1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2014 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
23 @c To avoid file-name clashes between index.html and Index.html, when
24 @c the manual is produced on a Posix host and then moved to a
25 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
26 @c indices into two: Concept Index and all the rest.
30 @c readline appendices use @vindex, @findex and @ftable,
31 @c annotate.texi and gdbmi use @findex.
34 @c !!set GDB manual's edition---not the same as GDB version!
35 @c This is updated by GNU Press.
38 @c !!set GDB edit command default editor
41 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
43 @c This is a dir.info fragment to support semi-automated addition of
44 @c manuals to an info tree.
45 @dircategory Software development
47 * Gdb: (gdb). The GNU debugger.
48 * gdbserver: (gdb) Server. The GNU debugging server.
52 @c man begin COPYRIGHT
53 Copyright @copyright{} 1988-2014 Free Software Foundation, Inc.
55 Permission is granted to copy, distribute and/or modify this document
56 under the terms of the GNU Free Documentation License, Version 1.3 or
57 any later version published by the Free Software Foundation; with the
58 Invariant Sections being ``Free Software'' and ``Free Software Needs
59 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
60 and with the Back-Cover Texts as in (a) below.
62 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
63 this GNU Manual. Buying copies from GNU Press supports the FSF in
64 developing GNU and promoting software freedom.''
69 This file documents the @sc{gnu} debugger @value{GDBN}.
71 This is the @value{EDITION} Edition, of @cite{Debugging with
72 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
73 @ifset VERSION_PACKAGE
74 @value{VERSION_PACKAGE}
76 Version @value{GDBVN}.
82 @title Debugging with @value{GDBN}
83 @subtitle The @sc{gnu} Source-Level Debugger
85 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
86 @ifset VERSION_PACKAGE
88 @subtitle @value{VERSION_PACKAGE}
90 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
94 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
95 \hfill {\it Debugging with @value{GDBN}}\par
96 \hfill \TeX{}info \texinfoversion\par
100 @vskip 0pt plus 1filll
101 Published by the Free Software Foundation @*
102 51 Franklin Street, Fifth Floor,
103 Boston, MA 02110-1301, USA@*
104 ISBN 978-0-9831592-3-0 @*
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2014 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
163 * In-Process Agent:: In-Process Agent
165 * GDB Bugs:: Reporting bugs in @value{GDBN}
167 @ifset SYSTEM_READLINE
168 * Command Line Editing: (rluserman). Command Line Editing
169 * Using History Interactively: (history). Using History Interactively
171 @ifclear SYSTEM_READLINE
172 * Command Line Editing:: Command Line Editing
173 * Using History Interactively:: Using History Interactively
175 * In Memoriam:: In Memoriam
176 * Formatting Documentation:: How to format and print @value{GDBN} documentation
177 * Installing GDB:: Installing GDB
178 * Maintenance Commands:: Maintenance Commands
179 * Remote Protocol:: GDB Remote Serial Protocol
180 * Agent Expressions:: The GDB Agent Expression Mechanism
181 * Target Descriptions:: How targets can describe themselves to
183 * Operating System Information:: Getting additional information from
185 * Trace File Format:: GDB trace file format
186 * Index Section Format:: .gdb_index section format
187 * Man Pages:: Manual pages
188 * Copying:: GNU General Public License says
189 how you can copy and share GDB
190 * GNU Free Documentation License:: The license for this documentation
191 * Concept Index:: Index of @value{GDBN} concepts
192 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
193 functions, and Python data types
201 @unnumbered Summary of @value{GDBN}
203 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
204 going on ``inside'' another program while it executes---or what another
205 program was doing at the moment it crashed.
207 @value{GDBN} can do four main kinds of things (plus other things in support of
208 these) to help you catch bugs in the act:
212 Start your program, specifying anything that might affect its behavior.
215 Make your program stop on specified conditions.
218 Examine what has happened, when your program has stopped.
221 Change things in your program, so you can experiment with correcting the
222 effects of one bug and go on to learn about another.
225 You can use @value{GDBN} to debug programs written in C and C@t{++}.
226 For more information, see @ref{Supported Languages,,Supported Languages}.
227 For more information, see @ref{C,,C and C++}.
229 Support for D is partial. For information on D, see
233 Support for Modula-2 is partial. For information on Modula-2, see
234 @ref{Modula-2,,Modula-2}.
236 Support for OpenCL C is partial. For information on OpenCL C, see
237 @ref{OpenCL C,,OpenCL C}.
240 Debugging Pascal programs which use sets, subranges, file variables, or
241 nested functions does not currently work. @value{GDBN} does not support
242 entering expressions, printing values, or similar features using Pascal
246 @value{GDBN} can be used to debug programs written in Fortran, although
247 it may be necessary to refer to some variables with a trailing
250 @value{GDBN} can be used to debug programs written in Objective-C,
251 using either the Apple/NeXT or the GNU Objective-C runtime.
254 * Free Software:: Freely redistributable software
255 * Free Documentation:: Free Software Needs Free Documentation
256 * Contributors:: Contributors to GDB
260 @unnumberedsec Free Software
262 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
263 General Public License
264 (GPL). The GPL gives you the freedom to copy or adapt a licensed
265 program---but every person getting a copy also gets with it the
266 freedom to modify that copy (which means that they must get access to
267 the source code), and the freedom to distribute further copies.
268 Typical software companies use copyrights to limit your freedoms; the
269 Free Software Foundation uses the GPL to preserve these freedoms.
271 Fundamentally, the General Public License is a license which says that
272 you have these freedoms and that you cannot take these freedoms away
275 @node Free Documentation
276 @unnumberedsec Free Software Needs Free Documentation
278 The biggest deficiency in the free software community today is not in
279 the software---it is the lack of good free documentation that we can
280 include with the free software. Many of our most important
281 programs do not come with free reference manuals and free introductory
282 texts. Documentation is an essential part of any software package;
283 when an important free software package does not come with a free
284 manual and a free tutorial, that is a major gap. We have many such
287 Consider Perl, for instance. The tutorial manuals that people
288 normally use are non-free. How did this come about? Because the
289 authors of those manuals published them with restrictive terms---no
290 copying, no modification, source files not available---which exclude
291 them from the free software world.
293 That wasn't the first time this sort of thing happened, and it was far
294 from the last. Many times we have heard a GNU user eagerly describe a
295 manual that he is writing, his intended contribution to the community,
296 only to learn that he had ruined everything by signing a publication
297 contract to make it non-free.
299 Free documentation, like free software, is a matter of freedom, not
300 price. The problem with the non-free manual is not that publishers
301 charge a price for printed copies---that in itself is fine. (The Free
302 Software Foundation sells printed copies of manuals, too.) The
303 problem is the restrictions on the use of the manual. Free manuals
304 are available in source code form, and give you permission to copy and
305 modify. Non-free manuals do not allow this.
307 The criteria of freedom for a free manual are roughly the same as for
308 free software. Redistribution (including the normal kinds of
309 commercial redistribution) must be permitted, so that the manual can
310 accompany every copy of the program, both on-line and on paper.
312 Permission for modification of the technical content is crucial too.
313 When people modify the software, adding or changing features, if they
314 are conscientious they will change the manual too---so they can
315 provide accurate and clear documentation for the modified program. A
316 manual that leaves you no choice but to write a new manual to document
317 a changed version of the program is not really available to our
320 Some kinds of limits on the way modification is handled are
321 acceptable. For example, requirements to preserve the original
322 author's copyright notice, the distribution terms, or the list of
323 authors, are ok. It is also no problem to require modified versions
324 to include notice that they were modified. Even entire sections that
325 may not be deleted or changed are acceptable, as long as they deal
326 with nontechnical topics (like this one). These kinds of restrictions
327 are acceptable because they don't obstruct the community's normal use
330 However, it must be possible to modify all the @emph{technical}
331 content of the manual, and then distribute the result in all the usual
332 media, through all the usual channels. Otherwise, the restrictions
333 obstruct the use of the manual, it is not free, and we need another
334 manual to replace it.
336 Please spread the word about this issue. Our community continues to
337 lose manuals to proprietary publishing. If we spread the word that
338 free software needs free reference manuals and free tutorials, perhaps
339 the next person who wants to contribute by writing documentation will
340 realize, before it is too late, that only free manuals contribute to
341 the free software community.
343 If you are writing documentation, please insist on publishing it under
344 the GNU Free Documentation License or another free documentation
345 license. Remember that this decision requires your approval---you
346 don't have to let the publisher decide. Some commercial publishers
347 will use a free license if you insist, but they will not propose the
348 option; it is up to you to raise the issue and say firmly that this is
349 what you want. If the publisher you are dealing with refuses, please
350 try other publishers. If you're not sure whether a proposed license
351 is free, write to @email{licensing@@gnu.org}.
353 You can encourage commercial publishers to sell more free, copylefted
354 manuals and tutorials by buying them, and particularly by buying
355 copies from the publishers that paid for their writing or for major
356 improvements. Meanwhile, try to avoid buying non-free documentation
357 at all. Check the distribution terms of a manual before you buy it,
358 and insist that whoever seeks your business must respect your freedom.
359 Check the history of the book, and try to reward the publishers that
360 have paid or pay the authors to work on it.
362 The Free Software Foundation maintains a list of free documentation
363 published by other publishers, at
364 @url{http://www.fsf.org/doc/other-free-books.html}.
367 @unnumberedsec Contributors to @value{GDBN}
369 Richard Stallman was the original author of @value{GDBN}, and of many
370 other @sc{gnu} programs. Many others have contributed to its
371 development. This section attempts to credit major contributors. One
372 of the virtues of free software is that everyone is free to contribute
373 to it; with regret, we cannot actually acknowledge everyone here. The
374 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
375 blow-by-blow account.
377 Changes much prior to version 2.0 are lost in the mists of time.
380 @emph{Plea:} Additions to this section are particularly welcome. If you
381 or your friends (or enemies, to be evenhanded) have been unfairly
382 omitted from this list, we would like to add your names!
385 So that they may not regard their many labors as thankless, we
386 particularly thank those who shepherded @value{GDBN} through major
388 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
389 Jim Blandy (release 4.18);
390 Jason Molenda (release 4.17);
391 Stan Shebs (release 4.14);
392 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
393 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
394 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
395 Jim Kingdon (releases 3.5, 3.4, and 3.3);
396 and Randy Smith (releases 3.2, 3.1, and 3.0).
398 Richard Stallman, assisted at various times by Peter TerMaat, Chris
399 Hanson, and Richard Mlynarik, handled releases through 2.8.
401 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
402 in @value{GDBN}, with significant additional contributions from Per
403 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
404 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
405 much general update work leading to release 3.0).
407 @value{GDBN} uses the BFD subroutine library to examine multiple
408 object-file formats; BFD was a joint project of David V.
409 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
411 David Johnson wrote the original COFF support; Pace Willison did
412 the original support for encapsulated COFF.
414 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
416 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
417 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
419 Jean-Daniel Fekete contributed Sun 386i support.
420 Chris Hanson improved the HP9000 support.
421 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
422 David Johnson contributed Encore Umax support.
423 Jyrki Kuoppala contributed Altos 3068 support.
424 Jeff Law contributed HP PA and SOM support.
425 Keith Packard contributed NS32K support.
426 Doug Rabson contributed Acorn Risc Machine support.
427 Bob Rusk contributed Harris Nighthawk CX-UX support.
428 Chris Smith contributed Convex support (and Fortran debugging).
429 Jonathan Stone contributed Pyramid support.
430 Michael Tiemann contributed SPARC support.
431 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
432 Pace Willison contributed Intel 386 support.
433 Jay Vosburgh contributed Symmetry support.
434 Marko Mlinar contributed OpenRISC 1000 support.
436 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
438 Rich Schaefer and Peter Schauer helped with support of SunOS shared
441 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
442 about several machine instruction sets.
444 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
445 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
446 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
447 and RDI targets, respectively.
449 Brian Fox is the author of the readline libraries providing
450 command-line editing and command history.
452 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
453 Modula-2 support, and contributed the Languages chapter of this manual.
455 Fred Fish wrote most of the support for Unix System Vr4.
456 He also enhanced the command-completion support to cover C@t{++} overloaded
459 Hitachi America (now Renesas America), Ltd. sponsored the support for
460 H8/300, H8/500, and Super-H processors.
462 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
464 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
467 Toshiba sponsored the support for the TX39 Mips processor.
469 Matsushita sponsored the support for the MN10200 and MN10300 processors.
471 Fujitsu sponsored the support for SPARClite and FR30 processors.
473 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
476 Michael Snyder added support for tracepoints.
478 Stu Grossman wrote gdbserver.
480 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
481 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
483 The following people at the Hewlett-Packard Company contributed
484 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
485 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
486 compiler, and the Text User Interface (nee Terminal User Interface):
487 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
488 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
489 provided HP-specific information in this manual.
491 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
492 Robert Hoehne made significant contributions to the DJGPP port.
494 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
495 development since 1991. Cygnus engineers who have worked on @value{GDBN}
496 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
497 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
498 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
499 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
500 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
501 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
502 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
503 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
504 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
505 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
506 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
507 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
508 Zuhn have made contributions both large and small.
510 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
511 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
513 Jim Blandy added support for preprocessor macros, while working for Red
516 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
517 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
518 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
519 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
520 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
521 with the migration of old architectures to this new framework.
523 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
524 unwinder framework, this consisting of a fresh new design featuring
525 frame IDs, independent frame sniffers, and the sentinel frame. Mark
526 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
527 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
528 trad unwinders. The architecture-specific changes, each involving a
529 complete rewrite of the architecture's frame code, were carried out by
530 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
531 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
532 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
533 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
536 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
537 Tensilica, Inc.@: contributed support for Xtensa processors. Others
538 who have worked on the Xtensa port of @value{GDBN} in the past include
539 Steve Tjiang, John Newlin, and Scott Foehner.
541 Michael Eager and staff of Xilinx, Inc., contributed support for the
542 Xilinx MicroBlaze architecture.
545 @chapter A Sample @value{GDBN} Session
547 You can use this manual at your leisure to read all about @value{GDBN}.
548 However, a handful of commands are enough to get started using the
549 debugger. This chapter illustrates those commands.
552 In this sample session, we emphasize user input like this: @b{input},
553 to make it easier to pick out from the surrounding output.
556 @c FIXME: this example may not be appropriate for some configs, where
557 @c FIXME...primary interest is in remote use.
559 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
560 processor) exhibits the following bug: sometimes, when we change its
561 quote strings from the default, the commands used to capture one macro
562 definition within another stop working. In the following short @code{m4}
563 session, we define a macro @code{foo} which expands to @code{0000}; we
564 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
565 same thing. However, when we change the open quote string to
566 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
567 procedure fails to define a new synonym @code{baz}:
576 @b{define(bar,defn(`foo'))}
580 @b{changequote(<QUOTE>,<UNQUOTE>)}
582 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
585 m4: End of input: 0: fatal error: EOF in string
589 Let us use @value{GDBN} to try to see what is going on.
592 $ @b{@value{GDBP} m4}
593 @c FIXME: this falsifies the exact text played out, to permit smallbook
594 @c FIXME... format to come out better.
595 @value{GDBN} is free software and you are welcome to distribute copies
596 of it under certain conditions; type "show copying" to see
598 There is absolutely no warranty for @value{GDBN}; type "show warranty"
601 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
606 @value{GDBN} reads only enough symbol data to know where to find the
607 rest when needed; as a result, the first prompt comes up very quickly.
608 We now tell @value{GDBN} to use a narrower display width than usual, so
609 that examples fit in this manual.
612 (@value{GDBP}) @b{set width 70}
616 We need to see how the @code{m4} built-in @code{changequote} works.
617 Having looked at the source, we know the relevant subroutine is
618 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
619 @code{break} command.
622 (@value{GDBP}) @b{break m4_changequote}
623 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
627 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
628 control; as long as control does not reach the @code{m4_changequote}
629 subroutine, the program runs as usual:
632 (@value{GDBP}) @b{run}
633 Starting program: /work/Editorial/gdb/gnu/m4/m4
641 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
642 suspends execution of @code{m4}, displaying information about the
643 context where it stops.
646 @b{changequote(<QUOTE>,<UNQUOTE>)}
648 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
650 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
654 Now we use the command @code{n} (@code{next}) to advance execution to
655 the next line of the current function.
659 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
664 @code{set_quotes} looks like a promising subroutine. We can go into it
665 by using the command @code{s} (@code{step}) instead of @code{next}.
666 @code{step} goes to the next line to be executed in @emph{any}
667 subroutine, so it steps into @code{set_quotes}.
671 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
673 530 if (lquote != def_lquote)
677 The display that shows the subroutine where @code{m4} is now
678 suspended (and its arguments) is called a stack frame display. It
679 shows a summary of the stack. We can use the @code{backtrace}
680 command (which can also be spelled @code{bt}), to see where we are
681 in the stack as a whole: the @code{backtrace} command displays a
682 stack frame for each active subroutine.
685 (@value{GDBP}) @b{bt}
686 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
688 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
690 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
691 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
693 #4 0x79dc in expand_input () at macro.c:40
694 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
698 We step through a few more lines to see what happens. The first two
699 times, we can use @samp{s}; the next two times we use @code{n} to avoid
700 falling into the @code{xstrdup} subroutine.
704 0x3b5c 532 if (rquote != def_rquote)
706 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
707 def_lquote : xstrdup(lq);
709 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
712 538 len_lquote = strlen(rquote);
716 The last line displayed looks a little odd; we can examine the variables
717 @code{lquote} and @code{rquote} to see if they are in fact the new left
718 and right quotes we specified. We use the command @code{p}
719 (@code{print}) to see their values.
722 (@value{GDBP}) @b{p lquote}
723 $1 = 0x35d40 "<QUOTE>"
724 (@value{GDBP}) @b{p rquote}
725 $2 = 0x35d50 "<UNQUOTE>"
729 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
730 To look at some context, we can display ten lines of source
731 surrounding the current line with the @code{l} (@code{list}) command.
737 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
739 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
742 538 len_lquote = strlen(rquote);
743 539 len_rquote = strlen(lquote);
750 Let us step past the two lines that set @code{len_lquote} and
751 @code{len_rquote}, and then examine the values of those variables.
755 539 len_rquote = strlen(lquote);
758 (@value{GDBP}) @b{p len_lquote}
760 (@value{GDBP}) @b{p len_rquote}
765 That certainly looks wrong, assuming @code{len_lquote} and
766 @code{len_rquote} are meant to be the lengths of @code{lquote} and
767 @code{rquote} respectively. We can set them to better values using
768 the @code{p} command, since it can print the value of
769 any expression---and that expression can include subroutine calls and
773 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
775 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
780 Is that enough to fix the problem of using the new quotes with the
781 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
782 executing with the @code{c} (@code{continue}) command, and then try the
783 example that caused trouble initially:
789 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
796 Success! The new quotes now work just as well as the default ones. The
797 problem seems to have been just the two typos defining the wrong
798 lengths. We allow @code{m4} exit by giving it an EOF as input:
802 Program exited normally.
806 The message @samp{Program exited normally.} is from @value{GDBN}; it
807 indicates @code{m4} has finished executing. We can end our @value{GDBN}
808 session with the @value{GDBN} @code{quit} command.
811 (@value{GDBP}) @b{quit}
815 @chapter Getting In and Out of @value{GDBN}
817 This chapter discusses how to start @value{GDBN}, and how to get out of it.
821 type @samp{@value{GDBP}} to start @value{GDBN}.
823 type @kbd{quit} or @kbd{Ctrl-d} to exit.
827 * Invoking GDB:: How to start @value{GDBN}
828 * Quitting GDB:: How to quit @value{GDBN}
829 * Shell Commands:: How to use shell commands inside @value{GDBN}
830 * Logging Output:: How to log @value{GDBN}'s output to a file
834 @section Invoking @value{GDBN}
836 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
837 @value{GDBN} reads commands from the terminal until you tell it to exit.
839 You can also run @code{@value{GDBP}} with a variety of arguments and options,
840 to specify more of your debugging environment at the outset.
842 The command-line options described here are designed
843 to cover a variety of situations; in some environments, some of these
844 options may effectively be unavailable.
846 The most usual way to start @value{GDBN} is with one argument,
847 specifying an executable program:
850 @value{GDBP} @var{program}
854 You can also start with both an executable program and a core file
858 @value{GDBP} @var{program} @var{core}
861 You can, instead, specify a process ID as a second argument, if you want
862 to debug a running process:
865 @value{GDBP} @var{program} 1234
869 would attach @value{GDBN} to process @code{1234} (unless you also have a file
870 named @file{1234}; @value{GDBN} does check for a core file first).
872 Taking advantage of the second command-line argument requires a fairly
873 complete operating system; when you use @value{GDBN} as a remote
874 debugger attached to a bare board, there may not be any notion of
875 ``process'', and there is often no way to get a core dump. @value{GDBN}
876 will warn you if it is unable to attach or to read core dumps.
878 You can optionally have @code{@value{GDBP}} pass any arguments after the
879 executable file to the inferior using @code{--args}. This option stops
882 @value{GDBP} --args gcc -O2 -c foo.c
884 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
885 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
887 You can run @code{@value{GDBP}} without printing the front material, which describes
888 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
895 You can further control how @value{GDBN} starts up by using command-line
896 options. @value{GDBN} itself can remind you of the options available.
906 to display all available options and briefly describe their use
907 (@samp{@value{GDBP} -h} is a shorter equivalent).
909 All options and command line arguments you give are processed
910 in sequential order. The order makes a difference when the
911 @samp{-x} option is used.
915 * File Options:: Choosing files
916 * Mode Options:: Choosing modes
917 * Startup:: What @value{GDBN} does during startup
921 @subsection Choosing Files
923 When @value{GDBN} starts, it reads any arguments other than options as
924 specifying an executable file and core file (or process ID). This is
925 the same as if the arguments were specified by the @samp{-se} and
926 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
927 first argument that does not have an associated option flag as
928 equivalent to the @samp{-se} option followed by that argument; and the
929 second argument that does not have an associated option flag, if any, as
930 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
931 If the second argument begins with a decimal digit, @value{GDBN} will
932 first attempt to attach to it as a process, and if that fails, attempt
933 to open it as a corefile. If you have a corefile whose name begins with
934 a digit, you can prevent @value{GDBN} from treating it as a pid by
935 prefixing it with @file{./}, e.g.@: @file{./12345}.
937 If @value{GDBN} has not been configured to included core file support,
938 such as for most embedded targets, then it will complain about a second
939 argument and ignore it.
941 Many options have both long and short forms; both are shown in the
942 following list. @value{GDBN} also recognizes the long forms if you truncate
943 them, so long as enough of the option is present to be unambiguous.
944 (If you prefer, you can flag option arguments with @samp{--} rather
945 than @samp{-}, though we illustrate the more usual convention.)
947 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
948 @c way, both those who look for -foo and --foo in the index, will find
952 @item -symbols @var{file}
954 @cindex @code{--symbols}
956 Read symbol table from file @var{file}.
958 @item -exec @var{file}
960 @cindex @code{--exec}
962 Use file @var{file} as the executable file to execute when appropriate,
963 and for examining pure data in conjunction with a core dump.
967 Read symbol table from file @var{file} and use it as the executable
970 @item -core @var{file}
972 @cindex @code{--core}
974 Use file @var{file} as a core dump to examine.
976 @item -pid @var{number}
977 @itemx -p @var{number}
980 Connect to process ID @var{number}, as with the @code{attach} command.
982 @item -command @var{file}
984 @cindex @code{--command}
986 Execute commands from file @var{file}. The contents of this file is
987 evaluated exactly as the @code{source} command would.
988 @xref{Command Files,, Command files}.
990 @item -eval-command @var{command}
991 @itemx -ex @var{command}
992 @cindex @code{--eval-command}
994 Execute a single @value{GDBN} command.
996 This option may be used multiple times to call multiple commands. It may
997 also be interleaved with @samp{-command} as required.
1000 @value{GDBP} -ex 'target sim' -ex 'load' \
1001 -x setbreakpoints -ex 'run' a.out
1004 @item -init-command @var{file}
1005 @itemx -ix @var{file}
1006 @cindex @code{--init-command}
1008 Execute commands from file @var{file} before loading the inferior (but
1009 after loading gdbinit files).
1012 @item -init-eval-command @var{command}
1013 @itemx -iex @var{command}
1014 @cindex @code{--init-eval-command}
1016 Execute a single @value{GDBN} command before loading the inferior (but
1017 after loading gdbinit files).
1020 @item -directory @var{directory}
1021 @itemx -d @var{directory}
1022 @cindex @code{--directory}
1024 Add @var{directory} to the path to search for source and script files.
1028 @cindex @code{--readnow}
1030 Read each symbol file's entire symbol table immediately, rather than
1031 the default, which is to read it incrementally as it is needed.
1032 This makes startup slower, but makes future operations faster.
1037 @subsection Choosing Modes
1039 You can run @value{GDBN} in various alternative modes---for example, in
1040 batch mode or quiet mode.
1048 Do not execute commands found in any initialization file.
1049 There are three init files, loaded in the following order:
1052 @item @file{system.gdbinit}
1053 This is the system-wide init file.
1054 Its location is specified with the @code{--with-system-gdbinit}
1055 configure option (@pxref{System-wide configuration}).
1056 It is loaded first when @value{GDBN} starts, before command line options
1057 have been processed.
1058 @item @file{~/.gdbinit}
1059 This is the init file in your home directory.
1060 It is loaded next, after @file{system.gdbinit}, and before
1061 command options have been processed.
1062 @item @file{./.gdbinit}
1063 This is the init file in the current directory.
1064 It is loaded last, after command line options other than @code{-x} and
1065 @code{-ex} have been processed. Command line options @code{-x} and
1066 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1069 For further documentation on startup processing, @xref{Startup}.
1070 For documentation on how to write command files,
1071 @xref{Command Files,,Command Files}.
1076 Do not execute commands found in @file{~/.gdbinit}, the init file
1077 in your home directory.
1083 @cindex @code{--quiet}
1084 @cindex @code{--silent}
1086 ``Quiet''. Do not print the introductory and copyright messages. These
1087 messages are also suppressed in batch mode.
1090 @cindex @code{--batch}
1091 Run in batch mode. Exit with status @code{0} after processing all the
1092 command files specified with @samp{-x} (and all commands from
1093 initialization files, if not inhibited with @samp{-n}). Exit with
1094 nonzero status if an error occurs in executing the @value{GDBN} commands
1095 in the command files. Batch mode also disables pagination, sets unlimited
1096 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1097 off} were in effect (@pxref{Messages/Warnings}).
1099 Batch mode may be useful for running @value{GDBN} as a filter, for
1100 example to download and run a program on another computer; in order to
1101 make this more useful, the message
1104 Program exited normally.
1108 (which is ordinarily issued whenever a program running under
1109 @value{GDBN} control terminates) is not issued when running in batch
1113 @cindex @code{--batch-silent}
1114 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1115 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1116 unaffected). This is much quieter than @samp{-silent} and would be useless
1117 for an interactive session.
1119 This is particularly useful when using targets that give @samp{Loading section}
1120 messages, for example.
1122 Note that targets that give their output via @value{GDBN}, as opposed to
1123 writing directly to @code{stdout}, will also be made silent.
1125 @item -return-child-result
1126 @cindex @code{--return-child-result}
1127 The return code from @value{GDBN} will be the return code from the child
1128 process (the process being debugged), with the following exceptions:
1132 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1133 internal error. In this case the exit code is the same as it would have been
1134 without @samp{-return-child-result}.
1136 The user quits with an explicit value. E.g., @samp{quit 1}.
1138 The child process never runs, or is not allowed to terminate, in which case
1139 the exit code will be -1.
1142 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1143 when @value{GDBN} is being used as a remote program loader or simulator
1148 @cindex @code{--nowindows}
1150 ``No windows''. If @value{GDBN} comes with a graphical user interface
1151 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1152 interface. If no GUI is available, this option has no effect.
1156 @cindex @code{--windows}
1158 If @value{GDBN} includes a GUI, then this option requires it to be
1161 @item -cd @var{directory}
1163 Run @value{GDBN} using @var{directory} as its working directory,
1164 instead of the current directory.
1166 @item -data-directory @var{directory}
1167 @cindex @code{--data-directory}
1168 Run @value{GDBN} using @var{directory} as its data directory.
1169 The data directory is where @value{GDBN} searches for its
1170 auxiliary files. @xref{Data Files}.
1174 @cindex @code{--fullname}
1176 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1177 subprocess. It tells @value{GDBN} to output the full file name and line
1178 number in a standard, recognizable fashion each time a stack frame is
1179 displayed (which includes each time your program stops). This
1180 recognizable format looks like two @samp{\032} characters, followed by
1181 the file name, line number and character position separated by colons,
1182 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1183 @samp{\032} characters as a signal to display the source code for the
1186 @item -annotate @var{level}
1187 @cindex @code{--annotate}
1188 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1189 effect is identical to using @samp{set annotate @var{level}}
1190 (@pxref{Annotations}). The annotation @var{level} controls how much
1191 information @value{GDBN} prints together with its prompt, values of
1192 expressions, source lines, and other types of output. Level 0 is the
1193 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1194 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1195 that control @value{GDBN}, and level 2 has been deprecated.
1197 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1201 @cindex @code{--args}
1202 Change interpretation of command line so that arguments following the
1203 executable file are passed as command line arguments to the inferior.
1204 This option stops option processing.
1206 @item -baud @var{bps}
1208 @cindex @code{--baud}
1210 Set the line speed (baud rate or bits per second) of any serial
1211 interface used by @value{GDBN} for remote debugging.
1213 @item -l @var{timeout}
1215 Set the timeout (in seconds) of any communication used by @value{GDBN}
1216 for remote debugging.
1218 @item -tty @var{device}
1219 @itemx -t @var{device}
1220 @cindex @code{--tty}
1222 Run using @var{device} for your program's standard input and output.
1223 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1225 @c resolve the situation of these eventually
1227 @cindex @code{--tui}
1228 Activate the @dfn{Text User Interface} when starting. The Text User
1229 Interface manages several text windows on the terminal, showing
1230 source, assembly, registers and @value{GDBN} command outputs
1231 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1232 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1233 Using @value{GDBN} under @sc{gnu} Emacs}).
1236 @c @cindex @code{--xdb}
1237 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1238 @c For information, see the file @file{xdb_trans.html}, which is usually
1239 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1242 @item -interpreter @var{interp}
1243 @cindex @code{--interpreter}
1244 Use the interpreter @var{interp} for interface with the controlling
1245 program or device. This option is meant to be set by programs which
1246 communicate with @value{GDBN} using it as a back end.
1247 @xref{Interpreters, , Command Interpreters}.
1249 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1250 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1251 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1252 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1253 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1254 @sc{gdb/mi} interfaces are no longer supported.
1257 @cindex @code{--write}
1258 Open the executable and core files for both reading and writing. This
1259 is equivalent to the @samp{set write on} command inside @value{GDBN}
1263 @cindex @code{--statistics}
1264 This option causes @value{GDBN} to print statistics about time and
1265 memory usage after it completes each command and returns to the prompt.
1268 @cindex @code{--version}
1269 This option causes @value{GDBN} to print its version number and
1270 no-warranty blurb, and exit.
1272 @item -configuration
1273 @cindex @code{--configuration}
1274 This option causes @value{GDBN} to print details about its build-time
1275 configuration parameters, and then exit. These details can be
1276 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1281 @subsection What @value{GDBN} Does During Startup
1282 @cindex @value{GDBN} startup
1284 Here's the description of what @value{GDBN} does during session startup:
1288 Sets up the command interpreter as specified by the command line
1289 (@pxref{Mode Options, interpreter}).
1293 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1294 used when building @value{GDBN}; @pxref{System-wide configuration,
1295 ,System-wide configuration and settings}) and executes all the commands in
1298 @anchor{Home Directory Init File}
1300 Reads the init file (if any) in your home directory@footnote{On
1301 DOS/Windows systems, the home directory is the one pointed to by the
1302 @code{HOME} environment variable.} and executes all the commands in
1305 @anchor{Option -init-eval-command}
1307 Executes commands and command files specified by the @samp{-iex} and
1308 @samp{-ix} options in their specified order. Usually you should use the
1309 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1310 settings before @value{GDBN} init files get executed and before inferior
1314 Processes command line options and operands.
1316 @anchor{Init File in the Current Directory during Startup}
1318 Reads and executes the commands from init file (if any) in the current
1319 working directory as long as @samp{set auto-load local-gdbinit} is set to
1320 @samp{on} (@pxref{Init File in the Current Directory}).
1321 This is only done if the current directory is
1322 different from your home directory. Thus, you can have more than one
1323 init file, one generic in your home directory, and another, specific
1324 to the program you are debugging, in the directory where you invoke
1328 If the command line specified a program to debug, or a process to
1329 attach to, or a core file, @value{GDBN} loads any auto-loaded
1330 scripts provided for the program or for its loaded shared libraries.
1331 @xref{Auto-loading}.
1333 If you wish to disable the auto-loading during startup,
1334 you must do something like the following:
1337 $ gdb -iex "set auto-load python-scripts off" myprogram
1340 Option @samp{-ex} does not work because the auto-loading is then turned
1344 Executes commands and command files specified by the @samp{-ex} and
1345 @samp{-x} options in their specified order. @xref{Command Files}, for
1346 more details about @value{GDBN} command files.
1349 Reads the command history recorded in the @dfn{history file}.
1350 @xref{Command History}, for more details about the command history and the
1351 files where @value{GDBN} records it.
1354 Init files use the same syntax as @dfn{command files} (@pxref{Command
1355 Files}) and are processed by @value{GDBN} in the same way. The init
1356 file in your home directory can set options (such as @samp{set
1357 complaints}) that affect subsequent processing of command line options
1358 and operands. Init files are not executed if you use the @samp{-nx}
1359 option (@pxref{Mode Options, ,Choosing Modes}).
1361 To display the list of init files loaded by gdb at startup, you
1362 can use @kbd{gdb --help}.
1364 @cindex init file name
1365 @cindex @file{.gdbinit}
1366 @cindex @file{gdb.ini}
1367 The @value{GDBN} init files are normally called @file{.gdbinit}.
1368 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1369 the limitations of file names imposed by DOS filesystems. The Windows
1370 port of @value{GDBN} uses the standard name, but if it finds a
1371 @file{gdb.ini} file in your home directory, it warns you about that
1372 and suggests to rename the file to the standard name.
1376 @section Quitting @value{GDBN}
1377 @cindex exiting @value{GDBN}
1378 @cindex leaving @value{GDBN}
1381 @kindex quit @r{[}@var{expression}@r{]}
1382 @kindex q @r{(@code{quit})}
1383 @item quit @r{[}@var{expression}@r{]}
1385 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1386 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1387 do not supply @var{expression}, @value{GDBN} will terminate normally;
1388 otherwise it will terminate using the result of @var{expression} as the
1393 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1394 terminates the action of any @value{GDBN} command that is in progress and
1395 returns to @value{GDBN} command level. It is safe to type the interrupt
1396 character at any time because @value{GDBN} does not allow it to take effect
1397 until a time when it is safe.
1399 If you have been using @value{GDBN} to control an attached process or
1400 device, you can release it with the @code{detach} command
1401 (@pxref{Attach, ,Debugging an Already-running Process}).
1403 @node Shell Commands
1404 @section Shell Commands
1406 If you need to execute occasional shell commands during your
1407 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1408 just use the @code{shell} command.
1413 @cindex shell escape
1414 @item shell @var{command-string}
1415 @itemx !@var{command-string}
1416 Invoke a standard shell to execute @var{command-string}.
1417 Note that no space is needed between @code{!} and @var{command-string}.
1418 If it exists, the environment variable @code{SHELL} determines which
1419 shell to run. Otherwise @value{GDBN} uses the default shell
1420 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1423 The utility @code{make} is often needed in development environments.
1424 You do not have to use the @code{shell} command for this purpose in
1429 @cindex calling make
1430 @item make @var{make-args}
1431 Execute the @code{make} program with the specified
1432 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1435 @node Logging Output
1436 @section Logging Output
1437 @cindex logging @value{GDBN} output
1438 @cindex save @value{GDBN} output to a file
1440 You may want to save the output of @value{GDBN} commands to a file.
1441 There are several commands to control @value{GDBN}'s logging.
1445 @item set logging on
1447 @item set logging off
1449 @cindex logging file name
1450 @item set logging file @var{file}
1451 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1452 @item set logging overwrite [on|off]
1453 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1454 you want @code{set logging on} to overwrite the logfile instead.
1455 @item set logging redirect [on|off]
1456 By default, @value{GDBN} output will go to both the terminal and the logfile.
1457 Set @code{redirect} if you want output to go only to the log file.
1458 @kindex show logging
1460 Show the current values of the logging settings.
1464 @chapter @value{GDBN} Commands
1466 You can abbreviate a @value{GDBN} command to the first few letters of the command
1467 name, if that abbreviation is unambiguous; and you can repeat certain
1468 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1469 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1470 show you the alternatives available, if there is more than one possibility).
1473 * Command Syntax:: How to give commands to @value{GDBN}
1474 * Completion:: Command completion
1475 * Help:: How to ask @value{GDBN} for help
1478 @node Command Syntax
1479 @section Command Syntax
1481 A @value{GDBN} command is a single line of input. There is no limit on
1482 how long it can be. It starts with a command name, which is followed by
1483 arguments whose meaning depends on the command name. For example, the
1484 command @code{step} accepts an argument which is the number of times to
1485 step, as in @samp{step 5}. You can also use the @code{step} command
1486 with no arguments. Some commands do not allow any arguments.
1488 @cindex abbreviation
1489 @value{GDBN} command names may always be truncated if that abbreviation is
1490 unambiguous. Other possible command abbreviations are listed in the
1491 documentation for individual commands. In some cases, even ambiguous
1492 abbreviations are allowed; for example, @code{s} is specially defined as
1493 equivalent to @code{step} even though there are other commands whose
1494 names start with @code{s}. You can test abbreviations by using them as
1495 arguments to the @code{help} command.
1497 @cindex repeating commands
1498 @kindex RET @r{(repeat last command)}
1499 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1500 repeat the previous command. Certain commands (for example, @code{run})
1501 will not repeat this way; these are commands whose unintentional
1502 repetition might cause trouble and which you are unlikely to want to
1503 repeat. User-defined commands can disable this feature; see
1504 @ref{Define, dont-repeat}.
1506 The @code{list} and @code{x} commands, when you repeat them with
1507 @key{RET}, construct new arguments rather than repeating
1508 exactly as typed. This permits easy scanning of source or memory.
1510 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1511 output, in a way similar to the common utility @code{more}
1512 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1513 @key{RET} too many in this situation, @value{GDBN} disables command
1514 repetition after any command that generates this sort of display.
1516 @kindex # @r{(a comment)}
1518 Any text from a @kbd{#} to the end of the line is a comment; it does
1519 nothing. This is useful mainly in command files (@pxref{Command
1520 Files,,Command Files}).
1522 @cindex repeating command sequences
1523 @kindex Ctrl-o @r{(operate-and-get-next)}
1524 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1525 commands. This command accepts the current line, like @key{RET}, and
1526 then fetches the next line relative to the current line from the history
1530 @section Command Completion
1533 @cindex word completion
1534 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1535 only one possibility; it can also show you what the valid possibilities
1536 are for the next word in a command, at any time. This works for @value{GDBN}
1537 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1539 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1540 of a word. If there is only one possibility, @value{GDBN} fills in the
1541 word, and waits for you to finish the command (or press @key{RET} to
1542 enter it). For example, if you type
1544 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1545 @c complete accuracy in these examples; space introduced for clarity.
1546 @c If texinfo enhancements make it unnecessary, it would be nice to
1547 @c replace " @key" by "@key" in the following...
1549 (@value{GDBP}) info bre @key{TAB}
1553 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1554 the only @code{info} subcommand beginning with @samp{bre}:
1557 (@value{GDBP}) info breakpoints
1561 You can either press @key{RET} at this point, to run the @code{info
1562 breakpoints} command, or backspace and enter something else, if
1563 @samp{breakpoints} does not look like the command you expected. (If you
1564 were sure you wanted @code{info breakpoints} in the first place, you
1565 might as well just type @key{RET} immediately after @samp{info bre},
1566 to exploit command abbreviations rather than command completion).
1568 If there is more than one possibility for the next word when you press
1569 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1570 characters and try again, or just press @key{TAB} a second time;
1571 @value{GDBN} displays all the possible completions for that word. For
1572 example, you might want to set a breakpoint on a subroutine whose name
1573 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1574 just sounds the bell. Typing @key{TAB} again displays all the
1575 function names in your program that begin with those characters, for
1579 (@value{GDBP}) b make_ @key{TAB}
1580 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1581 make_a_section_from_file make_environ
1582 make_abs_section make_function_type
1583 make_blockvector make_pointer_type
1584 make_cleanup make_reference_type
1585 make_command make_symbol_completion_list
1586 (@value{GDBP}) b make_
1590 After displaying the available possibilities, @value{GDBN} copies your
1591 partial input (@samp{b make_} in the example) so you can finish the
1594 If you just want to see the list of alternatives in the first place, you
1595 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1596 means @kbd{@key{META} ?}. You can type this either by holding down a
1597 key designated as the @key{META} shift on your keyboard (if there is
1598 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1600 @cindex quotes in commands
1601 @cindex completion of quoted strings
1602 Sometimes the string you need, while logically a ``word'', may contain
1603 parentheses or other characters that @value{GDBN} normally excludes from
1604 its notion of a word. To permit word completion to work in this
1605 situation, you may enclose words in @code{'} (single quote marks) in
1606 @value{GDBN} commands.
1608 The most likely situation where you might need this is in typing the
1609 name of a C@t{++} function. This is because C@t{++} allows function
1610 overloading (multiple definitions of the same function, distinguished
1611 by argument type). For example, when you want to set a breakpoint you
1612 may need to distinguish whether you mean the version of @code{name}
1613 that takes an @code{int} parameter, @code{name(int)}, or the version
1614 that takes a @code{float} parameter, @code{name(float)}. To use the
1615 word-completion facilities in this situation, type a single quote
1616 @code{'} at the beginning of the function name. This alerts
1617 @value{GDBN} that it may need to consider more information than usual
1618 when you press @key{TAB} or @kbd{M-?} to request word completion:
1621 (@value{GDBP}) b 'bubble( @kbd{M-?}
1622 bubble(double,double) bubble(int,int)
1623 (@value{GDBP}) b 'bubble(
1626 In some cases, @value{GDBN} can tell that completing a name requires using
1627 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1628 completing as much as it can) if you do not type the quote in the first
1632 (@value{GDBP}) b bub @key{TAB}
1633 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1634 (@value{GDBP}) b 'bubble(
1638 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1639 you have not yet started typing the argument list when you ask for
1640 completion on an overloaded symbol.
1642 For more information about overloaded functions, see @ref{C Plus Plus
1643 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1644 overload-resolution off} to disable overload resolution;
1645 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1647 @cindex completion of structure field names
1648 @cindex structure field name completion
1649 @cindex completion of union field names
1650 @cindex union field name completion
1651 When completing in an expression which looks up a field in a
1652 structure, @value{GDBN} also tries@footnote{The completer can be
1653 confused by certain kinds of invalid expressions. Also, it only
1654 examines the static type of the expression, not the dynamic type.} to
1655 limit completions to the field names available in the type of the
1659 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1660 magic to_fputs to_rewind
1661 to_data to_isatty to_write
1662 to_delete to_put to_write_async_safe
1667 This is because the @code{gdb_stdout} is a variable of the type
1668 @code{struct ui_file} that is defined in @value{GDBN} sources as
1675 ui_file_flush_ftype *to_flush;
1676 ui_file_write_ftype *to_write;
1677 ui_file_write_async_safe_ftype *to_write_async_safe;
1678 ui_file_fputs_ftype *to_fputs;
1679 ui_file_read_ftype *to_read;
1680 ui_file_delete_ftype *to_delete;
1681 ui_file_isatty_ftype *to_isatty;
1682 ui_file_rewind_ftype *to_rewind;
1683 ui_file_put_ftype *to_put;
1690 @section Getting Help
1691 @cindex online documentation
1694 You can always ask @value{GDBN} itself for information on its commands,
1695 using the command @code{help}.
1698 @kindex h @r{(@code{help})}
1701 You can use @code{help} (abbreviated @code{h}) with no arguments to
1702 display a short list of named classes of commands:
1706 List of classes of commands:
1708 aliases -- Aliases of other commands
1709 breakpoints -- Making program stop at certain points
1710 data -- Examining data
1711 files -- Specifying and examining files
1712 internals -- Maintenance commands
1713 obscure -- Obscure features
1714 running -- Running the program
1715 stack -- Examining the stack
1716 status -- Status inquiries
1717 support -- Support facilities
1718 tracepoints -- Tracing of program execution without
1719 stopping the program
1720 user-defined -- User-defined commands
1722 Type "help" followed by a class name for a list of
1723 commands in that class.
1724 Type "help" followed by command name for full
1726 Command name abbreviations are allowed if unambiguous.
1729 @c the above line break eliminates huge line overfull...
1731 @item help @var{class}
1732 Using one of the general help classes as an argument, you can get a
1733 list of the individual commands in that class. For example, here is the
1734 help display for the class @code{status}:
1737 (@value{GDBP}) help status
1742 @c Line break in "show" line falsifies real output, but needed
1743 @c to fit in smallbook page size.
1744 info -- Generic command for showing things
1745 about the program being debugged
1746 show -- Generic command for showing things
1749 Type "help" followed by command name for full
1751 Command name abbreviations are allowed if unambiguous.
1755 @item help @var{command}
1756 With a command name as @code{help} argument, @value{GDBN} displays a
1757 short paragraph on how to use that command.
1760 @item apropos @var{args}
1761 The @code{apropos} command searches through all of the @value{GDBN}
1762 commands, and their documentation, for the regular expression specified in
1763 @var{args}. It prints out all matches found. For example:
1774 alias -- Define a new command that is an alias of an existing command
1775 aliases -- Aliases of other commands
1776 d -- Delete some breakpoints or auto-display expressions
1777 del -- Delete some breakpoints or auto-display expressions
1778 delete -- Delete some breakpoints or auto-display expressions
1783 @item complete @var{args}
1784 The @code{complete @var{args}} command lists all the possible completions
1785 for the beginning of a command. Use @var{args} to specify the beginning of the
1786 command you want completed. For example:
1792 @noindent results in:
1803 @noindent This is intended for use by @sc{gnu} Emacs.
1806 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1807 and @code{show} to inquire about the state of your program, or the state
1808 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1809 manual introduces each of them in the appropriate context. The listings
1810 under @code{info} and under @code{show} in the Command, Variable, and
1811 Function Index point to all the sub-commands. @xref{Command and Variable
1817 @kindex i @r{(@code{info})}
1819 This command (abbreviated @code{i}) is for describing the state of your
1820 program. For example, you can show the arguments passed to a function
1821 with @code{info args}, list the registers currently in use with @code{info
1822 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1823 You can get a complete list of the @code{info} sub-commands with
1824 @w{@code{help info}}.
1828 You can assign the result of an expression to an environment variable with
1829 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1830 @code{set prompt $}.
1834 In contrast to @code{info}, @code{show} is for describing the state of
1835 @value{GDBN} itself.
1836 You can change most of the things you can @code{show}, by using the
1837 related command @code{set}; for example, you can control what number
1838 system is used for displays with @code{set radix}, or simply inquire
1839 which is currently in use with @code{show radix}.
1842 To display all the settable parameters and their current
1843 values, you can use @code{show} with no arguments; you may also use
1844 @code{info set}. Both commands produce the same display.
1845 @c FIXME: "info set" violates the rule that "info" is for state of
1846 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1847 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1851 Here are several miscellaneous @code{show} subcommands, all of which are
1852 exceptional in lacking corresponding @code{set} commands:
1855 @kindex show version
1856 @cindex @value{GDBN} version number
1858 Show what version of @value{GDBN} is running. You should include this
1859 information in @value{GDBN} bug-reports. If multiple versions of
1860 @value{GDBN} are in use at your site, you may need to determine which
1861 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1862 commands are introduced, and old ones may wither away. Also, many
1863 system vendors ship variant versions of @value{GDBN}, and there are
1864 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1865 The version number is the same as the one announced when you start
1868 @kindex show copying
1869 @kindex info copying
1870 @cindex display @value{GDBN} copyright
1873 Display information about permission for copying @value{GDBN}.
1875 @kindex show warranty
1876 @kindex info warranty
1878 @itemx info warranty
1879 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1880 if your version of @value{GDBN} comes with one.
1882 @kindex show configuration
1883 @item show configuration
1884 Display detailed information about the way @value{GDBN} was configured
1885 when it was built. This displays the optional arguments passed to the
1886 @file{configure} script and also configuration parameters detected
1887 automatically by @command{configure}. When reporting a @value{GDBN}
1888 bug (@pxref{GDB Bugs}), it is important to include this information in
1894 @chapter Running Programs Under @value{GDBN}
1896 When you run a program under @value{GDBN}, you must first generate
1897 debugging information when you compile it.
1899 You may start @value{GDBN} with its arguments, if any, in an environment
1900 of your choice. If you are doing native debugging, you may redirect
1901 your program's input and output, debug an already running process, or
1902 kill a child process.
1905 * Compilation:: Compiling for debugging
1906 * Starting:: Starting your program
1907 * Arguments:: Your program's arguments
1908 * Environment:: Your program's environment
1910 * Working Directory:: Your program's working directory
1911 * Input/Output:: Your program's input and output
1912 * Attach:: Debugging an already-running process
1913 * Kill Process:: Killing the child process
1915 * Inferiors and Programs:: Debugging multiple inferiors and programs
1916 * Threads:: Debugging programs with multiple threads
1917 * Forks:: Debugging forks
1918 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1922 @section Compiling for Debugging
1924 In order to debug a program effectively, you need to generate
1925 debugging information when you compile it. This debugging information
1926 is stored in the object file; it describes the data type of each
1927 variable or function and the correspondence between source line numbers
1928 and addresses in the executable code.
1930 To request debugging information, specify the @samp{-g} option when you run
1933 Programs that are to be shipped to your customers are compiled with
1934 optimizations, using the @samp{-O} compiler option. However, some
1935 compilers are unable to handle the @samp{-g} and @samp{-O} options
1936 together. Using those compilers, you cannot generate optimized
1937 executables containing debugging information.
1939 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1940 without @samp{-O}, making it possible to debug optimized code. We
1941 recommend that you @emph{always} use @samp{-g} whenever you compile a
1942 program. You may think your program is correct, but there is no sense
1943 in pushing your luck. For more information, see @ref{Optimized Code}.
1945 Older versions of the @sc{gnu} C compiler permitted a variant option
1946 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1947 format; if your @sc{gnu} C compiler has this option, do not use it.
1949 @value{GDBN} knows about preprocessor macros and can show you their
1950 expansion (@pxref{Macros}). Most compilers do not include information
1951 about preprocessor macros in the debugging information if you specify
1952 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1953 the @sc{gnu} C compiler, provides macro information if you are using
1954 the DWARF debugging format, and specify the option @option{-g3}.
1956 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1957 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1958 information on @value{NGCC} options affecting debug information.
1960 You will have the best debugging experience if you use the latest
1961 version of the DWARF debugging format that your compiler supports.
1962 DWARF is currently the most expressive and best supported debugging
1963 format in @value{GDBN}.
1967 @section Starting your Program
1973 @kindex r @r{(@code{run})}
1976 Use the @code{run} command to start your program under @value{GDBN}.
1977 You must first specify the program name (except on VxWorks) with an
1978 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1979 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1980 (@pxref{Files, ,Commands to Specify Files}).
1984 If you are running your program in an execution environment that
1985 supports processes, @code{run} creates an inferior process and makes
1986 that process run your program. In some environments without processes,
1987 @code{run} jumps to the start of your program. Other targets,
1988 like @samp{remote}, are always running. If you get an error
1989 message like this one:
1992 The "remote" target does not support "run".
1993 Try "help target" or "continue".
1997 then use @code{continue} to run your program. You may need @code{load}
1998 first (@pxref{load}).
2000 The execution of a program is affected by certain information it
2001 receives from its superior. @value{GDBN} provides ways to specify this
2002 information, which you must do @emph{before} starting your program. (You
2003 can change it after starting your program, but such changes only affect
2004 your program the next time you start it.) This information may be
2005 divided into four categories:
2008 @item The @emph{arguments.}
2009 Specify the arguments to give your program as the arguments of the
2010 @code{run} command. If a shell is available on your target, the shell
2011 is used to pass the arguments, so that you may use normal conventions
2012 (such as wildcard expansion or variable substitution) in describing
2014 In Unix systems, you can control which shell is used with the
2015 @code{SHELL} environment variable. If you do not define @code{SHELL},
2016 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2017 use of any shell with the @code{set startup-with-shell} command (see
2020 @item The @emph{environment.}
2021 Your program normally inherits its environment from @value{GDBN}, but you can
2022 use the @value{GDBN} commands @code{set environment} and @code{unset
2023 environment} to change parts of the environment that affect
2024 your program. @xref{Environment, ,Your Program's Environment}.
2026 @item The @emph{working directory.}
2027 Your program inherits its working directory from @value{GDBN}. You can set
2028 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2029 @xref{Working Directory, ,Your Program's Working Directory}.
2031 @item The @emph{standard input and output.}
2032 Your program normally uses the same device for standard input and
2033 standard output as @value{GDBN} is using. You can redirect input and output
2034 in the @code{run} command line, or you can use the @code{tty} command to
2035 set a different device for your program.
2036 @xref{Input/Output, ,Your Program's Input and Output}.
2039 @emph{Warning:} While input and output redirection work, you cannot use
2040 pipes to pass the output of the program you are debugging to another
2041 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2045 When you issue the @code{run} command, your program begins to execute
2046 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2047 of how to arrange for your program to stop. Once your program has
2048 stopped, you may call functions in your program, using the @code{print}
2049 or @code{call} commands. @xref{Data, ,Examining Data}.
2051 If the modification time of your symbol file has changed since the last
2052 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2053 table, and reads it again. When it does this, @value{GDBN} tries to retain
2054 your current breakpoints.
2059 @cindex run to main procedure
2060 The name of the main procedure can vary from language to language.
2061 With C or C@t{++}, the main procedure name is always @code{main}, but
2062 other languages such as Ada do not require a specific name for their
2063 main procedure. The debugger provides a convenient way to start the
2064 execution of the program and to stop at the beginning of the main
2065 procedure, depending on the language used.
2067 The @samp{start} command does the equivalent of setting a temporary
2068 breakpoint at the beginning of the main procedure and then invoking
2069 the @samp{run} command.
2071 @cindex elaboration phase
2072 Some programs contain an @dfn{elaboration} phase where some startup code is
2073 executed before the main procedure is called. This depends on the
2074 languages used to write your program. In C@t{++}, for instance,
2075 constructors for static and global objects are executed before
2076 @code{main} is called. It is therefore possible that the debugger stops
2077 before reaching the main procedure. However, the temporary breakpoint
2078 will remain to halt execution.
2080 Specify the arguments to give to your program as arguments to the
2081 @samp{start} command. These arguments will be given verbatim to the
2082 underlying @samp{run} command. Note that the same arguments will be
2083 reused if no argument is provided during subsequent calls to
2084 @samp{start} or @samp{run}.
2086 It is sometimes necessary to debug the program during elaboration. In
2087 these cases, using the @code{start} command would stop the execution of
2088 your program too late, as the program would have already completed the
2089 elaboration phase. Under these circumstances, insert breakpoints in your
2090 elaboration code before running your program.
2092 @anchor{set exec-wrapper}
2093 @kindex set exec-wrapper
2094 @item set exec-wrapper @var{wrapper}
2095 @itemx show exec-wrapper
2096 @itemx unset exec-wrapper
2097 When @samp{exec-wrapper} is set, the specified wrapper is used to
2098 launch programs for debugging. @value{GDBN} starts your program
2099 with a shell command of the form @kbd{exec @var{wrapper}
2100 @var{program}}. Quoting is added to @var{program} and its
2101 arguments, but not to @var{wrapper}, so you should add quotes if
2102 appropriate for your shell. The wrapper runs until it executes
2103 your program, and then @value{GDBN} takes control.
2105 You can use any program that eventually calls @code{execve} with
2106 its arguments as a wrapper. Several standard Unix utilities do
2107 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2108 with @code{exec "$@@"} will also work.
2110 For example, you can use @code{env} to pass an environment variable to
2111 the debugged program, without setting the variable in your shell's
2115 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2119 This command is available when debugging locally on most targets, excluding
2120 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2122 @kindex set startup-with-shell
2123 @item set startup-with-shell
2124 @itemx set startup-with-shell on
2125 @itemx set startup-with-shell off
2126 @itemx show set startup-with-shell
2127 On Unix systems, by default, if a shell is available on your target,
2128 @value{GDBN}) uses it to start your program. Arguments of the
2129 @code{run} command are passed to the shell, which does variable
2130 substitution, expands wildcard characters and performs redirection of
2131 I/O. In some circumstances, it may be useful to disable such use of a
2132 shell, for example, when debugging the shell itself or diagnosing
2133 startup failures such as:
2137 Starting program: ./a.out
2138 During startup program terminated with signal SIGSEGV, Segmentation fault.
2142 which indicates the shell or the wrapper specified with
2143 @samp{exec-wrapper} crashed, not your program. Most often, this is
2144 caused by something odd in your shell's non-interactive mode
2145 initialization file---such as @file{.cshrc} for C-shell,
2146 $@file{.zshenv} for the Z shell, or the file specified in the
2147 @samp{BASH_ENV} environment variable for BASH.
2149 @kindex set disable-randomization
2150 @item set disable-randomization
2151 @itemx set disable-randomization on
2152 This option (enabled by default in @value{GDBN}) will turn off the native
2153 randomization of the virtual address space of the started program. This option
2154 is useful for multiple debugging sessions to make the execution better
2155 reproducible and memory addresses reusable across debugging sessions.
2157 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2158 On @sc{gnu}/Linux you can get the same behavior using
2161 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2164 @item set disable-randomization off
2165 Leave the behavior of the started executable unchanged. Some bugs rear their
2166 ugly heads only when the program is loaded at certain addresses. If your bug
2167 disappears when you run the program under @value{GDBN}, that might be because
2168 @value{GDBN} by default disables the address randomization on platforms, such
2169 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2170 disable-randomization off} to try to reproduce such elusive bugs.
2172 On targets where it is available, virtual address space randomization
2173 protects the programs against certain kinds of security attacks. In these
2174 cases the attacker needs to know the exact location of a concrete executable
2175 code. Randomizing its location makes it impossible to inject jumps misusing
2176 a code at its expected addresses.
2178 Prelinking shared libraries provides a startup performance advantage but it
2179 makes addresses in these libraries predictable for privileged processes by
2180 having just unprivileged access at the target system. Reading the shared
2181 library binary gives enough information for assembling the malicious code
2182 misusing it. Still even a prelinked shared library can get loaded at a new
2183 random address just requiring the regular relocation process during the
2184 startup. Shared libraries not already prelinked are always loaded at
2185 a randomly chosen address.
2187 Position independent executables (PIE) contain position independent code
2188 similar to the shared libraries and therefore such executables get loaded at
2189 a randomly chosen address upon startup. PIE executables always load even
2190 already prelinked shared libraries at a random address. You can build such
2191 executable using @command{gcc -fPIE -pie}.
2193 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2194 (as long as the randomization is enabled).
2196 @item show disable-randomization
2197 Show the current setting of the explicit disable of the native randomization of
2198 the virtual address space of the started program.
2203 @section Your Program's Arguments
2205 @cindex arguments (to your program)
2206 The arguments to your program can be specified by the arguments of the
2208 They are passed to a shell, which expands wildcard characters and
2209 performs redirection of I/O, and thence to your program. Your
2210 @code{SHELL} environment variable (if it exists) specifies what shell
2211 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2212 the default shell (@file{/bin/sh} on Unix).
2214 On non-Unix systems, the program is usually invoked directly by
2215 @value{GDBN}, which emulates I/O redirection via the appropriate system
2216 calls, and the wildcard characters are expanded by the startup code of
2217 the program, not by the shell.
2219 @code{run} with no arguments uses the same arguments used by the previous
2220 @code{run}, or those set by the @code{set args} command.
2225 Specify the arguments to be used the next time your program is run. If
2226 @code{set args} has no arguments, @code{run} executes your program
2227 with no arguments. Once you have run your program with arguments,
2228 using @code{set args} before the next @code{run} is the only way to run
2229 it again without arguments.
2233 Show the arguments to give your program when it is started.
2237 @section Your Program's Environment
2239 @cindex environment (of your program)
2240 The @dfn{environment} consists of a set of environment variables and
2241 their values. Environment variables conventionally record such things as
2242 your user name, your home directory, your terminal type, and your search
2243 path for programs to run. Usually you set up environment variables with
2244 the shell and they are inherited by all the other programs you run. When
2245 debugging, it can be useful to try running your program with a modified
2246 environment without having to start @value{GDBN} over again.
2250 @item path @var{directory}
2251 Add @var{directory} to the front of the @code{PATH} environment variable
2252 (the search path for executables) that will be passed to your program.
2253 The value of @code{PATH} used by @value{GDBN} does not change.
2254 You may specify several directory names, separated by whitespace or by a
2255 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2256 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2257 is moved to the front, so it is searched sooner.
2259 You can use the string @samp{$cwd} to refer to whatever is the current
2260 working directory at the time @value{GDBN} searches the path. If you
2261 use @samp{.} instead, it refers to the directory where you executed the
2262 @code{path} command. @value{GDBN} replaces @samp{.} in the
2263 @var{directory} argument (with the current path) before adding
2264 @var{directory} to the search path.
2265 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2266 @c document that, since repeating it would be a no-op.
2270 Display the list of search paths for executables (the @code{PATH}
2271 environment variable).
2273 @kindex show environment
2274 @item show environment @r{[}@var{varname}@r{]}
2275 Print the value of environment variable @var{varname} to be given to
2276 your program when it starts. If you do not supply @var{varname},
2277 print the names and values of all environment variables to be given to
2278 your program. You can abbreviate @code{environment} as @code{env}.
2280 @kindex set environment
2281 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2282 Set environment variable @var{varname} to @var{value}. The value
2283 changes for your program (and the shell @value{GDBN} uses to launch
2284 it), not for @value{GDBN} itself. @var{value} may be any string; the
2285 values of environment variables are just strings, and any
2286 interpretation is supplied by your program itself. The @var{value}
2287 parameter is optional; if it is eliminated, the variable is set to a
2289 @c "any string" here does not include leading, trailing
2290 @c blanks. Gnu asks: does anyone care?
2292 For example, this command:
2299 tells the debugged program, when subsequently run, that its user is named
2300 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2301 are not actually required.)
2303 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2304 which also inherits the environment set with @code{set environment}.
2305 If necessary, you can avoid that by using the @samp{env} program as a
2306 wrapper instead of using @code{set environment}. @xref{set
2307 exec-wrapper}, for an example doing just that.
2309 @kindex unset environment
2310 @item unset environment @var{varname}
2311 Remove variable @var{varname} from the environment to be passed to your
2312 program. This is different from @samp{set env @var{varname} =};
2313 @code{unset environment} removes the variable from the environment,
2314 rather than assigning it an empty value.
2317 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2318 the shell indicated by your @code{SHELL} environment variable if it
2319 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2320 names a shell that runs an initialization file when started
2321 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2322 for the Z shell, or the file specified in the @samp{BASH_ENV}
2323 environment variable for BASH---any variables you set in that file
2324 affect your program. You may wish to move setting of environment
2325 variables to files that are only run when you sign on, such as
2326 @file{.login} or @file{.profile}.
2328 @node Working Directory
2329 @section Your Program's Working Directory
2331 @cindex working directory (of your program)
2332 Each time you start your program with @code{run}, it inherits its
2333 working directory from the current working directory of @value{GDBN}.
2334 The @value{GDBN} working directory is initially whatever it inherited
2335 from its parent process (typically the shell), but you can specify a new
2336 working directory in @value{GDBN} with the @code{cd} command.
2338 The @value{GDBN} working directory also serves as a default for the commands
2339 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2344 @cindex change working directory
2345 @item cd @r{[}@var{directory}@r{]}
2346 Set the @value{GDBN} working directory to @var{directory}. If not
2347 given, @var{directory} uses @file{'~'}.
2351 Print the @value{GDBN} working directory.
2354 It is generally impossible to find the current working directory of
2355 the process being debugged (since a program can change its directory
2356 during its run). If you work on a system where @value{GDBN} is
2357 configured with the @file{/proc} support, you can use the @code{info
2358 proc} command (@pxref{SVR4 Process Information}) to find out the
2359 current working directory of the debuggee.
2362 @section Your Program's Input and Output
2367 By default, the program you run under @value{GDBN} does input and output to
2368 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2369 to its own terminal modes to interact with you, but it records the terminal
2370 modes your program was using and switches back to them when you continue
2371 running your program.
2374 @kindex info terminal
2376 Displays information recorded by @value{GDBN} about the terminal modes your
2380 You can redirect your program's input and/or output using shell
2381 redirection with the @code{run} command. For example,
2388 starts your program, diverting its output to the file @file{outfile}.
2391 @cindex controlling terminal
2392 Another way to specify where your program should do input and output is
2393 with the @code{tty} command. This command accepts a file name as
2394 argument, and causes this file to be the default for future @code{run}
2395 commands. It also resets the controlling terminal for the child
2396 process, for future @code{run} commands. For example,
2403 directs that processes started with subsequent @code{run} commands
2404 default to do input and output on the terminal @file{/dev/ttyb} and have
2405 that as their controlling terminal.
2407 An explicit redirection in @code{run} overrides the @code{tty} command's
2408 effect on the input/output device, but not its effect on the controlling
2411 When you use the @code{tty} command or redirect input in the @code{run}
2412 command, only the input @emph{for your program} is affected. The input
2413 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2414 for @code{set inferior-tty}.
2416 @cindex inferior tty
2417 @cindex set inferior controlling terminal
2418 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2419 display the name of the terminal that will be used for future runs of your
2423 @item set inferior-tty /dev/ttyb
2424 @kindex set inferior-tty
2425 Set the tty for the program being debugged to /dev/ttyb.
2427 @item show inferior-tty
2428 @kindex show inferior-tty
2429 Show the current tty for the program being debugged.
2433 @section Debugging an Already-running Process
2438 @item attach @var{process-id}
2439 This command attaches to a running process---one that was started
2440 outside @value{GDBN}. (@code{info files} shows your active
2441 targets.) The command takes as argument a process ID. The usual way to
2442 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2443 or with the @samp{jobs -l} shell command.
2445 @code{attach} does not repeat if you press @key{RET} a second time after
2446 executing the command.
2449 To use @code{attach}, your program must be running in an environment
2450 which supports processes; for example, @code{attach} does not work for
2451 programs on bare-board targets that lack an operating system. You must
2452 also have permission to send the process a signal.
2454 When you use @code{attach}, the debugger finds the program running in
2455 the process first by looking in the current working directory, then (if
2456 the program is not found) by using the source file search path
2457 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2458 the @code{file} command to load the program. @xref{Files, ,Commands to
2461 The first thing @value{GDBN} does after arranging to debug the specified
2462 process is to stop it. You can examine and modify an attached process
2463 with all the @value{GDBN} commands that are ordinarily available when
2464 you start processes with @code{run}. You can insert breakpoints; you
2465 can step and continue; you can modify storage. If you would rather the
2466 process continue running, you may use the @code{continue} command after
2467 attaching @value{GDBN} to the process.
2472 When you have finished debugging the attached process, you can use the
2473 @code{detach} command to release it from @value{GDBN} control. Detaching
2474 the process continues its execution. After the @code{detach} command,
2475 that process and @value{GDBN} become completely independent once more, and you
2476 are ready to @code{attach} another process or start one with @code{run}.
2477 @code{detach} does not repeat if you press @key{RET} again after
2478 executing the command.
2481 If you exit @value{GDBN} while you have an attached process, you detach
2482 that process. If you use the @code{run} command, you kill that process.
2483 By default, @value{GDBN} asks for confirmation if you try to do either of these
2484 things; you can control whether or not you need to confirm by using the
2485 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2489 @section Killing the Child Process
2494 Kill the child process in which your program is running under @value{GDBN}.
2497 This command is useful if you wish to debug a core dump instead of a
2498 running process. @value{GDBN} ignores any core dump file while your program
2501 On some operating systems, a program cannot be executed outside @value{GDBN}
2502 while you have breakpoints set on it inside @value{GDBN}. You can use the
2503 @code{kill} command in this situation to permit running your program
2504 outside the debugger.
2506 The @code{kill} command is also useful if you wish to recompile and
2507 relink your program, since on many systems it is impossible to modify an
2508 executable file while it is running in a process. In this case, when you
2509 next type @code{run}, @value{GDBN} notices that the file has changed, and
2510 reads the symbol table again (while trying to preserve your current
2511 breakpoint settings).
2513 @node Inferiors and Programs
2514 @section Debugging Multiple Inferiors and Programs
2516 @value{GDBN} lets you run and debug multiple programs in a single
2517 session. In addition, @value{GDBN} on some systems may let you run
2518 several programs simultaneously (otherwise you have to exit from one
2519 before starting another). In the most general case, you can have
2520 multiple threads of execution in each of multiple processes, launched
2521 from multiple executables.
