36844 and is located in the @file{gdb-@var{version-number}/texinfo}
36847 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36848 typeset and print this manual. First switch to the @file{gdb}
36849 subdirectory of the main source directory (for example, to
36850 @file{gdb-@value{GDBVN}/gdb}) and type:
36856 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36858 @node Installing GDB
36859 @appendix Installing @value{GDBN}
36860 @cindex installation
36863 * Requirements:: Requirements for building @value{GDBN}
36864 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36865 * Separate Objdir:: Compiling @value{GDBN} in another directory
36866 * Config Names:: Specifying names for hosts and targets
36867 * Configure Options:: Summary of options for configure
36868 * System-wide configuration:: Having a system-wide init file
36872 @section Requirements for Building @value{GDBN}
36873 @cindex building @value{GDBN}, requirements for
36875 Building @value{GDBN} requires various tools and packages to be available.
36876 Other packages will be used only if they are found.
36878 @heading Tools/Packages Necessary for Building @value{GDBN}
36880 @item ISO C90 compiler
36881 @value{GDBN} is written in ISO C90. It should be buildable with any
36882 working C90 compiler, e.g.@: GCC.
36886 @heading Tools/Packages Optional for Building @value{GDBN}
36890 @value{GDBN} can use the Expat XML parsing library. This library may be
36891 included with your operating system distribution; if it is not, you
36892 can get the latest version from @url{http://expat.sourceforge.net}.
36893 The @file{configure} script will search for this library in several
36894 standard locations; if it is installed in an unusual path, you can
36895 use the @option{--with-libexpat-prefix} option to specify its location.
36901 Remote protocol memory maps (@pxref{Memory Map Format})
36903 Target descriptions (@pxref{Target Descriptions})
36905 Remote shared library lists (@xref{Library List Format},
36906 or alternatively @pxref{Library List Format for SVR4 Targets})
36908 MS-Windows shared libraries (@pxref{Shared Libraries})
36910 Traceframe info (@pxref{Traceframe Info Format})
36912 Branch trace (@pxref{Branch Trace Format})
36916 @cindex compressed debug sections
36917 @value{GDBN} will use the @samp{zlib} library, if available, to read
36918 compressed debug sections. Some linkers, such as GNU gold, are capable
36919 of producing binaries with compressed debug sections. If @value{GDBN}
36920 is compiled with @samp{zlib}, it will be able to read the debug
36921 information in such binaries.
36923 The @samp{zlib} library is likely included with your operating system
36924 distribution; if it is not, you can get the latest version from
36925 @url{http://zlib.net}.
36928 @value{GDBN}'s features related to character sets (@pxref{Character
36929 Sets}) require a functioning @code{iconv} implementation. If you are
36930 on a GNU system, then this is provided by the GNU C Library. Some
36931 other systems also provide a working @code{iconv}.
36933 If @value{GDBN} is using the @code{iconv} program which is installed
36934 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36935 This is done with @option{--with-iconv-bin} which specifies the
36936 directory that contains the @code{iconv} program.
36938 On systems without @code{iconv}, you can install GNU Libiconv. If you
36939 have previously installed Libiconv, you can use the
36940 @option{--with-libiconv-prefix} option to configure.
36942 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36943 arrange to build Libiconv if a directory named @file{libiconv} appears
36944 in the top-most source directory. If Libiconv is built this way, and
36945 if the operating system does not provide a suitable @code{iconv}
36946 implementation, then the just-built library will automatically be used
36947 by @value{GDBN}. One easy way to set this up is to download GNU
36948 Libiconv, unpack it, and then rename the directory holding the
36949 Libiconv source code to @samp{libiconv}.
36952 @node Running Configure
36953 @section Invoking the @value{GDBN} @file{configure} Script
36954 @cindex configuring @value{GDBN}
36955 @value{GDBN} comes with a @file{configure} script that automates the process
36956 of preparing @value{GDBN} for installation; you can then use @code{make} to
36957 build the @code{gdb} program.
36959 @c irrelevant in info file; it's as current as the code it lives with.
36960 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36961 look at the @file{README} file in the sources; we may have improved the
36962 installation procedures since publishing this manual.}
36965 The @value{GDBN} distribution includes all the source code you need for
36966 @value{GDBN} in a single directory, whose name is usually composed by
36967 appending the version number to @samp{gdb}.
36969 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36970 @file{gdb-@value{GDBVN}} directory. That directory contains:
36973 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36974 script for configuring @value{GDBN} and all its supporting libraries
36976 @item gdb-@value{GDBVN}/gdb
36977 the source specific to @value{GDBN} itself
36979 @item gdb-@value{GDBVN}/bfd
36980 source for the Binary File Descriptor library
36982 @item gdb-@value{GDBVN}/include
36983 @sc{gnu} include files
36985 @item gdb-@value{GDBVN}/libiberty
36986 source for the @samp{-liberty} free software library
36988 @item gdb-@value{GDBVN}/opcodes
36989 source for the library of opcode tables and disassemblers
36991 @item gdb-@value{GDBVN}/readline
36992 source for the @sc{gnu} command-line interface
36994 @item gdb-@value{GDBVN}/glob
36995 source for the @sc{gnu} filename pattern-matching subroutine
36997 @item gdb-@value{GDBVN}/mmalloc
36998 source for the @sc{gnu} memory-mapped malloc package
37001 The simplest way to configure and build @value{GDBN} is to run @file{configure}
37002 from the @file{gdb-@var{version-number}} source directory, which in
37003 this example is the @file{gdb-@value{GDBVN}} directory.
37005 First switch to the @file{gdb-@var{version-number}} source directory
37006 if you are not already in it; then run @file{configure}. Pass the
37007 identifier for the platform on which @value{GDBN} will run as an
37013 cd gdb-@value{GDBVN}
37014 ./configure @var{host}
37019 where @var{host} is an identifier such as @samp{sun4} or
37020 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
37021 (You can often leave off @var{host}; @file{configure} tries to guess the
37022 correct value by examining your system.)
37024 Running @samp{configure @var{host}} and then running @code{make} builds the
37025 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
37026 libraries, then @code{gdb} itself. The configured source files, and the
37027 binaries, are left in the corresponding source directories.
37030 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
37031 system does not recognize this automatically when you run a different
37032 shell, you may need to run @code{sh} on it explicitly:
37035 sh configure @var{host}
37038 If you run @file{configure} from a directory that contains source
37039 directories for multiple libraries or programs, such as the
37040 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
37042 creates configuration files for every directory level underneath (unless
37043 you tell it not to, with the @samp{--norecursion} option).
37045 You should run the @file{configure} script from the top directory in the
37046 source tree, the @file{gdb-@var{version-number}} directory. If you run
37047 @file{configure} from one of the subdirectories, you will configure only
37048 that subdirectory. That is usually not what you want. In particular,
37049 if you run the first @file{configure} from the @file{gdb} subdirectory
37050 of the @file{gdb-@var{version-number}} directory, you will omit the
37051 configuration of @file{bfd}, @file{readline}, and other sibling
37052 directories of the @file{gdb} subdirectory. This leads to build errors
37053 about missing include files such as @file{bfd/bfd.h}.
37055 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
37056 However, you should make sure that the shell on your path (named by
37057 the @samp{SHELL} environment variable) is publicly readable. Remember
37058 that @value{GDBN} uses the shell to start your program---some systems refuse to
37059 let @value{GDBN} debug child processes whose programs are not readable.
37061 @node Separate Objdir
37062 @section Compiling @value{GDBN} in Another Directory
37064 If you want to run @value{GDBN} versions for several host or target machines,
37065 you need a different @code{gdb} compiled for each combination of
37066 host and target. @file{configure} is designed to make this easy by
37067 allowing you to generate each configuration in a separate subdirectory,
37068 rather than in the source directory. If your @code{make} program
37069 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
37070 @code{make} in each of these directories builds the @code{gdb}
37071 program specified there.
37073 To build @code{gdb} in a separate directory, run @file{configure}
37074 with the @samp{--srcdir} option to specify where to find the source.
37075 (You also need to specify a path to find @file{configure}
37076 itself from your working directory. If the path to @file{configure}
37077 would be the same as the argument to @samp{--srcdir}, you can leave out
37078 the @samp{--srcdir} option; it is assumed.)
37080 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
37081 separate directory for a Sun 4 like this:
37085 cd gdb-@value{GDBVN}
37088 ../gdb-@value{GDBVN}/configure sun4
37093 When @file{configure} builds a configuration using a remote source
37094 directory, it creates a tree for the binaries with the same structure
37095 (and using the same names) as the tree under the source directory. In
37096 the example, you'd find the Sun 4 library @file{libiberty.a} in the
37097 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
37098 @file{gdb-sun4/gdb}.
37100 Make sure that your path to the @file{configure} script has just one
37101 instance of @file{gdb} in it. If your path to @file{configure} looks
37102 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
37103 one subdirectory of @value{GDBN}, not the whole package. This leads to
37104 build errors about missing include files such as @file{bfd/bfd.h}.
37106 One popular reason to build several @value{GDBN} configurations in separate
37107 directories is to configure @value{GDBN} for cross-compiling (where
37108 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
37109 programs that run on another machine---the @dfn{target}).
37110 You specify a cross-debugging target by
37111 giving the @samp{--target=@var{target}} option to @file{configure}.
37113 When you run @code{make} to build a program or library, you must run
37114 it in a configured directory---whatever directory you were in when you
37115 called @file{configure} (or one of its subdirectories).
37117 The @code{Makefile} that @file{configure} generates in each source
37118 directory also runs recursively. If you type @code{make} in a source
37119 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
37120 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
37121 will build all the required libraries, and then build GDB.
37123 When you have multiple hosts or targets configured in separate
37124 directories, you can run @code{make} on them in parallel (for example,
37125 if they are NFS-mounted on each of the hosts); they will not interfere
37129 @section Specifying Names for Hosts and Targets
37131 The specifications used for hosts and targets in the @file{configure}
37132 script are based on a three-part naming scheme, but some short predefined
37133 aliases are also supported. The full naming scheme encodes three pieces
37134 of information in the following pattern:
37137 @var{architecture}-@var{vendor}-@var{os}
37140 For example, you can use the alias @code{sun4} as a @var{host} argument,
37141 or as the value for @var{target} in a @code{--target=@var{target}}
37142 option. The equivalent full name is @samp{sparc-sun-sunos4}.
37144 The @file{configure} script accompanying @value{GDBN} does not provide
37145 any query facility to list all supported host and target names or
37146 aliases. @file{configure} calls the Bourne shell script
37147 @code{config.sub} to map abbreviations to full names; you can read the
37148 script, if you wish, or you can use it to test your guesses on
37149 abbreviations---for example:
37152 % sh config.sub i386-linux
37154 % sh config.sub alpha-linux
37155 alpha-unknown-linux-gnu
37156 % sh config.sub hp9k700
37158 % sh config.sub sun4
37159 sparc-sun-sunos4.1.1
37160 % sh config.sub sun3
37161 m68k-sun-sunos4.1.1
37162 % sh config.sub i986v
37163 Invalid configuration `i986v': machine `i986v' not recognized
37167 @code{config.sub} is also distributed in the @value{GDBN} source
37168 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
37170 @node Configure Options
37171 @section @file{configure} Options
37173 Here is a summary of the @file{configure} options and arguments that
37174 are most often useful for building @value{GDBN}. @file{configure} also has
37175 several other options not listed here. @inforef{What Configure
37176 Does,,configure.info}, for a full explanation of @file{configure}.
37179 configure @r{[}--help@r{]}
37180 @r{[}--prefix=@var{dir}@r{]}
37181 @r{[}--exec-prefix=@var{dir}@r{]}
37182 @r{[}--srcdir=@var{dirname}@r{]}
37183 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
37184 @r{[}--target=@var{target}@r{]}
37189 You may introduce options with a single @samp{-} rather than
37190 @samp{--} if you prefer; but you may abbreviate option names if you use
37195 Display a quick summary of how to invoke @file{configure}.
37197 @item --prefix=@var{dir}
37198 Configure the source to install programs and files under directory
37201 @item --exec-prefix=@var{dir}
37202 Configure the source to install programs under directory
37205 @c avoid splitting the warning from the explanation:
37207 @item --srcdir=@var{dirname}
37208 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
37209 @code{make} that implements the @code{VPATH} feature.}@*
37210 Use this option to make configurations in directories separate from the
37211 @value{GDBN} source directories. Among other things, you can use this to
37212 build (or maintain) several configurations simultaneously, in separate
37213 directories. @file{configure} writes configuration-specific files in
37214 the current directory, but arranges for them to use the source in the
37215 directory @var{dirname}. @file{configure} creates directories under
37216 the working directory in parallel to the source directories below
37219 @item --norecursion
37220 Configure only the directory level where @file{configure} is executed; do not
37221 propagate configuration to subdirectories.
37223 @item --target=@var{target}
37224 Configure @value{GDBN} for cross-debugging programs running on the specified
37225 @var{target}. Without this option, @value{GDBN} is configured to debug
37226 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37228 There is no convenient way to generate a list of all available targets.
37230 @item @var{host} @dots{}
37231 Configure @value{GDBN} to run on the specified @var{host}.
37233 There is no convenient way to generate a list of all available hosts.
37236 There are many other options available as well, but they are generally
37237 needed for special purposes only.
37239 @node System-wide configuration
37240 @section System-wide configuration and settings
37241 @cindex system-wide init file
37243 @value{GDBN} can be configured to have a system-wide init file;
37244 this file will be read and executed at startup (@pxref{Startup, , What
37245 @value{GDBN} does during startup}).
37247 Here is the corresponding configure option:
37250 @item --with-system-gdbinit=@var{file}
37251 Specify that the default location of the system-wide init file is
37255 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37256 it may be subject to relocation. Two possible cases:
37260 If the default location of this init file contains @file{$prefix},
37261 it will be subject to relocation. Suppose that the configure options
37262 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37263 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37264 init file is looked for as @file{$install/etc/gdbinit} instead of
37265 @file{$prefix/etc/gdbinit}.
37268 By contrast, if the default location does not contain the prefix,
37269 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37270 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37271 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37272 wherever @value{GDBN} is installed.
37275 If the configured location of the system-wide init file (as given by the
37276 @option{--with-system-gdbinit} option at configure time) is in the
37277 data-directory (as specified by @option{--with-gdb-datadir} at configure
37278 time) or in one of its subdirectories, then @value{GDBN} will look for the
37279 system-wide init file in the directory specified by the
37280 @option{--data-directory} command-line option.
37281 Note that the system-wide init file is only read once, during @value{GDBN}
37282 initialization. If the data-directory is changed after @value{GDBN} has
37283 started with the @code{set data-directory} command, the file will not be
37287 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37290 @node System-wide Configuration Scripts
37291 @subsection Installed System-wide Configuration Scripts
37292 @cindex system-wide configuration scripts
37294 The @file{system-gdbinit} directory, located inside the data-directory
37295 (as specified by @option{--with-gdb-datadir} at configure time) contains
37296 a number of scripts which can be used as system-wide init files. To
37297 automatically source those scripts at startup, @value{GDBN} should be
37298 configured with @option{--with-system-gdbinit}. Otherwise, any user
37299 should be able to source them by hand as needed.
37301 The following scripts are currently available:
37304 @item @file{elinos.py}
37306 @cindex ELinOS system-wide configuration script
37307 This script is useful when debugging a program on an ELinOS target.
37308 It takes advantage of the environment variables defined in a standard
37309 ELinOS environment in order to determine the location of the system
37310 shared libraries, and then sets the @samp{solib-absolute-prefix}
37311 and @samp{solib-search-path} variables appropriately.
37313 @item @file{wrs-linux.py}
37314 @pindex wrs-linux.py
37315 @cindex Wind River Linux system-wide configuration script
37316 This script is useful when debugging a program on a target running
37317 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37318 the host-side sysroot used by the target system.
37322 @node Maintenance Commands
37323 @appendix Maintenance Commands
37324 @cindex maintenance commands
37325 @cindex internal commands
37327 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37328 includes a number of commands intended for @value{GDBN} developers,
37329 that are not documented elsewhere in this manual. These commands are
37330 provided here for reference. (For commands that turn on debugging
37331 messages, see @ref{Debugging Output}.)
37334 @kindex maint agent
37335 @kindex maint agent-eval
37336 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37337 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37338 Translate the given @var{expression} into remote agent bytecodes.
37339 This command is useful for debugging the Agent Expression mechanism
37340 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37341 expression useful for data collection, such as by tracepoints, while
37342 @samp{maint agent-eval} produces an expression that evaluates directly
37343 to a result. For instance, a collection expression for @code{globa +
37344 globb} will include bytecodes to record four bytes of memory at each
37345 of the addresses of @code{globa} and @code{globb}, while discarding
37346 the result of the addition, while an evaluation expression will do the
37347 addition and return the sum.
37348 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37349 If not, generate remote agent bytecode for current frame PC address.
37351 @kindex maint agent-printf
37352 @item maint agent-printf @var{format},@var{expr},...
37353 Translate the given format string and list of argument expressions
37354 into remote agent bytecodes and display them as a disassembled list.
37355 This command is useful for debugging the agent version of dynamic
37356 printf (@pxref{Dynamic Printf}).
37358 @kindex maint info breakpoints
37359 @item @anchor{maint info breakpoints}maint info breakpoints
37360 Using the same format as @samp{info breakpoints}, display both the
37361 breakpoints you've set explicitly, and those @value{GDBN} is using for
37362 internal purposes. Internal breakpoints are shown with negative
37363 breakpoint numbers. The type column identifies what kind of breakpoint
37368 Normal, explicitly set breakpoint.
37371 Normal, explicitly set watchpoint.
37374 Internal breakpoint, used to handle correctly stepping through
37375 @code{longjmp} calls.
37377 @item longjmp resume
37378 Internal breakpoint at the target of a @code{longjmp}.
37381 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37384 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37387 Shared library events.
37391 @kindex maint info bfds
37392 @item maint info bfds
37393 This prints information about each @code{bfd} object that is known to
37394 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37396 @kindex set displaced-stepping
37397 @kindex show displaced-stepping
37398 @cindex displaced stepping support
37399 @cindex out-of-line single-stepping
37400 @item set displaced-stepping
37401 @itemx show displaced-stepping
37402 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37403 if the target supports it. Displaced stepping is a way to single-step
37404 over breakpoints without removing them from the inferior, by executing
37405 an out-of-line copy of the instruction that was originally at the
37406 breakpoint location. It is also known as out-of-line single-stepping.
37409 @item set displaced-stepping on
37410 If the target architecture supports it, @value{GDBN} will use
37411 displaced stepping to step over breakpoints.
37413 @item set displaced-stepping off
37414 @value{GDBN} will not use displaced stepping to step over breakpoints,
37415 even if such is supported by the target architecture.
37417 @cindex non-stop mode, and @samp{set displaced-stepping}
37418 @item set displaced-stepping auto
37419 This is the default mode. @value{GDBN} will use displaced stepping
37420 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37421 architecture supports displaced stepping.
37424 @kindex maint check-psymtabs
37425 @item maint check-psymtabs
37426 Check the consistency of currently expanded psymtabs versus symtabs.
37427 Use this to check, for example, whether a symbol is in one but not the other.
37429 @kindex maint check-symtabs
37430 @item maint check-symtabs
37431 Check the consistency of currently expanded symtabs.
37433 @kindex maint expand-symtabs
37434 @item maint expand-symtabs [@var{regexp}]
37435 Expand symbol tables.
37436 If @var{regexp} is specified, only expand symbol tables for file
37437 names matching @var{regexp}.
37439 @kindex maint cplus first_component
37440 @item maint cplus first_component @var{name}
37441 Print the first C@t{++} class/namespace component of @var{name}.
37443 @kindex maint cplus namespace
37444 @item maint cplus namespace
37445 Print the list of possible C@t{++} namespaces.
37447 @kindex maint demangle
37448 @item maint demangle @var{name}
37449 Demangle a C@t{++} or Objective-C mangled @var{name}.
37451 @kindex maint deprecate
37452 @kindex maint undeprecate
37453 @cindex deprecated commands
37454 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37455 @itemx maint undeprecate @var{command}
37456 Deprecate or undeprecate the named @var{command}. Deprecated commands
37457 cause @value{GDBN} to issue a warning when you use them. The optional
37458 argument @var{replacement} says which newer command should be used in
37459 favor of the deprecated one; if it is given, @value{GDBN} will mention
37460 the replacement as part of the warning.
37462 @kindex maint dump-me
37463 @item maint dump-me
37464 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37465 Cause a fatal signal in the debugger and force it to dump its core.
37466 This is supported only on systems which support aborting a program
37467 with the @code{SIGQUIT} signal.
37469 @kindex maint internal-error
37470 @kindex maint internal-warning
37471 @item maint internal-error @r{[}@var{message-text}@r{]}
37472 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37473 Cause @value{GDBN} to call the internal function @code{internal_error}
37474 or @code{internal_warning} and hence behave as though an internal error
37475 or internal warning has been detected. In addition to reporting the
37476 internal problem, these functions give the user the opportunity to
37477 either quit @value{GDBN} or create a core file of the current
37478 @value{GDBN} session.
37480 These commands take an optional parameter @var{message-text} that is
37481 used as the text of the error or warning message.
37483 Here's an example of using @code{internal-error}:
37486 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37487 @dots{}/maint.c:121: internal-error: testing, 1, 2
37488 A problem internal to GDB has been detected. Further
37489 debugging may prove unreliable.
37490 Quit this debugging session? (y or n) @kbd{n}
37491 Create a core file? (y or n) @kbd{n}
37495 @cindex @value{GDBN} internal error
37496 @cindex internal errors, control of @value{GDBN} behavior
37498 @kindex maint set internal-error
37499 @kindex maint show internal-error
37500 @kindex maint set internal-warning
37501 @kindex maint show internal-warning
37502 @item maint set internal-error @var{action} [ask|yes|no]
37503 @itemx maint show internal-error @var{action}
37504 @itemx maint set internal-warning @var{action} [ask|yes|no]
37505 @itemx maint show internal-warning @var{action}
37506 When @value{GDBN} reports an internal problem (error or warning) it
37507 gives the user the opportunity to both quit @value{GDBN} and create a
37508 core file of the current @value{GDBN} session. These commands let you
37509 override the default behaviour for each particular @var{action},
37510 described in the table below.
37514 You can specify that @value{GDBN} should always (yes) or never (no)
37515 quit. The default is to ask the user what to do.
37518 You can specify that @value{GDBN} should always (yes) or never (no)
37519 create a core file. The default is to ask the user what to do.
37522 @kindex maint packet
37523 @item maint packet @var{text}
37524 If @value{GDBN} is talking to an inferior via the serial protocol,
37525 then this command sends the string @var{text} to the inferior, and
37526 displays the response packet. @value{GDBN} supplies the initial
37527 @samp{$} character, the terminating @samp{#} character, and the
37530 @kindex maint print architecture
37531 @item maint print architecture @r{[}@var{file}@r{]}
37532 Print the entire architecture configuration. The optional argument
37533 @var{file} names the file where the output goes.
37535 @kindex maint print c-tdesc
37536 @item maint print c-tdesc
37537 Print the current target description (@pxref{Target Descriptions}) as
37538 a C source file. The created source file can be used in @value{GDBN}
37539 when an XML parser is not available to parse the description.
37541 @kindex maint print dummy-frames
37542 @item maint print dummy-frames
37543 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37546 (@value{GDBP}) @kbd{b add}
37548 (@value{GDBP}) @kbd{print add(2,3)}
37549 Breakpoint 2, add (a=2, b=3) at @dots{}
37551 The program being debugged stopped while in a function called from GDB.
37553 (@value{GDBP}) @kbd{maint print dummy-frames}
37554 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37555 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37556 call_lo=0x01014000 call_hi=0x01014001
37560 Takes an optional file parameter.
37562 @kindex maint print registers
37563 @kindex maint print raw-registers
37564 @kindex maint print cooked-registers
37565 @kindex maint print register-groups
37566 @kindex maint print remote-registers
37567 @item maint print registers @r{[}@var{file}@r{]}
37568 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37569 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37570 @itemx maint print register-groups @r{[}@var{file}@r{]}
37571 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37572 Print @value{GDBN}'s internal register data structures.
37574 The command @code{maint print raw-registers} includes the contents of
37575 the raw register cache; the command @code{maint print
37576 cooked-registers} includes the (cooked) value of all registers,
37577 including registers which aren't available on the target nor visible
37578 to user; the command @code{maint print register-groups} includes the
37579 groups that each register is a member of; and the command @code{maint
37580 print remote-registers} includes the remote target's register numbers
37581 and offsets in the `G' packets.
37583 These commands take an optional parameter, a file name to which to
37584 write the information.
37586 @kindex maint print reggroups
37587 @item maint print reggroups @r{[}@var{file}@r{]}
37588 Print @value{GDBN}'s internal register group data structures. The
37589 optional argument @var{file} tells to what file to write the
37592 The register groups info looks like this:
37595 (@value{GDBP}) @kbd{maint print reggroups}
37608 This command forces @value{GDBN} to flush its internal register cache.
37610 @kindex maint print objfiles
37611 @cindex info for known object files
37612 @item maint print objfiles @r{[}@var{regexp}@r{]}
37613 Print a dump of all known object files.
37614 If @var{regexp} is specified, only print object files whose names
37615 match @var{regexp}. For each object file, this command prints its name,
37616 address in memory, and all of its psymtabs and symtabs.
37618 @kindex maint print section-scripts
37619 @cindex info for known .debug_gdb_scripts-loaded scripts
37620 @item maint print section-scripts [@var{regexp}]
37621 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37622 If @var{regexp} is specified, only print scripts loaded by object files
37623 matching @var{regexp}.
37624 For each script, this command prints its name as specified in the objfile,
37625 and the full path if known.
37626 @xref{dotdebug_gdb_scripts section}.
37628 @kindex maint print statistics
37629 @cindex bcache statistics
37630 @item maint print statistics
37631 This command prints, for each object file in the program, various data
37632 about that object file followed by the byte cache (@dfn{bcache})
37633 statistics for the object file. The objfile data includes the number
37634 of minimal, partial, full, and stabs symbols, the number of types
37635 defined by the objfile, the number of as yet unexpanded psym tables,
37636 the number of line tables and string tables, and the amount of memory
37637 used by the various tables. The bcache statistics include the counts,
37638 sizes, and counts of duplicates of all and unique objects, max,
37639 average, and median entry size, total memory used and its overhead and
37640 savings, and various measures of the hash table size and chain
37643 @kindex maint print target-stack
37644 @cindex target stack description
37645 @item maint print target-stack
37646 A @dfn{target} is an interface between the debugger and a particular
37647 kind of file or process. Targets can be stacked in @dfn{strata},
37648 so that more than one target can potentially respond to a request.
37649 In particular, memory accesses will walk down the stack of targets
37650 until they find a target that is interested in handling that particular
37653 This command prints a short description of each layer that was pushed on
37654 the @dfn{target stack}, starting from the top layer down to the bottom one.
37656 @kindex maint print type
37657 @cindex type chain of a data type
37658 @item maint print type @var{expr}
37659 Print the type chain for a type specified by @var{expr}. The argument
37660 can be either a type name or a symbol. If it is a symbol, the type of
37661 that symbol is described. The type chain produced by this command is
37662 a recursive definition of the data type as stored in @value{GDBN}'s
37663 data structures, including its flags and contained types.
37665 @kindex maint set dwarf2 always-disassemble
37666 @kindex maint show dwarf2 always-disassemble
37667 @item maint set dwarf2 always-disassemble
37668 @item maint show dwarf2 always-disassemble
37669 Control the behavior of @code{info address} when using DWARF debugging
37672 The default is @code{off}, which means that @value{GDBN} should try to
37673 describe a variable's location in an easily readable format. When
37674 @code{on}, @value{GDBN} will instead display the DWARF location
37675 expression in an assembly-like format. Note that some locations are
37676 too complex for @value{GDBN} to describe simply; in this case you will
37677 always see the disassembly form.
37679 Here is an example of the resulting disassembly:
37682 (gdb) info addr argc
37683 Symbol "argc" is a complex DWARF expression:
37687 For more information on these expressions, see
37688 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37690 @kindex maint set dwarf2 max-cache-age
37691 @kindex maint show dwarf2 max-cache-age
37692 @item maint set dwarf2 max-cache-age
37693 @itemx maint show dwarf2 max-cache-age
37694 Control the DWARF 2 compilation unit cache.
37696 @cindex DWARF 2 compilation units cache
37697 In object files with inter-compilation-unit references, such as those
37698 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37699 reader needs to frequently refer to previously read compilation units.
37700 This setting controls how long a compilation unit will remain in the
37701 cache if it is not referenced. A higher limit means that cached
37702 compilation units will be stored in memory longer, and more total
37703 memory will be used. Setting it to zero disables caching, which will
37704 slow down @value{GDBN} startup, but reduce memory consumption.
37706 @kindex maint set profile
37707 @kindex maint show profile
37708 @cindex profiling GDB
37709 @item maint set profile
37710 @itemx maint show profile
37711 Control profiling of @value{GDBN}.
37713 Profiling will be disabled until you use the @samp{maint set profile}
37714 command to enable it. When you enable profiling, the system will begin
37715 collecting timing and execution count data; when you disable profiling or
37716 exit @value{GDBN}, the results will be written to a log file. Remember that
37717 if you use profiling, @value{GDBN} will overwrite the profiling log file
37718 (often called @file{gmon.out}). If you have a record of important profiling
37719 data in a @file{gmon.out} file, be sure to move it to a safe location.
37721 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37722 compiled with the @samp{-pg} compiler option.
37724 @kindex maint set show-debug-regs
37725 @kindex maint show show-debug-regs
37726 @cindex hardware debug registers
37727 @item maint set show-debug-regs
37728 @itemx maint show show-debug-regs
37729 Control whether to show variables that mirror the hardware debug
37730 registers. Use @code{on} to enable, @code{off} to disable. If
37731 enabled, the debug registers values are shown when @value{GDBN} inserts or
37732 removes a hardware breakpoint or watchpoint, and when the inferior
37733 triggers a hardware-assisted breakpoint or watchpoint.
37735 @kindex maint set show-all-tib
37736 @kindex maint show show-all-tib
37737 @item maint set show-all-tib
37738 @itemx maint show show-all-tib
37739 Control whether to show all non zero areas within a 1k block starting
37740 at thread local base, when using the @samp{info w32 thread-information-block}
37743 @kindex maint set per-command
37744 @kindex maint show per-command
37745 @item maint set per-command
37746 @itemx maint show per-command
37747 @cindex resources used by commands
37749 @value{GDBN} can display the resources used by each command.
37750 This is useful in debugging performance problems.
37753 @item maint set per-command space [on|off]
37754 @itemx maint show per-command space
37755 Enable or disable the printing of the memory used by GDB for each command.
37756 If enabled, @value{GDBN} will display how much memory each command
37757 took, following the command's own output.
37758 This can also be requested by invoking @value{GDBN} with the
37759 @option{--statistics} command-line switch (@pxref{Mode Options}).
37761 @item maint set per-command time [on|off]
37762 @itemx maint show per-command time
37763 Enable or disable the printing of the execution time of @value{GDBN}
37765 If enabled, @value{GDBN} will display how much time it
37766 took to execute each command, following the command's own output.
37767 Both CPU time and wallclock time are printed.
37768 Printing both is useful when trying to determine whether the cost is
37769 CPU or, e.g., disk/network latency.
37770 Note that the CPU time printed is for @value{GDBN} only, it does not include
37771 the execution time of the inferior because there's no mechanism currently
37772 to compute how much time was spent by @value{GDBN} and how much time was
37773 spent by the program been debugged.
37774 This can also be requested by invoking @value{GDBN} with the
37775 @option{--statistics} command-line switch (@pxref{Mode Options}).
37777 @item maint set per-command symtab [on|off]
37778 @itemx maint show per-command symtab
37779 Enable or disable the printing of basic symbol table statistics
37781 If enabled, @value{GDBN} will display the following information:
37785 number of symbol tables
37787 number of primary symbol tables
37789 number of blocks in the blockvector
37793 @kindex maint space
37794 @cindex memory used by commands
37795 @item maint space @var{value}
37796 An alias for @code{maint set per-command space}.
37797 A non-zero value enables it, zero disables it.
37800 @cindex time of command execution
37801 @item maint time @var{value}
37802 An alias for @code{maint set per-command time}.
37803 A non-zero value enables it, zero disables it.
37805 @kindex maint translate-address
37806 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37807 Find the symbol stored at the location specified by the address
37808 @var{addr} and an optional section name @var{section}. If found,
37809 @value{GDBN} prints the name of the closest symbol and an offset from
37810 the symbol's location to the specified address. This is similar to
37811 the @code{info address} command (@pxref{Symbols}), except that this
37812 command also allows to find symbols in other sections.
37814 If section was not specified, the section in which the symbol was found
37815 is also printed. For dynamically linked executables, the name of
37816 executable or shared library containing the symbol is printed as well.
37820 The following command is useful for non-interactive invocations of
37821 @value{GDBN}, such as in the test suite.
37824 @item set watchdog @var{nsec}
37825 @kindex set watchdog
37826 @cindex watchdog timer
37827 @cindex timeout for commands
37828 Set the maximum number of seconds @value{GDBN} will wait for the
37829 target operation to finish. If this time expires, @value{GDBN}
37830 reports and error and the command is aborted.
37832 @item show watchdog
37833 Show the current setting of the target wait timeout.
37836 @node Remote Protocol
37837 @appendix @value{GDBN} Remote Serial Protocol
37842 * Stop Reply Packets::
37843 * General Query Packets::
37844 * Architecture-Specific Protocol Details::
37845 * Tracepoint Packets::
37846 * Host I/O Packets::
37848 * Notification Packets::
37849 * Remote Non-Stop::
37850 * Packet Acknowledgment::
37852 * File-I/O Remote Protocol Extension::
37853 * Library List Format::
37854 * Library List Format for SVR4 Targets::
37855 * Memory Map Format::
37856 * Thread List Format::
37857 * Traceframe Info Format::
37858 * Branch Trace Format::
37864 There may be occasions when you need to know something about the
37865 protocol---for example, if there is only one serial port to your target
37866 machine, you might want your program to do something special if it
37867 recognizes a packet meant for @value{GDBN}.
37869 In the examples below, @samp{->} and @samp{<-} are used to indicate
37870 transmitted and received data, respectively.
37872 @cindex protocol, @value{GDBN} remote serial
37873 @cindex serial protocol, @value{GDBN} remote
37874 @cindex remote serial protocol
37875 All @value{GDBN} commands and responses (other than acknowledgments
37876 and notifications, see @ref{Notification Packets}) are sent as a
37877 @var{packet}. A @var{packet} is introduced with the character
37878 @samp{$}, the actual @var{packet-data}, and the terminating character
37879 @samp{#} followed by a two-digit @var{checksum}:
37882 @code{$}@var{packet-data}@code{#}@var{checksum}
37886 @cindex checksum, for @value{GDBN} remote
37888 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37889 characters between the leading @samp{$} and the trailing @samp{#} (an
37890 eight bit unsigned checksum).
37892 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37893 specification also included an optional two-digit @var{sequence-id}:
37896 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37899 @cindex sequence-id, for @value{GDBN} remote
37901 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37902 has never output @var{sequence-id}s. Stubs that handle packets added
37903 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37905 When either the host or the target machine receives a packet, the first
37906 response expected is an acknowledgment: either @samp{+} (to indicate
37907 the package was received correctly) or @samp{-} (to request
37911 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37916 The @samp{+}/@samp{-} acknowledgments can be disabled
37917 once a connection is established.
37918 @xref{Packet Acknowledgment}, for details.
37920 The host (@value{GDBN}) sends @var{command}s, and the target (the
37921 debugging stub incorporated in your program) sends a @var{response}. In
37922 the case of step and continue @var{command}s, the response is only sent
37923 when the operation has completed, and the target has again stopped all
37924 threads in all attached processes. This is the default all-stop mode
37925 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37926 execution mode; see @ref{Remote Non-Stop}, for details.
37928 @var{packet-data} consists of a sequence of characters with the
37929 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37932 @cindex remote protocol, field separator
37933 Fields within the packet should be separated using @samp{,} @samp{;} or
37934 @samp{:}. Except where otherwise noted all numbers are represented in
37935 @sc{hex} with leading zeros suppressed.
37937 Implementors should note that prior to @value{GDBN} 5.0, the character
37938 @samp{:} could not appear as the third character in a packet (as it
37939 would potentially conflict with the @var{sequence-id}).
37941 @cindex remote protocol, binary data
37942 @anchor{Binary Data}
37943 Binary data in most packets is encoded either as two hexadecimal
37944 digits per byte of binary data. This allowed the traditional remote
37945 protocol to work over connections which were only seven-bit clean.
37946 Some packets designed more recently assume an eight-bit clean
37947 connection, and use a more efficient encoding to send and receive
37950 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37951 as an escape character. Any escaped byte is transmitted as the escape
37952 character followed by the original character XORed with @code{0x20}.
37953 For example, the byte @code{0x7d} would be transmitted as the two
37954 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37955 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37956 @samp{@}}) must always be escaped. Responses sent by the stub
37957 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37958 is not interpreted as the start of a run-length encoded sequence
37961 Response @var{data} can be run-length encoded to save space.
37962 Run-length encoding replaces runs of identical characters with one
37963 instance of the repeated character, followed by a @samp{*} and a
37964 repeat count. The repeat count is itself sent encoded, to avoid
37965 binary characters in @var{data}: a value of @var{n} is sent as
37966 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37967 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37968 code 32) for a repeat count of 3. (This is because run-length
37969 encoding starts to win for counts 3 or more.) Thus, for example,
37970 @samp{0* } is a run-length encoding of ``0000'': the space character
37971 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37974 The printable characters @samp{#} and @samp{$} or with a numeric value
37975 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37976 seven repeats (@samp{$}) can be expanded using a repeat count of only
37977 five (@samp{"}). For example, @samp{00000000} can be encoded as
37980 The error response returned for some packets includes a two character
37981 error number. That number is not well defined.
37983 @cindex empty response, for unsupported packets
37984 For any @var{command} not supported by the stub, an empty response
37985 (@samp{$#00}) should be returned. That way it is possible to extend the
37986 protocol. A newer @value{GDBN} can tell if a packet is supported based
37989 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37990 commands for register access, and the @samp{m} and @samp{M} commands
37991 for memory access. Stubs that only control single-threaded targets
37992 can implement run control with the @samp{c} (continue), and @samp{s}
37993 (step) commands. Stubs that support multi-threading targets should
37994 support the @samp{vCont} command. All other commands are optional.
37999 The following table provides a complete list of all currently defined
38000 @var{command}s and their corresponding response @var{data}.
38001 @xref{File-I/O Remote Protocol Extension}, for details about the File
38002 I/O extension of the remote protocol.
38004 Each packet's description has a template showing the packet's overall
38005 syntax, followed by an explanation of the packet's meaning. We
38006 include spaces in some of the templates for clarity; these are not
38007 part of the packet's syntax. No @value{GDBN} packet uses spaces to
38008 separate its components. For example, a template like @samp{foo
38009 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
38010 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
38011 @var{baz}. @value{GDBN} does not transmit a space character between the
38012 @samp{foo} and the @var{bar}, or between the @var{bar} and the
38015 @cindex @var{thread-id}, in remote protocol
38016 @anchor{thread-id syntax}
38017 Several packets and replies include a @var{thread-id} field to identify
38018 a thread. Normally these are positive numbers with a target-specific
38019 interpretation, formatted as big-endian hex strings. A @var{thread-id}
38020 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
38023 In addition, the remote protocol supports a multiprocess feature in
38024 which the @var{thread-id} syntax is extended to optionally include both
38025 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
38026 The @var{pid} (process) and @var{tid} (thread) components each have the
38027 format described above: a positive number with target-specific
38028 interpretation formatted as a big-endian hex string, literal @samp{-1}
38029 to indicate all processes or threads (respectively), or @samp{0} to
38030 indicate an arbitrary process or thread. Specifying just a process, as
38031 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
38032 error to specify all processes but a specific thread, such as
38033 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
38034 for those packets and replies explicitly documented to include a process
38035 ID, rather than a @var{thread-id}.
38037 The multiprocess @var{thread-id} syntax extensions are only used if both
38038 @value{GDBN} and the stub report support for the @samp{multiprocess}
38039 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
38042 Note that all packet forms beginning with an upper- or lower-case
38043 letter, other than those described here, are reserved for future use.
38045 Here are the packet descriptions.
38050 @cindex @samp{!} packet
38051 @anchor{extended mode}
38052 Enable extended mode. In extended mode, the remote server is made
38053 persistent. The @samp{R} packet is used to restart the program being
38059 The remote target both supports and has enabled extended mode.
38063 @cindex @samp{?} packet
38064 Indicate the reason the target halted. The reply is the same as for
38065 step and continue. This packet has a special interpretation when the
38066 target is in non-stop mode; see @ref{Remote Non-Stop}.
38069 @xref{Stop Reply Packets}, for the reply specifications.
38071 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
38072 @cindex @samp{A} packet
38073 Initialized @code{argv[]} array passed into program. @var{arglen}
38074 specifies the number of bytes in the hex encoded byte stream
38075 @var{arg}. See @code{gdbserver} for more details.
38080 The arguments were set.
38086 @cindex @samp{b} packet
38087 (Don't use this packet; its behavior is not well-defined.)
38088 Change the serial line speed to @var{baud}.
38090 JTC: @emph{When does the transport layer state change? When it's
38091 received, or after the ACK is transmitted. In either case, there are
38092 problems if the command or the acknowledgment packet is dropped.}
38094 Stan: @emph{If people really wanted to add something like this, and get
38095 it working for the first time, they ought to modify ser-unix.c to send
38096 some kind of out-of-band message to a specially-setup stub and have the
38097 switch happen "in between" packets, so that from remote protocol's point
38098 of view, nothing actually happened.}
38100 @item B @var{addr},@var{mode}
38101 @cindex @samp{B} packet
38102 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
38103 breakpoint at @var{addr}.
38105 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
38106 (@pxref{insert breakpoint or watchpoint packet}).
38108 @cindex @samp{bc} packet
38111 Backward continue. Execute the target system in reverse. No parameter.
38112 @xref{Reverse Execution}, for more information.
38115 @xref{Stop Reply Packets}, for the reply specifications.
38117 @cindex @samp{bs} packet
38120 Backward single step. Execute one instruction in reverse. No parameter.
38121 @xref{Reverse Execution}, for more information.
38124 @xref{Stop Reply Packets}, for the reply specifications.
38126 @item c @r{[}@var{addr}@r{]}
38127 @cindex @samp{c} packet
38128 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
38129 resume at current address.
38131 This packet is deprecated for multi-threading support. @xref{vCont
38135 @xref{Stop Reply Packets}, for the reply specifications.
38137 @item C @var{sig}@r{[};@var{addr}@r{]}
38138 @cindex @samp{C} packet
38139 Continue with signal @var{sig} (hex signal number). If
38140 @samp{;@var{addr}} is omitted, resume at same address.
38142 This packet is deprecated for multi-threading support. @xref{vCont
38146 @xref{Stop Reply Packets}, for the reply specifications.
38149 @cindex @samp{d} packet
38152 Don't use this packet; instead, define a general set packet
38153 (@pxref{General Query Packets}).
38157 @cindex @samp{D} packet
38158 The first form of the packet is used to detach @value{GDBN} from the
38159 remote system. It is sent to the remote target
38160 before @value{GDBN} disconnects via the @code{detach} command.
38162 The second form, including a process ID, is used when multiprocess
38163 protocol extensions are enabled (@pxref{multiprocess extensions}), to
38164 detach only a specific process. The @var{pid} is specified as a
38165 big-endian hex string.
38175 @item F @var{RC},@var{EE},@var{CF};@var{XX}
38176 @cindex @samp{F} packet
38177 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
38178 This is part of the File-I/O protocol extension. @xref{File-I/O
38179 Remote Protocol Extension}, for the specification.
38182 @anchor{read registers packet}
38183 @cindex @samp{g} packet
38184 Read general registers.
38188 @item @var{XX@dots{}}
38189 Each byte of register data is described by two hex digits. The bytes
38190 with the register are transmitted in target byte order. The size of
38191 each register and their position within the @samp{g} packet are
38192 determined by the @value{GDBN} internal gdbarch functions
38193 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
38194 specification of several standard @samp{g} packets is specified below.
38196 When reading registers from a trace frame (@pxref{Analyze Collected
38197 Data,,Using the Collected Data}), the stub may also return a string of
38198 literal @samp{x}'s in place of the register data digits, to indicate
38199 that the corresponding register has not been collected, thus its value
38200 is unavailable. For example, for an architecture with 4 registers of
38201 4 bytes each, the following reply indicates to @value{GDBN} that
38202 registers 0 and 2 have not been collected, while registers 1 and 3
38203 have been collected, and both have zero value:
38207 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38214 @item G @var{XX@dots{}}
38215 @cindex @samp{G} packet
38216 Write general registers. @xref{read registers packet}, for a
38217 description of the @var{XX@dots{}} data.
38227 @item H @var{op} @var{thread-id}
38228 @cindex @samp{H} packet
38229 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38230 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38231 it should be @samp{c} for step and continue operations (note that this
38232 is deprecated, supporting the @samp{vCont} command is a better
38233 option), @samp{g} for other operations. The thread designator
38234 @var{thread-id} has the format and interpretation described in
38235 @ref{thread-id syntax}.
38246 @c 'H': How restrictive (or permissive) is the thread model. If a
38247 @c thread is selected and stopped, are other threads allowed
38248 @c to continue to execute? As I mentioned above, I think the
38249 @c semantics of each command when a thread is selected must be
38250 @c described. For example:
38252 @c 'g': If the stub supports threads and a specific thread is
38253 @c selected, returns the register block from that thread;
38254 @c otherwise returns current registers.
38256 @c 'G' If the stub supports threads and a specific thread is
38257 @c selected, sets the registers of the register block of
38258 @c that thread; otherwise sets current registers.
38260 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38261 @anchor{cycle step packet}
38262 @cindex @samp{i} packet
38263 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38264 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38265 step starting at that address.
38268 @cindex @samp{I} packet
38269 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38273 @cindex @samp{k} packet
38276 FIXME: @emph{There is no description of how to operate when a specific
38277 thread context has been selected (i.e.@: does 'k' kill only that
38280 @item m @var{addr},@var{length}
38281 @cindex @samp{m} packet
38282 Read @var{length} bytes of memory starting at address @var{addr}.
38283 Note that @var{addr} may not be aligned to any particular boundary.
38285 The stub need not use any particular size or alignment when gathering
38286 data from memory for the response; even if @var{addr} is word-aligned
38287 and @var{length} is a multiple of the word size, the stub is free to
38288 use byte accesses, or not. For this reason, this packet may not be
38289 suitable for accessing memory-mapped I/O devices.
38290 @cindex alignment of remote memory accesses
38291 @cindex size of remote memory accesses
38292 @cindex memory, alignment and size of remote accesses
38296 @item @var{XX@dots{}}
38297 Memory contents; each byte is transmitted as a two-digit hexadecimal
38298 number. The reply may contain fewer bytes than requested if the
38299 server was able to read only part of the region of memory.
38304 @item M @var{addr},@var{length}:@var{XX@dots{}}
38305 @cindex @samp{M} packet
38306 Write @var{length} bytes of memory starting at address @var{addr}.
38307 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38308 hexadecimal number.
38315 for an error (this includes the case where only part of the data was
38320 @cindex @samp{p} packet
38321 Read the value of register @var{n}; @var{n} is in hex.
38322 @xref{read registers packet}, for a description of how the returned
38323 register value is encoded.
38327 @item @var{XX@dots{}}
38328 the register's value
38332 Indicating an unrecognized @var{query}.
38335 @item P @var{n@dots{}}=@var{r@dots{}}
38336 @anchor{write register packet}
38337 @cindex @samp{P} packet
38338 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38339 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38340 digits for each byte in the register (target byte order).
38350 @item q @var{name} @var{params}@dots{}
38351 @itemx Q @var{name} @var{params}@dots{}
38352 @cindex @samp{q} packet
38353 @cindex @samp{Q} packet
38354 General query (@samp{q}) and set (@samp{Q}). These packets are
38355 described fully in @ref{General Query Packets}.
38358 @cindex @samp{r} packet
38359 Reset the entire system.
38361 Don't use this packet; use the @samp{R} packet instead.
38364 @cindex @samp{R} packet
38365 Restart the program being debugged. @var{XX}, while needed, is ignored.
38366 This packet is only available in extended mode (@pxref{extended mode}).
38368 The @samp{R} packet has no reply.
38370 @item s @r{[}@var{addr}@r{]}
38371 @cindex @samp{s} packet
38372 Single step. @var{addr} is the address at which to resume. If
38373 @var{addr} is omitted, resume at same address.
38375 This packet is deprecated for multi-threading support. @xref{vCont
38379 @xref{Stop Reply Packets}, for the reply specifications.
38381 @item S @var{sig}@r{[};@var{addr}@r{]}
38382 @anchor{step with signal packet}
38383 @cindex @samp{S} packet
38384 Step with signal. This is analogous to the @samp{C} packet, but
38385 requests a single-step, rather than a normal resumption of execution.
38387 This packet is deprecated for multi-threading support. @xref{vCont
38391 @xref{Stop Reply Packets}, for the reply specifications.
38393 @item t @var{addr}:@var{PP},@var{MM}
38394 @cindex @samp{t} packet
38395 Search backwards starting at address @var{addr} for a match with pattern
38396 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38397 @var{addr} must be at least 3 digits.
38399 @item T @var{thread-id}
38400 @cindex @samp{T} packet
38401 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38406 thread is still alive
38412 Packets starting with @samp{v} are identified by a multi-letter name,
38413 up to the first @samp{;} or @samp{?} (or the end of the packet).
38415 @item vAttach;@var{pid}
38416 @cindex @samp{vAttach} packet
38417 Attach to a new process with the specified process ID @var{pid}.
38418 The process ID is a
38419 hexadecimal integer identifying the process. In all-stop mode, all
38420 threads in the attached process are stopped; in non-stop mode, it may be
38421 attached without being stopped if that is supported by the target.
38423 @c In non-stop mode, on a successful vAttach, the stub should set the
38424 @c current thread to a thread of the newly-attached process. After
38425 @c attaching, GDB queries for the attached process's thread ID with qC.
38426 @c Also note that, from a user perspective, whether or not the
38427 @c target is stopped on attach in non-stop mode depends on whether you
38428 @c use the foreground or background version of the attach command, not
38429 @c on what vAttach does; GDB does the right thing with respect to either
38430 @c stopping or restarting threads.
38432 This packet is only available in extended mode (@pxref{extended mode}).
38438 @item @r{Any stop packet}
38439 for success in all-stop mode (@pxref{Stop Reply Packets})
38441 for success in non-stop mode (@pxref{Remote Non-Stop})
38444 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38445 @cindex @samp{vCont} packet
38446 @anchor{vCont packet}
38447 Resume the inferior, specifying different actions for each thread.
38448 If an action is specified with no @var{thread-id}, then it is applied to any
38449 threads that don't have a specific action specified; if no default action is
38450 specified then other threads should remain stopped in all-stop mode and
38451 in their current state in non-stop mode.