2524 @value{GDBN} represents the state of each program execution with an
2525 object called an @dfn{inferior}. An inferior typically corresponds to
2526 a process, but is more general and applies also to targets that do not
2527 have processes. Inferiors may be created before a process runs, and
2528 may be retained after a process exits. Inferiors have unique
2529 identifiers that are different from process ids. Usually each
2530 inferior will also have its own distinct address space, although some
2531 embedded targets may have several inferiors running in different parts
2532 of a single address space. Each inferior may in turn have multiple
2533 threads running in it.
2535 To find out what inferiors exist at any moment, use @w{@code{info
2539 @kindex info inferiors
2540 @item info inferiors
2541 Print a list of all inferiors currently being managed by @value{GDBN}.
2543 @value{GDBN} displays for each inferior (in this order):
2547 the inferior number assigned by @value{GDBN}
2550 the target system's inferior identifier
2553 the name of the executable the inferior is running.
2558 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2559 indicates the current inferior.
2563 @c end table here to get a little more width for example
2566 (@value{GDBP}) info inferiors
2567 Num Description Executable
2568 2 process 2307 hello
2569 * 1 process 3401 goodbye
2572 To switch focus between inferiors, use the @code{inferior} command:
2575 @kindex inferior @var{infno}
2576 @item inferior @var{infno}
2577 Make inferior number @var{infno} the current inferior. The argument
2578 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2579 in the first field of the @samp{info inferiors} display.
2583 You can get multiple executables into a debugging session via the
2584 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2585 systems @value{GDBN} can add inferiors to the debug session
2586 automatically by following calls to @code{fork} and @code{exec}. To
2587 remove inferiors from the debugging session use the
2588 @w{@code{remove-inferiors}} command.
2591 @kindex add-inferior
2592 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2593 Adds @var{n} inferiors to be run using @var{executable} as the
2594 executable. @var{n} defaults to 1. If no executable is specified,
2595 the inferiors begins empty, with no program. You can still assign or
2596 change the program assigned to the inferior at any time by using the
2597 @code{file} command with the executable name as its argument.
2599 @kindex clone-inferior
2600 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2601 Adds @var{n} inferiors ready to execute the same program as inferior
2602 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2603 number of the current inferior. This is a convenient command when you
2604 want to run another instance of the inferior you are debugging.
2607 (@value{GDBP}) info inferiors
2608 Num Description Executable
2609 * 1 process 29964 helloworld
2610 (@value{GDBP}) clone-inferior
2613 (@value{GDBP}) info inferiors
2614 Num Description Executable
2616 * 1 process 29964 helloworld
2619 You can now simply switch focus to inferior 2 and run it.
2621 @kindex remove-inferiors
2622 @item remove-inferiors @var{infno}@dots{}
2623 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2624 possible to remove an inferior that is running with this command. For
2625 those, use the @code{kill} or @code{detach} command first.
2629 To quit debugging one of the running inferiors that is not the current
2630 inferior, you can either detach from it by using the @w{@code{detach
2631 inferior}} command (allowing it to run independently), or kill it
2632 using the @w{@code{kill inferiors}} command:
2635 @kindex detach inferiors @var{infno}@dots{}
2636 @item detach inferior @var{infno}@dots{}
2637 Detach from the inferior or inferiors identified by @value{GDBN}
2638 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2639 still stays on the list of inferiors shown by @code{info inferiors},
2640 but its Description will show @samp{<null>}.
2642 @kindex kill inferiors @var{infno}@dots{}
2643 @item kill inferiors @var{infno}@dots{}
2644 Kill the inferior or inferiors identified by @value{GDBN} inferior
2645 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2646 stays on the list of inferiors shown by @code{info inferiors}, but its
2647 Description will show @samp{<null>}.
2650 After the successful completion of a command such as @code{detach},
2651 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2652 a normal process exit, the inferior is still valid and listed with
2653 @code{info inferiors}, ready to be restarted.
2656 To be notified when inferiors are started or exit under @value{GDBN}'s
2657 control use @w{@code{set print inferior-events}}:
2660 @kindex set print inferior-events
2661 @cindex print messages on inferior start and exit
2662 @item set print inferior-events
2663 @itemx set print inferior-events on
2664 @itemx set print inferior-events off
2665 The @code{set print inferior-events} command allows you to enable or
2666 disable printing of messages when @value{GDBN} notices that new
2667 inferiors have started or that inferiors have exited or have been
2668 detached. By default, these messages will not be printed.
2670 @kindex show print inferior-events
2671 @item show print inferior-events
2672 Show whether messages will be printed when @value{GDBN} detects that
2673 inferiors have started, exited or have been detached.
2676 Many commands will work the same with multiple programs as with a
2677 single program: e.g., @code{print myglobal} will simply display the
2678 value of @code{myglobal} in the current inferior.
2681 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2682 get more info about the relationship of inferiors, programs, address
2683 spaces in a debug session. You can do that with the @w{@code{maint
2684 info program-spaces}} command.
2687 @kindex maint info program-spaces
2688 @item maint info program-spaces
2689 Print a list of all program spaces currently being managed by
2692 @value{GDBN} displays for each program space (in this order):
2696 the program space number assigned by @value{GDBN}
2699 the name of the executable loaded into the program space, with e.g.,
2700 the @code{file} command.
2705 An asterisk @samp{*} preceding the @value{GDBN} program space number
2706 indicates the current program space.
2708 In addition, below each program space line, @value{GDBN} prints extra
2709 information that isn't suitable to display in tabular form. For
2710 example, the list of inferiors bound to the program space.
2713 (@value{GDBP}) maint info program-spaces
2716 Bound inferiors: ID 1 (process 21561)
2720 Here we can see that no inferior is running the program @code{hello},
2721 while @code{process 21561} is running the program @code{goodbye}. On
2722 some targets, it is possible that multiple inferiors are bound to the
2723 same program space. The most common example is that of debugging both
2724 the parent and child processes of a @code{vfork} call. For example,
2727 (@value{GDBP}) maint info program-spaces
2730 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2733 Here, both inferior 2 and inferior 1 are running in the same program
2734 space as a result of inferior 1 having executed a @code{vfork} call.
2738 @section Debugging Programs with Multiple Threads
2740 @cindex threads of execution
2741 @cindex multiple threads
2742 @cindex switching threads
2743 In some operating systems, such as HP-UX and Solaris, a single program
2744 may have more than one @dfn{thread} of execution. The precise semantics
2745 of threads differ from one operating system to another, but in general
2746 the threads of a single program are akin to multiple processes---except
2747 that they share one address space (that is, they can all examine and
2748 modify the same variables). On the other hand, each thread has its own
2749 registers and execution stack, and perhaps private memory.
2751 @value{GDBN} provides these facilities for debugging multi-thread
2755 @item automatic notification of new threads
2756 @item @samp{thread @var{threadno}}, a command to switch among threads
2757 @item @samp{info threads}, a command to inquire about existing threads
2758 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2759 a command to apply a command to a list of threads
2760 @item thread-specific breakpoints
2761 @item @samp{set print thread-events}, which controls printing of
2762 messages on thread start and exit.
2763 @item @samp{set libthread-db-search-path @var{path}}, which lets
2764 the user specify which @code{libthread_db} to use if the default choice
2765 isn't compatible with the program.
2769 @emph{Warning:} These facilities are not yet available on every
2770 @value{GDBN} configuration where the operating system supports threads.
2771 If your @value{GDBN} does not support threads, these commands have no
2772 effect. For example, a system without thread support shows no output
2773 from @samp{info threads}, and always rejects the @code{thread} command,
2777 (@value{GDBP}) info threads
2778 (@value{GDBP}) thread 1
2779 Thread ID 1 not known. Use the "info threads" command to
2780 see the IDs of currently known threads.
2782 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2783 @c doesn't support threads"?
2786 @cindex focus of debugging
2787 @cindex current thread
2788 The @value{GDBN} thread debugging facility allows you to observe all
2789 threads while your program runs---but whenever @value{GDBN} takes
2790 control, one thread in particular is always the focus of debugging.
2791 This thread is called the @dfn{current thread}. Debugging commands show
2792 program information from the perspective of the current thread.
2794 @cindex @code{New} @var{systag} message
2795 @cindex thread identifier (system)
2796 @c FIXME-implementors!! It would be more helpful if the [New...] message
2797 @c included GDB's numeric thread handle, so you could just go to that
2798 @c thread without first checking `info threads'.
2799 Whenever @value{GDBN} detects a new thread in your program, it displays
2800 the target system's identification for the thread with a message in the
2801 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2802 whose form varies depending on the particular system. For example, on
2803 @sc{gnu}/Linux, you might see
2806 [New Thread 0x41e02940 (LWP 25582)]
2810 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2811 the @var{systag} is simply something like @samp{process 368}, with no
2814 @c FIXME!! (1) Does the [New...] message appear even for the very first
2815 @c thread of a program, or does it only appear for the
2816 @c second---i.e.@: when it becomes obvious we have a multithread
2818 @c (2) *Is* there necessarily a first thread always? Or do some
2819 @c multithread systems permit starting a program with multiple
2820 @c threads ab initio?
2822 @cindex thread number
2823 @cindex thread identifier (GDB)
2824 For debugging purposes, @value{GDBN} associates its own thread
2825 number---always a single integer---with each thread in your program.
2828 @kindex info threads
2829 @item info threads @r{[}@var{id}@dots{}@r{]}
2830 Display a summary of all threads currently in your program. Optional
2831 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2832 means to print information only about the specified thread or threads.
2833 @value{GDBN} displays for each thread (in this order):
2837 the thread number assigned by @value{GDBN}
2840 the target system's thread identifier (@var{systag})
2843 the thread's name, if one is known. A thread can either be named by
2844 the user (see @code{thread name}, below), or, in some cases, by the
2848 the current stack frame summary for that thread
2852 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2853 indicates the current thread.
2857 @c end table here to get a little more width for example
2860 (@value{GDBP}) info threads
2862 3 process 35 thread 27 0x34e5 in sigpause ()
2863 2 process 35 thread 23 0x34e5 in sigpause ()
2864 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2868 On Solaris, you can display more information about user threads with a
2869 Solaris-specific command:
2872 @item maint info sol-threads
2873 @kindex maint info sol-threads
2874 @cindex thread info (Solaris)
2875 Display info on Solaris user threads.
2879 @kindex thread @var{threadno}
2880 @item thread @var{threadno}
2881 Make thread number @var{threadno} the current thread. The command
2882 argument @var{threadno} is the internal @value{GDBN} thread number, as
2883 shown in the first field of the @samp{info threads} display.
2884 @value{GDBN} responds by displaying the system identifier of the thread
2885 you selected, and its current stack frame summary:
2888 (@value{GDBP}) thread 2
2889 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2890 #0 some_function (ignore=0x0) at example.c:8
2891 8 printf ("hello\n");
2895 As with the @samp{[New @dots{}]} message, the form of the text after
2896 @samp{Switching to} depends on your system's conventions for identifying
2899 @vindex $_thread@r{, convenience variable}
2900 The debugger convenience variable @samp{$_thread} contains the number
2901 of the current thread. You may find this useful in writing breakpoint
2902 conditional expressions, command scripts, and so forth. See
2903 @xref{Convenience Vars,, Convenience Variables}, for general
2904 information on convenience variables.
2906 @kindex thread apply
2907 @cindex apply command to several threads
2908 @item thread apply [@var{threadno} | all] @var{command}
2909 The @code{thread apply} command allows you to apply the named
2910 @var{command} to one or more threads. Specify the numbers of the
2911 threads that you want affected with the command argument
2912 @var{threadno}. It can be a single thread number, one of the numbers
2913 shown in the first field of the @samp{info threads} display; or it
2914 could be a range of thread numbers, as in @code{2-4}. To apply a
2915 command to all threads, type @kbd{thread apply all @var{command}}.
2918 @cindex name a thread
2919 @item thread name [@var{name}]
2920 This command assigns a name to the current thread. If no argument is
2921 given, any existing user-specified name is removed. The thread name
2922 appears in the @samp{info threads} display.
2924 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2925 determine the name of the thread as given by the OS. On these
2926 systems, a name specified with @samp{thread name} will override the
2927 system-give name, and removing the user-specified name will cause
2928 @value{GDBN} to once again display the system-specified name.
2931 @cindex search for a thread
2932 @item thread find [@var{regexp}]
2933 Search for and display thread ids whose name or @var{systag}
2934 matches the supplied regular expression.
2936 As well as being the complement to the @samp{thread name} command,
2937 this command also allows you to identify a thread by its target
2938 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2942 (@value{GDBN}) thread find 26688
2943 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2944 (@value{GDBN}) info thread 4
2946 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2949 @kindex set print thread-events
2950 @cindex print messages on thread start and exit
2951 @item set print thread-events
2952 @itemx set print thread-events on
2953 @itemx set print thread-events off
2954 The @code{set print thread-events} command allows you to enable or
2955 disable printing of messages when @value{GDBN} notices that new threads have
2956 started or that threads have exited. By default, these messages will
2957 be printed if detection of these events is supported by the target.
2958 Note that these messages cannot be disabled on all targets.
2960 @kindex show print thread-events
2961 @item show print thread-events
2962 Show whether messages will be printed when @value{GDBN} detects that threads
2963 have started and exited.
2966 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2967 more information about how @value{GDBN} behaves when you stop and start
2968 programs with multiple threads.
2970 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2971 watchpoints in programs with multiple threads.
2973 @anchor{set libthread-db-search-path}
2975 @kindex set libthread-db-search-path
2976 @cindex search path for @code{libthread_db}
2977 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2978 If this variable is set, @var{path} is a colon-separated list of
2979 directories @value{GDBN} will use to search for @code{libthread_db}.
2980 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2981 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2982 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2985 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2986 @code{libthread_db} library to obtain information about threads in the
2987 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2988 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2989 specific thread debugging library loading is enabled
2990 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2992 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2993 refers to the default system directories that are
2994 normally searched for loading shared libraries. The @samp{$sdir} entry
2995 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2996 (@pxref{libthread_db.so.1 file}).
2998 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2999 refers to the directory from which @code{libpthread}
3000 was loaded in the inferior process.
3002 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3003 @value{GDBN} attempts to initialize it with the current inferior process.
3004 If this initialization fails (which could happen because of a version
3005 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3006 will unload @code{libthread_db}, and continue with the next directory.
3007 If none of @code{libthread_db} libraries initialize successfully,
3008 @value{GDBN} will issue a warning and thread debugging will be disabled.
3010 Setting @code{libthread-db-search-path} is currently implemented
3011 only on some platforms.
3013 @kindex show libthread-db-search-path
3014 @item show libthread-db-search-path
3015 Display current libthread_db search path.
3017 @kindex set debug libthread-db
3018 @kindex show debug libthread-db
3019 @cindex debugging @code{libthread_db}
3020 @item set debug libthread-db
3021 @itemx show debug libthread-db
3022 Turns on or off display of @code{libthread_db}-related events.
3023 Use @code{1} to enable, @code{0} to disable.
3027 @section Debugging Forks
3029 @cindex fork, debugging programs which call
3030 @cindex multiple processes
3031 @cindex processes, multiple
3032 On most systems, @value{GDBN} has no special support for debugging
3033 programs which create additional processes using the @code{fork}
3034 function. When a program forks, @value{GDBN} will continue to debug the
3035 parent process and the child process will run unimpeded. If you have
3036 set a breakpoint in any code which the child then executes, the child
3037 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3038 will cause it to terminate.
3040 However, if you want to debug the child process there is a workaround
3041 which isn't too painful. Put a call to @code{sleep} in the code which
3042 the child process executes after the fork. It may be useful to sleep
3043 only if a certain environment variable is set, or a certain file exists,
3044 so that the delay need not occur when you don't want to run @value{GDBN}
3045 on the child. While the child is sleeping, use the @code{ps} program to
3046 get its process ID. Then tell @value{GDBN} (a new invocation of
3047 @value{GDBN} if you are also debugging the parent process) to attach to
3048 the child process (@pxref{Attach}). From that point on you can debug
3049 the child process just like any other process which you attached to.
3051 On some systems, @value{GDBN} provides support for debugging programs that
3052 create additional processes using the @code{fork} or @code{vfork} functions.
3053 Currently, the only platforms with this feature are HP-UX (11.x and later
3054 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
3056 By default, when a program forks, @value{GDBN} will continue to debug
3057 the parent process and the child process will run unimpeded.
3059 If you want to follow the child process instead of the parent process,
3060 use the command @w{@code{set follow-fork-mode}}.
3063 @kindex set follow-fork-mode
3064 @item set follow-fork-mode @var{mode}
3065 Set the debugger response to a program call of @code{fork} or
3066 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3067 process. The @var{mode} argument can be:
3071 The original process is debugged after a fork. The child process runs
3072 unimpeded. This is the default.
3075 The new process is debugged after a fork. The parent process runs
3080 @kindex show follow-fork-mode
3081 @item show follow-fork-mode
3082 Display the current debugger response to a @code{fork} or @code{vfork} call.
3085 @cindex debugging multiple processes
3086 On Linux, if you want to debug both the parent and child processes, use the
3087 command @w{@code{set detach-on-fork}}.
3090 @kindex set detach-on-fork
3091 @item set detach-on-fork @var{mode}
3092 Tells gdb whether to detach one of the processes after a fork, or
3093 retain debugger control over them both.
3097 The child process (or parent process, depending on the value of
3098 @code{follow-fork-mode}) will be detached and allowed to run
3099 independently. This is the default.
3102 Both processes will be held under the control of @value{GDBN}.
3103 One process (child or parent, depending on the value of
3104 @code{follow-fork-mode}) is debugged as usual, while the other
3109 @kindex show detach-on-fork
3110 @item show detach-on-fork
3111 Show whether detach-on-fork mode is on/off.
3114 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3115 will retain control of all forked processes (including nested forks).
3116 You can list the forked processes under the control of @value{GDBN} by
3117 using the @w{@code{info inferiors}} command, and switch from one fork
3118 to another by using the @code{inferior} command (@pxref{Inferiors and
3119 Programs, ,Debugging Multiple Inferiors and Programs}).
3121 To quit debugging one of the forked processes, you can either detach
3122 from it by using the @w{@code{detach inferiors}} command (allowing it
3123 to run independently), or kill it using the @w{@code{kill inferiors}}
3124 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3127 If you ask to debug a child process and a @code{vfork} is followed by an
3128 @code{exec}, @value{GDBN} executes the new target up to the first
3129 breakpoint in the new target. If you have a breakpoint set on
3130 @code{main} in your original program, the breakpoint will also be set on
3131 the child process's @code{main}.
3133 On some systems, when a child process is spawned by @code{vfork}, you
3134 cannot debug the child or parent until an @code{exec} call completes.
3136 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3137 call executes, the new target restarts. To restart the parent
3138 process, use the @code{file} command with the parent executable name
3139 as its argument. By default, after an @code{exec} call executes,
3140 @value{GDBN} discards the symbols of the previous executable image.
3141 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3145 @kindex set follow-exec-mode
3146 @item set follow-exec-mode @var{mode}
3148 Set debugger response to a program call of @code{exec}. An
3149 @code{exec} call replaces the program image of a process.
3151 @code{follow-exec-mode} can be:
3155 @value{GDBN} creates a new inferior and rebinds the process to this
3156 new inferior. The program the process was running before the
3157 @code{exec} call can be restarted afterwards by restarting the
3163 (@value{GDBP}) info inferiors
3165 Id Description Executable
3168 process 12020 is executing new program: prog2
3169 Program exited normally.
3170 (@value{GDBP}) info inferiors
3171 Id Description Executable
3177 @value{GDBN} keeps the process bound to the same inferior. The new
3178 executable image replaces the previous executable loaded in the
3179 inferior. Restarting the inferior after the @code{exec} call, with
3180 e.g., the @code{run} command, restarts the executable the process was
3181 running after the @code{exec} call. This is the default mode.
3186 (@value{GDBP}) info inferiors
3187 Id Description Executable
3190 process 12020 is executing new program: prog2
3191 Program exited normally.
3192 (@value{GDBP}) info inferiors
3193 Id Description Executable
3200 You can use the @code{catch} command to make @value{GDBN} stop whenever
3201 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3202 Catchpoints, ,Setting Catchpoints}.
3204 @node Checkpoint/Restart
3205 @section Setting a @emph{Bookmark} to Return to Later
3210 @cindex snapshot of a process
3211 @cindex rewind program state
3213 On certain operating systems@footnote{Currently, only
3214 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3215 program's state, called a @dfn{checkpoint}, and come back to it
3218 Returning to a checkpoint effectively undoes everything that has
3219 happened in the program since the @code{checkpoint} was saved. This
3220 includes changes in memory, registers, and even (within some limits)
3221 system state. Effectively, it is like going back in time to the
3222 moment when the checkpoint was saved.
3224 Thus, if you're stepping thru a program and you think you're
3225 getting close to the point where things go wrong, you can save
3226 a checkpoint. Then, if you accidentally go too far and miss
3227 the critical statement, instead of having to restart your program
3228 from the beginning, you can just go back to the checkpoint and
3229 start again from there.
3231 This can be especially useful if it takes a lot of time or
3232 steps to reach the point where you think the bug occurs.
3234 To use the @code{checkpoint}/@code{restart} method of debugging:
3239 Save a snapshot of the debugged program's current execution state.
3240 The @code{checkpoint} command takes no arguments, but each checkpoint
3241 is assigned a small integer id, similar to a breakpoint id.
3243 @kindex info checkpoints
3244 @item info checkpoints
3245 List the checkpoints that have been saved in the current debugging
3246 session. For each checkpoint, the following information will be
3253 @item Source line, or label
3256 @kindex restart @var{checkpoint-id}
3257 @item restart @var{checkpoint-id}
3258 Restore the program state that was saved as checkpoint number
3259 @var{checkpoint-id}. All program variables, registers, stack frames
3260 etc.@: will be returned to the values that they had when the checkpoint
3261 was saved. In essence, gdb will ``wind back the clock'' to the point
3262 in time when the checkpoint was saved.
3264 Note that breakpoints, @value{GDBN} variables, command history etc.
3265 are not affected by restoring a checkpoint. In general, a checkpoint
3266 only restores things that reside in the program being debugged, not in
3269 @kindex delete checkpoint @var{checkpoint-id}
3270 @item delete checkpoint @var{checkpoint-id}
3271 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3275 Returning to a previously saved checkpoint will restore the user state
3276 of the program being debugged, plus a significant subset of the system
3277 (OS) state, including file pointers. It won't ``un-write'' data from
3278 a file, but it will rewind the file pointer to the previous location,
3279 so that the previously written data can be overwritten. For files
3280 opened in read mode, the pointer will also be restored so that the
3281 previously read data can be read again.
3283 Of course, characters that have been sent to a printer (or other
3284 external device) cannot be ``snatched back'', and characters received
3285 from eg.@: a serial device can be removed from internal program buffers,
3286 but they cannot be ``pushed back'' into the serial pipeline, ready to
3287 be received again. Similarly, the actual contents of files that have
3288 been changed cannot be restored (at this time).
3290 However, within those constraints, you actually can ``rewind'' your
3291 program to a previously saved point in time, and begin debugging it
3292 again --- and you can change the course of events so as to debug a
3293 different execution path this time.
3295 @cindex checkpoints and process id
3296 Finally, there is one bit of internal program state that will be
3297 different when you return to a checkpoint --- the program's process
3298 id. Each checkpoint will have a unique process id (or @var{pid}),
3299 and each will be different from the program's original @var{pid}.
3300 If your program has saved a local copy of its process id, this could
3301 potentially pose a problem.
3303 @subsection A Non-obvious Benefit of Using Checkpoints
3305 On some systems such as @sc{gnu}/Linux, address space randomization
3306 is performed on new processes for security reasons. This makes it
3307 difficult or impossible to set a breakpoint, or watchpoint, on an
3308 absolute address if you have to restart the program, since the
3309 absolute location of a symbol will change from one execution to the
3312 A checkpoint, however, is an @emph{identical} copy of a process.
3313 Therefore if you create a checkpoint at (eg.@:) the start of main,
3314 and simply return to that checkpoint instead of restarting the
3315 process, you can avoid the effects of address randomization and
3316 your symbols will all stay in the same place.
3319 @chapter Stopping and Continuing
3321 The principal purposes of using a debugger are so that you can stop your
3322 program before it terminates; or so that, if your program runs into
3323 trouble, you can investigate and find out why.
3325 Inside @value{GDBN}, your program may stop for any of several reasons,
3326 such as a signal, a breakpoint, or reaching a new line after a
3327 @value{GDBN} command such as @code{step}. You may then examine and
3328 change variables, set new breakpoints or remove old ones, and then
3329 continue execution. Usually, the messages shown by @value{GDBN} provide
3330 ample explanation of the status of your program---but you can also
3331 explicitly request this information at any time.
3334 @kindex info program
3336 Display information about the status of your program: whether it is
3337 running or not, what process it is, and why it stopped.
3341 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3342 * Continuing and Stepping:: Resuming execution
3343 * Skipping Over Functions and Files::
3344 Skipping over functions and files
3346 * Thread Stops:: Stopping and starting multi-thread programs
3350 @section Breakpoints, Watchpoints, and Catchpoints
3353 A @dfn{breakpoint} makes your program stop whenever a certain point in
3354 the program is reached. For each breakpoint, you can add conditions to
3355 control in finer detail whether your program stops. You can set
3356 breakpoints with the @code{break} command and its variants (@pxref{Set
3357 Breaks, ,Setting Breakpoints}), to specify the place where your program
3358 should stop by line number, function name or exact address in the
3361 On some systems, you can set breakpoints in shared libraries before
3362 the executable is run. There is a minor limitation on HP-UX systems:
3363 you must wait until the executable is run in order to set breakpoints
3364 in shared library routines that are not called directly by the program
3365 (for example, routines that are arguments in a @code{pthread_create}
3369 @cindex data breakpoints
3370 @cindex memory tracing
3371 @cindex breakpoint on memory address
3372 @cindex breakpoint on variable modification
3373 A @dfn{watchpoint} is a special breakpoint that stops your program
3374 when the value of an expression changes. The expression may be a value
3375 of a variable, or it could involve values of one or more variables
3376 combined by operators, such as @samp{a + b}. This is sometimes called
3377 @dfn{data breakpoints}. You must use a different command to set
3378 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3379 from that, you can manage a watchpoint like any other breakpoint: you
3380 enable, disable, and delete both breakpoints and watchpoints using the
3383 You can arrange to have values from your program displayed automatically
3384 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3388 @cindex breakpoint on events
3389 A @dfn{catchpoint} is another special breakpoint that stops your program
3390 when a certain kind of event occurs, such as the throwing of a C@t{++}
3391 exception or the loading of a library. As with watchpoints, you use a
3392 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3393 Catchpoints}), but aside from that, you can manage a catchpoint like any
3394 other breakpoint. (To stop when your program receives a signal, use the
3395 @code{handle} command; see @ref{Signals, ,Signals}.)
3397 @cindex breakpoint numbers
3398 @cindex numbers for breakpoints
3399 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3400 catchpoint when you create it; these numbers are successive integers
3401 starting with one. In many of the commands for controlling various
3402 features of breakpoints you use the breakpoint number to say which
3403 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3404 @dfn{disabled}; if disabled, it has no effect on your program until you
3407 @cindex breakpoint ranges
3408 @cindex ranges of breakpoints
3409 Some @value{GDBN} commands accept a range of breakpoints on which to
3410 operate. A breakpoint range is either a single breakpoint number, like
3411 @samp{5}, or two such numbers, in increasing order, separated by a
3412 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3413 all breakpoints in that range are operated on.
3416 * Set Breaks:: Setting breakpoints
3417 * Set Watchpoints:: Setting watchpoints
3418 * Set Catchpoints:: Setting catchpoints
3419 * Delete Breaks:: Deleting breakpoints
3420 * Disabling:: Disabling breakpoints
3421 * Conditions:: Break conditions
3422 * Break Commands:: Breakpoint command lists
3423 * Dynamic Printf:: Dynamic printf
3424 * Save Breakpoints:: How to save breakpoints in a file
3425 * Static Probe Points:: Listing static probe points
3426 * Error in Breakpoints:: ``Cannot insert breakpoints''
3427 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3431 @subsection Setting Breakpoints
3433 @c FIXME LMB what does GDB do if no code on line of breakpt?
3434 @c consider in particular declaration with/without initialization.
3436 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3439 @kindex b @r{(@code{break})}
3440 @vindex $bpnum@r{, convenience variable}
3441 @cindex latest breakpoint
3442 Breakpoints are set with the @code{break} command (abbreviated
3443 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3444 number of the breakpoint you've set most recently; see @ref{Convenience
3445 Vars,, Convenience Variables}, for a discussion of what you can do with
3446 convenience variables.
3449 @item break @var{location}
3450 Set a breakpoint at the given @var{location}, which can specify a
3451 function name, a line number, or an address of an instruction.
3452 (@xref{Specify Location}, for a list of all the possible ways to
3453 specify a @var{location}.) The breakpoint will stop your program just
3454 before it executes any of the code in the specified @var{location}.
3456 When using source languages that permit overloading of symbols, such as
3457 C@t{++}, a function name may refer to more than one possible place to break.
3458 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3461 It is also possible to insert a breakpoint that will stop the program
3462 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3463 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3466 When called without any arguments, @code{break} sets a breakpoint at
3467 the next instruction to be executed in the selected stack frame
3468 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3469 innermost, this makes your program stop as soon as control
3470 returns to that frame. This is similar to the effect of a
3471 @code{finish} command in the frame inside the selected frame---except
3472 that @code{finish} does not leave an active breakpoint. If you use
3473 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3474 the next time it reaches the current location; this may be useful
3477 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3478 least one instruction has been executed. If it did not do this, you
3479 would be unable to proceed past a breakpoint without first disabling the
3480 breakpoint. This rule applies whether or not the breakpoint already
3481 existed when your program stopped.
3483 @item break @dots{} if @var{cond}
3484 Set a breakpoint with condition @var{cond}; evaluate the expression
3485 @var{cond} each time the breakpoint is reached, and stop only if the
3486 value is nonzero---that is, if @var{cond} evaluates as true.
3487 @samp{@dots{}} stands for one of the possible arguments described
3488 above (or no argument) specifying where to break. @xref{Conditions,
3489 ,Break Conditions}, for more information on breakpoint conditions.
3492 @item tbreak @var{args}
3493 Set a breakpoint enabled only for one stop. @var{args} are the
3494 same as for the @code{break} command, and the breakpoint is set in the same
3495 way, but the breakpoint is automatically deleted after the first time your
3496 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3499 @cindex hardware breakpoints
3500 @item hbreak @var{args}
3501 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3502 @code{break} command and the breakpoint is set in the same way, but the
3503 breakpoint requires hardware support and some target hardware may not
3504 have this support. The main purpose of this is EPROM/ROM code
3505 debugging, so you can set a breakpoint at an instruction without
3506 changing the instruction. This can be used with the new trap-generation
3507 provided by SPARClite DSU and most x86-based targets. These targets
3508 will generate traps when a program accesses some data or instruction
3509 address that is assigned to the debug registers. However the hardware
3510 breakpoint registers can take a limited number of breakpoints. For
3511 example, on the DSU, only two data breakpoints can be set at a time, and
3512 @value{GDBN} will reject this command if more than two are used. Delete
3513 or disable unused hardware breakpoints before setting new ones
3514 (@pxref{Disabling, ,Disabling Breakpoints}).
3515 @xref{Conditions, ,Break Conditions}.
3516 For remote targets, you can restrict the number of hardware
3517 breakpoints @value{GDBN} will use, see @ref{set remote
3518 hardware-breakpoint-limit}.
3521 @item thbreak @var{args}
3522 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3523 are the same as for the @code{hbreak} command and the breakpoint is set in
3524 the same way. However, like the @code{tbreak} command,
3525 the breakpoint is automatically deleted after the
3526 first time your program stops there. Also, like the @code{hbreak}
3527 command, the breakpoint requires hardware support and some target hardware
3528 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3529 See also @ref{Conditions, ,Break Conditions}.
3532 @cindex regular expression
3533 @cindex breakpoints at functions matching a regexp
3534 @cindex set breakpoints in many functions
3535 @item rbreak @var{regex}
3536 Set breakpoints on all functions matching the regular expression
3537 @var{regex}. This command sets an unconditional breakpoint on all
3538 matches, printing a list of all breakpoints it set. Once these
3539 breakpoints are set, they are treated just like the breakpoints set with
3540 the @code{break} command. You can delete them, disable them, or make
3541 them conditional the same way as any other breakpoint.
3543 The syntax of the regular expression is the standard one used with tools
3544 like @file{grep}. Note that this is different from the syntax used by
3545 shells, so for instance @code{foo*} matches all functions that include
3546 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3547 @code{.*} leading and trailing the regular expression you supply, so to
3548 match only functions that begin with @code{foo}, use @code{^foo}.
3550 @cindex non-member C@t{++} functions, set breakpoint in
3551 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3552 breakpoints on overloaded functions that are not members of any special
3555 @cindex set breakpoints on all functions
3556 The @code{rbreak} command can be used to set breakpoints in
3557 @strong{all} the functions in a program, like this:
3560 (@value{GDBP}) rbreak .
3563 @item rbreak @var{file}:@var{regex}
3564 If @code{rbreak} is called with a filename qualification, it limits
3565 the search for functions matching the given regular expression to the
3566 specified @var{file}. This can be used, for example, to set breakpoints on
3567 every function in a given file:
3570 (@value{GDBP}) rbreak file.c:.
3573 The colon separating the filename qualifier from the regex may
3574 optionally be surrounded by spaces.
3576 @kindex info breakpoints
3577 @cindex @code{$_} and @code{info breakpoints}
3578 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3579 @itemx info break @r{[}@var{n}@dots{}@r{]}
3580 Print a table of all breakpoints, watchpoints, and catchpoints set and
3581 not deleted. Optional argument @var{n} means print information only
3582 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3583 For each breakpoint, following columns are printed:
3586 @item Breakpoint Numbers
3588 Breakpoint, watchpoint, or catchpoint.
3590 Whether the breakpoint is marked to be disabled or deleted when hit.
3591 @item Enabled or Disabled
3592 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3593 that are not enabled.
3595 Where the breakpoint is in your program, as a memory address. For a
3596 pending breakpoint whose address is not yet known, this field will
3597 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3598 library that has the symbol or line referred by breakpoint is loaded.
3599 See below for details. A breakpoint with several locations will
3600 have @samp{<MULTIPLE>} in this field---see below for details.
3602 Where the breakpoint is in the source for your program, as a file and
3603 line number. For a pending breakpoint, the original string passed to
3604 the breakpoint command will be listed as it cannot be resolved until
3605 the appropriate shared library is loaded in the future.
3609 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3610 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3611 @value{GDBN} on the host's side. If it is ``target'', then the condition
3612 is evaluated by the target. The @code{info break} command shows
3613 the condition on the line following the affected breakpoint, together with
3614 its condition evaluation mode in between parentheses.
3616 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3617 allowed to have a condition specified for it. The condition is not parsed for
3618 validity until a shared library is loaded that allows the pending
3619 breakpoint to resolve to a valid location.
3622 @code{info break} with a breakpoint
3623 number @var{n} as argument lists only that breakpoint. The
3624 convenience variable @code{$_} and the default examining-address for
3625 the @code{x} command are set to the address of the last breakpoint
3626 listed (@pxref{Memory, ,Examining Memory}).
3629 @code{info break} displays a count of the number of times the breakpoint
3630 has been hit. This is especially useful in conjunction with the
3631 @code{ignore} command. You can ignore a large number of breakpoint
3632 hits, look at the breakpoint info to see how many times the breakpoint
3633 was hit, and then run again, ignoring one less than that number. This
3634 will get you quickly to the last hit of that breakpoint.
3637 For a breakpoints with an enable count (xref) greater than 1,
3638 @code{info break} also displays that count.
3642 @value{GDBN} allows you to set any number of breakpoints at the same place in
3643 your program. There is nothing silly or meaningless about this. When
3644 the breakpoints are conditional, this is even useful
3645 (@pxref{Conditions, ,Break Conditions}).
3647 @cindex multiple locations, breakpoints
3648 @cindex breakpoints, multiple locations
3649 It is possible that a breakpoint corresponds to several locations
3650 in your program. Examples of this situation are:
3654 Multiple functions in the program may have the same name.
3657 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3658 instances of the function body, used in different cases.
3661 For a C@t{++} template function, a given line in the function can
3662 correspond to any number of instantiations.
3665 For an inlined function, a given source line can correspond to
3666 several places where that function is inlined.
3669 In all those cases, @value{GDBN} will insert a breakpoint at all
3670 the relevant locations.
3672 A breakpoint with multiple locations is displayed in the breakpoint
3673 table using several rows---one header row, followed by one row for
3674 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3675 address column. The rows for individual locations contain the actual
3676 addresses for locations, and show the functions to which those
3677 locations belong. The number column for a location is of the form
3678 @var{breakpoint-number}.@var{location-number}.
3683 Num Type Disp Enb Address What
3684 1 breakpoint keep y <MULTIPLE>
3686 breakpoint already hit 1 time
3687 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3688 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3691 Each location can be individually enabled or disabled by passing
3692 @var{breakpoint-number}.@var{location-number} as argument to the
3693 @code{enable} and @code{disable} commands. Note that you cannot
3694 delete the individual locations from the list, you can only delete the
3695 entire list of locations that belong to their parent breakpoint (with
3696 the @kbd{delete @var{num}} command, where @var{num} is the number of
3697 the parent breakpoint, 1 in the above example). Disabling or enabling
3698 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3699 that belong to that breakpoint.
3701 @cindex pending breakpoints
3702 It's quite common to have a breakpoint inside a shared library.
3703 Shared libraries can be loaded and unloaded explicitly,
3704 and possibly repeatedly, as the program is executed. To support
3705 this use case, @value{GDBN} updates breakpoint locations whenever
3706 any shared library is loaded or unloaded. Typically, you would
3707 set a breakpoint in a shared library at the beginning of your
3708 debugging session, when the library is not loaded, and when the
3709 symbols from the library are not available. When you try to set
3710 breakpoint, @value{GDBN} will ask you if you want to set
3711 a so called @dfn{pending breakpoint}---breakpoint whose address
3712 is not yet resolved.
3714 After the program is run, whenever a new shared library is loaded,
3715 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3716 shared library contains the symbol or line referred to by some
3717 pending breakpoint, that breakpoint is resolved and becomes an
3718 ordinary breakpoint. When a library is unloaded, all breakpoints
3719 that refer to its symbols or source lines become pending again.
3721 This logic works for breakpoints with multiple locations, too. For
3722 example, if you have a breakpoint in a C@t{++} template function, and
3723 a newly loaded shared library has an instantiation of that template,
3724 a new location is added to the list of locations for the breakpoint.
3726 Except for having unresolved address, pending breakpoints do not
3727 differ from regular breakpoints. You can set conditions or commands,
3728 enable and disable them and perform other breakpoint operations.
3730 @value{GDBN} provides some additional commands for controlling what
3731 happens when the @samp{break} command cannot resolve breakpoint
3732 address specification to an address:
3734 @kindex set breakpoint pending
3735 @kindex show breakpoint pending
3737 @item set breakpoint pending auto
3738 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3739 location, it queries you whether a pending breakpoint should be created.
3741 @item set breakpoint pending on
3742 This indicates that an unrecognized breakpoint location should automatically
3743 result in a pending breakpoint being created.
3745 @item set breakpoint pending off
3746 This indicates that pending breakpoints are not to be created. Any
3747 unrecognized breakpoint location results in an error. This setting does
3748 not affect any pending breakpoints previously created.
3750 @item show breakpoint pending
3751 Show the current behavior setting for creating pending breakpoints.
3754 The settings above only affect the @code{break} command and its
3755 variants. Once breakpoint is set, it will be automatically updated
3756 as shared libraries are loaded and unloaded.
3758 @cindex automatic hardware breakpoints
3759 For some targets, @value{GDBN} can automatically decide if hardware or
3760 software breakpoints should be used, depending on whether the
3761 breakpoint address is read-only or read-write. This applies to
3762 breakpoints set with the @code{break} command as well as to internal
3763 breakpoints set by commands like @code{next} and @code{finish}. For
3764 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3767 You can control this automatic behaviour with the following commands::
3769 @kindex set breakpoint auto-hw
3770 @kindex show breakpoint auto-hw
3772 @item set breakpoint auto-hw on
3773 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3774 will try to use the target memory map to decide if software or hardware
3775 breakpoint must be used.
3777 @item set breakpoint auto-hw off
3778 This indicates @value{GDBN} should not automatically select breakpoint
3779 type. If the target provides a memory map, @value{GDBN} will warn when
3780 trying to set software breakpoint at a read-only address.
3783 @value{GDBN} normally implements breakpoints by replacing the program code
3784 at the breakpoint address with a special instruction, which, when
3785 executed, given control to the debugger. By default, the program
3786 code is so modified only when the program is resumed. As soon as
3787 the program stops, @value{GDBN} restores the original instructions. This
3788 behaviour guards against leaving breakpoints inserted in the
3789 target should gdb abrubptly disconnect. However, with slow remote
3790 targets, inserting and removing breakpoint can reduce the performance.
3791 This behavior can be controlled with the following commands::
3793 @kindex set breakpoint always-inserted
3794 @kindex show breakpoint always-inserted
3796 @item set breakpoint always-inserted off
3797 All breakpoints, including newly added by the user, are inserted in
3798 the target only when the target is resumed. All breakpoints are
3799 removed from the target when it stops.
3801 @item set breakpoint always-inserted on
3802 Causes all breakpoints to be inserted in the target at all times. If
3803 the user adds a new breakpoint, or changes an existing breakpoint, the
3804 breakpoints in the target are updated immediately. A breakpoint is
3805 removed from the target only when breakpoint itself is removed.
3807 @cindex non-stop mode, and @code{breakpoint always-inserted}
3808 @item set breakpoint always-inserted auto
3809 This is the default mode. If @value{GDBN} is controlling the inferior
3810 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3811 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3812 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3813 @code{breakpoint always-inserted} mode is off.
3816 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3817 when a breakpoint breaks. If the condition is true, then the process being
3818 debugged stops, otherwise the process is resumed.
3820 If the target supports evaluating conditions on its end, @value{GDBN} may
3821 download the breakpoint, together with its conditions, to it.
3823 This feature can be controlled via the following commands:
3825 @kindex set breakpoint condition-evaluation
3826 @kindex show breakpoint condition-evaluation
3828 @item set breakpoint condition-evaluation host
3829 This option commands @value{GDBN} to evaluate the breakpoint
3830 conditions on the host's side. Unconditional breakpoints are sent to
3831 the target which in turn receives the triggers and reports them back to GDB
3832 for condition evaluation. This is the standard evaluation mode.
3834 @item set breakpoint condition-evaluation target
3835 This option commands @value{GDBN} to download breakpoint conditions
3836 to the target at the moment of their insertion. The target
3837 is responsible for evaluating the conditional expression and reporting
3838 breakpoint stop events back to @value{GDBN} whenever the condition
3839 is true. Due to limitations of target-side evaluation, some conditions
3840 cannot be evaluated there, e.g., conditions that depend on local data
3841 that is only known to the host. Examples include
3842 conditional expressions involving convenience variables, complex types
3843 that cannot be handled by the agent expression parser and expressions
3844 that are too long to be sent over to the target, specially when the
3845 target is a remote system. In these cases, the conditions will be
3846 evaluated by @value{GDBN}.
3848 @item set breakpoint condition-evaluation auto
3849 This is the default mode. If the target supports evaluating breakpoint
3850 conditions on its end, @value{GDBN} will download breakpoint conditions to
3851 the target (limitations mentioned previously apply). If the target does
3852 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3853 to evaluating all these conditions on the host's side.
3857 @cindex negative breakpoint numbers
3858 @cindex internal @value{GDBN} breakpoints
3859 @value{GDBN} itself sometimes sets breakpoints in your program for
3860 special purposes, such as proper handling of @code{longjmp} (in C
3861 programs). These internal breakpoints are assigned negative numbers,
3862 starting with @code{-1}; @samp{info breakpoints} does not display them.
3863 You can see these breakpoints with the @value{GDBN} maintenance command
3864 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3867 @node Set Watchpoints
3868 @subsection Setting Watchpoints
3870 @cindex setting watchpoints
3871 You can use a watchpoint to stop execution whenever the value of an
3872 expression changes, without having to predict a particular place where
3873 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3874 The expression may be as simple as the value of a single variable, or
3875 as complex as many variables combined by operators. Examples include:
3879 A reference to the value of a single variable.
3882 An address cast to an appropriate data type. For example,
3883 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3884 address (assuming an @code{int} occupies 4 bytes).
3887 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3888 expression can use any operators valid in the program's native
3889 language (@pxref{Languages}).
3892 You can set a watchpoint on an expression even if the expression can
3893 not be evaluated yet. For instance, you can set a watchpoint on
3894 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3895 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3896 the expression produces a valid value. If the expression becomes
3897 valid in some other way than changing a variable (e.g.@: if the memory
3898 pointed to by @samp{*global_ptr} becomes readable as the result of a
3899 @code{malloc} call), @value{GDBN} may not stop until the next time
3900 the expression changes.
3902 @cindex software watchpoints
3903 @cindex hardware watchpoints
3904 Depending on your system, watchpoints may be implemented in software or
3905 hardware. @value{GDBN} does software watchpointing by single-stepping your
3906 program and testing the variable's value each time, which is hundreds of
3907 times slower than normal execution. (But this may still be worth it, to
3908 catch errors where you have no clue what part of your program is the
3911 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3912 x86-based targets, @value{GDBN} includes support for hardware
3913 watchpoints, which do not slow down the running of your program.
3917 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3918 Set a watchpoint for an expression. @value{GDBN} will break when the
3919 expression @var{expr} is written into by the program and its value
3920 changes. The simplest (and the most popular) use of this command is
3921 to watch the value of a single variable:
3924 (@value{GDBP}) watch foo
3927 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3928 argument, @value{GDBN} breaks only when the thread identified by
3929 @var{threadnum} changes the value of @var{expr}. If any other threads
3930 change the value of @var{expr}, @value{GDBN} will not break. Note
3931 that watchpoints restricted to a single thread in this way only work
3932 with Hardware Watchpoints.
3934 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3935 (see below). The @code{-location} argument tells @value{GDBN} to
3936 instead watch the memory referred to by @var{expr}. In this case,
3937 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3938 and watch the memory at that address. The type of the result is used
3939 to determine the size of the watched memory. If the expression's
3940 result does not have an address, then @value{GDBN} will print an
3943 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3944 of masked watchpoints, if the current architecture supports this
3945 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3946 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3947 to an address to watch. The mask specifies that some bits of an address
3948 (the bits which are reset in the mask) should be ignored when matching
3949 the address accessed by the inferior against the watchpoint address.
3950 Thus, a masked watchpoint watches many addresses simultaneously---those
3951 addresses whose unmasked bits are identical to the unmasked bits in the
3952 watchpoint address. The @code{mask} argument implies @code{-location}.
3956 (@value{GDBP}) watch foo mask 0xffff00ff
3957 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3961 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3962 Set a watchpoint that will break when the value of @var{expr} is read
3966 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3967 Set a watchpoint that will break when @var{expr} is either read from
3968 or written into by the program.
3970 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3971 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3972 This command prints a list of watchpoints, using the same format as
3973 @code{info break} (@pxref{Set Breaks}).
3976 If you watch for a change in a numerically entered address you need to
3977 dereference it, as the address itself is just a constant number which will
3978 never change. @value{GDBN} refuses to create a watchpoint that watches
3979 a never-changing value:
3982 (@value{GDBP}) watch 0x600850
3983 Cannot watch constant value 0x600850.
3984 (@value{GDBP}) watch *(int *) 0x600850
3985 Watchpoint 1: *(int *) 6293584
3988 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3989 watchpoints execute very quickly, and the debugger reports a change in
3990 value at the exact instruction where the change occurs. If @value{GDBN}
3991 cannot set a hardware watchpoint, it sets a software watchpoint, which
3992 executes more slowly and reports the change in value at the next
3993 @emph{statement}, not the instruction, after the change occurs.
3995 @cindex use only software watchpoints
3996 You can force @value{GDBN} to use only software watchpoints with the
3997 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3998 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3999 the underlying system supports them. (Note that hardware-assisted
4000 watchpoints that were set @emph{before} setting
4001 @code{can-use-hw-watchpoints} to zero will still use the hardware
4002 mechanism of watching expression values.)
4005 @item set can-use-hw-watchpoints
4006 @kindex set can-use-hw-watchpoints
4007 Set whether or not to use hardware watchpoints.
4009 @item show can-use-hw-watchpoints
4010 @kindex show can-use-hw-watchpoints
4011 Show the current mode of using hardware watchpoints.
4014 For remote targets, you can restrict the number of hardware
4015 watchpoints @value{GDBN} will use, see @ref{set remote
4016 hardware-breakpoint-limit}.
4018 When you issue the @code{watch} command, @value{GDBN} reports
4021 Hardware watchpoint @var{num}: @var{expr}
4025 if it was able to set a hardware watchpoint.
4027 Currently, the @code{awatch} and @code{rwatch} commands can only set
4028 hardware watchpoints, because accesses to data that don't change the
4029 value of the watched expression cannot be detected without examining
4030 every instruction as it is being executed, and @value{GDBN} does not do
4031 that currently. If @value{GDBN} finds that it is unable to set a
4032 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4033 will print a message like this:
4036 Expression cannot be implemented with read/access watchpoint.
4039 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4040 data type of the watched expression is wider than what a hardware
4041 watchpoint on the target machine can handle. For example, some systems
4042 can only watch regions that are up to 4 bytes wide; on such systems you
4043 cannot set hardware watchpoints for an expression that yields a
4044 double-precision floating-point number (which is typically 8 bytes
4045 wide). As a work-around, it might be possible to break the large region
4046 into a series of smaller ones and watch them with separate watchpoints.
4048 If you set too many hardware watchpoints, @value{GDBN} might be unable
4049 to insert all of them when you resume the execution of your program.
4050 Since the precise number of active watchpoints is unknown until such
4051 time as the program is about to be resumed, @value{GDBN} might not be
4052 able to warn you about this when you set the watchpoints, and the
4053 warning will be printed only when the program is resumed:
4056 Hardware watchpoint @var{num}: Could not insert watchpoint
4060 If this happens, delete or disable some of the watchpoints.
4062 Watching complex expressions that reference many variables can also
4063 exhaust the resources available for hardware-assisted watchpoints.
4064 That's because @value{GDBN} needs to watch every variable in the
4065 expression with separately allocated resources.
4067 If you call a function interactively using @code{print} or @code{call},
4068 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4069 kind of breakpoint or the call completes.
4071 @value{GDBN} automatically deletes watchpoints that watch local
4072 (automatic) variables, or expressions that involve such variables, when
4073 they go out of scope, that is, when the execution leaves the block in
4074 which these variables were defined. In particular, when the program
4075 being debugged terminates, @emph{all} local variables go out of scope,
4076 and so only watchpoints that watch global variables remain set. If you
4077 rerun the program, you will need to set all such watchpoints again. One
4078 way of doing that would be to set a code breakpoint at the entry to the
4079 @code{main} function and when it breaks, set all the watchpoints.
4081 @cindex watchpoints and threads
4082 @cindex threads and watchpoints
4083 In multi-threaded programs, watchpoints will detect changes to the
4084 watched expression from every thread.
4087 @emph{Warning:} In multi-threaded programs, software watchpoints
4088 have only limited usefulness. If @value{GDBN} creates a software
4089 watchpoint, it can only watch the value of an expression @emph{in a
4090 single thread}. If you are confident that the expression can only
4091 change due to the current thread's activity (and if you are also
4092 confident that no other thread can become current), then you can use
4093 software watchpoints as usual. However, @value{GDBN} may not notice
4094 when a non-current thread's activity changes the expression. (Hardware
4095 watchpoints, in contrast, watch an expression in all threads.)
4098 @xref{set remote hardware-watchpoint-limit}.
4100 @node Set Catchpoints
4101 @subsection Setting Catchpoints
4102 @cindex catchpoints, setting
4103 @cindex exception handlers
4104 @cindex event handling
4106 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4107 kinds of program events, such as C@t{++} exceptions or the loading of a
4108 shared library. Use the @code{catch} command to set a catchpoint.
4112 @item catch @var{event}
4113 Stop when @var{event} occurs. @var{event} can be any of the following:
4116 @item throw @r{[}@var{regexp}@r{]}
4117 @itemx rethrow @r{[}@var{regexp}@r{]}
4118 @itemx catch @r{[}@var{regexp}@r{]}
4120 @kindex catch rethrow
4122 @cindex stop on C@t{++} exceptions
4123 The throwing, re-throwing, or catching of a C@t{++} exception.
4125 If @var{regexp} is given, then only exceptions whose type matches the
4126 regular expression will be caught.
4128 @vindex $_exception@r{, convenience variable}
4129 The convenience variable @code{$_exception} is available at an
4130 exception-related catchpoint, on some systems. This holds the
4131 exception being thrown.
4133 There are currently some limitations to C@t{++} exception handling in
4138 The support for these commands is system-dependent. Currently, only
4139 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4143 The regular expression feature and the @code{$_exception} convenience
4144 variable rely on the presence of some SDT probes in @code{libstdc++}.
4145 If these probes are not present, then these features cannot be used.
4146 These probes were first available in the GCC 4.8 release, but whether
4147 or not they are available in your GCC also depends on how it was
4151 The @code{$_exception} convenience variable is only valid at the
4152 instruction at which an exception-related catchpoint is set.
4155 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4156 location in the system library which implements runtime exception
4157 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4158 (@pxref{Selection}) to get to your code.
4161 If you call a function interactively, @value{GDBN} normally returns
4162 control to you when the function has finished executing. If the call
4163 raises an exception, however, the call may bypass the mechanism that
4164 returns control to you and cause your program either to abort or to
4165 simply continue running until it hits a breakpoint, catches a signal
4166 that @value{GDBN} is listening for, or exits. This is the case even if
4167 you set a catchpoint for the exception; catchpoints on exceptions are
4168 disabled within interactive calls. @xref{Calling}, for information on
4169 controlling this with @code{set unwind-on-terminating-exception}.
4172 You cannot raise an exception interactively.
4175 You cannot install an exception handler interactively.
4179 @kindex catch exception
4180 @cindex Ada exception catching
4181 @cindex catch Ada exceptions
4182 An Ada exception being raised. If an exception name is specified
4183 at the end of the command (eg @code{catch exception Program_Error}),
4184 the debugger will stop only when this specific exception is raised.
4185 Otherwise, the debugger stops execution when any Ada exception is raised.
4187 When inserting an exception catchpoint on a user-defined exception whose
4188 name is identical to one of the exceptions defined by the language, the
4189 fully qualified name must be used as the exception name. Otherwise,
4190 @value{GDBN} will assume that it should stop on the pre-defined exception
4191 rather than the user-defined one. For instance, assuming an exception
4192 called @code{Constraint_Error} is defined in package @code{Pck}, then
4193 the command to use to catch such exceptions is @kbd{catch exception
4194 Pck.Constraint_Error}.
4196 @item exception unhandled
4197 @kindex catch exception unhandled
4198 An exception that was raised but is not handled by the program.
4201 @kindex catch assert
4202 A failed Ada assertion.
4206 @cindex break on fork/exec
4207 A call to @code{exec}. This is currently only available for HP-UX
4211 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4212 @kindex catch syscall
4213 @cindex break on a system call.
4214 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4215 syscall is a mechanism for application programs to request a service
4216 from the operating system (OS) or one of the OS system services.
4217 @value{GDBN} can catch some or all of the syscalls issued by the
4218 debuggee, and show the related information for each syscall. If no
4219 argument is specified, calls to and returns from all system calls
4222 @var{name} can be any system call name that is valid for the
4223 underlying OS. Just what syscalls are valid depends on the OS. On
4224 GNU and Unix systems, you can find the full list of valid syscall
4225 names on @file{/usr/include/asm/unistd.h}.
4227 @c For MS-Windows, the syscall names and the corresponding numbers
4228 @c can be found, e.g., on this URL:
4229 @c http://www.metasploit.com/users/opcode/syscalls.html
4230 @c but we don't support Windows syscalls yet.
4232 Normally, @value{GDBN} knows in advance which syscalls are valid for
4233 each OS, so you can use the @value{GDBN} command-line completion
4234 facilities (@pxref{Completion,, command completion}) to list the
4237 You may also specify the system call numerically. A syscall's
4238 number is the value passed to the OS's syscall dispatcher to
4239 identify the requested service. When you specify the syscall by its
4240 name, @value{GDBN} uses its database of syscalls to convert the name
4241 into the corresponding numeric code, but using the number directly
4242 may be useful if @value{GDBN}'s database does not have the complete
4243 list of syscalls on your system (e.g., because @value{GDBN} lags
4244 behind the OS upgrades).
4246 The example below illustrates how this command works if you don't provide
4250 (@value{GDBP}) catch syscall
4251 Catchpoint 1 (syscall)
4253 Starting program: /tmp/catch-syscall
4255 Catchpoint 1 (call to syscall 'close'), \
4256 0xffffe424 in __kernel_vsyscall ()
4260 Catchpoint 1 (returned from syscall 'close'), \
4261 0xffffe424 in __kernel_vsyscall ()
4265 Here is an example of catching a system call by name:
4268 (@value{GDBP}) catch syscall chroot
4269 Catchpoint 1 (syscall 'chroot' [61])
4271 Starting program: /tmp/catch-syscall
4273 Catchpoint 1 (call to syscall 'chroot'), \
4274 0xffffe424 in __kernel_vsyscall ()
4278 Catchpoint 1 (returned from syscall 'chroot'), \
4279 0xffffe424 in __kernel_vsyscall ()
4283 An example of specifying a system call numerically. In the case
4284 below, the syscall number has a corresponding entry in the XML
4285 file, so @value{GDBN} finds its name and prints it:
4288 (@value{GDBP}) catch syscall 252
4289 Catchpoint 1 (syscall(s) 'exit_group')
4291 Starting program: /tmp/catch-syscall
4293 Catchpoint 1 (call to syscall 'exit_group'), \
4294 0xffffe424 in __kernel_vsyscall ()
4298 Program exited normally.
4302 However, there can be situations when there is no corresponding name
4303 in XML file for that syscall number. In this case, @value{GDBN} prints
4304 a warning message saying that it was not able to find the syscall name,
4305 but the catchpoint will be set anyway. See the example below:
4308 (@value{GDBP}) catch syscall 764
4309 warning: The number '764' does not represent a known syscall.
4310 Catchpoint 2 (syscall 764)
4314 If you configure @value{GDBN} using the @samp{--without-expat} option,
4315 it will not be able to display syscall names. Also, if your
4316 architecture does not have an XML file describing its system calls,
4317 you will not be able to see the syscall names. It is important to
4318 notice that these two features are used for accessing the syscall
4319 name database. In either case, you will see a warning like this:
4322 (@value{GDBP}) catch syscall
4323 warning: Could not open "syscalls/i386-linux.xml"
4324 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4325 GDB will not be able to display syscall names.
4326 Catchpoint 1 (syscall)
4330 Of course, the file name will change depending on your architecture and system.
4332 Still using the example above, you can also try to catch a syscall by its
4333 number. In this case, you would see something like:
4336 (@value{GDBP}) catch syscall 252
4337 Catchpoint 1 (syscall(s) 252)
4340 Again, in this case @value{GDBN} would not be able to display syscall's names.
4344 A call to @code{fork}. This is currently only available for HP-UX
4349 A call to @code{vfork}. This is currently only available for HP-UX
4352 @item load @r{[}regexp@r{]}
4353 @itemx unload @r{[}regexp@r{]}
4355 @kindex catch unload
4356 The loading or unloading of a shared library. If @var{regexp} is
4357 given, then the catchpoint will stop only if the regular expression
4358 matches one of the affected libraries.
4360 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4361 @kindex catch signal
4362 The delivery of a signal.
4364 With no arguments, this catchpoint will catch any signal that is not
4365 used internally by @value{GDBN}, specifically, all signals except
4366 @samp{SIGTRAP} and @samp{SIGINT}.
4368 With the argument @samp{all}, all signals, including those used by
4369 @value{GDBN}, will be caught. This argument cannot be used with other
4372 Otherwise, the arguments are a list of signal names as given to
4373 @code{handle} (@pxref{Signals}). Only signals specified in this list
4376 One reason that @code{catch signal} can be more useful than
4377 @code{handle} is that you can attach commands and conditions to the
4380 When a signal is caught by a catchpoint, the signal's @code{stop} and
4381 @code{print} settings, as specified by @code{handle}, are ignored.
4382 However, whether the signal is still delivered to the inferior depends
4383 on the @code{pass} setting; this can be changed in the catchpoint's
4388 @item tcatch @var{event}
4390 Set a catchpoint that is enabled only for one stop. The catchpoint is
4391 automatically deleted after the first time the event is caught.
4395 Use the @code{info break} command to list the current catchpoints.
4399 @subsection Deleting Breakpoints
4401 @cindex clearing breakpoints, watchpoints, catchpoints
4402 @cindex deleting breakpoints, watchpoints, catchpoints
4403 It is often necessary to eliminate a breakpoint, watchpoint, or
4404 catchpoint once it has done its job and you no longer want your program
4405 to stop there. This is called @dfn{deleting} the breakpoint. A
4406 breakpoint that has been deleted no longer exists; it is forgotten.
4408 With the @code{clear} command you can delete breakpoints according to
4409 where they are in your program. With the @code{delete} command you can
4410 delete individual breakpoints, watchpoints, or catchpoints by specifying
4411 their breakpoint numbers.
4413 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4414 automatically ignores breakpoints on the first instruction to be executed
4415 when you continue execution without changing the execution address.
4420 Delete any breakpoints at the next instruction to be executed in the
4421 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4422 the innermost frame is selected, this is a good way to delete a
4423 breakpoint where your program just stopped.
4425 @item clear @var{location}
4426 Delete any breakpoints set at the specified @var{location}.
4427 @xref{Specify Location}, for the various forms of @var{location}; the
4428 most useful ones are listed below:
4431 @item clear @var{function}
4432 @itemx clear @var{filename}:@var{function}
4433 Delete any breakpoints set at entry to the named @var{function}.
4435 @item clear @var{linenum}
4436 @itemx clear @var{filename}:@var{linenum}
4437 Delete any breakpoints set at or within the code of the specified
4438 @var{linenum} of the specified @var{filename}.
4441 @cindex delete breakpoints
4443 @kindex d @r{(@code{delete})}
4444 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4445 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4446 ranges specified as arguments. If no argument is specified, delete all
4447 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4448 confirm off}). You can abbreviate this command as @code{d}.
4452 @subsection Disabling Breakpoints
4454 @cindex enable/disable a breakpoint
4455 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4456 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4457 it had been deleted, but remembers the information on the breakpoint so
4458 that you can @dfn{enable} it again later.
4460 You disable and enable breakpoints, watchpoints, and catchpoints with
4461 the @code{enable} and @code{disable} commands, optionally specifying
4462 one or more breakpoint numbers as arguments. Use @code{info break} to
4463 print a list of all breakpoints, watchpoints, and catchpoints if you
4464 do not know which numbers to use.
4466 Disabling and enabling a breakpoint that has multiple locations
4467 affects all of its locations.
4469 A breakpoint, watchpoint, or catchpoint can have any of several
4470 different states of enablement:
4474 Enabled. The breakpoint stops your program. A breakpoint set
4475 with the @code{break} command starts out in this state.
4477 Disabled. The breakpoint has no effect on your program.
4479 Enabled once. The breakpoint stops your program, but then becomes
4482 Enabled for a count. The breakpoint stops your program for the next
4483 N times, then becomes disabled.
4485 Enabled for deletion. The breakpoint stops your program, but
4486 immediately after it does so it is deleted permanently. A breakpoint
4487 set with the @code{tbreak} command starts out in this state.
4490 You can use the following commands to enable or disable breakpoints,
4491 watchpoints, and catchpoints:
4495 @kindex dis @r{(@code{disable})}
4496 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4497 Disable the specified breakpoints---or all breakpoints, if none are
4498 listed. A disabled breakpoint has no effect but is not forgotten. All
4499 options such as ignore-counts, conditions and commands are remembered in
4500 case the breakpoint is enabled again later. You may abbreviate
4501 @code{disable} as @code{dis}.
4504 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4505 Enable the specified breakpoints (or all defined breakpoints). They
4506 become effective once again in stopping your program.
4508 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4509 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4510 of these breakpoints immediately after stopping your program.
4512 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4513 Enable the specified breakpoints temporarily. @value{GDBN} records
4514 @var{count} with each of the specified breakpoints, and decrements a
4515 breakpoint's count when it is hit. When any count reaches 0,
4516 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4517 count (@pxref{Conditions, ,Break Conditions}), that will be
4518 decremented to 0 before @var{count} is affected.
4520 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4521 Enable the specified breakpoints to work once, then die. @value{GDBN}
4522 deletes any of these breakpoints as soon as your program stops there.
4523 Breakpoints set by the @code{tbreak} command start out in this state.
4526 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4527 @c confusing: tbreak is also initially enabled.
4528 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4529 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4530 subsequently, they become disabled or enabled only when you use one of
4531 the commands above. (The command @code{until} can set and delete a
4532 breakpoint of its own, but it does not change the state of your other
4533 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4537 @subsection Break Conditions
4538 @cindex conditional breakpoints
4539 @cindex breakpoint conditions
4541 @c FIXME what is scope of break condition expr? Context where wanted?
4542 @c in particular for a watchpoint?
4543 The simplest sort of breakpoint breaks every time your program reaches a
4544 specified place. You can also specify a @dfn{condition} for a
4545 breakpoint. A condition is just a Boolean expression in your
4546 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4547 a condition evaluates the expression each time your program reaches it,
4548 and your program stops only if the condition is @emph{true}.
4550 This is the converse of using assertions for program validation; in that
4551 situation, you want to stop when the assertion is violated---that is,
4552 when the condition is false. In C, if you want to test an assertion expressed
4553 by the condition @var{assert}, you should set the condition
4554 @samp{! @var{assert}} on the appropriate breakpoint.
4556 Conditions are also accepted for watchpoints; you may not need them,
4557 since a watchpoint is inspecting the value of an expression anyhow---but
4558 it might be simpler, say, to just set a watchpoint on a variable name,
4559 and specify a condition that tests whether the new value is an interesting
4562 Break conditions can have side effects, and may even call functions in
4563 your program. This can be useful, for example, to activate functions
4564 that log program progress, or to use your own print functions to
4565 format special data structures. The effects are completely predictable
4566 unless there is another enabled breakpoint at the same address. (In
4567 that case, @value{GDBN} might see the other breakpoint first and stop your
4568 program without checking the condition of this one.) Note that
4569 breakpoint commands are usually more convenient and flexible than break
4571 purpose of performing side effects when a breakpoint is reached
4572 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4574 Breakpoint conditions can also be evaluated on the target's side if
4575 the target supports it. Instead of evaluating the conditions locally,
4576 @value{GDBN} encodes the expression into an agent expression
4577 (@pxref{Agent Expressions}) suitable for execution on the target,
4578 independently of @value{GDBN}. Global variables become raw memory
4579 locations, locals become stack accesses, and so forth.
4581 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4582 when its condition evaluates to true. This mechanism may provide faster
4583 response times depending on the performance characteristics of the target
4584 since it does not need to keep @value{GDBN} informed about
4585 every breakpoint trigger, even those with false conditions.
4587 Break conditions can be specified when a breakpoint is set, by using
4588 @samp{if} in the arguments to the @code{break} command. @xref{Set
4589 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4590 with the @code{condition} command.
4592 You can also use the @code{if} keyword with the @code{watch} command.
4593 The @code{catch} command does not recognize the @code{if} keyword;
4594 @code{condition} is the only way to impose a further condition on a
4599 @item condition @var{bnum} @var{expression}
4600 Specify @var{expression} as the break condition for breakpoint,
4601 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4602 breakpoint @var{bnum} stops your program only if the value of
4603 @var{expression} is true (nonzero, in C). When you use
4604 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4605 syntactic correctness, and to determine whether symbols in it have
4606 referents in the context of your breakpoint. If @var{expression} uses
4607 symbols not referenced in the context of the breakpoint, @value{GDBN}
4608 prints an error message:
4611 No symbol "foo" in current context.
4616 not actually evaluate @var{expression} at the time the @code{condition}
4617 command (or a command that sets a breakpoint with a condition, like
4618 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4620 @item condition @var{bnum}
4621 Remove the condition from breakpoint number @var{bnum}. It becomes
4622 an ordinary unconditional breakpoint.
4625 @cindex ignore count (of breakpoint)
4626 A special case of a breakpoint condition is to stop only when the
4627 breakpoint has been reached a certain number of times. This is so
4628 useful that there is a special way to do it, using the @dfn{ignore
4629 count} of the breakpoint. Every breakpoint has an ignore count, which
4630 is an integer. Most of the time, the ignore count is zero, and
4631 therefore has no effect. But if your program reaches a breakpoint whose
4632 ignore count is positive, then instead of stopping, it just decrements
4633 the ignore count by one and continues. As a result, if the ignore count
4634 value is @var{n}, the breakpoint does not stop the next @var{n} times
4635 your program reaches it.
4639 @item ignore @var{bnum} @var{count}
4640 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4641 The next @var{count} times the breakpoint is reached, your program's
4642 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4645 To make the breakpoint stop the next time it is reached, specify
4648 When you use @code{continue} to resume execution of your program from a
4649 breakpoint, you can specify an ignore count directly as an argument to
4650 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4651 Stepping,,Continuing and Stepping}.
4653 If a breakpoint has a positive ignore count and a condition, the
4654 condition is not checked. Once the ignore count reaches zero,
4655 @value{GDBN} resumes checking the condition.
4657 You could achieve the effect of the ignore count with a condition such
4658 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4659 is decremented each time. @xref{Convenience Vars, ,Convenience
4663 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4666 @node Break Commands
4667 @subsection Breakpoint Command Lists
4669 @cindex breakpoint commands
4670 You can give any breakpoint (or watchpoint or catchpoint) a series of
4671 commands to execute when your program stops due to that breakpoint. For
4672 example, you might want to print the values of certain expressions, or
4673 enable other breakpoints.
4677 @kindex end@r{ (breakpoint commands)}
4678 @item commands @r{[}@var{range}@dots{}@r{]}
4679 @itemx @dots{} @var{command-list} @dots{}
4681 Specify a list of commands for the given breakpoints. The commands
4682 themselves appear on the following lines. Type a line containing just
4683 @code{end} to terminate the commands.
4685 To remove all commands from a breakpoint, type @code{commands} and
4686 follow it immediately with @code{end}; that is, give no commands.
4688 With no argument, @code{commands} refers to the last breakpoint,
4689 watchpoint, or catchpoint set (not to the breakpoint most recently
4690 encountered). If the most recent breakpoints were set with a single
4691 command, then the @code{commands} will apply to all the breakpoints
4692 set by that command. This applies to breakpoints set by
4693 @code{rbreak}, and also applies when a single @code{break} command
4694 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4698 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4699 disabled within a @var{command-list}.
4701 You can use breakpoint commands to start your program up again. Simply
4702 use the @code{continue} command, or @code{step}, or any other command
4703 that resumes execution.
4705 Any other commands in the command list, after a command that resumes
4706 execution, are ignored. This is because any time you resume execution
4707 (even with a simple @code{next} or @code{step}), you may encounter
4708 another breakpoint---which could have its own command list, leading to
4709 ambiguities about which list to execute.
4712 If the first command you specify in a command list is @code{silent}, the
4713 usual message about stopping at a breakpoint is not printed. This may
4714 be desirable for breakpoints that are to print a specific message and
4715 then continue. If none of the remaining commands print anything, you
4716 see no sign that the breakpoint was reached. @code{silent} is
4717 meaningful only at the beginning of a breakpoint command list.
4719 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4720 print precisely controlled output, and are often useful in silent
4721 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4723 For example, here is how you could use breakpoint commands to print the
4724 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4730 printf "x is %d\n",x
4735 One application for breakpoint commands is to compensate for one bug so
4736 you can test for another. Put a breakpoint just after the erroneous line
4737 of code, give it a condition to detect the case in which something
4738 erroneous has been done, and give it commands to assign correct values
4739 to any variables that need them. End with the @code{continue} command
4740 so that your program does not stop, and start with the @code{silent}
4741 command so that no output is produced. Here is an example:
4752 @node Dynamic Printf
4753 @subsection Dynamic Printf
4755 @cindex dynamic printf
4757 The dynamic printf command @code{dprintf} combines a breakpoint with
4758 formatted printing of your program's data to give you the effect of
4759 inserting @code{printf} calls into your program on-the-fly, without
4760 having to recompile it.
4762 In its most basic form, the output goes to the GDB console. However,
4763 you can set the variable @code{dprintf-style} for alternate handling.
4764 For instance, you can ask to format the output by calling your
4765 program's @code{printf} function. This has the advantage that the
4766 characters go to the program's output device, so they can recorded in
4767 redirects to files and so forth.
4769 If you are doing remote debugging with a stub or agent, you can also
4770 ask to have the printf handled by the remote agent. In addition to
4771 ensuring that the output goes to the remote program's device along
4772 with any other output the program might produce, you can also ask that
4773 the dprintf remain active even after disconnecting from the remote
4774 target. Using the stub/agent is also more efficient, as it can do
4775 everything without needing to communicate with @value{GDBN}.
4779 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4780 Whenever execution reaches @var{location}, print the values of one or
4781 more @var{expressions} under the control of the string @var{template}.
4782 To print several values, separate them with commas.
4784 @item set dprintf-style @var{style}
4785 Set the dprintf output to be handled in one of several different
4786 styles enumerated below. A change of style affects all existing
4787 dynamic printfs immediately. (If you need individual control over the
4788 print commands, simply define normal breakpoints with
4789 explicitly-supplied command lists.)
4792 @kindex dprintf-style gdb
4793 Handle the output using the @value{GDBN} @code{printf} command.
4796 @kindex dprintf-style call
4797 Handle the output by calling a function in your program (normally
4801 @kindex dprintf-style agent
4802 Have the remote debugging agent (such as @code{gdbserver}) handle
4803 the output itself. This style is only available for agents that
4804 support running commands on the target.
4806 @item set dprintf-function @var{function}
4807 Set the function to call if the dprintf style is @code{call}. By
4808 default its value is @code{printf}. You may set it to any expression.
4809 that @value{GDBN} can evaluate to a function, as per the @code{call}
4812 @item set dprintf-channel @var{channel}
4813 Set a ``channel'' for dprintf. If set to a non-empty value,
4814 @value{GDBN} will evaluate it as an expression and pass the result as
4815 a first argument to the @code{dprintf-function}, in the manner of
4816 @code{fprintf} and similar functions. Otherwise, the dprintf format
4817 string will be the first argument, in the manner of @code{printf}.
4819 As an example, if you wanted @code{dprintf} output to go to a logfile
4820 that is a standard I/O stream assigned to the variable @code{mylog},
4821 you could do the following:
4824 (gdb) set dprintf-style call
4825 (gdb) set dprintf-function fprintf
4826 (gdb) set dprintf-channel mylog
4827 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4828 Dprintf 1 at 0x123456: file main.c, line 25.
4830 1 dprintf keep y 0x00123456 in main at main.c:25
4831 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4836 Note that the @code{info break} displays the dynamic printf commands
4837 as normal breakpoint commands; you can thus easily see the effect of
4838 the variable settings.
4840 @item set disconnected-dprintf on
4841 @itemx set disconnected-dprintf off
4842 @kindex set disconnected-dprintf
4843 Choose whether @code{dprintf} commands should continue to run if
4844 @value{GDBN} has disconnected from the target. This only applies
4845 if the @code{dprintf-style} is @code{agent}.
4847 @item show disconnected-dprintf off
4848 @kindex show disconnected-dprintf
4849 Show the current choice for disconnected @code{dprintf}.
4853 @value{GDBN} does not check the validity of function and channel,
4854 relying on you to supply values that are meaningful for the contexts
4855 in which they are being used. For instance, the function and channel
4856 may be the values of local variables, but if that is the case, then
4857 all enabled dynamic prints must be at locations within the scope of
4858 those locals. If evaluation fails, @value{GDBN} will report an error.
4860 @node Save Breakpoints
4861 @subsection How to save breakpoints to a file
4863 To save breakpoint definitions to a file use the @w{@code{save
4864 breakpoints}} command.
4867 @kindex save breakpoints
4868 @cindex save breakpoints to a file for future sessions
4869 @item save breakpoints [@var{filename}]
4870 This command saves all current breakpoint definitions together with
4871 their commands and ignore counts, into a file @file{@var{filename}}
4872 suitable for use in a later debugging session. This includes all
4873 types of breakpoints (breakpoints, watchpoints, catchpoints,
4874 tracepoints). To read the saved breakpoint definitions, use the
4875 @code{source} command (@pxref{Command Files}). Note that watchpoints
4876 with expressions involving local variables may fail to be recreated
4877 because it may not be possible to access the context where the
4878 watchpoint is valid anymore. Because the saved breakpoint definitions
4879 are simply a sequence of @value{GDBN} commands that recreate the
4880 breakpoints, you can edit the file in your favorite editing program,
4881 and remove the breakpoint definitions you're not interested in, or
4882 that can no longer be recreated.
4885 @node Static Probe Points
4886 @subsection Static Probe Points
4888 @cindex static probe point, SystemTap
4889 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4890 for Statically Defined Tracing, and the probes are designed to have a tiny
4891 runtime code and data footprint, and no dynamic relocations. They are
4892 usable from assembly, C and C@t{++} languages. See
4893 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4894 for a good reference on how the @acronym{SDT} probes are implemented.
4896 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4897 @acronym{SDT} probes are supported on ELF-compatible systems. See
4898 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4899 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4900 in your applications.
4902 @cindex semaphores on static probe points
4903 Some probes have an associated semaphore variable; for instance, this
4904 happens automatically if you defined your probe using a DTrace-style
4905 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4906 automatically enable it when you specify a breakpoint using the
4907 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4908 location by some other method (e.g., @code{break file:line}), then
4909 @value{GDBN} will not automatically set the semaphore.
4911 You can examine the available static static probes using @code{info
4912 probes}, with optional arguments:
4916 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4917 If given, @var{provider} is a regular expression used to match against provider
4918 names when selecting which probes to list. If omitted, probes by all
4919 probes from all providers are listed.
4921 If given, @var{name} is a regular expression to match against probe names
4922 when selecting which probes to list. If omitted, probe names are not
4923 considered when deciding whether to display them.
4925 If given, @var{objfile} is a regular expression used to select which
4926 object files (executable or shared libraries) to examine. If not
4927 given, all object files are considered.
4929 @item info probes all
4930 List the available static probes, from all types.
4933 @vindex $_probe_arg@r{, convenience variable}
4934 A probe may specify up to twelve arguments. These are available at the
4935 point at which the probe is defined---that is, when the current PC is
4936 at the probe's location. The arguments are available using the
4937 convenience variables (@pxref{Convenience Vars})
4938 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4939 an integer of the appropriate size; types are not preserved. The
4940 convenience variable @code{$_probe_argc} holds the number of arguments
4941 at the current probe point.
4943 These variables are always available, but attempts to access them at
4944 any location other than a probe point will cause @value{GDBN} to give
4948 @c @ifclear BARETARGET
4949 @node Error in Breakpoints
4950 @subsection ``Cannot insert breakpoints''
4952 If you request too many active hardware-assisted breakpoints and
4953 watchpoints, you will see this error message:
4955 @c FIXME: the precise wording of this message may change; the relevant
4956 @c source change is not committed yet (Sep 3, 1999).
4958 Stopped; cannot insert breakpoints.
4959 You may have requested too many hardware breakpoints and watchpoints.
4963 This message is printed when you attempt to resume the program, since
4964 only then @value{GDBN} knows exactly how many hardware breakpoints and
4965 watchpoints it needs to insert.
4967 When this message is printed, you need to disable or remove some of the
4968 hardware-assisted breakpoints and watchpoints, and then continue.
4970 @node Breakpoint-related Warnings
4971 @subsection ``Breakpoint address adjusted...''
4972 @cindex breakpoint address adjusted
4974 Some processor architectures place constraints on the addresses at
4975 which breakpoints may be placed. For architectures thus constrained,
4976 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4977 with the constraints dictated by the architecture.
4979 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4980 a VLIW architecture in which a number of RISC-like instructions may be
4981 bundled together for parallel execution. The FR-V architecture
4982 constrains the location of a breakpoint instruction within such a
4983 bundle to the instruction with the lowest address. @value{GDBN}
4984 honors this constraint by adjusting a breakpoint's address to the
4985 first in the bundle.
4987 It is not uncommon for optimized code to have bundles which contain
4988 instructions from different source statements, thus it may happen that
4989 a breakpoint's address will be adjusted from one source statement to
4990 another. Since this adjustment may significantly alter @value{GDBN}'s
4991 breakpoint related behavior from what the user expects, a warning is
4992 printed when the breakpoint is first set and also when the breakpoint
4995 A warning like the one below is printed when setting a breakpoint
4996 that's been subject to address adjustment:
4999 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5002 Such warnings are printed both for user settable and @value{GDBN}'s
5003 internal breakpoints. If you see one of these warnings, you should
5004 verify that a breakpoint set at the adjusted address will have the
5005 desired affect. If not, the breakpoint in question may be removed and
5006 other breakpoints may be set which will have the desired behavior.
5007 E.g., it may be sufficient to place the breakpoint at a later
5008 instruction. A conditional breakpoint may also be useful in some
5009 cases to prevent the breakpoint from triggering too often.
5011 @value{GDBN} will also issue a warning when stopping at one of these
5012 adjusted breakpoints:
5015 warning: Breakpoint 1 address previously adjusted from 0x00010414
5019 When this warning is encountered, it may be too late to take remedial
5020 action except in cases where the breakpoint is hit earlier or more
5021 frequently than expected.
5023 @node Continuing and Stepping
5024 @section Continuing and Stepping
5028 @cindex resuming execution
5029 @dfn{Continuing} means resuming program execution until your program
5030 completes normally. In contrast, @dfn{stepping} means executing just
5031 one more ``step'' of your program, where ``step'' may mean either one
5032 line of source code, or one machine instruction (depending on what
5033 particular command you use). Either when continuing or when stepping,
5034 your program may stop even sooner, due to a breakpoint or a signal. (If
5035 it stops due to a signal, you may want to use @code{handle}, or use
5036 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
5040 @kindex c @r{(@code{continue})}
5041 @kindex fg @r{(resume foreground execution)}
5042 @item continue @r{[}@var{ignore-count}@r{]}
5043 @itemx c @r{[}@var{ignore-count}@r{]}
5044 @itemx fg @r{[}@var{ignore-count}@r{]}
5045 Resume program execution, at the address where your program last stopped;
5046 any breakpoints set at that address are bypassed. The optional argument
5047 @var{ignore-count} allows you to specify a further number of times to
5048 ignore a breakpoint at this location; its effect is like that of
5049 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5051 The argument @var{ignore-count} is meaningful only when your program
5052 stopped due to a breakpoint. At other times, the argument to
5053 @code{continue} is ignored.
5055 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5056 debugged program is deemed to be the foreground program) are provided
5057 purely for convenience, and have exactly the same behavior as
5061 To resume execution at a different place, you can use @code{return}
5062 (@pxref{Returning, ,Returning from a Function}) to go back to the
5063 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5064 Different Address}) to go to an arbitrary location in your program.
5066 A typical technique for using stepping is to set a breakpoint
5067 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5068 beginning of the function or the section of your program where a problem
5069 is believed to lie, run your program until it stops at that breakpoint,
5070 and then step through the suspect area, examining the variables that are
5071 interesting, until you see the problem happen.
5075 @kindex s @r{(@code{step})}
5077 Continue running your program until control reaches a different source
5078 line, then stop it and return control to @value{GDBN}. This command is
5079 abbreviated @code{s}.
5082 @c "without debugging information" is imprecise; actually "without line
5083 @c numbers in the debugging information". (gcc -g1 has debugging info but
5084 @c not line numbers). But it seems complex to try to make that
5085 @c distinction here.
5086 @emph{Warning:} If you use the @code{step} command while control is
5087 within a function that was compiled without debugging information,
5088 execution proceeds until control reaches a function that does have
5089 debugging information. Likewise, it will not step into a function which
5090 is compiled without debugging information. To step through functions
5091 without debugging information, use the @code{stepi} command, described
5095 The @code{step} command only stops at the first instruction of a source
5096 line. This prevents the multiple stops that could otherwise occur in
5097 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5098 to stop if a function that has debugging information is called within
5099 the line. In other words, @code{step} @emph{steps inside} any functions
5100 called within the line.
5102 Also, the @code{step} command only enters a function if there is line
5103 number information for the function. Otherwise it acts like the
5104 @code{next} command. This avoids problems when using @code{cc -gl}
5105 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5106 was any debugging information about the routine.
5108 @item step @var{count}
5109 Continue running as in @code{step}, but do so @var{count} times. If a
5110 breakpoint is reached, or a signal not related to stepping occurs before
5111 @var{count} steps, stepping stops right away.
5114 @kindex n @r{(@code{next})}
5115 @item next @r{[}@var{count}@r{]}
5116 Continue to the next source line in the current (innermost) stack frame.
5117 This is similar to @code{step}, but function calls that appear within
5118 the line of code are executed without stopping. Execution stops when
5119 control reaches a different line of code at the original stack level
5120 that was executing when you gave the @code{next} command. This command
5121 is abbreviated @code{n}.
5123 An argument @var{count} is a repeat count, as for @code{step}.
5126 @c FIX ME!! Do we delete this, or is there a way it fits in with
5127 @c the following paragraph? --- Vctoria
5129 @c @code{next} within a function that lacks debugging information acts like
5130 @c @code{step}, but any function calls appearing within the code of the
5131 @c function are executed without stopping.
5133 The @code{next} command only stops at the first instruction of a
5134 source line. This prevents multiple stops that could otherwise occur in
5135 @code{switch} statements, @code{for} loops, etc.
5137 @kindex set step-mode
5139 @cindex functions without line info, and stepping
5140 @cindex stepping into functions with no line info
5141 @itemx set step-mode on
5142 The @code{set step-mode on} command causes the @code{step} command to
5143 stop at the first instruction of a function which contains no debug line
5144 information rather than stepping over it.
5146 This is useful in cases where you may be interested in inspecting the
5147 machine instructions of a function which has no symbolic info and do not
5148 want @value{GDBN} to automatically skip over this function.
5150 @item set step-mode off
5151 Causes the @code{step} command to step over any functions which contains no
5152 debug information. This is the default.
5154 @item show step-mode
5155 Show whether @value{GDBN} will stop in or step over functions without
5156 source line debug information.
5159 @kindex fin @r{(@code{finish})}
5161 Continue running until just after function in the selected stack frame
5162 returns. Print the returned value (if any). This command can be
5163 abbreviated as @code{fin}.
5165 Contrast this with the @code{return} command (@pxref{Returning,
5166 ,Returning from a Function}).
5169 @kindex u @r{(@code{until})}
5170 @cindex run until specified location
5173 Continue running until a source line past the current line, in the
5174 current stack frame, is reached. This command is used to avoid single
5175 stepping through a loop more than once. It is like the @code{next}
5176 command, except that when @code{until} encounters a jump, it
5177 automatically continues execution until the program counter is greater
5178 than the address of the jump.
5180 This means that when you reach the end of a loop after single stepping
5181 though it, @code{until} makes your program continue execution until it
5182 exits the loop. In contrast, a @code{next} command at the end of a loop
5183 simply steps back to the beginning of the loop, which forces you to step
5184 through the next iteration.
5186 @code{until} always stops your program if it attempts to exit the current
5189 @code{until} may produce somewhat counterintuitive results if the order
5190 of machine code does not match the order of the source lines. For
5191 example, in the following excerpt from a debugging session, the @code{f}
5192 (@code{frame}) command shows that execution is stopped at line
5193 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5197 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5199 (@value{GDBP}) until
5200 195 for ( ; argc > 0; NEXTARG) @{
5203 This happened because, for execution efficiency, the compiler had
5204 generated code for the loop closure test at the end, rather than the
5205 start, of the loop---even though the test in a C @code{for}-loop is
5206 written before the body of the loop. The @code{until} command appeared
5207 to step back to the beginning of the loop when it advanced to this
5208 expression; however, it has not really gone to an earlier
5209 statement---not in terms of the actual machine code.
5211 @code{until} with no argument works by means of single
5212 instruction stepping, and hence is slower than @code{until} with an
5215 @item until @var{location}
5216 @itemx u @var{location}
5217 Continue running your program until either the specified location is
5218 reached, or the current stack frame returns. @var{location} is any of
5219 the forms described in @ref{Specify Location}.
5220 This form of the command uses temporary breakpoints, and
5221 hence is quicker than @code{until} without an argument. The specified
5222 location is actually reached only if it is in the current frame. This
5223 implies that @code{until} can be used to skip over recursive function
5224 invocations. For instance in the code below, if the current location is
5225 line @code{96}, issuing @code{until 99} will execute the program up to
5226 line @code{99} in the same invocation of factorial, i.e., after the inner
5227 invocations have returned.
5230 94 int factorial (int value)
5232 96 if (value > 1) @{
5233 97 value *= factorial (value - 1);
5240 @kindex advance @var{location}
5241 @item advance @var{location}
5242 Continue running the program up to the given @var{location}. An argument is
5243 required, which should be of one of the forms described in
5244 @ref{Specify Location}.
5245 Execution will also stop upon exit from the current stack
5246 frame. This command is similar to @code{until}, but @code{advance} will
5247 not skip over recursive function calls, and the target location doesn't
5248 have to be in the same frame as the current one.
5252 @kindex si @r{(@code{stepi})}
5254 @itemx stepi @var{arg}
5256 Execute one machine instruction, then stop and return to the debugger.
5258 It is often useful to do @samp{display/i $pc} when stepping by machine
5259 instructions. This makes @value{GDBN} automatically display the next
5260 instruction to be executed, each time your program stops. @xref{Auto
5261 Display,, Automatic Display}.
5263 An argument is a repeat count, as in @code{step}.
5267 @kindex ni @r{(@code{nexti})}
5269 @itemx nexti @var{arg}
5271 Execute one machine instruction, but if it is a function call,
5272 proceed until the function returns.
5274 An argument is a repeat count, as in @code{next}.
5278 @anchor{range stepping}
5279 @cindex range stepping
5280 @cindex target-assisted range stepping
5281 By default, and if available, @value{GDBN} makes use of
5282 target-assisted @dfn{range stepping}. In other words, whenever you
5283 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5284 tells the target to step the corresponding range of instruction
5285 addresses instead of issuing multiple single-steps. This speeds up
5286 line stepping, particularly for remote targets. Ideally, there should
5287 be no reason you would want to turn range stepping off. However, it's
5288 possible that a bug in the debug info, a bug in the remote stub (for
5289 remote targets), or even a bug in @value{GDBN} could make line
5290 stepping behave incorrectly when target-assisted range stepping is
5291 enabled. You can use the following command to turn off range stepping
5295 @kindex set range-stepping
5296 @kindex show range-stepping
5297 @item set range-stepping
5298 @itemx show range-stepping
5299 Control whether range stepping is enabled.
5301 If @code{on}, and the target supports it, @value{GDBN} tells the
5302 target to step a range of addresses itself, instead of issuing
5303 multiple single-steps. If @code{off}, @value{GDBN} always issues
5304 single-steps, even if range stepping is supported by the target. The
5305 default is @code{on}.
5309 @node Skipping Over Functions and Files
5310 @section Skipping Over Functions and Files
5311 @cindex skipping over functions and files
5313 The program you are debugging may contain some functions which are
5314 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5315 skip a function or all functions in a file when stepping.
5317 For example, consider the following C function:
5328 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5329 are not interested in stepping through @code{boring}. If you run @code{step}
5330 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5331 step over both @code{foo} and @code{boring}!
5333 One solution is to @code{step} into @code{boring} and use the @code{finish}
5334 command to immediately exit it. But this can become tedious if @code{boring}
5335 is called from many places.
5337 A more flexible solution is to execute @kbd{skip boring}. This instructs
5338 @value{GDBN} never to step into @code{boring}. Now when you execute
5339 @code{step} at line 103, you'll step over @code{boring} and directly into
5342 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5343 example, @code{skip file boring.c}.
5346 @kindex skip function
5347 @item skip @r{[}@var{linespec}@r{]}
5348 @itemx skip function @r{[}@var{linespec}@r{]}
5349 After running this command, the function named by @var{linespec} or the
5350 function containing the line named by @var{linespec} will be skipped over when
5351 stepping. @xref{Specify Location}.
5353 If you do not specify @var{linespec}, the function you're currently debugging
5356 (If you have a function called @code{file} that you want to skip, use
5357 @kbd{skip function file}.)
5360 @item skip file @r{[}@var{filename}@r{]}
5361 After running this command, any function whose source lives in @var{filename}
5362 will be skipped over when stepping.
5364 If you do not specify @var{filename}, functions whose source lives in the file
5365 you're currently debugging will be skipped.
5368 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5369 These are the commands for managing your list of skips:
5373 @item info skip @r{[}@var{range}@r{]}
5374 Print details about the specified skip(s). If @var{range} is not specified,
5375 print a table with details about all functions and files marked for skipping.
5376 @code{info skip} prints the following information about each skip:
5380 A number identifying this skip.
5382 The type of this skip, either @samp{function} or @samp{file}.
5383 @item Enabled or Disabled
5384 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5386 For function skips, this column indicates the address in memory of the function
5387 being skipped. If you've set a function skip on a function which has not yet
5388 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5389 which has the function is loaded, @code{info skip} will show the function's
5392 For file skips, this field contains the filename being skipped. For functions
5393 skips, this field contains the function name and its line number in the file
5394 where it is defined.
5398 @item skip delete @r{[}@var{range}@r{]}
5399 Delete the specified skip(s). If @var{range} is not specified, delete all
5403 @item skip enable @r{[}@var{range}@r{]}
5404 Enable the specified skip(s). If @var{range} is not specified, enable all
5407 @kindex skip disable
5408 @item skip disable @r{[}@var{range}@r{]}
5409 Disable the specified skip(s). If @var{range} is not specified, disable all
5418 A signal is an asynchronous event that can happen in a program. The
5419 operating system defines the possible kinds of signals, and gives each
5420 kind a name and a number. For example, in Unix @code{SIGINT} is the
5421 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5422 @code{SIGSEGV} is the signal a program gets from referencing a place in
5423 memory far away from all the areas in use; @code{SIGALRM} occurs when
5424 the alarm clock timer goes off (which happens only if your program has
5425 requested an alarm).
5427 @cindex fatal signals
5428 Some signals, including @code{SIGALRM}, are a normal part of the
5429 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5430 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5431 program has not specified in advance some other way to handle the signal.
5432 @code{SIGINT} does not indicate an error in your program, but it is normally
5433 fatal so it can carry out the purpose of the interrupt: to kill the program.
5435 @value{GDBN} has the ability to detect any occurrence of a signal in your
5436 program. You can tell @value{GDBN} in advance what to do for each kind of
5439 @cindex handling signals
5440 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5441 @code{SIGALRM} be silently passed to your program
5442 (so as not to interfere with their role in the program's functioning)
5443 but to stop your program immediately whenever an error signal happens.
5444 You can change these settings with the @code{handle} command.
5447 @kindex info signals
5451 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5452 handle each one. You can use this to see the signal numbers of all
5453 the defined types of signals.
5455 @item info signals @var{sig}
5456 Similar, but print information only about the specified signal number.
5458 @code{info handle} is an alias for @code{info signals}.
5460 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5461 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5462 for details about this command.
5465 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5466 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5467 can be the number of a signal or its name (with or without the
5468 @samp{SIG} at the beginning); a list of signal numbers of the form
5469 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5470 known signals. Optional arguments @var{keywords}, described below,
5471 say what change to make.
5475 The keywords allowed by the @code{handle} command can be abbreviated.
5476 Their full names are:
5480 @value{GDBN} should not stop your program when this signal happens. It may
5481 still print a message telling you that the signal has come in.
5484 @value{GDBN} should stop your program when this signal happens. This implies
5485 the @code{print} keyword as well.
5488 @value{GDBN} should print a message when this signal happens.
5491 @value{GDBN} should not mention the occurrence of the signal at all. This
5492 implies the @code{nostop} keyword as well.
5496 @value{GDBN} should allow your program to see this signal; your program
5497 can handle the signal, or else it may terminate if the signal is fatal
5498 and not handled. @code{pass} and @code{noignore} are synonyms.
5502 @value{GDBN} should not allow your program to see this signal.
5503 @code{nopass} and @code{ignore} are synonyms.
5507 When a signal stops your program, the signal is not visible to the
5509 continue. Your program sees the signal then, if @code{pass} is in
5510 effect for the signal in question @emph{at that time}. In other words,
5511 after @value{GDBN} reports a signal, you can use the @code{handle}
5512 command with @code{pass} or @code{nopass} to control whether your
5513 program sees that signal when you continue.
5515 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5516 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5517 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5520 You can also use the @code{signal} command to prevent your program from
5521 seeing a signal, or cause it to see a signal it normally would not see,
5522 or to give it any signal at any time. For example, if your program stopped
5523 due to some sort of memory reference error, you might store correct
5524 values into the erroneous variables and continue, hoping to see more
5525 execution; but your program would probably terminate immediately as
5526 a result of the fatal signal once it saw the signal. To prevent this,
5527 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5530 @cindex extra signal information
5531 @anchor{extra signal information}
5533 On some targets, @value{GDBN} can inspect extra signal information
5534 associated with the intercepted signal, before it is actually
5535 delivered to the program being debugged. This information is exported
5536 by the convenience variable @code{$_siginfo}, and consists of data
5537 that is passed by the kernel to the signal handler at the time of the
5538 receipt of a signal. The data type of the information itself is
5539 target dependent. You can see the data type using the @code{ptype
5540 $_siginfo} command. On Unix systems, it typically corresponds to the
5541 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5544 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5545 referenced address that raised a segmentation fault.
5549 (@value{GDBP}) continue
5550 Program received signal SIGSEGV, Segmentation fault.
5551 0x0000000000400766 in main ()
5553 (@value{GDBP}) ptype $_siginfo
5560 struct @{...@} _kill;
5561 struct @{...@} _timer;
5563 struct @{...@} _sigchld;
5564 struct @{...@} _sigfault;
5565 struct @{...@} _sigpoll;
5568 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5572 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5573 $1 = (void *) 0x7ffff7ff7000
5577 Depending on target support, @code{$_siginfo} may also be writable.
5580 @section Stopping and Starting Multi-thread Programs
5582 @cindex stopped threads
5583 @cindex threads, stopped
5585 @cindex continuing threads
5586 @cindex threads, continuing
5588 @value{GDBN} supports debugging programs with multiple threads
5589 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5590 are two modes of controlling execution of your program within the
5591 debugger. In the default mode, referred to as @dfn{all-stop mode},
5592 when any thread in your program stops (for example, at a breakpoint
5593 or while being stepped), all other threads in the program are also stopped by
5594 @value{GDBN}. On some targets, @value{GDBN} also supports
5595 @dfn{non-stop mode}, in which other threads can continue to run freely while
5596 you examine the stopped thread in the debugger.
5599 * All-Stop Mode:: All threads stop when GDB takes control
5600 * Non-Stop Mode:: Other threads continue to execute
5601 * Background Execution:: Running your program asynchronously
5602 * Thread-Specific Breakpoints:: Controlling breakpoints
5603 * Interrupted System Calls:: GDB may interfere with system calls
5604 * Observer Mode:: GDB does not alter program behavior
5608 @subsection All-Stop Mode
5610 @cindex all-stop mode
5612 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5613 @emph{all} threads of execution stop, not just the current thread. This
5614 allows you to examine the overall state of the program, including
5615 switching between threads, without worrying that things may change
5618 Conversely, whenever you restart the program, @emph{all} threads start
5619 executing. @emph{This is true even when single-stepping} with commands
5620 like @code{step} or @code{next}.
5622 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5623 Since thread scheduling is up to your debugging target's operating
5624 system (not controlled by @value{GDBN}), other threads may
5625 execute more than one statement while the current thread completes a
5626 single step. Moreover, in general other threads stop in the middle of a
5627 statement, rather than at a clean statement boundary, when the program
5630 You might even find your program stopped in another thread after
5631 continuing or even single-stepping. This happens whenever some other
5632 thread runs into a breakpoint, a signal, or an exception before the
5633 first thread completes whatever you requested.
5635 @cindex automatic thread selection
5636 @cindex switching threads automatically
5637 @cindex threads, automatic switching
5638 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5639 signal, it automatically selects the thread where that breakpoint or
5640 signal happened. @value{GDBN} alerts you to the context switch with a
5641 message such as @samp{[Switching to Thread @var{n}]} to identify the
5644 On some OSes, you can modify @value{GDBN}'s default behavior by
5645 locking the OS scheduler to allow only a single thread to run.
5648 @item set scheduler-locking @var{mode}
5649 @cindex scheduler locking mode
5650 @cindex lock scheduler
5651 Set the scheduler locking mode. If it is @code{off}, then there is no
5652 locking and any thread may run at any time. If @code{on}, then only the
5653 current thread may run when the inferior is resumed. The @code{step}
5654 mode optimizes for single-stepping; it prevents other threads
5655 from preempting the current thread while you are stepping, so that
5656 the focus of debugging does not change unexpectedly.
5657 Other threads only rarely (or never) get a chance to run
5658 when you step. They are more likely to run when you @samp{next} over a
5659 function call, and they are completely free to run when you use commands
5660 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5661 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5662 the current thread away from the thread that you are debugging.
5664 @item show scheduler-locking
5665 Display the current scheduler locking mode.
5668 @cindex resume threads of multiple processes simultaneously
5669 By default, when you issue one of the execution commands such as
5670 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5671 threads of the current inferior to run. For example, if @value{GDBN}
5672 is attached to two inferiors, each with two threads, the
5673 @code{continue} command resumes only the two threads of the current
5674 inferior. This is useful, for example, when you debug a program that
5675 forks and you want to hold the parent stopped (so that, for instance,
5676 it doesn't run to exit), while you debug the child. In other
5677 situations, you may not be interested in inspecting the current state
5678 of any of the processes @value{GDBN} is attached to, and you may want
5679 to resume them all until some breakpoint is hit. In the latter case,
5680 you can instruct @value{GDBN} to allow all threads of all the
5681 inferiors to run with the @w{@code{set schedule-multiple}} command.
5684 @kindex set schedule-multiple
5685 @item set schedule-multiple
5686 Set the mode for allowing threads of multiple processes to be resumed
5687 when an execution command is issued. When @code{on}, all threads of
5688 all processes are allowed to run. When @code{off}, only the threads
5689 of the current process are resumed. The default is @code{off}. The
5690 @code{scheduler-locking} mode takes precedence when set to @code{on},
5691 or while you are stepping and set to @code{step}.
5693 @item show schedule-multiple
5694 Display the current mode for resuming the execution of threads of
5699 @subsection Non-Stop Mode
5701 @cindex non-stop mode
5703 @c This section is really only a place-holder, and needs to be expanded
5704 @c with more details.
5706 For some multi-threaded targets, @value{GDBN} supports an optional
5707 mode of operation in which you can examine stopped program threads in
5708 the debugger while other threads continue to execute freely. This
5709 minimizes intrusion when debugging live systems, such as programs
5710 where some threads have real-time constraints or must continue to
5711 respond to external events. This is referred to as @dfn{non-stop} mode.
5713 In non-stop mode, when a thread stops to report a debugging event,
5714 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5715 threads as well, in contrast to the all-stop mode behavior. Additionally,
5716 execution commands such as @code{continue} and @code{step} apply by default
5717 only to the current thread in non-stop mode, rather than all threads as
5718 in all-stop mode. This allows you to control threads explicitly in
5719 ways that are not possible in all-stop mode --- for example, stepping
5720 one thread while allowing others to run freely, stepping
5721 one thread while holding all others stopped, or stepping several threads
5722 independently and simultaneously.
5724 To enter non-stop mode, use this sequence of commands before you run
5725 or attach to your program:
5728 # Enable the async interface.
5731 # If using the CLI, pagination breaks non-stop.
5734 # Finally, turn it on!
5738 You can use these commands to manipulate the non-stop mode setting:
5741 @kindex set non-stop
5742 @item set non-stop on
5743 Enable selection of non-stop mode.
5744 @item set non-stop off
5745 Disable selection of non-stop mode.
5746 @kindex show non-stop
5748 Show the current non-stop enablement setting.
5751 Note these commands only reflect whether non-stop mode is enabled,
5752 not whether the currently-executing program is being run in non-stop mode.
5753 In particular, the @code{set non-stop} preference is only consulted when
5754 @value{GDBN} starts or connects to the target program, and it is generally
5755 not possible to switch modes once debugging has started. Furthermore,
5756 since not all targets support non-stop mode, even when you have enabled
5757 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5760 In non-stop mode, all execution commands apply only to the current thread
5761 by default. That is, @code{continue} only continues one thread.
5762 To continue all threads, issue @code{continue -a} or @code{c -a}.
5764 You can use @value{GDBN}'s background execution commands
5765 (@pxref{Background Execution}) to run some threads in the background
5766 while you continue to examine or step others from @value{GDBN}.
5767 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5768 always executed asynchronously in non-stop mode.
5770 Suspending execution is done with the @code{interrupt} command when
5771 running in the background, or @kbd{Ctrl-c} during foreground execution.
5772 In all-stop mode, this stops the whole process;
5773 but in non-stop mode the interrupt applies only to the current thread.
5774 To stop the whole program, use @code{interrupt -a}.
5776 Other execution commands do not currently support the @code{-a} option.
5778 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5779 that thread current, as it does in all-stop mode. This is because the
5780 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5781 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5782 changed to a different thread just as you entered a command to operate on the
5783 previously current thread.
5785 @node Background Execution
5786 @subsection Background Execution
5788 @cindex foreground execution
5789 @cindex background execution
5790 @cindex asynchronous execution
5791 @cindex execution, foreground, background and asynchronous
5793 @value{GDBN}'s execution commands have two variants: the normal
5794 foreground (synchronous) behavior, and a background
5795 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5796 the program to report that some thread has stopped before prompting for
5797 another command. In background execution, @value{GDBN} immediately gives
5798 a command prompt so that you can issue other commands while your program runs.
5800 You need to explicitly enable asynchronous mode before you can use
5801 background execution commands. You can use these commands to
5802 manipulate the asynchronous mode setting:
5805 @kindex set target-async
5806 @item set target-async on
5807 Enable asynchronous mode.
5808 @item set target-async off
5809 Disable asynchronous mode.
5810 @kindex show target-async
5811 @item show target-async
5812 Show the current target-async setting.
5815 If the target doesn't support async mode, @value{GDBN} issues an error
5816 message if you attempt to use the background execution commands.
5818 To specify background execution, add a @code{&} to the command. For example,
5819 the background form of the @code{continue} command is @code{continue&}, or
5820 just @code{c&}. The execution commands that accept background execution
5826 @xref{Starting, , Starting your Program}.
5830 @xref{Attach, , Debugging an Already-running Process}.
5834 @xref{Continuing and Stepping, step}.
5838 @xref{Continuing and Stepping, stepi}.
5842 @xref{Continuing and Stepping, next}.
5846 @xref{Continuing and Stepping, nexti}.
5850 @xref{Continuing and Stepping, continue}.
5854 @xref{Continuing and Stepping, finish}.
5858 @xref{Continuing and Stepping, until}.
5862 Background execution is especially useful in conjunction with non-stop
5863 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5864 However, you can also use these commands in the normal all-stop mode with
5865 the restriction that you cannot issue another execution command until the
5866 previous one finishes. Examples of commands that are valid in all-stop
5867 mode while the program is running include @code{help} and @code{info break}.
5869 You can interrupt your program while it is running in the background by
5870 using the @code{interrupt} command.
5877 Suspend execution of the running program. In all-stop mode,
5878 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5879 only the current thread. To stop the whole program in non-stop mode,
5880 use @code{interrupt -a}.
5883 @node Thread-Specific Breakpoints
5884 @subsection Thread-Specific Breakpoints
5886 When your program has multiple threads (@pxref{Threads,, Debugging
5887 Programs with Multiple Threads}), you can choose whether to set
5888 breakpoints on all threads, or on a particular thread.
5891 @cindex breakpoints and threads
5892 @cindex thread breakpoints
5893 @kindex break @dots{} thread @var{threadno}
5894 @item break @var{linespec} thread @var{threadno}
5895 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5896 @var{linespec} specifies source lines; there are several ways of
5897 writing them (@pxref{Specify Location}), but the effect is always to
5898 specify some source line.
5900 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5901 to specify that you only want @value{GDBN} to stop the program when a
5902 particular thread reaches this breakpoint. @var{threadno} is one of the
5903 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5904 column of the @samp{info threads} display.
5906 If you do not specify @samp{thread @var{threadno}} when you set a
5907 breakpoint, the breakpoint applies to @emph{all} threads of your
5910 You can use the @code{thread} qualifier on conditional breakpoints as
5911 well; in this case, place @samp{thread @var{threadno}} before or
5912 after the breakpoint condition, like this:
5915 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5920 Thread-specific breakpoints are automatically deleted when
5921 @value{GDBN} detects the corresponding thread is no longer in the
5922 thread list. For example:
5926 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
5929 There are several ways for a thread to disappear, such as a regular
5930 thread exit, but also when you detach from the process with the
5931 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
5932 Process}), or if @value{GDBN} loses the remote connection
5933 (@pxref{Remote Debugging}), etc. Note that with some targets,
5934 @value{GDBN} is only able to detect a thread has exited when the user
5935 explictly asks for the thread list with the @code{info threads}
5938 @node Interrupted System Calls
5939 @subsection Interrupted System Calls
5941 @cindex thread breakpoints and system calls
5942 @cindex system calls and thread breakpoints
5943 @cindex premature return from system calls
5944 There is an unfortunate side effect when using @value{GDBN} to debug
5945 multi-threaded programs. If one thread stops for a
5946 breakpoint, or for some other reason, and another thread is blocked in a
5947 system call, then the system call may return prematurely. This is a
5948 consequence of the interaction between multiple threads and the signals
5949 that @value{GDBN} uses to implement breakpoints and other events that
5952 To handle this problem, your program should check the return value of
5953 each system call and react appropriately. This is good programming
5956 For example, do not write code like this:
5962 The call to @code{sleep} will return early if a different thread stops
5963 at a breakpoint or for some other reason.
5965 Instead, write this:
5970 unslept = sleep (unslept);
5973 A system call is allowed to return early, so the system is still
5974 conforming to its specification. But @value{GDBN} does cause your
5975 multi-threaded program to behave differently than it would without
5978 Also, @value{GDBN} uses internal breakpoints in the thread library to
5979 monitor certain events such as thread creation and thread destruction.
5980 When such an event happens, a system call in another thread may return
5981 prematurely, even though your program does not appear to stop.
5984 @subsection Observer Mode
5986 If you want to build on non-stop mode and observe program behavior
5987 without any chance of disruption by @value{GDBN}, you can set
5988 variables to disable all of the debugger's attempts to modify state,
5989 whether by writing memory, inserting breakpoints, etc. These operate
5990 at a low level, intercepting operations from all commands.
5992 When all of these are set to @code{off}, then @value{GDBN} is said to
5993 be @dfn{observer mode}. As a convenience, the variable
5994 @code{observer} can be set to disable these, plus enable non-stop
5997 Note that @value{GDBN} will not prevent you from making nonsensical
5998 combinations of these settings. For instance, if you have enabled
5999 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6000 then breakpoints that work by writing trap instructions into the code
6001 stream will still not be able to be placed.
6006 @item set observer on
6007 @itemx set observer off
6008 When set to @code{on}, this disables all the permission variables
6009 below (except for @code{insert-fast-tracepoints}), plus enables
6010 non-stop debugging. Setting this to @code{off} switches back to
6011 normal debugging, though remaining in non-stop mode.
6014 Show whether observer mode is on or off.
6016 @kindex may-write-registers
6017 @item set may-write-registers on
6018 @itemx set may-write-registers off
6019 This controls whether @value{GDBN} will attempt to alter the values of
6020 registers, such as with assignment expressions in @code{print}, or the
6021 @code{jump} command. It defaults to @code{on}.
6023 @item show may-write-registers
6024 Show the current permission to write registers.
6026 @kindex may-write-memory
6027 @item set may-write-memory on
6028 @itemx set may-write-memory off
6029 This controls whether @value{GDBN} will attempt to alter the contents
6030 of memory, such as with assignment expressions in @code{print}. It
6031 defaults to @code{on}.
6033 @item show may-write-memory
6034 Show the current permission to write memory.
6036 @kindex may-insert-breakpoints
6037 @item set may-insert-breakpoints on
6038 @itemx set may-insert-breakpoints off
6039 This controls whether @value{GDBN} will attempt to insert breakpoints.
6040 This affects all breakpoints, including internal breakpoints defined
6041 by @value{GDBN}. It defaults to @code{on}.
6043 @item show may-insert-breakpoints
6044 Show the current permission to insert breakpoints.
6046 @kindex may-insert-tracepoints
6047 @item set may-insert-tracepoints on
6048 @itemx set may-insert-tracepoints off
6049 This controls whether @value{GDBN} will attempt to insert (regular)
6050 tracepoints at the beginning of a tracing experiment. It affects only
6051 non-fast tracepoints, fast tracepoints being under the control of
6052 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6054 @item show may-insert-tracepoints
6055 Show the current permission to insert tracepoints.
6057 @kindex may-insert-fast-tracepoints
6058 @item set may-insert-fast-tracepoints on
6059 @itemx set may-insert-fast-tracepoints off
6060 This controls whether @value{GDBN} will attempt to insert fast
6061 tracepoints at the beginning of a tracing experiment. It affects only
6062 fast tracepoints, regular (non-fast) tracepoints being under the
6063 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6065 @item show may-insert-fast-tracepoints
6066 Show the current permission to insert fast tracepoints.
6068 @kindex may-interrupt
6069 @item set may-interrupt on
6070 @itemx set may-interrupt off
6071 This controls whether @value{GDBN} will attempt to interrupt or stop
6072 program execution. When this variable is @code{off}, the
6073 @code{interrupt} command will have no effect, nor will
6074 @kbd{Ctrl-c}. It defaults to @code{on}.
6076 @item show may-interrupt
6077 Show the current permission to interrupt or stop the program.
6081 @node Reverse Execution
6082 @chapter Running programs backward
6083 @cindex reverse execution
6084 @cindex running programs backward
6086 When you are debugging a program, it is not unusual to realize that
6087 you have gone too far, and some event of interest has already happened.
6088 If the target environment supports it, @value{GDBN} can allow you to
6089 ``rewind'' the program by running it backward.
6091 A target environment that supports reverse execution should be able
6092 to ``undo'' the changes in machine state that have taken place as the
6093 program was executing normally. Variables, registers etc.@: should
6094 revert to their previous values. Obviously this requires a great
6095 deal of sophistication on the part of the target environment; not
6096 all target environments can support reverse execution.
6098 When a program is executed in reverse, the instructions that
6099 have most recently been executed are ``un-executed'', in reverse
6100 order. The program counter runs backward, following the previous
6101 thread of execution in reverse. As each instruction is ``un-executed'',
6102 the values of memory and/or registers that were changed by that
6103 instruction are reverted to their previous states. After executing
6104 a piece of source code in reverse, all side effects of that code
6105 should be ``undone'', and all variables should be returned to their
6106 prior values@footnote{
6107 Note that some side effects are easier to undo than others. For instance,
6108 memory and registers are relatively easy, but device I/O is hard. Some
6109 targets may be able undo things like device I/O, and some may not.
6111 The contract between @value{GDBN} and the reverse executing target
6112 requires only that the target do something reasonable when
6113 @value{GDBN} tells it to execute backwards, and then report the
6114 results back to @value{GDBN}. Whatever the target reports back to
6115 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6116 assumes that the memory and registers that the target reports are in a
6117 consistant state, but @value{GDBN} accepts whatever it is given.
6120 If you are debugging in a target environment that supports
6121 reverse execution, @value{GDBN} provides the following commands.
6124 @kindex reverse-continue
6125 @kindex rc @r{(@code{reverse-continue})}
6126 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6127 @itemx rc @r{[}@var{ignore-count}@r{]}
6128 Beginning at the point where your program last stopped, start executing
6129 in reverse. Reverse execution will stop for breakpoints and synchronous
6130 exceptions (signals), just like normal execution. Behavior of
6131 asynchronous signals depends on the target environment.
6133 @kindex reverse-step
6134 @kindex rs @r{(@code{step})}
6135 @item reverse-step @r{[}@var{count}@r{]}
6136 Run the program backward until control reaches the start of a
6137 different source line; then stop it, and return control to @value{GDBN}.
6139 Like the @code{step} command, @code{reverse-step} will only stop
6140 at the beginning of a source line. It ``un-executes'' the previously
6141 executed source line. If the previous source line included calls to
6142 debuggable functions, @code{reverse-step} will step (backward) into
6143 the called function, stopping at the beginning of the @emph{last}
6144 statement in the called function (typically a return statement).
6146 Also, as with the @code{step} command, if non-debuggable functions are
6147 called, @code{reverse-step} will run thru them backward without stopping.
6149 @kindex reverse-stepi
6150 @kindex rsi @r{(@code{reverse-stepi})}
6151 @item reverse-stepi @r{[}@var{count}@r{]}
6152 Reverse-execute one machine instruction. Note that the instruction
6153 to be reverse-executed is @emph{not} the one pointed to by the program
6154 counter, but the instruction executed prior to that one. For instance,
6155 if the last instruction was a jump, @code{reverse-stepi} will take you
6156 back from the destination of the jump to the jump instruction itself.
6158 @kindex reverse-next
6159 @kindex rn @r{(@code{reverse-next})}
6160 @item reverse-next @r{[}@var{count}@r{]}
6161 Run backward to the beginning of the previous line executed in
6162 the current (innermost) stack frame. If the line contains function
6163 calls, they will be ``un-executed'' without stopping. Starting from
6164 the first line of a function, @code{reverse-next} will take you back
6165 to the caller of that function, @emph{before} the function was called,
6166 just as the normal @code{next} command would take you from the last
6167 line of a function back to its return to its caller
6168 @footnote{Unless the code is too heavily optimized.}.
6170 @kindex reverse-nexti
6171 @kindex rni @r{(@code{reverse-nexti})}
6172 @item reverse-nexti @r{[}@var{count}@r{]}
6173 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6174 in reverse, except that called functions are ``un-executed'' atomically.
6175 That is, if the previously executed instruction was a return from
6176 another function, @code{reverse-nexti} will continue to execute
6177 in reverse until the call to that function (from the current stack
6180 @kindex reverse-finish
6181 @item reverse-finish
6182 Just as the @code{finish} command takes you to the point where the
6183 current function returns, @code{reverse-finish} takes you to the point
6184 where it was called. Instead of ending up at the end of the current
6185 function invocation, you end up at the beginning.
6187 @kindex set exec-direction
6188 @item set exec-direction
6189 Set the direction of target execution.
6190 @item set exec-direction reverse
6191 @cindex execute forward or backward in time
6192 @value{GDBN} will perform all execution commands in reverse, until the
6193 exec-direction mode is changed to ``forward''. Affected commands include
6194 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6195 command cannot be used in reverse mode.
6196 @item set exec-direction forward
6197 @value{GDBN} will perform all execution commands in the normal fashion.
6198 This is the default.
6202 @node Process Record and Replay
6203 @chapter Recording Inferior's Execution and Replaying It
6204 @cindex process record and replay
6205 @cindex recording inferior's execution and replaying it
6207 On some platforms, @value{GDBN} provides a special @dfn{process record
6208 and replay} target that can record a log of the process execution, and
6209 replay it later with both forward and reverse execution commands.
6212 When this target is in use, if the execution log includes the record
6213 for the next instruction, @value{GDBN} will debug in @dfn{replay
6214 mode}. In the replay mode, the inferior does not really execute code
6215 instructions. Instead, all the events that normally happen during
6216 code execution are taken from the execution log. While code is not
6217 really executed in replay mode, the values of registers (including the
6218 program counter register) and the memory of the inferior are still
6219 changed as they normally would. Their contents are taken from the
6223 If the record for the next instruction is not in the execution log,
6224 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6225 inferior executes normally, and @value{GDBN} records the execution log
6228 The process record and replay target supports reverse execution
6229 (@pxref{Reverse Execution}), even if the platform on which the
6230 inferior runs does not. However, the reverse execution is limited in
6231 this case by the range of the instructions recorded in the execution
6232 log. In other words, reverse execution on platforms that don't
6233 support it directly can only be done in the replay mode.
6235 When debugging in the reverse direction, @value{GDBN} will work in
6236 replay mode as long as the execution log includes the record for the
6237 previous instruction; otherwise, it will work in record mode, if the
6238 platform supports reverse execution, or stop if not.
6240 For architecture environments that support process record and replay,
6241 @value{GDBN} provides the following commands:
6244 @kindex target record
6245 @kindex target record-full
6246 @kindex target record-btrace
6249 @kindex record btrace
6253 @item record @var{method}
6254 This command starts the process record and replay target. The
6255 recording method can be specified as parameter. Without a parameter
6256 the command uses the @code{full} recording method. The following
6257 recording methods are available:
6261 Full record/replay recording using @value{GDBN}'s software record and
6262 replay implementation. This method allows replaying and reverse
6266 Hardware-supported instruction recording. This method does not allow
6267 replaying and reverse execution.
6269 This recording method may not be available on all processors.
6272 The process record and replay target can only debug a process that is
6273 already running. Therefore, you need first to start the process with
6274 the @kbd{run} or @kbd{start} commands, and then start the recording
6275 with the @kbd{record @var{method}} command.
6277 Both @code{record @var{method}} and @code{rec @var{method}} are
6278 aliases of @code{target record-@var{method}}.
6280 @cindex displaced stepping, and process record and replay
6281 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6282 will be automatically disabled when process record and replay target
6283 is started. That's because the process record and replay target
6284 doesn't support displaced stepping.
6286 @cindex non-stop mode, and process record and replay
6287 @cindex asynchronous execution, and process record and replay
6288 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6289 the asynchronous execution mode (@pxref{Background Execution}), not
6290 all recording methods are available. The @code{full} recording method
6291 does not support these two modes.
6296 Stop the process record and replay target. When process record and
6297 replay target stops, the entire execution log will be deleted and the
6298 inferior will either be terminated, or will remain in its final state.
6300 When you stop the process record and replay target in record mode (at
6301 the end of the execution log), the inferior will be stopped at the
6302 next instruction that would have been recorded. In other words, if
6303 you record for a while and then stop recording, the inferior process
6304 will be left in the same state as if the recording never happened.
6306 On the other hand, if the process record and replay target is stopped
6307 while in replay mode (that is, not at the end of the execution log,
6308 but at some earlier point), the inferior process will become ``live''
6309 at that earlier state, and it will then be possible to continue the
6310 usual ``live'' debugging of the process from that state.
6312 When the inferior process exits, or @value{GDBN} detaches from it,
6313 process record and replay target will automatically stop itself.
6317 Go to a specific location in the execution log. There are several
6318 ways to specify the location to go to:
6321 @item record goto begin
6322 @itemx record goto start
6323 Go to the beginning of the execution log.
6325 @item record goto end
6326 Go to the end of the execution log.
6328 @item record goto @var{n}
6329 Go to instruction number @var{n} in the execution log.
6333 @item record save @var{filename}
6334 Save the execution log to a file @file{@var{filename}}.
6335 Default filename is @file{gdb_record.@var{process_id}}, where
6336 @var{process_id} is the process ID of the inferior.
6338 This command may not be available for all recording methods.
6340 @kindex record restore
6341 @item record restore @var{filename}
6342 Restore the execution log from a file @file{@var{filename}}.
6343 File must have been created with @code{record save}.
6345 @kindex set record full
6346 @item set record full insn-number-max @var{limit}
6347 @itemx set record full insn-number-max unlimited
6348 Set the limit of instructions to be recorded for the @code{full}
6349 recording method. Default value is 200000.
6351 If @var{limit} is a positive number, then @value{GDBN} will start
6352 deleting instructions from the log once the number of the record
6353 instructions becomes greater than @var{limit}. For every new recorded
6354 instruction, @value{GDBN} will delete the earliest recorded
6355 instruction to keep the number of recorded instructions at the limit.
6356 (Since deleting recorded instructions loses information, @value{GDBN}
6357 lets you control what happens when the limit is reached, by means of
6358 the @code{stop-at-limit} option, described below.)
6360 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6361 delete recorded instructions from the execution log. The number of
6362 recorded instructions is limited only by the available memory.
6364 @kindex show record full
6365 @item show record full insn-number-max
6366 Show the limit of instructions to be recorded with the @code{full}
6369 @item set record full stop-at-limit
6370 Control the behavior of the @code{full} recording method when the
6371 number of recorded instructions reaches the limit. If ON (the
6372 default), @value{GDBN} will stop when the limit is reached for the
6373 first time and ask you whether you want to stop the inferior or
6374 continue running it and recording the execution log. If you decide
6375 to continue recording, each new recorded instruction will cause the
6376 oldest one to be deleted.
6378 If this option is OFF, @value{GDBN} will automatically delete the
6379 oldest record to make room for each new one, without asking.
6381 @item show record full stop-at-limit
6382 Show the current setting of @code{stop-at-limit}.
6384 @item set record full memory-query
6385 Control the behavior when @value{GDBN} is unable to record memory
6386 changes caused by an instruction for the @code{full} recording method.
6387 If ON, @value{GDBN} will query whether to stop the inferior in that
6390 If this option is OFF (the default), @value{GDBN} will automatically
6391 ignore the effect of such instructions on memory. Later, when
6392 @value{GDBN} replays this execution log, it will mark the log of this
6393 instruction as not accessible, and it will not affect the replay
6396 @item show record full memory-query
6397 Show the current setting of @code{memory-query}.
6401 Show various statistics about the recording depending on the recording
6406 For the @code{full} recording method, it shows the state of process
6407 record and its in-memory execution log buffer, including:
6411 Whether in record mode or replay mode.
6413 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6415 Highest recorded instruction number.
6417 Current instruction about to be replayed (if in replay mode).
6419 Number of instructions contained in the execution log.
6421 Maximum number of instructions that may be contained in the execution log.
6425 For the @code{btrace} recording method, it shows the number of
6426 instructions that have been recorded and the number of blocks of
6427 sequential control-flow that is formed by the recorded instructions.
6430 @kindex record delete
6433 When record target runs in replay mode (``in the past''), delete the
6434 subsequent execution log and begin to record a new execution log starting
6435 from the current address. This means you will abandon the previously
6436 recorded ``future'' and begin recording a new ``future''.
6438 @kindex record instruction-history
6439 @kindex rec instruction-history
6440 @item record instruction-history
6441 Disassembles instructions from the recorded execution log. By
6442 default, ten instructions are disassembled. This can be changed using
6443 the @code{set record instruction-history-size} command. Instructions
6444 are printed in execution order. There are several ways to specify
6445 what part of the execution log to disassemble:
6448 @item record instruction-history @var{insn}
6449 Disassembles ten instructions starting from instruction number
6452 @item record instruction-history @var{insn}, +/-@var{n}
6453 Disassembles @var{n} instructions around instruction number
6454 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6455 @var{n} instructions after instruction number @var{insn}. If
6456 @var{n} is preceded with @code{-}, disassembles @var{n}
6457 instructions before instruction number @var{insn}.
6459 @item record instruction-history
6460 Disassembles ten more instructions after the last disassembly.
6462 @item record instruction-history -
6463 Disassembles ten more instructions before the last disassembly.
6465 @item record instruction-history @var{begin} @var{end}
6466 Disassembles instructions beginning with instruction number
6467 @var{begin} until instruction number @var{end}. The instruction
6468 number @var{end} is not included.
6471 This command may not be available for all recording methods.
6474 @item set record instruction-history-size @var{size}
6475 @itemx set record instruction-history-size unlimited
6476 Define how many instructions to disassemble in the @code{record
6477 instruction-history} command. The default value is 10.
6478 A @var{size} of @code{unlimited} means unlimited instructions.
6481 @item show record instruction-history-size
6482 Show how many instructions to disassemble in the @code{record
6483 instruction-history} command.
6485 @kindex record function-call-history
6486 @kindex rec function-call-history
6487 @item record function-call-history
6488 Prints the execution history at function granularity. It prints one
6489 line for each sequence of instructions that belong to the same
6490 function giving the name of that function, the source lines
6491 for this instruction sequence (if the @code{/l} modifier is
6492 specified), and the instructions numbers that form the sequence (if
6493 the @code{/i} modifier is specified).
6496 (@value{GDBP}) @b{list 1, 10}
6507 (@value{GDBP}) @b{record function-call-history /l}
6513 By default, ten lines are printed. This can be changed using the
6514 @code{set record function-call-history-size} command. Functions are
6515 printed in execution order. There are several ways to specify what
6519 @item record function-call-history @var{func}
6520 Prints ten functions starting from function number @var{func}.
6522 @item record function-call-history @var{func}, +/-@var{n}
6523 Prints @var{n} functions around function number @var{func}. If
6524 @var{n} is preceded with @code{+}, prints @var{n} functions after
6525 function number @var{func}. If @var{n} is preceded with @code{-},
6526 prints @var{n} functions before function number @var{func}.
6528 @item record function-call-history
6529 Prints ten more functions after the last ten-line print.
6531 @item record function-call-history -
6532 Prints ten more functions before the last ten-line print.
6534 @item record function-call-history @var{begin} @var{end}
6535 Prints functions beginning with function number @var{begin} until
6536 function number @var{end}. The function number @var{end} is not
6540 This command may not be available for all recording methods.
6542 @item set record function-call-history-size @var{size}
6543 @itemx set record function-call-history-size unlimited
6544 Define how many lines to print in the
6545 @code{record function-call-history} command. The default value is 10.
6546 A size of @code{unlimited} means unlimited lines.
6548 @item show record function-call-history-size
6549 Show how many lines to print in the
6550 @code{record function-call-history} command.
6555 @chapter Examining the Stack
6557 When your program has stopped, the first thing you need to know is where it
6558 stopped and how it got there.
6561 Each time your program performs a function call, information about the call
6563 That information includes the location of the call in your program,
6564 the arguments of the call,
6565 and the local variables of the function being called.
6566 The information is saved in a block of data called a @dfn{stack frame}.
6567 The stack frames are allocated in a region of memory called the @dfn{call
6570 When your program stops, the @value{GDBN} commands for examining the
6571 stack allow you to see all of this information.
6573 @cindex selected frame
6574 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6575 @value{GDBN} commands refer implicitly to the selected frame. In
6576 particular, whenever you ask @value{GDBN} for the value of a variable in
6577 your program, the value is found in the selected frame. There are
6578 special @value{GDBN} commands to select whichever frame you are
6579 interested in. @xref{Selection, ,Selecting a Frame}.
6581 When your program stops, @value{GDBN} automatically selects the
6582 currently executing frame and describes it briefly, similar to the
6583 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6586 * Frames:: Stack frames
6587 * Backtrace:: Backtraces
6588 * Frame Filter Management:: Managing frame filters
6589 * Selection:: Selecting a frame
6590 * Frame Info:: Information on a frame
6595 @section Stack Frames
6597 @cindex frame, definition
6599 The call stack is divided up into contiguous pieces called @dfn{stack
6600 frames}, or @dfn{frames} for short; each frame is the data associated
6601 with one call to one function. The frame contains the arguments given
6602 to the function, the function's local variables, and the address at
6603 which the function is executing.
6605 @cindex initial frame
6606 @cindex outermost frame
6607 @cindex innermost frame
6608 When your program is started, the stack has only one frame, that of the
6609 function @code{main}. This is called the @dfn{initial} frame or the
6610 @dfn{outermost} frame. Each time a function is called, a new frame is
6611 made. Each time a function returns, the frame for that function invocation
6612 is eliminated. If a function is recursive, there can be many frames for
6613 the same function. The frame for the function in which execution is
6614 actually occurring is called the @dfn{innermost} frame. This is the most
6615 recently created of all the stack frames that still exist.
6617 @cindex frame pointer
6618 Inside your program, stack frames are identified by their addresses. A
6619 stack frame consists of many bytes, each of which has its own address; each
6620 kind of computer has a convention for choosing one byte whose
6621 address serves as the address of the frame. Usually this address is kept
6622 in a register called the @dfn{frame pointer register}
6623 (@pxref{Registers, $fp}) while execution is going on in that frame.
6625 @cindex frame number
6626 @value{GDBN} assigns numbers to all existing stack frames, starting with
6627 zero for the innermost frame, one for the frame that called it,
6628 and so on upward. These numbers do not really exist in your program;
6629 they are assigned by @value{GDBN} to give you a way of designating stack
6630 frames in @value{GDBN} commands.
6632 @c The -fomit-frame-pointer below perennially causes hbox overflow
6633 @c underflow problems.
6634 @cindex frameless execution
6635 Some compilers provide a way to compile functions so that they operate
6636 without stack frames. (For example, the @value{NGCC} option
6638 @samp{-fomit-frame-pointer}
6640 generates functions without a frame.)
6641 This is occasionally done with heavily used library functions to save
6642 the frame setup time. @value{GDBN} has limited facilities for dealing
6643 with these function invocations. If the innermost function invocation
6644 has no stack frame, @value{GDBN} nevertheless regards it as though
6645 it had a separate frame, which is numbered zero as usual, allowing
6646 correct tracing of the function call chain. However, @value{GDBN} has
6647 no provision for frameless functions elsewhere in the stack.
6650 @kindex frame@r{, command}
6651 @cindex current stack frame
6652 @item frame @var{args}
6653 The @code{frame} command allows you to move from one stack frame to another,
6654 and to print the stack frame you select. @var{args} may be either the
6655 address of the frame or the stack frame number. Without an argument,
6656 @code{frame} prints the current stack frame.
6658 @kindex select-frame
6659 @cindex selecting frame silently
6661 The @code{select-frame} command allows you to move from one stack frame
6662 to another without printing the frame. This is the silent version of
6670 @cindex call stack traces
6671 A backtrace is a summary of how your program got where it is. It shows one
6672 line per frame, for many frames, starting with the currently executing
6673 frame (frame zero), followed by its caller (frame one), and on up the
6676 @anchor{backtrace-command}
6679 @kindex bt @r{(@code{backtrace})}
6682 Print a backtrace of the entire stack: one line per frame for all
6683 frames in the stack.
6685 You can stop the backtrace at any time by typing the system interrupt
6686 character, normally @kbd{Ctrl-c}.
6688 @item backtrace @var{n}
6690 Similar, but print only the innermost @var{n} frames.
6692 @item backtrace -@var{n}
6694 Similar, but print only the outermost @var{n} frames.
6696 @item backtrace full
6698 @itemx bt full @var{n}
6699 @itemx bt full -@var{n}
6700 Print the values of the local variables also. @var{n} specifies the
6701 number of frames to print, as described above.
6703 @item backtrace no-filters
6704 @itemx bt no-filters
6705 @itemx bt no-filters @var{n}
6706 @itemx bt no-filters -@var{n}
6707 @itemx bt no-filters full
6708 @itemx bt no-filters full @var{n}
6709 @itemx bt no-filters full -@var{n}
6710 Do not run Python frame filters on this backtrace. @xref{Frame
6711 Filter API}, for more information. Additionally use @ref{disable
6712 frame-filter all} to turn off all frame filters. This is only
6713 relevant when @value{GDBN} has been configured with @code{Python}
6719 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6720 are additional aliases for @code{backtrace}.
6722 @cindex multiple threads, backtrace
6723 In a multi-threaded program, @value{GDBN} by default shows the
6724 backtrace only for the current thread. To display the backtrace for
6725 several or all of the threads, use the command @code{thread apply}
6726 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6727 apply all backtrace}, @value{GDBN} will display the backtrace for all
6728 the threads; this is handy when you debug a core dump of a
6729 multi-threaded program.
6731 Each line in the backtrace shows the frame number and the function name.
6732 The program counter value is also shown---unless you use @code{set
6733 print address off}. The backtrace also shows the source file name and
6734 line number, as well as the arguments to the function. The program
6735 counter value is omitted if it is at the beginning of the code for that
6738 Here is an example of a backtrace. It was made with the command
6739 @samp{bt 3}, so it shows the innermost three frames.
6743 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6745 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6746 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6748 (More stack frames follow...)
6753 The display for frame zero does not begin with a program counter
6754 value, indicating that your program has stopped at the beginning of the
6755 code for line @code{993} of @code{builtin.c}.
6758 The value of parameter @code{data} in frame 1 has been replaced by
6759 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6760 only if it is a scalar (integer, pointer, enumeration, etc). See command
6761 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6762 on how to configure the way function parameter values are printed.
6764 @cindex optimized out, in backtrace
6765 @cindex function call arguments, optimized out
6766 If your program was compiled with optimizations, some compilers will
6767 optimize away arguments passed to functions if those arguments are
6768 never used after the call. Such optimizations generate code that
6769 passes arguments through registers, but doesn't store those arguments
6770 in the stack frame. @value{GDBN} has no way of displaying such
6771 arguments in stack frames other than the innermost one. Here's what
6772 such a backtrace might look like:
6776 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6778 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6779 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6781 (More stack frames follow...)
6786 The values of arguments that were not saved in their stack frames are
6787 shown as @samp{<optimized out>}.
6789 If you need to display the values of such optimized-out arguments,
6790 either deduce that from other variables whose values depend on the one
6791 you are interested in, or recompile without optimizations.
6793 @cindex backtrace beyond @code{main} function
6794 @cindex program entry point
6795 @cindex startup code, and backtrace
6796 Most programs have a standard user entry point---a place where system
6797 libraries and startup code transition into user code. For C this is
6798 @code{main}@footnote{
6799 Note that embedded programs (the so-called ``free-standing''
6800 environment) are not required to have a @code{main} function as the
6801 entry point. They could even have multiple entry points.}.
6802 When @value{GDBN} finds the entry function in a backtrace
6803 it will terminate the backtrace, to avoid tracing into highly
6804 system-specific (and generally uninteresting) code.
6806 If you need to examine the startup code, or limit the number of levels
6807 in a backtrace, you can change this behavior:
6810 @item set backtrace past-main
6811 @itemx set backtrace past-main on
6812 @kindex set backtrace
6813 Backtraces will continue past the user entry point.
6815 @item set backtrace past-main off
6816 Backtraces will stop when they encounter the user entry point. This is the
6819 @item show backtrace past-main
6820 @kindex show backtrace
6821 Display the current user entry point backtrace policy.
6823 @item set backtrace past-entry
6824 @itemx set backtrace past-entry on
6825 Backtraces will continue past the internal entry point of an application.
6826 This entry point is encoded by the linker when the application is built,
6827 and is likely before the user entry point @code{main} (or equivalent) is called.
6829 @item set backtrace past-entry off
6830 Backtraces will stop when they encounter the internal entry point of an
6831 application. This is the default.