38452 Specifying multiple
38453 default actions is an error; specifying no actions is also an error.
38454 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38456 Currently supported actions are:
38462 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38466 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38469 @item r @var{start},@var{end}
38470 Step once, and then keep stepping as long as the thread stops at
38471 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38472 The remote stub reports a stop reply when either the thread goes out
38473 of the range or is stopped due to an unrelated reason, such as hitting
38474 a breakpoint. @xref{range stepping}.
38476 If the range is empty (@var{start} == @var{end}), then the action
38477 becomes equivalent to the @samp{s} action. In other words,
38478 single-step once, and report the stop (even if the stepped instruction
38479 jumps to @var{start}).
38481 (A stop reply may be sent at any point even if the PC is still within
38482 the stepping range; for example, it is valid to implement this packet
38483 in a degenerate way as a single instruction step operation.)
38487 The optional argument @var{addr} normally associated with the
38488 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38489 not supported in @samp{vCont}.
38491 The @samp{t} action is only relevant in non-stop mode
38492 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38493 A stop reply should be generated for any affected thread not already stopped.
38494 When a thread is stopped by means of a @samp{t} action,
38495 the corresponding stop reply should indicate that the thread has stopped with
38496 signal @samp{0}, regardless of whether the target uses some other signal
38497 as an implementation detail.
38499 The stub must support @samp{vCont} if it reports support for
38500 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38501 this case @samp{vCont} actions can be specified to apply to all threads
38502 in a process by using the @samp{p@var{pid}.-1} form of the
38506 @xref{Stop Reply Packets}, for the reply specifications.
38509 @cindex @samp{vCont?} packet
38510 Request a list of actions supported by the @samp{vCont} packet.
38514 @item vCont@r{[};@var{action}@dots{}@r{]}
38515 The @samp{vCont} packet is supported. Each @var{action} is a supported
38516 command in the @samp{vCont} packet.
38518 The @samp{vCont} packet is not supported.
38521 @item vFile:@var{operation}:@var{parameter}@dots{}
38522 @cindex @samp{vFile} packet
38523 Perform a file operation on the target system. For details,
38524 see @ref{Host I/O Packets}.
38526 @item vFlashErase:@var{addr},@var{length}
38527 @cindex @samp{vFlashErase} packet
38528 Direct the stub to erase @var{length} bytes of flash starting at
38529 @var{addr}. The region may enclose any number of flash blocks, but
38530 its start and end must fall on block boundaries, as indicated by the
38531 flash block size appearing in the memory map (@pxref{Memory Map
38532 Format}). @value{GDBN} groups flash memory programming operations
38533 together, and sends a @samp{vFlashDone} request after each group; the
38534 stub is allowed to delay erase operation until the @samp{vFlashDone}
38535 packet is received.
38545 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38546 @cindex @samp{vFlashWrite} packet
38547 Direct the stub to write data to flash address @var{addr}. The data
38548 is passed in binary form using the same encoding as for the @samp{X}
38549 packet (@pxref{Binary Data}). The memory ranges specified by
38550 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38551 not overlap, and must appear in order of increasing addresses
38552 (although @samp{vFlashErase} packets for higher addresses may already
38553 have been received; the ordering is guaranteed only between
38554 @samp{vFlashWrite} packets). If a packet writes to an address that was
38555 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38556 target-specific method, the results are unpredictable.
38564 for vFlashWrite addressing non-flash memory
38570 @cindex @samp{vFlashDone} packet
38571 Indicate to the stub that flash programming operation is finished.
38572 The stub is permitted to delay or batch the effects of a group of
38573 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38574 @samp{vFlashDone} packet is received. The contents of the affected
38575 regions of flash memory are unpredictable until the @samp{vFlashDone}
38576 request is completed.
38578 @item vKill;@var{pid}
38579 @cindex @samp{vKill} packet
38580 Kill the process with the specified process ID. @var{pid} is a
38581 hexadecimal integer identifying the process. This packet is used in
38582 preference to @samp{k} when multiprocess protocol extensions are
38583 supported; see @ref{multiprocess extensions}.
38593 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38594 @cindex @samp{vRun} packet
38595 Run the program @var{filename}, passing it each @var{argument} on its
38596 command line. The file and arguments are hex-encoded strings. If
38597 @var{filename} is an empty string, the stub may use a default program
38598 (e.g.@: the last program run). The program is created in the stopped
38601 @c FIXME: What about non-stop mode?
38603 This packet is only available in extended mode (@pxref{extended mode}).
38609 @item @r{Any stop packet}
38610 for success (@pxref{Stop Reply Packets})
38614 @cindex @samp{vStopped} packet
38615 @xref{Notification Packets}.
38617 @item X @var{addr},@var{length}:@var{XX@dots{}}
38619 @cindex @samp{X} packet
38620 Write data to memory, where the data is transmitted in binary.
38621 @var{addr} is address, @var{length} is number of bytes,
38622 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38632 @item z @var{type},@var{addr},@var{kind}
38633 @itemx Z @var{type},@var{addr},@var{kind}
38634 @anchor{insert breakpoint or watchpoint packet}
38635 @cindex @samp{z} packet
38636 @cindex @samp{Z} packets
38637 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38638 watchpoint starting at address @var{address} of kind @var{kind}.
38640 Each breakpoint and watchpoint packet @var{type} is documented
38643 @emph{Implementation notes: A remote target shall return an empty string
38644 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38645 remote target shall support either both or neither of a given
38646 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38647 avoid potential problems with duplicate packets, the operations should
38648 be implemented in an idempotent way.}
38650 @item z0,@var{addr},@var{kind}
38651 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38652 @cindex @samp{z0} packet
38653 @cindex @samp{Z0} packet
38654 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38655 @var{addr} of type @var{kind}.
38657 A memory breakpoint is implemented by replacing the instruction at
38658 @var{addr} with a software breakpoint or trap instruction. The
38659 @var{kind} is target-specific and typically indicates the size of
38660 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38661 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38662 architectures have additional meanings for @var{kind};
38663 @var{cond_list} is an optional list of conditional expressions in bytecode
38664 form that should be evaluated on the target's side. These are the
38665 conditions that should be taken into consideration when deciding if
38666 the breakpoint trigger should be reported back to @var{GDBN}.
38668 The @var{cond_list} parameter is comprised of a series of expressions,
38669 concatenated without separators. Each expression has the following form:
38673 @item X @var{len},@var{expr}
38674 @var{len} is the length of the bytecode expression and @var{expr} is the
38675 actual conditional expression in bytecode form.
38679 The optional @var{cmd_list} parameter introduces commands that may be
38680 run on the target, rather than being reported back to @value{GDBN}.
38681 The parameter starts with a numeric flag @var{persist}; if the flag is
38682 nonzero, then the breakpoint may remain active and the commands
38683 continue to be run even when @value{GDBN} disconnects from the target.
38684 Following this flag is a series of expressions concatenated with no
38685 separators. Each expression has the following form:
38689 @item X @var{len},@var{expr}
38690 @var{len} is the length of the bytecode expression and @var{expr} is the
38691 actual conditional expression in bytecode form.
38695 see @ref{Architecture-Specific Protocol Details}.
38697 @emph{Implementation note: It is possible for a target to copy or move
38698 code that contains memory breakpoints (e.g., when implementing
38699 overlays). The behavior of this packet, in the presence of such a
38700 target, is not defined.}
38712 @item z1,@var{addr},@var{kind}
38713 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38714 @cindex @samp{z1} packet
38715 @cindex @samp{Z1} packet
38716 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38717 address @var{addr}.
38719 A hardware breakpoint is implemented using a mechanism that is not
38720 dependant on being able to modify the target's memory. @var{kind}
38721 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38723 @emph{Implementation note: A hardware breakpoint is not affected by code
38736 @item z2,@var{addr},@var{kind}
38737 @itemx Z2,@var{addr},@var{kind}
38738 @cindex @samp{z2} packet
38739 @cindex @samp{Z2} packet
38740 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38741 @var{kind} is interpreted as the number of bytes to watch.
38753 @item z3,@var{addr},@var{kind}
38754 @itemx Z3,@var{addr},@var{kind}
38755 @cindex @samp{z3} packet
38756 @cindex @samp{Z3} packet
38757 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38758 @var{kind} is interpreted as the number of bytes to watch.
38770 @item z4,@var{addr},@var{kind}
38771 @itemx Z4,@var{addr},@var{kind}
38772 @cindex @samp{z4} packet
38773 @cindex @samp{Z4} packet
38774 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38775 @var{kind} is interpreted as the number of bytes to watch.
38789 @node Stop Reply Packets
38790 @section Stop Reply Packets
38791 @cindex stop reply packets
38793 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38794 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38795 receive any of the below as a reply. Except for @samp{?}
38796 and @samp{vStopped}, that reply is only returned
38797 when the target halts. In the below the exact meaning of @dfn{signal
38798 number} is defined by the header @file{include/gdb/signals.h} in the
38799 @value{GDBN} source code.
38801 As in the description of request packets, we include spaces in the
38802 reply templates for clarity; these are not part of the reply packet's
38803 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38809 The program received signal number @var{AA} (a two-digit hexadecimal
38810 number). This is equivalent to a @samp{T} response with no
38811 @var{n}:@var{r} pairs.
38813 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38814 @cindex @samp{T} packet reply
38815 The program received signal number @var{AA} (a two-digit hexadecimal
38816 number). This is equivalent to an @samp{S} response, except that the
38817 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38818 and other information directly in the stop reply packet, reducing
38819 round-trip latency. Single-step and breakpoint traps are reported
38820 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38824 If @var{n} is a hexadecimal number, it is a register number, and the
38825 corresponding @var{r} gives that register's value. @var{r} is a
38826 series of bytes in target byte order, with each byte given by a
38827 two-digit hex number.
38830 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38831 the stopped thread, as specified in @ref{thread-id syntax}.
38834 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38835 the core on which the stop event was detected.
38838 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38839 specific event that stopped the target. The currently defined stop
38840 reasons are listed below. @var{aa} should be @samp{05}, the trap
38841 signal. At most one stop reason should be present.
38844 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38845 and go on to the next; this allows us to extend the protocol in the
38849 The currently defined stop reasons are:
38855 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38858 @cindex shared library events, remote reply
38860 The packet indicates that the loaded libraries have changed.
38861 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38862 list of loaded libraries. @var{r} is ignored.
38864 @cindex replay log events, remote reply
38866 The packet indicates that the target cannot continue replaying
38867 logged execution events, because it has reached the end (or the
38868 beginning when executing backward) of the log. The value of @var{r}
38869 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38870 for more information.
38874 @itemx W @var{AA} ; process:@var{pid}
38875 The process exited, and @var{AA} is the exit status. This is only
38876 applicable to certain targets.
38878 The second form of the response, including the process ID of the exited
38879 process, can be used only when @value{GDBN} has reported support for
38880 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38881 The @var{pid} is formatted as a big-endian hex string.
38884 @itemx X @var{AA} ; process:@var{pid}
38885 The process terminated with signal @var{AA}.
38887 The second form of the response, including the process ID of the
38888 terminated process, can be used only when @value{GDBN} has reported
38889 support for multiprocess protocol extensions; see @ref{multiprocess
38890 extensions}. The @var{pid} is formatted as a big-endian hex string.
38892 @item O @var{XX}@dots{}
38893 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38894 written as the program's console output. This can happen at any time
38895 while the program is running and the debugger should continue to wait
38896 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38898 @item F @var{call-id},@var{parameter}@dots{}
38899 @var{call-id} is the identifier which says which host system call should
38900 be called. This is just the name of the function. Translation into the
38901 correct system call is only applicable as it's defined in @value{GDBN}.
38902 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38905 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38906 this very system call.
38908 The target replies with this packet when it expects @value{GDBN} to
38909 call a host system call on behalf of the target. @value{GDBN} replies
38910 with an appropriate @samp{F} packet and keeps up waiting for the next
38911 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38912 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38913 Protocol Extension}, for more details.
38917 @node General Query Packets
38918 @section General Query Packets
38919 @cindex remote query requests
38921 Packets starting with @samp{q} are @dfn{general query packets};
38922 packets starting with @samp{Q} are @dfn{general set packets}. General
38923 query and set packets are a semi-unified form for retrieving and
38924 sending information to and from the stub.
38926 The initial letter of a query or set packet is followed by a name
38927 indicating what sort of thing the packet applies to. For example,
38928 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38929 definitions with the stub. These packet names follow some
38934 The name must not contain commas, colons or semicolons.
38936 Most @value{GDBN} query and set packets have a leading upper case
38939 The names of custom vendor packets should use a company prefix, in
38940 lower case, followed by a period. For example, packets designed at
38941 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38942 foos) or @samp{Qacme.bar} (for setting bars).
38945 The name of a query or set packet should be separated from any
38946 parameters by a @samp{:}; the parameters themselves should be
38947 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38948 full packet name, and check for a separator or the end of the packet,
38949 in case two packet names share a common prefix. New packets should not begin
38950 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38951 packets predate these conventions, and have arguments without any terminator
38952 for the packet name; we suspect they are in widespread use in places that
38953 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38954 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38957 Like the descriptions of the other packets, each description here
38958 has a template showing the packet's overall syntax, followed by an
38959 explanation of the packet's meaning. We include spaces in some of the
38960 templates for clarity; these are not part of the packet's syntax. No
38961 @value{GDBN} packet uses spaces to separate its components.
38963 Here are the currently defined query and set packets:
38969 Turn on or off the agent as a helper to perform some debugging operations
38970 delegated from @value{GDBN} (@pxref{Control Agent}).
38972 @item QAllow:@var{op}:@var{val}@dots{}
38973 @cindex @samp{QAllow} packet
38974 Specify which operations @value{GDBN} expects to request of the
38975 target, as a semicolon-separated list of operation name and value
38976 pairs. Possible values for @var{op} include @samp{WriteReg},
38977 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38978 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38979 indicating that @value{GDBN} will not request the operation, or 1,
38980 indicating that it may. (The target can then use this to set up its
38981 own internals optimally, for instance if the debugger never expects to
38982 insert breakpoints, it may not need to install its own trap handler.)
38985 @cindex current thread, remote request
38986 @cindex @samp{qC} packet
38987 Return the current thread ID.
38991 @item QC @var{thread-id}
38992 Where @var{thread-id} is a thread ID as documented in
38993 @ref{thread-id syntax}.
38994 @item @r{(anything else)}
38995 Any other reply implies the old thread ID.
38998 @item qCRC:@var{addr},@var{length}
38999 @cindex CRC of memory block, remote request
39000 @cindex @samp{qCRC} packet
39001 Compute the CRC checksum of a block of memory using CRC-32 defined in
39002 IEEE 802.3. The CRC is computed byte at a time, taking the most
39003 significant bit of each byte first. The initial pattern code
39004 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
39006 @emph{Note:} This is the same CRC used in validating separate debug
39007 files (@pxref{Separate Debug Files, , Debugging Information in Separate
39008 Files}). However the algorithm is slightly different. When validating
39009 separate debug files, the CRC is computed taking the @emph{least}
39010 significant bit of each byte first, and the final result is inverted to
39011 detect trailing zeros.
39016 An error (such as memory fault)
39017 @item C @var{crc32}
39018 The specified memory region's checksum is @var{crc32}.
39021 @item QDisableRandomization:@var{value}
39022 @cindex disable address space randomization, remote request
39023 @cindex @samp{QDisableRandomization} packet
39024 Some target operating systems will randomize the virtual address space
39025 of the inferior process as a security feature, but provide a feature
39026 to disable such randomization, e.g.@: to allow for a more deterministic
39027 debugging experience. On such systems, this packet with a @var{value}
39028 of 1 directs the target to disable address space randomization for
39029 processes subsequently started via @samp{vRun} packets, while a packet
39030 with a @var{value} of 0 tells the target to enable address space
39033 This packet is only available in extended mode (@pxref{extended mode}).
39038 The request succeeded.
39041 An error occurred. @var{nn} are hex digits.
39044 An empty reply indicates that @samp{QDisableRandomization} is not supported
39048 This packet is not probed by default; the remote stub must request it,
39049 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39050 This should only be done on targets that actually support disabling
39051 address space randomization.
39054 @itemx qsThreadInfo
39055 @cindex list active threads, remote request
39056 @cindex @samp{qfThreadInfo} packet
39057 @cindex @samp{qsThreadInfo} packet
39058 Obtain a list of all active thread IDs from the target (OS). Since there
39059 may be too many active threads to fit into one reply packet, this query
39060 works iteratively: it may require more than one query/reply sequence to
39061 obtain the entire list of threads. The first query of the sequence will
39062 be the @samp{qfThreadInfo} query; subsequent queries in the
39063 sequence will be the @samp{qsThreadInfo} query.
39065 NOTE: This packet replaces the @samp{qL} query (see below).
39069 @item m @var{thread-id}
39071 @item m @var{thread-id},@var{thread-id}@dots{}
39072 a comma-separated list of thread IDs
39074 (lower case letter @samp{L}) denotes end of list.
39077 In response to each query, the target will reply with a list of one or
39078 more thread IDs, separated by commas.
39079 @value{GDBN} will respond to each reply with a request for more thread
39080 ids (using the @samp{qs} form of the query), until the target responds
39081 with @samp{l} (lower-case ell, for @dfn{last}).
39082 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
39085 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
39086 @cindex get thread-local storage address, remote request
39087 @cindex @samp{qGetTLSAddr} packet
39088 Fetch the address associated with thread local storage specified
39089 by @var{thread-id}, @var{offset}, and @var{lm}.
39091 @var{thread-id} is the thread ID associated with the
39092 thread for which to fetch the TLS address. @xref{thread-id syntax}.
39094 @var{offset} is the (big endian, hex encoded) offset associated with the
39095 thread local variable. (This offset is obtained from the debug
39096 information associated with the variable.)
39098 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
39099 load module associated with the thread local storage. For example,
39100 a @sc{gnu}/Linux system will pass the link map address of the shared
39101 object associated with the thread local storage under consideration.
39102 Other operating environments may choose to represent the load module
39103 differently, so the precise meaning of this parameter will vary.
39107 @item @var{XX}@dots{}
39108 Hex encoded (big endian) bytes representing the address of the thread
39109 local storage requested.
39112 An error occurred. @var{nn} are hex digits.
39115 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
39118 @item qGetTIBAddr:@var{thread-id}
39119 @cindex get thread information block address
39120 @cindex @samp{qGetTIBAddr} packet
39121 Fetch address of the Windows OS specific Thread Information Block.
39123 @var{thread-id} is the thread ID associated with the thread.
39127 @item @var{XX}@dots{}
39128 Hex encoded (big endian) bytes representing the linear address of the
39129 thread information block.
39132 An error occured. This means that either the thread was not found, or the
39133 address could not be retrieved.
39136 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
39139 @item qL @var{startflag} @var{threadcount} @var{nextthread}
39140 Obtain thread information from RTOS. Where: @var{startflag} (one hex
39141 digit) is one to indicate the first query and zero to indicate a
39142 subsequent query; @var{threadcount} (two hex digits) is the maximum
39143 number of threads the response packet can contain; and @var{nextthread}
39144 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
39145 returned in the response as @var{argthread}.
39147 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
39151 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
39152 Where: @var{count} (two hex digits) is the number of threads being
39153 returned; @var{done} (one hex digit) is zero to indicate more threads
39154 and one indicates no further threads; @var{argthreadid} (eight hex
39155 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
39156 is a sequence of thread IDs from the target. @var{threadid} (eight hex
39157 digits). See @code{remote.c:parse_threadlist_response()}.
39161 @cindex section offsets, remote request
39162 @cindex @samp{qOffsets} packet
39163 Get section offsets that the target used when relocating the downloaded
39168 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
39169 Relocate the @code{Text} section by @var{xxx} from its original address.
39170 Relocate the @code{Data} section by @var{yyy} from its original address.
39171 If the object file format provides segment information (e.g.@: @sc{elf}
39172 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
39173 segments by the supplied offsets.
39175 @emph{Note: while a @code{Bss} offset may be included in the response,
39176 @value{GDBN} ignores this and instead applies the @code{Data} offset
39177 to the @code{Bss} section.}
39179 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
39180 Relocate the first segment of the object file, which conventionally
39181 contains program code, to a starting address of @var{xxx}. If
39182 @samp{DataSeg} is specified, relocate the second segment, which
39183 conventionally contains modifiable data, to a starting address of
39184 @var{yyy}. @value{GDBN} will report an error if the object file
39185 does not contain segment information, or does not contain at least
39186 as many segments as mentioned in the reply. Extra segments are
39187 kept at fixed offsets relative to the last relocated segment.
39190 @item qP @var{mode} @var{thread-id}
39191 @cindex thread information, remote request
39192 @cindex @samp{qP} packet
39193 Returns information on @var{thread-id}. Where: @var{mode} is a hex
39194 encoded 32 bit mode; @var{thread-id} is a thread ID
39195 (@pxref{thread-id syntax}).
39197 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
39200 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39204 @cindex non-stop mode, remote request
39205 @cindex @samp{QNonStop} packet
39207 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39208 @xref{Remote Non-Stop}, for more information.
39213 The request succeeded.
39216 An error occurred. @var{nn} are hex digits.
39219 An empty reply indicates that @samp{QNonStop} is not supported by
39223 This packet is not probed by default; the remote stub must request it,
39224 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39225 Use of this packet is controlled by the @code{set non-stop} command;
39226 @pxref{Non-Stop Mode}.
39228 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39229 @cindex pass signals to inferior, remote request
39230 @cindex @samp{QPassSignals} packet
39231 @anchor{QPassSignals}
39232 Each listed @var{signal} should be passed directly to the inferior process.
39233 Signals are numbered identically to continue packets and stop replies
39234 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39235 strictly greater than the previous item. These signals do not need to stop
39236 the inferior, or be reported to @value{GDBN}. All other signals should be
39237 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39238 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39239 new list. This packet improves performance when using @samp{handle
39240 @var{signal} nostop noprint pass}.
39245 The request succeeded.
39248 An error occurred. @var{nn} are hex digits.
39251 An empty reply indicates that @samp{QPassSignals} is not supported by
39255 Use of this packet is controlled by the @code{set remote pass-signals}
39256 command (@pxref{Remote Configuration, set remote pass-signals}).
39257 This packet is not probed by default; the remote stub must request it,
39258 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39260 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39261 @cindex signals the inferior may see, remote request
39262 @cindex @samp{QProgramSignals} packet
39263 @anchor{QProgramSignals}
39264 Each listed @var{signal} may be delivered to the inferior process.
39265 Others should be silently discarded.
39267 In some cases, the remote stub may need to decide whether to deliver a
39268 signal to the program or not without @value{GDBN} involvement. One
39269 example of that is while detaching --- the program's threads may have
39270 stopped for signals that haven't yet had a chance of being reported to
39271 @value{GDBN}, and so the remote stub can use the signal list specified
39272 by this packet to know whether to deliver or ignore those pending
39275 This does not influence whether to deliver a signal as requested by a
39276 resumption packet (@pxref{vCont packet}).
39278 Signals are numbered identically to continue packets and stop replies
39279 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39280 strictly greater than the previous item. Multiple
39281 @samp{QProgramSignals} packets do not combine; any earlier
39282 @samp{QProgramSignals} list is completely replaced by the new list.
39287 The request succeeded.
39290 An error occurred. @var{nn} are hex digits.
39293 An empty reply indicates that @samp{QProgramSignals} is not supported
39297 Use of this packet is controlled by the @code{set remote program-signals}
39298 command (@pxref{Remote Configuration, set remote program-signals}).
39299 This packet is not probed by default; the remote stub must request it,
39300 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39302 @item qRcmd,@var{command}
39303 @cindex execute remote command, remote request
39304 @cindex @samp{qRcmd} packet
39305 @var{command} (hex encoded) is passed to the local interpreter for
39306 execution. Invalid commands should be reported using the output
39307 string. Before the final result packet, the target may also respond
39308 with a number of intermediate @samp{O@var{output}} console output
39309 packets. @emph{Implementors should note that providing access to a
39310 stubs's interpreter may have security implications}.
39315 A command response with no output.
39317 A command response with the hex encoded output string @var{OUTPUT}.
39319 Indicate a badly formed request.
39321 An empty reply indicates that @samp{qRcmd} is not recognized.
39324 (Note that the @code{qRcmd} packet's name is separated from the
39325 command by a @samp{,}, not a @samp{:}, contrary to the naming
39326 conventions above. Please don't use this packet as a model for new
39329 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39330 @cindex searching memory, in remote debugging
39332 @cindex @samp{qSearch:memory} packet
39334 @cindex @samp{qSearch memory} packet
39335 @anchor{qSearch memory}
39336 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39337 @var{address} and @var{length} are encoded in hex.
39338 @var{search-pattern} is a sequence of bytes, hex encoded.
39343 The pattern was not found.
39345 The pattern was found at @var{address}.
39347 A badly formed request or an error was encountered while searching memory.
39349 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39352 @item QStartNoAckMode
39353 @cindex @samp{QStartNoAckMode} packet
39354 @anchor{QStartNoAckMode}
39355 Request that the remote stub disable the normal @samp{+}/@samp{-}
39356 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39361 The stub has switched to no-acknowledgment mode.
39362 @value{GDBN} acknowledges this reponse,
39363 but neither the stub nor @value{GDBN} shall send or expect further
39364 @samp{+}/@samp{-} acknowledgments in the current connection.