6833 @item show backtrace past-entry
6834 Display the current internal entry point backtrace policy.
6836 @item set backtrace limit @var{n}
6837 @itemx set backtrace limit 0
6838 @itemx set backtrace limit unlimited
6839 @cindex backtrace limit
6840 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6841 or zero means unlimited levels.
6843 @item show backtrace limit
6844 Display the current limit on backtrace levels.
6847 You can control how file names are displayed.
6850 @item set filename-display
6851 @itemx set filename-display relative
6852 @cindex filename-display
6853 Display file names relative to the compilation directory. This is the default.
6855 @item set filename-display basename
6856 Display only basename of a filename.
6858 @item set filename-display absolute
6859 Display an absolute filename.
6861 @item show filename-display
6862 Show the current way to display filenames.
6865 @node Frame Filter Management
6866 @section Management of Frame Filters.
6867 @cindex managing frame filters
6869 Frame filters are Python based utilities to manage and decorate the
6870 output of frames. @xref{Frame Filter API}, for further information.
6872 Managing frame filters is performed by several commands available
6873 within @value{GDBN}, detailed here.
6876 @kindex info frame-filter
6877 @item info frame-filter
6878 Print a list of installed frame filters from all dictionaries, showing
6879 their name, priority and enabled status.
6881 @kindex disable frame-filter
6882 @anchor{disable frame-filter all}
6883 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6884 Disable a frame filter in the dictionary matching
6885 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6886 @var{filter-dictionary} may be @code{all}, @code{global},
6887 @code{progspace} or the name of the object file where the frame filter
6888 dictionary resides. When @code{all} is specified, all frame filters
6889 across all dictionaries are disabled. @var{filter-name} is the name
6890 of the frame filter and is used when @code{all} is not the option for
6891 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6892 may be enabled again later.
6894 @kindex enable frame-filter
6895 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6896 Enable a frame filter in the dictionary matching
6897 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6898 @var{filter-dictionary} may be @code{all}, @code{global},
6899 @code{progspace} or the name of the object file where the frame filter
6900 dictionary resides. When @code{all} is specified, all frame filters across
6901 all dictionaries are enabled. @var{filter-name} is the name of the frame
6902 filter and is used when @code{all} is not the option for
6903 @var{filter-dictionary}.
6908 (gdb) info frame-filter
6910 global frame-filters:
6911 Priority Enabled Name
6912 1000 No PrimaryFunctionFilter
6915 progspace /build/test frame-filters:
6916 Priority Enabled Name
6917 100 Yes ProgspaceFilter
6919 objfile /build/test frame-filters:
6920 Priority Enabled Name
6921 999 Yes BuildProgra Filter
6923 (gdb) disable frame-filter /build/test BuildProgramFilter
6924 (gdb) info frame-filter
6926 global frame-filters:
6927 Priority Enabled Name
6928 1000 No PrimaryFunctionFilter
6931 progspace /build/test frame-filters:
6932 Priority Enabled Name
6933 100 Yes ProgspaceFilter
6935 objfile /build/test frame-filters:
6936 Priority Enabled Name
6937 999 No BuildProgramFilter
6939 (gdb) enable frame-filter global PrimaryFunctionFilter
6940 (gdb) info frame-filter
6942 global frame-filters:
6943 Priority Enabled Name
6944 1000 Yes PrimaryFunctionFilter
6947 progspace /build/test frame-filters:
6948 Priority Enabled Name
6949 100 Yes ProgspaceFilter
6951 objfile /build/test frame-filters:
6952 Priority Enabled Name
6953 999 No BuildProgramFilter
6956 @kindex set frame-filter priority
6957 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6958 Set 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
6962 dictionary resides. @var{priority} is an integer.
6964 @kindex show frame-filter priority
6965 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6966 Show the @var{priority} of a frame filter in the dictionary matching
6967 @var{filter-dictionary}, and the frame filter name matching
6968 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6969 @code{progspace} or the name of the object file where the frame filter
6975 (gdb) info frame-filter
6977 global frame-filters:
6978 Priority Enabled Name
6979 1000 Yes PrimaryFunctionFilter
6982 progspace /build/test frame-filters:
6983 Priority Enabled Name
6984 100 Yes ProgspaceFilter
6986 objfile /build/test frame-filters:
6987 Priority Enabled Name
6988 999 No BuildProgramFilter
6990 (gdb) set frame-filter priority global Reverse 50
6991 (gdb) info frame-filter
6993 global frame-filters:
6994 Priority Enabled Name
6995 1000 Yes PrimaryFunctionFilter
6998 progspace /build/test frame-filters:
6999 Priority Enabled Name
7000 100 Yes ProgspaceFilter
7002 objfile /build/test frame-filters:
7003 Priority Enabled Name
7004 999 No BuildProgramFilter
7009 @section Selecting a Frame
7011 Most commands for examining the stack and other data in your program work on
7012 whichever stack frame is selected at the moment. Here are the commands for
7013 selecting a stack frame; all of them finish by printing a brief description
7014 of the stack frame just selected.
7017 @kindex frame@r{, selecting}
7018 @kindex f @r{(@code{frame})}
7021 Select frame number @var{n}. Recall that frame zero is the innermost
7022 (currently executing) frame, frame one is the frame that called the
7023 innermost one, and so on. The highest-numbered frame is the one for
7026 @item frame @var{addr}
7028 Select the frame at address @var{addr}. This is useful mainly if the
7029 chaining of stack frames has been damaged by a bug, making it
7030 impossible for @value{GDBN} to assign numbers properly to all frames. In
7031 addition, this can be useful when your program has multiple stacks and
7032 switches between them.
7034 On the SPARC architecture, @code{frame} needs two addresses to
7035 select an arbitrary frame: a frame pointer and a stack pointer.
7037 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
7038 pointer and a program counter.
7040 On the 29k architecture, it needs three addresses: a register stack
7041 pointer, a program counter, and a memory stack pointer.
7045 Move @var{n} frames up the stack. For positive numbers @var{n}, this
7046 advances toward the outermost frame, to higher frame numbers, to frames
7047 that have existed longer. @var{n} defaults to one.
7050 @kindex do @r{(@code{down})}
7052 Move @var{n} frames down the stack. For positive numbers @var{n}, this
7053 advances toward the innermost frame, to lower frame numbers, to frames
7054 that were created more recently. @var{n} defaults to one. You may
7055 abbreviate @code{down} as @code{do}.
7058 All of these commands end by printing two lines of output describing the
7059 frame. The first line shows the frame number, the function name, the
7060 arguments, and the source file and line number of execution in that
7061 frame. The second line shows the text of that source line.
7069 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7071 10 read_input_file (argv[i]);
7075 After such a printout, the @code{list} command with no arguments
7076 prints ten lines centered on the point of execution in the frame.
7077 You can also edit the program at the point of execution with your favorite
7078 editing program by typing @code{edit}.
7079 @xref{List, ,Printing Source Lines},
7083 @kindex down-silently
7085 @item up-silently @var{n}
7086 @itemx down-silently @var{n}
7087 These two commands are variants of @code{up} and @code{down},
7088 respectively; they differ in that they do their work silently, without
7089 causing display of the new frame. They are intended primarily for use
7090 in @value{GDBN} command scripts, where the output might be unnecessary and
7095 @section Information About a Frame
7097 There are several other commands to print information about the selected
7103 When used without any argument, this command does not change which
7104 frame is selected, but prints a brief description of the currently
7105 selected stack frame. It can be abbreviated @code{f}. With an
7106 argument, this command is used to select a stack frame.
7107 @xref{Selection, ,Selecting a Frame}.
7110 @kindex info f @r{(@code{info frame})}
7113 This command prints a verbose description of the selected stack frame,
7118 the address of the frame
7120 the address of the next frame down (called by this frame)
7122 the address of the next frame up (caller of this frame)
7124 the language in which the source code corresponding to this frame is written
7126 the address of the frame's arguments
7128 the address of the frame's local variables
7130 the program counter saved in it (the address of execution in the caller frame)
7132 which registers were saved in the frame
7135 @noindent The verbose description is useful when
7136 something has gone wrong that has made the stack format fail to fit
7137 the usual conventions.
7139 @item info frame @var{addr}
7140 @itemx info f @var{addr}
7141 Print a verbose description of the frame at address @var{addr}, without
7142 selecting that frame. The selected frame remains unchanged by this
7143 command. This requires the same kind of address (more than one for some
7144 architectures) that you specify in the @code{frame} command.
7145 @xref{Selection, ,Selecting a Frame}.
7149 Print the arguments of the selected frame, each on a separate line.
7153 Print the local variables of the selected frame, each on a separate
7154 line. These are all variables (declared either static or automatic)
7155 accessible at the point of execution of the selected frame.
7161 @chapter Examining Source Files
7163 @value{GDBN} can print parts of your program's source, since the debugging
7164 information recorded in the program tells @value{GDBN} what source files were
7165 used to build it. When your program stops, @value{GDBN} spontaneously prints
7166 the line where it stopped. Likewise, when you select a stack frame
7167 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7168 execution in that frame has stopped. You can print other portions of
7169 source files by explicit command.
7171 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7172 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7173 @value{GDBN} under @sc{gnu} Emacs}.
7176 * List:: Printing source lines
7177 * Specify Location:: How to specify code locations
7178 * Edit:: Editing source files
7179 * Search:: Searching source files
7180 * Source Path:: Specifying source directories
7181 * Machine Code:: Source and machine code
7185 @section Printing Source Lines
7188 @kindex l @r{(@code{list})}
7189 To print lines from a source file, use the @code{list} command
7190 (abbreviated @code{l}). By default, ten lines are printed.
7191 There are several ways to specify what part of the file you want to
7192 print; see @ref{Specify Location}, for the full list.
7194 Here are the forms of the @code{list} command most commonly used:
7197 @item list @var{linenum}
7198 Print lines centered around line number @var{linenum} in the
7199 current source file.
7201 @item list @var{function}
7202 Print lines centered around the beginning of function
7206 Print more lines. If the last lines printed were printed with a
7207 @code{list} command, this prints lines following the last lines
7208 printed; however, if the last line printed was a solitary line printed
7209 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7210 Stack}), this prints lines centered around that line.
7213 Print lines just before the lines last printed.
7216 @cindex @code{list}, how many lines to display
7217 By default, @value{GDBN} prints ten source lines with any of these forms of
7218 the @code{list} command. You can change this using @code{set listsize}:
7221 @kindex set listsize
7222 @item set listsize @var{count}
7223 @itemx set listsize unlimited
7224 Make the @code{list} command display @var{count} source lines (unless
7225 the @code{list} argument explicitly specifies some other number).
7226 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7228 @kindex show listsize
7230 Display the number of lines that @code{list} prints.
7233 Repeating a @code{list} command with @key{RET} discards the argument,
7234 so it is equivalent to typing just @code{list}. This is more useful
7235 than listing the same lines again. An exception is made for an
7236 argument of @samp{-}; that argument is preserved in repetition so that
7237 each repetition moves up in the source file.
7239 In general, the @code{list} command expects you to supply zero, one or two
7240 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7241 of writing them (@pxref{Specify Location}), but the effect is always
7242 to specify some source line.
7244 Here is a complete description of the possible arguments for @code{list}:
7247 @item list @var{linespec}
7248 Print lines centered around the line specified by @var{linespec}.
7250 @item list @var{first},@var{last}
7251 Print lines from @var{first} to @var{last}. Both arguments are
7252 linespecs. When a @code{list} command has two linespecs, and the
7253 source file of the second linespec is omitted, this refers to
7254 the same source file as the first linespec.
7256 @item list ,@var{last}
7257 Print lines ending with @var{last}.
7259 @item list @var{first},
7260 Print lines starting with @var{first}.
7263 Print lines just after the lines last printed.
7266 Print lines just before the lines last printed.
7269 As described in the preceding table.
7272 @node Specify Location
7273 @section Specifying a Location
7274 @cindex specifying location
7277 Several @value{GDBN} commands accept arguments that specify a location
7278 of your program's code. Since @value{GDBN} is a source-level
7279 debugger, a location usually specifies some line in the source code;
7280 for that reason, locations are also known as @dfn{linespecs}.
7282 Here are all the different ways of specifying a code location that
7283 @value{GDBN} understands:
7287 Specifies the line number @var{linenum} of the current source file.
7290 @itemx +@var{offset}
7291 Specifies the line @var{offset} lines before or after the @dfn{current
7292 line}. For the @code{list} command, the current line is the last one
7293 printed; for the breakpoint commands, this is the line at which
7294 execution stopped in the currently selected @dfn{stack frame}
7295 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7296 used as the second of the two linespecs in a @code{list} command,
7297 this specifies the line @var{offset} lines up or down from the first
7300 @item @var{filename}:@var{linenum}
7301 Specifies the line @var{linenum} in the source file @var{filename}.
7302 If @var{filename} is a relative file name, then it will match any
7303 source file name with the same trailing components. For example, if
7304 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7305 name of @file{/build/trunk/gcc/expr.c}, but not
7306 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7308 @item @var{function}
7309 Specifies the line that begins the body of the function @var{function}.
7310 For example, in C, this is the line with the open brace.
7312 @item @var{function}:@var{label}
7313 Specifies the line where @var{label} appears in @var{function}.
7315 @item @var{filename}:@var{function}
7316 Specifies the line that begins the body of the function @var{function}
7317 in the file @var{filename}. You only need the file name with a
7318 function name to avoid ambiguity when there are identically named
7319 functions in different source files.
7322 Specifies the line at which the label named @var{label} appears.
7323 @value{GDBN} searches for the label in the function corresponding to
7324 the currently selected stack frame. If there is no current selected
7325 stack frame (for instance, if the inferior is not running), then
7326 @value{GDBN} will not search for a label.
7328 @item *@var{address}
7329 Specifies the program address @var{address}. For line-oriented
7330 commands, such as @code{list} and @code{edit}, this specifies a source
7331 line that contains @var{address}. For @code{break} and other
7332 breakpoint oriented commands, this can be used to set breakpoints in
7333 parts of your program which do not have debugging information or
7336 Here @var{address} may be any expression valid in the current working
7337 language (@pxref{Languages, working language}) that specifies a code
7338 address. In addition, as a convenience, @value{GDBN} extends the
7339 semantics of expressions used in locations to cover the situations
7340 that frequently happen during debugging. Here are the various forms
7344 @item @var{expression}
7345 Any expression valid in the current working language.
7347 @item @var{funcaddr}
7348 An address of a function or procedure derived from its name. In C,
7349 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7350 simply the function's name @var{function} (and actually a special case
7351 of a valid expression). In Pascal and Modula-2, this is
7352 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7353 (although the Pascal form also works).
7355 This form specifies the address of the function's first instruction,
7356 before the stack frame and arguments have been set up.
7358 @item '@var{filename}'::@var{funcaddr}
7359 Like @var{funcaddr} above, but also specifies the name of the source
7360 file explicitly. This is useful if the name of the function does not
7361 specify the function unambiguously, e.g., if there are several
7362 functions with identical names in different source files.
7365 @cindex breakpoint at static probe point
7366 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7367 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7368 applications to embed static probes. @xref{Static Probe Points}, for more
7369 information on finding and using static probes. This form of linespec
7370 specifies the location of such a static probe.
7372 If @var{objfile} is given, only probes coming from that shared library
7373 or executable matching @var{objfile} as a regular expression are considered.
7374 If @var{provider} is given, then only probes from that provider are considered.
7375 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7376 each one of those probes.
7382 @section Editing Source Files
7383 @cindex editing source files
7386 @kindex e @r{(@code{edit})}
7387 To edit the lines in a source file, use the @code{edit} command.
7388 The editing program of your choice
7389 is invoked with the current line set to
7390 the active line in the program.
7391 Alternatively, there are several ways to specify what part of the file you
7392 want to print if you want to see other parts of the program:
7395 @item edit @var{location}
7396 Edit the source file specified by @code{location}. Editing starts at
7397 that @var{location}, e.g., at the specified source line of the
7398 specified file. @xref{Specify Location}, for all the possible forms
7399 of the @var{location} argument; here are the forms of the @code{edit}
7400 command most commonly used:
7403 @item edit @var{number}
7404 Edit the current source file with @var{number} as the active line number.
7406 @item edit @var{function}
7407 Edit the file containing @var{function} at the beginning of its definition.
7412 @subsection Choosing your Editor
7413 You can customize @value{GDBN} to use any editor you want
7415 The only restriction is that your editor (say @code{ex}), recognizes the
7416 following command-line syntax:
7418 ex +@var{number} file
7420 The optional numeric value +@var{number} specifies the number of the line in
7421 the file where to start editing.}.
7422 By default, it is @file{@value{EDITOR}}, but you can change this
7423 by setting the environment variable @code{EDITOR} before using
7424 @value{GDBN}. For example, to configure @value{GDBN} to use the
7425 @code{vi} editor, you could use these commands with the @code{sh} shell:
7431 or in the @code{csh} shell,
7433 setenv EDITOR /usr/bin/vi
7438 @section Searching Source Files
7439 @cindex searching source files
7441 There are two commands for searching through the current source file for a
7446 @kindex forward-search
7447 @kindex fo @r{(@code{forward-search})}
7448 @item forward-search @var{regexp}
7449 @itemx search @var{regexp}
7450 The command @samp{forward-search @var{regexp}} checks each line,
7451 starting with the one following the last line listed, for a match for
7452 @var{regexp}. It lists the line that is found. You can use the
7453 synonym @samp{search @var{regexp}} or abbreviate the command name as
7456 @kindex reverse-search
7457 @item reverse-search @var{regexp}
7458 The command @samp{reverse-search @var{regexp}} checks each line, starting
7459 with the one before the last line listed and going backward, for a match
7460 for @var{regexp}. It lists the line that is found. You can abbreviate
7461 this command as @code{rev}.
7465 @section Specifying Source Directories
7468 @cindex directories for source files
7469 Executable programs sometimes do not record the directories of the source
7470 files from which they were compiled, just the names. Even when they do,
7471 the directories could be moved between the compilation and your debugging
7472 session. @value{GDBN} has a list of directories to search for source files;
7473 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7474 it tries all the directories in the list, in the order they are present
7475 in the list, until it finds a file with the desired name.
7477 For example, suppose an executable references the file
7478 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7479 @file{/mnt/cross}. The file is first looked up literally; if this
7480 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7481 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7482 message is printed. @value{GDBN} does not look up the parts of the
7483 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7484 Likewise, the subdirectories of the source path are not searched: if
7485 the source path is @file{/mnt/cross}, and the binary refers to
7486 @file{foo.c}, @value{GDBN} would not find it under
7487 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7489 Plain file names, relative file names with leading directories, file
7490 names containing dots, etc.@: are all treated as described above; for
7491 instance, if the source path is @file{/mnt/cross}, and the source file
7492 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7493 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7494 that---@file{/mnt/cross/foo.c}.
7496 Note that the executable search path is @emph{not} used to locate the
7499 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7500 any information it has cached about where source files are found and where
7501 each line is in the file.
7505 When you start @value{GDBN}, its source path includes only @samp{cdir}
7506 and @samp{cwd}, in that order.
7507 To add other directories, use the @code{directory} command.
7509 The search path is used to find both program source files and @value{GDBN}
7510 script files (read using the @samp{-command} option and @samp{source} command).
7512 In addition to the source path, @value{GDBN} provides a set of commands
7513 that manage a list of source path substitution rules. A @dfn{substitution
7514 rule} specifies how to rewrite source directories stored in the program's
7515 debug information in case the sources were moved to a different
7516 directory between compilation and debugging. A rule is made of
7517 two strings, the first specifying what needs to be rewritten in
7518 the path, and the second specifying how it should be rewritten.
7519 In @ref{set substitute-path}, we name these two parts @var{from} and
7520 @var{to} respectively. @value{GDBN} does a simple string replacement
7521 of @var{from} with @var{to} at the start of the directory part of the
7522 source file name, and uses that result instead of the original file
7523 name to look up the sources.
7525 Using the previous example, suppose the @file{foo-1.0} tree has been
7526 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7527 @value{GDBN} to replace @file{/usr/src} in all source path names with
7528 @file{/mnt/cross}. The first lookup will then be
7529 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7530 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7531 substitution rule, use the @code{set substitute-path} command
7532 (@pxref{set substitute-path}).
7534 To avoid unexpected substitution results, a rule is applied only if the
7535 @var{from} part of the directory name ends at a directory separator.
7536 For instance, a rule substituting @file{/usr/source} into
7537 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7538 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7539 is applied only at the beginning of the directory name, this rule will
7540 not be applied to @file{/root/usr/source/baz.c} either.
7542 In many cases, you can achieve the same result using the @code{directory}
7543 command. However, @code{set substitute-path} can be more efficient in
7544 the case where the sources are organized in a complex tree with multiple
7545 subdirectories. With the @code{directory} command, you need to add each
7546 subdirectory of your project. If you moved the entire tree while
7547 preserving its internal organization, then @code{set substitute-path}
7548 allows you to direct the debugger to all the sources with one single
7551 @code{set substitute-path} is also more than just a shortcut command.
7552 The source path is only used if the file at the original location no
7553 longer exists. On the other hand, @code{set substitute-path} modifies
7554 the debugger behavior to look at the rewritten location instead. So, if
7555 for any reason a source file that is not relevant to your executable is
7556 located at the original location, a substitution rule is the only
7557 method available to point @value{GDBN} at the new location.
7559 @cindex @samp{--with-relocated-sources}
7560 @cindex default source path substitution
7561 You can configure a default source path substitution rule by
7562 configuring @value{GDBN} with the
7563 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7564 should be the name of a directory under @value{GDBN}'s configured
7565 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7566 directory names in debug information under @var{dir} will be adjusted
7567 automatically if the installed @value{GDBN} is moved to a new
7568 location. This is useful if @value{GDBN}, libraries or executables
7569 with debug information and corresponding source code are being moved
7573 @item directory @var{dirname} @dots{}
7574 @item dir @var{dirname} @dots{}
7575 Add directory @var{dirname} to the front of the source path. Several
7576 directory names may be given to this command, separated by @samp{:}
7577 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7578 part of absolute file names) or
7579 whitespace. You may specify a directory that is already in the source
7580 path; this moves it forward, so @value{GDBN} searches it sooner.
7584 @vindex $cdir@r{, convenience variable}
7585 @vindex $cwd@r{, convenience variable}
7586 @cindex compilation directory
7587 @cindex current directory
7588 @cindex working directory
7589 @cindex directory, current
7590 @cindex directory, compilation
7591 You can use the string @samp{$cdir} to refer to the compilation
7592 directory (if one is recorded), and @samp{$cwd} to refer to the current
7593 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7594 tracks the current working directory as it changes during your @value{GDBN}
7595 session, while the latter is immediately expanded to the current
7596 directory at the time you add an entry to the source path.
7599 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7601 @c RET-repeat for @code{directory} is explicitly disabled, but since
7602 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7604 @item set directories @var{path-list}
7605 @kindex set directories
7606 Set the source path to @var{path-list}.
7607 @samp{$cdir:$cwd} are added if missing.
7609 @item show directories
7610 @kindex show directories
7611 Print the source path: show which directories it contains.
7613 @anchor{set substitute-path}
7614 @item set substitute-path @var{from} @var{to}
7615 @kindex set substitute-path
7616 Define a source path substitution rule, and add it at the end of the
7617 current list of existing substitution rules. If a rule with the same
7618 @var{from} was already defined, then the old rule is also deleted.
7620 For example, if the file @file{/foo/bar/baz.c} was moved to
7621 @file{/mnt/cross/baz.c}, then the command
7624 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7628 will tell @value{GDBN} to replace @samp{/usr/src} with
7629 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7630 @file{baz.c} even though it was moved.
7632 In the case when more than one substitution rule have been defined,
7633 the rules are evaluated one by one in the order where they have been
7634 defined. The first one matching, if any, is selected to perform
7637 For instance, if we had entered the following commands:
7640 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7641 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7645 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7646 @file{/mnt/include/defs.h} by using the first rule. However, it would
7647 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7648 @file{/mnt/src/lib/foo.c}.
7651 @item unset substitute-path [path]
7652 @kindex unset substitute-path
7653 If a path is specified, search the current list of substitution rules
7654 for a rule that would rewrite that path. Delete that rule if found.
7655 A warning is emitted by the debugger if no rule could be found.
7657 If no path is specified, then all substitution rules are deleted.
7659 @item show substitute-path [path]
7660 @kindex show substitute-path
7661 If a path is specified, then print the source path substitution rule
7662 which would rewrite that path, if any.
7664 If no path is specified, then print all existing source path substitution
7669 If your source path is cluttered with directories that are no longer of
7670 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7671 versions of source. You can correct the situation as follows:
7675 Use @code{directory} with no argument to reset the source path to its default value.
7678 Use @code{directory} with suitable arguments to reinstall the
7679 directories you want in the source path. You can add all the
7680 directories in one command.
7684 @section Source and Machine Code
7685 @cindex source line and its code address
7687 You can use the command @code{info line} to map source lines to program
7688 addresses (and vice versa), and the command @code{disassemble} to display
7689 a range of addresses as machine instructions. You can use the command
7690 @code{set disassemble-next-line} to set whether to disassemble next
7691 source line when execution stops. When run under @sc{gnu} Emacs
7692 mode, the @code{info line} command causes the arrow to point to the
7693 line specified. Also, @code{info line} prints addresses in symbolic form as
7698 @item info line @var{linespec}
7699 Print the starting and ending addresses of the compiled code for
7700 source line @var{linespec}. You can specify source lines in any of
7701 the ways documented in @ref{Specify Location}.
7704 For example, we can use @code{info line} to discover the location of
7705 the object code for the first line of function
7706 @code{m4_changequote}:
7708 @c FIXME: I think this example should also show the addresses in
7709 @c symbolic form, as they usually would be displayed.
7711 (@value{GDBP}) info line m4_changequote
7712 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7716 @cindex code address and its source line
7717 We can also inquire (using @code{*@var{addr}} as the form for
7718 @var{linespec}) what source line covers a particular address:
7720 (@value{GDBP}) info line *0x63ff
7721 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7724 @cindex @code{$_} and @code{info line}
7725 @cindex @code{x} command, default address
7726 @kindex x@r{(examine), and} info line
7727 After @code{info line}, the default address for the @code{x} command
7728 is changed to the starting address of the line, so that @samp{x/i} is
7729 sufficient to begin examining the machine code (@pxref{Memory,
7730 ,Examining Memory}). Also, this address is saved as the value of the
7731 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7736 @cindex assembly instructions
7737 @cindex instructions, assembly
7738 @cindex machine instructions
7739 @cindex listing machine instructions
7741 @itemx disassemble /m
7742 @itemx disassemble /r
7743 This specialized command dumps a range of memory as machine
7744 instructions. It can also print mixed source+disassembly by specifying
7745 the @code{/m} modifier and print the raw instructions in hex as well as
7746 in symbolic form by specifying the @code{/r}.
7747 The default memory range is the function surrounding the
7748 program counter of the selected frame. A single argument to this
7749 command is a program counter value; @value{GDBN} dumps the function
7750 surrounding this value. When two arguments are given, they should
7751 be separated by a comma, possibly surrounded by whitespace. The
7752 arguments specify a range of addresses to dump, in one of two forms:
7755 @item @var{start},@var{end}
7756 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7757 @item @var{start},+@var{length}
7758 the addresses from @var{start} (inclusive) to
7759 @code{@var{start}+@var{length}} (exclusive).
7763 When 2 arguments are specified, the name of the function is also
7764 printed (since there could be several functions in the given range).
7766 The argument(s) can be any expression yielding a numeric value, such as
7767 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7769 If the range of memory being disassembled contains current program counter,
7770 the instruction at that location is shown with a @code{=>} marker.
7773 The following example shows the disassembly of a range of addresses of
7774 HP PA-RISC 2.0 code:
7777 (@value{GDBP}) disas 0x32c4, 0x32e4
7778 Dump of assembler code from 0x32c4 to 0x32e4:
7779 0x32c4 <main+204>: addil 0,dp
7780 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7781 0x32cc <main+212>: ldil 0x3000,r31
7782 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7783 0x32d4 <main+220>: ldo 0(r31),rp
7784 0x32d8 <main+224>: addil -0x800,dp
7785 0x32dc <main+228>: ldo 0x588(r1),r26
7786 0x32e0 <main+232>: ldil 0x3000,r31
7787 End of assembler dump.
7790 Here is an example showing mixed source+assembly for Intel x86, when the
7791 program is stopped just after function prologue:
7794 (@value{GDBP}) disas /m main
7795 Dump of assembler code for function main:
7797 0x08048330 <+0>: push %ebp
7798 0x08048331 <+1>: mov %esp,%ebp
7799 0x08048333 <+3>: sub $0x8,%esp
7800 0x08048336 <+6>: and $0xfffffff0,%esp
7801 0x08048339 <+9>: sub $0x10,%esp
7803 6 printf ("Hello.\n");
7804 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7805 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7809 0x08048348 <+24>: mov $0x0,%eax
7810 0x0804834d <+29>: leave
7811 0x0804834e <+30>: ret
7813 End of assembler dump.
7816 Here is another example showing raw instructions in hex for AMD x86-64,
7819 (gdb) disas /r 0x400281,+10
7820 Dump of assembler code from 0x400281 to 0x40028b:
7821 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7822 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7823 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7824 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7825 End of assembler dump.
7828 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7829 So, for example, if you want to disassemble function @code{bar}
7830 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7831 and not @samp{disassemble foo.c:bar}.
7833 Some architectures have more than one commonly-used set of instruction
7834 mnemonics or other syntax.
7836 For programs that were dynamically linked and use shared libraries,
7837 instructions that call functions or branch to locations in the shared
7838 libraries might show a seemingly bogus location---it's actually a
7839 location of the relocation table. On some architectures, @value{GDBN}
7840 might be able to resolve these to actual function names.
7843 @kindex set disassembly-flavor
7844 @cindex Intel disassembly flavor
7845 @cindex AT&T disassembly flavor
7846 @item set disassembly-flavor @var{instruction-set}
7847 Select the instruction set to use when disassembling the
7848 program via the @code{disassemble} or @code{x/i} commands.
7850 Currently this command is only defined for the Intel x86 family. You
7851 can set @var{instruction-set} to either @code{intel} or @code{att}.
7852 The default is @code{att}, the AT&T flavor used by default by Unix
7853 assemblers for x86-based targets.
7855 @kindex show disassembly-flavor
7856 @item show disassembly-flavor
7857 Show the current setting of the disassembly flavor.
7861 @kindex set disassemble-next-line
7862 @kindex show disassemble-next-line
7863 @item set disassemble-next-line
7864 @itemx show disassemble-next-line
7865 Control whether or not @value{GDBN} will disassemble the next source
7866 line or instruction when execution stops. If ON, @value{GDBN} will
7867 display disassembly of the next source line when execution of the
7868 program being debugged stops. This is @emph{in addition} to
7869 displaying the source line itself, which @value{GDBN} always does if
7870 possible. If the next source line cannot be displayed for some reason
7871 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7872 info in the debug info), @value{GDBN} will display disassembly of the
7873 next @emph{instruction} instead of showing the next source line. If
7874 AUTO, @value{GDBN} will display disassembly of next instruction only
7875 if the source line cannot be displayed. This setting causes
7876 @value{GDBN} to display some feedback when you step through a function
7877 with no line info or whose source file is unavailable. The default is
7878 OFF, which means never display the disassembly of the next line or
7884 @chapter Examining Data
7886 @cindex printing data
7887 @cindex examining data
7890 The usual way to examine data in your program is with the @code{print}
7891 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7892 evaluates and prints the value of an expression of the language your
7893 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7894 Different Languages}). It may also print the expression using a
7895 Python-based pretty-printer (@pxref{Pretty Printing}).
7898 @item print @var{expr}
7899 @itemx print /@var{f} @var{expr}
7900 @var{expr} is an expression (in the source language). By default the
7901 value of @var{expr} is printed in a format appropriate to its data type;
7902 you can choose a different format by specifying @samp{/@var{f}}, where
7903 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7907 @itemx print /@var{f}
7908 @cindex reprint the last value
7909 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7910 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7911 conveniently inspect the same value in an alternative format.
7914 A more low-level way of examining data is with the @code{x} command.
7915 It examines data in memory at a specified address and prints it in a
7916 specified format. @xref{Memory, ,Examining Memory}.
7918 If you are interested in information about types, or about how the
7919 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7920 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7923 @cindex exploring hierarchical data structures
7925 Another way of examining values of expressions and type information is
7926 through the Python extension command @code{explore} (available only if
7927 the @value{GDBN} build is configured with @code{--with-python}). It
7928 offers an interactive way to start at the highest level (or, the most
7929 abstract level) of the data type of an expression (or, the data type
7930 itself) and explore all the way down to leaf scalar values/fields
7931 embedded in the higher level data types.
7934 @item explore @var{arg}
7935 @var{arg} is either an expression (in the source language), or a type
7936 visible in the current context of the program being debugged.
7939 The working of the @code{explore} command can be illustrated with an
7940 example. If a data type @code{struct ComplexStruct} is defined in your
7950 struct ComplexStruct
7952 struct SimpleStruct *ss_p;
7958 followed by variable declarations as
7961 struct SimpleStruct ss = @{ 10, 1.11 @};
7962 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7966 then, the value of the variable @code{cs} can be explored using the
7967 @code{explore} command as follows.
7971 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7972 the following fields:
7974 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7975 arr = <Enter 1 to explore this field of type `int [10]'>
7977 Enter the field number of choice:
7981 Since the fields of @code{cs} are not scalar values, you are being
7982 prompted to chose the field you want to explore. Let's say you choose
7983 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7984 pointer, you will be asked if it is pointing to a single value. From
7985 the declaration of @code{cs} above, it is indeed pointing to a single
7986 value, hence you enter @code{y}. If you enter @code{n}, then you will
7987 be asked if it were pointing to an array of values, in which case this
7988 field will be explored as if it were an array.
7991 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7992 Continue exploring it as a pointer to a single value [y/n]: y
7993 The value of `*(cs.ss_p)' is a struct/class of type `struct
7994 SimpleStruct' with the following fields:
7996 i = 10 .. (Value of type `int')
7997 d = 1.1100000000000001 .. (Value of type `double')
7999 Press enter to return to parent value:
8003 If the field @code{arr} of @code{cs} was chosen for exploration by
8004 entering @code{1} earlier, then since it is as array, you will be
8005 prompted to enter the index of the element in the array that you want
8009 `cs.arr' is an array of `int'.
8010 Enter the index of the element you want to explore in `cs.arr': 5
8012 `(cs.arr)[5]' is a scalar value of type `int'.
8016 Press enter to return to parent value:
8019 In general, at any stage of exploration, you can go deeper towards the
8020 leaf values by responding to the prompts appropriately, or hit the
8021 return key to return to the enclosing data structure (the @i{higher}
8022 level data structure).
8024 Similar to exploring values, you can use the @code{explore} command to
8025 explore types. Instead of specifying a value (which is typically a
8026 variable name or an expression valid in the current context of the
8027 program being debugged), you specify a type name. If you consider the
8028 same example as above, your can explore the type
8029 @code{struct ComplexStruct} by passing the argument
8030 @code{struct ComplexStruct} to the @code{explore} command.
8033 (gdb) explore struct ComplexStruct
8037 By responding to the prompts appropriately in the subsequent interactive
8038 session, you can explore the type @code{struct ComplexStruct} in a
8039 manner similar to how the value @code{cs} was explored in the above
8042 The @code{explore} command also has two sub-commands,
8043 @code{explore value} and @code{explore type}. The former sub-command is
8044 a way to explicitly specify that value exploration of the argument is
8045 being invoked, while the latter is a way to explicitly specify that type
8046 exploration of the argument is being invoked.
8049 @item explore value @var{expr}
8050 @cindex explore value
8051 This sub-command of @code{explore} explores the value of the
8052 expression @var{expr} (if @var{expr} is an expression valid in the
8053 current context of the program being debugged). The behavior of this
8054 command is identical to that of the behavior of the @code{explore}
8055 command being passed the argument @var{expr}.
8057 @item explore type @var{arg}
8058 @cindex explore type
8059 This sub-command of @code{explore} explores the type of @var{arg} (if
8060 @var{arg} is a type visible in the current context of program being
8061 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8062 is an expression valid in the current context of the program being
8063 debugged). If @var{arg} is a type, then the behavior of this command is
8064 identical to that of the @code{explore} command being passed the
8065 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8066 this command will be identical to that of the @code{explore} command
8067 being passed the type of @var{arg} as the argument.
8071 * Expressions:: Expressions
8072 * Ambiguous Expressions:: Ambiguous Expressions
8073 * Variables:: Program variables
8074 * Arrays:: Artificial arrays
8075 * Output Formats:: Output formats
8076 * Memory:: Examining memory
8077 * Auto Display:: Automatic display
8078 * Print Settings:: Print settings
8079 * Pretty Printing:: Python pretty printing
8080 * Value History:: Value history
8081 * Convenience Vars:: Convenience variables
8082 * Convenience Funs:: Convenience functions
8083 * Registers:: Registers
8084 * Floating Point Hardware:: Floating point hardware
8085 * Vector Unit:: Vector Unit
8086 * OS Information:: Auxiliary data provided by operating system
8087 * Memory Region Attributes:: Memory region attributes
8088 * Dump/Restore Files:: Copy between memory and a file
8089 * Core File Generation:: Cause a program dump its core
8090 * Character Sets:: Debugging programs that use a different
8091 character set than GDB does
8092 * Caching Target Data:: Data caching for targets
8093 * Searching Memory:: Searching memory for a sequence of bytes
8097 @section Expressions
8100 @code{print} and many other @value{GDBN} commands accept an expression and
8101 compute its value. Any kind of constant, variable or operator defined
8102 by the programming language you are using is valid in an expression in
8103 @value{GDBN}. This includes conditional expressions, function calls,
8104 casts, and string constants. It also includes preprocessor macros, if
8105 you compiled your program to include this information; see
8108 @cindex arrays in expressions
8109 @value{GDBN} supports array constants in expressions input by
8110 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8111 you can use the command @code{print @{1, 2, 3@}} to create an array
8112 of three integers. If you pass an array to a function or assign it
8113 to a program variable, @value{GDBN} copies the array to memory that
8114 is @code{malloc}ed in the target program.
8116 Because C is so widespread, most of the expressions shown in examples in
8117 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8118 Languages}, for information on how to use expressions in other
8121 In this section, we discuss operators that you can use in @value{GDBN}
8122 expressions regardless of your programming language.
8124 @cindex casts, in expressions
8125 Casts are supported in all languages, not just in C, because it is so
8126 useful to cast a number into a pointer in order to examine a structure
8127 at that address in memory.
8128 @c FIXME: casts supported---Mod2 true?
8130 @value{GDBN} supports these operators, in addition to those common
8131 to programming languages:
8135 @samp{@@} is a binary operator for treating parts of memory as arrays.
8136 @xref{Arrays, ,Artificial Arrays}, for more information.
8139 @samp{::} allows you to specify a variable in terms of the file or
8140 function where it is defined. @xref{Variables, ,Program Variables}.
8142 @cindex @{@var{type}@}
8143 @cindex type casting memory
8144 @cindex memory, viewing as typed object
8145 @cindex casts, to view memory
8146 @item @{@var{type}@} @var{addr}
8147 Refers to an object of type @var{type} stored at address @var{addr} in
8148 memory. @var{addr} may be any expression whose value is an integer or
8149 pointer (but parentheses are required around binary operators, just as in
8150 a cast). This construct is allowed regardless of what kind of data is
8151 normally supposed to reside at @var{addr}.
8154 @node Ambiguous Expressions
8155 @section Ambiguous Expressions
8156 @cindex ambiguous expressions
8158 Expressions can sometimes contain some ambiguous elements. For instance,
8159 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8160 a single function name to be defined several times, for application in
8161 different contexts. This is called @dfn{overloading}. Another example
8162 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8163 templates and is typically instantiated several times, resulting in
8164 the same function name being defined in different contexts.
8166 In some cases and depending on the language, it is possible to adjust
8167 the expression to remove the ambiguity. For instance in C@t{++}, you
8168 can specify the signature of the function you want to break on, as in
8169 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8170 qualified name of your function often makes the expression unambiguous
8173 When an ambiguity that needs to be resolved is detected, the debugger
8174 has the capability to display a menu of numbered choices for each
8175 possibility, and then waits for the selection with the prompt @samp{>}.
8176 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8177 aborts the current command. If the command in which the expression was
8178 used allows more than one choice to be selected, the next option in the
8179 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8182 For example, the following session excerpt shows an attempt to set a
8183 breakpoint at the overloaded symbol @code{String::after}.
8184 We choose three particular definitions of that function name:
8186 @c FIXME! This is likely to change to show arg type lists, at least
8189 (@value{GDBP}) b String::after
8192 [2] file:String.cc; line number:867
8193 [3] file:String.cc; line number:860
8194 [4] file:String.cc; line number:875
8195 [5] file:String.cc; line number:853
8196 [6] file:String.cc; line number:846
8197 [7] file:String.cc; line number:735
8199 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8200 Breakpoint 2 at 0xb344: file String.cc, line 875.
8201 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8202 Multiple breakpoints were set.
8203 Use the "delete" command to delete unwanted
8210 @kindex set multiple-symbols
8211 @item set multiple-symbols @var{mode}
8212 @cindex multiple-symbols menu
8214 This option allows you to adjust the debugger behavior when an expression
8217 By default, @var{mode} is set to @code{all}. If the command with which
8218 the expression is used allows more than one choice, then @value{GDBN}
8219 automatically selects all possible choices. For instance, inserting
8220 a breakpoint on a function using an ambiguous name results in a breakpoint
8221 inserted on each possible match. However, if a unique choice must be made,
8222 then @value{GDBN} uses the menu to help you disambiguate the expression.
8223 For instance, printing the address of an overloaded function will result
8224 in the use of the menu.
8226 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8227 when an ambiguity is detected.
8229 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8230 an error due to the ambiguity and the command is aborted.
8232 @kindex show multiple-symbols
8233 @item show multiple-symbols
8234 Show the current value of the @code{multiple-symbols} setting.
8238 @section Program Variables
8240 The most common kind of expression to use is the name of a variable
8243 Variables in expressions are understood in the selected stack frame
8244 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8248 global (or file-static)
8255 visible according to the scope rules of the
8256 programming language from the point of execution in that frame
8259 @noindent This means that in the function
8274 you can examine and use the variable @code{a} whenever your program is
8275 executing within the function @code{foo}, but you can only use or
8276 examine the variable @code{b} while your program is executing inside
8277 the block where @code{b} is declared.
8279 @cindex variable name conflict
8280 There is an exception: you can refer to a variable or function whose
8281 scope is a single source file even if the current execution point is not
8282 in this file. But it is possible to have more than one such variable or
8283 function with the same name (in different source files). If that
8284 happens, referring to that name has unpredictable effects. If you wish,
8285 you can specify a static variable in a particular function or file by
8286 using the colon-colon (@code{::}) notation:
8288 @cindex colon-colon, context for variables/functions
8290 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8291 @cindex @code{::}, context for variables/functions
8294 @var{file}::@var{variable}
8295 @var{function}::@var{variable}
8299 Here @var{file} or @var{function} is the name of the context for the
8300 static @var{variable}. In the case of file names, you can use quotes to
8301 make sure @value{GDBN} parses the file name as a single word---for example,
8302 to print a global value of @code{x} defined in @file{f2.c}:
8305 (@value{GDBP}) p 'f2.c'::x
8308 The @code{::} notation is normally used for referring to
8309 static variables, since you typically disambiguate uses of local variables
8310 in functions by selecting the appropriate frame and using the
8311 simple name of the variable. However, you may also use this notation
8312 to refer to local variables in frames enclosing the selected frame:
8321 process (a); /* Stop here */
8332 For example, if there is a breakpoint at the commented line,
8333 here is what you might see
8334 when the program stops after executing the call @code{bar(0)}:
8339 (@value{GDBP}) p bar::a
8342 #2 0x080483d0 in foo (a=5) at foobar.c:12
8345 (@value{GDBP}) p bar::a
8349 @cindex C@t{++} scope resolution
8350 These uses of @samp{::} are very rarely in conflict with the very
8351 similar use of the same notation in C@t{++}. When they are in
8352 conflict, the C@t{++} meaning takes precedence; however, this can be
8353 overridden by quoting the file or function name with single quotes.
8355 For example, suppose the program is stopped in a method of a class
8356 that has a field named @code{includefile}, and there is also an
8357 include file named @file{includefile} that defines a variable,
8361 (@value{GDBP}) p includefile
8363 (@value{GDBP}) p includefile::some_global
8364 A syntax error in expression, near `'.
8365 (@value{GDBP}) p 'includefile'::some_global
8369 @cindex wrong values
8370 @cindex variable values, wrong
8371 @cindex function entry/exit, wrong values of variables
8372 @cindex optimized code, wrong values of variables
8374 @emph{Warning:} Occasionally, a local variable may appear to have the
8375 wrong value at certain points in a function---just after entry to a new
8376 scope, and just before exit.
8378 You may see this problem when you are stepping by machine instructions.
8379 This is because, on most machines, it takes more than one instruction to
8380 set up a stack frame (including local variable definitions); if you are
8381 stepping by machine instructions, variables may appear to have the wrong
8382 values until the stack frame is completely built. On exit, it usually
8383 also takes more than one machine instruction to destroy a stack frame;
8384 after you begin stepping through that group of instructions, local
8385 variable definitions may be gone.
8387 This may also happen when the compiler does significant optimizations.
8388 To be sure of always seeing accurate values, turn off all optimization
8391 @cindex ``No symbol "foo" in current context''
8392 Another possible effect of compiler optimizations is to optimize
8393 unused variables out of existence, or assign variables to registers (as
8394 opposed to memory addresses). Depending on the support for such cases
8395 offered by the debug info format used by the compiler, @value{GDBN}
8396 might not be able to display values for such local variables. If that
8397 happens, @value{GDBN} will print a message like this:
8400 No symbol "foo" in current context.
8403 To solve such problems, either recompile without optimizations, or use a
8404 different debug info format, if the compiler supports several such
8405 formats. @xref{Compilation}, for more information on choosing compiler
8406 options. @xref{C, ,C and C@t{++}}, for more information about debug
8407 info formats that are best suited to C@t{++} programs.
8409 If you ask to print an object whose contents are unknown to
8410 @value{GDBN}, e.g., because its data type is not completely specified
8411 by the debug information, @value{GDBN} will say @samp{<incomplete
8412 type>}. @xref{Symbols, incomplete type}, for more about this.
8414 If you append @kbd{@@entry} string to a function parameter name you get its
8415 value at the time the function got called. If the value is not available an
8416 error message is printed. Entry values are available only with some compilers.
8417 Entry values are normally also printed at the function parameter list according
8418 to @ref{set print entry-values}.
8421 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8427 (gdb) print i@@entry
8431 Strings are identified as arrays of @code{char} values without specified
8432 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8433 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8434 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8435 defines literal string type @code{"char"} as @code{char} without a sign.
8440 signed char var1[] = "A";
8443 You get during debugging
8448 $2 = @{65 'A', 0 '\0'@}
8452 @section Artificial Arrays
8454 @cindex artificial array
8456 @kindex @@@r{, referencing memory as an array}
8457 It is often useful to print out several successive objects of the
8458 same type in memory; a section of an array, or an array of
8459 dynamically determined size for which only a pointer exists in the
8462 You can do this by referring to a contiguous span of memory as an
8463 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8464 operand of @samp{@@} should be the first element of the desired array
8465 and be an individual object. The right operand should be the desired length
8466 of the array. The result is an array value whose elements are all of
8467 the type of the left argument. The first element is actually the left
8468 argument; the second element comes from bytes of memory immediately
8469 following those that hold the first element, and so on. Here is an
8470 example. If a program says
8473 int *array = (int *) malloc (len * sizeof (int));
8477 you can print the contents of @code{array} with
8483 The left operand of @samp{@@} must reside in memory. Array values made
8484 with @samp{@@} in this way behave just like other arrays in terms of
8485 subscripting, and are coerced to pointers when used in expressions.
8486 Artificial arrays most often appear in expressions via the value history
8487 (@pxref{Value History, ,Value History}), after printing one out.
8489 Another way to create an artificial array is to use a cast.
8490 This re-interprets a value as if it were an array.
8491 The value need not be in memory:
8493 (@value{GDBP}) p/x (short[2])0x12345678
8494 $1 = @{0x1234, 0x5678@}
8497 As a convenience, if you leave the array length out (as in
8498 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8499 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8501 (@value{GDBP}) p/x (short[])0x12345678
8502 $2 = @{0x1234, 0x5678@}
8505 Sometimes the artificial array mechanism is not quite enough; in
8506 moderately complex data structures, the elements of interest may not
8507 actually be adjacent---for example, if you are interested in the values
8508 of pointers in an array. One useful work-around in this situation is
8509 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8510 Variables}) as a counter in an expression that prints the first
8511 interesting value, and then repeat that expression via @key{RET}. For
8512 instance, suppose you have an array @code{dtab} of pointers to
8513 structures, and you are interested in the values of a field @code{fv}
8514 in each structure. Here is an example of what you might type:
8524 @node Output Formats
8525 @section Output Formats
8527 @cindex formatted output
8528 @cindex output formats
8529 By default, @value{GDBN} prints a value according to its data type. Sometimes
8530 this is not what you want. For example, you might want to print a number
8531 in hex, or a pointer in decimal. Or you might want to view data in memory
8532 at a certain address as a character string or as an instruction. To do
8533 these things, specify an @dfn{output format} when you print a value.
8535 The simplest use of output formats is to say how to print a value
8536 already computed. This is done by starting the arguments of the
8537 @code{print} command with a slash and a format letter. The format
8538 letters supported are:
8542 Regard the bits of the value as an integer, and print the integer in
8546 Print as integer in signed decimal.
8549 Print as integer in unsigned decimal.
8552 Print as integer in octal.
8555 Print as integer in binary. The letter @samp{t} stands for ``two''.
8556 @footnote{@samp{b} cannot be used because these format letters are also
8557 used with the @code{x} command, where @samp{b} stands for ``byte'';
8558 see @ref{Memory,,Examining Memory}.}
8561 @cindex unknown address, locating
8562 @cindex locate address
8563 Print as an address, both absolute in hexadecimal and as an offset from
8564 the nearest preceding symbol. You can use this format used to discover
8565 where (in what function) an unknown address is located:
8568 (@value{GDBP}) p/a 0x54320
8569 $3 = 0x54320 <_initialize_vx+396>
8573 The command @code{info symbol 0x54320} yields similar results.
8574 @xref{Symbols, info symbol}.
8577 Regard as an integer and print it as a character constant. This
8578 prints both the numerical value and its character representation. The
8579 character representation is replaced with the octal escape @samp{\nnn}
8580 for characters outside the 7-bit @sc{ascii} range.
8582 Without this format, @value{GDBN} displays @code{char},
8583 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8584 constants. Single-byte members of vectors are displayed as integer
8588 Regard the bits of the value as a floating point number and print
8589 using typical floating point syntax.
8592 @cindex printing strings
8593 @cindex printing byte arrays
8594 Regard as a string, if possible. With this format, pointers to single-byte
8595 data are displayed as null-terminated strings and arrays of single-byte data
8596 are displayed as fixed-length strings. Other values are displayed in their
8599 Without this format, @value{GDBN} displays pointers to and arrays of
8600 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8601 strings. Single-byte members of a vector are displayed as an integer
8605 Like @samp{x} formatting, the value is treated as an integer and
8606 printed as hexadecimal, but leading zeros are printed to pad the value
8607 to the size of the integer type.
8610 @cindex raw printing
8611 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8612 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8613 Printing}). This typically results in a higher-level display of the
8614 value's contents. The @samp{r} format bypasses any Python
8615 pretty-printer which might exist.
8618 For example, to print the program counter in hex (@pxref{Registers}), type
8625 Note that no space is required before the slash; this is because command
8626 names in @value{GDBN} cannot contain a slash.
8628 To reprint the last value in the value history with a different format,
8629 you can use the @code{print} command with just a format and no
8630 expression. For example, @samp{p/x} reprints the last value in hex.
8633 @section Examining Memory
8635 You can use the command @code{x} (for ``examine'') to examine memory in
8636 any of several formats, independently of your program's data types.
8638 @cindex examining memory
8640 @kindex x @r{(examine memory)}
8641 @item x/@var{nfu} @var{addr}
8644 Use the @code{x} command to examine memory.
8647 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8648 much memory to display and how to format it; @var{addr} is an
8649 expression giving the address where you want to start displaying memory.
8650 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8651 Several commands set convenient defaults for @var{addr}.
8654 @item @var{n}, the repeat count
8655 The repeat count is a decimal integer; the default is 1. It specifies
8656 how much memory (counting by units @var{u}) to display.
8657 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8660 @item @var{f}, the display format
8661 The display format is one of the formats used by @code{print}
8662 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8663 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8664 The default is @samp{x} (hexadecimal) initially. The default changes
8665 each time you use either @code{x} or @code{print}.
8667 @item @var{u}, the unit size
8668 The unit size is any of
8674 Halfwords (two bytes).
8676 Words (four bytes). This is the initial default.
8678 Giant words (eight bytes).
8681 Each time you specify a unit size with @code{x}, that size becomes the
8682 default unit the next time you use @code{x}. For the @samp{i} format,
8683 the unit size is ignored and is normally not written. For the @samp{s} format,
8684 the unit size defaults to @samp{b}, unless it is explicitly given.
8685 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8686 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8687 Note that the results depend on the programming language of the
8688 current compilation unit. If the language is C, the @samp{s}
8689 modifier will use the UTF-16 encoding while @samp{w} will use
8690 UTF-32. The encoding is set by the programming language and cannot
8693 @item @var{addr}, starting display address
8694 @var{addr} is the address where you want @value{GDBN} to begin displaying
8695 memory. The expression need not have a pointer value (though it may);
8696 it is always interpreted as an integer address of a byte of memory.
8697 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8698 @var{addr} is usually just after the last address examined---but several
8699 other commands also set the default address: @code{info breakpoints} (to
8700 the address of the last breakpoint listed), @code{info line} (to the
8701 starting address of a line), and @code{print} (if you use it to display
8702 a value from memory).
8705 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8706 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8707 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8708 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8709 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8711 Since the letters indicating unit sizes are all distinct from the
8712 letters specifying output formats, you do not have to remember whether
8713 unit size or format comes first; either order works. The output
8714 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8715 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8717 Even though the unit size @var{u} is ignored for the formats @samp{s}
8718 and @samp{i}, you might still want to use a count @var{n}; for example,
8719 @samp{3i} specifies that you want to see three machine instructions,
8720 including any operands. For convenience, especially when used with
8721 the @code{display} command, the @samp{i} format also prints branch delay
8722 slot instructions, if any, beyond the count specified, which immediately
8723 follow the last instruction that is within the count. The command
8724 @code{disassemble} gives an alternative way of inspecting machine
8725 instructions; see @ref{Machine Code,,Source and Machine Code}.
8727 All the defaults for the arguments to @code{x} are designed to make it
8728 easy to continue scanning memory with minimal specifications each time
8729 you use @code{x}. For example, after you have inspected three machine
8730 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8731 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8732 the repeat count @var{n} is used again; the other arguments default as
8733 for successive uses of @code{x}.
8735 When examining machine instructions, the instruction at current program
8736 counter is shown with a @code{=>} marker. For example:
8739 (@value{GDBP}) x/5i $pc-6
8740 0x804837f <main+11>: mov %esp,%ebp
8741 0x8048381 <main+13>: push %ecx
8742 0x8048382 <main+14>: sub $0x4,%esp
8743 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8744 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8747 @cindex @code{$_}, @code{$__}, and value history
8748 The addresses and contents printed by the @code{x} command are not saved
8749 in the value history because there is often too much of them and they
8750 would get in the way. Instead, @value{GDBN} makes these values available for
8751 subsequent use in expressions as values of the convenience variables
8752 @code{$_} and @code{$__}. After an @code{x} command, the last address
8753 examined is available for use in expressions in the convenience variable
8754 @code{$_}. The contents of that address, as examined, are available in
8755 the convenience variable @code{$__}.
8757 If the @code{x} command has a repeat count, the address and contents saved
8758 are from the last memory unit printed; this is not the same as the last
8759 address printed if several units were printed on the last line of output.
8761 @cindex remote memory comparison
8762 @cindex verify remote memory image
8763 When you are debugging a program running on a remote target machine
8764 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8765 remote machine's memory against the executable file you downloaded to
8766 the target. The @code{compare-sections} command is provided for such
8770 @kindex compare-sections
8771 @item compare-sections @r{[}@var{section-name}@r{]}
8772 Compare the data of a loadable section @var{section-name} in the
8773 executable file of the program being debugged with the same section in
8774 the remote machine's memory, and report any mismatches. With no
8775 arguments, compares all loadable sections. This command's
8776 availability depends on the target's support for the @code{"qCRC"}
8781 @section Automatic Display
8782 @cindex automatic display
8783 @cindex display of expressions
8785 If you find that you want to print the value of an expression frequently
8786 (to see how it changes), you might want to add it to the @dfn{automatic
8787 display list} so that @value{GDBN} prints its value each time your program stops.
8788 Each expression added to the list is given a number to identify it;
8789 to remove an expression from the list, you specify that number.
8790 The automatic display looks like this:
8794 3: bar[5] = (struct hack *) 0x3804
8798 This display shows item numbers, expressions and their current values. As with
8799 displays you request manually using @code{x} or @code{print}, you can
8800 specify the output format you prefer; in fact, @code{display} decides
8801 whether to use @code{print} or @code{x} depending your format
8802 specification---it uses @code{x} if you specify either the @samp{i}
8803 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8807 @item display @var{expr}
8808 Add the expression @var{expr} to the list of expressions to display
8809 each time your program stops. @xref{Expressions, ,Expressions}.
8811 @code{display} does not repeat if you press @key{RET} again after using it.
8813 @item display/@var{fmt} @var{expr}
8814 For @var{fmt} specifying only a display format and not a size or
8815 count, add the expression @var{expr} to the auto-display list but
8816 arrange to display it each time in the specified format @var{fmt}.
8817 @xref{Output Formats,,Output Formats}.
8819 @item display/@var{fmt} @var{addr}
8820 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8821 number of units, add the expression @var{addr} as a memory address to
8822 be examined each time your program stops. Examining means in effect
8823 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8826 For example, @samp{display/i $pc} can be helpful, to see the machine
8827 instruction about to be executed each time execution stops (@samp{$pc}
8828 is a common name for the program counter; @pxref{Registers, ,Registers}).
8831 @kindex delete display
8833 @item undisplay @var{dnums}@dots{}
8834 @itemx delete display @var{dnums}@dots{}
8835 Remove items from the list of expressions to display. Specify the
8836 numbers of the displays that you want affected with the command
8837 argument @var{dnums}. It can be a single display number, one of the
8838 numbers shown in the first field of the @samp{info display} display;
8839 or it could be a range of display numbers, as in @code{2-4}.
8841 @code{undisplay} does not repeat if you press @key{RET} after using it.
8842 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8844 @kindex disable display
8845 @item disable display @var{dnums}@dots{}
8846 Disable the display of item numbers @var{dnums}. A disabled display
8847 item is not printed automatically, but is not forgotten. It may be
8848 enabled again later. Specify the numbers of the displays that you
8849 want affected with the command argument @var{dnums}. It can be a
8850 single display number, one of the numbers shown in the first field of
8851 the @samp{info display} display; or it could be a range of display
8852 numbers, as in @code{2-4}.
8854 @kindex enable display
8855 @item enable display @var{dnums}@dots{}
8856 Enable display of item numbers @var{dnums}. It becomes effective once
8857 again in auto display of its expression, until you specify otherwise.
8858 Specify the numbers of the displays that you want affected with the
8859 command argument @var{dnums}. It can be a single display number, one
8860 of the numbers shown in the first field of the @samp{info display}
8861 display; or it could be a range of display numbers, as in @code{2-4}.
8864 Display the current values of the expressions on the list, just as is
8865 done when your program stops.
8867 @kindex info display
8869 Print the list of expressions previously set up to display
8870 automatically, each one with its item number, but without showing the
8871 values. This includes disabled expressions, which are marked as such.
8872 It also includes expressions which would not be displayed right now
8873 because they refer to automatic variables not currently available.
8876 @cindex display disabled out of scope
8877 If a display expression refers to local variables, then it does not make
8878 sense outside the lexical context for which it was set up. Such an
8879 expression is disabled when execution enters a context where one of its
8880 variables is not defined. For example, if you give the command
8881 @code{display last_char} while inside a function with an argument
8882 @code{last_char}, @value{GDBN} displays this argument while your program
8883 continues to stop inside that function. When it stops elsewhere---where
8884 there is no variable @code{last_char}---the display is disabled
8885 automatically. The next time your program stops where @code{last_char}
8886 is meaningful, you can enable the display expression once again.
8888 @node Print Settings
8889 @section Print Settings
8891 @cindex format options
8892 @cindex print settings
8893 @value{GDBN} provides the following ways to control how arrays, structures,
8894 and symbols are printed.
8897 These settings are useful for debugging programs in any language:
8901 @item set print address
8902 @itemx set print address on
8903 @cindex print/don't print memory addresses
8904 @value{GDBN} prints memory addresses showing the location of stack
8905 traces, structure values, pointer values, breakpoints, and so forth,
8906 even when it also displays the contents of those addresses. The default
8907 is @code{on}. For example, this is what a stack frame display looks like with
8908 @code{set print address on}:
8913 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8915 530 if (lquote != def_lquote)
8919 @item set print address off
8920 Do not print addresses when displaying their contents. For example,
8921 this is the same stack frame displayed with @code{set print address off}:
8925 (@value{GDBP}) set print addr off
8927 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8928 530 if (lquote != def_lquote)
8932 You can use @samp{set print address off} to eliminate all machine
8933 dependent displays from the @value{GDBN} interface. For example, with
8934 @code{print address off}, you should get the same text for backtraces on
8935 all machines---whether or not they involve pointer arguments.
8938 @item show print address
8939 Show whether or not addresses are to be printed.
8942 When @value{GDBN} prints a symbolic address, it normally prints the
8943 closest earlier symbol plus an offset. If that symbol does not uniquely
8944 identify the address (for example, it is a name whose scope is a single
8945 source file), you may need to clarify. One way to do this is with
8946 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8947 you can set @value{GDBN} to print the source file and line number when
8948 it prints a symbolic address:
8951 @item set print symbol-filename on
8952 @cindex source file and line of a symbol
8953 @cindex symbol, source file and line
8954 Tell @value{GDBN} to print the source file name and line number of a
8955 symbol in the symbolic form of an address.
8957 @item set print symbol-filename off
8958 Do not print source file name and line number of a symbol. This is the
8961 @item show print symbol-filename
8962 Show whether or not @value{GDBN} will print the source file name and
8963 line number of a symbol in the symbolic form of an address.
8966 Another situation where it is helpful to show symbol filenames and line
8967 numbers is when disassembling code; @value{GDBN} shows you the line
8968 number and source file that corresponds to each instruction.
8970 Also, you may wish to see the symbolic form only if the address being
8971 printed is reasonably close to the closest earlier symbol:
8974 @item set print max-symbolic-offset @var{max-offset}
8975 @itemx set print max-symbolic-offset unlimited
8976 @cindex maximum value for offset of closest symbol
8977 Tell @value{GDBN} to only display the symbolic form of an address if the
8978 offset between the closest earlier symbol and the address is less than
8979 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8980 to always print the symbolic form of an address if any symbol precedes
8981 it. Zero is equivalent to @code{unlimited}.
8983 @item show print max-symbolic-offset
8984 Ask how large the maximum offset is that @value{GDBN} prints in a
8988 @cindex wild pointer, interpreting
8989 @cindex pointer, finding referent
8990 If you have a pointer and you are not sure where it points, try
8991 @samp{set print symbol-filename on}. Then you can determine the name
8992 and source file location of the variable where it points, using
8993 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8994 For example, here @value{GDBN} shows that a variable @code{ptt} points
8995 at another variable @code{t}, defined in @file{hi2.c}:
8998 (@value{GDBP}) set print symbol-filename on
8999 (@value{GDBP}) p/a ptt
9000 $4 = 0xe008 <t in hi2.c>
9004 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9005 does not show the symbol name and filename of the referent, even with
9006 the appropriate @code{set print} options turned on.
9009 You can also enable @samp{/a}-like formatting all the time using
9010 @samp{set print symbol on}:
9013 @item set print symbol on
9014 Tell @value{GDBN} to print the symbol corresponding to an address, if
9017 @item set print symbol off
9018 Tell @value{GDBN} not to print the symbol corresponding to an
9019 address. In this mode, @value{GDBN} will still print the symbol
9020 corresponding to pointers to functions. This is the default.
9022 @item show print symbol
9023 Show whether @value{GDBN} will display the symbol corresponding to an
9027 Other settings control how different kinds of objects are printed:
9030 @item set print array
9031 @itemx set print array on
9032 @cindex pretty print arrays
9033 Pretty print arrays. This format is more convenient to read,
9034 but uses more space. The default is off.
9036 @item set print array off
9037 Return to compressed format for arrays.
9039 @item show print array
9040 Show whether compressed or pretty format is selected for displaying
9043 @cindex print array indexes
9044 @item set print array-indexes
9045 @itemx set print array-indexes on
9046 Print the index of each element when displaying arrays. May be more
9047 convenient to locate a given element in the array or quickly find the
9048 index of a given element in that printed array. The default is off.
9050 @item set print array-indexes off
9051 Stop printing element indexes when displaying arrays.
9053 @item show print array-indexes
9054 Show whether the index of each element is printed when displaying
9057 @item set print elements @var{number-of-elements}
9058 @itemx set print elements unlimited
9059 @cindex number of array elements to print
9060 @cindex limit on number of printed array elements
9061 Set a limit on how many elements of an array @value{GDBN} will print.
9062 If @value{GDBN} is printing a large array, it stops printing after it has
9063 printed the number of elements set by the @code{set print elements} command.
9064 This limit also applies to the display of strings.
9065 When @value{GDBN} starts, this limit is set to 200.
9066 Setting @var{number-of-elements} to @code{unlimited} or zero means
9067 that the number of elements to print is unlimited.
9069 @item show print elements
9070 Display the number of elements of a large array that @value{GDBN} will print.
9071 If the number is 0, then the printing is unlimited.
9073 @item set print frame-arguments @var{value}
9074 @kindex set print frame-arguments
9075 @cindex printing frame argument values
9076 @cindex print all frame argument values
9077 @cindex print frame argument values for scalars only
9078 @cindex do not print frame argument values
9079 This command allows to control how the values of arguments are printed
9080 when the debugger prints a frame (@pxref{Frames}). The possible
9085 The values of all arguments are printed.
9088 Print the value of an argument only if it is a scalar. The value of more
9089 complex arguments such as arrays, structures, unions, etc, is replaced
9090 by @code{@dots{}}. This is the default. Here is an example where
9091 only scalar arguments are shown:
9094 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9099 None of the argument values are printed. Instead, the value of each argument
9100 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9103 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9108 By default, only scalar arguments are printed. This command can be used
9109 to configure the debugger to print the value of all arguments, regardless
9110 of their type. However, it is often advantageous to not print the value
9111 of more complex parameters. For instance, it reduces the amount of
9112 information printed in each frame, making the backtrace more readable.
9113 Also, it improves performance when displaying Ada frames, because
9114 the computation of large arguments can sometimes be CPU-intensive,
9115 especially in large applications. Setting @code{print frame-arguments}
9116 to @code{scalars} (the default) or @code{none} avoids this computation,
9117 thus speeding up the display of each Ada frame.
9119 @item show print frame-arguments
9120 Show how the value of arguments should be displayed when printing a frame.
9122 @item set print raw frame-arguments on
9123 Print frame arguments in raw, non pretty-printed, form.
9125 @item set print raw frame-arguments off
9126 Print frame arguments in pretty-printed form, if there is a pretty-printer
9127 for the value (@pxref{Pretty Printing}),
9128 otherwise print the value in raw form.
9129 This is the default.
9131 @item show print raw frame-arguments
9132 Show whether to print frame arguments in raw form.
9134 @anchor{set print entry-values}
9135 @item set print entry-values @var{value}
9136 @kindex set print entry-values
9137 Set printing of frame argument values at function entry. In some cases
9138 @value{GDBN} can determine the value of function argument which was passed by
9139 the function caller, even if the value was modified inside the called function
9140 and therefore is different. With optimized code, the current value could be
9141 unavailable, but the entry value may still be known.
9143 The default value is @code{default} (see below for its description). Older
9144 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9145 this feature will behave in the @code{default} setting the same way as with the
9148 This functionality is currently supported only by DWARF 2 debugging format and
9149 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9150 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9153 The @var{value} parameter can be one of the following:
9157 Print only actual parameter values, never print values from function entry
9161 #0 different (val=6)
9162 #0 lost (val=<optimized out>)
9164 #0 invalid (val=<optimized out>)
9168 Print only parameter values from function entry point. The actual parameter
9169 values are never printed.
9171 #0 equal (val@@entry=5)
9172 #0 different (val@@entry=5)
9173 #0 lost (val@@entry=5)
9174 #0 born (val@@entry=<optimized out>)
9175 #0 invalid (val@@entry=<optimized out>)
9179 Print only parameter values from function entry point. If value from function
9180 entry point is not known while the actual value is known, print the actual
9181 value for such parameter.
9183 #0 equal (val@@entry=5)
9184 #0 different (val@@entry=5)
9185 #0 lost (val@@entry=5)
9187 #0 invalid (val@@entry=<optimized out>)
9191 Print actual parameter values. If actual parameter value is not known while
9192 value from function entry point is known, print the entry point value for such
9196 #0 different (val=6)
9197 #0 lost (val@@entry=5)
9199 #0 invalid (val=<optimized out>)
9203 Always print both the actual parameter value and its value from function entry
9204 point, even if values of one or both are not available due to compiler
9207 #0 equal (val=5, val@@entry=5)
9208 #0 different (val=6, val@@entry=5)
9209 #0 lost (val=<optimized out>, val@@entry=5)
9210 #0 born (val=10, val@@entry=<optimized out>)
9211 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9215 Print the actual parameter value if it is known and also its value from
9216 function entry point if it is known. If neither is known, print for the actual
9217 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9218 values are known and identical, print the shortened
9219 @code{param=param@@entry=VALUE} notation.
9221 #0 equal (val=val@@entry=5)
9222 #0 different (val=6, val@@entry=5)
9223 #0 lost (val@@entry=5)
9225 #0 invalid (val=<optimized out>)
9229 Always print the actual parameter value. Print also its value from function
9230 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9231 if both values are known and identical, print the shortened
9232 @code{param=param@@entry=VALUE} notation.
9234 #0 equal (val=val@@entry=5)
9235 #0 different (val=6, val@@entry=5)
9236 #0 lost (val=<optimized out>, val@@entry=5)
9238 #0 invalid (val=<optimized out>)
9242 For analysis messages on possible failures of frame argument values at function
9243 entry resolution see @ref{set debug entry-values}.
9245 @item show print entry-values
9246 Show the method being used for printing of frame argument values at function
9249 @item set print repeats @var{number-of-repeats}
9250 @itemx set print repeats unlimited
9251 @cindex repeated array elements
9252 Set the threshold for suppressing display of repeated array
9253 elements. When the number of consecutive identical elements of an
9254 array exceeds the threshold, @value{GDBN} prints the string
9255 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9256 identical repetitions, instead of displaying the identical elements
9257 themselves. Setting the threshold to @code{unlimited} or zero will
9258 cause all elements to be individually printed. The default threshold
9261 @item show print repeats
9262 Display the current threshold for printing repeated identical
9265 @item set print null-stop
9266 @cindex @sc{null} elements in arrays
9267 Cause @value{GDBN} to stop printing the characters of an array when the first
9268 @sc{null} is encountered. This is useful when large arrays actually
9269 contain only short strings.
9272 @item show print null-stop
9273 Show whether @value{GDBN} stops printing an array on the first
9274 @sc{null} character.
9276 @item set print pretty on
9277 @cindex print structures in indented form
9278 @cindex indentation in structure display
9279 Cause @value{GDBN} to print structures in an indented format with one member
9280 per line, like this:
9295 @item set print pretty off
9296 Cause @value{GDBN} to print structures in a compact format, like this:
9300 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9301 meat = 0x54 "Pork"@}
9306 This is the default format.
9308 @item show print pretty
9309 Show which format @value{GDBN} is using to print structures.
9311 @item set print sevenbit-strings on
9312 @cindex eight-bit characters in strings
9313 @cindex octal escapes in strings
9314 Print using only seven-bit characters; if this option is set,
9315 @value{GDBN} displays any eight-bit characters (in strings or
9316 character values) using the notation @code{\}@var{nnn}. This setting is
9317 best if you are working in English (@sc{ascii}) and you use the
9318 high-order bit of characters as a marker or ``meta'' bit.
9320 @item set print sevenbit-strings off
9321 Print full eight-bit characters. This allows the use of more
9322 international character sets, and is the default.
9324 @item show print sevenbit-strings
9325 Show whether or not @value{GDBN} is printing only seven-bit characters.
9327 @item set print union on
9328 @cindex unions in structures, printing
9329 Tell @value{GDBN} to print unions which are contained in structures
9330 and other unions. This is the default setting.
9332 @item set print union off
9333 Tell @value{GDBN} not to print unions which are contained in
9334 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9337 @item show print union
9338 Ask @value{GDBN} whether or not it will print unions which are contained in
9339 structures and other unions.
9341 For example, given the declarations
9344 typedef enum @{Tree, Bug@} Species;
9345 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9346 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9357 struct thing foo = @{Tree, @{Acorn@}@};
9361 with @code{set print union on} in effect @samp{p foo} would print
9364 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9368 and with @code{set print union off} in effect it would print
9371 $1 = @{it = Tree, form = @{...@}@}
9375 @code{set print union} affects programs written in C-like languages
9381 These settings are of interest when debugging C@t{++} programs:
9384 @cindex demangling C@t{++} names
9385 @item set print demangle
9386 @itemx set print demangle on
9387 Print C@t{++} names in their source form rather than in the encoded
9388 (``mangled'') form passed to the assembler and linker for type-safe
9389 linkage. The default is on.
9391 @item show print demangle
9392 Show whether C@t{++} names are printed in mangled or demangled form.
9394 @item set print asm-demangle
9395 @itemx set print asm-demangle on
9396 Print C@t{++} names in their source form rather than their mangled form, even
9397 in assembler code printouts such as instruction disassemblies.
9400 @item show print asm-demangle
9401 Show whether C@t{++} names in assembly listings are printed in mangled
9404 @cindex C@t{++} symbol decoding style
9405 @cindex symbol decoding style, C@t{++}
9406 @kindex set demangle-style
9407 @item set demangle-style @var{style}
9408 Choose among several encoding schemes used by different compilers to
9409 represent C@t{++} names. The choices for @var{style} are currently:
9413 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9414 This is the default.
9417 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9420 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9423 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9426 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9427 @strong{Warning:} this setting alone is not sufficient to allow
9428 debugging @code{cfront}-generated executables. @value{GDBN} would
9429 require further enhancement to permit that.
9432 If you omit @var{style}, you will see a list of possible formats.
9434 @item show demangle-style
9435 Display the encoding style currently in use for decoding C@t{++} symbols.
9437 @item set print object
9438 @itemx set print object on
9439 @cindex derived type of an object, printing
9440 @cindex display derived types
9441 When displaying a pointer to an object, identify the @emph{actual}
9442 (derived) type of the object rather than the @emph{declared} type, using
9443 the virtual function table. Note that the virtual function table is
9444 required---this feature can only work for objects that have run-time
9445 type identification; a single virtual method in the object's declared
9446 type is sufficient. Note that this setting is also taken into account when
9447 working with variable objects via MI (@pxref{GDB/MI}).
9449 @item set print object off
9450 Display only the declared type of objects, without reference to the
9451 virtual function table. This is the default setting.
9453 @item show print object
9454 Show whether actual, or declared, object types are displayed.
9456 @item set print static-members
9457 @itemx set print static-members on
9458 @cindex static members of C@t{++} objects
9459 Print static members when displaying a C@t{++} object. The default is on.
9461 @item set print static-members off
9462 Do not print static members when displaying a C@t{++} object.
9464 @item show print static-members
9465 Show whether C@t{++} static members are printed or not.
9467 @item set print pascal_static-members
9468 @itemx set print pascal_static-members on
9469 @cindex static members of Pascal objects
9470 @cindex Pascal objects, static members display
9471 Print static members when displaying a Pascal object. The default is on.
9473 @item set print pascal_static-members off
9474 Do not print static members when displaying a Pascal object.
9476 @item show print pascal_static-members
9477 Show whether Pascal static members are printed or not.
9479 @c These don't work with HP ANSI C++ yet.
9480 @item set print vtbl
9481 @itemx set print vtbl on
9482 @cindex pretty print C@t{++} virtual function tables
9483 @cindex virtual functions (C@t{++}) display
9484 @cindex VTBL display
9485 Pretty print C@t{++} virtual function tables. The default is off.
9486 (The @code{vtbl} commands do not work on programs compiled with the HP
9487 ANSI C@t{++} compiler (@code{aCC}).)
9489 @item set print vtbl off
9490 Do not pretty print C@t{++} virtual function tables.
9492 @item show print vtbl
9493 Show whether C@t{++} virtual function tables are pretty printed, or not.
9496 @node Pretty Printing
9497 @section Pretty Printing
9499 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9500 Python code. It greatly simplifies the display of complex objects. This
9501 mechanism works for both MI and the CLI.
9504 * Pretty-Printer Introduction:: Introduction to pretty-printers
9505 * Pretty-Printer Example:: An example pretty-printer
9506 * Pretty-Printer Commands:: Pretty-printer commands
9509 @node Pretty-Printer Introduction
9510 @subsection Pretty-Printer Introduction
9512 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9513 registered for the value. If there is then @value{GDBN} invokes the
9514 pretty-printer to print the value. Otherwise the value is printed normally.
9516 Pretty-printers are normally named. This makes them easy to manage.
9517 The @samp{info pretty-printer} command will list all the installed
9518 pretty-printers with their names.
9519 If a pretty-printer can handle multiple data types, then its
9520 @dfn{subprinters} are the printers for the individual data types.
9521 Each such subprinter has its own name.
9522 The format of the name is @var{printer-name};@var{subprinter-name}.
9524 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9525 Typically they are automatically loaded and registered when the corresponding
9526 debug information is loaded, thus making them available without having to
9527 do anything special.
9529 There are three places where a pretty-printer can be registered.
9533 Pretty-printers registered globally are available when debugging
9537 Pretty-printers registered with a program space are available only
9538 when debugging that program.
9539 @xref{Progspaces In Python}, for more details on program spaces in Python.
9542 Pretty-printers registered with an objfile are loaded and unloaded
9543 with the corresponding objfile (e.g., shared library).
9544 @xref{Objfiles In Python}, for more details on objfiles in Python.
9547 @xref{Selecting Pretty-Printers}, for further information on how
9548 pretty-printers are selected,
9550 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9553 @node Pretty-Printer Example
9554 @subsection Pretty-Printer Example
9556 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9559 (@value{GDBP}) print s
9561 static npos = 4294967295,
9563 <std::allocator<char>> = @{
9564 <__gnu_cxx::new_allocator<char>> = @{
9565 <No data fields>@}, <No data fields>
9567 members of std::basic_string<char, std::char_traits<char>,
9568 std::allocator<char> >::_Alloc_hider:
9569 _M_p = 0x804a014 "abcd"
9574 With a pretty-printer for @code{std::string} only the contents are printed:
9577 (@value{GDBP}) print s
9581 @node Pretty-Printer Commands
9582 @subsection Pretty-Printer Commands
9583 @cindex pretty-printer commands
9586 @kindex info pretty-printer
9587 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9588 Print the list of installed pretty-printers.
9589 This includes disabled pretty-printers, which are marked as such.
9591 @var{object-regexp} is a regular expression matching the objects
9592 whose pretty-printers to list.
9593 Objects can be @code{global}, the program space's file
9594 (@pxref{Progspaces In Python}),
9595 and the object files within that program space (@pxref{Objfiles In Python}).
9596 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9597 looks up a printer from these three objects.
9599 @var{name-regexp} is a regular expression matching the name of the printers
9602 @kindex disable pretty-printer
9603 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9604 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9605 A disabled pretty-printer is not forgotten, it may be enabled again later.
9607 @kindex enable pretty-printer
9608 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9609 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9614 Suppose we have three pretty-printers installed: one from library1.so
9615 named @code{foo} that prints objects of type @code{foo}, and
9616 another from library2.so named @code{bar} that prints two types of objects,
9617 @code{bar1} and @code{bar2}.
9620 (gdb) info pretty-printer
9627 (gdb) info pretty-printer library2
9632 (gdb) disable pretty-printer library1
9634 2 of 3 printers enabled
9635 (gdb) info pretty-printer
9642 (gdb) disable pretty-printer library2 bar:bar1
9644 1 of 3 printers enabled
9645 (gdb) info pretty-printer library2
9652 (gdb) disable pretty-printer library2 bar
9654 0 of 3 printers enabled
9655 (gdb) info pretty-printer library2
9664 Note that for @code{bar} the entire printer can be disabled,
9665 as can each individual subprinter.
9668 @section Value History
9670 @cindex value history
9671 @cindex history of values printed by @value{GDBN}
9672 Values printed by the @code{print} command are saved in the @value{GDBN}
9673 @dfn{value history}. This allows you to refer to them in other expressions.
9674 Values are kept until the symbol table is re-read or discarded
9675 (for example with the @code{file} or @code{symbol-file} commands).
9676 When the symbol table changes, the value history is discarded,
9677 since the values may contain pointers back to the types defined in the
9682 @cindex history number
9683 The values printed are given @dfn{history numbers} by which you can
9684 refer to them. These are successive integers starting with one.
9685 @code{print} shows you the history number assigned to a value by
9686 printing @samp{$@var{num} = } before the value; here @var{num} is the
9689 To refer to any previous value, use @samp{$} followed by the value's
9690 history number. The way @code{print} labels its output is designed to
9691 remind you of this. Just @code{$} refers to the most recent value in
9692 the history, and @code{$$} refers to the value before that.
9693 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9694 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9695 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9697 For example, suppose you have just printed a pointer to a structure and
9698 want to see the contents of the structure. It suffices to type
9704 If you have a chain of structures where the component @code{next} points
9705 to the next one, you can print the contents of the next one with this:
9712 You can print successive links in the chain by repeating this
9713 command---which you can do by just typing @key{RET}.
9715 Note that the history records values, not expressions. If the value of
9716 @code{x} is 4 and you type these commands:
9724 then the value recorded in the value history by the @code{print} command
9725 remains 4 even though the value of @code{x} has changed.
9730 Print the last ten values in the value history, with their item numbers.
9731 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9732 values} does not change the history.
9734 @item show values @var{n}
9735 Print ten history values centered on history item number @var{n}.
9738 Print ten history values just after the values last printed. If no more
9739 values are available, @code{show values +} produces no display.
9742 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9743 same effect as @samp{show values +}.
9745 @node Convenience Vars
9746 @section Convenience Variables
9748 @cindex convenience variables
9749 @cindex user-defined variables
9750 @value{GDBN} provides @dfn{convenience variables} that you can use within
9751 @value{GDBN} to hold on to a value and refer to it later. These variables
9752 exist entirely within @value{GDBN}; they are not part of your program, and
9753 setting a convenience variable has no direct effect on further execution
9754 of your program. That is why you can use them freely.
9756 Convenience variables are prefixed with @samp{$}. Any name preceded by
9757 @samp{$} can be used for a convenience variable, unless it is one of
9758 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9759 (Value history references, in contrast, are @emph{numbers} preceded
9760 by @samp{$}. @xref{Value History, ,Value History}.)
9762 You can save a value in a convenience variable with an assignment
9763 expression, just as you would set a variable in your program.
9767 set $foo = *object_ptr
9771 would save in @code{$foo} the value contained in the object pointed to by
9774 Using a convenience variable for the first time creates it, but its
9775 value is @code{void} until you assign a new value. You can alter the
9776 value with another assignment at any time.
9778 Convenience variables have no fixed types. You can assign a convenience
9779 variable any type of value, including structures and arrays, even if
9780 that variable already has a value of a different type. The convenience
9781 variable, when used as an expression, has the type of its current value.
9784 @kindex show convenience
9785 @cindex show all user variables and functions
9786 @item show convenience
9787 Print a list of convenience variables used so far, and their values,
9788 as well as a list of the convenience functions.
9789 Abbreviated @code{show conv}.
9791 @kindex init-if-undefined
9792 @cindex convenience variables, initializing
9793 @item init-if-undefined $@var{variable} = @var{expression}
9794 Set a convenience variable if it has not already been set. This is useful
9795 for user-defined commands that keep some state. It is similar, in concept,
9796 to using local static variables with initializers in C (except that
9797 convenience variables are global). It can also be used to allow users to
9798 override default values used in a command script.
9800 If the variable is already defined then the expression is not evaluated so
9801 any side-effects do not occur.
9804 One of the ways to use a convenience variable is as a counter to be
9805 incremented or a pointer to be advanced. For example, to print
9806 a field from successive elements of an array of structures:
9810 print bar[$i++]->contents
9814 Repeat that command by typing @key{RET}.
9816 Some convenience variables are created automatically by @value{GDBN} and given
9817 values likely to be useful.
9820 @vindex $_@r{, convenience variable}
9822 The variable @code{$_} is automatically set by the @code{x} command to
9823 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9824 commands which provide a default address for @code{x} to examine also
9825 set @code{$_} to that address; these commands include @code{info line}
9826 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9827 except when set by the @code{x} command, in which case it is a pointer
9828 to the type of @code{$__}.
9830 @vindex $__@r{, convenience variable}
9832 The variable @code{$__} is automatically set by the @code{x} command
9833 to the value found in the last address examined. Its type is chosen
9834 to match the format in which the data was printed.
9837 @vindex $_exitcode@r{, convenience variable}
9838 When the program being debugged terminates normally, @value{GDBN}
9839 automatically sets this variable to the exit code of the program, and
9840 resets @code{$_exitsignal} to @code{void}.
9843 @vindex $_exitsignal@r{, convenience variable}
9844 When the program being debugged dies due to an uncaught signal,
9845 @value{GDBN} automatically sets this variable to that signal's number,
9846 and resets @code{$_exitcode} to @code{void}.
9848 To distinguish between whether the program being debugged has exited
9849 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
9850 @code{$_exitsignal} is not @code{void}), the convenience function
9851 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
9852 Functions}). For example, considering the following source code:
9858 main (int argc, char *argv[])
9865 A valid way of telling whether the program being debugged has exited
9866 or signalled would be:
9869 (@value{GDBP}) define has_exited_or_signalled
9870 Type commands for definition of ``has_exited_or_signalled''.
9871 End with a line saying just ``end''.
9872 >if $_isvoid ($_exitsignal)
9873 >echo The program has exited\n
9875 >echo The program has signalled\n
9881 Program terminated with signal SIGALRM, Alarm clock.
9882 The program no longer exists.
9883 (@value{GDBP}) has_exited_or_signalled
9884 The program has signalled
9887 As can be seen, @value{GDBN} correctly informs that the program being
9888 debugged has signalled, since it calls @code{raise} and raises a
9889 @code{SIGALRM} signal. If the program being debugged had not called
9890 @code{raise}, then @value{GDBN} would report a normal exit:
9893 (@value{GDBP}) has_exited_or_signalled
9894 The program has exited
9898 The variable @code{$_exception} is set to the exception object being
9899 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9902 @itemx $_probe_arg0@dots{}$_probe_arg11
9903 Arguments to a static probe. @xref{Static Probe Points}.
9906 @vindex $_sdata@r{, inspect, convenience variable}
9907 The variable @code{$_sdata} contains extra collected static tracepoint
9908 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9909 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9910 if extra static tracepoint data has not been collected.
9913 @vindex $_siginfo@r{, convenience variable}
9914 The variable @code{$_siginfo} contains extra signal information
9915 (@pxref{extra signal information}). Note that @code{$_siginfo}
9916 could be empty, if the application has not yet received any signals.
9917 For example, it will be empty before you execute the @code{run} command.
9920 @vindex $_tlb@r{, convenience variable}
9921 The variable @code{$_tlb} is automatically set when debugging
9922 applications running on MS-Windows in native mode or connected to
9923 gdbserver that supports the @code{qGetTIBAddr} request.
9924 @xref{General Query Packets}.
9925 This variable contains the address of the thread information block.
9929 On HP-UX systems, if you refer to a function or variable name that
9930 begins with a dollar sign, @value{GDBN} searches for a user or system
9931 name first, before it searches for a convenience variable.
9933 @node Convenience Funs
9934 @section Convenience Functions
9936 @cindex convenience functions
9937 @value{GDBN} also supplies some @dfn{convenience functions}. These
9938 have a syntax similar to convenience variables. A convenience
9939 function can be used in an expression just like an ordinary function;
9940 however, a convenience function is implemented internally to
9943 These functions do not require @value{GDBN} to be configured with
9944 @code{Python} support, which means that they are always available.
9948 @item $_isvoid (@var{expr})
9949 @findex $_isvoid@r{, convenience function}
9950 Return one if the expression @var{expr} is @code{void}. Otherwise it
9953 A @code{void} expression is an expression where the type of the result
9954 is @code{void}. For example, you can examine a convenience variable
9955 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9959 (@value{GDBP}) print $_exitcode
9961 (@value{GDBP}) print $_isvoid ($_exitcode)
9964 Starting program: ./a.out
9965 [Inferior 1 (process 29572) exited normally]
9966 (@value{GDBP}) print $_exitcode
9968 (@value{GDBP}) print $_isvoid ($_exitcode)
9972 In the example above, we used @code{$_isvoid} to check whether
9973 @code{$_exitcode} is @code{void} before and after the execution of the
9974 program being debugged. Before the execution there is no exit code to
9975 be examined, therefore @code{$_exitcode} is @code{void}. After the
9976 execution the program being debugged returned zero, therefore
9977 @code{$_exitcode} is zero, which means that it is not @code{void}
9980 The @code{void} expression can also be a call of a function from the
9981 program being debugged. For example, given the following function:
9990 The result of calling it inside @value{GDBN} is @code{void}:
9993 (@value{GDBP}) print foo ()
9995 (@value{GDBP}) print $_isvoid (foo ())
9997 (@value{GDBP}) set $v = foo ()
9998 (@value{GDBP}) print $v
10000 (@value{GDBP}) print $_isvoid ($v)
10006 These functions require @value{GDBN} to be configured with
10007 @code{Python} support.
10011 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10012 @findex $_memeq@r{, convenience function}
10013 Returns one if the @var{length} bytes at the addresses given by
10014 @var{buf1} and @var{buf2} are equal.
10015 Otherwise it returns zero.
10017 @item $_regex(@var{str}, @var{regex})
10018 @findex $_regex@r{, convenience function}
10019 Returns one if the string @var{str} matches the regular expression
10020 @var{regex}. Otherwise it returns zero.
10021 The syntax of the regular expression is that specified by @code{Python}'s
10022 regular expression support.
10024 @item $_streq(@var{str1}, @var{str2})
10025 @findex $_streq@r{, convenience function}
10026 Returns one if the strings @var{str1} and @var{str2} are equal.
10027 Otherwise it returns zero.
10029 @item $_strlen(@var{str})
10030 @findex $_strlen@r{, convenience function}
10031 Returns the length of string @var{str}.
10035 @value{GDBN} provides the ability to list and get help on
10036 convenience functions.
10039 @item help function
10040 @kindex help function
10041 @cindex show all convenience functions
10042 Print a list of all convenience functions.
10049 You can refer to machine register contents, in expressions, as variables
10050 with names starting with @samp{$}. The names of registers are different
10051 for each machine; use @code{info registers} to see the names used on
10055 @kindex info registers
10056 @item info registers
10057 Print the names and values of all registers except floating-point
10058 and vector registers (in the selected stack frame).
10060 @kindex info all-registers
10061 @cindex floating point registers
10062 @item info all-registers
10063 Print the names and values of all registers, including floating-point
10064 and vector registers (in the selected stack frame).
10066 @item info registers @var{regname} @dots{}
10067 Print the @dfn{relativized} value of each specified register @var{regname}.
10068 As discussed in detail below, register values are normally relative to
10069 the selected stack frame. @var{regname} may be any register name valid on
10070 the machine you are using, with or without the initial @samp{$}.
10073 @cindex stack pointer register
10074 @cindex program counter register
10075 @cindex process status register
10076 @cindex frame pointer register
10077 @cindex standard registers
10078 @value{GDBN} has four ``standard'' register names that are available (in
10079 expressions) on most machines---whenever they do not conflict with an
10080 architecture's canonical mnemonics for registers. The register names
10081 @code{$pc} and @code{$sp} are used for the program counter register and
10082 the stack pointer. @code{$fp} is used for a register that contains a
10083 pointer to the current stack frame, and @code{$ps} is used for a
10084 register that contains the processor status. For example,
10085 you could print the program counter in hex with
10092 or print the instruction to be executed next with
10099 or add four to the stack pointer@footnote{This is a way of removing
10100 one word from the stack, on machines where stacks grow downward in
10101 memory (most machines, nowadays). This assumes that the innermost
10102 stack frame is selected; setting @code{$sp} is not allowed when other
10103 stack frames are selected. To pop entire frames off the stack,
10104 regardless of machine architecture, use @code{return};
10105 see @ref{Returning, ,Returning from a Function}.} with
10111 Whenever possible, these four standard register names are available on
10112 your machine even though the machine has different canonical mnemonics,
10113 so long as there is no conflict. The @code{info registers} command
10114 shows the canonical names. For example, on the SPARC, @code{info
10115 registers} displays the processor status register as @code{$psr} but you
10116 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10117 is an alias for the @sc{eflags} register.
10119 @value{GDBN} always considers the contents of an ordinary register as an
10120 integer when the register is examined in this way. Some machines have
10121 special registers which can hold nothing but floating point; these
10122 registers are considered to have floating point values. There is no way
10123 to refer to the contents of an ordinary register as floating point value
10124 (although you can @emph{print} it as a floating point value with
10125 @samp{print/f $@var{regname}}).
10127 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10128 means that the data format in which the register contents are saved by
10129 the operating system is not the same one that your program normally
10130 sees. For example, the registers of the 68881 floating point
10131 coprocessor are always saved in ``extended'' (raw) format, but all C
10132 programs expect to work with ``double'' (virtual) format. In such
10133 cases, @value{GDBN} normally works with the virtual format only (the format
10134 that makes sense for your program), but the @code{info registers} command
10135 prints the data in both formats.
10137 @cindex SSE registers (x86)
10138 @cindex MMX registers (x86)
10139 Some machines have special registers whose contents can be interpreted
10140 in several different ways. For example, modern x86-based machines
10141 have SSE and MMX registers that can hold several values packed
10142 together in several different formats. @value{GDBN} refers to such
10143 registers in @code{struct} notation:
10146 (@value{GDBP}) print $xmm1
10148 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10149 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10150 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10151 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10152 v4_int32 = @{0, 20657912, 11, 13@},
10153 v2_int64 = @{88725056443645952, 55834574859@},
10154 uint128 = 0x0000000d0000000b013b36f800000000
10159 To set values of such registers, you need to tell @value{GDBN} which
10160 view of the register you wish to change, as if you were assigning
10161 value to a @code{struct} member:
10164 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10167 Normally, register values are relative to the selected stack frame
10168 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10169 value that the register would contain if all stack frames farther in
10170 were exited and their saved registers restored. In order to see the
10171 true contents of hardware registers, you must select the innermost
10172 frame (with @samp{frame 0}).
10174 @cindex caller-saved registers
10175 @cindex call-clobbered registers
10176 @cindex volatile registers
10177 @cindex <not saved> values
10178 Usually ABIs reserve some registers as not needed to be saved by the
10179 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10180 registers). It may therefore not be possible for @value{GDBN} to know
10181 the value a register had before the call (in other words, in the outer
10182 frame), if the register value has since been changed by the callee.
10183 @value{GDBN} tries to deduce where the inner frame saved
10184 (``callee-saved'') registers, from the debug info, unwind info, or the
10185 machine code generated by your compiler. If some register is not
10186 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10187 its own knowledge of the ABI, or because the debug/unwind info
10188 explicitly says the register's value is undefined), @value{GDBN}
10189 displays @w{@samp{<not saved>}} as the register's value. With targets
10190 that @value{GDBN} has no knowledge of the register saving convention,
10191 if a register was not saved by the callee, then its value and location
10192 in the outer frame are assumed to be the same of the inner frame.
10193 This is usually harmless, because if the register is call-clobbered,
10194 the caller either does not care what is in the register after the
10195 call, or has code to restore the value that it does care about. Note,
10196 however, that if you change such a register in the outer frame, you
10197 may also be affecting the inner frame. Also, the more ``outer'' the
10198 frame is you're looking at, the more likely a call-clobbered
10199 register's value is to be wrong, in the sense that it doesn't actually
10200 represent the value the register had just before the call.
10202 @node Floating Point Hardware
10203 @section Floating Point Hardware
10204 @cindex floating point
10206 Depending on the configuration, @value{GDBN} may be able to give
10207 you more information about the status of the floating point hardware.
10212 Display hardware-dependent information about the floating
10213 point unit. The exact contents and layout vary depending on the
10214 floating point chip. Currently, @samp{info float} is supported on
10215 the ARM and x86 machines.
10219 @section Vector Unit
10220 @cindex vector unit
10222 Depending on the configuration, @value{GDBN} may be able to give you
10223 more information about the status of the vector unit.
10226 @kindex info vector
10228 Display information about the vector unit. The exact contents and
10229 layout vary depending on the hardware.
10232 @node OS Information
10233 @section Operating System Auxiliary Information
10234 @cindex OS information
10236 @value{GDBN} provides interfaces to useful OS facilities that can help
10237 you debug your program.
10239 @cindex auxiliary vector
10240 @cindex vector, auxiliary
10241 Some operating systems supply an @dfn{auxiliary vector} to programs at
10242 startup. This is akin to the arguments and environment that you
10243 specify for a program, but contains a system-dependent variety of
10244 binary values that tell system libraries important details about the
10245 hardware, operating system, and process. Each value's purpose is
10246 identified by an integer tag; the meanings are well-known but system-specific.
10247 Depending on the configuration and operating system facilities,
10248 @value{GDBN} may be able to show you this information. For remote
10249 targets, this functionality may further depend on the remote stub's
10250 support of the @samp{qXfer:auxv:read} packet, see
10251 @ref{qXfer auxiliary vector read}.
10256 Display the auxiliary vector of the inferior, which can be either a
10257 live process or a core dump file. @value{GDBN} prints each tag value
10258 numerically, and also shows names and text descriptions for recognized
10259 tags. Some values in the vector are numbers, some bit masks, and some
10260 pointers to strings or other data. @value{GDBN} displays each value in the
10261 most appropriate form for a recognized tag, and in hexadecimal for
10262 an unrecognized tag.
10265 On some targets, @value{GDBN} can access operating system-specific
10266 information and show it to you. The types of information available
10267 will differ depending on the type of operating system running on the
10268 target. The mechanism used to fetch the data is described in
10269 @ref{Operating System Information}. For remote targets, this
10270 functionality depends on the remote stub's support of the
10271 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10275 @item info os @var{infotype}
10277 Display OS information of the requested type.
10279 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10281 @anchor{linux info os infotypes}
10283 @kindex info os processes
10285 Display the list of processes on the target. For each process,
10286 @value{GDBN} prints the process identifier, the name of the user, the
10287 command corresponding to the process, and the list of processor cores
10288 that the process is currently running on. (To understand what these
10289 properties mean, for this and the following info types, please consult
10290 the general @sc{gnu}/Linux documentation.)
10292 @kindex info os procgroups
10294 Display the list of process groups on the target. For each process,
10295 @value{GDBN} prints the identifier of the process group that it belongs
10296 to, the command corresponding to the process group leader, the process
10297 identifier, and the command line of the process. The list is sorted
10298 first by the process group identifier, then by the process identifier,
10299 so that processes belonging to the same process group are grouped together
10300 and the process group leader is listed first.
10302 @kindex info os threads
10304 Display the list of threads running on the target. For each thread,
10305 @value{GDBN} prints the identifier of the process that the thread
10306 belongs to, the command of the process, the thread identifier, and the
10307 processor core that it is currently running on. The main thread of a
10308 process is not listed.
10310 @kindex info os files
10312 Display the list of open file descriptors on the target. For each
10313 file descriptor, @value{GDBN} prints the identifier of the process
10314 owning the descriptor, the command of the owning process, the value
10315 of the descriptor, and the target of the descriptor.
10317 @kindex info os sockets
10319 Display the list of Internet-domain sockets on the target. For each
10320 socket, @value{GDBN} prints the address and port of the local and
10321 remote endpoints, the current state of the connection, the creator of
10322 the socket, the IP address family of the socket, and the type of the
10325 @kindex info os shm
10327 Display the list of all System V shared-memory regions on the target.
10328 For each shared-memory region, @value{GDBN} prints the region key,
10329 the shared-memory identifier, the access permissions, the size of the
10330 region, the process that created the region, the process that last
10331 attached to or detached from the region, the current number of live
10332 attaches to the region, and the times at which the region was last
10333 attached to, detach from, and changed.
10335 @kindex info os semaphores
10337 Display the list of all System V semaphore sets on the target. For each
10338 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10339 set identifier, the access permissions, the number of semaphores in the
10340 set, the user and group of the owner and creator of the semaphore set,
10341 and the times at which the semaphore set was operated upon and changed.
10343 @kindex info os msg
10345 Display the list of all System V message queues on the target. For each
10346 message queue, @value{GDBN} prints the message queue key, the message
10347 queue identifier, the access permissions, the current number of bytes
10348 on the queue, the current number of messages on the queue, the processes
10349 that last sent and received a message on the queue, the user and group
10350 of the owner and creator of the message queue, the times at which a
10351 message was last sent and received on the queue, and the time at which
10352 the message queue was last changed.
10354 @kindex info os modules
10356 Display the list of all loaded kernel modules on the target. For each
10357 module, @value{GDBN} prints the module name, the size of the module in
10358 bytes, the number of times the module is used, the dependencies of the
10359 module, the status of the module, and the address of the loaded module
10364 If @var{infotype} is omitted, then list the possible values for
10365 @var{infotype} and the kind of OS information available for each
10366 @var{infotype}. If the target does not return a list of possible
10367 types, this command will report an error.
10370 @node Memory Region Attributes
10371 @section Memory Region Attributes
10372 @cindex memory region attributes
10374 @dfn{Memory region attributes} allow you to describe special handling
10375 required by regions of your target's memory. @value{GDBN} uses
10376 attributes to determine whether to allow certain types of memory
10377 accesses; whether to use specific width accesses; and whether to cache
10378 target memory. By default the description of memory regions is
10379 fetched from the target (if the current target supports this), but the
10380 user can override the fetched regions.
10382 Defined memory regions can be individually enabled and disabled. When a
10383 memory region is disabled, @value{GDBN} uses the default attributes when
10384 accessing memory in that region. Similarly, if no memory regions have
10385 been defined, @value{GDBN} uses the default attributes when accessing
10388 When a memory region is defined, it is given a number to identify it;
10389 to enable, disable, or remove a memory region, you specify that number.
10393 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10394 Define a memory region bounded by @var{lower} and @var{upper} with
10395 attributes @var{attributes}@dots{}, and add it to the list of regions
10396 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10397 case: it is treated as the target's maximum memory address.
10398 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10401 Discard any user changes to the memory regions and use target-supplied
10402 regions, if available, or no regions if the target does not support.
10405 @item delete mem @var{nums}@dots{}
10406 Remove memory regions @var{nums}@dots{} from the list of regions
10407 monitored by @value{GDBN}.
10409 @kindex disable mem
10410 @item disable mem @var{nums}@dots{}
10411 Disable monitoring of memory regions @var{nums}@dots{}.
10412 A disabled memory region is not forgotten.
10413 It may be enabled again later.
10416 @item enable mem @var{nums}@dots{}
10417 Enable monitoring of memory regions @var{nums}@dots{}.
10421 Print a table of all defined memory regions, with the following columns
10425 @item Memory Region Number
10426 @item Enabled or Disabled.
10427 Enabled memory regions are marked with @samp{y}.
10428 Disabled memory regions are marked with @samp{n}.
10431 The address defining the inclusive lower bound of the memory region.
10434 The address defining the exclusive upper bound of the memory region.
10437 The list of attributes set for this memory region.
10442 @subsection Attributes
10444 @subsubsection Memory Access Mode
10445 The access mode attributes set whether @value{GDBN} may make read or
10446 write accesses to a memory region.
10448 While these attributes prevent @value{GDBN} from performing invalid
10449 memory accesses, they do nothing to prevent the target system, I/O DMA,
10450 etc.@: from accessing memory.
10454 Memory is read only.
10456 Memory is write only.
10458 Memory is read/write. This is the default.
10461 @subsubsection Memory Access Size
10462 The access size attribute tells @value{GDBN} to use specific sized
10463 accesses in the memory region. Often memory mapped device registers
10464 require specific sized accesses. If no access size attribute is
10465 specified, @value{GDBN} may use accesses of any size.
10469 Use 8 bit memory accesses.
10471 Use 16 bit memory accesses.
10473 Use 32 bit memory accesses.
10475 Use 64 bit memory accesses.
10478 @c @subsubsection Hardware/Software Breakpoints
10479 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10480 @c will use hardware or software breakpoints for the internal breakpoints
10481 @c used by the step, next, finish, until, etc. commands.
10485 @c Always use hardware breakpoints
10486 @c @item swbreak (default)
10489 @subsubsection Data Cache
10490 The data cache attributes set whether @value{GDBN} will cache target
10491 memory. While this generally improves performance by reducing debug
10492 protocol overhead, it can lead to incorrect results because @value{GDBN}
10493 does not know about volatile variables or memory mapped device
10498 Enable @value{GDBN} to cache target memory.
10500 Disable @value{GDBN} from caching target memory. This is the default.
10503 @subsection Memory Access Checking
10504 @value{GDBN} can be instructed to refuse accesses to memory that is
10505 not explicitly described. This can be useful if accessing such
10506 regions has undesired effects for a specific target, or to provide
10507 better error checking. The following commands control this behaviour.
10510 @kindex set mem inaccessible-by-default
10511 @item set mem inaccessible-by-default [on|off]
10512 If @code{on} is specified, make @value{GDBN} treat memory not
10513 explicitly described by the memory ranges as non-existent and refuse accesses
10514 to such memory. The checks are only performed if there's at least one
10515 memory range defined. If @code{off} is specified, make @value{GDBN}
10516 treat the memory not explicitly described by the memory ranges as RAM.
10517 The default value is @code{on}.
10518 @kindex show mem inaccessible-by-default
10519 @item show mem inaccessible-by-default
10520 Show the current handling of accesses to unknown memory.
10524 @c @subsubsection Memory Write Verification
10525 @c The memory write verification attributes set whether @value{GDBN}
10526 @c will re-reads data after each write to verify the write was successful.
10530 @c @item noverify (default)
10533 @node Dump/Restore Files
10534 @section Copy Between Memory and a File
10535 @cindex dump/restore files
10536 @cindex append data to a file
10537 @cindex dump data to a file
10538 @cindex restore data from a file
10540 You can use the commands @code{dump}, @code{append}, and
10541 @code{restore} to copy data between target memory and a file. The
10542 @code{dump} and @code{append} commands write data to a file, and the
10543 @code{restore} command reads data from a file back into the inferior's
10544 memory. Files may be in binary, Motorola S-record, Intel hex, or
10545 Tektronix Hex format; however, @value{GDBN} can only append to binary
10551 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10552 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10553 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10554 or the value of @var{expr}, to @var{filename} in the given format.
10556 The @var{format} parameter may be any one of:
10563 Motorola S-record format.
10565 Tektronix Hex format.
10568 @value{GDBN} uses the same definitions of these formats as the
10569 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10570 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10574 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10575 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10576 Append the contents of memory from @var{start_addr} to @var{end_addr},
10577 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10578 (@value{GDBN} can only append data to files in raw binary form.)
10581 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10582 Restore the contents of file @var{filename} into memory. The
10583 @code{restore} command can automatically recognize any known @sc{bfd}
10584 file format, except for raw binary. To restore a raw binary file you
10585 must specify the optional keyword @code{binary} after the filename.
10587 If @var{bias} is non-zero, its value will be added to the addresses
10588 contained in the file. Binary files always start at address zero, so
10589 they will be restored at address @var{bias}. Other bfd files have
10590 a built-in location; they will be restored at offset @var{bias}
10591 from that location.
10593 If @var{start} and/or @var{end} are non-zero, then only data between
10594 file offset @var{start} and file offset @var{end} will be restored.
10595 These offsets are relative to the addresses in the file, before
10596 the @var{bias} argument is applied.
10600 @node Core File Generation
10601 @section How to Produce a Core File from Your Program
10602 @cindex dump core from inferior
10604 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10605 image of a running process and its process status (register values
10606 etc.). Its primary use is post-mortem debugging of a program that
10607 crashed while it ran outside a debugger. A program that crashes
10608 automatically produces a core file, unless this feature is disabled by
10609 the user. @xref{Files}, for information on invoking @value{GDBN} in
10610 the post-mortem debugging mode.
10612 Occasionally, you may wish to produce a core file of the program you
10613 are debugging in order to preserve a snapshot of its state.
10614 @value{GDBN} has a special command for that.
10618 @kindex generate-core-file
10619 @item generate-core-file [@var{file}]
10620 @itemx gcore [@var{file}]
10621 Produce a core dump of the inferior process. The optional argument
10622 @var{file} specifies the file name where to put the core dump. If not
10623 specified, the file name defaults to @file{core.@var{pid}}, where
10624 @var{pid} is the inferior process ID.
10626 Note that this command is implemented only for some systems (as of
10627 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10630 @node Character Sets
10631 @section Character Sets
10632 @cindex character sets
10634 @cindex translating between character sets
10635 @cindex host character set
10636 @cindex target character set
10638 If the program you are debugging uses a different character set to
10639 represent characters and strings than the one @value{GDBN} uses itself,
10640 @value{GDBN} can automatically translate between the character sets for
10641 you. The character set @value{GDBN} uses we call the @dfn{host
10642 character set}; the one the inferior program uses we call the
10643 @dfn{target character set}.
10645 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10646 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10647 remote protocol (@pxref{Remote Debugging}) to debug a program
10648 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10649 then the host character set is Latin-1, and the target character set is
10650 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10651 target-charset EBCDIC-US}, then @value{GDBN} translates between
10652 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10653 character and string literals in expressions.
10655 @value{GDBN} has no way to automatically recognize which character set
10656 the inferior program uses; you must tell it, using the @code{set
10657 target-charset} command, described below.
10659 Here are the commands for controlling @value{GDBN}'s character set
10663 @item set target-charset @var{charset}
10664 @kindex set target-charset
10665 Set the current target character set to @var{charset}. To display the
10666 list of supported target character sets, type
10667 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10669 @item set host-charset @var{charset}
10670 @kindex set host-charset
10671 Set the current host character set to @var{charset}.
10673 By default, @value{GDBN} uses a host character set appropriate to the
10674 system it is running on; you can override that default using the
10675 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10676 automatically determine the appropriate host character set. In this
10677 case, @value{GDBN} uses @samp{UTF-8}.
10679 @value{GDBN} can only use certain character sets as its host character
10680 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10681 @value{GDBN} will list the host character sets it supports.
10683 @item set charset @var{charset}
10684 @kindex set charset
10685 Set the current host and target character sets to @var{charset}. As
10686 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10687 @value{GDBN} will list the names of the character sets that can be used
10688 for both host and target.
10691 @kindex show charset
10692 Show the names of the current host and target character sets.
10694 @item show host-charset
10695 @kindex show host-charset
10696 Show the name of the current host character set.
10698 @item show target-charset
10699 @kindex show target-charset
10700 Show the name of the current target character set.
10702 @item set target-wide-charset @var{charset}
10703 @kindex set target-wide-charset
10704 Set the current target's wide character set to @var{charset}. This is
10705 the character set used by the target's @code{wchar_t} type. To
10706 display the list of supported wide character sets, type
10707 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10709 @item show target-wide-charset
10710 @kindex show target-wide-charset
10711 Show the name of the current target's wide character set.
10714 Here is an example of @value{GDBN}'s character set support in action.
10715 Assume that the following source code has been placed in the file
10716 @file{charset-test.c}:
10722 = @{72, 101, 108, 108, 111, 44, 32, 119,
10723 111, 114, 108, 100, 33, 10, 0@};
10724 char ibm1047_hello[]
10725 = @{200, 133, 147, 147, 150, 107, 64, 166,
10726 150, 153, 147, 132, 90, 37, 0@};
10730 printf ("Hello, world!\n");
10734 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10735 containing the string @samp{Hello, world!} followed by a newline,
10736 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10738 We compile the program, and invoke the debugger on it:
10741 $ gcc -g charset-test.c -o charset-test
10742 $ gdb -nw charset-test
10743 GNU gdb 2001-12-19-cvs
10744 Copyright 2001 Free Software Foundation, Inc.
10749 We can use the @code{show charset} command to see what character sets
10750 @value{GDBN} is currently using to interpret and display characters and
10754 (@value{GDBP}) show charset
10755 The current host and target character set is `ISO-8859-1'.
10759 For the sake of printing this manual, let's use @sc{ascii} as our
10760 initial character set:
10762 (@value{GDBP}) set charset ASCII
10763 (@value{GDBP}) show charset
10764 The current host and target character set is `ASCII'.
10768 Let's assume that @sc{ascii} is indeed the correct character set for our
10769 host system --- in other words, let's assume that if @value{GDBN} prints
10770 characters using the @sc{ascii} character set, our terminal will display
10771 them properly. Since our current target character set is also
10772 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10775 (@value{GDBP}) print ascii_hello
10776 $1 = 0x401698 "Hello, world!\n"
10777 (@value{GDBP}) print ascii_hello[0]
10782 @value{GDBN} uses the target character set for character and string
10783 literals you use in expressions:
10786 (@value{GDBP}) print '+'
10791 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10794 @value{GDBN} relies on the user to tell it which character set the
10795 target program uses. If we print @code{ibm1047_hello} while our target
10796 character set is still @sc{ascii}, we get jibberish:
10799 (@value{GDBP}) print ibm1047_hello
10800 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10801 (@value{GDBP}) print ibm1047_hello[0]
10806 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10807 @value{GDBN} tells us the character sets it supports:
10810 (@value{GDBP}) set target-charset
10811 ASCII EBCDIC-US IBM1047 ISO-8859-1
10812 (@value{GDBP}) set target-charset
10815 We can select @sc{ibm1047} as our target character set, and examine the
10816 program's strings again. Now the @sc{ascii} string is wrong, but
10817 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10818 target character set, @sc{ibm1047}, to the host character set,
10819 @sc{ascii}, and they display correctly:
10822 (@value{GDBP}) set target-charset IBM1047
10823 (@value{GDBP}) show charset
10824 The current host character set is `ASCII'.
10825 The current target character set is `IBM1047'.
10826 (@value{GDBP}) print ascii_hello
10827 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10828 (@value{GDBP}) print ascii_hello[0]
10830 (@value{GDBP}) print ibm1047_hello
10831 $8 = 0x4016a8 "Hello, world!\n"
10832 (@value{GDBP}) print ibm1047_hello[0]
10837 As above, @value{GDBN} uses the target character set for character and
10838 string literals you use in expressions:
10841 (@value{GDBP}) print '+'
10846 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10849 @node Caching Target Data
10850 @section Caching Data of Targets
10851 @cindex caching data of targets
10853 @value{GDBN} caches data exchanged between the debugger and a target.
10854 Each cache is associated with the address space of the inferior.
10855 @xref{Inferiors and Programs}, about inferior and address space.
10856 Such caching generally improves performance in remote debugging
10857 (@pxref{Remote Debugging}), because it reduces the overhead of the
10858 remote protocol by bundling memory reads and writes into large chunks.
10859 Unfortunately, simply caching everything would lead to incorrect results,
10860 since @value{GDBN} does not necessarily know anything about volatile
10861 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
10862 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
10864 Therefore, by default, @value{GDBN} only caches data
10865 known to be on the stack@footnote{In non-stop mode, it is moderately
10866 rare for a running thread to modify the stack of a stopped thread
10867 in a way that would interfere with a backtrace, and caching of
10868 stack reads provides a significant speed up of remote backtraces.} or
10869 in the code segment.
10870 Other regions of memory can be explicitly marked as
10871 cacheable; @pxref{Memory Region Attributes}.
10874 @kindex set remotecache
10875 @item set remotecache on
10876 @itemx set remotecache off
10877 This option no longer does anything; it exists for compatibility
10880 @kindex show remotecache
10881 @item show remotecache
10882 Show the current state of the obsolete remotecache flag.
10884 @kindex set stack-cache
10885 @item set stack-cache on
10886 @itemx set stack-cache off
10887 Enable or disable caching of stack accesses. When @code{on}, use
10888 caching. By default, this option is @code{on}.
10890 @kindex show stack-cache
10891 @item show stack-cache
10892 Show the current state of data caching for memory accesses.
10894 @kindex set code-cache
10895 @item set code-cache on
10896 @itemx set code-cache off
10897 Enable or disable caching of code segment accesses. When @code{on},
10898 use caching. By default, this option is @code{on}. This improves
10899 performance of disassembly in remote debugging.
10901 @kindex show code-cache
10902 @item show code-cache
10903 Show the current state of target memory cache for code segment
10906 @kindex info dcache
10907 @item info dcache @r{[}line@r{]}
10908 Print the information about the performance of data cache of the
10909 current inferior's address space. The information displayed
10910 includes the dcache width and depth, and for each cache line, its
10911 number, address, and how many times it was referenced. This
10912 command is useful for debugging the data cache operation.
10914 If a line number is specified, the contents of that line will be
10917 @item set dcache size @var{size}
10918 @cindex dcache size
10919 @kindex set dcache size
10920 Set maximum number of entries in dcache (dcache depth above).
10922 @item set dcache line-size @var{line-size}
10923 @cindex dcache line-size
10924 @kindex set dcache line-size
10925 Set number of bytes each dcache entry caches (dcache width above).
10926 Must be a power of 2.
10928 @item show dcache size
10929 @kindex show dcache size
10930 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
10932 @item show dcache line-size
10933 @kindex show dcache line-size
10934 Show default size of dcache lines.
10938 @node Searching Memory
10939 @section Search Memory
10940 @cindex searching memory
10942 Memory can be searched for a particular sequence of bytes with the
10943 @code{find} command.
10947 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10948 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10949 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10950 etc. The search begins at address @var{start_addr} and continues for either
10951 @var{len} bytes or through to @var{end_addr} inclusive.
10954 @var{s} and @var{n} are optional parameters.
10955 They may be specified in either order, apart or together.
10958 @item @var{s}, search query size
10959 The size of each search query value.
10965 halfwords (two bytes)
10969 giant words (eight bytes)
10972 All values are interpreted in the current language.
10973 This means, for example, that if the current source language is C/C@t{++}
10974 then searching for the string ``hello'' includes the trailing '\0'.
10976 If the value size is not specified, it is taken from the
10977 value's type in the current language.
10978 This is useful when one wants to specify the search
10979 pattern as a mixture of types.
10980 Note that this means, for example, that in the case of C-like languages
10981 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10982 which is typically four bytes.
10984 @item @var{n}, maximum number of finds
10985 The maximum number of matches to print. The default is to print all finds.
10988 You can use strings as search values. Quote them with double-quotes
10990 The string value is copied into the search pattern byte by byte,
10991 regardless of the endianness of the target and the size specification.
10993 The address of each match found is printed as well as a count of the
10994 number of matches found.
10996 The address of the last value found is stored in convenience variable
10998 A count of the number of matches is stored in @samp{$numfound}.
11000 For example, if stopped at the @code{printf} in this function:
11006 static char hello[] = "hello-hello";
11007 static struct @{ char c; short s; int i; @}
11008 __attribute__ ((packed)) mixed
11009 = @{ 'c', 0x1234, 0x87654321 @};
11010 printf ("%s\n", hello);
11015 you get during debugging:
11018 (gdb) find &hello[0], +sizeof(hello), "hello"
11019 0x804956d <hello.1620+6>
11021 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11022 0x8049567 <hello.1620>
11023 0x804956d <hello.1620+6>
11025 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11026 0x8049567 <hello.1620>
11028 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11029 0x8049560 <mixed.1625>
11031 (gdb) print $numfound
11034 $2 = (void *) 0x8049560
11037 @node Optimized Code
11038 @chapter Debugging Optimized Code
11039 @cindex optimized code, debugging
11040 @cindex debugging optimized code
11042 Almost all compilers support optimization. With optimization
11043 disabled, the compiler generates assembly code that corresponds
11044 directly to your source code, in a simplistic way. As the compiler
11045 applies more powerful optimizations, the generated assembly code
11046 diverges from your original source code. With help from debugging
11047 information generated by the compiler, @value{GDBN} can map from
11048 the running program back to constructs from your original source.
11050 @value{GDBN} is more accurate with optimization disabled. If you
11051 can recompile without optimization, it is easier to follow the
11052 progress of your program during debugging. But, there are many cases
11053 where you may need to debug an optimized version.
11055 When you debug a program compiled with @samp{-g -O}, remember that the
11056 optimizer has rearranged your code; the debugger shows you what is
11057 really there. Do not be too surprised when the execution path does not
11058 exactly match your source file! An extreme example: if you define a
11059 variable, but never use it, @value{GDBN} never sees that
11060 variable---because the compiler optimizes it out of existence.
11062 Some things do not work as well with @samp{-g -O} as with just
11063 @samp{-g}, particularly on machines with instruction scheduling. If in
11064 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11065 please report it to us as a bug (including a test case!).
11066 @xref{Variables}, for more information about debugging optimized code.
11069 * Inline Functions:: How @value{GDBN} presents inlining
11070 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11073 @node Inline Functions
11074 @section Inline Functions
11075 @cindex inline functions, debugging
11077 @dfn{Inlining} is an optimization that inserts a copy of the function
11078 body directly at each call site, instead of jumping to a shared
11079 routine. @value{GDBN} displays inlined functions just like
11080 non-inlined functions. They appear in backtraces. You can view their
11081 arguments and local variables, step into them with @code{step}, skip
11082 them with @code{next}, and escape from them with @code{finish}.
11083 You can check whether a function was inlined by using the
11084 @code{info frame} command.
11086 For @value{GDBN} to support inlined functions, the compiler must
11087 record information about inlining in the debug information ---
11088 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11089 other compilers do also. @value{GDBN} only supports inlined functions
11090 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11091 do not emit two required attributes (@samp{DW_AT_call_file} and
11092 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11093 function calls with earlier versions of @value{NGCC}. It instead
11094 displays the arguments and local variables of inlined functions as
11095 local variables in the caller.
11097 The body of an inlined function is directly included at its call site;
11098 unlike a non-inlined function, there are no instructions devoted to
11099 the call. @value{GDBN} still pretends that the call site and the
11100 start of the inlined function are different instructions. Stepping to
11101 the call site shows the call site, and then stepping again shows
11102 the first line of the inlined function, even though no additional
11103 instructions are executed.
11105 This makes source-level debugging much clearer; you can see both the
11106 context of the call and then the effect of the call. Only stepping by
11107 a single instruction using @code{stepi} or @code{nexti} does not do
11108 this; single instruction steps always show the inlined body.
11110 There are some ways that @value{GDBN} does not pretend that inlined
11111 function calls are the same as normal calls:
11115 Setting breakpoints at the call site of an inlined function may not
11116 work, because the call site does not contain any code. @value{GDBN}
11117 may incorrectly move the breakpoint to the next line of the enclosing
11118 function, after the call. This limitation will be removed in a future
11119 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11120 or inside the inlined function instead.
11123 @value{GDBN} cannot locate the return value of inlined calls after
11124 using the @code{finish} command. This is a limitation of compiler-generated
11125 debugging information; after @code{finish}, you can step to the next line
11126 and print a variable where your program stored the return value.
11130 @node Tail Call Frames
11131 @section Tail Call Frames
11132 @cindex tail call frames, debugging
11134 Function @code{B} can call function @code{C} in its very last statement. In
11135 unoptimized compilation the call of @code{C} is immediately followed by return
11136 instruction at the end of @code{B} code. Optimizing compiler may replace the
11137 call and return in function @code{B} into one jump to function @code{C}
11138 instead. Such use of a jump instruction is called @dfn{tail call}.
11140 During execution of function @code{C}, there will be no indication in the
11141 function call stack frames that it was tail-called from @code{B}. If function
11142 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11143 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11144 some cases @value{GDBN} can determine that @code{C} was tail-called from
11145 @code{B}, and it will then create fictitious call frame for that, with the
11146 return address set up as if @code{B} called @code{C} normally.
11148 This functionality is currently supported only by DWARF 2 debugging format and
11149 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11150 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11153 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11154 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11158 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11160 Stack level 1, frame at 0x7fffffffda30:
11161 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11162 tail call frame, caller of frame at 0x7fffffffda30
11163 source language c++.
11164 Arglist at unknown address.
11165 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11168 The detection of all the possible code path executions can find them ambiguous.
11169 There is no execution history stored (possible @ref{Reverse Execution} is never
11170 used for this purpose) and the last known caller could have reached the known
11171 callee by multiple different jump sequences. In such case @value{GDBN} still
11172 tries to show at least all the unambiguous top tail callers and all the
11173 unambiguous bottom tail calees, if any.
11176 @anchor{set debug entry-values}
11177 @item set debug entry-values
11178 @kindex set debug entry-values
11179 When set to on, enables printing of analysis messages for both frame argument
11180 values at function entry and tail calls. It will show all the possible valid
11181 tail calls code paths it has considered. It will also print the intersection
11182 of them with the final unambiguous (possibly partial or even empty) code path
11185 @item show debug entry-values
11186 @kindex show debug entry-values
11187 Show the current state of analysis messages printing for both frame argument
11188 values at function entry and tail calls.
11191 The analysis messages for tail calls can for example show why the virtual tail
11192 call frame for function @code{c} has not been recognized (due to the indirect
11193 reference by variable @code{x}):
11196 static void __attribute__((noinline, noclone)) c (void);
11197 void (*x) (void) = c;
11198 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11199 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11200 int main (void) @{ x (); return 0; @}
11202 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11203 DW_TAG_GNU_call_site 0x40039a in main
11205 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11208 #1 0x000000000040039a in main () at t.c:5
11211 Another possibility is an ambiguous virtual tail call frames resolution:
11215 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11216 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11217 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11218 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11219 static void __attribute__((noinline, noclone)) b (void)
11220 @{ if (i) c (); else e (); @}
11221 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11222 int main (void) @{ a (); return 0; @}
11224 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11225 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11226 tailcall: reduced: 0x4004d2(a) |
11229 #1 0x00000000004004d2 in a () at t.c:8
11230 #2 0x0000000000400395 in main () at t.c:9
11233 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11234 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11236 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11237 @ifset HAVE_MAKEINFO_CLICK
11238 @set ARROW @click{}
11239 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11240 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11242 @ifclear HAVE_MAKEINFO_CLICK
11244 @set CALLSEQ1B @value{CALLSEQ1A}
11245 @set CALLSEQ2B @value{CALLSEQ2A}
11248 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11249 The code can have possible execution paths @value{CALLSEQ1B} or
11250 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11252 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11253 has found. It then finds another possible calling sequcen - that one is
11254 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11255 printed as the @code{reduced:} calling sequence. That one could have many
11256 futher @code{compare:} and @code{reduced:} statements as long as there remain
11257 any non-ambiguous sequence entries.
11259 For the frame of function @code{b} in both cases there are different possible
11260 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11261 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11262 therefore this one is displayed to the user while the ambiguous frames are
11265 There can be also reasons why printing of frame argument values at function
11270 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11271 static void __attribute__((noinline, noclone)) a (int i);
11272 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11273 static void __attribute__((noinline, noclone)) a (int i)
11274 @{ if (i) b (i - 1); else c (0); @}
11275 int main (void) @{ a (5); return 0; @}
11278 #0 c (i=i@@entry=0) at t.c:2
11279 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11280 function "a" at 0x400420 can call itself via tail calls
11281 i=<optimized out>) at t.c:6
11282 #2 0x000000000040036e in main () at t.c:7
11285 @value{GDBN} cannot find out from the inferior state if and how many times did
11286 function @code{a} call itself (via function @code{b}) as these calls would be
11287 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11288 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11289 prints @code{<optimized out>} instead.
11292 @chapter C Preprocessor Macros
11294 Some languages, such as C and C@t{++}, provide a way to define and invoke
11295 ``preprocessor macros'' which expand into strings of tokens.
11296 @value{GDBN} can evaluate expressions containing macro invocations, show
11297 the result of macro expansion, and show a macro's definition, including
11298 where it was defined.
11300 You may need to compile your program specially to provide @value{GDBN}
11301 with information about preprocessor macros. Most compilers do not
11302 include macros in their debugging information, even when you compile
11303 with the @option{-g} flag. @xref{Compilation}.
11305 A program may define a macro at one point, remove that definition later,
11306 and then provide a different definition after that. Thus, at different
11307 points in the program, a macro may have different definitions, or have
11308 no definition at all. If there is a current stack frame, @value{GDBN}
11309 uses the macros in scope at that frame's source code line. Otherwise,
11310 @value{GDBN} uses the macros in scope at the current listing location;
11313 Whenever @value{GDBN} evaluates an expression, it always expands any
11314 macro invocations present in the expression. @value{GDBN} also provides
11315 the following commands for working with macros explicitly.
11319 @kindex macro expand
11320 @cindex macro expansion, showing the results of preprocessor
11321 @cindex preprocessor macro expansion, showing the results of
11322 @cindex expanding preprocessor macros
11323 @item macro expand @var{expression}
11324 @itemx macro exp @var{expression}
11325 Show the results of expanding all preprocessor macro invocations in
11326 @var{expression}. Since @value{GDBN} simply expands macros, but does
11327 not parse the result, @var{expression} need not be a valid expression;
11328 it can be any string of tokens.
11331 @item macro expand-once @var{expression}
11332 @itemx macro exp1 @var{expression}
11333 @cindex expand macro once
11334 @i{(This command is not yet implemented.)} Show the results of
11335 expanding those preprocessor macro invocations that appear explicitly in
11336 @var{expression}. Macro invocations appearing in that expansion are
11337 left unchanged. This command allows you to see the effect of a
11338 particular macro more clearly, without being confused by further
11339 expansions. Since @value{GDBN} simply expands macros, but does not
11340 parse the result, @var{expression} need not be a valid expression; it
11341 can be any string of tokens.
11344 @cindex macro definition, showing
11345 @cindex definition of a macro, showing
11346 @cindex macros, from debug info
11347 @item info macro [-a|-all] [--] @var{macro}
11348 Show the current definition or all definitions of the named @var{macro},
11349 and describe the source location or compiler command-line where that
11350 definition was established. The optional double dash is to signify the end of
11351 argument processing and the beginning of @var{macro} for non C-like macros where
11352 the macro may begin with a hyphen.
11354 @kindex info macros
11355 @item info macros @var{linespec}
11356 Show all macro definitions that are in effect at the location specified
11357 by @var{linespec}, and describe the source location or compiler
11358 command-line where those definitions were established.
11360 @kindex macro define
11361 @cindex user-defined macros
11362 @cindex defining macros interactively
11363 @cindex macros, user-defined
11364 @item macro define @var{macro} @var{replacement-list}
11365 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11366 Introduce a definition for a preprocessor macro named @var{macro},
11367 invocations of which are replaced by the tokens given in
11368 @var{replacement-list}. The first form of this command defines an
11369 ``object-like'' macro, which takes no arguments; the second form
11370 defines a ``function-like'' macro, which takes the arguments given in
11373 A definition introduced by this command is in scope in every
11374 expression evaluated in @value{GDBN}, until it is removed with the
11375 @code{macro undef} command, described below. The definition overrides
11376 all definitions for @var{macro} present in the program being debugged,
11377 as well as any previous user-supplied definition.
11379 @kindex macro undef
11380 @item macro undef @var{macro}
11381 Remove any user-supplied definition for the macro named @var{macro}.
11382 This command only affects definitions provided with the @code{macro
11383 define} command, described above; it cannot remove definitions present
11384 in the program being debugged.
11388 List all the macros defined using the @code{macro define} command.
11391 @cindex macros, example of debugging with
11392 Here is a transcript showing the above commands in action. First, we
11393 show our source files:
11398 #include "sample.h"
11401 #define ADD(x) (M + x)
11406 printf ("Hello, world!\n");
11408 printf ("We're so creative.\n");
11410 printf ("Goodbye, world!\n");
11417 Now, we compile the program using the @sc{gnu} C compiler,
11418 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11419 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11420 and @option{-gdwarf-4}; we recommend always choosing the most recent
11421 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11422 includes information about preprocessor macros in the debugging
11426 $ gcc -gdwarf-2 -g3 sample.c -o sample
11430 Now, we start @value{GDBN} on our sample program:
11434 GNU gdb 2002-05-06-cvs
11435 Copyright 2002 Free Software Foundation, Inc.
11436 GDB is free software, @dots{}
11440 We can expand macros and examine their definitions, even when the
11441 program is not running. @value{GDBN} uses the current listing position
11442 to decide which macro definitions are in scope:
11445 (@value{GDBP}) list main
11448 5 #define ADD(x) (M + x)
11453 10 printf ("Hello, world!\n");
11455 12 printf ("We're so creative.\n");
11456 (@value{GDBP}) info macro ADD
11457 Defined at /home/jimb/gdb/macros/play/sample.c:5
11458 #define ADD(x) (M + x)
11459 (@value{GDBP}) info macro Q
11460 Defined at /home/jimb/gdb/macros/play/sample.h:1
11461 included at /home/jimb/gdb/macros/play/sample.c:2
11463 (@value{GDBP}) macro expand ADD(1)
11464 expands to: (42 + 1)
11465 (@value{GDBP}) macro expand-once ADD(1)
11466 expands to: once (M + 1)
11470 In the example above, note that @code{macro expand-once} expands only
11471 the macro invocation explicit in the original text --- the invocation of
11472 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11473 which was introduced by @code{ADD}.
11475 Once the program is running, @value{GDBN} uses the macro definitions in
11476 force at the source line of the current stack frame:
11479 (@value{GDBP}) break main
11480 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11482 Starting program: /home/jimb/gdb/macros/play/sample
11484 Breakpoint 1, main () at sample.c:10
11485 10 printf ("Hello, world!\n");
11489 At line 10, the definition of the macro @code{N} at line 9 is in force:
11492 (@value{GDBP}) info macro N
11493 Defined at /home/jimb/gdb/macros/play/sample.c:9
11495 (@value{GDBP}) macro expand N Q M
11496 expands to: 28 < 42
11497 (@value{GDBP}) print N Q M
11502 As we step over directives that remove @code{N}'s definition, and then
11503 give it a new definition, @value{GDBN} finds the definition (or lack
11504 thereof) in force at each point:
11507 (@value{GDBP}) next
11509 12 printf ("We're so creative.\n");
11510 (@value{GDBP}) info macro N
11511 The symbol `N' has no definition as a C/C++ preprocessor macro
11512 at /home/jimb/gdb/macros/play/sample.c:12
11513 (@value{GDBP}) next
11515 14 printf ("Goodbye, world!\n");
11516 (@value{GDBP}) info macro N
11517 Defined at /home/jimb/gdb/macros/play/sample.c:13
11519 (@value{GDBP}) macro expand N Q M
11520 expands to: 1729 < 42
11521 (@value{GDBP}) print N Q M
11526 In addition to source files, macros can be defined on the compilation command
11527 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11528 such a way, @value{GDBN} displays the location of their definition as line zero
11529 of the source file submitted to the compiler.
11532 (@value{GDBP}) info macro __STDC__
11533 Defined at /home/jimb/gdb/macros/play/sample.c:0
11540 @chapter Tracepoints
11541 @c This chapter is based on the documentation written by Michael
11542 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11544 @cindex tracepoints
11545 In some applications, it is not feasible for the debugger to interrupt
11546 the program's execution long enough for the developer to learn
11547 anything helpful about its behavior. If the program's correctness
11548 depends on its real-time behavior, delays introduced by a debugger
11549 might cause the program to change its behavior drastically, or perhaps
11550 fail, even when the code itself is correct. It is useful to be able
11551 to observe the program's behavior without interrupting it.
11553 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11554 specify locations in the program, called @dfn{tracepoints}, and
11555 arbitrary expressions to evaluate when those tracepoints are reached.
11556 Later, using the @code{tfind} command, you can examine the values
11557 those expressions had when the program hit the tracepoints. The
11558 expressions may also denote objects in memory---structures or arrays,
11559 for example---whose values @value{GDBN} should record; while visiting
11560 a particular tracepoint, you may inspect those objects as if they were
11561 in memory at that moment. However, because @value{GDBN} records these
11562 values without interacting with you, it can do so quickly and
11563 unobtrusively, hopefully not disturbing the program's behavior.
11565 The tracepoint facility is currently available only for remote
11566 targets. @xref{Targets}. In addition, your remote target must know
11567 how to collect trace data. This functionality is implemented in the
11568 remote stub; however, none of the stubs distributed with @value{GDBN}
11569 support tracepoints as of this writing. The format of the remote
11570 packets used to implement tracepoints are described in @ref{Tracepoint
11573 It is also possible to get trace data from a file, in a manner reminiscent
11574 of corefiles; you specify the filename, and use @code{tfind} to search
11575 through the file. @xref{Trace Files}, for more details.
11577 This chapter describes the tracepoint commands and features.
11580 * Set Tracepoints::
11581 * Analyze Collected Data::
11582 * Tracepoint Variables::
11586 @node Set Tracepoints
11587 @section Commands to Set Tracepoints
11589 Before running such a @dfn{trace experiment}, an arbitrary number of
11590 tracepoints can be set. A tracepoint is actually a special type of
11591 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11592 standard breakpoint commands. For instance, as with breakpoints,
11593 tracepoint numbers are successive integers starting from one, and many
11594 of the commands associated with tracepoints take the tracepoint number
11595 as their argument, to identify which tracepoint to work on.
11597 For each tracepoint, you can specify, in advance, some arbitrary set
11598 of data that you want the target to collect in the trace buffer when
11599 it hits that tracepoint. The collected data can include registers,
11600 local variables, or global data. Later, you can use @value{GDBN}
11601 commands to examine the values these data had at the time the
11602 tracepoint was hit.
11604 Tracepoints do not support every breakpoint feature. Ignore counts on
11605 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11606 commands when they are hit. Tracepoints may not be thread-specific
11609 @cindex fast tracepoints
11610 Some targets may support @dfn{fast tracepoints}, which are inserted in
11611 a different way (such as with a jump instead of a trap), that is
11612 faster but possibly restricted in where they may be installed.