39366 An empty reply indicates that the stub does not support no-acknowledgment mode.
39369 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39370 @cindex supported packets, remote query
39371 @cindex features of the remote protocol
39372 @cindex @samp{qSupported} packet
39373 @anchor{qSupported}
39374 Tell the remote stub about features supported by @value{GDBN}, and
39375 query the stub for features it supports. This packet allows
39376 @value{GDBN} and the remote stub to take advantage of each others'
39377 features. @samp{qSupported} also consolidates multiple feature probes
39378 at startup, to improve @value{GDBN} performance---a single larger
39379 packet performs better than multiple smaller probe packets on
39380 high-latency links. Some features may enable behavior which must not
39381 be on by default, e.g.@: because it would confuse older clients or
39382 stubs. Other features may describe packets which could be
39383 automatically probed for, but are not. These features must be
39384 reported before @value{GDBN} will use them. This ``default
39385 unsupported'' behavior is not appropriate for all packets, but it
39386 helps to keep the initial connection time under control with new
39387 versions of @value{GDBN} which support increasing numbers of packets.
39391 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39392 The stub supports or does not support each returned @var{stubfeature},
39393 depending on the form of each @var{stubfeature} (see below for the
39396 An empty reply indicates that @samp{qSupported} is not recognized,
39397 or that no features needed to be reported to @value{GDBN}.
39400 The allowed forms for each feature (either a @var{gdbfeature} in the
39401 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39405 @item @var{name}=@var{value}
39406 The remote protocol feature @var{name} is supported, and associated
39407 with the specified @var{value}. The format of @var{value} depends
39408 on the feature, but it must not include a semicolon.
39410 The remote protocol feature @var{name} is supported, and does not
39411 need an associated value.
39413 The remote protocol feature @var{name} is not supported.
39415 The remote protocol feature @var{name} may be supported, and
39416 @value{GDBN} should auto-detect support in some other way when it is
39417 needed. This form will not be used for @var{gdbfeature} notifications,
39418 but may be used for @var{stubfeature} responses.
39421 Whenever the stub receives a @samp{qSupported} request, the
39422 supplied set of @value{GDBN} features should override any previous
39423 request. This allows @value{GDBN} to put the stub in a known
39424 state, even if the stub had previously been communicating with
39425 a different version of @value{GDBN}.
39427 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39432 This feature indicates whether @value{GDBN} supports multiprocess
39433 extensions to the remote protocol. @value{GDBN} does not use such
39434 extensions unless the stub also reports that it supports them by
39435 including @samp{multiprocess+} in its @samp{qSupported} reply.
39436 @xref{multiprocess extensions}, for details.
39439 This feature indicates that @value{GDBN} supports the XML target
39440 description. If the stub sees @samp{xmlRegisters=} with target
39441 specific strings separated by a comma, it will report register
39445 This feature indicates whether @value{GDBN} supports the
39446 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39447 instruction reply packet}).
39450 Stubs should ignore any unknown values for
39451 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39452 packet supports receiving packets of unlimited length (earlier
39453 versions of @value{GDBN} may reject overly long responses). Additional values
39454 for @var{gdbfeature} may be defined in the future to let the stub take
39455 advantage of new features in @value{GDBN}, e.g.@: incompatible
39456 improvements in the remote protocol---the @samp{multiprocess} feature is
39457 an example of such a feature. The stub's reply should be independent
39458 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39459 describes all the features it supports, and then the stub replies with
39460 all the features it supports.
39462 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39463 responses, as long as each response uses one of the standard forms.
39465 Some features are flags. A stub which supports a flag feature
39466 should respond with a @samp{+} form response. Other features
39467 require values, and the stub should respond with an @samp{=}
39470 Each feature has a default value, which @value{GDBN} will use if
39471 @samp{qSupported} is not available or if the feature is not mentioned
39472 in the @samp{qSupported} response. The default values are fixed; a
39473 stub is free to omit any feature responses that match the defaults.
39475 Not all features can be probed, but for those which can, the probing
39476 mechanism is useful: in some cases, a stub's internal
39477 architecture may not allow the protocol layer to know some information
39478 about the underlying target in advance. This is especially common in
39479 stubs which may be configured for multiple targets.
39481 These are the currently defined stub features and their properties:
39483 @multitable @columnfractions 0.35 0.2 0.12 0.2
39484 @c NOTE: The first row should be @headitem, but we do not yet require
39485 @c a new enough version of Texinfo (4.7) to use @headitem.
39487 @tab Value Required
39491 @item @samp{PacketSize}
39496 @item @samp{qXfer:auxv:read}
39501 @item @samp{qXfer:btrace:read}
39506 @item @samp{qXfer:features:read}
39511 @item @samp{qXfer:libraries:read}
39516 @item @samp{qXfer:libraries-svr4:read}
39521 @item @samp{augmented-libraries-svr4-read}
39526 @item @samp{qXfer:memory-map:read}
39531 @item @samp{qXfer:sdata:read}
39536 @item @samp{qXfer:spu:read}
39541 @item @samp{qXfer:spu:write}
39546 @item @samp{qXfer:siginfo:read}
39551 @item @samp{qXfer:siginfo:write}
39556 @item @samp{qXfer:threads:read}
39561 @item @samp{qXfer:traceframe-info:read}
39566 @item @samp{qXfer:uib:read}
39571 @item @samp{qXfer:fdpic:read}
39576 @item @samp{Qbtrace:off}
39581 @item @samp{Qbtrace:bts}
39586 @item @samp{QNonStop}
39591 @item @samp{QPassSignals}
39596 @item @samp{QStartNoAckMode}
39601 @item @samp{multiprocess}
39606 @item @samp{ConditionalBreakpoints}
39611 @item @samp{ConditionalTracepoints}
39616 @item @samp{ReverseContinue}
39621 @item @samp{ReverseStep}
39626 @item @samp{TracepointSource}
39631 @item @samp{QAgent}
39636 @item @samp{QAllow}
39641 @item @samp{QDisableRandomization}
39646 @item @samp{EnableDisableTracepoints}
39651 @item @samp{QTBuffer:size}
39656 @item @samp{tracenz}
39661 @item @samp{BreakpointCommands}
39668 These are the currently defined stub features, in more detail:
39671 @cindex packet size, remote protocol
39672 @item PacketSize=@var{bytes}
39673 The remote stub can accept packets up to at least @var{bytes} in
39674 length. @value{GDBN} will send packets up to this size for bulk
39675 transfers, and will never send larger packets. This is a limit on the
39676 data characters in the packet, including the frame and checksum.
39677 There is no trailing NUL byte in a remote protocol packet; if the stub
39678 stores packets in a NUL-terminated format, it should allow an extra
39679 byte in its buffer for the NUL. If this stub feature is not supported,
39680 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39682 @item qXfer:auxv:read
39683 The remote stub understands the @samp{qXfer:auxv:read} packet
39684 (@pxref{qXfer auxiliary vector read}).
39686 @item qXfer:btrace:read
39687 The remote stub understands the @samp{qXfer:btrace:read}
39688 packet (@pxref{qXfer btrace read}).
39690 @item qXfer:features:read
39691 The remote stub understands the @samp{qXfer:features:read} packet
39692 (@pxref{qXfer target description read}).
39694 @item qXfer:libraries:read
39695 The remote stub understands the @samp{qXfer:libraries:read} packet
39696 (@pxref{qXfer library list read}).
39698 @item qXfer:libraries-svr4:read
39699 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39700 (@pxref{qXfer svr4 library list read}).
39702 @item augmented-libraries-svr4-read
39703 The remote stub understands the augmented form of the
39704 @samp{qXfer:libraries-svr4:read} packet
39705 (@pxref{qXfer svr4 library list read}).
39707 @item qXfer:memory-map:read
39708 The remote stub understands the @samp{qXfer:memory-map:read} packet
39709 (@pxref{qXfer memory map read}).
39711 @item qXfer:sdata:read
39712 The remote stub understands the @samp{qXfer:sdata:read} packet
39713 (@pxref{qXfer sdata read}).
39715 @item qXfer:spu:read
39716 The remote stub understands the @samp{qXfer:spu:read} packet
39717 (@pxref{qXfer spu read}).
39719 @item qXfer:spu:write
39720 The remote stub understands the @samp{qXfer:spu:write} packet
39721 (@pxref{qXfer spu write}).
39723 @item qXfer:siginfo:read
39724 The remote stub understands the @samp{qXfer:siginfo:read} packet
39725 (@pxref{qXfer siginfo read}).
39727 @item qXfer:siginfo:write
39728 The remote stub understands the @samp{qXfer:siginfo:write} packet
39729 (@pxref{qXfer siginfo write}).
39731 @item qXfer:threads:read
39732 The remote stub understands the @samp{qXfer:threads:read} packet
39733 (@pxref{qXfer threads read}).
39735 @item qXfer:traceframe-info:read
39736 The remote stub understands the @samp{qXfer:traceframe-info:read}
39737 packet (@pxref{qXfer traceframe info read}).
39739 @item qXfer:uib:read
39740 The remote stub understands the @samp{qXfer:uib:read}
39741 packet (@pxref{qXfer unwind info block}).
39743 @item qXfer:fdpic:read
39744 The remote stub understands the @samp{qXfer:fdpic:read}
39745 packet (@pxref{qXfer fdpic loadmap read}).
39748 The remote stub understands the @samp{QNonStop} packet
39749 (@pxref{QNonStop}).
39752 The remote stub understands the @samp{QPassSignals} packet
39753 (@pxref{QPassSignals}).
39755 @item QStartNoAckMode
39756 The remote stub understands the @samp{QStartNoAckMode} packet and
39757 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39760 @anchor{multiprocess extensions}
39761 @cindex multiprocess extensions, in remote protocol
39762 The remote stub understands the multiprocess extensions to the remote
39763 protocol syntax. The multiprocess extensions affect the syntax of
39764 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39765 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39766 replies. Note that reporting this feature indicates support for the
39767 syntactic extensions only, not that the stub necessarily supports
39768 debugging of more than one process at a time. The stub must not use
39769 multiprocess extensions in packet replies unless @value{GDBN} has also
39770 indicated it supports them in its @samp{qSupported} request.
39772 @item qXfer:osdata:read
39773 The remote stub understands the @samp{qXfer:osdata:read} packet
39774 ((@pxref{qXfer osdata read}).
39776 @item ConditionalBreakpoints
39777 The target accepts and implements evaluation of conditional expressions
39778 defined for breakpoints. The target will only report breakpoint triggers
39779 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39781 @item ConditionalTracepoints
39782 The remote stub accepts and implements conditional expressions defined
39783 for tracepoints (@pxref{Tracepoint Conditions}).
39785 @item ReverseContinue
39786 The remote stub accepts and implements the reverse continue packet
39790 The remote stub accepts and implements the reverse step packet
39793 @item TracepointSource
39794 The remote stub understands the @samp{QTDPsrc} packet that supplies
39795 the source form of tracepoint definitions.
39798 The remote stub understands the @samp{QAgent} packet.
39801 The remote stub understands the @samp{QAllow} packet.
39803 @item QDisableRandomization
39804 The remote stub understands the @samp{QDisableRandomization} packet.
39806 @item StaticTracepoint
39807 @cindex static tracepoints, in remote protocol
39808 The remote stub supports static tracepoints.
39810 @item InstallInTrace
39811 @anchor{install tracepoint in tracing}
39812 The remote stub supports installing tracepoint in tracing.
39814 @item EnableDisableTracepoints
39815 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39816 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39817 to be enabled and disabled while a trace experiment is running.
39819 @item QTBuffer:size
39820 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39821 packet that allows to change the size of the trace buffer.
39824 @cindex string tracing, in remote protocol
39825 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39826 See @ref{Bytecode Descriptions} for details about the bytecode.
39828 @item BreakpointCommands
39829 @cindex breakpoint commands, in remote protocol
39830 The remote stub supports running a breakpoint's command list itself,
39831 rather than reporting the hit to @value{GDBN}.
39834 The remote stub understands the @samp{Qbtrace:off} packet.
39837 The remote stub understands the @samp{Qbtrace:bts} packet.
39842 @cindex symbol lookup, remote request
39843 @cindex @samp{qSymbol} packet
39844 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39845 requests. Accept requests from the target for the values of symbols.
39850 The target does not need to look up any (more) symbols.
39851 @item qSymbol:@var{sym_name}
39852 The target requests the value of symbol @var{sym_name} (hex encoded).
39853 @value{GDBN} may provide the value by using the
39854 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39858 @item qSymbol:@var{sym_value}:@var{sym_name}
39859 Set the value of @var{sym_name} to @var{sym_value}.
39861 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39862 target has previously requested.
39864 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39865 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39871 The target does not need to look up any (more) symbols.
39872 @item qSymbol:@var{sym_name}
39873 The target requests the value of a new symbol @var{sym_name} (hex
39874 encoded). @value{GDBN} will continue to supply the values of symbols
39875 (if available), until the target ceases to request them.
39880 @itemx QTDisconnected
39887 @itemx qTMinFTPILen
39889 @xref{Tracepoint Packets}.
39891 @item qThreadExtraInfo,@var{thread-id}
39892 @cindex thread attributes info, remote request
39893 @cindex @samp{qThreadExtraInfo} packet
39894 Obtain a printable string description of a thread's attributes from
39895 the target OS. @var{thread-id} is a thread ID;
39896 see @ref{thread-id syntax}. This
39897 string may contain anything that the target OS thinks is interesting
39898 for @value{GDBN} to tell the user about the thread. The string is
39899 displayed in @value{GDBN}'s @code{info threads} display. Some
39900 examples of possible thread extra info strings are @samp{Runnable}, or
39901 @samp{Blocked on Mutex}.
39905 @item @var{XX}@dots{}
39906 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39907 comprising the printable string containing the extra information about
39908 the thread's attributes.
39911 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39912 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39913 conventions above. Please don't use this packet as a model for new
39932 @xref{Tracepoint Packets}.
39934 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39935 @cindex read special object, remote request
39936 @cindex @samp{qXfer} packet
39937 @anchor{qXfer read}
39938 Read uninterpreted bytes from the target's special data area
39939 identified by the keyword @var{object}. Request @var{length} bytes
39940 starting at @var{offset} bytes into the data. The content and
39941 encoding of @var{annex} is specific to @var{object}; it can supply
39942 additional details about what data to access.
39944 Here are the specific requests of this form defined so far. All
39945 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39946 formats, listed below.
39949 @item qXfer:auxv:read::@var{offset},@var{length}
39950 @anchor{qXfer auxiliary vector read}
39951 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39952 auxiliary vector}. Note @var{annex} must be empty.
39954 This packet is not probed by default; the remote stub must request it,
39955 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39957 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39958 @anchor{qXfer btrace read}
39960 Return a description of the current branch trace.
39961 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39962 packet may have one of the following values:
39966 Returns all available branch trace.
39969 Returns all available branch trace if the branch trace changed since
39970 the last read request.
39973 This packet is not probed by default; the remote stub must request it
39974 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39976 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39977 @anchor{qXfer target description read}
39978 Access the @dfn{target description}. @xref{Target Descriptions}. The
39979 annex specifies which XML document to access. The main description is
39980 always loaded from the @samp{target.xml} annex.
39982 This packet is not probed by default; the remote stub must request it,
39983 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39985 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39986 @anchor{qXfer library list read}
39987 Access the target's list of loaded libraries. @xref{Library List Format}.
39988 The annex part of the generic @samp{qXfer} packet must be empty
39989 (@pxref{qXfer read}).
39991 Targets which maintain a list of libraries in the program's memory do
39992 not need to implement this packet; it is designed for platforms where
39993 the operating system manages the list of loaded libraries.
39995 This packet is not probed by default; the remote stub must request it,
39996 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39998 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39999 @anchor{qXfer svr4 library list read}
40000 Access the target's list of loaded libraries when the target is an SVR4
40001 platform. @xref{Library List Format for SVR4 Targets}. The annex part
40002 of the generic @samp{qXfer} packet must be empty unless the remote
40003 stub indicated it supports the augmented form of this packet
40004 by supplying an appropriate @samp{qSupported} response
40005 (@pxref{qXfer read}, @ref{qSupported}).
40007 This packet is optional for better performance on SVR4 targets.
40008 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
40010 This packet is not probed by default; the remote stub must request it,
40011 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40013 If the remote stub indicates it supports the augmented form of this
40014 packet then the annex part of the generic @samp{qXfer} packet may
40015 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
40016 arguments. The currently supported arguments are:
40019 @item start=@var{address}
40020 A hexadecimal number specifying the address of the @samp{struct
40021 link_map} to start reading the library list from. If unset or zero
40022 then the first @samp{struct link_map} in the library list will be
40023 chosen as the starting point.
40025 @item prev=@var{address}
40026 A hexadecimal number specifying the address of the @samp{struct
40027 link_map} immediately preceding the @samp{struct link_map}
40028 specified by the @samp{start} argument. If unset or zero then
40029 the remote stub will expect that no @samp{struct link_map}
40030 exists prior to the starting point.
40034 Arguments that are not understood by the remote stub will be silently
40037 @item qXfer:memory-map:read::@var{offset},@var{length}
40038 @anchor{qXfer memory map read}
40039 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
40040 annex part of the generic @samp{qXfer} packet must be empty
40041 (@pxref{qXfer read}).
40043 This packet is not probed by default; the remote stub must request it,
40044 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40046 @item qXfer:sdata:read::@var{offset},@var{length}
40047 @anchor{qXfer sdata read}
40049 Read contents of the extra collected static tracepoint marker
40050 information. The annex part of the generic @samp{qXfer} packet must
40051 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
40054 This packet is not probed by default; the remote stub must request it,
40055 by supplying an appropriate @samp{qSupported} response
40056 (@pxref{qSupported}).
40058 @item qXfer:siginfo:read::@var{offset},@var{length}
40059 @anchor{qXfer siginfo read}
40060 Read contents of the extra signal information on the target
40061 system. The annex part of the generic @samp{qXfer} packet must be
40062 empty (@pxref{qXfer read}).
40064 This packet is not probed by default; the remote stub must request it,
40065 by supplying an appropriate @samp{qSupported} response
40066 (@pxref{qSupported}).
40068 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
40069 @anchor{qXfer spu read}
40070 Read contents of an @code{spufs} file on the target system. The
40071 annex specifies which file to read; it must be of the form
40072 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40073 in the target process, and @var{name} identifes the @code{spufs} file
40074 in that context to be accessed.
40076 This packet is not probed by default; the remote stub must request it,
40077 by supplying an appropriate @samp{qSupported} response
40078 (@pxref{qSupported}).
40080 @item qXfer:threads:read::@var{offset},@var{length}
40081 @anchor{qXfer threads read}
40082 Access the list of threads on target. @xref{Thread List Format}. The
40083 annex part of the generic @samp{qXfer} packet must be empty
40084 (@pxref{qXfer read}).
40086 This packet is not probed by default; the remote stub must request it,
40087 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40089 @item qXfer:traceframe-info:read::@var{offset},@var{length}
40090 @anchor{qXfer traceframe info read}
40092 Return a description of the current traceframe's contents.
40093 @xref{Traceframe Info Format}. The annex part of the generic
40094 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
40096 This packet is not probed by default; the remote stub must request it,
40097 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40099 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
40100 @anchor{qXfer unwind info block}
40102 Return the unwind information block for @var{pc}. This packet is used
40103 on OpenVMS/ia64 to ask the kernel unwind information.
40105 This packet is not probed by default.
40107 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
40108 @anchor{qXfer fdpic loadmap read}
40109 Read contents of @code{loadmap}s on the target system. The
40110 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
40111 executable @code{loadmap} or interpreter @code{loadmap} to read.
40113 This packet is not probed by default; the remote stub must request it,
40114 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40116 @item qXfer:osdata:read::@var{offset},@var{length}
40117 @anchor{qXfer osdata read}
40118 Access the target's @dfn{operating system information}.
40119 @xref{Operating System Information}.
40126 Data @var{data} (@pxref{Binary Data}) has been read from the
40127 target. There may be more data at a higher address (although
40128 it is permitted to return @samp{m} even for the last valid
40129 block of data, as long as at least one byte of data was read).
40130 @var{data} may have fewer bytes than the @var{length} in the
40134 Data @var{data} (@pxref{Binary Data}) has been read from the target.
40135 There is no more data to be read. @var{data} may have fewer bytes
40136 than the @var{length} in the request.
40139 The @var{offset} in the request is at the end of the data.
40140 There is no more data to be read.
40143 The request was malformed, or @var{annex} was invalid.
40146 The offset was invalid, or there was an error encountered reading the data.
40147 @var{nn} is a hex-encoded @code{errno} value.
40150 An empty reply indicates the @var{object} string was not recognized by
40151 the stub, or that the object does not support reading.
40154 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
40155 @cindex write data into object, remote request
40156 @anchor{qXfer write}
40157 Write uninterpreted bytes into the target's special data area
40158 identified by the keyword @var{object}, starting at @var{offset} bytes
40159 into the data. @var{data}@dots{} is the binary-encoded data
40160 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
40161 is specific to @var{object}; it can supply additional details about what data
40164 Here are the specific requests of this form defined so far. All
40165 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
40166 formats, listed below.
40169 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
40170 @anchor{qXfer siginfo write}
40171 Write @var{data} to the extra signal information on the target system.
40172 The annex part of the generic @samp{qXfer} packet must be
40173 empty (@pxref{qXfer write}).
40175 This packet is not probed by default; the remote stub must request it,
40176 by supplying an appropriate @samp{qSupported} response
40177 (@pxref{qSupported}).
40179 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
40180 @anchor{qXfer spu write}
40181 Write @var{data} to an @code{spufs} file on the target system. The
40182 annex specifies which file to write; it must be of the form
40183 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40184 in the target process, and @var{name} identifes the @code{spufs} file
40185 in that context to be accessed.
40187 This packet is not probed by default; the remote stub must request it,
40188 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40194 @var{nn} (hex encoded) is the number of bytes written.
40195 This may be fewer bytes than supplied in the request.
40198 The request was malformed, or @var{annex} was invalid.
40201 The offset was invalid, or there was an error encountered writing the data.
40202 @var{nn} is a hex-encoded @code{errno} value.
40205 An empty reply indicates the @var{object} string was not
40206 recognized by the stub, or that the object does not support writing.
40209 @item qXfer:@var{object}:@var{operation}:@dots{}
40210 Requests of this form may be added in the future. When a stub does
40211 not recognize the @var{object} keyword, or its support for
40212 @var{object} does not recognize the @var{operation} keyword, the stub
40213 must respond with an empty packet.
40215 @item qAttached:@var{pid}
40216 @cindex query attached, remote request
40217 @cindex @samp{qAttached} packet
40218 Return an indication of whether the remote server attached to an
40219 existing process or created a new process. When the multiprocess
40220 protocol extensions are supported (@pxref{multiprocess extensions}),
40221 @var{pid} is an integer in hexadecimal format identifying the target
40222 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40223 the query packet will be simplified as @samp{qAttached}.
40225 This query is used, for example, to know whether the remote process
40226 should be detached or killed when a @value{GDBN} session is ended with
40227 the @code{quit} command.
40232 The remote server attached to an existing process.
40234 The remote server created a new process.
40236 A badly formed request or an error was encountered.
40240 Enable branch tracing for the current thread using bts tracing.
40245 Branch tracing has been enabled.
40247 A badly formed request or an error was encountered.
40251 Disable branch tracing for the current thread.
40256 Branch tracing has been disabled.
40258 A badly formed request or an error was encountered.
40263 @node Architecture-Specific Protocol Details
40264 @section Architecture-Specific Protocol Details
40266 This section describes how the remote protocol is applied to specific
40267 target architectures. Also see @ref{Standard Target Features}, for
40268 details of XML target descriptions for each architecture.
40271 * ARM-Specific Protocol Details::
40272 * MIPS-Specific Protocol Details::
40275 @node ARM-Specific Protocol Details
40276 @subsection @acronym{ARM}-specific Protocol Details
40279 * ARM Breakpoint Kinds::
40282 @node ARM Breakpoint Kinds
40283 @subsubsection @acronym{ARM} Breakpoint Kinds
40284 @cindex breakpoint kinds, @acronym{ARM}
40286 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40291 16-bit Thumb mode breakpoint.
40294 32-bit Thumb mode (Thumb-2) breakpoint.
40297 32-bit @acronym{ARM} mode breakpoint.
40301 @node MIPS-Specific Protocol Details
40302 @subsection @acronym{MIPS}-specific Protocol Details
40305 * MIPS Register packet Format::
40306 * MIPS Breakpoint Kinds::
40309 @node MIPS Register packet Format
40310 @subsubsection @acronym{MIPS} Register Packet Format
40311 @cindex register packet format, @acronym{MIPS}
40313 The following @code{g}/@code{G} packets have previously been defined.
40314 In the below, some thirty-two bit registers are transferred as
40315 sixty-four bits. Those registers should be zero/sign extended (which?)
40316 to fill the space allocated. Register bytes are transferred in target
40317 byte order. The two nibbles within a register byte are transferred
40318 most-significant -- least-significant.
40323 All registers are transferred as thirty-two bit quantities in the order:
40324 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40325 registers; fsr; fir; fp.
40328 All registers are transferred as sixty-four bit quantities (including
40329 thirty-two bit registers such as @code{sr}). The ordering is the same
40334 @node MIPS Breakpoint Kinds
40335 @subsubsection @acronym{MIPS} Breakpoint Kinds
40336 @cindex breakpoint kinds, @acronym{MIPS}
40338 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40343 16-bit @acronym{MIPS16} mode breakpoint.
40346 16-bit @acronym{microMIPS} mode breakpoint.
40349 32-bit standard @acronym{MIPS} mode breakpoint.
40352 32-bit @acronym{microMIPS} mode breakpoint.
40356 @node Tracepoint Packets
40357 @section Tracepoint Packets
40358 @cindex tracepoint packets
40359 @cindex packets, tracepoint
40361 Here we describe the packets @value{GDBN} uses to implement
40362 tracepoints (@pxref{Tracepoints}).