11614 @cindex static tracepoints
11615 @cindex markers, static tracepoints
11616 @cindex probing markers, static tracepoints
11617 Regular and fast tracepoints are dynamic tracing facilities, meaning
11618 that they can be used to insert tracepoints at (almost) any location
11619 in the target. Some targets may also support controlling @dfn{static
11620 tracepoints} from @value{GDBN}. With static tracing, a set of
11621 instrumentation points, also known as @dfn{markers}, are embedded in
11622 the target program, and can be activated or deactivated by name or
11623 address. These are usually placed at locations which facilitate
11624 investigating what the target is actually doing. @value{GDBN}'s
11625 support for static tracing includes being able to list instrumentation
11626 points, and attach them with @value{GDBN} defined high level
11627 tracepoints that expose the whole range of convenience of
11628 @value{GDBN}'s tracepoints support. Namely, support for collecting
11629 registers values and values of global or local (to the instrumentation
11630 point) variables; tracepoint conditions and trace state variables.
11631 The act of installing a @value{GDBN} static tracepoint on an
11632 instrumentation point, or marker, is referred to as @dfn{probing} a
11633 static tracepoint marker.
11635 @code{gdbserver} supports tracepoints on some target systems.
11636 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11638 This section describes commands to set tracepoints and associated
11639 conditions and actions.
11642 * Create and Delete Tracepoints::
11643 * Enable and Disable Tracepoints::
11644 * Tracepoint Passcounts::
11645 * Tracepoint Conditions::
11646 * Trace State Variables::
11647 * Tracepoint Actions::
11648 * Listing Tracepoints::
11649 * Listing Static Tracepoint Markers::
11650 * Starting and Stopping Trace Experiments::
11651 * Tracepoint Restrictions::
11654 @node Create and Delete Tracepoints
11655 @subsection Create and Delete Tracepoints
11658 @cindex set tracepoint
11660 @item trace @var{location}
11661 The @code{trace} command is very similar to the @code{break} command.
11662 Its argument @var{location} can be a source line, a function name, or
11663 an address in the target program. @xref{Specify Location}. The
11664 @code{trace} command defines a tracepoint, which is a point in the
11665 target program where the debugger will briefly stop, collect some
11666 data, and then allow the program to continue. Setting a tracepoint or
11667 changing its actions takes effect immediately if the remote stub
11668 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11670 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11671 these changes don't take effect until the next @code{tstart}
11672 command, and once a trace experiment is running, further changes will
11673 not have any effect until the next trace experiment starts. In addition,
11674 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11675 address is not yet resolved. (This is similar to pending breakpoints.)
11676 Pending tracepoints are not downloaded to the target and not installed
11677 until they are resolved. The resolution of pending tracepoints requires
11678 @value{GDBN} support---when debugging with the remote target, and
11679 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11680 tracing}), pending tracepoints can not be resolved (and downloaded to
11681 the remote stub) while @value{GDBN} is disconnected.
11683 Here are some examples of using the @code{trace} command:
11686 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11688 (@value{GDBP}) @b{trace +2} // 2 lines forward
11690 (@value{GDBP}) @b{trace my_function} // first source line of function
11692 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11694 (@value{GDBP}) @b{trace *0x2117c4} // an address
11698 You can abbreviate @code{trace} as @code{tr}.
11700 @item trace @var{location} if @var{cond}
11701 Set a tracepoint with condition @var{cond}; evaluate the expression
11702 @var{cond} each time the tracepoint is reached, and collect data only
11703 if the value is nonzero---that is, if @var{cond} evaluates as true.
11704 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11705 information on tracepoint conditions.
11707 @item ftrace @var{location} [ if @var{cond} ]
11708 @cindex set fast tracepoint
11709 @cindex fast tracepoints, setting
11711 The @code{ftrace} command sets a fast tracepoint. For targets that
11712 support them, fast tracepoints will use a more efficient but possibly
11713 less general technique to trigger data collection, such as a jump
11714 instruction instead of a trap, or some sort of hardware support. It
11715 may not be possible to create a fast tracepoint at the desired
11716 location, in which case the command will exit with an explanatory
11719 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11722 On 32-bit x86-architecture systems, fast tracepoints normally need to
11723 be placed at an instruction that is 5 bytes or longer, but can be
11724 placed at 4-byte instructions if the low 64K of memory of the target
11725 program is available to install trampolines. Some Unix-type systems,
11726 such as @sc{gnu}/Linux, exclude low addresses from the program's
11727 address space; but for instance with the Linux kernel it is possible
11728 to let @value{GDBN} use this area by doing a @command{sysctl} command
11729 to set the @code{mmap_min_addr} kernel parameter, as in
11732 sudo sysctl -w vm.mmap_min_addr=32768
11736 which sets the low address to 32K, which leaves plenty of room for
11737 trampolines. The minimum address should be set to a page boundary.
11739 @item strace @var{location} [ if @var{cond} ]
11740 @cindex set static tracepoint
11741 @cindex static tracepoints, setting
11742 @cindex probe static tracepoint marker
11744 The @code{strace} command sets a static tracepoint. For targets that
11745 support it, setting a static tracepoint probes a static
11746 instrumentation point, or marker, found at @var{location}. It may not
11747 be possible to set a static tracepoint at the desired location, in
11748 which case the command will exit with an explanatory message.
11750 @value{GDBN} handles arguments to @code{strace} exactly as for
11751 @code{trace}, with the addition that the user can also specify
11752 @code{-m @var{marker}} as @var{location}. This probes the marker
11753 identified by the @var{marker} string identifier. This identifier
11754 depends on the static tracepoint backend library your program is
11755 using. You can find all the marker identifiers in the @samp{ID} field
11756 of the @code{info static-tracepoint-markers} command output.
11757 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11758 Markers}. For example, in the following small program using the UST
11764 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11769 the marker id is composed of joining the first two arguments to the
11770 @code{trace_mark} call with a slash, which translates to:
11773 (@value{GDBP}) info static-tracepoint-markers
11774 Cnt Enb ID Address What
11775 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11781 so you may probe the marker above with:
11784 (@value{GDBP}) strace -m ust/bar33
11787 Static tracepoints accept an extra collect action --- @code{collect
11788 $_sdata}. This collects arbitrary user data passed in the probe point
11789 call to the tracing library. In the UST example above, you'll see
11790 that the third argument to @code{trace_mark} is a printf-like format
11791 string. The user data is then the result of running that formating
11792 string against the following arguments. Note that @code{info
11793 static-tracepoint-markers} command output lists that format string in
11794 the @samp{Data:} field.
11796 You can inspect this data when analyzing the trace buffer, by printing
11797 the $_sdata variable like any other variable available to
11798 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11801 @cindex last tracepoint number
11802 @cindex recent tracepoint number
11803 @cindex tracepoint number
11804 The convenience variable @code{$tpnum} records the tracepoint number
11805 of the most recently set tracepoint.
11807 @kindex delete tracepoint
11808 @cindex tracepoint deletion
11809 @item delete tracepoint @r{[}@var{num}@r{]}
11810 Permanently delete one or more tracepoints. With no argument, the
11811 default is to delete all tracepoints. Note that the regular
11812 @code{delete} command can remove tracepoints also.
11817 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11819 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11823 You can abbreviate this command as @code{del tr}.
11826 @node Enable and Disable Tracepoints
11827 @subsection Enable and Disable Tracepoints
11829 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11832 @kindex disable tracepoint
11833 @item disable tracepoint @r{[}@var{num}@r{]}
11834 Disable tracepoint @var{num}, or all tracepoints if no argument
11835 @var{num} is given. A disabled tracepoint will have no effect during
11836 a trace experiment, but it is not forgotten. You can re-enable
11837 a disabled tracepoint using the @code{enable tracepoint} command.
11838 If the command is issued during a trace experiment and the debug target
11839 has support for disabling tracepoints during a trace experiment, then the
11840 change will be effective immediately. Otherwise, it will be applied to the
11841 next trace experiment.
11843 @kindex enable tracepoint
11844 @item enable tracepoint @r{[}@var{num}@r{]}
11845 Enable tracepoint @var{num}, or all tracepoints. If this command is
11846 issued during a trace experiment and the debug target supports enabling
11847 tracepoints during a trace experiment, then the enabled tracepoints will
11848 become effective immediately. Otherwise, they will become effective the
11849 next time a trace experiment is run.
11852 @node Tracepoint Passcounts
11853 @subsection Tracepoint Passcounts
11857 @cindex tracepoint pass count
11858 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11859 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11860 automatically stop a trace experiment. If a tracepoint's passcount is
11861 @var{n}, then the trace experiment will be automatically stopped on
11862 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11863 @var{num} is not specified, the @code{passcount} command sets the
11864 passcount of the most recently defined tracepoint. If no passcount is
11865 given, the trace experiment will run until stopped explicitly by the
11871 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11872 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11874 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11875 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11876 (@value{GDBP}) @b{trace foo}
11877 (@value{GDBP}) @b{pass 3}
11878 (@value{GDBP}) @b{trace bar}
11879 (@value{GDBP}) @b{pass 2}
11880 (@value{GDBP}) @b{trace baz}
11881 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11882 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11883 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11884 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11888 @node Tracepoint Conditions
11889 @subsection Tracepoint Conditions
11890 @cindex conditional tracepoints
11891 @cindex tracepoint conditions
11893 The simplest sort of tracepoint collects data every time your program
11894 reaches a specified place. You can also specify a @dfn{condition} for
11895 a tracepoint. A condition is just a Boolean expression in your
11896 programming language (@pxref{Expressions, ,Expressions}). A
11897 tracepoint with a condition evaluates the expression each time your
11898 program reaches it, and data collection happens only if the condition
11901 Tracepoint conditions can be specified when a tracepoint is set, by
11902 using @samp{if} in the arguments to the @code{trace} command.
11903 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11904 also be set or changed at any time with the @code{condition} command,
11905 just as with breakpoints.
11907 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11908 the conditional expression itself. Instead, @value{GDBN} encodes the
11909 expression into an agent expression (@pxref{Agent Expressions})
11910 suitable for execution on the target, independently of @value{GDBN}.
11911 Global variables become raw memory locations, locals become stack
11912 accesses, and so forth.
11914 For instance, suppose you have a function that is usually called
11915 frequently, but should not be called after an error has occurred. You
11916 could use the following tracepoint command to collect data about calls
11917 of that function that happen while the error code is propagating
11918 through the program; an unconditional tracepoint could end up
11919 collecting thousands of useless trace frames that you would have to
11923 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11926 @node Trace State Variables
11927 @subsection Trace State Variables
11928 @cindex trace state variables
11930 A @dfn{trace state variable} is a special type of variable that is
11931 created and managed by target-side code. The syntax is the same as
11932 that for GDB's convenience variables (a string prefixed with ``$''),
11933 but they are stored on the target. They must be created explicitly,
11934 using a @code{tvariable} command. They are always 64-bit signed
11937 Trace state variables are remembered by @value{GDBN}, and downloaded
11938 to the target along with tracepoint information when the trace
11939 experiment starts. There are no intrinsic limits on the number of
11940 trace state variables, beyond memory limitations of the target.
11942 @cindex convenience variables, and trace state variables
11943 Although trace state variables are managed by the target, you can use
11944 them in print commands and expressions as if they were convenience
11945 variables; @value{GDBN} will get the current value from the target
11946 while the trace experiment is running. Trace state variables share
11947 the same namespace as other ``$'' variables, which means that you
11948 cannot have trace state variables with names like @code{$23} or
11949 @code{$pc}, nor can you have a trace state variable and a convenience
11950 variable with the same name.
11954 @item tvariable $@var{name} [ = @var{expression} ]
11956 The @code{tvariable} command creates a new trace state variable named
11957 @code{$@var{name}}, and optionally gives it an initial value of
11958 @var{expression}. @var{expression} is evaluated when this command is
11959 entered; the result will be converted to an integer if possible,
11960 otherwise @value{GDBN} will report an error. A subsequent
11961 @code{tvariable} command specifying the same name does not create a
11962 variable, but instead assigns the supplied initial value to the
11963 existing variable of that name, overwriting any previous initial
11964 value. The default initial value is 0.
11966 @item info tvariables
11967 @kindex info tvariables
11968 List all the trace state variables along with their initial values.
11969 Their current values may also be displayed, if the trace experiment is
11972 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11973 @kindex delete tvariable
11974 Delete the given trace state variables, or all of them if no arguments
11979 @node Tracepoint Actions
11980 @subsection Tracepoint Action Lists
11984 @cindex tracepoint actions
11985 @item actions @r{[}@var{num}@r{]}
11986 This command will prompt for a list of actions to be taken when the
11987 tracepoint is hit. If the tracepoint number @var{num} is not
11988 specified, this command sets the actions for the one that was most
11989 recently defined (so that you can define a tracepoint and then say
11990 @code{actions} without bothering about its number). You specify the
11991 actions themselves on the following lines, one action at a time, and
11992 terminate the actions list with a line containing just @code{end}. So
11993 far, the only defined actions are @code{collect}, @code{teval}, and
11994 @code{while-stepping}.
11996 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11997 Commands, ,Breakpoint Command Lists}), except that only the defined
11998 actions are allowed; any other @value{GDBN} command is rejected.
12000 @cindex remove actions from a tracepoint
12001 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12002 and follow it immediately with @samp{end}.
12005 (@value{GDBP}) @b{collect @var{data}} // collect some data
12007 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12009 (@value{GDBP}) @b{end} // signals the end of actions.
12012 In the following example, the action list begins with @code{collect}
12013 commands indicating the things to be collected when the tracepoint is
12014 hit. Then, in order to single-step and collect additional data
12015 following the tracepoint, a @code{while-stepping} command is used,
12016 followed by the list of things to be collected after each step in a
12017 sequence of single steps. The @code{while-stepping} command is
12018 terminated by its own separate @code{end} command. Lastly, the action
12019 list is terminated by an @code{end} command.
12022 (@value{GDBP}) @b{trace foo}
12023 (@value{GDBP}) @b{actions}
12024 Enter actions for tracepoint 1, one per line:
12027 > while-stepping 12
12028 > collect $pc, arr[i]
12033 @kindex collect @r{(tracepoints)}
12034 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12035 Collect values of the given expressions when the tracepoint is hit.
12036 This command accepts a comma-separated list of any valid expressions.
12037 In addition to global, static, or local variables, the following
12038 special arguments are supported:
12042 Collect all registers.
12045 Collect all function arguments.
12048 Collect all local variables.
12051 Collect the return address. This is helpful if you want to see more
12055 Collects the number of arguments from the static probe at which the
12056 tracepoint is located.
12057 @xref{Static Probe Points}.
12059 @item $_probe_arg@var{n}
12060 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12061 from the static probe at which the tracepoint is located.
12062 @xref{Static Probe Points}.
12065 @vindex $_sdata@r{, collect}
12066 Collect static tracepoint marker specific data. Only available for
12067 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12068 Lists}. On the UST static tracepoints library backend, an
12069 instrumentation point resembles a @code{printf} function call. The
12070 tracing library is able to collect user specified data formatted to a
12071 character string using the format provided by the programmer that
12072 instrumented the program. Other backends have similar mechanisms.
12073 Here's an example of a UST marker call:
12076 const char master_name[] = "$your_name";
12077 trace_mark(channel1, marker1, "hello %s", master_name)
12080 In this case, collecting @code{$_sdata} collects the string
12081 @samp{hello $yourname}. When analyzing the trace buffer, you can
12082 inspect @samp{$_sdata} like any other variable available to
12086 You can give several consecutive @code{collect} commands, each one
12087 with a single argument, or one @code{collect} command with several
12088 arguments separated by commas; the effect is the same.
12090 The optional @var{mods} changes the usual handling of the arguments.
12091 @code{s} requests that pointers to chars be handled as strings, in
12092 particular collecting the contents of the memory being pointed at, up
12093 to the first zero. The upper bound is by default the value of the
12094 @code{print elements} variable; if @code{s} is followed by a decimal
12095 number, that is the upper bound instead. So for instance
12096 @samp{collect/s25 mystr} collects as many as 25 characters at
12099 The command @code{info scope} (@pxref{Symbols, info scope}) is
12100 particularly useful for figuring out what data to collect.
12102 @kindex teval @r{(tracepoints)}
12103 @item teval @var{expr1}, @var{expr2}, @dots{}
12104 Evaluate the given expressions when the tracepoint is hit. This
12105 command accepts a comma-separated list of expressions. The results
12106 are discarded, so this is mainly useful for assigning values to trace
12107 state variables (@pxref{Trace State Variables}) without adding those
12108 values to the trace buffer, as would be the case if the @code{collect}
12111 @kindex while-stepping @r{(tracepoints)}
12112 @item while-stepping @var{n}
12113 Perform @var{n} single-step instruction traces after the tracepoint,
12114 collecting new data after each step. The @code{while-stepping}
12115 command is followed by the list of what to collect while stepping
12116 (followed by its own @code{end} command):
12119 > while-stepping 12
12120 > collect $regs, myglobal
12126 Note that @code{$pc} is not automatically collected by
12127 @code{while-stepping}; you need to explicitly collect that register if
12128 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12131 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12132 @kindex set default-collect
12133 @cindex default collection action
12134 This variable is a list of expressions to collect at each tracepoint
12135 hit. It is effectively an additional @code{collect} action prepended
12136 to every tracepoint action list. The expressions are parsed
12137 individually for each tracepoint, so for instance a variable named
12138 @code{xyz} may be interpreted as a global for one tracepoint, and a
12139 local for another, as appropriate to the tracepoint's location.
12141 @item show default-collect
12142 @kindex show default-collect
12143 Show the list of expressions that are collected by default at each
12148 @node Listing Tracepoints
12149 @subsection Listing Tracepoints
12152 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12153 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12154 @cindex information about tracepoints
12155 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12156 Display information about the tracepoint @var{num}. If you don't
12157 specify a tracepoint number, displays information about all the
12158 tracepoints defined so far. The format is similar to that used for
12159 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12160 command, simply restricting itself to tracepoints.
12162 A tracepoint's listing may include additional information specific to
12167 its passcount as given by the @code{passcount @var{n}} command
12170 the state about installed on target of each location
12174 (@value{GDBP}) @b{info trace}
12175 Num Type Disp Enb Address What
12176 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12178 collect globfoo, $regs
12183 2 tracepoint keep y <MULTIPLE>
12185 2.1 y 0x0804859c in func4 at change-loc.h:35
12186 installed on target
12187 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12188 installed on target
12189 2.3 y <PENDING> set_tracepoint
12190 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12191 not installed on target
12196 This command can be abbreviated @code{info tp}.
12199 @node Listing Static Tracepoint Markers
12200 @subsection Listing Static Tracepoint Markers
12203 @kindex info static-tracepoint-markers
12204 @cindex information about static tracepoint markers
12205 @item info static-tracepoint-markers
12206 Display information about all static tracepoint markers defined in the
12209 For each marker, the following columns are printed:
12213 An incrementing counter, output to help readability. This is not a
12216 The marker ID, as reported by the target.
12217 @item Enabled or Disabled
12218 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12219 that are not enabled.
12221 Where the marker is in your program, as a memory address.
12223 Where the marker is in the source for your program, as a file and line
12224 number. If the debug information included in the program does not
12225 allow @value{GDBN} to locate the source of the marker, this column
12226 will be left blank.
12230 In addition, the following information may be printed for each marker:
12234 User data passed to the tracing library by the marker call. In the
12235 UST backend, this is the format string passed as argument to the
12237 @item Static tracepoints probing the marker
12238 The list of static tracepoints attached to the marker.
12242 (@value{GDBP}) info static-tracepoint-markers
12243 Cnt ID Enb Address What
12244 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12245 Data: number1 %d number2 %d
12246 Probed by static tracepoints: #2
12247 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12253 @node Starting and Stopping Trace Experiments
12254 @subsection Starting and Stopping Trace Experiments
12257 @kindex tstart [ @var{notes} ]
12258 @cindex start a new trace experiment
12259 @cindex collected data discarded
12261 This command starts the trace experiment, and begins collecting data.
12262 It has the side effect of discarding all the data collected in the
12263 trace buffer during the previous trace experiment. If any arguments
12264 are supplied, they are taken as a note and stored with the trace
12265 experiment's state. The notes may be arbitrary text, and are
12266 especially useful with disconnected tracing in a multi-user context;
12267 the notes can explain what the trace is doing, supply user contact
12268 information, and so forth.
12270 @kindex tstop [ @var{notes} ]
12271 @cindex stop a running trace experiment
12273 This command stops the trace experiment. If any arguments are
12274 supplied, they are recorded with the experiment as a note. This is
12275 useful if you are stopping a trace started by someone else, for
12276 instance if the trace is interfering with the system's behavior and
12277 needs to be stopped quickly.
12279 @strong{Note}: a trace experiment and data collection may stop
12280 automatically if any tracepoint's passcount is reached
12281 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12284 @cindex status of trace data collection
12285 @cindex trace experiment, status of
12287 This command displays the status of the current trace data
12291 Here is an example of the commands we described so far:
12294 (@value{GDBP}) @b{trace gdb_c_test}
12295 (@value{GDBP}) @b{actions}
12296 Enter actions for tracepoint #1, one per line.
12297 > collect $regs,$locals,$args
12298 > while-stepping 11
12302 (@value{GDBP}) @b{tstart}
12303 [time passes @dots{}]
12304 (@value{GDBP}) @b{tstop}
12307 @anchor{disconnected tracing}
12308 @cindex disconnected tracing
12309 You can choose to continue running the trace experiment even if
12310 @value{GDBN} disconnects from the target, voluntarily or
12311 involuntarily. For commands such as @code{detach}, the debugger will
12312 ask what you want to do with the trace. But for unexpected
12313 terminations (@value{GDBN} crash, network outage), it would be
12314 unfortunate to lose hard-won trace data, so the variable
12315 @code{disconnected-tracing} lets you decide whether the trace should
12316 continue running without @value{GDBN}.
12319 @item set disconnected-tracing on
12320 @itemx set disconnected-tracing off
12321 @kindex set disconnected-tracing
12322 Choose whether a tracing run should continue to run if @value{GDBN}
12323 has disconnected from the target. Note that @code{detach} or
12324 @code{quit} will ask you directly what to do about a running trace no
12325 matter what this variable's setting, so the variable is mainly useful
12326 for handling unexpected situations, such as loss of the network.
12328 @item show disconnected-tracing
12329 @kindex show disconnected-tracing
12330 Show the current choice for disconnected tracing.
12334 When you reconnect to the target, the trace experiment may or may not
12335 still be running; it might have filled the trace buffer in the
12336 meantime, or stopped for one of the other reasons. If it is running,
12337 it will continue after reconnection.
12339 Upon reconnection, the target will upload information about the
12340 tracepoints in effect. @value{GDBN} will then compare that
12341 information to the set of tracepoints currently defined, and attempt
12342 to match them up, allowing for the possibility that the numbers may
12343 have changed due to creation and deletion in the meantime. If one of
12344 the target's tracepoints does not match any in @value{GDBN}, the
12345 debugger will create a new tracepoint, so that you have a number with
12346 which to specify that tracepoint. This matching-up process is
12347 necessarily heuristic, and it may result in useless tracepoints being
12348 created; you may simply delete them if they are of no use.
12350 @cindex circular trace buffer
12351 If your target agent supports a @dfn{circular trace buffer}, then you
12352 can run a trace experiment indefinitely without filling the trace
12353 buffer; when space runs out, the agent deletes already-collected trace
12354 frames, oldest first, until there is enough room to continue
12355 collecting. This is especially useful if your tracepoints are being
12356 hit too often, and your trace gets terminated prematurely because the
12357 buffer is full. To ask for a circular trace buffer, simply set
12358 @samp{circular-trace-buffer} to on. You can set this at any time,
12359 including during tracing; if the agent can do it, it will change
12360 buffer handling on the fly, otherwise it will not take effect until
12364 @item set circular-trace-buffer on
12365 @itemx set circular-trace-buffer off
12366 @kindex set circular-trace-buffer
12367 Choose whether a tracing run should use a linear or circular buffer
12368 for trace data. A linear buffer will not lose any trace data, but may
12369 fill up prematurely, while a circular buffer will discard old trace
12370 data, but it will have always room for the latest tracepoint hits.
12372 @item show circular-trace-buffer
12373 @kindex show circular-trace-buffer
12374 Show the current choice for the trace buffer. Note that this may not
12375 match the agent's current buffer handling, nor is it guaranteed to
12376 match the setting that might have been in effect during a past run,
12377 for instance if you are looking at frames from a trace file.
12382 @item set trace-buffer-size @var{n}
12383 @itemx set trace-buffer-size unlimited
12384 @kindex set trace-buffer-size
12385 Request that the target use a trace buffer of @var{n} bytes. Not all
12386 targets will honor the request; they may have a compiled-in size for
12387 the trace buffer, or some other limitation. Set to a value of
12388 @code{unlimited} or @code{-1} to let the target use whatever size it
12389 likes. This is also the default.
12391 @item show trace-buffer-size
12392 @kindex show trace-buffer-size
12393 Show the current requested size for the trace buffer. Note that this
12394 will only match the actual size if the target supports size-setting,
12395 and was able to handle the requested size. For instance, if the
12396 target can only change buffer size between runs, this variable will
12397 not reflect the change until the next run starts. Use @code{tstatus}
12398 to get a report of the actual buffer size.
12402 @item set trace-user @var{text}
12403 @kindex set trace-user
12405 @item show trace-user
12406 @kindex show trace-user
12408 @item set trace-notes @var{text}
12409 @kindex set trace-notes
12410 Set the trace run's notes.
12412 @item show trace-notes
12413 @kindex show trace-notes
12414 Show the trace run's notes.
12416 @item set trace-stop-notes @var{text}
12417 @kindex set trace-stop-notes
12418 Set the trace run's stop notes. The handling of the note is as for
12419 @code{tstop} arguments; the set command is convenient way to fix a
12420 stop note that is mistaken or incomplete.
12422 @item show trace-stop-notes
12423 @kindex show trace-stop-notes
12424 Show the trace run's stop notes.
12428 @node Tracepoint Restrictions
12429 @subsection Tracepoint Restrictions
12431 @cindex tracepoint restrictions
12432 There are a number of restrictions on the use of tracepoints. As
12433 described above, tracepoint data gathering occurs on the target
12434 without interaction from @value{GDBN}. Thus the full capabilities of
12435 the debugger are not available during data gathering, and then at data
12436 examination time, you will be limited by only having what was
12437 collected. The following items describe some common problems, but it
12438 is not exhaustive, and you may run into additional difficulties not
12444 Tracepoint expressions are intended to gather objects (lvalues). Thus
12445 the full flexibility of GDB's expression evaluator is not available.
12446 You cannot call functions, cast objects to aggregate types, access
12447 convenience variables or modify values (except by assignment to trace
12448 state variables). Some language features may implicitly call
12449 functions (for instance Objective-C fields with accessors), and therefore
12450 cannot be collected either.
12453 Collection of local variables, either individually or in bulk with
12454 @code{$locals} or @code{$args}, during @code{while-stepping} may
12455 behave erratically. The stepping action may enter a new scope (for
12456 instance by stepping into a function), or the location of the variable
12457 may change (for instance it is loaded into a register). The
12458 tracepoint data recorded uses the location information for the
12459 variables that is correct for the tracepoint location. When the
12460 tracepoint is created, it is not possible, in general, to determine
12461 where the steps of a @code{while-stepping} sequence will advance the
12462 program---particularly if a conditional branch is stepped.
12465 Collection of an incompletely-initialized or partially-destroyed object
12466 may result in something that @value{GDBN} cannot display, or displays
12467 in a misleading way.
12470 When @value{GDBN} displays a pointer to character it automatically
12471 dereferences the pointer to also display characters of the string
12472 being pointed to. However, collecting the pointer during tracing does
12473 not automatically collect the string. You need to explicitly
12474 dereference the pointer and provide size information if you want to
12475 collect not only the pointer, but the memory pointed to. For example,
12476 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12480 It is not possible to collect a complete stack backtrace at a
12481 tracepoint. Instead, you may collect the registers and a few hundred
12482 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12483 (adjust to use the name of the actual stack pointer register on your
12484 target architecture, and the amount of stack you wish to capture).
12485 Then the @code{backtrace} command will show a partial backtrace when
12486 using a trace frame. The number of stack frames that can be examined
12487 depends on the sizes of the frames in the collected stack. Note that
12488 if you ask for a block so large that it goes past the bottom of the
12489 stack, the target agent may report an error trying to read from an
12493 If you do not collect registers at a tracepoint, @value{GDBN} can
12494 infer that the value of @code{$pc} must be the same as the address of
12495 the tracepoint and use that when you are looking at a trace frame
12496 for that tracepoint. However, this cannot work if the tracepoint has
12497 multiple locations (for instance if it was set in a function that was
12498 inlined), or if it has a @code{while-stepping} loop. In those cases
12499 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12504 @node Analyze Collected Data
12505 @section Using the Collected Data
12507 After the tracepoint experiment ends, you use @value{GDBN} commands
12508 for examining the trace data. The basic idea is that each tracepoint
12509 collects a trace @dfn{snapshot} every time it is hit and another
12510 snapshot every time it single-steps. All these snapshots are
12511 consecutively numbered from zero and go into a buffer, and you can
12512 examine them later. The way you examine them is to @dfn{focus} on a
12513 specific trace snapshot. When the remote stub is focused on a trace
12514 snapshot, it will respond to all @value{GDBN} requests for memory and
12515 registers by reading from the buffer which belongs to that snapshot,
12516 rather than from @emph{real} memory or registers of the program being
12517 debugged. This means that @strong{all} @value{GDBN} commands
12518 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12519 behave as if we were currently debugging the program state as it was
12520 when the tracepoint occurred. Any requests for data that are not in
12521 the buffer will fail.
12524 * tfind:: How to select a trace snapshot
12525 * tdump:: How to display all data for a snapshot
12526 * save tracepoints:: How to save tracepoints for a future run
12530 @subsection @code{tfind @var{n}}
12533 @cindex select trace snapshot
12534 @cindex find trace snapshot
12535 The basic command for selecting a trace snapshot from the buffer is
12536 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12537 counting from zero. If no argument @var{n} is given, the next
12538 snapshot is selected.
12540 Here are the various forms of using the @code{tfind} command.
12544 Find the first snapshot in the buffer. This is a synonym for
12545 @code{tfind 0} (since 0 is the number of the first snapshot).
12548 Stop debugging trace snapshots, resume @emph{live} debugging.
12551 Same as @samp{tfind none}.
12554 No argument means find the next trace snapshot.
12557 Find the previous trace snapshot before the current one. This permits
12558 retracing earlier steps.
12560 @item tfind tracepoint @var{num}
12561 Find the next snapshot associated with tracepoint @var{num}. Search
12562 proceeds forward from the last examined trace snapshot. If no
12563 argument @var{num} is given, it means find the next snapshot collected
12564 for the same tracepoint as the current snapshot.
12566 @item tfind pc @var{addr}
12567 Find the next snapshot associated with the value @var{addr} of the
12568 program counter. Search proceeds forward from the last examined trace
12569 snapshot. If no argument @var{addr} is given, it means find the next
12570 snapshot with the same value of PC as the current snapshot.
12572 @item tfind outside @var{addr1}, @var{addr2}
12573 Find the next snapshot whose PC is outside the given range of
12574 addresses (exclusive).
12576 @item tfind range @var{addr1}, @var{addr2}
12577 Find the next snapshot whose PC is between @var{addr1} and
12578 @var{addr2} (inclusive).
12580 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12581 Find the next snapshot associated with the source line @var{n}. If
12582 the optional argument @var{file} is given, refer to line @var{n} in
12583 that source file. Search proceeds forward from the last examined
12584 trace snapshot. If no argument @var{n} is given, it means find the
12585 next line other than the one currently being examined; thus saying
12586 @code{tfind line} repeatedly can appear to have the same effect as
12587 stepping from line to line in a @emph{live} debugging session.
12590 The default arguments for the @code{tfind} commands are specifically
12591 designed to make it easy to scan through the trace buffer. For
12592 instance, @code{tfind} with no argument selects the next trace
12593 snapshot, and @code{tfind -} with no argument selects the previous
12594 trace snapshot. So, by giving one @code{tfind} command, and then
12595 simply hitting @key{RET} repeatedly you can examine all the trace
12596 snapshots in order. Or, by saying @code{tfind -} and then hitting
12597 @key{RET} repeatedly you can examine the snapshots in reverse order.
12598 The @code{tfind line} command with no argument selects the snapshot
12599 for the next source line executed. The @code{tfind pc} command with
12600 no argument selects the next snapshot with the same program counter
12601 (PC) as the current frame. The @code{tfind tracepoint} command with
12602 no argument selects the next trace snapshot collected by the same
12603 tracepoint as the current one.
12605 In addition to letting you scan through the trace buffer manually,
12606 these commands make it easy to construct @value{GDBN} scripts that
12607 scan through the trace buffer and print out whatever collected data
12608 you are interested in. Thus, if we want to examine the PC, FP, and SP
12609 registers from each trace frame in the buffer, we can say this:
12612 (@value{GDBP}) @b{tfind start}
12613 (@value{GDBP}) @b{while ($trace_frame != -1)}
12614 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12615 $trace_frame, $pc, $sp, $fp
12619 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12620 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12621 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12622 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12623 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12624 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12625 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12626 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12627 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12628 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12629 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12632 Or, if we want to examine the variable @code{X} at each source line in
12636 (@value{GDBP}) @b{tfind start}
12637 (@value{GDBP}) @b{while ($trace_frame != -1)}
12638 > printf "Frame %d, X == %d\n", $trace_frame, X
12648 @subsection @code{tdump}
12650 @cindex dump all data collected at tracepoint
12651 @cindex tracepoint data, display
12653 This command takes no arguments. It prints all the data collected at
12654 the current trace snapshot.
12657 (@value{GDBP}) @b{trace 444}
12658 (@value{GDBP}) @b{actions}
12659 Enter actions for tracepoint #2, one per line:
12660 > collect $regs, $locals, $args, gdb_long_test
12663 (@value{GDBP}) @b{tstart}
12665 (@value{GDBP}) @b{tfind line 444}
12666 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12668 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12670 (@value{GDBP}) @b{tdump}
12671 Data collected at tracepoint 2, trace frame 1:
12672 d0 0xc4aa0085 -995491707
12676 d4 0x71aea3d 119204413
12679 d7 0x380035 3670069
12680 a0 0x19e24a 1696330
12681 a1 0x3000668 50333288
12683 a3 0x322000 3284992
12684 a4 0x3000698 50333336
12685 a5 0x1ad3cc 1758156
12686 fp 0x30bf3c 0x30bf3c
12687 sp 0x30bf34 0x30bf34
12689 pc 0x20b2c8 0x20b2c8
12693 p = 0x20e5b4 "gdb-test"
12700 gdb_long_test = 17 '\021'
12705 @code{tdump} works by scanning the tracepoint's current collection
12706 actions and printing the value of each expression listed. So
12707 @code{tdump} can fail, if after a run, you change the tracepoint's
12708 actions to mention variables that were not collected during the run.
12710 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12711 uses the collected value of @code{$pc} to distinguish between trace
12712 frames that were collected at the tracepoint hit, and frames that were
12713 collected while stepping. This allows it to correctly choose whether
12714 to display the basic list of collections, or the collections from the
12715 body of the while-stepping loop. However, if @code{$pc} was not collected,
12716 then @code{tdump} will always attempt to dump using the basic collection
12717 list, and may fail if a while-stepping frame does not include all the
12718 same data that is collected at the tracepoint hit.
12719 @c This is getting pretty arcane, example would be good.
12721 @node save tracepoints
12722 @subsection @code{save tracepoints @var{filename}}
12723 @kindex save tracepoints
12724 @kindex save-tracepoints
12725 @cindex save tracepoints for future sessions
12727 This command saves all current tracepoint definitions together with
12728 their actions and passcounts, into a file @file{@var{filename}}
12729 suitable for use in a later debugging session. To read the saved
12730 tracepoint definitions, use the @code{source} command (@pxref{Command
12731 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12732 alias for @w{@code{save tracepoints}}
12734 @node Tracepoint Variables
12735 @section Convenience Variables for Tracepoints
12736 @cindex tracepoint variables
12737 @cindex convenience variables for tracepoints
12740 @vindex $trace_frame
12741 @item (int) $trace_frame
12742 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12743 snapshot is selected.
12745 @vindex $tracepoint
12746 @item (int) $tracepoint
12747 The tracepoint for the current trace snapshot.
12749 @vindex $trace_line
12750 @item (int) $trace_line
12751 The line number for the current trace snapshot.
12753 @vindex $trace_file
12754 @item (char []) $trace_file
12755 The source file for the current trace snapshot.
12757 @vindex $trace_func
12758 @item (char []) $trace_func
12759 The name of the function containing @code{$tracepoint}.
12762 Note: @code{$trace_file} is not suitable for use in @code{printf},
12763 use @code{output} instead.
12765 Here's a simple example of using these convenience variables for
12766 stepping through all the trace snapshots and printing some of their
12767 data. Note that these are not the same as trace state variables,
12768 which are managed by the target.
12771 (@value{GDBP}) @b{tfind start}
12773 (@value{GDBP}) @b{while $trace_frame != -1}
12774 > output $trace_file
12775 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12781 @section Using Trace Files
12782 @cindex trace files
12784 In some situations, the target running a trace experiment may no
12785 longer be available; perhaps it crashed, or the hardware was needed
12786 for a different activity. To handle these cases, you can arrange to
12787 dump the trace data into a file, and later use that file as a source
12788 of trace data, via the @code{target tfile} command.
12793 @item tsave [ -r ] @var{filename}
12794 @itemx tsave [-ctf] @var{dirname}
12795 Save the trace data to @var{filename}. By default, this command
12796 assumes that @var{filename} refers to the host filesystem, so if
12797 necessary @value{GDBN} will copy raw trace data up from the target and
12798 then save it. If the target supports it, you can also supply the
12799 optional argument @code{-r} (``remote'') to direct the target to save
12800 the data directly into @var{filename} in its own filesystem, which may be
12801 more efficient if the trace buffer is very large. (Note, however, that
12802 @code{target tfile} can only read from files accessible to the host.)
12803 By default, this command will save trace frame in tfile format.
12804 You can supply the optional argument @code{-ctf} to save date in CTF
12805 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12806 that can be shared by multiple debugging and tracing tools. Please go to
12807 @indicateurl{http://www.efficios.com/ctf} to get more information.
12809 @kindex target tfile
12813 @item target tfile @var{filename}
12814 @itemx target ctf @var{dirname}
12815 Use the file named @var{filename} or directory named @var{dirname} as
12816 a source of trace data. Commands that examine data work as they do with
12817 a live target, but it is not possible to run any new trace experiments.
12818 @code{tstatus} will report the state of the trace run at the moment
12819 the data was saved, as well as the current trace frame you are examining.
12820 @var{filename} or @var{dirname} must be on a filesystem accessible to
12824 (@value{GDBP}) target ctf ctf.ctf
12825 (@value{GDBP}) tfind
12826 Found trace frame 0, tracepoint 2
12827 39 ++a; /* set tracepoint 1 here */
12828 (@value{GDBP}) tdump
12829 Data collected at tracepoint 2, trace frame 0:
12833 c = @{"123", "456", "789", "123", "456", "789"@}
12834 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12842 @chapter Debugging Programs That Use Overlays
12845 If your program is too large to fit completely in your target system's
12846 memory, you can sometimes use @dfn{overlays} to work around this
12847 problem. @value{GDBN} provides some support for debugging programs that
12851 * How Overlays Work:: A general explanation of overlays.
12852 * Overlay Commands:: Managing overlays in @value{GDBN}.
12853 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12854 mapped by asking the inferior.
12855 * Overlay Sample Program:: A sample program using overlays.
12858 @node How Overlays Work
12859 @section How Overlays Work
12860 @cindex mapped overlays
12861 @cindex unmapped overlays
12862 @cindex load address, overlay's
12863 @cindex mapped address
12864 @cindex overlay area
12866 Suppose you have a computer whose instruction address space is only 64
12867 kilobytes long, but which has much more memory which can be accessed by
12868 other means: special instructions, segment registers, or memory
12869 management hardware, for example. Suppose further that you want to
12870 adapt a program which is larger than 64 kilobytes to run on this system.
12872 One solution is to identify modules of your program which are relatively
12873 independent, and need not call each other directly; call these modules
12874 @dfn{overlays}. Separate the overlays from the main program, and place
12875 their machine code in the larger memory. Place your main program in
12876 instruction memory, but leave at least enough space there to hold the
12877 largest overlay as well.
12879 Now, to call a function located in an overlay, you must first copy that
12880 overlay's machine code from the large memory into the space set aside
12881 for it in the instruction memory, and then jump to its entry point
12884 @c NB: In the below the mapped area's size is greater or equal to the
12885 @c size of all overlays. This is intentional to remind the developer
12886 @c that overlays don't necessarily need to be the same size.
12890 Data Instruction Larger
12891 Address Space Address Space Address Space
12892 +-----------+ +-----------+ +-----------+
12894 +-----------+ +-----------+ +-----------+<-- overlay 1
12895 | program | | main | .----| overlay 1 | load address
12896 | variables | | program | | +-----------+
12897 | and heap | | | | | |
12898 +-----------+ | | | +-----------+<-- overlay 2
12899 | | +-----------+ | | | load address
12900 +-----------+ | | | .-| overlay 2 |
12902 mapped --->+-----------+ | | +-----------+
12903 address | | | | | |
12904 | overlay | <-' | | |
12905 | area | <---' +-----------+<-- overlay 3
12906 | | <---. | | load address
12907 +-----------+ `--| overlay 3 |
12914 @anchor{A code overlay}A code overlay
12918 The diagram (@pxref{A code overlay}) shows a system with separate data
12919 and instruction address spaces. To map an overlay, the program copies
12920 its code from the larger address space to the instruction address space.
12921 Since the overlays shown here all use the same mapped address, only one
12922 may be mapped at a time. For a system with a single address space for
12923 data and instructions, the diagram would be similar, except that the
12924 program variables and heap would share an address space with the main
12925 program and the overlay area.
12927 An overlay loaded into instruction memory and ready for use is called a
12928 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12929 instruction memory. An overlay not present (or only partially present)
12930 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12931 is its address in the larger memory. The mapped address is also called
12932 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12933 called the @dfn{load memory address}, or @dfn{LMA}.
12935 Unfortunately, overlays are not a completely transparent way to adapt a
12936 program to limited instruction memory. They introduce a new set of
12937 global constraints you must keep in mind as you design your program:
12942 Before calling or returning to a function in an overlay, your program
12943 must make sure that overlay is actually mapped. Otherwise, the call or
12944 return will transfer control to the right address, but in the wrong
12945 overlay, and your program will probably crash.
12948 If the process of mapping an overlay is expensive on your system, you
12949 will need to choose your overlays carefully to minimize their effect on
12950 your program's performance.
12953 The executable file you load onto your system must contain each
12954 overlay's instructions, appearing at the overlay's load address, not its
12955 mapped address. However, each overlay's instructions must be relocated
12956 and its symbols defined as if the overlay were at its mapped address.
12957 You can use GNU linker scripts to specify different load and relocation
12958 addresses for pieces of your program; see @ref{Overlay Description,,,
12959 ld.info, Using ld: the GNU linker}.
12962 The procedure for loading executable files onto your system must be able
12963 to load their contents into the larger address space as well as the
12964 instruction and data spaces.
12968 The overlay system described above is rather simple, and could be
12969 improved in many ways:
12974 If your system has suitable bank switch registers or memory management
12975 hardware, you could use those facilities to make an overlay's load area
12976 contents simply appear at their mapped address in instruction space.
12977 This would probably be faster than copying the overlay to its mapped
12978 area in the usual way.
12981 If your overlays are small enough, you could set aside more than one
12982 overlay area, and have more than one overlay mapped at a time.
12985 You can use overlays to manage data, as well as instructions. In
12986 general, data overlays are even less transparent to your design than
12987 code overlays: whereas code overlays only require care when you call or
12988 return to functions, data overlays require care every time you access
12989 the data. Also, if you change the contents of a data overlay, you
12990 must copy its contents back out to its load address before you can copy a
12991 different data overlay into the same mapped area.
12996 @node Overlay Commands
12997 @section Overlay Commands
12999 To use @value{GDBN}'s overlay support, each overlay in your program must
13000 correspond to a separate section of the executable file. The section's
13001 virtual memory address and load memory address must be the overlay's
13002 mapped and load addresses. Identifying overlays with sections allows
13003 @value{GDBN} to determine the appropriate address of a function or
13004 variable, depending on whether the overlay is mapped or not.
13006 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13007 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13012 Disable @value{GDBN}'s overlay support. When overlay support is
13013 disabled, @value{GDBN} assumes that all functions and variables are
13014 always present at their mapped addresses. By default, @value{GDBN}'s
13015 overlay support is disabled.
13017 @item overlay manual
13018 @cindex manual overlay debugging
13019 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13020 relies on you to tell it which overlays are mapped, and which are not,
13021 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13022 commands described below.
13024 @item overlay map-overlay @var{overlay}
13025 @itemx overlay map @var{overlay}
13026 @cindex map an overlay
13027 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13028 be the name of the object file section containing the overlay. When an
13029 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13030 functions and variables at their mapped addresses. @value{GDBN} assumes
13031 that any other overlays whose mapped ranges overlap that of
13032 @var{overlay} are now unmapped.
13034 @item overlay unmap-overlay @var{overlay}
13035 @itemx overlay unmap @var{overlay}
13036 @cindex unmap an overlay
13037 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13038 must be the name of the object file section containing the overlay.
13039 When an overlay is unmapped, @value{GDBN} assumes it can find the
13040 overlay's functions and variables at their load addresses.
13043 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13044 consults a data structure the overlay manager maintains in the inferior
13045 to see which overlays are mapped. For details, see @ref{Automatic
13046 Overlay Debugging}.
13048 @item overlay load-target
13049 @itemx overlay load
13050 @cindex reloading the overlay table
13051 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13052 re-reads the table @value{GDBN} automatically each time the inferior
13053 stops, so this command should only be necessary if you have changed the
13054 overlay mapping yourself using @value{GDBN}. This command is only
13055 useful when using automatic overlay debugging.
13057 @item overlay list-overlays
13058 @itemx overlay list
13059 @cindex listing mapped overlays
13060 Display a list of the overlays currently mapped, along with their mapped
13061 addresses, load addresses, and sizes.
13065 Normally, when @value{GDBN} prints a code address, it includes the name
13066 of the function the address falls in:
13069 (@value{GDBP}) print main
13070 $3 = @{int ()@} 0x11a0 <main>
13073 When overlay debugging is enabled, @value{GDBN} recognizes code in
13074 unmapped overlays, and prints the names of unmapped functions with
13075 asterisks around them. For example, if @code{foo} is a function in an
13076 unmapped overlay, @value{GDBN} prints it this way:
13079 (@value{GDBP}) overlay list
13080 No sections are mapped.
13081 (@value{GDBP}) print foo
13082 $5 = @{int (int)@} 0x100000 <*foo*>
13085 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13089 (@value{GDBP}) overlay list
13090 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13091 mapped at 0x1016 - 0x104a
13092 (@value{GDBP}) print foo
13093 $6 = @{int (int)@} 0x1016 <foo>
13096 When overlay debugging is enabled, @value{GDBN} can find the correct
13097 address for functions and variables in an overlay, whether or not the
13098 overlay is mapped. This allows most @value{GDBN} commands, like
13099 @code{break} and @code{disassemble}, to work normally, even on unmapped
13100 code. However, @value{GDBN}'s breakpoint support has some limitations:
13104 @cindex breakpoints in overlays
13105 @cindex overlays, setting breakpoints in
13106 You can set breakpoints in functions in unmapped overlays, as long as
13107 @value{GDBN} can write to the overlay at its load address.
13109 @value{GDBN} can not set hardware or simulator-based breakpoints in
13110 unmapped overlays. However, if you set a breakpoint at the end of your
13111 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13112 you are using manual overlay management), @value{GDBN} will re-set its
13113 breakpoints properly.
13117 @node Automatic Overlay Debugging
13118 @section Automatic Overlay Debugging
13119 @cindex automatic overlay debugging
13121 @value{GDBN} can automatically track which overlays are mapped and which
13122 are not, given some simple co-operation from the overlay manager in the
13123 inferior. If you enable automatic overlay debugging with the
13124 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13125 looks in the inferior's memory for certain variables describing the
13126 current state of the overlays.
13128 Here are the variables your overlay manager must define to support
13129 @value{GDBN}'s automatic overlay debugging:
13133 @item @code{_ovly_table}:
13134 This variable must be an array of the following structures:
13139 /* The overlay's mapped address. */
13142 /* The size of the overlay, in bytes. */
13143 unsigned long size;
13145 /* The overlay's load address. */
13148 /* Non-zero if the overlay is currently mapped;
13150 unsigned long mapped;
13154 @item @code{_novlys}:
13155 This variable must be a four-byte signed integer, holding the total
13156 number of elements in @code{_ovly_table}.
13160 To decide whether a particular overlay is mapped or not, @value{GDBN}
13161 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13162 @code{lma} members equal the VMA and LMA of the overlay's section in the
13163 executable file. When @value{GDBN} finds a matching entry, it consults
13164 the entry's @code{mapped} member to determine whether the overlay is
13167 In addition, your overlay manager may define a function called
13168 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13169 will silently set a breakpoint there. If the overlay manager then
13170 calls this function whenever it has changed the overlay table, this
13171 will enable @value{GDBN} to accurately keep track of which overlays
13172 are in program memory, and update any breakpoints that may be set
13173 in overlays. This will allow breakpoints to work even if the
13174 overlays are kept in ROM or other non-writable memory while they
13175 are not being executed.
13177 @node Overlay Sample Program
13178 @section Overlay Sample Program
13179 @cindex overlay example program
13181 When linking a program which uses overlays, you must place the overlays
13182 at their load addresses, while relocating them to run at their mapped
13183 addresses. To do this, you must write a linker script (@pxref{Overlay
13184 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13185 since linker scripts are specific to a particular host system, target
13186 architecture, and target memory layout, this manual cannot provide
13187 portable sample code demonstrating @value{GDBN}'s overlay support.
13189 However, the @value{GDBN} source distribution does contain an overlaid
13190 program, with linker scripts for a few systems, as part of its test
13191 suite. The program consists of the following files from
13192 @file{gdb/testsuite/gdb.base}:
13196 The main program file.
13198 A simple overlay manager, used by @file{overlays.c}.
13203 Overlay modules, loaded and used by @file{overlays.c}.
13206 Linker scripts for linking the test program on the @code{d10v-elf}
13207 and @code{m32r-elf} targets.
13210 You can build the test program using the @code{d10v-elf} GCC
13211 cross-compiler like this:
13214 $ d10v-elf-gcc -g -c overlays.c
13215 $ d10v-elf-gcc -g -c ovlymgr.c
13216 $ d10v-elf-gcc -g -c foo.c
13217 $ d10v-elf-gcc -g -c bar.c
13218 $ d10v-elf-gcc -g -c baz.c
13219 $ d10v-elf-gcc -g -c grbx.c
13220 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13221 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13224 The build process is identical for any other architecture, except that
13225 you must substitute the appropriate compiler and linker script for the
13226 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13230 @chapter Using @value{GDBN} with Different Languages
13233 Although programming languages generally have common aspects, they are
13234 rarely expressed in the same manner. For instance, in ANSI C,
13235 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13236 Modula-2, it is accomplished by @code{p^}. Values can also be
13237 represented (and displayed) differently. Hex numbers in C appear as
13238 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13240 @cindex working language
13241 Language-specific information is built into @value{GDBN} for some languages,
13242 allowing you to express operations like the above in your program's
13243 native language, and allowing @value{GDBN} to output values in a manner
13244 consistent with the syntax of your program's native language. The
13245 language you use to build expressions is called the @dfn{working
13249 * Setting:: Switching between source languages
13250 * Show:: Displaying the language
13251 * Checks:: Type and range checks
13252 * Supported Languages:: Supported languages
13253 * Unsupported Languages:: Unsupported languages
13257 @section Switching Between Source Languages
13259 There are two ways to control the working language---either have @value{GDBN}
13260 set it automatically, or select it manually yourself. You can use the
13261 @code{set language} command for either purpose. On startup, @value{GDBN}
13262 defaults to setting the language automatically. The working language is
13263 used to determine how expressions you type are interpreted, how values
13266 In addition to the working language, every source file that
13267 @value{GDBN} knows about has its own working language. For some object
13268 file formats, the compiler might indicate which language a particular
13269 source file is in. However, most of the time @value{GDBN} infers the
13270 language from the name of the file. The language of a source file
13271 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13272 show each frame appropriately for its own language. There is no way to
13273 set the language of a source file from within @value{GDBN}, but you can
13274 set the language associated with a filename extension. @xref{Show, ,
13275 Displaying the Language}.
13277 This is most commonly a problem when you use a program, such
13278 as @code{cfront} or @code{f2c}, that generates C but is written in
13279 another language. In that case, make the
13280 program use @code{#line} directives in its C output; that way
13281 @value{GDBN} will know the correct language of the source code of the original
13282 program, and will display that source code, not the generated C code.
13285 * Filenames:: Filename extensions and languages.
13286 * Manually:: Setting the working language manually
13287 * Automatically:: Having @value{GDBN} infer the source language
13291 @subsection List of Filename Extensions and Languages
13293 If a source file name ends in one of the following extensions, then
13294 @value{GDBN} infers that its language is the one indicated.
13312 C@t{++} source file
13318 Objective-C source file
13322 Fortran source file
13325 Modula-2 source file
13329 Assembler source file. This actually behaves almost like C, but
13330 @value{GDBN} does not skip over function prologues when stepping.
13333 In addition, you may set the language associated with a filename
13334 extension. @xref{Show, , Displaying the Language}.
13337 @subsection Setting the Working Language
13339 If you allow @value{GDBN} to set the language automatically,
13340 expressions are interpreted the same way in your debugging session and
13343 @kindex set language
13344 If you wish, you may set the language manually. To do this, issue the
13345 command @samp{set language @var{lang}}, where @var{lang} is the name of
13346 a language, such as
13347 @code{c} or @code{modula-2}.
13348 For a list of the supported languages, type @samp{set language}.
13350 Setting the language manually prevents @value{GDBN} from updating the working
13351 language automatically. This can lead to confusion if you try
13352 to debug a program when the working language is not the same as the
13353 source language, when an expression is acceptable to both
13354 languages---but means different things. For instance, if the current
13355 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13363 might not have the effect you intended. In C, this means to add
13364 @code{b} and @code{c} and place the result in @code{a}. The result
13365 printed would be the value of @code{a}. In Modula-2, this means to compare
13366 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13368 @node Automatically
13369 @subsection Having @value{GDBN} Infer the Source Language
13371 To have @value{GDBN} set the working language automatically, use
13372 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13373 then infers the working language. That is, when your program stops in a
13374 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13375 working language to the language recorded for the function in that
13376 frame. If the language for a frame is unknown (that is, if the function
13377 or block corresponding to the frame was defined in a source file that
13378 does not have a recognized extension), the current working language is
13379 not changed, and @value{GDBN} issues a warning.
13381 This may not seem necessary for most programs, which are written
13382 entirely in one source language. However, program modules and libraries
13383 written in one source language can be used by a main program written in
13384 a different source language. Using @samp{set language auto} in this
13385 case frees you from having to set the working language manually.
13388 @section Displaying the Language
13390 The following commands help you find out which language is the
13391 working language, and also what language source files were written in.
13394 @item show language
13395 @anchor{show language}
13396 @kindex show language
13397 Display the current working language. This is the
13398 language you can use with commands such as @code{print} to
13399 build and compute expressions that may involve variables in your program.
13402 @kindex info frame@r{, show the source language}
13403 Display the source language for this frame. This language becomes the
13404 working language if you use an identifier from this frame.
13405 @xref{Frame Info, ,Information about a Frame}, to identify the other
13406 information listed here.
13409 @kindex info source@r{, show the source language}
13410 Display the source language of this source file.
13411 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13412 information listed here.
13415 In unusual circumstances, you may have source files with extensions
13416 not in the standard list. You can then set the extension associated
13417 with a language explicitly:
13420 @item set extension-language @var{ext} @var{language}
13421 @kindex set extension-language
13422 Tell @value{GDBN} that source files with extension @var{ext} are to be
13423 assumed as written in the source language @var{language}.
13425 @item info extensions
13426 @kindex info extensions
13427 List all the filename extensions and the associated languages.
13431 @section Type and Range Checking
13433 Some languages are designed to guard you against making seemingly common
13434 errors through a series of compile- and run-time checks. These include
13435 checking the type of arguments to functions and operators and making
13436 sure mathematical overflows are caught at run time. Checks such as
13437 these help to ensure a program's correctness once it has been compiled
13438 by eliminating type mismatches and providing active checks for range
13439 errors when your program is running.
13441 By default @value{GDBN} checks for these errors according to the
13442 rules of the current source language. Although @value{GDBN} does not check
13443 the statements in your program, it can check expressions entered directly
13444 into @value{GDBN} for evaluation via the @code{print} command, for example.
13447 * Type Checking:: An overview of type checking
13448 * Range Checking:: An overview of range checking
13451 @cindex type checking
13452 @cindex checks, type
13453 @node Type Checking
13454 @subsection An Overview of Type Checking
13456 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13457 arguments to operators and functions have to be of the correct type,
13458 otherwise an error occurs. These checks prevent type mismatch
13459 errors from ever causing any run-time problems. For example,
13462 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13464 (@value{GDBP}) print obj.my_method (0)
13467 (@value{GDBP}) print obj.my_method (0x1234)
13468 Cannot resolve method klass::my_method to any overloaded instance
13471 The second example fails because in C@t{++} the integer constant
13472 @samp{0x1234} is not type-compatible with the pointer parameter type.
13474 For the expressions you use in @value{GDBN} commands, you can tell
13475 @value{GDBN} to not enforce strict type checking or
13476 to treat any mismatches as errors and abandon the expression;
13477 When type checking is disabled, @value{GDBN} successfully evaluates
13478 expressions like the second example above.
13480 Even if type checking is off, there may be other reasons
13481 related to type that prevent @value{GDBN} from evaluating an expression.
13482 For instance, @value{GDBN} does not know how to add an @code{int} and
13483 a @code{struct foo}. These particular type errors have nothing to do
13484 with the language in use and usually arise from expressions which make
13485 little sense to evaluate anyway.
13487 @value{GDBN} provides some additional commands for controlling type checking:
13489 @kindex set check type
13490 @kindex show check type
13492 @item set check type on
13493 @itemx set check type off
13494 Set strict type checking on or off. If any type mismatches occur in
13495 evaluating an expression while type checking is on, @value{GDBN} prints a
13496 message and aborts evaluation of the expression.
13498 @item show check type
13499 Show the current setting of type checking and whether @value{GDBN}
13500 is enforcing strict type checking rules.
13503 @cindex range checking
13504 @cindex checks, range
13505 @node Range Checking
13506 @subsection An Overview of Range Checking
13508 In some languages (such as Modula-2), it is an error to exceed the
13509 bounds of a type; this is enforced with run-time checks. Such range
13510 checking is meant to ensure program correctness by making sure
13511 computations do not overflow, or indices on an array element access do
13512 not exceed the bounds of the array.
13514 For expressions you use in @value{GDBN} commands, you can tell
13515 @value{GDBN} to treat range errors in one of three ways: ignore them,
13516 always treat them as errors and abandon the expression, or issue
13517 warnings but evaluate the expression anyway.
13519 A range error can result from numerical overflow, from exceeding an
13520 array index bound, or when you type a constant that is not a member
13521 of any type. Some languages, however, do not treat overflows as an
13522 error. In many implementations of C, mathematical overflow causes the
13523 result to ``wrap around'' to lower values---for example, if @var{m} is
13524 the largest integer value, and @var{s} is the smallest, then
13527 @var{m} + 1 @result{} @var{s}
13530 This, too, is specific to individual languages, and in some cases
13531 specific to individual compilers or machines. @xref{Supported Languages, ,
13532 Supported Languages}, for further details on specific languages.
13534 @value{GDBN} provides some additional commands for controlling the range checker:
13536 @kindex set check range
13537 @kindex show check range
13539 @item set check range auto
13540 Set range checking on or off based on the current working language.
13541 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13544 @item set check range on
13545 @itemx set check range off
13546 Set range checking on or off, overriding the default setting for the
13547 current working language. A warning is issued if the setting does not
13548 match the language default. If a range error occurs and range checking is on,
13549 then a message is printed and evaluation of the expression is aborted.
13551 @item set check range warn
13552 Output messages when the @value{GDBN} range checker detects a range error,
13553 but attempt to evaluate the expression anyway. Evaluating the
13554 expression may still be impossible for other reasons, such as accessing
13555 memory that the process does not own (a typical example from many Unix
13559 Show the current setting of the range checker, and whether or not it is
13560 being set automatically by @value{GDBN}.
13563 @node Supported Languages
13564 @section Supported Languages
13566 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13567 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13568 @c This is false ...
13569 Some @value{GDBN} features may be used in expressions regardless of the
13570 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13571 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13572 ,Expressions}) can be used with the constructs of any supported
13575 The following sections detail to what degree each source language is
13576 supported by @value{GDBN}. These sections are not meant to be language
13577 tutorials or references, but serve only as a reference guide to what the
13578 @value{GDBN} expression parser accepts, and what input and output
13579 formats should look like for different languages. There are many good
13580 books written on each of these languages; please look to these for a
13581 language reference or tutorial.
13584 * C:: C and C@t{++}
13587 * Objective-C:: Objective-C
13588 * OpenCL C:: OpenCL C
13589 * Fortran:: Fortran
13591 * Modula-2:: Modula-2
13596 @subsection C and C@t{++}
13598 @cindex C and C@t{++}
13599 @cindex expressions in C or C@t{++}
13601 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13602 to both languages. Whenever this is the case, we discuss those languages
13606 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13607 @cindex @sc{gnu} C@t{++}
13608 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13609 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13610 effectively, you must compile your C@t{++} programs with a supported
13611 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13612 compiler (@code{aCC}).
13615 * C Operators:: C and C@t{++} operators
13616 * C Constants:: C and C@t{++} constants
13617 * C Plus Plus Expressions:: C@t{++} expressions
13618 * C Defaults:: Default settings for C and C@t{++}
13619 * C Checks:: C and C@t{++} type and range checks
13620 * Debugging C:: @value{GDBN} and C
13621 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13622 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13626 @subsubsection C and C@t{++} Operators
13628 @cindex C and C@t{++} operators
13630 Operators must be defined on values of specific types. For instance,
13631 @code{+} is defined on numbers, but not on structures. Operators are
13632 often defined on groups of types.
13634 For the purposes of C and C@t{++}, the following definitions hold:
13639 @emph{Integral types} include @code{int} with any of its storage-class
13640 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13643 @emph{Floating-point types} include @code{float}, @code{double}, and
13644 @code{long double} (if supported by the target platform).
13647 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13650 @emph{Scalar types} include all of the above.
13655 The following operators are supported. They are listed here
13656 in order of increasing precedence:
13660 The comma or sequencing operator. Expressions in a comma-separated list
13661 are evaluated from left to right, with the result of the entire
13662 expression being the last expression evaluated.
13665 Assignment. The value of an assignment expression is the value
13666 assigned. Defined on scalar types.
13669 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13670 and translated to @w{@code{@var{a} = @var{a op b}}}.
13671 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13672 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13673 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13676 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13677 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13681 Logical @sc{or}. Defined on integral types.
13684 Logical @sc{and}. Defined on integral types.
13687 Bitwise @sc{or}. Defined on integral types.
13690 Bitwise exclusive-@sc{or}. Defined on integral types.
13693 Bitwise @sc{and}. Defined on integral types.
13696 Equality and inequality. Defined on scalar types. The value of these
13697 expressions is 0 for false and non-zero for true.
13699 @item <@r{, }>@r{, }<=@r{, }>=
13700 Less than, greater than, less than or equal, greater than or equal.
13701 Defined on scalar types. The value of these expressions is 0 for false
13702 and non-zero for true.
13705 left shift, and right shift. Defined on integral types.
13708 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13711 Addition and subtraction. Defined on integral types, floating-point types and
13714 @item *@r{, }/@r{, }%
13715 Multiplication, division, and modulus. Multiplication and division are
13716 defined on integral and floating-point types. Modulus is defined on
13720 Increment and decrement. When appearing before a variable, the
13721 operation is performed before the variable is used in an expression;
13722 when appearing after it, the variable's value is used before the
13723 operation takes place.
13726 Pointer dereferencing. Defined on pointer types. Same precedence as
13730 Address operator. Defined on variables. Same precedence as @code{++}.
13732 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13733 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13734 to examine the address
13735 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13739 Negative. Defined on integral and floating-point types. Same
13740 precedence as @code{++}.
13743 Logical negation. Defined on integral types. Same precedence as
13747 Bitwise complement operator. Defined on integral types. Same precedence as
13752 Structure member, and pointer-to-structure member. For convenience,
13753 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13754 pointer based on the stored type information.
13755 Defined on @code{struct} and @code{union} data.
13758 Dereferences of pointers to members.
13761 Array indexing. @code{@var{a}[@var{i}]} is defined as
13762 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13765 Function parameter list. Same precedence as @code{->}.
13768 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13769 and @code{class} types.
13772 Doubled colons also represent the @value{GDBN} scope operator
13773 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13777 If an operator is redefined in the user code, @value{GDBN} usually
13778 attempts to invoke the redefined version instead of using the operator's
13779 predefined meaning.
13782 @subsubsection C and C@t{++} Constants
13784 @cindex C and C@t{++} constants
13786 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13791 Integer constants are a sequence of digits. Octal constants are
13792 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13793 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13794 @samp{l}, specifying that the constant should be treated as a
13798 Floating point constants are a sequence of digits, followed by a decimal
13799 point, followed by a sequence of digits, and optionally followed by an
13800 exponent. An exponent is of the form:
13801 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13802 sequence of digits. The @samp{+} is optional for positive exponents.
13803 A floating-point constant may also end with a letter @samp{f} or
13804 @samp{F}, specifying that the constant should be treated as being of
13805 the @code{float} (as opposed to the default @code{double}) type; or with
13806 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13810 Enumerated constants consist of enumerated identifiers, or their
13811 integral equivalents.
13814 Character constants are a single character surrounded by single quotes
13815 (@code{'}), or a number---the ordinal value of the corresponding character
13816 (usually its @sc{ascii} value). Within quotes, the single character may
13817 be represented by a letter or by @dfn{escape sequences}, which are of
13818 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13819 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13820 @samp{@var{x}} is a predefined special character---for example,
13821 @samp{\n} for newline.
13823 Wide character constants can be written by prefixing a character
13824 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13825 form of @samp{x}. The target wide character set is used when
13826 computing the value of this constant (@pxref{Character Sets}).
13829 String constants are a sequence of character constants surrounded by
13830 double quotes (@code{"}). Any valid character constant (as described
13831 above) may appear. Double quotes within the string must be preceded by
13832 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13835 Wide string constants can be written by prefixing a string constant
13836 with @samp{L}, as in C. The target wide character set is used when
13837 computing the value of this constant (@pxref{Character Sets}).
13840 Pointer constants are an integral value. You can also write pointers
13841 to constants using the C operator @samp{&}.
13844 Array constants are comma-separated lists surrounded by braces @samp{@{}
13845 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13846 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13847 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13850 @node C Plus Plus Expressions
13851 @subsubsection C@t{++} Expressions
13853 @cindex expressions in C@t{++}
13854 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13856 @cindex debugging C@t{++} programs
13857 @cindex C@t{++} compilers
13858 @cindex debug formats and C@t{++}
13859 @cindex @value{NGCC} and C@t{++}
13861 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13862 the proper compiler and the proper debug format. Currently,
13863 @value{GDBN} works best when debugging C@t{++} code that is compiled
13864 with the most recent version of @value{NGCC} possible. The DWARF
13865 debugging format is preferred; @value{NGCC} defaults to this on most
13866 popular platforms. Other compilers and/or debug formats are likely to
13867 work badly or not at all when using @value{GDBN} to debug C@t{++}
13868 code. @xref{Compilation}.
13873 @cindex member functions
13875 Member function calls are allowed; you can use expressions like
13878 count = aml->GetOriginal(x, y)
13881 @vindex this@r{, inside C@t{++} member functions}
13882 @cindex namespace in C@t{++}
13884 While a member function is active (in the selected stack frame), your
13885 expressions have the same namespace available as the member function;
13886 that is, @value{GDBN} allows implicit references to the class instance
13887 pointer @code{this} following the same rules as C@t{++}. @code{using}
13888 declarations in the current scope are also respected by @value{GDBN}.
13890 @cindex call overloaded functions
13891 @cindex overloaded functions, calling
13892 @cindex type conversions in C@t{++}
13894 You can call overloaded functions; @value{GDBN} resolves the function
13895 call to the right definition, with some restrictions. @value{GDBN} does not
13896 perform overload resolution involving user-defined type conversions,
13897 calls to constructors, or instantiations of templates that do not exist
13898 in the program. It also cannot handle ellipsis argument lists or
13901 It does perform integral conversions and promotions, floating-point
13902 promotions, arithmetic conversions, pointer conversions, conversions of
13903 class objects to base classes, and standard conversions such as those of
13904 functions or arrays to pointers; it requires an exact match on the
13905 number of function arguments.