40366 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40367 @cindex @samp{QTDP} packet
40368 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40369 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40370 the tracepoint is disabled. @var{step} is the tracepoint's step
40371 count, and @var{pass} is its pass count. If an @samp{F} is present,
40372 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40373 the number of bytes that the target should copy elsewhere to make room
40374 for the tracepoint. If an @samp{X} is present, it introduces a
40375 tracepoint condition, which consists of a hexadecimal length, followed
40376 by a comma and hex-encoded bytes, in a manner similar to action
40377 encodings as described below. If the trailing @samp{-} is present,
40378 further @samp{QTDP} packets will follow to specify this tracepoint's
40384 The packet was understood and carried out.
40386 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40388 The packet was not recognized.
40391 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40392 Define actions to be taken when a tracepoint is hit. @var{n} and
40393 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40394 this tracepoint. This packet may only be sent immediately after
40395 another @samp{QTDP} packet that ended with a @samp{-}. If the
40396 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40397 specifying more actions for this tracepoint.
40399 In the series of action packets for a given tracepoint, at most one
40400 can have an @samp{S} before its first @var{action}. If such a packet
40401 is sent, it and the following packets define ``while-stepping''
40402 actions. Any prior packets define ordinary actions --- that is, those
40403 taken when the tracepoint is first hit. If no action packet has an
40404 @samp{S}, then all the packets in the series specify ordinary
40405 tracepoint actions.
40407 The @samp{@var{action}@dots{}} portion of the packet is a series of
40408 actions, concatenated without separators. Each action has one of the
40414 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40415 a hexadecimal number whose @var{i}'th bit is set if register number
40416 @var{i} should be collected. (The least significant bit is numbered
40417 zero.) Note that @var{mask} may be any number of digits long; it may
40418 not fit in a 32-bit word.
40420 @item M @var{basereg},@var{offset},@var{len}
40421 Collect @var{len} bytes of memory starting at the address in register
40422 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40423 @samp{-1}, then the range has a fixed address: @var{offset} is the
40424 address of the lowest byte to collect. The @var{basereg},
40425 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40426 values (the @samp{-1} value for @var{basereg} is a special case).
40428 @item X @var{len},@var{expr}
40429 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40430 it directs. @var{expr} is an agent expression, as described in
40431 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40432 two-digit hex number in the packet; @var{len} is the number of bytes
40433 in the expression (and thus one-half the number of hex digits in the
40438 Any number of actions may be packed together in a single @samp{QTDP}
40439 packet, as long as the packet does not exceed the maximum packet
40440 length (400 bytes, for many stubs). There may be only one @samp{R}
40441 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40442 actions. Any registers referred to by @samp{M} and @samp{X} actions
40443 must be collected by a preceding @samp{R} action. (The
40444 ``while-stepping'' actions are treated as if they were attached to a
40445 separate tracepoint, as far as these restrictions are concerned.)
40450 The packet was understood and carried out.
40452 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40454 The packet was not recognized.
40457 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40458 @cindex @samp{QTDPsrc} packet
40459 Specify a source string of tracepoint @var{n} at address @var{addr}.
40460 This is useful to get accurate reproduction of the tracepoints
40461 originally downloaded at the beginning of the trace run. @var{type}
40462 is the name of the tracepoint part, such as @samp{cond} for the
40463 tracepoint's conditional expression (see below for a list of types), while
40464 @var{bytes} is the string, encoded in hexadecimal.
40466 @var{start} is the offset of the @var{bytes} within the overall source
40467 string, while @var{slen} is the total length of the source string.
40468 This is intended for handling source strings that are longer than will
40469 fit in a single packet.
40470 @c Add detailed example when this info is moved into a dedicated
40471 @c tracepoint descriptions section.
40473 The available string types are @samp{at} for the location,
40474 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40475 @value{GDBN} sends a separate packet for each command in the action
40476 list, in the same order in which the commands are stored in the list.
40478 The target does not need to do anything with source strings except
40479 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40482 Although this packet is optional, and @value{GDBN} will only send it
40483 if the target replies with @samp{TracepointSource} @xref{General
40484 Query Packets}, it makes both disconnected tracing and trace files
40485 much easier to use. Otherwise the user must be careful that the
40486 tracepoints in effect while looking at trace frames are identical to
40487 the ones in effect during the trace run; even a small discrepancy
40488 could cause @samp{tdump} not to work, or a particular trace frame not
40491 @item QTDV:@var{n}:@var{value}
40492 @cindex define trace state variable, remote request
40493 @cindex @samp{QTDV} packet
40494 Create a new trace state variable, number @var{n}, with an initial
40495 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40496 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40497 the option of not using this packet for initial values of zero; the
40498 target should simply create the trace state variables as they are
40499 mentioned in expressions.
40501 @item QTFrame:@var{n}
40502 @cindex @samp{QTFrame} packet
40503 Select the @var{n}'th tracepoint frame from the buffer, and use the
40504 register and memory contents recorded there to answer subsequent
40505 request packets from @value{GDBN}.
40507 A successful reply from the stub indicates that the stub has found the
40508 requested frame. The response is a series of parts, concatenated
40509 without separators, describing the frame we selected. Each part has
40510 one of the following forms:
40514 The selected frame is number @var{n} in the trace frame buffer;
40515 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40516 was no frame matching the criteria in the request packet.
40519 The selected trace frame records a hit of tracepoint number @var{t};
40520 @var{t} is a hexadecimal number.
40524 @item QTFrame:pc:@var{addr}
40525 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40526 currently selected frame whose PC is @var{addr};
40527 @var{addr} is a hexadecimal number.
40529 @item QTFrame:tdp:@var{t}
40530 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40531 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40532 is a hexadecimal number.
40534 @item QTFrame:range:@var{start}:@var{end}
40535 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40536 currently selected frame whose PC is between @var{start} (inclusive)
40537 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40540 @item QTFrame:outside:@var{start}:@var{end}
40541 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40542 frame @emph{outside} the given range of addresses (exclusive).
40545 @cindex @samp{qTMinFTPILen} packet
40546 This packet requests the minimum length of instruction at which a fast
40547 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40548 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40549 it depends on the target system being able to create trampolines in
40550 the first 64K of memory, which might or might not be possible for that
40551 system. So the reply to this packet will be 4 if it is able to
40558 The minimum instruction length is currently unknown.
40560 The minimum instruction length is @var{length}, where @var{length} is greater
40561 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40562 that a fast tracepoint may be placed on any instruction regardless of size.
40564 An error has occurred.
40566 An empty reply indicates that the request is not supported by the stub.
40570 @cindex @samp{QTStart} packet
40571 Begin the tracepoint experiment. Begin collecting data from
40572 tracepoint hits in the trace frame buffer. This packet supports the
40573 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40574 instruction reply packet}).
40577 @cindex @samp{QTStop} packet
40578 End the tracepoint experiment. Stop collecting trace frames.
40580 @item QTEnable:@var{n}:@var{addr}
40582 @cindex @samp{QTEnable} packet
40583 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40584 experiment. If the tracepoint was previously disabled, then collection
40585 of data from it will resume.
40587 @item QTDisable:@var{n}:@var{addr}
40589 @cindex @samp{QTDisable} packet
40590 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40591 experiment. No more data will be collected from the tracepoint unless
40592 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40595 @cindex @samp{QTinit} packet
40596 Clear the table of tracepoints, and empty the trace frame buffer.
40598 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40599 @cindex @samp{QTro} packet
40600 Establish the given ranges of memory as ``transparent''. The stub
40601 will answer requests for these ranges from memory's current contents,
40602 if they were not collected as part of the tracepoint hit.
40604 @value{GDBN} uses this to mark read-only regions of memory, like those
40605 containing program code. Since these areas never change, they should
40606 still have the same contents they did when the tracepoint was hit, so
40607 there's no reason for the stub to refuse to provide their contents.
40609 @item QTDisconnected:@var{value}
40610 @cindex @samp{QTDisconnected} packet
40611 Set the choice to what to do with the tracing run when @value{GDBN}
40612 disconnects from the target. A @var{value} of 1 directs the target to
40613 continue the tracing run, while 0 tells the target to stop tracing if
40614 @value{GDBN} is no longer in the picture.
40617 @cindex @samp{qTStatus} packet
40618 Ask the stub if there is a trace experiment running right now.
40620 The reply has the form:
40624 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40625 @var{running} is a single digit @code{1} if the trace is presently
40626 running, or @code{0} if not. It is followed by semicolon-separated
40627 optional fields that an agent may use to report additional status.
40631 If the trace is not running, the agent may report any of several
40632 explanations as one of the optional fields:
40637 No trace has been run yet.
40639 @item tstop[:@var{text}]:0
40640 The trace was stopped by a user-originated stop command. The optional
40641 @var{text} field is a user-supplied string supplied as part of the
40642 stop command (for instance, an explanation of why the trace was
40643 stopped manually). It is hex-encoded.
40646 The trace stopped because the trace buffer filled up.
40648 @item tdisconnected:0
40649 The trace stopped because @value{GDBN} disconnected from the target.
40651 @item tpasscount:@var{tpnum}
40652 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40654 @item terror:@var{text}:@var{tpnum}
40655 The trace stopped because tracepoint @var{tpnum} had an error. The
40656 string @var{text} is available to describe the nature of the error
40657 (for instance, a divide by zero in the condition expression).
40658 @var{text} is hex encoded.
40661 The trace stopped for some other reason.
40665 Additional optional fields supply statistical and other information.
40666 Although not required, they are extremely useful for users monitoring
40667 the progress of a trace run. If a trace has stopped, and these
40668 numbers are reported, they must reflect the state of the just-stopped
40673 @item tframes:@var{n}
40674 The number of trace frames in the buffer.
40676 @item tcreated:@var{n}
40677 The total number of trace frames created during the run. This may
40678 be larger than the trace frame count, if the buffer is circular.
40680 @item tsize:@var{n}
40681 The total size of the trace buffer, in bytes.
40683 @item tfree:@var{n}
40684 The number of bytes still unused in the buffer.
40686 @item circular:@var{n}
40687 The value of the circular trace buffer flag. @code{1} means that the
40688 trace buffer is circular and old trace frames will be discarded if
40689 necessary to make room, @code{0} means that the trace buffer is linear
40692 @item disconn:@var{n}
40693 The value of the disconnected tracing flag. @code{1} means that
40694 tracing will continue after @value{GDBN} disconnects, @code{0} means
40695 that the trace run will stop.
40699 @item qTP:@var{tp}:@var{addr}
40700 @cindex tracepoint status, remote request
40701 @cindex @samp{qTP} packet
40702 Ask the stub for the current state of tracepoint number @var{tp} at
40703 address @var{addr}.
40707 @item V@var{hits}:@var{usage}
40708 The tracepoint has been hit @var{hits} times so far during the trace
40709 run, and accounts for @var{usage} in the trace buffer. Note that
40710 @code{while-stepping} steps are not counted as separate hits, but the
40711 steps' space consumption is added into the usage number.
40715 @item qTV:@var{var}
40716 @cindex trace state variable value, remote request
40717 @cindex @samp{qTV} packet
40718 Ask the stub for the value of the trace state variable number @var{var}.
40723 The value of the variable is @var{value}. This will be the current
40724 value of the variable if the user is examining a running target, or a
40725 saved value if the variable was collected in the trace frame that the
40726 user is looking at. Note that multiple requests may result in
40727 different reply values, such as when requesting values while the
40728 program is running.
40731 The value of the variable is unknown. This would occur, for example,
40732 if the user is examining a trace frame in which the requested variable
40737 @cindex @samp{qTfP} packet
40739 @cindex @samp{qTsP} packet
40740 These packets request data about tracepoints that are being used by
40741 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40742 of data, and multiple @code{qTsP} to get additional pieces. Replies
40743 to these packets generally take the form of the @code{QTDP} packets
40744 that define tracepoints. (FIXME add detailed syntax)
40747 @cindex @samp{qTfV} packet
40749 @cindex @samp{qTsV} packet
40750 These packets request data about trace state variables that are on the
40751 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40752 and multiple @code{qTsV} to get additional variables. Replies to
40753 these packets follow the syntax of the @code{QTDV} packets that define
40754 trace state variables.
40760 @cindex @samp{qTfSTM} packet
40761 @cindex @samp{qTsSTM} packet
40762 These packets request data about static tracepoint markers that exist
40763 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40764 first piece of data, and multiple @code{qTsSTM} to get additional
40765 pieces. Replies to these packets take the following form:
40769 @item m @var{address}:@var{id}:@var{extra}
40771 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40772 a comma-separated list of markers
40774 (lower case letter @samp{L}) denotes end of list.
40776 An error occurred. @var{nn} are hex digits.
40778 An empty reply indicates that the request is not supported by the
40782 @var{address} is encoded in hex.
40783 @var{id} and @var{extra} are strings encoded in hex.
40785 In response to each query, the target will reply with a list of one or
40786 more markers, separated by commas. @value{GDBN} will respond to each
40787 reply with a request for more markers (using the @samp{qs} form of the
40788 query), until the target responds with @samp{l} (lower-case ell, for
40791 @item qTSTMat:@var{address}
40793 @cindex @samp{qTSTMat} packet
40794 This packets requests data about static tracepoint markers in the
40795 target program at @var{address}. Replies to this packet follow the
40796 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40797 tracepoint markers.
40799 @item QTSave:@var{filename}
40800 @cindex @samp{QTSave} packet
40801 This packet directs the target to save trace data to the file name
40802 @var{filename} in the target's filesystem. @var{filename} is encoded
40803 as a hex string; the interpretation of the file name (relative vs
40804 absolute, wild cards, etc) is up to the target.
40806 @item qTBuffer:@var{offset},@var{len}
40807 @cindex @samp{qTBuffer} packet
40808 Return up to @var{len} bytes of the current contents of trace buffer,
40809 starting at @var{offset}. The trace buffer is treated as if it were
40810 a contiguous collection of traceframes, as per the trace file format.
40811 The reply consists as many hex-encoded bytes as the target can deliver
40812 in a packet; it is not an error to return fewer than were asked for.
40813 A reply consisting of just @code{l} indicates that no bytes are
40816 @item QTBuffer:circular:@var{value}
40817 This packet directs the target to use a circular trace buffer if
40818 @var{value} is 1, or a linear buffer if the value is 0.
40820 @item QTBuffer:size:@var{size}
40821 @anchor{QTBuffer-size}
40822 @cindex @samp{QTBuffer size} packet
40823 This packet directs the target to make the trace buffer be of size
40824 @var{size} if possible. A value of @code{-1} tells the target to
40825 use whatever size it prefers.
40827 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40828 @cindex @samp{QTNotes} packet
40829 This packet adds optional textual notes to the trace run. Allowable
40830 types include @code{user}, @code{notes}, and @code{tstop}, the
40831 @var{text} fields are arbitrary strings, hex-encoded.
40835 @subsection Relocate instruction reply packet
40836 When installing fast tracepoints in memory, the target may need to
40837 relocate the instruction currently at the tracepoint address to a
40838 different address in memory. For most instructions, a simple copy is
40839 enough, but, for example, call instructions that implicitly push the
40840 return address on the stack, and relative branches or other
40841 PC-relative instructions require offset adjustment, so that the effect
40842 of executing the instruction at a different address is the same as if
40843 it had executed in the original location.
40845 In response to several of the tracepoint packets, the target may also
40846 respond with a number of intermediate @samp{qRelocInsn} request
40847 packets before the final result packet, to have @value{GDBN} handle
40848 this relocation operation. If a packet supports this mechanism, its
40849 documentation will explicitly say so. See for example the above
40850 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40851 format of the request is:
40854 @item qRelocInsn:@var{from};@var{to}
40856 This requests @value{GDBN} to copy instruction at address @var{from}
40857 to address @var{to}, possibly adjusted so that executing the
40858 instruction at @var{to} has the same effect as executing it at
40859 @var{from}. @value{GDBN} writes the adjusted instruction to target
40860 memory starting at @var{to}.
40865 @item qRelocInsn:@var{adjusted_size}
40866 Informs the stub the relocation is complete. @var{adjusted_size} is
40867 the length in bytes of resulting relocated instruction sequence.
40869 A badly formed request was detected, or an error was encountered while
40870 relocating the instruction.
40873 @node Host I/O Packets
40874 @section Host I/O Packets
40875 @cindex Host I/O, remote protocol
40876 @cindex file transfer, remote protocol
40878 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40879 operations on the far side of a remote link. For example, Host I/O is
40880 used to upload and download files to a remote target with its own
40881 filesystem. Host I/O uses the same constant values and data structure
40882 layout as the target-initiated File-I/O protocol. However, the
40883 Host I/O packets are structured differently. The target-initiated
40884 protocol relies on target memory to store parameters and buffers.
40885 Host I/O requests are initiated by @value{GDBN}, and the
40886 target's memory is not involved. @xref{File-I/O Remote Protocol
40887 Extension}, for more details on the target-initiated protocol.
40889 The Host I/O request packets all encode a single operation along with
40890 its arguments. They have this format:
40894 @item vFile:@var{operation}: @var{parameter}@dots{}
40895 @var{operation} is the name of the particular request; the target
40896 should compare the entire packet name up to the second colon when checking
40897 for a supported operation. The format of @var{parameter} depends on
40898 the operation. Numbers are always passed in hexadecimal. Negative
40899 numbers have an explicit minus sign (i.e.@: two's complement is not
40900 used). Strings (e.g.@: filenames) are encoded as a series of
40901 hexadecimal bytes. The last argument to a system call may be a
40902 buffer of escaped binary data (@pxref{Binary Data}).
40906 The valid responses to Host I/O packets are:
40910 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40911 @var{result} is the integer value returned by this operation, usually
40912 non-negative for success and -1 for errors. If an error has occured,
40913 @var{errno} will be included in the result. @var{errno} will have a
40914 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40915 operations which return data, @var{attachment} supplies the data as a
40916 binary buffer. Binary buffers in response packets are escaped in the
40917 normal way (@pxref{Binary Data}). See the individual packet
40918 documentation for the interpretation of @var{result} and
40922 An empty response indicates that this operation is not recognized.
40926 These are the supported Host I/O operations:
40929 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40930 Open a file at @var{pathname} and return a file descriptor for it, or
40931 return -1 if an error occurs. @var{pathname} is a string,
40932 @var{flags} is an integer indicating a mask of open flags
40933 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40934 of mode bits to use if the file is created (@pxref{mode_t Values}).
40935 @xref{open}, for details of the open flags and mode values.
40937 @item vFile:close: @var{fd}
40938 Close the open file corresponding to @var{fd} and return 0, or
40939 -1 if an error occurs.
40941 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40942 Read data from the open file corresponding to @var{fd}. Up to
40943 @var{count} bytes will be read from the file, starting at @var{offset}
40944 relative to the start of the file. The target may read fewer bytes;
40945 common reasons include packet size limits and an end-of-file
40946 condition. The number of bytes read is returned. Zero should only be
40947 returned for a successful read at the end of the file, or if
40948 @var{count} was zero.
40950 The data read should be returned as a binary attachment on success.
40951 If zero bytes were read, the response should include an empty binary
40952 attachment (i.e.@: a trailing semicolon). The return value is the
40953 number of target bytes read; the binary attachment may be longer if
40954 some characters were escaped.
40956 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40957 Write @var{data} (a binary buffer) to the open file corresponding
40958 to @var{fd}. Start the write at @var{offset} from the start of the
40959 file. Unlike many @code{write} system calls, there is no
40960 separate @var{count} argument; the length of @var{data} in the
40961 packet is used. @samp{vFile:write} returns the number of bytes written,
40962 which may be shorter than the length of @var{data}, or -1 if an
40965 @item vFile:unlink: @var{pathname}
40966 Delete the file at @var{pathname} on the target. Return 0,
40967 or -1 if an error occurs. @var{pathname} is a string.
40969 @item vFile:readlink: @var{filename}
40970 Read value of symbolic link @var{filename} on the target. Return
40971 the number of bytes read, or -1 if an error occurs.
40973 The data read should be returned as a binary attachment on success.
40974 If zero bytes were read, the response should include an empty binary
40975 attachment (i.e.@: a trailing semicolon). The return value is the
40976 number of target bytes read; the binary attachment may be longer if
40977 some characters were escaped.
40982 @section Interrupts
40983 @cindex interrupts (remote protocol)
40985 When a program on the remote target is running, @value{GDBN} may
40986 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40987 a @code{BREAK} followed by @code{g},
40988 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40990 The precise meaning of @code{BREAK} is defined by the transport
40991 mechanism and may, in fact, be undefined. @value{GDBN} does not
40992 currently define a @code{BREAK} mechanism for any of the network
40993 interfaces except for TCP, in which case @value{GDBN} sends the
40994 @code{telnet} BREAK sequence.
40996 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40997 transport mechanisms. It is represented by sending the single byte
40998 @code{0x03} without any of the usual packet overhead described in
40999 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
41000 transmitted as part of a packet, it is considered to be packet data
41001 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
41002 (@pxref{X packet}), used for binary downloads, may include an unescaped
41003 @code{0x03} as part of its packet.
41005 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
41006 When Linux kernel receives this sequence from serial port,
41007 it stops execution and connects to gdb.
41009 Stubs are not required to recognize these interrupt mechanisms and the
41010 precise meaning associated with receipt of the interrupt is
41011 implementation defined. If the target supports debugging of multiple
41012 threads and/or processes, it should attempt to interrupt all
41013 currently-executing threads and processes.
41014 If the stub is successful at interrupting the
41015 running program, it should send one of the stop
41016 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
41017 of successfully stopping the program in all-stop mode, and a stop reply
41018 for each stopped thread in non-stop mode.
41019 Interrupts received while the
41020 program is stopped are discarded.
41022 @node Notification Packets
41023 @section Notification Packets
41024 @cindex notification packets
41025 @cindex packets, notification
41027 The @value{GDBN} remote serial protocol includes @dfn{notifications},
41028 packets that require no acknowledgment. Both the GDB and the stub
41029 may send notifications (although the only notifications defined at
41030 present are sent by the stub). Notifications carry information
41031 without incurring the round-trip latency of an acknowledgment, and so
41032 are useful for low-impact communications where occasional packet loss
41035 A notification packet has the form @samp{% @var{data} #
41036 @var{checksum}}, where @var{data} is the content of the notification,
41037 and @var{checksum} is a checksum of @var{data}, computed and formatted
41038 as for ordinary @value{GDBN} packets. A notification's @var{data}
41039 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
41040 receiving a notification, the recipient sends no @samp{+} or @samp{-}
41041 to acknowledge the notification's receipt or to report its corruption.
41043 Every notification's @var{data} begins with a name, which contains no
41044 colon characters, followed by a colon character.
41046 Recipients should silently ignore corrupted notifications and
41047 notifications they do not understand. Recipients should restart
41048 timeout periods on receipt of a well-formed notification, whether or
41049 not they understand it.
41051 Senders should only send the notifications described here when this
41052 protocol description specifies that they are permitted. In the
41053 future, we may extend the protocol to permit existing notifications in
41054 new contexts; this rule helps older senders avoid confusing newer
41057 (Older versions of @value{GDBN} ignore bytes received until they see
41058 the @samp{$} byte that begins an ordinary packet, so new stubs may
41059 transmit notifications without fear of confusing older clients. There
41060 are no notifications defined for @value{GDBN} to send at the moment, but we
41061 assume that most older stubs would ignore them, as well.)
41063 Each notification is comprised of three parts:
41065 @item @var{name}:@var{event}
41066 The notification packet is sent by the side that initiates the
41067 exchange (currently, only the stub does that), with @var{event}
41068 carrying the specific information about the notification.
41069 @var{name} is the name of the notification.
41071 The acknowledge sent by the other side, usually @value{GDBN}, to
41072 acknowledge the exchange and request the event.
41075 The purpose of an asynchronous notification mechanism is to report to
41076 @value{GDBN} that something interesting happened in the remote stub.
41078 The remote stub may send notification @var{name}:@var{event}
41079 at any time, but @value{GDBN} acknowledges the notification when
41080 appropriate. The notification event is pending before @value{GDBN}
41081 acknowledges. Only one notification at a time may be pending; if
41082 additional events occur before @value{GDBN} has acknowledged the
41083 previous notification, they must be queued by the stub for later
41084 synchronous transmission in response to @var{ack} packets from
41085 @value{GDBN}. Because the notification mechanism is unreliable,
41086 the stub is permitted to resend a notification if it believes
41087 @value{GDBN} may not have received it.
41089 Specifically, notifications may appear when @value{GDBN} is not
41090 otherwise reading input from the stub, or when @value{GDBN} is
41091 expecting to read a normal synchronous response or a
41092 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
41093 Notification packets are distinct from any other communication from
41094 the stub so there is no ambiguity.
41096 After receiving a notification, @value{GDBN} shall acknowledge it by
41097 sending a @var{ack} packet as a regular, synchronous request to the
41098 stub. Such acknowledgment is not required to happen immediately, as
41099 @value{GDBN} is permitted to send other, unrelated packets to the
41100 stub first, which the stub should process normally.
41102 Upon receiving a @var{ack} packet, if the stub has other queued
41103 events to report to @value{GDBN}, it shall respond by sending a
41104 normal @var{event}. @value{GDBN} shall then send another @var{ack}
41105 packet to solicit further responses; again, it is permitted to send
41106 other, unrelated packets as well which the stub should process
41109 If the stub receives a @var{ack} packet and there are no additional
41110 @var{event} to report, the stub shall return an @samp{OK} response.
41111 At this point, @value{GDBN} has finished processing a notification
41112 and the stub has completed sending any queued events. @value{GDBN}
41113 won't accept any new notifications until the final @samp{OK} is
41114 received . If further notification events occur, the stub shall send
41115 a new notification, @value{GDBN} shall accept the notification, and
41116 the process shall be repeated.
41118 The process of asynchronous notification can be illustrated by the
41121 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
41124 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
41126 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
41131 The following notifications are defined:
41132 @multitable @columnfractions 0.12 0.12 0.38 0.38
41141 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41142 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41143 for information on how these notifications are acknowledged by
41145 @tab Report an asynchronous stop event in non-stop mode.
41149 @node Remote Non-Stop
41150 @section Remote Protocol Support for Non-Stop Mode
41152 @value{GDBN}'s remote protocol supports non-stop debugging of
41153 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41154 supports non-stop mode, it should report that to @value{GDBN} by including
41155 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41157 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41158 establishing a new connection with the stub. Entering non-stop mode
41159 does not alter the state of any currently-running threads, but targets
41160 must stop all threads in any already-attached processes when entering
41161 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41162 probe the target state after a mode change.
41164 In non-stop mode, when an attached process encounters an event that
41165 would otherwise be reported with a stop reply, it uses the
41166 asynchronous notification mechanism (@pxref{Notification Packets}) to
41167 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41168 in all processes are stopped when a stop reply is sent, in non-stop
41169 mode only the thread reporting the stop event is stopped. That is,
41170 when reporting a @samp{S} or @samp{T} response to indicate completion
41171 of a step operation, hitting a breakpoint, or a fault, only the
41172 affected thread is stopped; any other still-running threads continue
41173 to run. When reporting a @samp{W} or @samp{X} response, all running
41174 threads belonging to other attached processes continue to run.
41176 In non-stop mode, the target shall respond to the @samp{?} packet as
41177 follows. First, any incomplete stop reply notification/@samp{vStopped}
41178 sequence in progress is abandoned. The target must begin a new
41179 sequence reporting stop events for all stopped threads, whether or not
41180 it has previously reported those events to @value{GDBN}. The first
41181 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41182 subsequent stop replies are sent as responses to @samp{vStopped} packets
41183 using the mechanism described above. The target must not send
41184 asynchronous stop reply notifications until the sequence is complete.
41185 If all threads are running when the target receives the @samp{?} packet,
41186 or if the target is not attached to any process, it shall respond
41189 @node Packet Acknowledgment
41190 @section Packet Acknowledgment
41192 @cindex acknowledgment, for @value{GDBN} remote
41193 @cindex packet acknowledgment, for @value{GDBN} remote
41194 By default, when either the host or the target machine receives a packet,
41195 the first response expected is an acknowledgment: either @samp{+} (to indicate
41196 the package was received correctly) or @samp{-} (to request retransmission).
41197 This mechanism allows the @value{GDBN} remote protocol to operate over
41198 unreliable transport mechanisms, such as a serial line.
41200 In cases where the transport mechanism is itself reliable (such as a pipe or
41201 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41202 It may be desirable to disable them in that case to reduce communication
41203 overhead, or for other reasons. This can be accomplished by means of the
41204 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41206 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41207 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41208 and response format still includes the normal checksum, as described in
41209 @ref{Overview}, but the checksum may be ignored by the receiver.
41211 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41212 no-acknowledgment mode, it should report that to @value{GDBN}
41213 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41214 @pxref{qSupported}.
41215 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41216 disabled via the @code{set remote noack-packet off} command
41217 (@pxref{Remote Configuration}),
41218 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41219 Only then may the stub actually turn off packet acknowledgments.
41220 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41221 response, which can be safely ignored by the stub.
41223 Note that @code{set remote noack-packet} command only affects negotiation
41224 between @value{GDBN} and the stub when subsequent connections are made;
41225 it does not affect the protocol acknowledgment state for any current
41227 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41228 new connection is established,
41229 there is also no protocol request to re-enable the acknowledgments
41230 for the current connection, once disabled.
41235 Example sequence of a target being re-started. Notice how the restart
41236 does not get any direct output:
41241 @emph{target restarts}
41244 <- @code{T001:1234123412341234}
41248 Example sequence of a target being stepped by a single instruction:
41251 -> @code{G1445@dots{}}
41256 <- @code{T001:1234123412341234}
41260 <- @code{1455@dots{}}
41264 @node File-I/O Remote Protocol Extension
41265 @section File-I/O Remote Protocol Extension
41266 @cindex File-I/O remote protocol extension
41269 * File-I/O Overview::
41270 * Protocol Basics::
41271 * The F Request Packet::
41272 * The F Reply Packet::
41273 * The Ctrl-C Message::
41275 * List of Supported Calls::
41276 * Protocol-specific Representation of Datatypes::
41278 * File-I/O Examples::
41281 @node File-I/O Overview
41282 @subsection File-I/O Overview
41283 @cindex file-i/o overview
41285 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41286 target to use the host's file system and console I/O to perform various
41287 system calls. System calls on the target system are translated into a
41288 remote protocol packet to the host system, which then performs the needed
41289 actions and returns a response packet to the target system.
41290 This simulates file system operations even on targets that lack file systems.
41292 The protocol is defined to be independent of both the host and target systems.
41293 It uses its own internal representation of datatypes and values. Both
41294 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41295 translating the system-dependent value representations into the internal
41296 protocol representations when data is transmitted.
41298 The communication is synchronous. A system call is possible only when
41299 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41300 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41301 the target is stopped to allow deterministic access to the target's
41302 memory. Therefore File-I/O is not interruptible by target signals. On
41303 the other hand, it is possible to interrupt File-I/O by a user interrupt
41304 (@samp{Ctrl-C}) within @value{GDBN}.
41306 The target's request to perform a host system call does not finish
41307 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41308 after finishing the system call, the target returns to continuing the
41309 previous activity (continue, step). No additional continue or step
41310 request from @value{GDBN} is required.
41313 (@value{GDBP}) continue
41314 <- target requests 'system call X'
41315 target is stopped, @value{GDBN} executes system call
41316 -> @value{GDBN} returns result
41317 ... target continues, @value{GDBN} returns to wait for the target
41318 <- target hits breakpoint and sends a Txx packet
41321 The protocol only supports I/O on the console and to regular files on
41322 the host file system. Character or block special devices, pipes,
41323 named pipes, sockets or any other communication method on the host
41324 system are not supported by this protocol.
41326 File I/O is not supported in non-stop mode.
41328 @node Protocol Basics
41329 @subsection Protocol Basics
41330 @cindex protocol basics, file-i/o
41332 The File-I/O protocol uses the @code{F} packet as the request as well
41333 as reply packet. Since a File-I/O system call can only occur when
41334 @value{GDBN} is waiting for a response from the continuing or stepping target,
41335 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41336 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41337 This @code{F} packet contains all information needed to allow @value{GDBN}
41338 to call the appropriate host system call:
41342 A unique identifier for the requested system call.
41345 All parameters to the system call. Pointers are given as addresses
41346 in the target memory address space. Pointers to strings are given as
41347 pointer/length pair. Numerical values are given as they are.
41348 Numerical control flags are given in a protocol-specific representation.
41352 At this point, @value{GDBN} has to perform the following actions.
41356 If the parameters include pointer values to data needed as input to a
41357 system call, @value{GDBN} requests this data from the target with a
41358 standard @code{m} packet request. This additional communication has to be
41359 expected by the target implementation and is handled as any other @code{m}
41363 @value{GDBN} translates all value from protocol representation to host
41364 representation as needed. Datatypes are coerced into the host types.
41367 @value{GDBN} calls the system call.
41370 It then coerces datatypes back to protocol representation.
41373 If the system call is expected to return data in buffer space specified
41374 by pointer parameters to the call, the data is transmitted to the
41375 target using a @code{M} or @code{X} packet. This packet has to be expected
41376 by the target implementation and is handled as any other @code{M} or @code{X}
41381 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41382 necessary information for the target to continue. This at least contains
41389 @code{errno}, if has been changed by the system call.
41396 After having done the needed type and value coercion, the target continues
41397 the latest continue or step action.
41399 @node The F Request Packet
41400 @subsection The @code{F} Request Packet
41401 @cindex file-i/o request packet
41402 @cindex @code{F} request packet
41404 The @code{F} request packet has the following format:
41407 @item F@var{call-id},@var{parameter@dots{}}
41409 @var{call-id} is the identifier to indicate the host system call to be called.
41410 This is just the name of the function.
41412 @var{parameter@dots{}} are the parameters to the system call.
41413 Parameters are hexadecimal integer values, either the actual values in case
41414 of scalar datatypes, pointers to target buffer space in case of compound
41415 datatypes and unspecified memory areas, or pointer/length pairs in case
41416 of string parameters. These are appended to the @var{call-id} as a
41417 comma-delimited list. All values are transmitted in ASCII
41418 string representation, pointer/length pairs separated by a slash.
41424 @node The F Reply Packet
41425 @subsection The @code{F} Reply Packet
41426 @cindex file-i/o reply packet
41427 @cindex @code{F} reply packet
41429 The @code{F} reply packet has the following format:
41433 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41435 @var{retcode} is the return code of the system call as hexadecimal value.
41437 @var{errno} is the @code{errno} set by the call, in protocol-specific
41439 This parameter can be omitted if the call was successful.
41441 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41442 case, @var{errno} must be sent as well, even if the call was successful.
41443 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41450 or, if the call was interrupted before the host call has been performed:
41457 assuming 4 is the protocol-specific representation of @code{EINTR}.
41462 @node The Ctrl-C Message
41463 @subsection The @samp{Ctrl-C} Message
41464 @cindex ctrl-c message, in file-i/o protocol
41466 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41467 reply packet (@pxref{The F Reply Packet}),
41468 the target should behave as if it had
41469 gotten a break message. The meaning for the target is ``system call
41470 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41471 (as with a break message) and return to @value{GDBN} with a @code{T02}
41474 It's important for the target to know in which
41475 state the system call was interrupted. There are two possible cases:
41479 The system call hasn't been performed on the host yet.
41482 The system call on the host has been finished.
41486 These two states can be distinguished by the target by the value of the
41487 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41488 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41489 on POSIX systems. In any other case, the target may presume that the
41490 system call has been finished --- successfully or not --- and should behave
41491 as if the break message arrived right after the system call.
41493 @value{GDBN} must behave reliably. If the system call has not been called
41494 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41495 @code{errno} in the packet. If the system call on the host has been finished
41496 before the user requests a break, the full action must be finished by
41497 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41498 The @code{F} packet may only be sent when either nothing has happened
41499 or the full action has been completed.
41502 @subsection Console I/O
41503 @cindex console i/o as part of file-i/o
41505 By default and if not explicitly closed by the target system, the file
41506 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41507 on the @value{GDBN} console is handled as any other file output operation
41508 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41509 by @value{GDBN} so that after the target read request from file descriptor
41510 0 all following typing is buffered until either one of the following
41515 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41517 system call is treated as finished.
41520 The user presses @key{RET}. This is treated as end of input with a trailing
41524 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41525 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41529 If the user has typed more characters than fit in the buffer given to
41530 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41531 either another @code{read(0, @dots{})} is requested by the target, or debugging
41532 is stopped at the user's request.
41535 @node List of Supported Calls
41536 @subsection List of Supported Calls
41537 @cindex list of supported file-i/o calls
41554 @unnumberedsubsubsec open
41555 @cindex open, file-i/o system call
41560 int open(const char *pathname, int flags);
41561 int open(const char *pathname, int flags, mode_t mode);
41565 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41568 @var{flags} is the bitwise @code{OR} of the following values:
41572 If the file does not exist it will be created. The host
41573 rules apply as far as file ownership and time stamps
41577 When used with @code{O_CREAT}, if the file already exists it is
41578 an error and open() fails.
41581 If the file already exists and the open mode allows
41582 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41583 truncated to zero length.
41586 The file is opened in append mode.
41589 The file is opened for reading only.
41592 The file is opened for writing only.
41595 The file is opened for reading and writing.
41599 Other bits are silently ignored.
41603 @var{mode} is the bitwise @code{OR} of the following values:
41607 User has read permission.
41610 User has write permission.
41613 Group has read permission.
41616 Group has write permission.
41619 Others have read permission.
41622 Others have write permission.
41626 Other bits are silently ignored.
41629 @item Return value:
41630 @code{open} returns the new file descriptor or -1 if an error
41637 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41640 @var{pathname} refers to a directory.
41643 The requested access is not allowed.
41646 @var{pathname} was too long.
41649 A directory component in @var{pathname} does not exist.
41652 @var{pathname} refers to a device, pipe, named pipe or socket.
41655 @var{pathname} refers to a file on a read-only filesystem and
41656 write access was requested.
41659 @var{pathname} is an invalid pointer value.
41662 No space on device to create the file.
41665 The process already has the maximum number of files open.
41668 The limit on the total number of files open on the system
41672 The call was interrupted by the user.
41678 @unnumberedsubsubsec close
41679 @cindex close, file-i/o system call
41688 @samp{Fclose,@var{fd}}
41690 @item Return value:
41691 @code{close} returns zero on success, or -1 if an error occurred.
41697 @var{fd} isn't a valid open file descriptor.
41700 The call was interrupted by the user.
41706 @unnumberedsubsubsec read
41707 @cindex read, file-i/o system call
41712 int read(int fd, void *buf, unsigned int count);
41716 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41718 @item Return value:
41719 On success, the number of bytes read is returned.
41720 Zero indicates end of file. If count is zero, read
41721 returns zero as well. On error, -1 is returned.
41727 @var{fd} is not a valid file descriptor or is not open for
41731 @var{bufptr} is an invalid pointer value.
41734 The call was interrupted by the user.
41740 @unnumberedsubsubsec write
41741 @cindex write, file-i/o system call
41746 int write(int fd, const void *buf, unsigned int count);
41750 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41752 @item Return value:
41753 On success, the number of bytes written are returned.
41754 Zero indicates nothing was written. On error, -1
41761 @var{fd} is not a valid file descriptor or is not open for
41765 @var{bufptr} is an invalid pointer value.
41768 An attempt was made to write a file that exceeds the
41769 host-specific maximum file size allowed.
41772 No space on device to write the data.
41775 The call was interrupted by the user.
41781 @unnumberedsubsubsec lseek
41782 @cindex lseek, file-i/o system call
41787 long lseek (int fd, long offset, int flag);
41791 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41793 @var{flag} is one of:
41797 The offset is set to @var{offset} bytes.
41800 The offset is set to its current location plus @var{offset}
41804 The offset is set to the size of the file plus @var{offset}
41808 @item Return value:
41809 On success, the resulting unsigned offset in bytes from
41810 the beginning of the file is returned. Otherwise, a
41811 value of -1 is returned.
41817 @var{fd} is not a valid open file descriptor.
41820 @var{fd} is associated with the @value{GDBN} console.
41823 @var{flag} is not a proper value.
41826 The call was interrupted by the user.
41832 @unnumberedsubsubsec rename
41833 @cindex rename, file-i/o system call
41838 int rename(const char *oldpath, const char *newpath);
41842 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41844 @item Return value:
41845 On success, zero is returned. On error, -1 is returned.
41851 @var{newpath} is an existing directory, but @var{oldpath} is not a
41855 @var{newpath} is a non-empty directory.
41858 @var{oldpath} or @var{newpath} is a directory that is in use by some
41862 An attempt was made to make a directory a subdirectory
41866 A component used as a directory in @var{oldpath} or new
41867 path is not a directory. Or @var{oldpath} is a directory
41868 and @var{newpath} exists but is not a directory.
41871 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41874 No access to the file or the path of the file.
41878 @var{oldpath} or @var{newpath} was too long.
41881 A directory component in @var{oldpath} or @var{newpath} does not exist.
41884 The file is on a read-only filesystem.
41887 The device containing the file has no room for the new
41891 The call was interrupted by the user.
41897 @unnumberedsubsubsec unlink
41898 @cindex unlink, file-i/o system call
41903 int unlink(const char *pathname);
41907 @samp{Funlink,@var{pathnameptr}/@var{len}}
41909 @item Return value:
41910 On success, zero is returned. On error, -1 is returned.
41916 No access to the file or the path of the file.
41919 The system does not allow unlinking of directories.
41922 The file @var{pathname} cannot be unlinked because it's
41923 being used by another process.
41926 @var{pathnameptr} is an invalid pointer value.
41929 @var{pathname} was too long.
41932 A directory component in @var{pathname} does not exist.
41935 A component of the path is not a directory.
41938 The file is on a read-only filesystem.
41941 The call was interrupted by the user.
41947 @unnumberedsubsubsec stat/fstat
41948 @cindex fstat, file-i/o system call
41949 @cindex stat, file-i/o system call
41954 int stat(const char *pathname, struct stat *buf);
41955 int fstat(int fd, struct stat *buf);
41959 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41960 @samp{Ffstat,@var{fd},@var{bufptr}}
41962 @item Return value:
41963 On success, zero is returned. On error, -1 is returned.
41969 @var{fd} is not a valid open file.
41972 A directory component in @var{pathname} does not exist or the
41973 path is an empty string.
41976 A component of the path is not a directory.
41979 @var{pathnameptr} is an invalid pointer value.
41982 No access to the file or the path of the file.
41985 @var{pathname} was too long.
41988 The call was interrupted by the user.
41994 @unnumberedsubsubsec gettimeofday
41995 @cindex gettimeofday, file-i/o system call
42000 int gettimeofday(struct timeval *tv, void *tz);
42004 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
42006 @item Return value:
42007 On success, 0 is returned, -1 otherwise.
42013 @var{tz} is a non-NULL pointer.
42016 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
42022 @unnumberedsubsubsec isatty
42023 @cindex isatty, file-i/o system call
42028 int isatty(int fd);
42032 @samp{Fisatty,@var{fd}}
42034 @item Return value:
42035 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
42041 The call was interrupted by the user.
42046 Note that the @code{isatty} call is treated as a special case: it returns
42047 1 to the target if the file descriptor is attached
42048 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
42049 would require implementing @code{ioctl} and would be more complex than
42054 @unnumberedsubsubsec system
42055 @cindex system, file-i/o system call
42060 int system(const char *command);
42064 @samp{Fsystem,@var{commandptr}/@var{len}}
42066 @item Return value:
42067 If @var{len} is zero, the return value indicates whether a shell is
42068 available. A zero return value indicates a shell is not available.
42069 For non-zero @var{len}, the value returned is -1 on error and the
42070 return status of the command otherwise. Only the exit status of the
42071 command is returned, which is extracted from the host's @code{system}
42072 return value by calling @code{WEXITSTATUS(retval)}. In case
42073 @file{/bin/sh} could not be executed, 127 is returned.
42079 The call was interrupted by the user.
42084 @value{GDBN} takes over the full task of calling the necessary host calls
42085 to perform the @code{system} call. The return value of @code{system} on
42086 the host is simplified before it's returned
42087 to the target. Any termination signal information from the child process
42088 is discarded, and the return value consists
42089 entirely of the exit status of the called command.
42091 Due to security concerns, the @code{system} call is by default refused
42092 by @value{GDBN}. The user has to allow this call explicitly with the
42093 @code{set remote system-call-allowed 1} command.
42096 @item set remote system-call-allowed
42097 @kindex set remote system-call-allowed
42098 Control whether to allow the @code{system} calls in the File I/O
42099 protocol for the remote target. The default is zero (disabled).
42101 @item show remote system-call-allowed
42102 @kindex show remote system-call-allowed
42103 Show whether the @code{system} calls are allowed in the File I/O
42107 @node Protocol-specific Representation of Datatypes
42108 @subsection Protocol-specific Representation of Datatypes
42109 @cindex protocol-specific representation of datatypes, in file-i/o protocol
42112 * Integral Datatypes::
42114 * Memory Transfer::
42119 @node Integral Datatypes
42120 @unnumberedsubsubsec Integral Datatypes
42121 @cindex integral datatypes, in file-i/o protocol
42123 The integral datatypes used in the system calls are @code{int},
42124 @code{unsigned int}, @code{long}, @code{unsigned long},
42125 @code{mode_t}, and @code{time_t}.
42127 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42128 implemented as 32 bit values in this protocol.
42130 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42132 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42133 in @file{limits.h}) to allow range checking on host and target.
42135 @code{time_t} datatypes are defined as seconds since the Epoch.
42137 All integral datatypes transferred as part of a memory read or write of a
42138 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42141 @node Pointer Values
42142 @unnumberedsubsubsec Pointer Values
42143 @cindex pointer values, in file-i/o protocol
42145 Pointers to target data are transmitted as they are. An exception
42146 is made for pointers to buffers for which the length isn't
42147 transmitted as part of the function call, namely strings. Strings
42148 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42155 which is a pointer to data of length 18 bytes at position 0x1aaf.
42156 The length is defined as the full string length in bytes, including
42157 the trailing null byte. For example, the string @code{"hello world"}
42158 at address 0x123456 is transmitted as
42164 @node Memory Transfer
42165 @unnumberedsubsubsec Memory Transfer
42166 @cindex memory transfer, in file-i/o protocol
42168 Structured data which is transferred using a memory read or write (for
42169 example, a @code{struct stat}) is expected to be in a protocol-specific format
42170 with all scalar multibyte datatypes being big endian. Translation to
42171 this representation needs to be done both by the target before the @code{F}
42172 packet is sent, and by @value{GDBN} before
42173 it transfers memory to the target. Transferred pointers to structured
42174 data should point to the already-coerced data at any time.
42178 @unnumberedsubsubsec struct stat
42179 @cindex struct stat, in file-i/o protocol
42181 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42182 is defined as follows:
42186 unsigned int st_dev; /* device */
42187 unsigned int st_ino; /* inode */
42188 mode_t st_mode; /* protection */
42189 unsigned int st_nlink; /* number of hard links */
42190 unsigned int st_uid; /* user ID of owner */
42191 unsigned int st_gid; /* group ID of owner */
42192 unsigned int st_rdev; /* device type (if inode device) */
42193 unsigned long st_size; /* total size, in bytes */
42194 unsigned long st_blksize; /* blocksize for filesystem I/O */
42195 unsigned long st_blocks; /* number of blocks allocated */
42196 time_t st_atime; /* time of last access */
42197 time_t st_mtime; /* time of last modification */
42198 time_t st_ctime; /* time of last change */
42202 The integral datatypes conform to the definitions given in the
42203 appropriate section (see @ref{Integral Datatypes}, for details) so this
42204 structure is of size 64 bytes.
42206 The values of several fields have a restricted meaning and/or
42212 A value of 0 represents a file, 1 the console.
42215 No valid meaning for the target. Transmitted unchanged.
42218 Valid mode bits are described in @ref{Constants}. Any other
42219 bits have currently no meaning for the target.
42224 No valid meaning for the target. Transmitted unchanged.
42229 These values have a host and file system dependent
42230 accuracy. Especially on Windows hosts, the file system may not
42231 support exact timing values.
42234 The target gets a @code{struct stat} of the above representation and is
42235 responsible for coercing it to the target representation before
42238 Note that due to size differences between the host, target, and protocol
42239 representations of @code{struct stat} members, these members could eventually
42240 get truncated on the target.
42242 @node struct timeval
42243 @unnumberedsubsubsec struct timeval
42244 @cindex struct timeval, in file-i/o protocol
42246 The buffer of type @code{struct timeval} used by the File-I/O protocol
42247 is defined as follows:
42251 time_t tv_sec; /* second */
42252 long tv_usec; /* microsecond */
42256 The integral datatypes conform to the definitions given in the
42257 appropriate section (see @ref{Integral Datatypes}, for details) so this
42258 structure is of size 8 bytes.
42261 @subsection Constants
42262 @cindex constants, in file-i/o protocol
42264 The following values are used for the constants inside of the
42265 protocol. @value{GDBN} and target are responsible for translating these
42266 values before and after the call as needed.
42277 @unnumberedsubsubsec Open Flags
42278 @cindex open flags, in file-i/o protocol
42280 All values are given in hexadecimal representation.
42292 @node mode_t Values
42293 @unnumberedsubsubsec mode_t Values
42294 @cindex mode_t values, in file-i/o protocol
42296 All values are given in octal representation.
42313 @unnumberedsubsubsec Errno Values
42314 @cindex errno values, in file-i/o protocol
42316 All values are given in decimal representation.
42341 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42342 any error value not in the list of supported error numbers.
42345 @unnumberedsubsubsec Lseek Flags
42346 @cindex lseek flags, in file-i/o protocol
42355 @unnumberedsubsubsec Limits
42356 @cindex limits, in file-i/o protocol
42358 All values are given in decimal representation.
42361 INT_MIN -2147483648
42363 UINT_MAX 4294967295
42364 LONG_MIN -9223372036854775808
42365 LONG_MAX 9223372036854775807
42366 ULONG_MAX 18446744073709551615
42369 @node File-I/O Examples
42370 @subsection File-I/O Examples
42371 @cindex file-i/o examples
42373 Example sequence of a write call, file descriptor 3, buffer is at target
42374 address 0x1234, 6 bytes should be written:
42377 <- @code{Fwrite,3,1234,6}
42378 @emph{request memory read from target}
42381 @emph{return "6 bytes written"}
42385 Example sequence of a read call, file descriptor 3, buffer is at target
42386 address 0x1234, 6 bytes should be read:
42389 <- @code{Fread,3,1234,6}
42390 @emph{request memory write to target}
42391 -> @code{X1234,6:XXXXXX}
42392 @emph{return "6 bytes read"}
42396 Example sequence of a read call, call fails on the host due to invalid
42397 file descriptor (@code{EBADF}):
42400 <- @code{Fread,3,1234,6}
42404 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42408 <- @code{Fread,3,1234,6}
42413 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42417 <- @code{Fread,3,1234,6}
42418 -> @code{X1234,6:XXXXXX}
42422 @node Library List Format
42423 @section Library List Format
42424 @cindex library list format, remote protocol
42426 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42427 same process as your application to manage libraries. In this case,
42428 @value{GDBN} can use the loader's symbol table and normal memory
42429 operations to maintain a list of shared libraries. On other
42430 platforms, the operating system manages loaded libraries.