13907 Overload resolution is always performed, unless you have specified
13908 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13909 ,@value{GDBN} Features for C@t{++}}.
13911 You must specify @code{set overload-resolution off} in order to use an
13912 explicit function signature to call an overloaded function, as in
13914 p 'foo(char,int)'('x', 13)
13917 The @value{GDBN} command-completion facility can simplify this;
13918 see @ref{Completion, ,Command Completion}.
13920 @cindex reference declarations
13922 @value{GDBN} understands variables declared as C@t{++} references; you can use
13923 them in expressions just as you do in C@t{++} source---they are automatically
13926 In the parameter list shown when @value{GDBN} displays a frame, the values of
13927 reference variables are not displayed (unlike other variables); this
13928 avoids clutter, since references are often used for large structures.
13929 The @emph{address} of a reference variable is always shown, unless
13930 you have specified @samp{set print address off}.
13933 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13934 expressions can use it just as expressions in your program do. Since
13935 one scope may be defined in another, you can use @code{::} repeatedly if
13936 necessary, for example in an expression like
13937 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13938 resolving name scope by reference to source files, in both C and C@t{++}
13939 debugging (@pxref{Variables, ,Program Variables}).
13942 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13947 @subsubsection C and C@t{++} Defaults
13949 @cindex C and C@t{++} defaults
13951 If you allow @value{GDBN} to set range checking automatically, it
13952 defaults to @code{off} whenever the working language changes to
13953 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13954 selects the working language.
13956 If you allow @value{GDBN} to set the language automatically, it
13957 recognizes source files whose names end with @file{.c}, @file{.C}, or
13958 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13959 these files, it sets the working language to C or C@t{++}.
13960 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13961 for further details.
13964 @subsubsection C and C@t{++} Type and Range Checks
13966 @cindex C and C@t{++} checks
13968 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13969 checking is used. However, if you turn type checking off, @value{GDBN}
13970 will allow certain non-standard conversions, such as promoting integer
13971 constants to pointers.
13973 Range checking, if turned on, is done on mathematical operations. Array
13974 indices are not checked, since they are often used to index a pointer
13975 that is not itself an array.
13978 @subsubsection @value{GDBN} and C
13980 The @code{set print union} and @code{show print union} commands apply to
13981 the @code{union} type. When set to @samp{on}, any @code{union} that is
13982 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13983 appears as @samp{@{...@}}.
13985 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13986 with pointers and a memory allocation function. @xref{Expressions,
13989 @node Debugging C Plus Plus
13990 @subsubsection @value{GDBN} Features for C@t{++}
13992 @cindex commands for C@t{++}
13994 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13995 designed specifically for use with C@t{++}. Here is a summary:
13998 @cindex break in overloaded functions
13999 @item @r{breakpoint menus}
14000 When you want a breakpoint in a function whose name is overloaded,
14001 @value{GDBN} has the capability to display a menu of possible breakpoint
14002 locations to help you specify which function definition you want.
14003 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14005 @cindex overloading in C@t{++}
14006 @item rbreak @var{regex}
14007 Setting breakpoints using regular expressions is helpful for setting
14008 breakpoints on overloaded functions that are not members of any special
14010 @xref{Set Breaks, ,Setting Breakpoints}.
14012 @cindex C@t{++} exception handling
14014 @itemx catch rethrow
14016 Debug C@t{++} exception handling using these commands. @xref{Set
14017 Catchpoints, , Setting Catchpoints}.
14019 @cindex inheritance
14020 @item ptype @var{typename}
14021 Print inheritance relationships as well as other information for type
14023 @xref{Symbols, ,Examining the Symbol Table}.
14025 @item info vtbl @var{expression}.
14026 The @code{info vtbl} command can be used to display the virtual
14027 method tables of the object computed by @var{expression}. This shows
14028 one entry per virtual table; there may be multiple virtual tables when
14029 multiple inheritance is in use.
14031 @cindex C@t{++} symbol display
14032 @item set print demangle
14033 @itemx show print demangle
14034 @itemx set print asm-demangle
14035 @itemx show print asm-demangle
14036 Control whether C@t{++} symbols display in their source form, both when
14037 displaying code as C@t{++} source and when displaying disassemblies.
14038 @xref{Print Settings, ,Print Settings}.
14040 @item set print object
14041 @itemx show print object
14042 Choose whether to print derived (actual) or declared types of objects.
14043 @xref{Print Settings, ,Print Settings}.
14045 @item set print vtbl
14046 @itemx show print vtbl
14047 Control the format for printing virtual function tables.
14048 @xref{Print Settings, ,Print Settings}.
14049 (The @code{vtbl} commands do not work on programs compiled with the HP
14050 ANSI C@t{++} compiler (@code{aCC}).)
14052 @kindex set overload-resolution
14053 @cindex overloaded functions, overload resolution
14054 @item set overload-resolution on
14055 Enable overload resolution for C@t{++} expression evaluation. The default
14056 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14057 and searches for a function whose signature matches the argument types,
14058 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14059 Expressions, ,C@t{++} Expressions}, for details).
14060 If it cannot find a match, it emits a message.
14062 @item set overload-resolution off
14063 Disable overload resolution for C@t{++} expression evaluation. For
14064 overloaded functions that are not class member functions, @value{GDBN}
14065 chooses the first function of the specified name that it finds in the
14066 symbol table, whether or not its arguments are of the correct type. For
14067 overloaded functions that are class member functions, @value{GDBN}
14068 searches for a function whose signature @emph{exactly} matches the
14071 @kindex show overload-resolution
14072 @item show overload-resolution
14073 Show the current setting of overload resolution.
14075 @item @r{Overloaded symbol names}
14076 You can specify a particular definition of an overloaded symbol, using
14077 the same notation that is used to declare such symbols in C@t{++}: type
14078 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14079 also use the @value{GDBN} command-line word completion facilities to list the
14080 available choices, or to finish the type list for you.
14081 @xref{Completion,, Command Completion}, for details on how to do this.
14084 @node Decimal Floating Point
14085 @subsubsection Decimal Floating Point format
14086 @cindex decimal floating point format
14088 @value{GDBN} can examine, set and perform computations with numbers in
14089 decimal floating point format, which in the C language correspond to the
14090 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14091 specified by the extension to support decimal floating-point arithmetic.
14093 There are two encodings in use, depending on the architecture: BID (Binary
14094 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14095 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14098 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14099 to manipulate decimal floating point numbers, it is not possible to convert
14100 (using a cast, for example) integers wider than 32-bit to decimal float.
14102 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14103 point computations, error checking in decimal float operations ignores
14104 underflow, overflow and divide by zero exceptions.
14106 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14107 to inspect @code{_Decimal128} values stored in floating point registers.
14108 See @ref{PowerPC,,PowerPC} for more details.
14114 @value{GDBN} can be used to debug programs written in D and compiled with
14115 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14116 specific feature --- dynamic arrays.
14121 @cindex Go (programming language)
14122 @value{GDBN} can be used to debug programs written in Go and compiled with
14123 @file{gccgo} or @file{6g} compilers.
14125 Here is a summary of the Go-specific features and restrictions:
14128 @cindex current Go package
14129 @item The current Go package
14130 The name of the current package does not need to be specified when
14131 specifying global variables and functions.
14133 For example, given the program:
14137 var myglob = "Shall we?"
14143 When stopped inside @code{main} either of these work:
14147 (gdb) p main.myglob
14150 @cindex builtin Go types
14151 @item Builtin Go types
14152 The @code{string} type is recognized by @value{GDBN} and is printed
14155 @cindex builtin Go functions
14156 @item Builtin Go functions
14157 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14158 function and handles it internally.
14160 @cindex restrictions on Go expressions
14161 @item Restrictions on Go expressions
14162 All Go operators are supported except @code{&^}.
14163 The Go @code{_} ``blank identifier'' is not supported.
14164 Automatic dereferencing of pointers is not supported.
14168 @subsection Objective-C
14170 @cindex Objective-C
14171 This section provides information about some commands and command
14172 options that are useful for debugging Objective-C code. See also
14173 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14174 few more commands specific to Objective-C support.
14177 * Method Names in Commands::
14178 * The Print Command with Objective-C::
14181 @node Method Names in Commands
14182 @subsubsection Method Names in Commands
14184 The following commands have been extended to accept Objective-C method
14185 names as line specifications:
14187 @kindex clear@r{, and Objective-C}
14188 @kindex break@r{, and Objective-C}
14189 @kindex info line@r{, and Objective-C}
14190 @kindex jump@r{, and Objective-C}
14191 @kindex list@r{, and Objective-C}
14195 @item @code{info line}
14200 A fully qualified Objective-C method name is specified as
14203 -[@var{Class} @var{methodName}]
14206 where the minus sign is used to indicate an instance method and a
14207 plus sign (not shown) is used to indicate a class method. The class
14208 name @var{Class} and method name @var{methodName} are enclosed in
14209 brackets, similar to the way messages are specified in Objective-C
14210 source code. For example, to set a breakpoint at the @code{create}
14211 instance method of class @code{Fruit} in the program currently being
14215 break -[Fruit create]
14218 To list ten program lines around the @code{initialize} class method,
14222 list +[NSText initialize]
14225 In the current version of @value{GDBN}, the plus or minus sign is
14226 required. In future versions of @value{GDBN}, the plus or minus
14227 sign will be optional, but you can use it to narrow the search. It
14228 is also possible to specify just a method name:
14234 You must specify the complete method name, including any colons. If
14235 your program's source files contain more than one @code{create} method,
14236 you'll be presented with a numbered list of classes that implement that
14237 method. Indicate your choice by number, or type @samp{0} to exit if
14240 As another example, to clear a breakpoint established at the
14241 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14244 clear -[NSWindow makeKeyAndOrderFront:]
14247 @node The Print Command with Objective-C
14248 @subsubsection The Print Command With Objective-C
14249 @cindex Objective-C, print objects
14250 @kindex print-object
14251 @kindex po @r{(@code{print-object})}
14253 The print command has also been extended to accept methods. For example:
14256 print -[@var{object} hash]
14259 @cindex print an Objective-C object description
14260 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14262 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14263 and print the result. Also, an additional command has been added,
14264 @code{print-object} or @code{po} for short, which is meant to print
14265 the description of an object. However, this command may only work
14266 with certain Objective-C libraries that have a particular hook
14267 function, @code{_NSPrintForDebugger}, defined.
14270 @subsection OpenCL C
14273 This section provides information about @value{GDBN}s OpenCL C support.
14276 * OpenCL C Datatypes::
14277 * OpenCL C Expressions::
14278 * OpenCL C Operators::
14281 @node OpenCL C Datatypes
14282 @subsubsection OpenCL C Datatypes
14284 @cindex OpenCL C Datatypes
14285 @value{GDBN} supports the builtin scalar and vector datatypes specified
14286 by OpenCL 1.1. In addition the half- and double-precision floating point
14287 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14288 extensions are also known to @value{GDBN}.
14290 @node OpenCL C Expressions
14291 @subsubsection OpenCL C Expressions
14293 @cindex OpenCL C Expressions
14294 @value{GDBN} supports accesses to vector components including the access as
14295 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14296 supported by @value{GDBN} can be used as well.
14298 @node OpenCL C Operators
14299 @subsubsection OpenCL C Operators
14301 @cindex OpenCL C Operators
14302 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14306 @subsection Fortran
14307 @cindex Fortran-specific support in @value{GDBN}
14309 @value{GDBN} can be used to debug programs written in Fortran, but it
14310 currently supports only the features of Fortran 77 language.
14312 @cindex trailing underscore, in Fortran symbols
14313 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14314 among them) append an underscore to the names of variables and
14315 functions. When you debug programs compiled by those compilers, you
14316 will need to refer to variables and functions with a trailing
14320 * Fortran Operators:: Fortran operators and expressions
14321 * Fortran Defaults:: Default settings for Fortran
14322 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14325 @node Fortran Operators
14326 @subsubsection Fortran Operators and Expressions
14328 @cindex Fortran operators and expressions
14330 Operators must be defined on values of specific types. For instance,
14331 @code{+} is defined on numbers, but not on characters or other non-
14332 arithmetic types. Operators are often defined on groups of types.
14336 The exponentiation operator. It raises the first operand to the power
14340 The range operator. Normally used in the form of array(low:high) to
14341 represent a section of array.
14344 The access component operator. Normally used to access elements in derived
14345 types. Also suitable for unions. As unions aren't part of regular Fortran,
14346 this can only happen when accessing a register that uses a gdbarch-defined
14350 @node Fortran Defaults
14351 @subsubsection Fortran Defaults
14353 @cindex Fortran Defaults
14355 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14356 default uses case-insensitive matches for Fortran symbols. You can
14357 change that with the @samp{set case-insensitive} command, see
14358 @ref{Symbols}, for the details.
14360 @node Special Fortran Commands
14361 @subsubsection Special Fortran Commands
14363 @cindex Special Fortran commands
14365 @value{GDBN} has some commands to support Fortran-specific features,
14366 such as displaying common blocks.
14369 @cindex @code{COMMON} blocks, Fortran
14370 @kindex info common
14371 @item info common @r{[}@var{common-name}@r{]}
14372 This command prints the values contained in the Fortran @code{COMMON}
14373 block whose name is @var{common-name}. With no argument, the names of
14374 all @code{COMMON} blocks visible at the current program location are
14381 @cindex Pascal support in @value{GDBN}, limitations
14382 Debugging Pascal programs which use sets, subranges, file variables, or
14383 nested functions does not currently work. @value{GDBN} does not support
14384 entering expressions, printing values, or similar features using Pascal
14387 The Pascal-specific command @code{set print pascal_static-members}
14388 controls whether static members of Pascal objects are displayed.
14389 @xref{Print Settings, pascal_static-members}.
14392 @subsection Modula-2
14394 @cindex Modula-2, @value{GDBN} support
14396 The extensions made to @value{GDBN} to support Modula-2 only support
14397 output from the @sc{gnu} Modula-2 compiler (which is currently being
14398 developed). Other Modula-2 compilers are not currently supported, and
14399 attempting to debug executables produced by them is most likely
14400 to give an error as @value{GDBN} reads in the executable's symbol
14403 @cindex expressions in Modula-2
14405 * M2 Operators:: Built-in operators
14406 * Built-In Func/Proc:: Built-in functions and procedures
14407 * M2 Constants:: Modula-2 constants
14408 * M2 Types:: Modula-2 types
14409 * M2 Defaults:: Default settings for Modula-2
14410 * Deviations:: Deviations from standard Modula-2
14411 * M2 Checks:: Modula-2 type and range checks
14412 * M2 Scope:: The scope operators @code{::} and @code{.}
14413 * GDB/M2:: @value{GDBN} and Modula-2
14417 @subsubsection Operators
14418 @cindex Modula-2 operators
14420 Operators must be defined on values of specific types. For instance,
14421 @code{+} is defined on numbers, but not on structures. Operators are
14422 often defined on groups of types. For the purposes of Modula-2, the
14423 following definitions hold:
14428 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14432 @emph{Character types} consist of @code{CHAR} and its subranges.
14435 @emph{Floating-point types} consist of @code{REAL}.
14438 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14442 @emph{Scalar types} consist of all of the above.
14445 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14448 @emph{Boolean types} consist of @code{BOOLEAN}.
14452 The following operators are supported, and appear in order of
14453 increasing precedence:
14457 Function argument or array index separator.
14460 Assignment. The value of @var{var} @code{:=} @var{value} is
14464 Less than, greater than on integral, floating-point, or enumerated
14468 Less than or equal to, greater than or equal to
14469 on integral, floating-point and enumerated types, or set inclusion on
14470 set types. Same precedence as @code{<}.
14472 @item =@r{, }<>@r{, }#
14473 Equality and two ways of expressing inequality, valid on scalar types.
14474 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14475 available for inequality, since @code{#} conflicts with the script
14479 Set membership. Defined on set types and the types of their members.
14480 Same precedence as @code{<}.
14483 Boolean disjunction. Defined on boolean types.
14486 Boolean conjunction. Defined on boolean types.
14489 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14492 Addition and subtraction on integral and floating-point types, or union
14493 and difference on set types.
14496 Multiplication on integral and floating-point types, or set intersection
14500 Division on floating-point types, or symmetric set difference on set
14501 types. Same precedence as @code{*}.
14504 Integer division and remainder. Defined on integral types. Same
14505 precedence as @code{*}.
14508 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14511 Pointer dereferencing. Defined on pointer types.
14514 Boolean negation. Defined on boolean types. Same precedence as
14518 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14519 precedence as @code{^}.
14522 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14525 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14529 @value{GDBN} and Modula-2 scope operators.
14533 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14534 treats the use of the operator @code{IN}, or the use of operators
14535 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14536 @code{<=}, and @code{>=} on sets as an error.
14540 @node Built-In Func/Proc
14541 @subsubsection Built-in Functions and Procedures
14542 @cindex Modula-2 built-ins
14544 Modula-2 also makes available several built-in procedures and functions.
14545 In describing these, the following metavariables are used:
14550 represents an @code{ARRAY} variable.
14553 represents a @code{CHAR} constant or variable.
14556 represents a variable or constant of integral type.
14559 represents an identifier that belongs to a set. Generally used in the
14560 same function with the metavariable @var{s}. The type of @var{s} should
14561 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14564 represents a variable or constant of integral or floating-point type.
14567 represents a variable or constant of floating-point type.
14573 represents a variable.
14576 represents a variable or constant of one of many types. See the
14577 explanation of the function for details.
14580 All Modula-2 built-in procedures also return a result, described below.
14584 Returns the absolute value of @var{n}.
14587 If @var{c} is a lower case letter, it returns its upper case
14588 equivalent, otherwise it returns its argument.
14591 Returns the character whose ordinal value is @var{i}.
14594 Decrements the value in the variable @var{v} by one. Returns the new value.
14596 @item DEC(@var{v},@var{i})
14597 Decrements the value in the variable @var{v} by @var{i}. Returns the
14600 @item EXCL(@var{m},@var{s})
14601 Removes the element @var{m} from the set @var{s}. Returns the new
14604 @item FLOAT(@var{i})
14605 Returns the floating point equivalent of the integer @var{i}.
14607 @item HIGH(@var{a})
14608 Returns the index of the last member of @var{a}.
14611 Increments the value in the variable @var{v} by one. Returns the new value.
14613 @item INC(@var{v},@var{i})
14614 Increments the value in the variable @var{v} by @var{i}. Returns the
14617 @item INCL(@var{m},@var{s})
14618 Adds the element @var{m} to the set @var{s} if it is not already
14619 there. Returns the new set.
14622 Returns the maximum value of the type @var{t}.
14625 Returns the minimum value of the type @var{t}.
14628 Returns boolean TRUE if @var{i} is an odd number.
14631 Returns the ordinal value of its argument. For example, the ordinal
14632 value of a character is its @sc{ascii} value (on machines supporting the
14633 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14634 integral, character and enumerated types.
14636 @item SIZE(@var{x})
14637 Returns the size of its argument. @var{x} can be a variable or a type.
14639 @item TRUNC(@var{r})
14640 Returns the integral part of @var{r}.
14642 @item TSIZE(@var{x})
14643 Returns the size of its argument. @var{x} can be a variable or a type.
14645 @item VAL(@var{t},@var{i})
14646 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14650 @emph{Warning:} Sets and their operations are not yet supported, so
14651 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14655 @cindex Modula-2 constants
14657 @subsubsection Constants
14659 @value{GDBN} allows you to express the constants of Modula-2 in the following
14665 Integer constants are simply a sequence of digits. When used in an
14666 expression, a constant is interpreted to be type-compatible with the
14667 rest of the expression. Hexadecimal integers are specified by a
14668 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14671 Floating point constants appear as a sequence of digits, followed by a
14672 decimal point and another sequence of digits. An optional exponent can
14673 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14674 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14675 digits of the floating point constant must be valid decimal (base 10)
14679 Character constants consist of a single character enclosed by a pair of
14680 like quotes, either single (@code{'}) or double (@code{"}). They may
14681 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14682 followed by a @samp{C}.
14685 String constants consist of a sequence of characters enclosed by a
14686 pair of like quotes, either single (@code{'}) or double (@code{"}).
14687 Escape sequences in the style of C are also allowed. @xref{C
14688 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14692 Enumerated constants consist of an enumerated identifier.
14695 Boolean constants consist of the identifiers @code{TRUE} and
14699 Pointer constants consist of integral values only.
14702 Set constants are not yet supported.
14706 @subsubsection Modula-2 Types
14707 @cindex Modula-2 types
14709 Currently @value{GDBN} can print the following data types in Modula-2
14710 syntax: array types, record types, set types, pointer types, procedure
14711 types, enumerated types, subrange types and base types. You can also
14712 print the contents of variables declared using these type.
14713 This section gives a number of simple source code examples together with
14714 sample @value{GDBN} sessions.
14716 The first example contains the following section of code:
14725 and you can request @value{GDBN} to interrogate the type and value of
14726 @code{r} and @code{s}.
14729 (@value{GDBP}) print s
14731 (@value{GDBP}) ptype s
14733 (@value{GDBP}) print r
14735 (@value{GDBP}) ptype r
14740 Likewise if your source code declares @code{s} as:
14744 s: SET ['A'..'Z'] ;
14748 then you may query the type of @code{s} by:
14751 (@value{GDBP}) ptype s
14752 type = SET ['A'..'Z']
14756 Note that at present you cannot interactively manipulate set
14757 expressions using the debugger.
14759 The following example shows how you might declare an array in Modula-2
14760 and how you can interact with @value{GDBN} to print its type and contents:
14764 s: ARRAY [-10..10] OF CHAR ;
14768 (@value{GDBP}) ptype s
14769 ARRAY [-10..10] OF CHAR
14772 Note that the array handling is not yet complete and although the type
14773 is printed correctly, expression handling still assumes that all
14774 arrays have a lower bound of zero and not @code{-10} as in the example
14777 Here are some more type related Modula-2 examples:
14781 colour = (blue, red, yellow, green) ;
14782 t = [blue..yellow] ;
14790 The @value{GDBN} interaction shows how you can query the data type
14791 and value of a variable.
14794 (@value{GDBP}) print s
14796 (@value{GDBP}) ptype t
14797 type = [blue..yellow]
14801 In this example a Modula-2 array is declared and its contents
14802 displayed. Observe that the contents are written in the same way as
14803 their @code{C} counterparts.
14807 s: ARRAY [1..5] OF CARDINAL ;
14813 (@value{GDBP}) print s
14814 $1 = @{1, 0, 0, 0, 0@}
14815 (@value{GDBP}) ptype s
14816 type = ARRAY [1..5] OF CARDINAL
14819 The Modula-2 language interface to @value{GDBN} also understands
14820 pointer types as shown in this example:
14824 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14831 and you can request that @value{GDBN} describes the type of @code{s}.
14834 (@value{GDBP}) ptype s
14835 type = POINTER TO ARRAY [1..5] OF CARDINAL
14838 @value{GDBN} handles compound types as we can see in this example.
14839 Here we combine array types, record types, pointer types and subrange
14850 myarray = ARRAY myrange OF CARDINAL ;
14851 myrange = [-2..2] ;
14853 s: POINTER TO ARRAY myrange OF foo ;
14857 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14861 (@value{GDBP}) ptype s
14862 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14865 f3 : ARRAY [-2..2] OF CARDINAL;
14870 @subsubsection Modula-2 Defaults
14871 @cindex Modula-2 defaults
14873 If type and range checking are set automatically by @value{GDBN}, they
14874 both default to @code{on} whenever the working language changes to
14875 Modula-2. This happens regardless of whether you or @value{GDBN}
14876 selected the working language.
14878 If you allow @value{GDBN} to set the language automatically, then entering
14879 code compiled from a file whose name ends with @file{.mod} sets the
14880 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14881 Infer the Source Language}, for further details.
14884 @subsubsection Deviations from Standard Modula-2
14885 @cindex Modula-2, deviations from
14887 A few changes have been made to make Modula-2 programs easier to debug.
14888 This is done primarily via loosening its type strictness:
14892 Unlike in standard Modula-2, pointer constants can be formed by
14893 integers. This allows you to modify pointer variables during
14894 debugging. (In standard Modula-2, the actual address contained in a
14895 pointer variable is hidden from you; it can only be modified
14896 through direct assignment to another pointer variable or expression that
14897 returned a pointer.)
14900 C escape sequences can be used in strings and characters to represent
14901 non-printable characters. @value{GDBN} prints out strings with these
14902 escape sequences embedded. Single non-printable characters are
14903 printed using the @samp{CHR(@var{nnn})} format.
14906 The assignment operator (@code{:=}) returns the value of its right-hand
14910 All built-in procedures both modify @emph{and} return their argument.
14914 @subsubsection Modula-2 Type and Range Checks
14915 @cindex Modula-2 checks
14918 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14921 @c FIXME remove warning when type/range checks added
14923 @value{GDBN} considers two Modula-2 variables type equivalent if:
14927 They are of types that have been declared equivalent via a @code{TYPE
14928 @var{t1} = @var{t2}} statement
14931 They have been declared on the same line. (Note: This is true of the
14932 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14935 As long as type checking is enabled, any attempt to combine variables
14936 whose types are not equivalent is an error.
14938 Range checking is done on all mathematical operations, assignment, array
14939 index bounds, and all built-in functions and procedures.
14942 @subsubsection The Scope Operators @code{::} and @code{.}
14944 @cindex @code{.}, Modula-2 scope operator
14945 @cindex colon, doubled as scope operator
14947 @vindex colon-colon@r{, in Modula-2}
14948 @c Info cannot handle :: but TeX can.
14951 @vindex ::@r{, in Modula-2}
14954 There are a few subtle differences between the Modula-2 scope operator
14955 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14960 @var{module} . @var{id}
14961 @var{scope} :: @var{id}
14965 where @var{scope} is the name of a module or a procedure,
14966 @var{module} the name of a module, and @var{id} is any declared
14967 identifier within your program, except another module.
14969 Using the @code{::} operator makes @value{GDBN} search the scope
14970 specified by @var{scope} for the identifier @var{id}. If it is not
14971 found in the specified scope, then @value{GDBN} searches all scopes
14972 enclosing the one specified by @var{scope}.
14974 Using the @code{.} operator makes @value{GDBN} search the current scope for
14975 the identifier specified by @var{id} that was imported from the
14976 definition module specified by @var{module}. With this operator, it is
14977 an error if the identifier @var{id} was not imported from definition
14978 module @var{module}, or if @var{id} is not an identifier in
14982 @subsubsection @value{GDBN} and Modula-2
14984 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14985 Five subcommands of @code{set print} and @code{show print} apply
14986 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14987 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14988 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14989 analogue in Modula-2.
14991 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14992 with any language, is not useful with Modula-2. Its
14993 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14994 created in Modula-2 as they can in C or C@t{++}. However, because an
14995 address can be specified by an integral constant, the construct
14996 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14998 @cindex @code{#} in Modula-2
14999 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15000 interpreted as the beginning of a comment. Use @code{<>} instead.
15006 The extensions made to @value{GDBN} for Ada only support
15007 output from the @sc{gnu} Ada (GNAT) compiler.
15008 Other Ada compilers are not currently supported, and
15009 attempting to debug executables produced by them is most likely
15013 @cindex expressions in Ada
15015 * Ada Mode Intro:: General remarks on the Ada syntax
15016 and semantics supported by Ada mode
15018 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15019 * Additions to Ada:: Extensions of the Ada expression syntax.
15020 * Stopping Before Main Program:: Debugging the program during elaboration.
15021 * Ada Exceptions:: Ada Exceptions
15022 * Ada Tasks:: Listing and setting breakpoints in tasks.
15023 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15024 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15026 * Ada Glitches:: Known peculiarities of Ada mode.
15029 @node Ada Mode Intro
15030 @subsubsection Introduction
15031 @cindex Ada mode, general
15033 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15034 syntax, with some extensions.
15035 The philosophy behind the design of this subset is
15039 That @value{GDBN} should provide basic literals and access to operations for
15040 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15041 leaving more sophisticated computations to subprograms written into the
15042 program (which therefore may be called from @value{GDBN}).
15045 That type safety and strict adherence to Ada language restrictions
15046 are not particularly important to the @value{GDBN} user.
15049 That brevity is important to the @value{GDBN} user.
15052 Thus, for brevity, the debugger acts as if all names declared in
15053 user-written packages are directly visible, even if they are not visible
15054 according to Ada rules, thus making it unnecessary to fully qualify most
15055 names with their packages, regardless of context. Where this causes
15056 ambiguity, @value{GDBN} asks the user's intent.
15058 The debugger will start in Ada mode if it detects an Ada main program.
15059 As for other languages, it will enter Ada mode when stopped in a program that
15060 was translated from an Ada source file.
15062 While in Ada mode, you may use `@t{--}' for comments. This is useful
15063 mostly for documenting command files. The standard @value{GDBN} comment
15064 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15065 middle (to allow based literals).
15067 The debugger supports limited overloading. Given a subprogram call in which
15068 the function symbol has multiple definitions, it will use the number of
15069 actual parameters and some information about their types to attempt to narrow
15070 the set of definitions. It also makes very limited use of context, preferring
15071 procedures to functions in the context of the @code{call} command, and
15072 functions to procedures elsewhere.
15074 @node Omissions from Ada
15075 @subsubsection Omissions from Ada
15076 @cindex Ada, omissions from
15078 Here are the notable omissions from the subset:
15082 Only a subset of the attributes are supported:
15086 @t{'First}, @t{'Last}, and @t{'Length}
15087 on array objects (not on types and subtypes).
15090 @t{'Min} and @t{'Max}.
15093 @t{'Pos} and @t{'Val}.
15099 @t{'Range} on array objects (not subtypes), but only as the right
15100 operand of the membership (@code{in}) operator.
15103 @t{'Access}, @t{'Unchecked_Access}, and
15104 @t{'Unrestricted_Access} (a GNAT extension).
15112 @code{Characters.Latin_1} are not available and
15113 concatenation is not implemented. Thus, escape characters in strings are
15114 not currently available.
15117 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15118 equality of representations. They will generally work correctly
15119 for strings and arrays whose elements have integer or enumeration types.
15120 They may not work correctly for arrays whose element
15121 types have user-defined equality, for arrays of real values
15122 (in particular, IEEE-conformant floating point, because of negative
15123 zeroes and NaNs), and for arrays whose elements contain unused bits with
15124 indeterminate values.
15127 The other component-by-component array operations (@code{and}, @code{or},
15128 @code{xor}, @code{not}, and relational tests other than equality)
15129 are not implemented.
15132 @cindex array aggregates (Ada)
15133 @cindex record aggregates (Ada)
15134 @cindex aggregates (Ada)
15135 There is limited support for array and record aggregates. They are
15136 permitted only on the right sides of assignments, as in these examples:
15139 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15140 (@value{GDBP}) set An_Array := (1, others => 0)
15141 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15142 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15143 (@value{GDBP}) set A_Record := (1, "Peter", True);
15144 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15148 discriminant's value by assigning an aggregate has an
15149 undefined effect if that discriminant is used within the record.
15150 However, you can first modify discriminants by directly assigning to
15151 them (which normally would not be allowed in Ada), and then performing an
15152 aggregate assignment. For example, given a variable @code{A_Rec}
15153 declared to have a type such as:
15156 type Rec (Len : Small_Integer := 0) is record
15158 Vals : IntArray (1 .. Len);
15162 you can assign a value with a different size of @code{Vals} with two
15166 (@value{GDBP}) set A_Rec.Len := 4
15167 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15170 As this example also illustrates, @value{GDBN} is very loose about the usual
15171 rules concerning aggregates. You may leave out some of the
15172 components of an array or record aggregate (such as the @code{Len}
15173 component in the assignment to @code{A_Rec} above); they will retain their
15174 original values upon assignment. You may freely use dynamic values as
15175 indices in component associations. You may even use overlapping or
15176 redundant component associations, although which component values are
15177 assigned in such cases is not defined.
15180 Calls to dispatching subprograms are not implemented.
15183 The overloading algorithm is much more limited (i.e., less selective)
15184 than that of real Ada. It makes only limited use of the context in
15185 which a subexpression appears to resolve its meaning, and it is much
15186 looser in its rules for allowing type matches. As a result, some
15187 function calls will be ambiguous, and the user will be asked to choose
15188 the proper resolution.
15191 The @code{new} operator is not implemented.
15194 Entry calls are not implemented.
15197 Aside from printing, arithmetic operations on the native VAX floating-point
15198 formats are not supported.
15201 It is not possible to slice a packed array.
15204 The names @code{True} and @code{False}, when not part of a qualified name,
15205 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15207 Should your program
15208 redefine these names in a package or procedure (at best a dubious practice),
15209 you will have to use fully qualified names to access their new definitions.
15212 @node Additions to Ada
15213 @subsubsection Additions to Ada
15214 @cindex Ada, deviations from
15216 As it does for other languages, @value{GDBN} makes certain generic
15217 extensions to Ada (@pxref{Expressions}):
15221 If the expression @var{E} is a variable residing in memory (typically
15222 a local variable or array element) and @var{N} is a positive integer,
15223 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15224 @var{N}-1 adjacent variables following it in memory as an array. In
15225 Ada, this operator is generally not necessary, since its prime use is
15226 in displaying parts of an array, and slicing will usually do this in
15227 Ada. However, there are occasional uses when debugging programs in
15228 which certain debugging information has been optimized away.
15231 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15232 appears in function or file @var{B}.'' When @var{B} is a file name,
15233 you must typically surround it in single quotes.
15236 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15237 @var{type} that appears at address @var{addr}.''
15240 A name starting with @samp{$} is a convenience variable
15241 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15244 In addition, @value{GDBN} provides a few other shortcuts and outright
15245 additions specific to Ada:
15249 The assignment statement is allowed as an expression, returning
15250 its right-hand operand as its value. Thus, you may enter
15253 (@value{GDBP}) set x := y + 3
15254 (@value{GDBP}) print A(tmp := y + 1)
15258 The semicolon is allowed as an ``operator,'' returning as its value
15259 the value of its right-hand operand.
15260 This allows, for example,
15261 complex conditional breaks:
15264 (@value{GDBP}) break f
15265 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15269 Rather than use catenation and symbolic character names to introduce special
15270 characters into strings, one may instead use a special bracket notation,
15271 which is also used to print strings. A sequence of characters of the form
15272 @samp{["@var{XX}"]} within a string or character literal denotes the
15273 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15274 sequence of characters @samp{["""]} also denotes a single quotation mark
15275 in strings. For example,
15277 "One line.["0a"]Next line.["0a"]"
15280 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15284 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15285 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15289 (@value{GDBP}) print 'max(x, y)
15293 When printing arrays, @value{GDBN} uses positional notation when the
15294 array has a lower bound of 1, and uses a modified named notation otherwise.
15295 For example, a one-dimensional array of three integers with a lower bound
15296 of 3 might print as
15303 That is, in contrast to valid Ada, only the first component has a @code{=>}
15307 You may abbreviate attributes in expressions with any unique,
15308 multi-character subsequence of
15309 their names (an exact match gets preference).
15310 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15311 in place of @t{a'length}.
15314 @cindex quoting Ada internal identifiers
15315 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15316 to lower case. The GNAT compiler uses upper-case characters for
15317 some of its internal identifiers, which are normally of no interest to users.
15318 For the rare occasions when you actually have to look at them,
15319 enclose them in angle brackets to avoid the lower-case mapping.
15322 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15326 Printing an object of class-wide type or dereferencing an
15327 access-to-class-wide value will display all the components of the object's
15328 specific type (as indicated by its run-time tag). Likewise, component
15329 selection on such a value will operate on the specific type of the
15334 @node Stopping Before Main Program
15335 @subsubsection Stopping at the Very Beginning
15337 @cindex breakpointing Ada elaboration code
15338 It is sometimes necessary to debug the program during elaboration, and
15339 before reaching the main procedure.
15340 As defined in the Ada Reference
15341 Manual, the elaboration code is invoked from a procedure called
15342 @code{adainit}. To run your program up to the beginning of
15343 elaboration, simply use the following two commands:
15344 @code{tbreak adainit} and @code{run}.
15346 @node Ada Exceptions
15347 @subsubsection Ada Exceptions
15349 A command is provided to list all Ada exceptions:
15352 @kindex info exceptions
15353 @item info exceptions
15354 @itemx info exceptions @var{regexp}
15355 The @code{info exceptions} command allows you to list all Ada exceptions
15356 defined within the program being debugged, as well as their addresses.
15357 With a regular expression, @var{regexp}, as argument, only those exceptions
15358 whose names match @var{regexp} are listed.
15361 Below is a small example, showing how the command can be used, first
15362 without argument, and next with a regular expression passed as an
15366 (@value{GDBP}) info exceptions
15367 All defined Ada exceptions:
15368 constraint_error: 0x613da0
15369 program_error: 0x613d20
15370 storage_error: 0x613ce0
15371 tasking_error: 0x613ca0
15372 const.aint_global_e: 0x613b00
15373 (@value{GDBP}) info exceptions const.aint
15374 All Ada exceptions matching regular expression "const.aint":
15375 constraint_error: 0x613da0
15376 const.aint_global_e: 0x613b00
15379 It is also possible to ask @value{GDBN} to stop your program's execution
15380 when an exception is raised. For more details, see @ref{Set Catchpoints}.
15383 @subsubsection Extensions for Ada Tasks
15384 @cindex Ada, tasking
15386 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15387 @value{GDBN} provides the following task-related commands:
15392 This command shows a list of current Ada tasks, as in the following example:
15399 (@value{GDBP}) info tasks
15400 ID TID P-ID Pri State Name
15401 1 8088000 0 15 Child Activation Wait main_task
15402 2 80a4000 1 15 Accept Statement b
15403 3 809a800 1 15 Child Activation Wait a
15404 * 4 80ae800 3 15 Runnable c
15409 In this listing, the asterisk before the last task indicates it to be the
15410 task currently being inspected.
15414 Represents @value{GDBN}'s internal task number.
15420 The parent's task ID (@value{GDBN}'s internal task number).
15423 The base priority of the task.
15426 Current state of the task.
15430 The task has been created but has not been activated. It cannot be
15434 The task is not blocked for any reason known to Ada. (It may be waiting
15435 for a mutex, though.) It is conceptually "executing" in normal mode.
15438 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15439 that were waiting on terminate alternatives have been awakened and have
15440 terminated themselves.
15442 @item Child Activation Wait
15443 The task is waiting for created tasks to complete activation.
15445 @item Accept Statement
15446 The task is waiting on an accept or selective wait statement.
15448 @item Waiting on entry call
15449 The task is waiting on an entry call.
15451 @item Async Select Wait
15452 The task is waiting to start the abortable part of an asynchronous
15456 The task is waiting on a select statement with only a delay
15459 @item Child Termination Wait
15460 The task is sleeping having completed a master within itself, and is
15461 waiting for the tasks dependent on that master to become terminated or
15462 waiting on a terminate Phase.
15464 @item Wait Child in Term Alt
15465 The task is sleeping waiting for tasks on terminate alternatives to
15466 finish terminating.
15468 @item Accepting RV with @var{taskno}
15469 The task is accepting a rendez-vous with the task @var{taskno}.
15473 Name of the task in the program.
15477 @kindex info task @var{taskno}
15478 @item info task @var{taskno}
15479 This command shows detailled informations on the specified task, as in
15480 the following example:
15485 (@value{GDBP}) info tasks
15486 ID TID P-ID Pri State Name
15487 1 8077880 0 15 Child Activation Wait main_task
15488 * 2 807c468 1 15 Runnable task_1
15489 (@value{GDBP}) info task 2
15490 Ada Task: 0x807c468
15493 Parent: 1 (main_task)
15499 @kindex task@r{ (Ada)}
15500 @cindex current Ada task ID
15501 This command prints the ID of the current task.
15507 (@value{GDBP}) info tasks
15508 ID TID P-ID Pri State Name
15509 1 8077870 0 15 Child Activation Wait main_task
15510 * 2 807c458 1 15 Runnable t
15511 (@value{GDBP}) task
15512 [Current task is 2]
15515 @item task @var{taskno}
15516 @cindex Ada task switching
15517 This command is like the @code{thread @var{threadno}}
15518 command (@pxref{Threads}). It switches the context of debugging
15519 from the current task to the given task.
15525 (@value{GDBP}) info tasks
15526 ID TID P-ID Pri State Name
15527 1 8077870 0 15 Child Activation Wait main_task
15528 * 2 807c458 1 15 Runnable t
15529 (@value{GDBP}) task 1
15530 [Switching to task 1]
15531 #0 0x8067726 in pthread_cond_wait ()
15533 #0 0x8067726 in pthread_cond_wait ()
15534 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15535 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15536 #3 0x806153e in system.tasking.stages.activate_tasks ()
15537 #4 0x804aacc in un () at un.adb:5
15540 @item break @var{linespec} task @var{taskno}
15541 @itemx break @var{linespec} task @var{taskno} if @dots{}
15542 @cindex breakpoints and tasks, in Ada
15543 @cindex task breakpoints, in Ada
15544 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15545 These commands are like the @code{break @dots{} thread @dots{}}
15546 command (@pxref{Thread Stops}).
15547 @var{linespec} specifies source lines, as described
15548 in @ref{Specify Location}.
15550 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15551 to specify that you only want @value{GDBN} to stop the program when a
15552 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15553 numeric task identifiers assigned by @value{GDBN}, shown in the first
15554 column of the @samp{info tasks} display.
15556 If you do not specify @samp{task @var{taskno}} when you set a
15557 breakpoint, the breakpoint applies to @emph{all} tasks of your
15560 You can use the @code{task} qualifier on conditional breakpoints as
15561 well; in this case, place @samp{task @var{taskno}} before the
15562 breakpoint condition (before the @code{if}).
15570 (@value{GDBP}) info tasks
15571 ID TID P-ID Pri State Name
15572 1 140022020 0 15 Child Activation Wait main_task
15573 2 140045060 1 15 Accept/Select Wait t2
15574 3 140044840 1 15 Runnable t1
15575 * 4 140056040 1 15 Runnable t3
15576 (@value{GDBP}) b 15 task 2
15577 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15578 (@value{GDBP}) cont
15583 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15585 (@value{GDBP}) info tasks
15586 ID TID P-ID Pri State Name
15587 1 140022020 0 15 Child Activation Wait main_task
15588 * 2 140045060 1 15 Runnable t2
15589 3 140044840 1 15 Runnable t1
15590 4 140056040 1 15 Delay Sleep t3
15594 @node Ada Tasks and Core Files
15595 @subsubsection Tasking Support when Debugging Core Files
15596 @cindex Ada tasking and core file debugging
15598 When inspecting a core file, as opposed to debugging a live program,
15599 tasking support may be limited or even unavailable, depending on
15600 the platform being used.
15601 For instance, on x86-linux, the list of tasks is available, but task
15602 switching is not supported. On Tru64, however, task switching will work
15605 On certain platforms, including Tru64, the debugger needs to perform some
15606 memory writes in order to provide Ada tasking support. When inspecting
15607 a core file, this means that the core file must be opened with read-write
15608 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15609 Under these circumstances, you should make a backup copy of the core
15610 file before inspecting it with @value{GDBN}.
15612 @node Ravenscar Profile
15613 @subsubsection Tasking Support when using the Ravenscar Profile
15614 @cindex Ravenscar Profile
15616 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15617 specifically designed for systems with safety-critical real-time
15621 @kindex set ravenscar task-switching on
15622 @cindex task switching with program using Ravenscar Profile
15623 @item set ravenscar task-switching on
15624 Allows task switching when debugging a program that uses the Ravenscar
15625 Profile. This is the default.
15627 @kindex set ravenscar task-switching off
15628 @item set ravenscar task-switching off
15629 Turn off task switching when debugging a program that uses the Ravenscar
15630 Profile. This is mostly intended to disable the code that adds support
15631 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15632 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15633 To be effective, this command should be run before the program is started.
15635 @kindex show ravenscar task-switching
15636 @item show ravenscar task-switching
15637 Show whether it is possible to switch from task to task in a program
15638 using the Ravenscar Profile.
15643 @subsubsection Known Peculiarities of Ada Mode
15644 @cindex Ada, problems
15646 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15647 we know of several problems with and limitations of Ada mode in
15649 some of which will be fixed with planned future releases of the debugger
15650 and the GNU Ada compiler.
15654 Static constants that the compiler chooses not to materialize as objects in
15655 storage are invisible to the debugger.
15658 Named parameter associations in function argument lists are ignored (the
15659 argument lists are treated as positional).
15662 Many useful library packages are currently invisible to the debugger.
15665 Fixed-point arithmetic, conversions, input, and output is carried out using
15666 floating-point arithmetic, and may give results that only approximate those on
15670 The GNAT compiler never generates the prefix @code{Standard} for any of
15671 the standard symbols defined by the Ada language. @value{GDBN} knows about
15672 this: it will strip the prefix from names when you use it, and will never
15673 look for a name you have so qualified among local symbols, nor match against
15674 symbols in other packages or subprograms. If you have
15675 defined entities anywhere in your program other than parameters and
15676 local variables whose simple names match names in @code{Standard},
15677 GNAT's lack of qualification here can cause confusion. When this happens,
15678 you can usually resolve the confusion
15679 by qualifying the problematic names with package
15680 @code{Standard} explicitly.
15683 Older versions of the compiler sometimes generate erroneous debugging
15684 information, resulting in the debugger incorrectly printing the value
15685 of affected entities. In some cases, the debugger is able to work
15686 around an issue automatically. In other cases, the debugger is able
15687 to work around the issue, but the work-around has to be specifically
15690 @kindex set ada trust-PAD-over-XVS
15691 @kindex show ada trust-PAD-over-XVS
15694 @item set ada trust-PAD-over-XVS on
15695 Configure GDB to strictly follow the GNAT encoding when computing the
15696 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15697 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15698 a complete description of the encoding used by the GNAT compiler).
15699 This is the default.
15701 @item set ada trust-PAD-over-XVS off
15702 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15703 sometimes prints the wrong value for certain entities, changing @code{ada
15704 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15705 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15706 @code{off}, but this incurs a slight performance penalty, so it is
15707 recommended to leave this setting to @code{on} unless necessary.
15711 @node Unsupported Languages
15712 @section Unsupported Languages
15714 @cindex unsupported languages
15715 @cindex minimal language
15716 In addition to the other fully-supported programming languages,
15717 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15718 It does not represent a real programming language, but provides a set
15719 of capabilities close to what the C or assembly languages provide.
15720 This should allow most simple operations to be performed while debugging
15721 an application that uses a language currently not supported by @value{GDBN}.
15723 If the language is set to @code{auto}, @value{GDBN} will automatically
15724 select this language if the current frame corresponds to an unsupported
15728 @chapter Examining the Symbol Table
15730 The commands described in this chapter allow you to inquire about the
15731 symbols (names of variables, functions and types) defined in your
15732 program. This information is inherent in the text of your program and
15733 does not change as your program executes. @value{GDBN} finds it in your
15734 program's symbol table, in the file indicated when you started @value{GDBN}
15735 (@pxref{File Options, ,Choosing Files}), or by one of the
15736 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15738 @cindex symbol names
15739 @cindex names of symbols
15740 @cindex quoting names
15741 Occasionally, you may need to refer to symbols that contain unusual
15742 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15743 most frequent case is in referring to static variables in other
15744 source files (@pxref{Variables,,Program Variables}). File names
15745 are recorded in object files as debugging symbols, but @value{GDBN} would
15746 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15747 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15748 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15755 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15758 @cindex case-insensitive symbol names
15759 @cindex case sensitivity in symbol names
15760 @kindex set case-sensitive
15761 @item set case-sensitive on
15762 @itemx set case-sensitive off
15763 @itemx set case-sensitive auto
15764 Normally, when @value{GDBN} looks up symbols, it matches their names
15765 with case sensitivity determined by the current source language.
15766 Occasionally, you may wish to control that. The command @code{set
15767 case-sensitive} lets you do that by specifying @code{on} for
15768 case-sensitive matches or @code{off} for case-insensitive ones. If
15769 you specify @code{auto}, case sensitivity is reset to the default
15770 suitable for the source language. The default is case-sensitive
15771 matches for all languages except for Fortran, for which the default is
15772 case-insensitive matches.
15774 @kindex show case-sensitive
15775 @item show case-sensitive
15776 This command shows the current setting of case sensitivity for symbols
15779 @kindex set print type methods
15780 @item set print type methods
15781 @itemx set print type methods on
15782 @itemx set print type methods off
15783 Normally, when @value{GDBN} prints a class, it displays any methods
15784 declared in that class. You can control this behavior either by
15785 passing the appropriate flag to @code{ptype}, or using @command{set
15786 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15787 display the methods; this is the default. Specifying @code{off} will
15788 cause @value{GDBN} to omit the methods.
15790 @kindex show print type methods
15791 @item show print type methods
15792 This command shows the current setting of method display when printing
15795 @kindex set print type typedefs
15796 @item set print type typedefs
15797 @itemx set print type typedefs on
15798 @itemx set print type typedefs off
15800 Normally, when @value{GDBN} prints a class, it displays any typedefs
15801 defined in that class. You can control this behavior either by
15802 passing the appropriate flag to @code{ptype}, or using @command{set
15803 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15804 display the typedef definitions; this is the default. Specifying
15805 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15806 Note that this controls whether the typedef definition itself is
15807 printed, not whether typedef names are substituted when printing other
15810 @kindex show print type typedefs
15811 @item show print type typedefs
15812 This command shows the current setting of typedef display when
15815 @kindex info address
15816 @cindex address of a symbol
15817 @item info address @var{symbol}
15818 Describe where the data for @var{symbol} is stored. For a register
15819 variable, this says which register it is kept in. For a non-register
15820 local variable, this prints the stack-frame offset at which the variable
15823 Note the contrast with @samp{print &@var{symbol}}, which does not work
15824 at all for a register variable, and for a stack local variable prints
15825 the exact address of the current instantiation of the variable.
15827 @kindex info symbol
15828 @cindex symbol from address
15829 @cindex closest symbol and offset for an address
15830 @item info symbol @var{addr}
15831 Print the name of a symbol which is stored at the address @var{addr}.
15832 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15833 nearest symbol and an offset from it:
15836 (@value{GDBP}) info symbol 0x54320
15837 _initialize_vx + 396 in section .text
15841 This is the opposite of the @code{info address} command. You can use
15842 it to find out the name of a variable or a function given its address.
15844 For dynamically linked executables, the name of executable or shared
15845 library containing the symbol is also printed:
15848 (@value{GDBP}) info symbol 0x400225
15849 _start + 5 in section .text of /tmp/a.out
15850 (@value{GDBP}) info symbol 0x2aaaac2811cf
15851 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15855 @item whatis[/@var{flags}] [@var{arg}]
15856 Print the data type of @var{arg}, which can be either an expression
15857 or a name of a data type. With no argument, print the data type of
15858 @code{$}, the last value in the value history.
15860 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15861 is not actually evaluated, and any side-effecting operations (such as
15862 assignments or function calls) inside it do not take place.
15864 If @var{arg} is a variable or an expression, @code{whatis} prints its
15865 literal type as it is used in the source code. If the type was
15866 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15867 the data type underlying the @code{typedef}. If the type of the
15868 variable or the expression is a compound data type, such as
15869 @code{struct} or @code{class}, @code{whatis} never prints their
15870 fields or methods. It just prints the @code{struct}/@code{class}
15871 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15872 such a compound data type, use @code{ptype}.
15874 If @var{arg} is a type name that was defined using @code{typedef},
15875 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15876 Unrolling means that @code{whatis} will show the underlying type used
15877 in the @code{typedef} declaration of @var{arg}. However, if that
15878 underlying type is also a @code{typedef}, @code{whatis} will not
15881 For C code, the type names may also have the form @samp{class
15882 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15883 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15885 @var{flags} can be used to modify how the type is displayed.
15886 Available flags are:
15890 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15891 parameters and typedefs defined in a class when printing the class'
15892 members. The @code{/r} flag disables this.
15895 Do not print methods defined in the class.
15898 Print methods defined in the class. This is the default, but the flag
15899 exists in case you change the default with @command{set print type methods}.
15902 Do not print typedefs defined in the class. Note that this controls
15903 whether the typedef definition itself is printed, not whether typedef
15904 names are substituted when printing other types.
15907 Print typedefs defined in the class. This is the default, but the flag
15908 exists in case you change the default with @command{set print type typedefs}.
15912 @item ptype[/@var{flags}] [@var{arg}]
15913 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15914 detailed description of the type, instead of just the name of the type.
15915 @xref{Expressions, ,Expressions}.
15917 Contrary to @code{whatis}, @code{ptype} always unrolls any
15918 @code{typedef}s in its argument declaration, whether the argument is
15919 a variable, expression, or a data type. This means that @code{ptype}
15920 of a variable or an expression will not print literally its type as
15921 present in the source code---use @code{whatis} for that. @code{typedef}s at
15922 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15923 fields, methods and inner @code{class typedef}s of @code{struct}s,
15924 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15926 For example, for this variable declaration:
15929 typedef double real_t;
15930 struct complex @{ real_t real; double imag; @};
15931 typedef struct complex complex_t;
15933 real_t *real_pointer_var;
15937 the two commands give this output:
15941 (@value{GDBP}) whatis var
15943 (@value{GDBP}) ptype var
15944 type = struct complex @{
15948 (@value{GDBP}) whatis complex_t
15949 type = struct complex
15950 (@value{GDBP}) whatis struct complex
15951 type = struct complex
15952 (@value{GDBP}) ptype struct complex
15953 type = struct complex @{
15957 (@value{GDBP}) whatis real_pointer_var
15959 (@value{GDBP}) ptype real_pointer_var
15965 As with @code{whatis}, using @code{ptype} without an argument refers to
15966 the type of @code{$}, the last value in the value history.
15968 @cindex incomplete type
15969 Sometimes, programs use opaque data types or incomplete specifications
15970 of complex data structure. If the debug information included in the
15971 program does not allow @value{GDBN} to display a full declaration of
15972 the data type, it will say @samp{<incomplete type>}. For example,
15973 given these declarations:
15977 struct foo *fooptr;
15981 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15984 (@value{GDBP}) ptype foo
15985 $1 = <incomplete type>
15989 ``Incomplete type'' is C terminology for data types that are not
15990 completely specified.
15993 @item info types @var{regexp}
15995 Print a brief description of all types whose names match the regular
15996 expression @var{regexp} (or all types in your program, if you supply
15997 no argument). Each complete typename is matched as though it were a
15998 complete line; thus, @samp{i type value} gives information on all
15999 types in your program whose names include the string @code{value}, but
16000 @samp{i type ^value$} gives information only on types whose complete
16001 name is @code{value}.
16003 This command differs from @code{ptype} in two ways: first, like
16004 @code{whatis}, it does not print a detailed description; second, it
16005 lists all source files where a type is defined.
16007 @kindex info type-printers
16008 @item info type-printers
16009 Versions of @value{GDBN} that ship with Python scripting enabled may
16010 have ``type printers'' available. When using @command{ptype} or
16011 @command{whatis}, these printers are consulted when the name of a type
16012 is needed. @xref{Type Printing API}, for more information on writing
16015 @code{info type-printers} displays all the available type printers.
16017 @kindex enable type-printer
16018 @kindex disable type-printer
16019 @item enable type-printer @var{name}@dots{}
16020 @item disable type-printer @var{name}@dots{}
16021 These commands can be used to enable or disable type printers.
16024 @cindex local variables
16025 @item info scope @var{location}
16026 List all the variables local to a particular scope. This command
16027 accepts a @var{location} argument---a function name, a source line, or
16028 an address preceded by a @samp{*}, and prints all the variables local
16029 to the scope defined by that location. (@xref{Specify Location}, for
16030 details about supported forms of @var{location}.) For example:
16033 (@value{GDBP}) @b{info scope command_line_handler}
16034 Scope for command_line_handler:
16035 Symbol rl is an argument at stack/frame offset 8, length 4.
16036 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16037 Symbol linelength is in static storage at address 0x150a1c, length 4.
16038 Symbol p is a local variable in register $esi, length 4.
16039 Symbol p1 is a local variable in register $ebx, length 4.
16040 Symbol nline is a local variable in register $edx, length 4.
16041 Symbol repeat is a local variable at frame offset -8, length 4.
16045 This command is especially useful for determining what data to collect
16046 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16049 @kindex info source
16051 Show information about the current source file---that is, the source file for
16052 the function containing the current point of execution:
16055 the name of the source file, and the directory containing it,
16057 the directory it was compiled in,
16059 its length, in lines,
16061 which programming language it is written in,
16063 whether the executable includes debugging information for that file, and
16064 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16066 whether the debugging information includes information about
16067 preprocessor macros.
16071 @kindex info sources
16073 Print the names of all source files in your program for which there is
16074 debugging information, organized into two lists: files whose symbols
16075 have already been read, and files whose symbols will be read when needed.
16077 @kindex info functions
16078 @item info functions
16079 Print the names and data types of all defined functions.
16081 @item info functions @var{regexp}
16082 Print the names and data types of all defined functions
16083 whose names contain a match for regular expression @var{regexp}.
16084 Thus, @samp{info fun step} finds all functions whose names
16085 include @code{step}; @samp{info fun ^step} finds those whose names
16086 start with @code{step}. If a function name contains characters
16087 that conflict with the regular expression language (e.g.@:
16088 @samp{operator*()}), they may be quoted with a backslash.
16090 @kindex info variables
16091 @item info variables
16092 Print the names and data types of all variables that are defined
16093 outside of functions (i.e.@: excluding local variables).
16095 @item info variables @var{regexp}
16096 Print the names and data types of all variables (except for local
16097 variables) whose names contain a match for regular expression
16100 @kindex info classes
16101 @cindex Objective-C, classes and selectors
16103 @itemx info classes @var{regexp}
16104 Display all Objective-C classes in your program, or
16105 (with the @var{regexp} argument) all those matching a particular regular
16108 @kindex info selectors
16109 @item info selectors
16110 @itemx info selectors @var{regexp}
16111 Display all Objective-C selectors in your program, or
16112 (with the @var{regexp} argument) all those matching a particular regular
16116 This was never implemented.
16117 @kindex info methods
16119 @itemx info methods @var{regexp}
16120 The @code{info methods} command permits the user to examine all defined
16121 methods within C@t{++} program, or (with the @var{regexp} argument) a
16122 specific set of methods found in the various C@t{++} classes. Many
16123 C@t{++} classes provide a large number of methods. Thus, the output
16124 from the @code{ptype} command can be overwhelming and hard to use. The
16125 @code{info-methods} command filters the methods, printing only those
16126 which match the regular-expression @var{regexp}.
16129 @cindex opaque data types
16130 @kindex set opaque-type-resolution
16131 @item set opaque-type-resolution on
16132 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16133 declared as a pointer to a @code{struct}, @code{class}, or
16134 @code{union}---for example, @code{struct MyType *}---that is used in one
16135 source file although the full declaration of @code{struct MyType} is in
16136 another source file. The default is on.
16138 A change in the setting of this subcommand will not take effect until
16139 the next time symbols for a file are loaded.
16141 @item set opaque-type-resolution off
16142 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16143 is printed as follows:
16145 @{<no data fields>@}
16148 @kindex show opaque-type-resolution
16149 @item show opaque-type-resolution
16150 Show whether opaque types are resolved or not.
16152 @kindex maint print symbols
16153 @cindex symbol dump
16154 @kindex maint print psymbols
16155 @cindex partial symbol dump
16156 @kindex maint print msymbols
16157 @cindex minimal symbol dump
16158 @item maint print symbols @var{filename}
16159 @itemx maint print psymbols @var{filename}
16160 @itemx maint print msymbols @var{filename}
16161 Write a dump of debugging symbol data into the file @var{filename}.
16162 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16163 symbols with debugging data are included. If you use @samp{maint print
16164 symbols}, @value{GDBN} includes all the symbols for which it has already
16165 collected full details: that is, @var{filename} reflects symbols for
16166 only those files whose symbols @value{GDBN} has read. You can use the
16167 command @code{info sources} to find out which files these are. If you
16168 use @samp{maint print psymbols} instead, the dump shows information about
16169 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16170 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16171 @samp{maint print msymbols} dumps just the minimal symbol information
16172 required for each object file from which @value{GDBN} has read some symbols.
16173 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16174 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16176 @kindex maint info symtabs
16177 @kindex maint info psymtabs
16178 @cindex listing @value{GDBN}'s internal symbol tables
16179 @cindex symbol tables, listing @value{GDBN}'s internal
16180 @cindex full symbol tables, listing @value{GDBN}'s internal
16181 @cindex partial symbol tables, listing @value{GDBN}'s internal
16182 @item maint info symtabs @r{[} @var{regexp} @r{]}
16183 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16185 List the @code{struct symtab} or @code{struct partial_symtab}
16186 structures whose names match @var{regexp}. If @var{regexp} is not
16187 given, list them all. The output includes expressions which you can
16188 copy into a @value{GDBN} debugging this one to examine a particular
16189 structure in more detail. For example:
16192 (@value{GDBP}) maint info psymtabs dwarf2read
16193 @{ objfile /home/gnu/build/gdb/gdb
16194 ((struct objfile *) 0x82e69d0)
16195 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16196 ((struct partial_symtab *) 0x8474b10)
16199 text addresses 0x814d3c8 -- 0x8158074
16200 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16201 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16202 dependencies (none)
16205 (@value{GDBP}) maint info symtabs
16209 We see that there is one partial symbol table whose filename contains
16210 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16211 and we see that @value{GDBN} has not read in any symtabs yet at all.
16212 If we set a breakpoint on a function, that will cause @value{GDBN} to
16213 read the symtab for the compilation unit containing that function:
16216 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16217 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16219 (@value{GDBP}) maint info symtabs
16220 @{ objfile /home/gnu/build/gdb/gdb
16221 ((struct objfile *) 0x82e69d0)
16222 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16223 ((struct symtab *) 0x86c1f38)
16226 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16227 linetable ((struct linetable *) 0x8370fa0)
16228 debugformat DWARF 2
16237 @chapter Altering Execution
16239 Once you think you have found an error in your program, you might want to
16240 find out for certain whether correcting the apparent error would lead to
16241 correct results in the rest of the run. You can find the answer by
16242 experiment, using the @value{GDBN} features for altering execution of the
16245 For example, you can store new values into variables or memory
16246 locations, give your program a signal, restart it at a different
16247 address, or even return prematurely from a function.
16250 * Assignment:: Assignment to variables
16251 * Jumping:: Continuing at a different address
16252 * Signaling:: Giving your program a signal
16253 * Returning:: Returning from a function
16254 * Calling:: Calling your program's functions
16255 * Patching:: Patching your program
16259 @section Assignment to Variables
16262 @cindex setting variables
16263 To alter the value of a variable, evaluate an assignment expression.
16264 @xref{Expressions, ,Expressions}. For example,
16271 stores the value 4 into the variable @code{x}, and then prints the
16272 value of the assignment expression (which is 4).
16273 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16274 information on operators in supported languages.
16276 @kindex set variable
16277 @cindex variables, setting
16278 If you are not interested in seeing the value of the assignment, use the
16279 @code{set} command instead of the @code{print} command. @code{set} is
16280 really the same as @code{print} except that the expression's value is
16281 not printed and is not put in the value history (@pxref{Value History,
16282 ,Value History}). The expression is evaluated only for its effects.
16284 If the beginning of the argument string of the @code{set} command
16285 appears identical to a @code{set} subcommand, use the @code{set
16286 variable} command instead of just @code{set}. This command is identical
16287 to @code{set} except for its lack of subcommands. For example, if your
16288 program has a variable @code{width}, you get an error if you try to set
16289 a new value with just @samp{set width=13}, because @value{GDBN} has the
16290 command @code{set width}:
16293 (@value{GDBP}) whatis width
16295 (@value{GDBP}) p width
16297 (@value{GDBP}) set width=47
16298 Invalid syntax in expression.
16302 The invalid expression, of course, is @samp{=47}. In
16303 order to actually set the program's variable @code{width}, use
16306 (@value{GDBP}) set var width=47
16309 Because the @code{set} command has many subcommands that can conflict
16310 with the names of program variables, it is a good idea to use the
16311 @code{set variable} command instead of just @code{set}. For example, if
16312 your program has a variable @code{g}, you run into problems if you try
16313 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16314 the command @code{set gnutarget}, abbreviated @code{set g}:
16318 (@value{GDBP}) whatis g
16322 (@value{GDBP}) set g=4
16326 The program being debugged has been started already.
16327 Start it from the beginning? (y or n) y
16328 Starting program: /home/smith/cc_progs/a.out
16329 "/home/smith/cc_progs/a.out": can't open to read symbols:
16330 Invalid bfd target.
16331 (@value{GDBP}) show g
16332 The current BFD target is "=4".
16337 The program variable @code{g} did not change, and you silently set the
16338 @code{gnutarget} to an invalid value. In order to set the variable
16342 (@value{GDBP}) set var g=4
16345 @value{GDBN} allows more implicit conversions in assignments than C; you can
16346 freely store an integer value into a pointer variable or vice versa,
16347 and you can convert any structure to any other structure that is the
16348 same length or shorter.
16349 @comment FIXME: how do structs align/pad in these conversions?
16350 @comment /doc@cygnus.com 18dec1990
16352 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16353 construct to generate a value of specified type at a specified address
16354 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16355 to memory location @code{0x83040} as an integer (which implies a certain size
16356 and representation in memory), and
16359 set @{int@}0x83040 = 4
16363 stores the value 4 into that memory location.
16366 @section Continuing at a Different Address
16368 Ordinarily, when you continue your program, you do so at the place where
16369 it stopped, with the @code{continue} command. You can instead continue at
16370 an address of your own choosing, with the following commands:
16374 @kindex j @r{(@code{jump})}
16375 @item jump @var{linespec}
16376 @itemx j @var{linespec}
16377 @itemx jump @var{location}
16378 @itemx j @var{location}
16379 Resume execution at line @var{linespec} or at address given by
16380 @var{location}. Execution stops again immediately if there is a
16381 breakpoint there. @xref{Specify Location}, for a description of the
16382 different forms of @var{linespec} and @var{location}. It is common
16383 practice to use the @code{tbreak} command in conjunction with
16384 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16386 The @code{jump} command does not change the current stack frame, or
16387 the stack pointer, or the contents of any memory location or any
16388 register other than the program counter. If line @var{linespec} is in
16389 a different function from the one currently executing, the results may
16390 be bizarre if the two functions expect different patterns of arguments or
16391 of local variables. For this reason, the @code{jump} command requests
16392 confirmation if the specified line is not in the function currently
16393 executing. However, even bizarre results are predictable if you are
16394 well acquainted with the machine-language code of your program.
16397 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16398 On many systems, you can get much the same effect as the @code{jump}
16399 command by storing a new value into the register @code{$pc}. The
16400 difference is that this does not start your program running; it only
16401 changes the address of where it @emph{will} run when you continue. For
16409 makes the next @code{continue} command or stepping command execute at
16410 address @code{0x485}, rather than at the address where your program stopped.
16411 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16413 The most common occasion to use the @code{jump} command is to back
16414 up---perhaps with more breakpoints set---over a portion of a program
16415 that has already executed, in order to examine its execution in more
16420 @section Giving your Program a Signal
16421 @cindex deliver a signal to a program
16425 @item signal @var{signal}
16426 Resume execution where your program stopped, but immediately give it the
16427 signal @var{signal}. @var{signal} can be the name or the number of a
16428 signal. For example, on many systems @code{signal 2} and @code{signal
16429 SIGINT} are both ways of sending an interrupt signal.
16431 Alternatively, if @var{signal} is zero, continue execution without
16432 giving a signal. This is useful when your program stopped on account of
16433 a signal and would ordinarily see the signal when resumed with the
16434 @code{continue} command; @samp{signal 0} causes it to resume without a
16437 @code{signal} does not repeat when you press @key{RET} a second time
16438 after executing the command.
16442 Invoking the @code{signal} command is not the same as invoking the
16443 @code{kill} utility from the shell. Sending a signal with @code{kill}
16444 causes @value{GDBN} to decide what to do with the signal depending on
16445 the signal handling tables (@pxref{Signals}). The @code{signal} command
16446 passes the signal directly to your program.
16450 @section Returning from a Function
16453 @cindex returning from a function
16456 @itemx return @var{expression}
16457 You can cancel execution of a function call with the @code{return}
16458 command. If you give an
16459 @var{expression} argument, its value is used as the function's return
16463 When you use @code{return}, @value{GDBN} discards the selected stack frame
16464 (and all frames within it). You can think of this as making the
16465 discarded frame return prematurely. If you wish to specify a value to
16466 be returned, give that value as the argument to @code{return}.
16468 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16469 Frame}), and any other frames inside of it, leaving its caller as the
16470 innermost remaining frame. That frame becomes selected. The
16471 specified value is stored in the registers used for returning values
16474 The @code{return} command does not resume execution; it leaves the
16475 program stopped in the state that would exist if the function had just
16476 returned. In contrast, the @code{finish} command (@pxref{Continuing
16477 and Stepping, ,Continuing and Stepping}) resumes execution until the
16478 selected stack frame returns naturally.
16480 @value{GDBN} needs to know how the @var{expression} argument should be set for
16481 the inferior. The concrete registers assignment depends on the OS ABI and the
16482 type being returned by the selected stack frame. For example it is common for
16483 OS ABI to return floating point values in FPU registers while integer values in
16484 CPU registers. Still some ABIs return even floating point values in CPU
16485 registers. Larger integer widths (such as @code{long long int}) also have
16486 specific placement rules. @value{GDBN} already knows the OS ABI from its
16487 current target so it needs to find out also the type being returned to make the
16488 assignment into the right register(s).