42431 @value{GDBN} can not retrieve the list of currently loaded libraries
42432 through memory operations, so it uses the @samp{qXfer:libraries:read}
42433 packet (@pxref{qXfer library list read}) instead. The remote stub
42434 queries the target's operating system and reports which libraries
42437 The @samp{qXfer:libraries:read} packet returns an XML document which
42438 lists loaded libraries and their offsets. Each library has an
42439 associated name and one or more segment or section base addresses,
42440 which report where the library was loaded in memory.
42442 For the common case of libraries that are fully linked binaries, the
42443 library should have a list of segments. If the target supports
42444 dynamic linking of a relocatable object file, its library XML element
42445 should instead include a list of allocated sections. The segment or
42446 section bases are start addresses, not relocation offsets; they do not
42447 depend on the library's link-time base addresses.
42449 @value{GDBN} must be linked with the Expat library to support XML
42450 library lists. @xref{Expat}.
42452 A simple memory map, with one loaded library relocated by a single
42453 offset, looks like this:
42457 <library name="/lib/libc.so.6">
42458 <segment address="0x10000000"/>
42463 Another simple memory map, with one loaded library with three
42464 allocated sections (.text, .data, .bss), looks like this:
42468 <library name="sharedlib.o">
42469 <section address="0x10000000"/>
42470 <section address="0x20000000"/>
42471 <section address="0x30000000"/>
42476 The format of a library list is described by this DTD:
42479 <!-- library-list: Root element with versioning -->
42480 <!ELEMENT library-list (library)*>
42481 <!ATTLIST library-list version CDATA #FIXED "1.0">
42482 <!ELEMENT library (segment*, section*)>
42483 <!ATTLIST library name CDATA #REQUIRED>
42484 <!ELEMENT segment EMPTY>
42485 <!ATTLIST segment address CDATA #REQUIRED>
42486 <!ELEMENT section EMPTY>
42487 <!ATTLIST section address CDATA #REQUIRED>
42490 In addition, segments and section descriptors cannot be mixed within a
42491 single library element, and you must supply at least one segment or
42492 section for each library.
42494 @node Library List Format for SVR4 Targets
42495 @section Library List Format for SVR4 Targets
42496 @cindex library list format, remote protocol
42498 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42499 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42500 shared libraries. Still a special library list provided by this packet is
42501 more efficient for the @value{GDBN} remote protocol.
42503 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42504 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42505 target, the following parameters are reported:
42509 @code{name}, the absolute file name from the @code{l_name} field of
42510 @code{struct link_map}.
42512 @code{lm} with address of @code{struct link_map} used for TLS
42513 (Thread Local Storage) access.
42515 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42516 @code{struct link_map}. For prelinked libraries this is not an absolute
42517 memory address. It is a displacement of absolute memory address against
42518 address the file was prelinked to during the library load.
42520 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42523 Additionally the single @code{main-lm} attribute specifies address of
42524 @code{struct link_map} used for the main executable. This parameter is used
42525 for TLS access and its presence is optional.
42527 @value{GDBN} must be linked with the Expat library to support XML
42528 SVR4 library lists. @xref{Expat}.
42530 A simple memory map, with two loaded libraries (which do not use prelink),
42534 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42535 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42537 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42539 </library-list-svr>
42542 The format of an SVR4 library list is described by this DTD:
42545 <!-- library-list-svr4: Root element with versioning -->
42546 <!ELEMENT library-list-svr4 (library)*>
42547 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42548 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42549 <!ELEMENT library EMPTY>
42550 <!ATTLIST library name CDATA #REQUIRED>
42551 <!ATTLIST library lm CDATA #REQUIRED>
42552 <!ATTLIST library l_addr CDATA #REQUIRED>
42553 <!ATTLIST library l_ld CDATA #REQUIRED>
42556 @node Memory Map Format
42557 @section Memory Map Format
42558 @cindex memory map format
42560 To be able to write into flash memory, @value{GDBN} needs to obtain a
42561 memory map from the target. This section describes the format of the
42564 The memory map is obtained using the @samp{qXfer:memory-map:read}
42565 (@pxref{qXfer memory map read}) packet and is an XML document that
42566 lists memory regions.
42568 @value{GDBN} must be linked with the Expat library to support XML
42569 memory maps. @xref{Expat}.
42571 The top-level structure of the document is shown below:
42574 <?xml version="1.0"?>
42575 <!DOCTYPE memory-map
42576 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42577 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42583 Each region can be either:
42588 A region of RAM starting at @var{addr} and extending for @var{length}
42592 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42597 A region of read-only memory:
42600 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42605 A region of flash memory, with erasure blocks @var{blocksize}
42609 <memory type="flash" start="@var{addr}" length="@var{length}">
42610 <property name="blocksize">@var{blocksize}</property>
42616 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42617 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42618 packets to write to addresses in such ranges.
42620 The formal DTD for memory map format is given below:
42623 <!-- ................................................... -->
42624 <!-- Memory Map XML DTD ................................ -->
42625 <!-- File: memory-map.dtd .............................. -->
42626 <!-- .................................... .............. -->
42627 <!-- memory-map.dtd -->
42628 <!-- memory-map: Root element with versioning -->
42629 <!ELEMENT memory-map (memory | property)>
42630 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42631 <!ELEMENT memory (property)>
42632 <!-- memory: Specifies a memory region,
42633 and its type, or device. -->
42634 <!ATTLIST memory type CDATA #REQUIRED
42635 start CDATA #REQUIRED
42636 length CDATA #REQUIRED
42637 device CDATA #IMPLIED>
42638 <!-- property: Generic attribute tag -->
42639 <!ELEMENT property (#PCDATA | property)*>
42640 <!ATTLIST property name CDATA #REQUIRED>
42643 @node Thread List Format
42644 @section Thread List Format
42645 @cindex thread list format
42647 To efficiently update the list of threads and their attributes,
42648 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42649 (@pxref{qXfer threads read}) and obtains the XML document with
42650 the following structure:
42653 <?xml version="1.0"?>
42655 <thread id="id" core="0">
42656 ... description ...
42661 Each @samp{thread} element must have the @samp{id} attribute that
42662 identifies the thread (@pxref{thread-id syntax}). The
42663 @samp{core} attribute, if present, specifies which processor core
42664 the thread was last executing on. The content of the of @samp{thread}
42665 element is interpreted as human-readable auxilliary information.
42667 @node Traceframe Info Format
42668 @section Traceframe Info Format
42669 @cindex traceframe info format
42671 To be able to know which objects in the inferior can be examined when
42672 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42673 memory ranges, registers and trace state variables that have been
42674 collected in a traceframe.
42676 This list is obtained using the @samp{qXfer:traceframe-info:read}
42677 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42679 @value{GDBN} must be linked with the Expat library to support XML
42680 traceframe info discovery. @xref{Expat}.
42682 The top-level structure of the document is shown below:
42685 <?xml version="1.0"?>
42686 <!DOCTYPE traceframe-info
42687 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42688 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42694 Each traceframe block can be either:
42699 A region of collected memory starting at @var{addr} and extending for
42700 @var{length} bytes from there:
42703 <memory start="@var{addr}" length="@var{length}"/>
42707 A block indicating trace state variable numbered @var{number} has been
42711 <tvar id="@var{number}"/>
42716 The formal DTD for the traceframe info format is given below:
42719 <!ELEMENT traceframe-info (memory | tvar)* >
42720 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42722 <!ELEMENT memory EMPTY>
42723 <!ATTLIST memory start CDATA #REQUIRED
42724 length CDATA #REQUIRED>
42726 <!ATTLIST tvar id CDATA #REQUIRED>
42729 @node Branch Trace Format
42730 @section Branch Trace Format
42731 @cindex branch trace format
42733 In order to display the branch trace of an inferior thread,
42734 @value{GDBN} needs to obtain the list of branches. This list is
42735 represented as list of sequential code blocks that are connected via
42736 branches. The code in each block has been executed sequentially.
42738 This list is obtained using the @samp{qXfer:btrace:read}
42739 (@pxref{qXfer btrace read}) packet and is an XML document.
42741 @value{GDBN} must be linked with the Expat library to support XML
42742 traceframe info discovery. @xref{Expat}.
42744 The top-level structure of the document is shown below:
42747 <?xml version="1.0"?>
42749 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42750 "http://sourceware.org/gdb/gdb-btrace.dtd">
42759 A block of sequentially executed instructions starting at @var{begin}
42760 and ending at @var{end}:
42763 <block begin="@var{begin}" end="@var{end}"/>
42768 The formal DTD for the branch trace format is given below:
42771 <!ELEMENT btrace (block)* >
42772 <!ATTLIST btrace version CDATA #FIXED "1.0">
42774 <!ELEMENT block EMPTY>
42775 <!ATTLIST block begin CDATA #REQUIRED
42776 end CDATA #REQUIRED>
42779 @include agentexpr.texi
42781 @node Target Descriptions
42782 @appendix Target Descriptions
42783 @cindex target descriptions
42785 One of the challenges of using @value{GDBN} to debug embedded systems
42786 is that there are so many minor variants of each processor
42787 architecture in use. It is common practice for vendors to start with
42788 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42789 and then make changes to adapt it to a particular market niche. Some
42790 architectures have hundreds of variants, available from dozens of
42791 vendors. This leads to a number of problems:
42795 With so many different customized processors, it is difficult for
42796 the @value{GDBN} maintainers to keep up with the changes.
42798 Since individual variants may have short lifetimes or limited
42799 audiences, it may not be worthwhile to carry information about every
42800 variant in the @value{GDBN} source tree.
42802 When @value{GDBN} does support the architecture of the embedded system
42803 at hand, the task of finding the correct architecture name to give the
42804 @command{set architecture} command can be error-prone.
42807 To address these problems, the @value{GDBN} remote protocol allows a
42808 target system to not only identify itself to @value{GDBN}, but to
42809 actually describe its own features. This lets @value{GDBN} support
42810 processor variants it has never seen before --- to the extent that the
42811 descriptions are accurate, and that @value{GDBN} understands them.
42813 @value{GDBN} must be linked with the Expat library to support XML
42814 target descriptions. @xref{Expat}.
42817 * Retrieving Descriptions:: How descriptions are fetched from a target.
42818 * Target Description Format:: The contents of a target description.
42819 * Predefined Target Types:: Standard types available for target
42821 * Standard Target Features:: Features @value{GDBN} knows about.
42824 @node Retrieving Descriptions
42825 @section Retrieving Descriptions
42827 Target descriptions can be read from the target automatically, or
42828 specified by the user manually. The default behavior is to read the
42829 description from the target. @value{GDBN} retrieves it via the remote
42830 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42831 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42832 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42833 XML document, of the form described in @ref{Target Description
42836 Alternatively, you can specify a file to read for the target description.
42837 If a file is set, the target will not be queried. The commands to
42838 specify a file are:
42841 @cindex set tdesc filename
42842 @item set tdesc filename @var{path}
42843 Read the target description from @var{path}.
42845 @cindex unset tdesc filename
42846 @item unset tdesc filename
42847 Do not read the XML target description from a file. @value{GDBN}
42848 will use the description supplied by the current target.
42850 @cindex show tdesc filename
42851 @item show tdesc filename
42852 Show the filename to read for a target description, if any.
42856 @node Target Description Format
42857 @section Target Description Format
42858 @cindex target descriptions, XML format
42860 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42861 document which complies with the Document Type Definition provided in
42862 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42863 means you can use generally available tools like @command{xmllint} to
42864 check that your feature descriptions are well-formed and valid.
42865 However, to help people unfamiliar with XML write descriptions for
42866 their targets, we also describe the grammar here.
42868 Target descriptions can identify the architecture of the remote target
42869 and (for some architectures) provide information about custom register
42870 sets. They can also identify the OS ABI of the remote target.
42871 @value{GDBN} can use this information to autoconfigure for your
42872 target, or to warn you if you connect to an unsupported target.
42874 Here is a simple target description:
42877 <target version="1.0">
42878 <architecture>i386:x86-64</architecture>
42883 This minimal description only says that the target uses
42884 the x86-64 architecture.
42886 A target description has the following overall form, with [ ] marking
42887 optional elements and @dots{} marking repeatable elements. The elements
42888 are explained further below.
42891 <?xml version="1.0"?>
42892 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42893 <target version="1.0">
42894 @r{[}@var{architecture}@r{]}
42895 @r{[}@var{osabi}@r{]}
42896 @r{[}@var{compatible}@r{]}
42897 @r{[}@var{feature}@dots{}@r{]}
42902 The description is generally insensitive to whitespace and line
42903 breaks, under the usual common-sense rules. The XML version
42904 declaration and document type declaration can generally be omitted
42905 (@value{GDBN} does not require them), but specifying them may be
42906 useful for XML validation tools. The @samp{version} attribute for
42907 @samp{<target>} may also be omitted, but we recommend
42908 including it; if future versions of @value{GDBN} use an incompatible
42909 revision of @file{gdb-target.dtd}, they will detect and report
42910 the version mismatch.
42912 @subsection Inclusion
42913 @cindex target descriptions, inclusion
42916 @cindex <xi:include>
42919 It can sometimes be valuable to split a target description up into
42920 several different annexes, either for organizational purposes, or to
42921 share files between different possible target descriptions. You can
42922 divide a description into multiple files by replacing any element of
42923 the target description with an inclusion directive of the form:
42926 <xi:include href="@var{document}"/>
42930 When @value{GDBN} encounters an element of this form, it will retrieve
42931 the named XML @var{document}, and replace the inclusion directive with
42932 the contents of that document. If the current description was read
42933 using @samp{qXfer}, then so will be the included document;
42934 @var{document} will be interpreted as the name of an annex. If the
42935 current description was read from a file, @value{GDBN} will look for
42936 @var{document} as a file in the same directory where it found the
42937 original description.
42939 @subsection Architecture
42940 @cindex <architecture>
42942 An @samp{<architecture>} element has this form:
42945 <architecture>@var{arch}</architecture>
42948 @var{arch} is one of the architectures from the set accepted by
42949 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42952 @cindex @code{<osabi>}
42954 This optional field was introduced in @value{GDBN} version 7.0.
42955 Previous versions of @value{GDBN} ignore it.
42957 An @samp{<osabi>} element has this form:
42960 <osabi>@var{abi-name}</osabi>
42963 @var{abi-name} is an OS ABI name from the same selection accepted by
42964 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42966 @subsection Compatible Architecture
42967 @cindex @code{<compatible>}
42969 This optional field was introduced in @value{GDBN} version 7.0.
42970 Previous versions of @value{GDBN} ignore it.
42972 A @samp{<compatible>} element has this form:
42975 <compatible>@var{arch}</compatible>
42978 @var{arch} is one of the architectures from the set accepted by
42979 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42981 A @samp{<compatible>} element is used to specify that the target
42982 is able to run binaries in some other than the main target architecture
42983 given by the @samp{<architecture>} element. For example, on the
42984 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42985 or @code{powerpc:common64}, but the system is able to run binaries
42986 in the @code{spu} architecture as well. The way to describe this
42987 capability with @samp{<compatible>} is as follows:
42990 <architecture>powerpc:common</architecture>
42991 <compatible>spu</compatible>
42994 @subsection Features
42997 Each @samp{<feature>} describes some logical portion of the target
42998 system. Features are currently used to describe available CPU
42999 registers and the types of their contents. A @samp{<feature>} element
43003 <feature name="@var{name}">
43004 @r{[}@var{type}@dots{}@r{]}
43010 Each feature's name should be unique within the description. The name
43011 of a feature does not matter unless @value{GDBN} has some special
43012 knowledge of the contents of that feature; if it does, the feature
43013 should have its standard name. @xref{Standard Target Features}.
43017 Any register's value is a collection of bits which @value{GDBN} must
43018 interpret. The default interpretation is a two's complement integer,
43019 but other types can be requested by name in the register description.
43020 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
43021 Target Types}), and the description can define additional composite types.
43023 Each type element must have an @samp{id} attribute, which gives
43024 a unique (within the containing @samp{<feature>}) name to the type.
43025 Types must be defined before they are used.
43028 Some targets offer vector registers, which can be treated as arrays
43029 of scalar elements. These types are written as @samp{<vector>} elements,
43030 specifying the array element type, @var{type}, and the number of elements,
43034 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
43038 If a register's value is usefully viewed in multiple ways, define it
43039 with a union type containing the useful representations. The
43040 @samp{<union>} element contains one or more @samp{<field>} elements,
43041 each of which has a @var{name} and a @var{type}:
43044 <union id="@var{id}">
43045 <field name="@var{name}" type="@var{type}"/>
43051 If a register's value is composed from several separate values, define
43052 it with a structure type. There are two forms of the @samp{<struct>}
43053 element; a @samp{<struct>} element must either contain only bitfields
43054 or contain no bitfields. If the structure contains only bitfields,
43055 its total size in bytes must be specified, each bitfield must have an
43056 explicit start and end, and bitfields are automatically assigned an
43057 integer type. The field's @var{start} should be less than or
43058 equal to its @var{end}, and zero represents the least significant bit.
43061 <struct id="@var{id}" size="@var{size}">
43062 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43067 If the structure contains no bitfields, then each field has an
43068 explicit type, and no implicit padding is added.
43071 <struct id="@var{id}">
43072 <field name="@var{name}" type="@var{type}"/>
43078 If a register's value is a series of single-bit flags, define it with
43079 a flags type. The @samp{<flags>} element has an explicit @var{size}
43080 and contains one or more @samp{<field>} elements. Each field has a
43081 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
43085 <flags id="@var{id}" size="@var{size}">
43086 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43091 @subsection Registers
43094 Each register is represented as an element with this form:
43097 <reg name="@var{name}"
43098 bitsize="@var{size}"
43099 @r{[}regnum="@var{num}"@r{]}
43100 @r{[}save-restore="@var{save-restore}"@r{]}
43101 @r{[}type="@var{type}"@r{]}
43102 @r{[}group="@var{group}"@r{]}/>
43106 The components are as follows:
43111 The register's name; it must be unique within the target description.
43114 The register's size, in bits.
43117 The register's number. If omitted, a register's number is one greater
43118 than that of the previous register (either in the current feature or in
43119 a preceding feature); the first register in the target description
43120 defaults to zero. This register number is used to read or write
43121 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43122 packets, and registers appear in the @code{g} and @code{G} packets
43123 in order of increasing register number.
43126 Whether the register should be preserved across inferior function
43127 calls; this must be either @code{yes} or @code{no}. The default is
43128 @code{yes}, which is appropriate for most registers except for
43129 some system control registers; this is not related to the target's
43133 The type of the register. @var{type} may be a predefined type, a type
43134 defined in the current feature, or one of the special types @code{int}
43135 and @code{float}. @code{int} is an integer type of the correct size
43136 for @var{bitsize}, and @code{float} is a floating point type (in the
43137 architecture's normal floating point format) of the correct size for
43138 @var{bitsize}. The default is @code{int}.
43141 The register group to which this register belongs. @var{group} must
43142 be either @code{general}, @code{float}, or @code{vector}. If no
43143 @var{group} is specified, @value{GDBN} will not display the register
43144 in @code{info registers}.
43148 @node Predefined Target Types
43149 @section Predefined Target Types
43150 @cindex target descriptions, predefined types
43152 Type definitions in the self-description can build up composite types
43153 from basic building blocks, but can not define fundamental types. Instead,
43154 standard identifiers are provided by @value{GDBN} for the fundamental
43155 types. The currently supported types are:
43164 Signed integer types holding the specified number of bits.
43171 Unsigned integer types holding the specified number of bits.
43175 Pointers to unspecified code and data. The program counter and
43176 any dedicated return address register may be marked as code
43177 pointers; printing a code pointer converts it into a symbolic
43178 address. The stack pointer and any dedicated address registers
43179 may be marked as data pointers.
43182 Single precision IEEE floating point.
43185 Double precision IEEE floating point.
43188 The 12-byte extended precision format used by ARM FPA registers.
43191 The 10-byte extended precision format used by x87 registers.
43194 32bit @sc{eflags} register used by x86.
43197 32bit @sc{mxcsr} register used by x86.
43201 @node Standard Target Features
43202 @section Standard Target Features
43203 @cindex target descriptions, standard features
43205 A target description must contain either no registers or all the
43206 target's registers. If the description contains no registers, then
43207 @value{GDBN} will assume a default register layout, selected based on
43208 the architecture. If the description contains any registers, the
43209 default layout will not be used; the standard registers must be
43210 described in the target description, in such a way that @value{GDBN}
43211 can recognize them.
43213 This is accomplished by giving specific names to feature elements
43214 which contain standard registers. @value{GDBN} will look for features
43215 with those names and verify that they contain the expected registers;
43216 if any known feature is missing required registers, or if any required
43217 feature is missing, @value{GDBN} will reject the target
43218 description. You can add additional registers to any of the
43219 standard features --- @value{GDBN} will display them just as if
43220 they were added to an unrecognized feature.
43222 This section lists the known features and their expected contents.
43223 Sample XML documents for these features are included in the
43224 @value{GDBN} source tree, in the directory @file{gdb/features}.
43226 Names recognized by @value{GDBN} should include the name of the
43227 company or organization which selected the name, and the overall
43228 architecture to which the feature applies; so e.g.@: the feature
43229 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43231 The names of registers are not case sensitive for the purpose
43232 of recognizing standard features, but @value{GDBN} will only display
43233 registers using the capitalization used in the description.
43236 * AArch64 Features::
43241 * Nios II Features::
43242 * PowerPC Features::
43243 * S/390 and System z Features::
43248 @node AArch64 Features
43249 @subsection AArch64 Features
43250 @cindex target descriptions, AArch64 features
43252 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43253 targets. It should contain registers @samp{x0} through @samp{x30},
43254 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43256 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43257 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43261 @subsection ARM Features
43262 @cindex target descriptions, ARM features
43264 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43266 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43267 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43269 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43270 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43271 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43274 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43275 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43277 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43278 it should contain at least registers @samp{wR0} through @samp{wR15} and
43279 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43280 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43282 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43283 should contain at least registers @samp{d0} through @samp{d15}. If
43284 they are present, @samp{d16} through @samp{d31} should also be included.
43285 @value{GDBN} will synthesize the single-precision registers from
43286 halves of the double-precision registers.
43288 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43289 need to contain registers; it instructs @value{GDBN} to display the
43290 VFP double-precision registers as vectors and to synthesize the
43291 quad-precision registers from pairs of double-precision registers.
43292 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43293 be present and include 32 double-precision registers.
43295 @node i386 Features
43296 @subsection i386 Features
43297 @cindex target descriptions, i386 features
43299 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43300 targets. It should describe the following registers:
43304 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43306 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43308 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43309 @samp{fs}, @samp{gs}
43311 @samp{st0} through @samp{st7}
43313 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43314 @samp{foseg}, @samp{fooff} and @samp{fop}
43317 The register sets may be different, depending on the target.
43319 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43320 describe registers:
43324 @samp{xmm0} through @samp{xmm7} for i386
43326 @samp{xmm0} through @samp{xmm15} for amd64
43331 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43332 @samp{org.gnu.gdb.i386.sse} feature. It should
43333 describe the upper 128 bits of @sc{ymm} registers:
43337 @samp{ymm0h} through @samp{ymm7h} for i386
43339 @samp{ymm0h} through @samp{ymm15h} for amd64
43342 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
43343 Memory Protection Extension (MPX). It should describe the following registers:
43347 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43349 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43352 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43353 describe a single register, @samp{orig_eax}.
43355 @node MIPS Features
43356 @subsection @acronym{MIPS} Features
43357 @cindex target descriptions, @acronym{MIPS} features
43359 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43360 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43361 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43364 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43365 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43366 registers. They may be 32-bit or 64-bit depending on the target.
43368 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43369 it may be optional in a future version of @value{GDBN}. It should
43370 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43371 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43373 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43374 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43375 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43376 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43378 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43379 contain a single register, @samp{restart}, which is used by the
43380 Linux kernel to control restartable syscalls.
43382 @node M68K Features
43383 @subsection M68K Features
43384 @cindex target descriptions, M68K features
43387 @item @samp{org.gnu.gdb.m68k.core}
43388 @itemx @samp{org.gnu.gdb.coldfire.core}
43389 @itemx @samp{org.gnu.gdb.fido.core}
43390 One of those features must be always present.
43391 The feature that is present determines which flavor of m68k is
43392 used. The feature that is present should contain registers
43393 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43394 @samp{sp}, @samp{ps} and @samp{pc}.
43396 @item @samp{org.gnu.gdb.coldfire.fp}
43397 This feature is optional. If present, it should contain registers
43398 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43402 @node Nios II Features
43403 @subsection Nios II Features
43404 @cindex target descriptions, Nios II features
43406 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43407 targets. It should contain the 32 core registers (@samp{zero},
43408 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43409 @samp{pc}, and the 16 control registers (@samp{status} through
43412 @node PowerPC Features
43413 @subsection PowerPC Features
43414 @cindex target descriptions, PowerPC features
43416 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43417 targets. It should contain registers @samp{r0} through @samp{r31},
43418 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43419 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43421 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43422 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43424 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43425 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43428 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43429 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43430 will combine these registers with the floating point registers
43431 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43432 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43433 through @samp{vs63}, the set of vector registers for POWER7.
43435 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43436 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43437 @samp{spefscr}. SPE targets should provide 32-bit registers in
43438 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43439 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43440 these to present registers @samp{ev0} through @samp{ev31} to the
43443 @node S/390 and System z Features
43444 @subsection S/390 and System z Features
43445 @cindex target descriptions, S/390 features
43446 @cindex target descriptions, System z features
43448 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43449 System z targets. It should contain the PSW and the 16 general
43450 registers. In particular, System z targets should provide the 64-bit
43451 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43452 S/390 targets should provide the 32-bit versions of these registers.
43453 A System z target that runs in 31-bit addressing mode should provide
43454 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43455 register's upper halves @samp{r0h} through @samp{r15h}, and their
43456 lower halves @samp{r0l} through @samp{r15l}.
43458 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43459 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43462 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43463 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43465 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43466 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43467 targets and 32-bit otherwise. In addition, the feature may contain
43468 the @samp{last_break} register, whose width depends on the addressing
43469 mode, as well as the @samp{system_call} register, which is always
43472 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43473 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43474 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43476 @node TIC6x Features
43477 @subsection TMS320C6x Features
43478 @cindex target descriptions, TIC6x features
43479 @cindex target descriptions, TMS320C6x features
43480 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43481 targets. It should contain registers @samp{A0} through @samp{A15},
43482 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43484 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43485 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43486 through @samp{B31}.
43488 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43489 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43491 @node Operating System Information
43492 @appendix Operating System Information
43493 @cindex operating system information
43499 Users of @value{GDBN} often wish to obtain information about the state of
43500 the operating system running on the target---for example the list of
43501 processes, or the list of open files. This section describes the
43502 mechanism that makes it possible. This mechanism is similar to the
43503 target features mechanism (@pxref{Target Descriptions}), but focuses
43504 on a different aspect of target.
43506 Operating system information is retrived from the target via the
43507 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43508 read}). The object name in the request should be @samp{osdata}, and
43509 the @var{annex} identifies the data to be fetched.
43512 @appendixsection Process list
43513 @cindex operating system information, process list
43515 When requesting the process list, the @var{annex} field in the
43516 @samp{qXfer} request should be @samp{processes}. The returned data is
43517 an XML document. The formal syntax of this document is defined in
43518 @file{gdb/features/osdata.dtd}.
43520 An example document is:
43523 <?xml version="1.0"?>
43524 <!DOCTYPE target SYSTEM "osdata.dtd">
43525 <osdata type="processes">
43527 <column name="pid">1</column>
43528 <column name="user">root</column>
43529 <column name="command">/sbin/init</column>
43530 <column name="cores">1,2,3</column>
43535 Each item should include a column whose name is @samp{pid}. The value
43536 of that column should identify the process on the target. The
43537 @samp{user} and @samp{command} columns are optional, and will be
43538 displayed by @value{GDBN}. The @samp{cores} column, if present,
43539 should contain a comma-separated list of cores that this process
43540 is running on. Target may provide additional columns,
43541 which @value{GDBN} currently ignores.
43543 @node Trace File Format
43544 @appendix Trace File Format
43545 @cindex trace file format
43547 The trace file comes in three parts: a header, a textual description
43548 section, and a trace frame section with binary data.
43550 The header has the form @code{\x7fTRACE0\n}. The first byte is
43551 @code{0x7f} so as to indicate that the file contains binary data,
43552 while the @code{0} is a version number that may have different values
43555 The description section consists of multiple lines of @sc{ascii} text
43556 separated by newline characters (@code{0xa}). The lines may include a
43557 variety of optional descriptive or context-setting information, such
43558 as tracepoint definitions or register set size. @value{GDBN} will
43559 ignore any line that it does not recognize. An empty line marks the end
43562 @c FIXME add some specific types of data
43564 The trace frame section consists of a number of consecutive frames.
43565 Each frame begins with a two-byte tracepoint number, followed by a
43566 four-byte size giving the amount of data in the frame. The data in
43567 the frame consists of a number of blocks, each introduced by a
43568 character indicating its type (at least register, memory, and trace
43569 state variable). The data in this section is raw binary, not a
43570 hexadecimal or other encoding; its endianness matches the target's
43573 @c FIXME bi-arch may require endianness/arch info in description section
43576 @item R @var{bytes}
43577 Register block. The number and ordering of bytes matches that of a
43578 @code{g} packet in the remote protocol. Note that these are the
43579 actual bytes, in target order and @value{GDBN} register order, not a
43580 hexadecimal encoding.
43582 @item M @var{address} @var{length} @var{bytes}...
43583 Memory block. This is a contiguous block of memory, at the 8-byte
43584 address @var{address}, with a 2-byte length @var{length}, followed by
43585 @var{length} bytes.
43587 @item V @var{number} @var{value}
43588 Trace state variable block. This records the 8-byte signed value
43589 @var{value} of trace state variable numbered @var{number}.
43593 Future enhancements of the trace file format may include additional types
43596 @node Index Section Format
43597 @appendix @code{.gdb_index} section format
43598 @cindex .gdb_index section format
43599 @cindex index section format
43601 This section documents the index section that is created by @code{save
43602 gdb-index} (@pxref{Index Files}). The index section is
43603 DWARF-specific; some knowledge of DWARF is assumed in this
43606 The mapped index file format is designed to be directly
43607 @code{mmap}able on any architecture. In most cases, a datum is
43608 represented using a little-endian 32-bit integer value, called an
43609 @code{offset_type}. Big endian machines must byte-swap the values
43610 before using them. Exceptions to this rule are noted. The data is
43611 laid out such that alignment is always respected.
43613 A mapped index consists of several areas, laid out in order.
43617 The file header. This is a sequence of values, of @code{offset_type}
43618 unless otherwise noted:
43622 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43623 Version 4 uses a different hashing function from versions 5 and 6.
43624 Version 6 includes symbols for inlined functions, whereas versions 4
43625 and 5 do not. Version 7 adds attributes to the CU indices in the
43626 symbol table. Version 8 specifies that symbols from DWARF type units
43627 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43628 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43630 @value{GDBN} will only read version 4, 5, or 6 indices
43631 by specifying @code{set use-deprecated-index-sections on}.
43632 GDB has a workaround for potentially broken version 7 indices so it is
43633 currently not flagged as deprecated.
43636 The offset, from the start of the file, of the CU list.
43639 The offset, from the start of the file, of the types CU list. Note
43640 that this area can be empty, in which case this offset will be equal
43641 to the next offset.
43644 The offset, from the start of the file, of the address area.
43647 The offset, from the start of the file, of the symbol table.
43650 The offset, from the start of the file, of the constant pool.
43654 The CU list. This is a sequence of pairs of 64-bit little-endian
43655 values, sorted by the CU offset. The first element in each pair is
43656 the offset of a CU in the @code{.debug_info} section. The second
43657 element in each pair is the length of that CU. References to a CU
43658 elsewhere in the map are done using a CU index, which is just the
43659 0-based index into this table. Note that if there are type CUs, then
43660 conceptually CUs and type CUs form a single list for the purposes of
43664 The types CU list. This is a sequence of triplets of 64-bit
43665 little-endian values. In a triplet, the first value is the CU offset,
43666 the second value is the type offset in the CU, and the third value is
43667 the type signature. The types CU list is not sorted.
43670 The address area. The address area consists of a sequence of address
43671 entries. Each address entry has three elements:
43675 The low address. This is a 64-bit little-endian value.
43678 The high address. This is a 64-bit little-endian value. Like
43679 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43682 The CU index. This is an @code{offset_type} value.
43686 The symbol table. This is an open-addressed hash table. The size of
43687 the hash table is always a power of 2.
43689 Each slot in the hash table consists of a pair of @code{offset_type}
43690 values. The first value is the offset of the symbol's name in the
43691 constant pool. The second value is the offset of the CU vector in the
43694 If both values are 0, then this slot in the hash table is empty. This
43695 is ok because while 0 is a valid constant pool index, it cannot be a
43696 valid index for both a string and a CU vector.
43698 The hash value for a table entry is computed by applying an
43699 iterative hash function to the symbol's name. Starting with an
43700 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43701 the string is incorporated into the hash using the formula depending on the
43706 The formula is @code{r = r * 67 + c - 113}.
43708 @item Versions 5 to 7
43709 The formula is @code{r = r * 67 + tolower (c) - 113}.
43712 The terminating @samp{\0} is not incorporated into the hash.
43714 The step size used in the hash table is computed via
43715 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43716 value, and @samp{size} is the size of the hash table. The step size
43717 is used to find the next candidate slot when handling a hash
43720 The names of C@t{++} symbols in the hash table are canonicalized. We
43721 don't currently have a simple description of the canonicalization
43722 algorithm; if you intend to create new index sections, you must read
43726 The constant pool. This is simply a bunch of bytes. It is organized
43727 so that alignment is correct: CU vectors are stored first, followed by
43730 A CU vector in the constant pool is a sequence of @code{offset_type}
43731 values. The first value is the number of CU indices in the vector.
43732 Each subsequent value is the index and symbol attributes of a CU in
43733 the CU list. This element in the hash table is used to indicate which
43734 CUs define the symbol and how the symbol is used.
43735 See below for the format of each CU index+attributes entry.
43737 A string in the constant pool is zero-terminated.
43740 Attributes were added to CU index values in @code{.gdb_index} version 7.
43741 If a symbol has multiple uses within a CU then there is one
43742 CU index+attributes value for each use.
43744 The format of each CU index+attributes entry is as follows
43750 This is the index of the CU in the CU list.
43752 These bits are reserved for future purposes and must be zero.
43754 The kind of the symbol in the CU.
43758 This value is reserved and should not be used.
43759 By reserving zero the full @code{offset_type} value is backwards compatible
43760 with previous versions of the index.
43762 The symbol is a type.
43764 The symbol is a variable or an enum value.
43766 The symbol is a function.
43768 Any other kind of symbol.
43770 These values are reserved.
43774 This bit is zero if the value is global and one if it is static.
43776 The determination of whether a symbol is global or static is complicated.
43777 The authorative reference is the file @file{dwarf2read.c} in
43778 @value{GDBN} sources.
43782 This pseudo-code describes the computation of a symbol's kind and
43783 global/static attributes in the index.
43786 is_external = get_attribute (die, DW_AT_external);
43787 language = get_attribute (cu_die, DW_AT_language);
43790 case DW_TAG_typedef:
43791 case DW_TAG_base_type:
43792 case DW_TAG_subrange_type:
43796 case DW_TAG_enumerator:
43798 is_static = (language != CPLUS && language != JAVA);
43800 case DW_TAG_subprogram:
43802 is_static = ! (is_external || language == ADA);
43804 case DW_TAG_constant:
43806 is_static = ! is_external;
43808 case DW_TAG_variable:
43810 is_static = ! is_external;
43812 case DW_TAG_namespace:
43816 case DW_TAG_class_type:
43817 case DW_TAG_interface_type:
43818 case DW_TAG_structure_type:
43819 case DW_TAG_union_type:
43820 case DW_TAG_enumeration_type:
43822 is_static = (language != CPLUS && language != JAVA);
43830 @appendix Manual pages
43834 * gdb man:: The GNU Debugger man page
43835 * gdbserver man:: Remote Server for the GNU Debugger man page
43836 * gcore man:: Generate a core file of a running program
43837 * gdbinit man:: gdbinit scripts
43843 @c man title gdb The GNU Debugger
43845 @c man begin SYNOPSIS gdb
43846 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43847 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43848 [@option{-b}@w{ }@var{bps}]
43849 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43850 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43851 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43852 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43853 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43856 @c man begin DESCRIPTION gdb
43857 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43858 going on ``inside'' another program while it executes -- or what another
43859 program was doing at the moment it crashed.
43861 @value{GDBN} can do four main kinds of things (plus other things in support of
43862 these) to help you catch bugs in the act:
43866 Start your program, specifying anything that might affect its behavior.
43869 Make your program stop on specified conditions.
43872 Examine what has happened, when your program has stopped.
43875 Change things in your program, so you can experiment with correcting the
43876 effects of one bug and go on to learn about another.
43879 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43882 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43883 commands from the terminal until you tell it to exit with the @value{GDBN}
43884 command @code{quit}. You can get online help from @value{GDBN} itself
43885 by using the command @code{help}.
43887 You can run @code{gdb} with no arguments or options; but the most
43888 usual way to start @value{GDBN} is with one argument or two, specifying an
43889 executable program as the argument:
43895 You can also start with both an executable program and a core file specified:
43901 You can, instead, specify a process ID as a second argument, if you want
43902 to debug a running process:
43910 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43911 named @file{1234}; @value{GDBN} does check for a core file first).
43912 With option @option{-p} you can omit the @var{program} filename.
43914 Here are some of the most frequently needed @value{GDBN} commands:
43916 @c pod2man highlights the right hand side of the @item lines.
43918 @item break [@var{file}:]@var{functiop}
43919 Set a breakpoint at @var{function} (in @var{file}).
43921 @item run [@var{arglist}]
43922 Start your program (with @var{arglist}, if specified).
43925 Backtrace: display the program stack.
43927 @item print @var{expr}
43928 Display the value of an expression.
43931 Continue running your program (after stopping, e.g. at a breakpoint).
43934 Execute next program line (after stopping); step @emph{over} any
43935 function calls in the line.
43937 @item edit [@var{file}:]@var{function}
43938 look at the program line where it is presently stopped.
43940 @item list [@var{file}:]@var{function}
43941 type the text of the program in the vicinity of where it is presently stopped.
43944 Execute next program line (after stopping); step @emph{into} any
43945 function calls in the line.
43947 @item help [@var{name}]
43948 Show information about @value{GDBN} command @var{name}, or general information
43949 about using @value{GDBN}.
43952 Exit from @value{GDBN}.
43956 For full details on @value{GDBN},
43957 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43958 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43959 as the @code{gdb} entry in the @code{info} program.
43963 @c man begin OPTIONS gdb
43964 Any arguments other than options specify an executable
43965 file and core file (or process ID); that is, the first argument
43966 encountered with no
43967 associated option flag is equivalent to a @option{-se} option, and the second,
43968 if any, is equivalent to a @option{-c} option if it's the name of a file.
43970 both long and short forms; both are shown here. The long forms are also
43971 recognized if you truncate them, so long as enough of the option is
43972 present to be unambiguous. (If you prefer, you can flag option
43973 arguments with @option{+} rather than @option{-}, though we illustrate the
43974 more usual convention.)
43976 All the options and command line arguments you give are processed
43977 in sequential order. The order makes a difference when the @option{-x}
43983 List all options, with brief explanations.
43985 @item -symbols=@var{file}
43986 @itemx -s @var{file}
43987 Read symbol table from file @var{file}.
43990 Enable writing into executable and core files.
43992 @item -exec=@var{file}
43993 @itemx -e @var{file}
43994 Use file @var{file} as the executable file to execute when
43995 appropriate, and for examining pure data in conjunction with a core
43998 @item -se=@var{file}
43999 Read symbol table from file @var{file} and use it as the executable
44002 @item -core=@var{file}
44003 @itemx -c @var{file}
44004 Use file @var{file} as a core dump to examine.
44006 @item -command=@var{file}
44007 @itemx -x @var{file}
44008 Execute @value{GDBN} commands from file @var{file}.
44010 @item -ex @var{command}
44011 Execute given @value{GDBN} @var{command}.
44013 @item -directory=@var{directory}
44014 @itemx -d @var{directory}
44015 Add @var{directory} to the path to search for source files.
44018 Do not execute commands from @file{~/.gdbinit}.
44022 Do not execute commands from any @file{.gdbinit} initialization files.
44026 ``Quiet''. Do not print the introductory and copyright messages. These
44027 messages are also suppressed in batch mode.
44030 Run in batch mode. Exit with status @code{0} after processing all the command
44031 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44032 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44033 commands in the command files.
44035 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44036 download and run a program on another computer; in order to make this
44037 more useful, the message
44040 Program exited normally.
44044 (which is ordinarily issued whenever a program running under @value{GDBN} control
44045 terminates) is not issued when running in batch mode.
44047 @item -cd=@var{directory}
44048 Run @value{GDBN} using @var{directory} as its working directory,
44049 instead of the current directory.
44053 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44054 @value{GDBN} to output the full file name and line number in a standard,
44055 recognizable fashion each time a stack frame is displayed (which
44056 includes each time the program stops). This recognizable format looks
44057 like two @samp{\032} characters, followed by the file name, line number
44058 and character position separated by colons, and a newline. The
44059 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44060 characters as a signal to display the source code for the frame.
44063 Set the line speed (baud rate or bits per second) of any serial
44064 interface used by @value{GDBN} for remote debugging.
44066 @item -tty=@var{device}
44067 Run using @var{device} for your program's standard input and output.
44071 @c man begin SEEALSO gdb
44073 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44074 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44075 documentation are properly installed at your site, the command
44082 should give you access to the complete manual.
44084 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44085 Richard M. Stallman and Roland H. Pesch, July 1991.
44089 @node gdbserver man
44090 @heading gdbserver man
44092 @c man title gdbserver Remote Server for the GNU Debugger
44094 @c man begin SYNOPSIS gdbserver
44095 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44097 gdbserver --attach @var{comm} @var{pid}
44099 gdbserver --multi @var{comm}
44103 @c man begin DESCRIPTION gdbserver
44104 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44105 than the one which is running the program being debugged.
44108 @subheading Usage (server (target) side)
44111 Usage (server (target) side):
44114 First, you need to have a copy of the program you want to debug put onto
44115 the target system. The program can be stripped to save space if needed, as
44116 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44117 the @value{GDBN} running on the host system.
44119 To use the server, you log on to the target system, and run the @command{gdbserver}
44120 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44121 your program, and (c) its arguments. The general syntax is:
44124 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44127 For example, using a serial port, you might say:
44131 @c @file would wrap it as F</dev/com1>.
44132 target> gdbserver /dev/com1 emacs foo.txt
44135 target> gdbserver @file{/dev/com1} emacs foo.txt
44139 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44140 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44141 waits patiently for the host @value{GDBN} to communicate with it.
44143 To use a TCP connection, you could say:
44146 target> gdbserver host:2345 emacs foo.txt
44149 This says pretty much the same thing as the last example, except that we are
44150 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44151 that we are expecting to see a TCP connection from @code{host} to local TCP port
44152 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44153 want for the port number as long as it does not conflict with any existing TCP
44154 ports on the target system. This same port number must be used in the host
44155 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44156 you chose a port number that conflicts with another service, @command{gdbserver} will
44157 print an error message and exit.
44159 @command{gdbserver} can also attach to running programs.
44160 This is accomplished via the @option{--attach} argument. The syntax is:
44163 target> gdbserver --attach @var{comm} @var{pid}
44166 @var{pid} is the process ID of a currently running process. It isn't
44167 necessary to point @command{gdbserver} at a binary for the running process.
44169 To start @code{gdbserver} without supplying an initial command to run
44170 or process ID to attach, use the @option{--multi} command line option.
44171 In such case you should connect using @kbd{target extended-remote} to start
44172 the program you want to debug.
44175 target> gdbserver --multi @var{comm}
44179 @subheading Usage (host side)
44185 You need an unstripped copy of the target program on your host system, since
44186 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
44187 would, with the target program as the first argument. (You may need to use the
44188 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44189 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44190 new command you need to know about is @code{target remote}
44191 (or @code{target extended-remote}). Its argument is either
44192 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44193 descriptor. For example:
44197 @c @file would wrap it as F</dev/ttyb>.
44198 (gdb) target remote /dev/ttyb
44201 (gdb) target remote @file{/dev/ttyb}
44206 communicates with the server via serial line @file{/dev/ttyb}, and:
44209 (gdb) target remote the-target:2345
44213 communicates via a TCP connection to port 2345 on host `the-target', where
44214 you previously started up @command{gdbserver} with the same port number. Note that for
44215 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44216 command, otherwise you may get an error that looks something like
44217 `Connection refused'.
44219 @command{gdbserver} can also debug multiple inferiors at once,
44222 the @value{GDBN} manual in node @code{Inferiors and Programs}
44223 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44226 @ref{Inferiors and Programs}.
44228 In such case use the @code{extended-remote} @value{GDBN} command variant:
44231 (gdb) target extended-remote the-target:2345
44234 The @command{gdbserver} option @option{--multi} may or may not be used in such
44238 @c man begin OPTIONS gdbserver
44239 There are three different modes for invoking @command{gdbserver}:
44244 Debug a specific program specified by its program name:
44247 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44250 The @var{comm} parameter specifies how should the server communicate
44251 with @value{GDBN}; it is either a device name (to use a serial line),
44252 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44253 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44254 debug in @var{prog}. Any remaining arguments will be passed to the
44255 program verbatim. When the program exits, @value{GDBN} will close the
44256 connection, and @code{gdbserver} will exit.
44259 Debug a specific program by specifying the process ID of a running
44263 gdbserver --attach @var{comm} @var{pid}
44266 The @var{comm} parameter is as described above. Supply the process ID
44267 of a running program in @var{pid}; @value{GDBN} will do everything
44268 else. Like with the previous mode, when the process @var{pid} exits,
44269 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44272 Multi-process mode -- debug more than one program/process:
44275 gdbserver --multi @var{comm}
44278 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44279 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44280 close the connection when a process being debugged exits, so you can
44281 debug several processes in the same session.
44284 In each of the modes you may specify these options:
44289 List all options, with brief explanations.
44292 This option causes @command{gdbserver} to print its version number and exit.
44295 @command{gdbserver} will attach to a running program. The syntax is:
44298 target> gdbserver --attach @var{comm} @var{pid}
44301 @var{pid} is the process ID of a currently running process. It isn't
44302 necessary to point @command{gdbserver} at a binary for the running process.
44305 To start @code{gdbserver} without supplying an initial command to run
44306 or process ID to attach, use this command line option.
44307 Then you can connect using @kbd{target extended-remote} and start
44308 the program you want to debug. The syntax is:
44311 target> gdbserver --multi @var{comm}
44315 Instruct @code{gdbserver} to display extra status information about the debugging
44317 This option is intended for @code{gdbserver} development and for bug reports to
44320 @item --remote-debug
44321 Instruct @code{gdbserver} to display remote protocol debug output.
44322 This option is intended for @code{gdbserver} development and for bug reports to
44326 Specify a wrapper to launch programs
44327 for debugging. The option should be followed by the name of the
44328 wrapper, then any command-line arguments to pass to the wrapper, then
44329 @kbd{--} indicating the end of the wrapper arguments.
44332 By default, @command{gdbserver} keeps the listening TCP port open, so that
44333 additional connections are possible. However, if you start @code{gdbserver}
44334 with the @option{--once} option, it will stop listening for any further
44335 connection attempts after connecting to the first @value{GDBN} session.
44337 @c --disable-packet is not documented for users.
44339 @c --disable-randomization and --no-disable-randomization are superseded by
44340 @c QDisableRandomization.
44345 @c man begin SEEALSO gdbserver
44347 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44348 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44349 documentation are properly installed at your site, the command
44355 should give you access to the complete manual.
44357 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44358 Richard M. Stallman and Roland H. Pesch, July 1991.
44365 @c man title gcore Generate a core file of a running program
44368 @c man begin SYNOPSIS gcore
44369 gcore [-o @var{filename}] @var{pid}
44373 @c man begin DESCRIPTION gcore
44374 Generate a core dump of a running program with process ID @var{pid}.
44375 Produced file is equivalent to a kernel produced core file as if the process
44376 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44377 limit). Unlike after a crash, after @command{gcore} the program remains
44378 running without any change.
44381 @c man begin OPTIONS gcore
44383 @item -o @var{filename}
44384 The optional argument
44385 @var{filename} specifies the file name where to put the core dump.
44386 If not specified, the file name defaults to @file{core.@var{pid}},
44387 where @var{pid} is the running program process ID.
44391 @c man begin SEEALSO gcore
44393 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44394 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44395 documentation are properly installed at your site, the command
44402 should give you access to the complete manual.
44404 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44405 Richard M. Stallman and Roland H. Pesch, July 1991.
44412 @c man title gdbinit GDB initialization scripts
44415 @c man begin SYNOPSIS gdbinit
44416 @ifset SYSTEM_GDBINIT
44417 @value{SYSTEM_GDBINIT}
44426 @c man begin DESCRIPTION gdbinit
44427 These files contain @value{GDBN} commands to automatically execute during
44428 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44431 the @value{GDBN} manual in node @code{Sequences}
44432 -- shell command @code{info -f gdb -n Sequences}.
44438 Please read more in
44440 the @value{GDBN} manual in node @code{Startup}
44441 -- shell command @code{info -f gdb -n Startup}.
44448 @ifset SYSTEM_GDBINIT
44449 @item @value{SYSTEM_GDBINIT}
44451 @ifclear SYSTEM_GDBINIT
44452 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44454 System-wide initialization file. It is executed unless user specified
44455 @value{GDBN} option @code{-nx} or @code{-n}.
44458 the @value{GDBN} manual in node @code{System-wide configuration}
44459 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44462 @ref{System-wide configuration}.
44466 User initialization file. It is executed unless user specified
44467 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44470 Initialization file for current directory. It may need to be enabled with
44471 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44474 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44475 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44478 @ref{Init File in the Current Directory}.
44483 @c man begin SEEALSO gdbinit
44485 gdb(1), @code{info -f gdb -n Startup}
44487 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44488 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44489 documentation are properly installed at your site, the command
44495 should give you access to the complete manual.
44497 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44498 Richard M. Stallman and Roland H. Pesch, July 1991.
44504 @node GNU Free Documentation License
44505 @appendix GNU Free Documentation License
44508 @node Concept Index
44509 @unnumbered Concept Index
44513 @node Command and Variable Index
44514 @unnumbered Command, Variable, and Function Index
44519 % I think something like @@colophon should be in texinfo. In the
44521 \long\def\colophon{\hbox to0pt{}\vfill
44522 \centerline{The body of this manual is set in}
44523 \centerline{\fontname\tenrm,}
44524 \centerline{with headings in {\bf\fontname\tenbf}}
44525 \centerline{and examples in {\tt\fontname\tentt}.}
44526 \centerline{{\it\fontname\tenit\/},}
44527 \centerline{{\bf\fontname\tenbf}, and}
44528 \centerline{{\sl\fontname\tensl\/}}
44529 \centerline{are used for emphasis.}\vfill}
44531 % Blame: doc@@cygnus.com, 1991.