16490 Normally, the selected stack frame has debug info. @value{GDBN} will always
16491 use the debug info instead of the implicit type of @var{expression} when the
16492 debug info is available. For example, if you type @kbd{return -1}, and the
16493 function in the current stack frame is declared to return a @code{long long
16494 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16495 into a @code{long long int}:
16498 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16500 (@value{GDBP}) return -1
16501 Make func return now? (y or n) y
16502 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16503 43 printf ("result=%lld\n", func ());
16507 However, if the selected stack frame does not have a debug info, e.g., if the
16508 function was compiled without debug info, @value{GDBN} has to find out the type
16509 to return from user. Specifying a different type by mistake may set the value
16510 in different inferior registers than the caller code expects. For example,
16511 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16512 of a @code{long long int} result for a debug info less function (on 32-bit
16513 architectures). Therefore the user is required to specify the return type by
16514 an appropriate cast explicitly:
16517 Breakpoint 2, 0x0040050b in func ()
16518 (@value{GDBP}) return -1
16519 Return value type not available for selected stack frame.
16520 Please use an explicit cast of the value to return.
16521 (@value{GDBP}) return (long long int) -1
16522 Make selected stack frame return now? (y or n) y
16523 #0 0x00400526 in main ()
16528 @section Calling Program Functions
16531 @cindex calling functions
16532 @cindex inferior functions, calling
16533 @item print @var{expr}
16534 Evaluate the expression @var{expr} and display the resulting value.
16535 @var{expr} may include calls to functions in the program being
16539 @item call @var{expr}
16540 Evaluate the expression @var{expr} without displaying @code{void}
16543 You can use this variant of the @code{print} command if you want to
16544 execute a function from your program that does not return anything
16545 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16546 with @code{void} returned values that @value{GDBN} will otherwise
16547 print. If the result is not void, it is printed and saved in the
16551 It is possible for the function you call via the @code{print} or
16552 @code{call} command to generate a signal (e.g., if there's a bug in
16553 the function, or if you passed it incorrect arguments). What happens
16554 in that case is controlled by the @code{set unwindonsignal} command.
16556 Similarly, with a C@t{++} program it is possible for the function you
16557 call via the @code{print} or @code{call} command to generate an
16558 exception that is not handled due to the constraints of the dummy
16559 frame. In this case, any exception that is raised in the frame, but has
16560 an out-of-frame exception handler will not be found. GDB builds a
16561 dummy-frame for the inferior function call, and the unwinder cannot
16562 seek for exception handlers outside of this dummy-frame. What happens
16563 in that case is controlled by the
16564 @code{set unwind-on-terminating-exception} command.
16567 @item set unwindonsignal
16568 @kindex set unwindonsignal
16569 @cindex unwind stack in called functions
16570 @cindex call dummy stack unwinding
16571 Set unwinding of the stack if a signal is received while in a function
16572 that @value{GDBN} called in the program being debugged. If set to on,
16573 @value{GDBN} unwinds the stack it created for the call and restores
16574 the context to what it was before the call. If set to off (the
16575 default), @value{GDBN} stops in the frame where the signal was
16578 @item show unwindonsignal
16579 @kindex show unwindonsignal
16580 Show the current setting of stack unwinding in the functions called by
16583 @item set unwind-on-terminating-exception
16584 @kindex set unwind-on-terminating-exception
16585 @cindex unwind stack in called functions with unhandled exceptions
16586 @cindex call dummy stack unwinding on unhandled exception.
16587 Set unwinding of the stack if a C@t{++} exception is raised, but left
16588 unhandled while in a function that @value{GDBN} called in the program being
16589 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16590 it created for the call and restores the context to what it was before
16591 the call. If set to off, @value{GDBN} the exception is delivered to
16592 the default C@t{++} exception handler and the inferior terminated.
16594 @item show unwind-on-terminating-exception
16595 @kindex show unwind-on-terminating-exception
16596 Show the current setting of stack unwinding in the functions called by
16601 @cindex weak alias functions
16602 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16603 for another function. In such case, @value{GDBN} might not pick up
16604 the type information, including the types of the function arguments,
16605 which causes @value{GDBN} to call the inferior function incorrectly.
16606 As a result, the called function will function erroneously and may
16607 even crash. A solution to that is to use the name of the aliased
16611 @section Patching Programs
16613 @cindex patching binaries
16614 @cindex writing into executables
16615 @cindex writing into corefiles
16617 By default, @value{GDBN} opens the file containing your program's
16618 executable code (or the corefile) read-only. This prevents accidental
16619 alterations to machine code; but it also prevents you from intentionally
16620 patching your program's binary.
16622 If you'd like to be able to patch the binary, you can specify that
16623 explicitly with the @code{set write} command. For example, you might
16624 want to turn on internal debugging flags, or even to make emergency
16630 @itemx set write off
16631 If you specify @samp{set write on}, @value{GDBN} opens executable and
16632 core files for both reading and writing; if you specify @kbd{set write
16633 off} (the default), @value{GDBN} opens them read-only.
16635 If you have already loaded a file, you must load it again (using the
16636 @code{exec-file} or @code{core-file} command) after changing @code{set
16637 write}, for your new setting to take effect.
16641 Display whether executable files and core files are opened for writing
16642 as well as reading.
16646 @chapter @value{GDBN} Files
16648 @value{GDBN} needs to know the file name of the program to be debugged,
16649 both in order to read its symbol table and in order to start your
16650 program. To debug a core dump of a previous run, you must also tell
16651 @value{GDBN} the name of the core dump file.
16654 * Files:: Commands to specify files
16655 * Separate Debug Files:: Debugging information in separate files
16656 * MiniDebugInfo:: Debugging information in a special section
16657 * Index Files:: Index files speed up GDB
16658 * Symbol Errors:: Errors reading symbol files
16659 * Data Files:: GDB data files
16663 @section Commands to Specify Files
16665 @cindex symbol table
16666 @cindex core dump file
16668 You may want to specify executable and core dump file names. The usual
16669 way to do this is at start-up time, using the arguments to
16670 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16671 Out of @value{GDBN}}).
16673 Occasionally it is necessary to change to a different file during a
16674 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16675 specify a file you want to use. Or you are debugging a remote target
16676 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16677 Program}). In these situations the @value{GDBN} commands to specify
16678 new files are useful.
16681 @cindex executable file
16683 @item file @var{filename}
16684 Use @var{filename} as the program to be debugged. It is read for its
16685 symbols and for the contents of pure memory. It is also the program
16686 executed when you use the @code{run} command. If you do not specify a
16687 directory and the file is not found in the @value{GDBN} working directory,
16688 @value{GDBN} uses the environment variable @code{PATH} as a list of
16689 directories to search, just as the shell does when looking for a program
16690 to run. You can change the value of this variable, for both @value{GDBN}
16691 and your program, using the @code{path} command.
16693 @cindex unlinked object files
16694 @cindex patching object files
16695 You can load unlinked object @file{.o} files into @value{GDBN} using
16696 the @code{file} command. You will not be able to ``run'' an object
16697 file, but you can disassemble functions and inspect variables. Also,
16698 if the underlying BFD functionality supports it, you could use
16699 @kbd{gdb -write} to patch object files using this technique. Note
16700 that @value{GDBN} can neither interpret nor modify relocations in this
16701 case, so branches and some initialized variables will appear to go to
16702 the wrong place. But this feature is still handy from time to time.
16705 @code{file} with no argument makes @value{GDBN} discard any information it
16706 has on both executable file and the symbol table.
16709 @item exec-file @r{[} @var{filename} @r{]}
16710 Specify that the program to be run (but not the symbol table) is found
16711 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16712 if necessary to locate your program. Omitting @var{filename} means to
16713 discard information on the executable file.
16715 @kindex symbol-file
16716 @item symbol-file @r{[} @var{filename} @r{]}
16717 Read symbol table information from file @var{filename}. @code{PATH} is
16718 searched when necessary. Use the @code{file} command to get both symbol
16719 table and program to run from the same file.
16721 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16722 program's symbol table.
16724 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16725 some breakpoints and auto-display expressions. This is because they may
16726 contain pointers to the internal data recording symbols and data types,
16727 which are part of the old symbol table data being discarded inside
16730 @code{symbol-file} does not repeat if you press @key{RET} again after
16733 When @value{GDBN} is configured for a particular environment, it
16734 understands debugging information in whatever format is the standard
16735 generated for that environment; you may use either a @sc{gnu} compiler, or
16736 other compilers that adhere to the local conventions.
16737 Best results are usually obtained from @sc{gnu} compilers; for example,
16738 using @code{@value{NGCC}} you can generate debugging information for
16741 For most kinds of object files, with the exception of old SVR3 systems
16742 using COFF, the @code{symbol-file} command does not normally read the
16743 symbol table in full right away. Instead, it scans the symbol table
16744 quickly to find which source files and which symbols are present. The
16745 details are read later, one source file at a time, as they are needed.
16747 The purpose of this two-stage reading strategy is to make @value{GDBN}
16748 start up faster. For the most part, it is invisible except for
16749 occasional pauses while the symbol table details for a particular source
16750 file are being read. (The @code{set verbose} command can turn these
16751 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16752 Warnings and Messages}.)
16754 We have not implemented the two-stage strategy for COFF yet. When the
16755 symbol table is stored in COFF format, @code{symbol-file} reads the
16756 symbol table data in full right away. Note that ``stabs-in-COFF''
16757 still does the two-stage strategy, since the debug info is actually
16761 @cindex reading symbols immediately
16762 @cindex symbols, reading immediately
16763 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16764 @itemx file @r{[} -readnow @r{]} @var{filename}
16765 You can override the @value{GDBN} two-stage strategy for reading symbol
16766 tables by using the @samp{-readnow} option with any of the commands that
16767 load symbol table information, if you want to be sure @value{GDBN} has the
16768 entire symbol table available.
16770 @c FIXME: for now no mention of directories, since this seems to be in
16771 @c flux. 13mar1992 status is that in theory GDB would look either in
16772 @c current dir or in same dir as myprog; but issues like competing
16773 @c GDB's, or clutter in system dirs, mean that in practice right now
16774 @c only current dir is used. FFish says maybe a special GDB hierarchy
16775 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16779 @item core-file @r{[}@var{filename}@r{]}
16781 Specify the whereabouts of a core dump file to be used as the ``contents
16782 of memory''. Traditionally, core files contain only some parts of the
16783 address space of the process that generated them; @value{GDBN} can access the
16784 executable file itself for other parts.
16786 @code{core-file} with no argument specifies that no core file is
16789 Note that the core file is ignored when your program is actually running
16790 under @value{GDBN}. So, if you have been running your program and you
16791 wish to debug a core file instead, you must kill the subprocess in which
16792 the program is running. To do this, use the @code{kill} command
16793 (@pxref{Kill Process, ,Killing the Child Process}).
16795 @kindex add-symbol-file
16796 @cindex dynamic linking
16797 @item add-symbol-file @var{filename} @var{address}
16798 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16799 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16800 The @code{add-symbol-file} command reads additional symbol table
16801 information from the file @var{filename}. You would use this command
16802 when @var{filename} has been dynamically loaded (by some other means)
16803 into the program that is running. @var{address} should be the memory
16804 address at which the file has been loaded; @value{GDBN} cannot figure
16805 this out for itself. You can additionally specify an arbitrary number
16806 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16807 section name and base address for that section. You can specify any
16808 @var{address} as an expression.
16810 The symbol table of the file @var{filename} is added to the symbol table
16811 originally read with the @code{symbol-file} command. You can use the
16812 @code{add-symbol-file} command any number of times; the new symbol data
16813 thus read is kept in addition to the old.
16815 Changes can be reverted using the command @code{remove-symbol-file}.
16817 @cindex relocatable object files, reading symbols from
16818 @cindex object files, relocatable, reading symbols from
16819 @cindex reading symbols from relocatable object files
16820 @cindex symbols, reading from relocatable object files
16821 @cindex @file{.o} files, reading symbols from
16822 Although @var{filename} is typically a shared library file, an
16823 executable file, or some other object file which has been fully
16824 relocated for loading into a process, you can also load symbolic
16825 information from relocatable @file{.o} files, as long as:
16829 the file's symbolic information refers only to linker symbols defined in
16830 that file, not to symbols defined by other object files,
16832 every section the file's symbolic information refers to has actually
16833 been loaded into the inferior, as it appears in the file, and
16835 you can determine the address at which every section was loaded, and
16836 provide these to the @code{add-symbol-file} command.
16840 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16841 relocatable files into an already running program; such systems
16842 typically make the requirements above easy to meet. However, it's
16843 important to recognize that many native systems use complex link
16844 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16845 assembly, for example) that make the requirements difficult to meet. In
16846 general, one cannot assume that using @code{add-symbol-file} to read a
16847 relocatable object file's symbolic information will have the same effect
16848 as linking the relocatable object file into the program in the normal
16851 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16853 @kindex remove-symbol-file
16854 @item remove-symbol-file @var{filename}
16855 @item remove-symbol-file -a @var{address}
16856 Remove a symbol file added via the @code{add-symbol-file} command. The
16857 file to remove can be identified by its @var{filename} or by an @var{address}
16858 that lies within the boundaries of this symbol file in memory. Example:
16861 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
16862 add symbol table from file "/home/user/gdb/mylib.so" at
16863 .text_addr = 0x7ffff7ff9480
16865 Reading symbols from /home/user/gdb/mylib.so...done.
16866 (gdb) remove-symbol-file -a 0x7ffff7ff9480
16867 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
16872 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
16874 @kindex add-symbol-file-from-memory
16875 @cindex @code{syscall DSO}
16876 @cindex load symbols from memory
16877 @item add-symbol-file-from-memory @var{address}
16878 Load symbols from the given @var{address} in a dynamically loaded
16879 object file whose image is mapped directly into the inferior's memory.
16880 For example, the Linux kernel maps a @code{syscall DSO} into each
16881 process's address space; this DSO provides kernel-specific code for
16882 some system calls. The argument can be any expression whose
16883 evaluation yields the address of the file's shared object file header.
16884 For this command to work, you must have used @code{symbol-file} or
16885 @code{exec-file} commands in advance.
16887 @kindex add-shared-symbol-files
16889 @item add-shared-symbol-files @var{library-file}
16890 @itemx assf @var{library-file}
16891 The @code{add-shared-symbol-files} command can currently be used only
16892 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16893 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16894 @value{GDBN} automatically looks for shared libraries, however if
16895 @value{GDBN} does not find yours, you can invoke
16896 @code{add-shared-symbol-files}. It takes one argument: the shared
16897 library's file name. @code{assf} is a shorthand alias for
16898 @code{add-shared-symbol-files}.
16901 @item section @var{section} @var{addr}
16902 The @code{section} command changes the base address of the named
16903 @var{section} of the exec file to @var{addr}. This can be used if the
16904 exec file does not contain section addresses, (such as in the
16905 @code{a.out} format), or when the addresses specified in the file
16906 itself are wrong. Each section must be changed separately. The
16907 @code{info files} command, described below, lists all the sections and
16911 @kindex info target
16914 @code{info files} and @code{info target} are synonymous; both print the
16915 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16916 including the names of the executable and core dump files currently in
16917 use by @value{GDBN}, and the files from which symbols were loaded. The
16918 command @code{help target} lists all possible targets rather than
16921 @kindex maint info sections
16922 @item maint info sections
16923 Another command that can give you extra information about program sections
16924 is @code{maint info sections}. In addition to the section information
16925 displayed by @code{info files}, this command displays the flags and file
16926 offset of each section in the executable and core dump files. In addition,
16927 @code{maint info sections} provides the following command options (which
16928 may be arbitrarily combined):
16932 Display sections for all loaded object files, including shared libraries.
16933 @item @var{sections}
16934 Display info only for named @var{sections}.
16935 @item @var{section-flags}
16936 Display info only for sections for which @var{section-flags} are true.
16937 The section flags that @value{GDBN} currently knows about are:
16940 Section will have space allocated in the process when loaded.
16941 Set for all sections except those containing debug information.
16943 Section will be loaded from the file into the child process memory.
16944 Set for pre-initialized code and data, clear for @code{.bss} sections.
16946 Section needs to be relocated before loading.
16948 Section cannot be modified by the child process.
16950 Section contains executable code only.
16952 Section contains data only (no executable code).
16954 Section will reside in ROM.
16956 Section contains data for constructor/destructor lists.
16958 Section is not empty.
16960 An instruction to the linker to not output the section.
16961 @item COFF_SHARED_LIBRARY
16962 A notification to the linker that the section contains
16963 COFF shared library information.
16965 Section contains common symbols.
16968 @kindex set trust-readonly-sections
16969 @cindex read-only sections
16970 @item set trust-readonly-sections on
16971 Tell @value{GDBN} that readonly sections in your object file
16972 really are read-only (i.e.@: that their contents will not change).
16973 In that case, @value{GDBN} can fetch values from these sections
16974 out of the object file, rather than from the target program.
16975 For some targets (notably embedded ones), this can be a significant
16976 enhancement to debugging performance.
16978 The default is off.
16980 @item set trust-readonly-sections off
16981 Tell @value{GDBN} not to trust readonly sections. This means that
16982 the contents of the section might change while the program is running,
16983 and must therefore be fetched from the target when needed.
16985 @item show trust-readonly-sections
16986 Show the current setting of trusting readonly sections.
16989 All file-specifying commands allow both absolute and relative file names
16990 as arguments. @value{GDBN} always converts the file name to an absolute file
16991 name and remembers it that way.
16993 @cindex shared libraries
16994 @anchor{Shared Libraries}
16995 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16996 and IBM RS/6000 AIX shared libraries.
16998 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16999 shared libraries. @xref{Expat}.
17001 @value{GDBN} automatically loads symbol definitions from shared libraries
17002 when you use the @code{run} command, or when you examine a core file.
17003 (Before you issue the @code{run} command, @value{GDBN} does not understand
17004 references to a function in a shared library, however---unless you are
17005 debugging a core file).
17007 On HP-UX, if the program loads a library explicitly, @value{GDBN}
17008 automatically loads the symbols at the time of the @code{shl_load} call.
17010 @c FIXME: some @value{GDBN} release may permit some refs to undef
17011 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
17012 @c FIXME...lib; check this from time to time when updating manual
17014 There are times, however, when you may wish to not automatically load
17015 symbol definitions from shared libraries, such as when they are
17016 particularly large or there are many of them.
17018 To control the automatic loading of shared library symbols, use the
17022 @kindex set auto-solib-add
17023 @item set auto-solib-add @var{mode}
17024 If @var{mode} is @code{on}, symbols from all shared object libraries
17025 will be loaded automatically when the inferior begins execution, you
17026 attach to an independently started inferior, or when the dynamic linker
17027 informs @value{GDBN} that a new library has been loaded. If @var{mode}
17028 is @code{off}, symbols must be loaded manually, using the
17029 @code{sharedlibrary} command. The default value is @code{on}.
17031 @cindex memory used for symbol tables
17032 If your program uses lots of shared libraries with debug info that
17033 takes large amounts of memory, you can decrease the @value{GDBN}
17034 memory footprint by preventing it from automatically loading the
17035 symbols from shared libraries. To that end, type @kbd{set
17036 auto-solib-add off} before running the inferior, then load each
17037 library whose debug symbols you do need with @kbd{sharedlibrary
17038 @var{regexp}}, where @var{regexp} is a regular expression that matches
17039 the libraries whose symbols you want to be loaded.
17041 @kindex show auto-solib-add
17042 @item show auto-solib-add
17043 Display the current autoloading mode.
17046 @cindex load shared library
17047 To explicitly load shared library symbols, use the @code{sharedlibrary}
17051 @kindex info sharedlibrary
17053 @item info share @var{regex}
17054 @itemx info sharedlibrary @var{regex}
17055 Print the names of the shared libraries which are currently loaded
17056 that match @var{regex}. If @var{regex} is omitted then print
17057 all shared libraries that are loaded.
17059 @kindex sharedlibrary
17061 @item sharedlibrary @var{regex}
17062 @itemx share @var{regex}
17063 Load shared object library symbols for files matching a
17064 Unix regular expression.
17065 As with files loaded automatically, it only loads shared libraries
17066 required by your program for a core file or after typing @code{run}. If
17067 @var{regex} is omitted all shared libraries required by your program are
17070 @item nosharedlibrary
17071 @kindex nosharedlibrary
17072 @cindex unload symbols from shared libraries
17073 Unload all shared object library symbols. This discards all symbols
17074 that have been loaded from all shared libraries. Symbols from shared
17075 libraries that were loaded by explicit user requests are not
17079 Sometimes you may wish that @value{GDBN} stops and gives you control
17080 when any of shared library events happen. The best way to do this is
17081 to use @code{catch load} and @code{catch unload} (@pxref{Set
17084 @value{GDBN} also supports the the @code{set stop-on-solib-events}
17085 command for this. This command exists for historical reasons. It is
17086 less useful than setting a catchpoint, because it does not allow for
17087 conditions or commands as a catchpoint does.
17090 @item set stop-on-solib-events
17091 @kindex set stop-on-solib-events
17092 This command controls whether @value{GDBN} should give you control
17093 when the dynamic linker notifies it about some shared library event.
17094 The most common event of interest is loading or unloading of a new
17097 @item show stop-on-solib-events
17098 @kindex show stop-on-solib-events
17099 Show whether @value{GDBN} stops and gives you control when shared
17100 library events happen.
17103 Shared libraries are also supported in many cross or remote debugging
17104 configurations. @value{GDBN} needs to have access to the target's libraries;
17105 this can be accomplished either by providing copies of the libraries
17106 on the host system, or by asking @value{GDBN} to automatically retrieve the
17107 libraries from the target. If copies of the target libraries are
17108 provided, they need to be the same as the target libraries, although the
17109 copies on the target can be stripped as long as the copies on the host are
17112 @cindex where to look for shared libraries
17113 For remote debugging, you need to tell @value{GDBN} where the target
17114 libraries are, so that it can load the correct copies---otherwise, it
17115 may try to load the host's libraries. @value{GDBN} has two variables
17116 to specify the search directories for target libraries.
17119 @cindex prefix for shared library file names
17120 @cindex system root, alternate
17121 @kindex set solib-absolute-prefix
17122 @kindex set sysroot
17123 @item set sysroot @var{path}
17124 Use @var{path} as the system root for the program being debugged. Any
17125 absolute shared library paths will be prefixed with @var{path}; many
17126 runtime loaders store the absolute paths to the shared library in the
17127 target program's memory. If you use @code{set sysroot} to find shared
17128 libraries, they need to be laid out in the same way that they are on
17129 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
17132 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
17133 retrieve the target libraries from the remote system. This is only
17134 supported when using a remote target that supports the @code{remote get}
17135 command (@pxref{File Transfer,,Sending files to a remote system}).
17136 The part of @var{path} following the initial @file{remote:}
17137 (if present) is used as system root prefix on the remote file system.
17138 @footnote{If you want to specify a local system root using a directory
17139 that happens to be named @file{remote:}, you need to use some equivalent
17140 variant of the name like @file{./remote:}.}
17142 For targets with an MS-DOS based filesystem, such as MS-Windows and
17143 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
17144 absolute file name with @var{path}. But first, on Unix hosts,
17145 @value{GDBN} converts all backslash directory separators into forward
17146 slashes, because the backslash is not a directory separator on Unix:
17149 c:\foo\bar.dll @result{} c:/foo/bar.dll
17152 Then, @value{GDBN} attempts prefixing the target file name with
17153 @var{path}, and looks for the resulting file name in the host file
17157 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
17160 If that does not find the shared library, @value{GDBN} tries removing
17161 the @samp{:} character from the drive spec, both for convenience, and,
17162 for the case of the host file system not supporting file names with
17166 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
17169 This makes it possible to have a system root that mirrors a target
17170 with more than one drive. E.g., you may want to setup your local
17171 copies of the target system shared libraries like so (note @samp{c} vs
17175 @file{/path/to/sysroot/c/sys/bin/foo.dll}
17176 @file{/path/to/sysroot/c/sys/bin/bar.dll}
17177 @file{/path/to/sysroot/z/sys/bin/bar.dll}
17181 and point the system root at @file{/path/to/sysroot}, so that
17182 @value{GDBN} can find the correct copies of both
17183 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
17185 If that still does not find the shared library, @value{GDBN} tries
17186 removing the whole drive spec from the target file name:
17189 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
17192 This last lookup makes it possible to not care about the drive name,
17193 if you don't want or need to.
17195 The @code{set solib-absolute-prefix} command is an alias for @code{set
17198 @cindex default system root
17199 @cindex @samp{--with-sysroot}
17200 You can set the default system root by using the configure-time
17201 @samp{--with-sysroot} option. If the system root is inside
17202 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17203 @samp{--exec-prefix}), then the default system root will be updated
17204 automatically if the installed @value{GDBN} is moved to a new
17207 @kindex show sysroot
17209 Display the current shared library prefix.
17211 @kindex set solib-search-path
17212 @item set solib-search-path @var{path}
17213 If this variable is set, @var{path} is a colon-separated list of
17214 directories to search for shared libraries. @samp{solib-search-path}
17215 is used after @samp{sysroot} fails to locate the library, or if the
17216 path to the library is relative instead of absolute. If you want to
17217 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
17218 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
17219 finding your host's libraries. @samp{sysroot} is preferred; setting
17220 it to a nonexistent directory may interfere with automatic loading
17221 of shared library symbols.
17223 @kindex show solib-search-path
17224 @item show solib-search-path
17225 Display the current shared library search path.
17227 @cindex DOS file-name semantics of file names.
17228 @kindex set target-file-system-kind (unix|dos-based|auto)
17229 @kindex show target-file-system-kind
17230 @item set target-file-system-kind @var{kind}
17231 Set assumed file system kind for target reported file names.
17233 Shared library file names as reported by the target system may not
17234 make sense as is on the system @value{GDBN} is running on. For
17235 example, when remote debugging a target that has MS-DOS based file
17236 system semantics, from a Unix host, the target may be reporting to
17237 @value{GDBN} a list of loaded shared libraries with file names such as
17238 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17239 drive letters, so the @samp{c:\} prefix is not normally understood as
17240 indicating an absolute file name, and neither is the backslash
17241 normally considered a directory separator character. In that case,
17242 the native file system would interpret this whole absolute file name
17243 as a relative file name with no directory components. This would make
17244 it impossible to point @value{GDBN} at a copy of the remote target's
17245 shared libraries on the host using @code{set sysroot}, and impractical
17246 with @code{set solib-search-path}. Setting
17247 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17248 to interpret such file names similarly to how the target would, and to
17249 map them to file names valid on @value{GDBN}'s native file system
17250 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17251 to one of the supported file system kinds. In that case, @value{GDBN}
17252 tries to determine the appropriate file system variant based on the
17253 current target's operating system (@pxref{ABI, ,Configuring the
17254 Current ABI}). The supported file system settings are:
17258 Instruct @value{GDBN} to assume the target file system is of Unix
17259 kind. Only file names starting the forward slash (@samp{/}) character
17260 are considered absolute, and the directory separator character is also
17264 Instruct @value{GDBN} to assume the target file system is DOS based.
17265 File names starting with either a forward slash, or a drive letter
17266 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17267 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17268 considered directory separators.
17271 Instruct @value{GDBN} to use the file system kind associated with the
17272 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17273 This is the default.
17277 @cindex file name canonicalization
17278 @cindex base name differences
17279 When processing file names provided by the user, @value{GDBN}
17280 frequently needs to compare them to the file names recorded in the
17281 program's debug info. Normally, @value{GDBN} compares just the
17282 @dfn{base names} of the files as strings, which is reasonably fast
17283 even for very large programs. (The base name of a file is the last
17284 portion of its name, after stripping all the leading directories.)
17285 This shortcut in comparison is based upon the assumption that files
17286 cannot have more than one base name. This is usually true, but
17287 references to files that use symlinks or similar filesystem
17288 facilities violate that assumption. If your program records files
17289 using such facilities, or if you provide file names to @value{GDBN}
17290 using symlinks etc., you can set @code{basenames-may-differ} to
17291 @code{true} to instruct @value{GDBN} to completely canonicalize each
17292 pair of file names it needs to compare. This will make file-name
17293 comparisons accurate, but at a price of a significant slowdown.
17296 @item set basenames-may-differ
17297 @kindex set basenames-may-differ
17298 Set whether a source file may have multiple base names.
17300 @item show basenames-may-differ
17301 @kindex show basenames-may-differ
17302 Show whether a source file may have multiple base names.
17305 @node Separate Debug Files
17306 @section Debugging Information in Separate Files
17307 @cindex separate debugging information files
17308 @cindex debugging information in separate files
17309 @cindex @file{.debug} subdirectories
17310 @cindex debugging information directory, global
17311 @cindex global debugging information directories
17312 @cindex build ID, and separate debugging files
17313 @cindex @file{.build-id} directory
17315 @value{GDBN} allows you to put a program's debugging information in a
17316 file separate from the executable itself, in a way that allows
17317 @value{GDBN} to find and load the debugging information automatically.
17318 Since debugging information can be very large---sometimes larger
17319 than the executable code itself---some systems distribute debugging
17320 information for their executables in separate files, which users can
17321 install only when they need to debug a problem.
17323 @value{GDBN} supports two ways of specifying the separate debug info
17328 The executable contains a @dfn{debug link} that specifies the name of
17329 the separate debug info file. The separate debug file's name is
17330 usually @file{@var{executable}.debug}, where @var{executable} is the
17331 name of the corresponding executable file without leading directories
17332 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17333 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17334 checksum for the debug file, which @value{GDBN} uses to validate that
17335 the executable and the debug file came from the same build.
17338 The executable contains a @dfn{build ID}, a unique bit string that is
17339 also present in the corresponding debug info file. (This is supported
17340 only on some operating systems, notably those which use the ELF format
17341 for binary files and the @sc{gnu} Binutils.) For more details about
17342 this feature, see the description of the @option{--build-id}
17343 command-line option in @ref{Options, , Command Line Options, ld.info,
17344 The GNU Linker}. The debug info file's name is not specified
17345 explicitly by the build ID, but can be computed from the build ID, see
17349 Depending on the way the debug info file is specified, @value{GDBN}
17350 uses two different methods of looking for the debug file:
17354 For the ``debug link'' method, @value{GDBN} looks up the named file in
17355 the directory of the executable file, then in a subdirectory of that
17356 directory named @file{.debug}, and finally under each one of the global debug
17357 directories, in a subdirectory whose name is identical to the leading
17358 directories of the executable's absolute file name.
17361 For the ``build ID'' method, @value{GDBN} looks in the
17362 @file{.build-id} subdirectory of each one of the global debug directories for
17363 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17364 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17365 are the rest of the bit string. (Real build ID strings are 32 or more
17366 hex characters, not 10.)
17369 So, for example, suppose you ask @value{GDBN} to debug
17370 @file{/usr/bin/ls}, which has a debug link that specifies the
17371 file @file{ls.debug}, and a build ID whose value in hex is
17372 @code{abcdef1234}. If the list of the global debug directories includes
17373 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17374 debug information files, in the indicated order:
17378 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17380 @file{/usr/bin/ls.debug}
17382 @file{/usr/bin/.debug/ls.debug}
17384 @file{/usr/lib/debug/usr/bin/ls.debug}.
17387 @anchor{debug-file-directory}
17388 Global debugging info directories default to what is set by @value{GDBN}
17389 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17390 you can also set the global debugging info directories, and view the list
17391 @value{GDBN} is currently using.
17395 @kindex set debug-file-directory
17396 @item set debug-file-directory @var{directories}
17397 Set the directories which @value{GDBN} searches for separate debugging
17398 information files to @var{directory}. Multiple path components can be set
17399 concatenating them by a path separator.
17401 @kindex show debug-file-directory
17402 @item show debug-file-directory
17403 Show the directories @value{GDBN} searches for separate debugging
17408 @cindex @code{.gnu_debuglink} sections
17409 @cindex debug link sections
17410 A debug link is a special section of the executable file named
17411 @code{.gnu_debuglink}. The section must contain:
17415 A filename, with any leading directory components removed, followed by
17418 zero to three bytes of padding, as needed to reach the next four-byte
17419 boundary within the section, and
17421 a four-byte CRC checksum, stored in the same endianness used for the
17422 executable file itself. The checksum is computed on the debugging
17423 information file's full contents by the function given below, passing
17424 zero as the @var{crc} argument.
17427 Any executable file format can carry a debug link, as long as it can
17428 contain a section named @code{.gnu_debuglink} with the contents
17431 @cindex @code{.note.gnu.build-id} sections
17432 @cindex build ID sections
17433 The build ID is a special section in the executable file (and in other
17434 ELF binary files that @value{GDBN} may consider). This section is
17435 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17436 It contains unique identification for the built files---the ID remains
17437 the same across multiple builds of the same build tree. The default
17438 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17439 content for the build ID string. The same section with an identical
17440 value is present in the original built binary with symbols, in its
17441 stripped variant, and in the separate debugging information file.
17443 The debugging information file itself should be an ordinary
17444 executable, containing a full set of linker symbols, sections, and
17445 debugging information. The sections of the debugging information file
17446 should have the same names, addresses, and sizes as the original file,
17447 but they need not contain any data---much like a @code{.bss} section
17448 in an ordinary executable.
17450 The @sc{gnu} binary utilities (Binutils) package includes the
17451 @samp{objcopy} utility that can produce
17452 the separated executable / debugging information file pairs using the
17453 following commands:
17456 @kbd{objcopy --only-keep-debug foo foo.debug}
17461 These commands remove the debugging
17462 information from the executable file @file{foo} and place it in the file
17463 @file{foo.debug}. You can use the first, second or both methods to link the
17468 The debug link method needs the following additional command to also leave
17469 behind a debug link in @file{foo}:
17472 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17475 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17476 a version of the @code{strip} command such that the command @kbd{strip foo -f
17477 foo.debug} has the same functionality as the two @code{objcopy} commands and
17478 the @code{ln -s} command above, together.
17481 Build ID gets embedded into the main executable using @code{ld --build-id} or
17482 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17483 compatibility fixes for debug files separation are present in @sc{gnu} binary
17484 utilities (Binutils) package since version 2.18.
17489 @cindex CRC algorithm definition
17490 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17491 IEEE 802.3 using the polynomial:
17493 @c TexInfo requires naked braces for multi-digit exponents for Tex
17494 @c output, but this causes HTML output to barf. HTML has to be set using
17495 @c raw commands. So we end up having to specify this equation in 2
17500 <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>
17501 + <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
17507 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17508 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17512 The function is computed byte at a time, taking the least
17513 significant bit of each byte first. The initial pattern
17514 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17515 the final result is inverted to ensure trailing zeros also affect the
17518 @emph{Note:} This is the same CRC polynomial as used in handling the
17519 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17520 , @value{GDBN} Remote Serial Protocol}). However in the
17521 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17522 significant bit first, and the result is not inverted, so trailing
17523 zeros have no effect on the CRC value.
17525 To complete the description, we show below the code of the function
17526 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17527 initially supplied @code{crc} argument means that an initial call to
17528 this function passing in zero will start computing the CRC using
17531 @kindex gnu_debuglink_crc32
17534 gnu_debuglink_crc32 (unsigned long crc,
17535 unsigned char *buf, size_t len)
17537 static const unsigned long crc32_table[256] =
17539 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17540 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17541 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17542 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17543 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17544 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17545 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17546 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17547 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17548 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17549 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17550 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17551 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17552 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17553 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17554 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17555 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17556 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17557 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17558 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17559 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17560 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17561 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17562 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17563 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17564 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17565 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17566 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17567 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17568 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17569 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17570 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17571 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17572 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17573 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17574 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17575 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17576 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17577 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17578 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17579 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17580 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17581 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17582 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17583 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17584 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17585 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17586 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17587 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17588 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17589 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17592 unsigned char *end;
17594 crc = ~crc & 0xffffffff;
17595 for (end = buf + len; buf < end; ++buf)
17596 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17597 return ~crc & 0xffffffff;
17602 This computation does not apply to the ``build ID'' method.
17604 @node MiniDebugInfo
17605 @section Debugging information in a special section
17606 @cindex separate debug sections
17607 @cindex @samp{.gnu_debugdata} section
17609 Some systems ship pre-built executables and libraries that have a
17610 special @samp{.gnu_debugdata} section. This feature is called
17611 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17612 is used to supply extra symbols for backtraces.
17614 The intent of this section is to provide extra minimal debugging
17615 information for use in simple backtraces. It is not intended to be a
17616 replacement for full separate debugging information (@pxref{Separate
17617 Debug Files}). The example below shows the intended use; however,
17618 @value{GDBN} does not currently put restrictions on what sort of
17619 debugging information might be included in the section.
17621 @value{GDBN} has support for this extension. If the section exists,
17622 then it is used provided that no other source of debugging information
17623 can be found, and that @value{GDBN} was configured with LZMA support.
17625 This section can be easily created using @command{objcopy} and other
17626 standard utilities:
17629 # Extract the dynamic symbols from the main binary, there is no need
17630 # to also have these in the normal symbol table.
17631 nm -D @var{binary} --format=posix --defined-only \
17632 | awk '@{ print $1 @}' | sort > dynsyms
17634 # Extract all the text (i.e. function) symbols from the debuginfo.
17635 # (Note that we actually also accept "D" symbols, for the benefit
17636 # of platforms like PowerPC64 that use function descriptors.)
17637 nm @var{binary} --format=posix --defined-only \
17638 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17641 # Keep all the function symbols not already in the dynamic symbol
17643 comm -13 dynsyms funcsyms > keep_symbols
17645 # Separate full debug info into debug binary.
17646 objcopy --only-keep-debug @var{binary} debug
17648 # Copy the full debuginfo, keeping only a minimal set of symbols and
17649 # removing some unnecessary sections.
17650 objcopy -S --remove-section .gdb_index --remove-section .comment \
17651 --keep-symbols=keep_symbols debug mini_debuginfo
17653 # Drop the full debug info from the original binary.
17654 strip --strip-all -R .comment @var{binary}
17656 # Inject the compressed data into the .gnu_debugdata section of the
17659 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17663 @section Index Files Speed Up @value{GDBN}
17664 @cindex index files
17665 @cindex @samp{.gdb_index} section
17667 When @value{GDBN} finds a symbol file, it scans the symbols in the
17668 file in order to construct an internal symbol table. This lets most
17669 @value{GDBN} operations work quickly---at the cost of a delay early
17670 on. For large programs, this delay can be quite lengthy, so
17671 @value{GDBN} provides a way to build an index, which speeds up
17674 The index is stored as a section in the symbol file. @value{GDBN} can
17675 write the index to a file, then you can put it into the symbol file
17676 using @command{objcopy}.
17678 To create an index file, use the @code{save gdb-index} command:
17681 @item save gdb-index @var{directory}
17682 @kindex save gdb-index
17683 Create an index file for each symbol file currently known by
17684 @value{GDBN}. Each file is named after its corresponding symbol file,
17685 with @samp{.gdb-index} appended, and is written into the given
17689 Once you have created an index file you can merge it into your symbol
17690 file, here named @file{symfile}, using @command{objcopy}:
17693 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17694 --set-section-flags .gdb_index=readonly symfile symfile
17697 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17698 sections that have been deprecated. Usually they are deprecated because
17699 they are missing a new feature or have performance issues.
17700 To tell @value{GDBN} to use a deprecated index section anyway
17701 specify @code{set use-deprecated-index-sections on}.
17702 The default is @code{off}.
17703 This can speed up startup, but may result in some functionality being lost.
17704 @xref{Index Section Format}.
17706 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17707 must be done before gdb reads the file. The following will not work:
17710 $ gdb -ex "set use-deprecated-index-sections on" <program>
17713 Instead you must do, for example,
17716 $ gdb -iex "set use-deprecated-index-sections on" <program>
17719 There are currently some limitation on indices. They only work when
17720 for DWARF debugging information, not stabs. And, they do not
17721 currently work for programs using Ada.
17723 @node Symbol Errors
17724 @section Errors Reading Symbol Files
17726 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17727 such as symbol types it does not recognize, or known bugs in compiler
17728 output. By default, @value{GDBN} does not notify you of such problems, since
17729 they are relatively common and primarily of interest to people
17730 debugging compilers. If you are interested in seeing information
17731 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17732 only one message about each such type of problem, no matter how many
17733 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17734 to see how many times the problems occur, with the @code{set
17735 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17738 The messages currently printed, and their meanings, include:
17741 @item inner block not inside outer block in @var{symbol}
17743 The symbol information shows where symbol scopes begin and end
17744 (such as at the start of a function or a block of statements). This
17745 error indicates that an inner scope block is not fully contained
17746 in its outer scope blocks.
17748 @value{GDBN} circumvents the problem by treating the inner block as if it had
17749 the same scope as the outer block. In the error message, @var{symbol}
17750 may be shown as ``@code{(don't know)}'' if the outer block is not a
17753 @item block at @var{address} out of order
17755 The symbol information for symbol scope blocks should occur in
17756 order of increasing addresses. This error indicates that it does not
17759 @value{GDBN} does not circumvent this problem, and has trouble
17760 locating symbols in the source file whose symbols it is reading. (You
17761 can often determine what source file is affected by specifying
17762 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17765 @item bad block start address patched
17767 The symbol information for a symbol scope block has a start address
17768 smaller than the address of the preceding source line. This is known
17769 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17771 @value{GDBN} circumvents the problem by treating the symbol scope block as
17772 starting on the previous source line.
17774 @item bad string table offset in symbol @var{n}
17777 Symbol number @var{n} contains a pointer into the string table which is
17778 larger than the size of the string table.
17780 @value{GDBN} circumvents the problem by considering the symbol to have the
17781 name @code{foo}, which may cause other problems if many symbols end up
17784 @item unknown symbol type @code{0x@var{nn}}
17786 The symbol information contains new data types that @value{GDBN} does
17787 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17788 uncomprehended information, in hexadecimal.
17790 @value{GDBN} circumvents the error by ignoring this symbol information.
17791 This usually allows you to debug your program, though certain symbols
17792 are not accessible. If you encounter such a problem and feel like
17793 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17794 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17795 and examine @code{*bufp} to see the symbol.
17797 @item stub type has NULL name
17799 @value{GDBN} could not find the full definition for a struct or class.
17801 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17802 The symbol information for a C@t{++} member function is missing some
17803 information that recent versions of the compiler should have output for
17806 @item info mismatch between compiler and debugger
17808 @value{GDBN} could not parse a type specification output by the compiler.
17813 @section GDB Data Files
17815 @cindex prefix for data files
17816 @value{GDBN} will sometimes read an auxiliary data file. These files
17817 are kept in a directory known as the @dfn{data directory}.
17819 You can set the data directory's name, and view the name @value{GDBN}
17820 is currently using.
17823 @kindex set data-directory
17824 @item set data-directory @var{directory}
17825 Set the directory which @value{GDBN} searches for auxiliary data files
17826 to @var{directory}.
17828 @kindex show data-directory
17829 @item show data-directory
17830 Show the directory @value{GDBN} searches for auxiliary data files.
17833 @cindex default data directory
17834 @cindex @samp{--with-gdb-datadir}
17835 You can set the default data directory by using the configure-time
17836 @samp{--with-gdb-datadir} option. If the data directory is inside
17837 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17838 @samp{--exec-prefix}), then the default data directory will be updated
17839 automatically if the installed @value{GDBN} is moved to a new
17842 The data directory may also be specified with the
17843 @code{--data-directory} command line option.
17844 @xref{Mode Options}.
17847 @chapter Specifying a Debugging Target
17849 @cindex debugging target
17850 A @dfn{target} is the execution environment occupied by your program.
17852 Often, @value{GDBN} runs in the same host environment as your program;
17853 in that case, the debugging target is specified as a side effect when
17854 you use the @code{file} or @code{core} commands. When you need more
17855 flexibility---for example, running @value{GDBN} on a physically separate
17856 host, or controlling a standalone system over a serial port or a
17857 realtime system over a TCP/IP connection---you can use the @code{target}
17858 command to specify one of the target types configured for @value{GDBN}
17859 (@pxref{Target Commands, ,Commands for Managing Targets}).
17861 @cindex target architecture
17862 It is possible to build @value{GDBN} for several different @dfn{target
17863 architectures}. When @value{GDBN} is built like that, you can choose
17864 one of the available architectures with the @kbd{set architecture}
17868 @kindex set architecture
17869 @kindex show architecture
17870 @item set architecture @var{arch}
17871 This command sets the current target architecture to @var{arch}. The
17872 value of @var{arch} can be @code{"auto"}, in addition to one of the
17873 supported architectures.
17875 @item show architecture
17876 Show the current target architecture.
17878 @item set processor
17880 @kindex set processor
17881 @kindex show processor
17882 These are alias commands for, respectively, @code{set architecture}
17883 and @code{show architecture}.
17887 * Active Targets:: Active targets
17888 * Target Commands:: Commands for managing targets
17889 * Byte Order:: Choosing target byte order
17892 @node Active Targets
17893 @section Active Targets
17895 @cindex stacking targets
17896 @cindex active targets
17897 @cindex multiple targets
17899 There are multiple classes of targets such as: processes, executable files or
17900 recording sessions. Core files belong to the process class, making core file
17901 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17902 on multiple active targets, one in each class. This allows you to (for
17903 example) start a process and inspect its activity, while still having access to
17904 the executable file after the process finishes. Or if you start process
17905 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17906 presented a virtual layer of the recording target, while the process target
17907 remains stopped at the chronologically last point of the process execution.
17909 Use the @code{core-file} and @code{exec-file} commands to select a new core
17910 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17911 specify as a target a process that is already running, use the @code{attach}
17912 command (@pxref{Attach, ,Debugging an Already-running Process}).
17914 @node Target Commands
17915 @section Commands for Managing Targets
17918 @item target @var{type} @var{parameters}
17919 Connects the @value{GDBN} host environment to a target machine or
17920 process. A target is typically a protocol for talking to debugging
17921 facilities. You use the argument @var{type} to specify the type or
17922 protocol of the target machine.
17924 Further @var{parameters} are interpreted by the target protocol, but
17925 typically include things like device names or host names to connect
17926 with, process numbers, and baud rates.
17928 The @code{target} command does not repeat if you press @key{RET} again
17929 after executing the command.
17931 @kindex help target
17933 Displays the names of all targets available. To display targets
17934 currently selected, use either @code{info target} or @code{info files}
17935 (@pxref{Files, ,Commands to Specify Files}).
17937 @item help target @var{name}
17938 Describe a particular target, including any parameters necessary to
17941 @kindex set gnutarget
17942 @item set gnutarget @var{args}
17943 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17944 knows whether it is reading an @dfn{executable},
17945 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17946 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17947 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17950 @emph{Warning:} To specify a file format with @code{set gnutarget},
17951 you must know the actual BFD name.
17955 @xref{Files, , Commands to Specify Files}.
17957 @kindex show gnutarget
17958 @item show gnutarget
17959 Use the @code{show gnutarget} command to display what file format
17960 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17961 @value{GDBN} will determine the file format for each file automatically,
17962 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17965 @cindex common targets
17966 Here are some common targets (available, or not, depending on the GDB
17971 @item target exec @var{program}
17972 @cindex executable file target
17973 An executable file. @samp{target exec @var{program}} is the same as
17974 @samp{exec-file @var{program}}.
17976 @item target core @var{filename}
17977 @cindex core dump file target
17978 A core dump file. @samp{target core @var{filename}} is the same as
17979 @samp{core-file @var{filename}}.
17981 @item target remote @var{medium}
17982 @cindex remote target
17983 A remote system connected to @value{GDBN} via a serial line or network
17984 connection. This command tells @value{GDBN} to use its own remote
17985 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17987 For example, if you have a board connected to @file{/dev/ttya} on the
17988 machine running @value{GDBN}, you could say:
17991 target remote /dev/ttya
17994 @code{target remote} supports the @code{load} command. This is only
17995 useful if you have some other way of getting the stub to the target
17996 system, and you can put it somewhere in memory where it won't get
17997 clobbered by the download.
17999 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18000 @cindex built-in simulator target
18001 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
18009 works; however, you cannot assume that a specific memory map, device
18010 drivers, or even basic I/O is available, although some simulators do
18011 provide these. For info about any processor-specific simulator details,
18012 see the appropriate section in @ref{Embedded Processors, ,Embedded
18017 Different targets are available on different configurations of @value{GDBN};
18018 your configuration may have more or fewer targets.
18020 Many remote targets require you to download the executable's code once
18021 you've successfully established a connection. You may wish to control
18022 various aspects of this process.
18027 @kindex set hash@r{, for remote monitors}
18028 @cindex hash mark while downloading
18029 This command controls whether a hash mark @samp{#} is displayed while
18030 downloading a file to the remote monitor. If on, a hash mark is
18031 displayed after each S-record is successfully downloaded to the
18035 @kindex show hash@r{, for remote monitors}
18036 Show the current status of displaying the hash mark.
18038 @item set debug monitor
18039 @kindex set debug monitor
18040 @cindex display remote monitor communications
18041 Enable or disable display of communications messages between
18042 @value{GDBN} and the remote monitor.
18044 @item show debug monitor
18045 @kindex show debug monitor
18046 Show the current status of displaying communications between
18047 @value{GDBN} and the remote monitor.
18052 @kindex load @var{filename}
18053 @item load @var{filename}
18055 Depending on what remote debugging facilities are configured into
18056 @value{GDBN}, the @code{load} command may be available. Where it exists, it
18057 is meant to make @var{filename} (an executable) available for debugging
18058 on the remote system---by downloading, or dynamic linking, for example.
18059 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
18060 the @code{add-symbol-file} command.
18062 If your @value{GDBN} does not have a @code{load} command, attempting to
18063 execute it gets the error message ``@code{You can't do that when your
18064 target is @dots{}}''
18066 The file is loaded at whatever address is specified in the executable.
18067 For some object file formats, you can specify the load address when you
18068 link the program; for other formats, like a.out, the object file format
18069 specifies a fixed address.
18070 @c FIXME! This would be a good place for an xref to the GNU linker doc.
18072 Depending on the remote side capabilities, @value{GDBN} may be able to
18073 load programs into flash memory.
18075 @code{load} does not repeat if you press @key{RET} again after using it.
18079 @section Choosing Target Byte Order
18081 @cindex choosing target byte order
18082 @cindex target byte order
18084 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
18085 offer the ability to run either big-endian or little-endian byte
18086 orders. Usually the executable or symbol will include a bit to
18087 designate the endian-ness, and you will not need to worry about
18088 which to use. However, you may still find it useful to adjust
18089 @value{GDBN}'s idea of processor endian-ness manually.
18093 @item set endian big
18094 Instruct @value{GDBN} to assume the target is big-endian.
18096 @item set endian little
18097 Instruct @value{GDBN} to assume the target is little-endian.
18099 @item set endian auto
18100 Instruct @value{GDBN} to use the byte order associated with the
18104 Display @value{GDBN}'s current idea of the target byte order.
18108 Note that these commands merely adjust interpretation of symbolic
18109 data on the host, and that they have absolutely no effect on the
18113 @node Remote Debugging
18114 @chapter Debugging Remote Programs
18115 @cindex remote debugging
18117 If you are trying to debug a program running on a machine that cannot run
18118 @value{GDBN} in the usual way, it is often useful to use remote debugging.
18119 For example, you might use remote debugging on an operating system kernel,
18120 or on a small system which does not have a general purpose operating system
18121 powerful enough to run a full-featured debugger.
18123 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
18124 to make this work with particular debugging targets. In addition,
18125 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
18126 but not specific to any particular target system) which you can use if you
18127 write the remote stubs---the code that runs on the remote system to
18128 communicate with @value{GDBN}.
18130 Other remote targets may be available in your
18131 configuration of @value{GDBN}; use @code{help target} to list them.
18134 * Connecting:: Connecting to a remote target
18135 * File Transfer:: Sending files to a remote system
18136 * Server:: Using the gdbserver program
18137 * Remote Configuration:: Remote configuration
18138 * Remote Stub:: Implementing a remote stub
18142 @section Connecting to a Remote Target
18144 On the @value{GDBN} host machine, you will need an unstripped copy of
18145 your program, since @value{GDBN} needs symbol and debugging information.
18146 Start up @value{GDBN} as usual, using the name of the local copy of your
18147 program as the first argument.
18149 @cindex @code{target remote}
18150 @value{GDBN} can communicate with the target over a serial line, or
18151 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
18152 each case, @value{GDBN} uses the same protocol for debugging your
18153 program; only the medium carrying the debugging packets varies. The
18154 @code{target remote} command establishes a connection to the target.
18155 Its arguments indicate which medium to use:
18159 @item target remote @var{serial-device}
18160 @cindex serial line, @code{target remote}
18161 Use @var{serial-device} to communicate with the target. For example,
18162 to use a serial line connected to the device named @file{/dev/ttyb}:
18165 target remote /dev/ttyb
18168 If you're using a serial line, you may want to give @value{GDBN} the
18169 @samp{--baud} option, or use the @code{set serial baud} command
18170 (@pxref{Remote Configuration, set serial baud}) before the
18171 @code{target} command.
18173 @item target remote @code{@var{host}:@var{port}}
18174 @itemx target remote @code{tcp:@var{host}:@var{port}}
18175 @cindex @acronym{TCP} port, @code{target remote}
18176 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
18177 The @var{host} may be either a host name or a numeric @acronym{IP}
18178 address; @var{port} must be a decimal number. The @var{host} could be
18179 the target machine itself, if it is directly connected to the net, or
18180 it might be a terminal server which in turn has a serial line to the
18183 For example, to connect to port 2828 on a terminal server named
18187 target remote manyfarms:2828
18190 If your remote target is actually running on the same machine as your
18191 debugger session (e.g.@: a simulator for your target running on the
18192 same host), you can omit the hostname. For example, to connect to
18193 port 1234 on your local machine:
18196 target remote :1234
18200 Note that the colon is still required here.
18202 @item target remote @code{udp:@var{host}:@var{port}}
18203 @cindex @acronym{UDP} port, @code{target remote}
18204 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
18205 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
18208 target remote udp:manyfarms:2828
18211 When using a @acronym{UDP} connection for remote debugging, you should
18212 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
18213 can silently drop packets on busy or unreliable networks, which will
18214 cause havoc with your debugging session.
18216 @item target remote | @var{command}
18217 @cindex pipe, @code{target remote} to
18218 Run @var{command} in the background and communicate with it using a
18219 pipe. The @var{command} is a shell command, to be parsed and expanded
18220 by the system's command shell, @code{/bin/sh}; it should expect remote
18221 protocol packets on its standard input, and send replies on its
18222 standard output. You could use this to run a stand-alone simulator
18223 that speaks the remote debugging protocol, to make net connections
18224 using programs like @code{ssh}, or for other similar tricks.
18226 If @var{command} closes its standard output (perhaps by exiting),
18227 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
18228 program has already exited, this will have no effect.)
18232 Once the connection has been established, you can use all the usual
18233 commands to examine and change data. The remote program is already
18234 running; you can use @kbd{step} and @kbd{continue}, and you do not
18235 need to use @kbd{run}.
18237 @cindex interrupting remote programs
18238 @cindex remote programs, interrupting
18239 Whenever @value{GDBN} is waiting for the remote program, if you type the
18240 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18241 program. This may or may not succeed, depending in part on the hardware
18242 and the serial drivers the remote system uses. If you type the
18243 interrupt character once again, @value{GDBN} displays this prompt:
18246 Interrupted while waiting for the program.
18247 Give up (and stop debugging it)? (y or n)
18250 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18251 (If you decide you want to try again later, you can use @samp{target
18252 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18253 goes back to waiting.
18256 @kindex detach (remote)
18258 When you have finished debugging the remote program, you can use the
18259 @code{detach} command to release it from @value{GDBN} control.
18260 Detaching from the target normally resumes its execution, but the results
18261 will depend on your particular remote stub. After the @code{detach}
18262 command, @value{GDBN} is free to connect to another target.
18266 The @code{disconnect} command behaves like @code{detach}, except that
18267 the target is generally not resumed. It will wait for @value{GDBN}
18268 (this instance or another one) to connect and continue debugging. After
18269 the @code{disconnect} command, @value{GDBN} is again free to connect to
18272 @cindex send command to remote monitor
18273 @cindex extend @value{GDBN} for remote targets
18274 @cindex add new commands for external monitor
18276 @item monitor @var{cmd}
18277 This command allows you to send arbitrary commands directly to the
18278 remote monitor. Since @value{GDBN} doesn't care about the commands it
18279 sends like this, this command is the way to extend @value{GDBN}---you
18280 can add new commands that only the external monitor will understand
18284 @node File Transfer
18285 @section Sending files to a remote system
18286 @cindex remote target, file transfer
18287 @cindex file transfer
18288 @cindex sending files to remote systems
18290 Some remote targets offer the ability to transfer files over the same
18291 connection used to communicate with @value{GDBN}. This is convenient
18292 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18293 running @code{gdbserver} over a network interface. For other targets,
18294 e.g.@: embedded devices with only a single serial port, this may be
18295 the only way to upload or download files.
18297 Not all remote targets support these commands.
18301 @item remote put @var{hostfile} @var{targetfile}
18302 Copy file @var{hostfile} from the host system (the machine running
18303 @value{GDBN}) to @var{targetfile} on the target system.
18306 @item remote get @var{targetfile} @var{hostfile}
18307 Copy file @var{targetfile} from the target system to @var{hostfile}
18308 on the host system.
18310 @kindex remote delete
18311 @item remote delete @var{targetfile}
18312 Delete @var{targetfile} from the target system.
18317 @section Using the @code{gdbserver} Program
18320 @cindex remote connection without stubs
18321 @code{gdbserver} is a control program for Unix-like systems, which
18322 allows you to connect your program with a remote @value{GDBN} via
18323 @code{target remote}---but without linking in the usual debugging stub.
18325 @code{gdbserver} is not a complete replacement for the debugging stubs,
18326 because it requires essentially the same operating-system facilities
18327 that @value{GDBN} itself does. In fact, a system that can run
18328 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18329 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18330 because it is a much smaller program than @value{GDBN} itself. It is
18331 also easier to port than all of @value{GDBN}, so you may be able to get
18332 started more quickly on a new system by using @code{gdbserver}.
18333 Finally, if you develop code for real-time systems, you may find that
18334 the tradeoffs involved in real-time operation make it more convenient to
18335 do as much development work as possible on another system, for example
18336 by cross-compiling. You can use @code{gdbserver} to make a similar
18337 choice for debugging.
18339 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18340 or a TCP connection, using the standard @value{GDBN} remote serial
18344 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18345 Do not run @code{gdbserver} connected to any public network; a
18346 @value{GDBN} connection to @code{gdbserver} provides access to the
18347 target system with the same privileges as the user running
18351 @subsection Running @code{gdbserver}
18352 @cindex arguments, to @code{gdbserver}
18353 @cindex @code{gdbserver}, command-line arguments
18355 Run @code{gdbserver} on the target system. You need a copy of the
18356 program you want to debug, including any libraries it requires.
18357 @code{gdbserver} does not need your program's symbol table, so you can
18358 strip the program if necessary to save space. @value{GDBN} on the host
18359 system does all the symbol handling.
18361 To use the server, you must tell it how to communicate with @value{GDBN};
18362 the name of your program; and the arguments for your program. The usual
18366 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18369 @var{comm} is either a device name (to use a serial line), or a TCP
18370 hostname and portnumber, or @code{-} or @code{stdio} to use
18371 stdin/stdout of @code{gdbserver}.
18372 For example, to debug Emacs with the argument
18373 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18377 target> gdbserver /dev/com1 emacs foo.txt
18380 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18383 To use a TCP connection instead of a serial line:
18386 target> gdbserver host:2345 emacs foo.txt
18389 The only difference from the previous example is the first argument,
18390 specifying that you are communicating with the host @value{GDBN} via
18391 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18392 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18393 (Currently, the @samp{host} part is ignored.) You can choose any number
18394 you want for the port number as long as it does not conflict with any
18395 TCP ports already in use on the target system (for example, @code{23} is
18396 reserved for @code{telnet}).@footnote{If you choose a port number that
18397 conflicts with another service, @code{gdbserver} prints an error message
18398 and exits.} You must use the same port number with the host @value{GDBN}
18399 @code{target remote} command.
18401 The @code{stdio} connection is useful when starting @code{gdbserver}
18405 (gdb) target remote | ssh -T hostname gdbserver - hello
18408 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18409 and we don't want escape-character handling. Ssh does this by default when
18410 a command is provided, the flag is provided to make it explicit.
18411 You could elide it if you want to.
18413 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18414 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18415 display through a pipe connected to gdbserver.
18416 Both @code{stdout} and @code{stderr} use the same pipe.
18418 @subsubsection Attaching to a Running Program
18419 @cindex attach to a program, @code{gdbserver}
18420 @cindex @option{--attach}, @code{gdbserver} option
18422 On some targets, @code{gdbserver} can also attach to running programs.
18423 This is accomplished via the @code{--attach} argument. The syntax is:
18426 target> gdbserver --attach @var{comm} @var{pid}
18429 @var{pid} is the process ID of a currently running process. It isn't necessary
18430 to point @code{gdbserver} at a binary for the running process.
18433 You can debug processes by name instead of process ID if your target has the
18434 @code{pidof} utility:
18437 target> gdbserver --attach @var{comm} `pidof @var{program}`
18440 In case more than one copy of @var{program} is running, or @var{program}
18441 has multiple threads, most versions of @code{pidof} support the
18442 @code{-s} option to only return the first process ID.
18444 @subsubsection Multi-Process Mode for @code{gdbserver}
18445 @cindex @code{gdbserver}, multiple processes
18446 @cindex multiple processes with @code{gdbserver}
18448 When you connect to @code{gdbserver} using @code{target remote},
18449 @code{gdbserver} debugs the specified program only once. When the
18450 program exits, or you detach from it, @value{GDBN} closes the connection
18451 and @code{gdbserver} exits.
18453 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18454 enters multi-process mode. When the debugged program exits, or you
18455 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18456 though no program is running. The @code{run} and @code{attach}
18457 commands instruct @code{gdbserver} to run or attach to a new program.
18458 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18459 remote exec-file}) to select the program to run. Command line
18460 arguments are supported, except for wildcard expansion and I/O
18461 redirection (@pxref{Arguments}).
18463 @cindex @option{--multi}, @code{gdbserver} option
18464 To start @code{gdbserver} without supplying an initial command to run
18465 or process ID to attach, use the @option{--multi} command line option.
18466 Then you can connect using @kbd{target extended-remote} and start
18467 the program you want to debug.
18469 In multi-process mode @code{gdbserver} does not automatically exit unless you
18470 use the option @option{--once}. You can terminate it by using
18471 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18472 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18473 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18474 @option{--multi} option to @code{gdbserver} has no influence on that.
18476 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18478 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18480 @code{gdbserver} normally terminates after all of its debugged processes have
18481 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18482 extended-remote}, @code{gdbserver} stays running even with no processes left.
18483 @value{GDBN} normally terminates the spawned debugged process on its exit,
18484 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18485 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18486 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18487 stays running even in the @kbd{target remote} mode.
18489 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18490 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18491 completeness, at most one @value{GDBN} can be connected at a time.
18493 @cindex @option{--once}, @code{gdbserver} option
18494 By default, @code{gdbserver} keeps the listening TCP port open, so that
18495 subsequent connections are possible. However, if you start @code{gdbserver}
18496 with the @option{--once} option, it will stop listening for any further
18497 connection attempts after connecting to the first @value{GDBN} session. This
18498 means no further connections to @code{gdbserver} will be possible after the
18499 first one. It also means @code{gdbserver} will terminate after the first
18500 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18501 connections and even in the @kbd{target extended-remote} mode. The
18502 @option{--once} option allows reusing the same port number for connecting to
18503 multiple instances of @code{gdbserver} running on the same host, since each
18504 instance closes its port after the first connection.
18506 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18508 @cindex @option{--debug}, @code{gdbserver} option
18509 The @option{--debug} option tells @code{gdbserver} to display extra
18510 status information about the debugging process.
18511 @cindex @option{--remote-debug}, @code{gdbserver} option
18512 The @option{--remote-debug} option tells @code{gdbserver} to display
18513 remote protocol debug output. These options are intended for
18514 @code{gdbserver} development and for bug reports to the developers.
18516 @cindex @option{--wrapper}, @code{gdbserver} option
18517 The @option{--wrapper} option specifies a wrapper to launch programs
18518 for debugging. The option should be followed by the name of the
18519 wrapper, then any command-line arguments to pass to the wrapper, then
18520 @kbd{--} indicating the end of the wrapper arguments.
18522 @code{gdbserver} runs the specified wrapper program with a combined
18523 command line including the wrapper arguments, then the name of the
18524 program to debug, then any arguments to the program. The wrapper
18525 runs until it executes your program, and then @value{GDBN} gains control.
18527 You can use any program that eventually calls @code{execve} with
18528 its arguments as a wrapper. Several standard Unix utilities do
18529 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18530 with @code{exec "$@@"} will also work.
18532 For example, you can use @code{env} to pass an environment variable to
18533 the debugged program, without setting the variable in @code{gdbserver}'s
18537 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18540 @subsection Connecting to @code{gdbserver}
18542 Run @value{GDBN} on the host system.
18544 First make sure you have the necessary symbol files. Load symbols for
18545 your application using the @code{file} command before you connect. Use
18546 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18547 was compiled with the correct sysroot using @code{--with-sysroot}).
18549 The symbol file and target libraries must exactly match the executable
18550 and libraries on the target, with one exception: the files on the host
18551 system should not be stripped, even if the files on the target system
18552 are. Mismatched or missing files will lead to confusing results
18553 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18554 files may also prevent @code{gdbserver} from debugging multi-threaded
18557 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18558 For TCP connections, you must start up @code{gdbserver} prior to using
18559 the @code{target remote} command. Otherwise you may get an error whose
18560 text depends on the host system, but which usually looks something like
18561 @samp{Connection refused}. Don't use the @code{load}
18562 command in @value{GDBN} when using @code{gdbserver}, since the program is
18563 already on the target.
18565 @subsection Monitor Commands for @code{gdbserver}
18566 @cindex monitor commands, for @code{gdbserver}
18567 @anchor{Monitor Commands for gdbserver}
18569 During a @value{GDBN} session using @code{gdbserver}, you can use the
18570 @code{monitor} command to send special requests to @code{gdbserver}.
18571 Here are the available commands.
18575 List the available monitor commands.
18577 @item monitor set debug 0
18578 @itemx monitor set debug 1
18579 Disable or enable general debugging messages.
18581 @item monitor set remote-debug 0
18582 @itemx monitor set remote-debug 1
18583 Disable or enable specific debugging messages associated with the remote
18584 protocol (@pxref{Remote Protocol}).
18586 @item monitor set libthread-db-search-path [PATH]
18587 @cindex gdbserver, search path for @code{libthread_db}
18588 When this command is issued, @var{path} is a colon-separated list of
18589 directories to search for @code{libthread_db} (@pxref{Threads,,set
18590 libthread-db-search-path}). If you omit @var{path},
18591 @samp{libthread-db-search-path} will be reset to its default value.
18593 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18594 not supported in @code{gdbserver}.
18597 Tell gdbserver to exit immediately. This command should be followed by
18598 @code{disconnect} to close the debugging session. @code{gdbserver} will
18599 detach from any attached processes and kill any processes it created.
18600 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18601 of a multi-process mode debug session.
18605 @subsection Tracepoints support in @code{gdbserver}
18606 @cindex tracepoints support in @code{gdbserver}
18608 On some targets, @code{gdbserver} supports tracepoints, fast
18609 tracepoints and static tracepoints.
18611 For fast or static tracepoints to work, a special library called the
18612 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18613 This library is built and distributed as an integral part of
18614 @code{gdbserver}. In addition, support for static tracepoints
18615 requires building the in-process agent library with static tracepoints
18616 support. At present, the UST (LTTng Userspace Tracer,
18617 @url{http://lttng.org/ust}) tracing engine is supported. This support
18618 is automatically available if UST development headers are found in the
18619 standard include path when @code{gdbserver} is built, or if
18620 @code{gdbserver} was explicitly configured using @option{--with-ust}
18621 to point at such headers. You can explicitly disable the support
18622 using @option{--with-ust=no}.
18624 There are several ways to load the in-process agent in your program:
18627 @item Specifying it as dependency at link time
18629 You can link your program dynamically with the in-process agent
18630 library. On most systems, this is accomplished by adding
18631 @code{-linproctrace} to the link command.
18633 @item Using the system's preloading mechanisms
18635 You can force loading the in-process agent at startup time by using
18636 your system's support for preloading shared libraries. Many Unixes
18637 support the concept of preloading user defined libraries. In most
18638 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18639 in the environment. See also the description of @code{gdbserver}'s
18640 @option{--wrapper} command line option.
18642 @item Using @value{GDBN} to force loading the agent at run time
18644 On some systems, you can force the inferior to load a shared library,
18645 by calling a dynamic loader function in the inferior that takes care
18646 of dynamically looking up and loading a shared library. On most Unix
18647 systems, the function is @code{dlopen}. You'll use the @code{call}
18648 command for that. For example:
18651 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18654 Note that on most Unix systems, for the @code{dlopen} function to be
18655 available, the program needs to be linked with @code{-ldl}.
18658 On systems that have a userspace dynamic loader, like most Unix
18659 systems, when you connect to @code{gdbserver} using @code{target
18660 remote}, you'll find that the program is stopped at the dynamic
18661 loader's entry point, and no shared library has been loaded in the
18662 program's address space yet, including the in-process agent. In that
18663 case, before being able to use any of the fast or static tracepoints
18664 features, you need to let the loader run and load the shared
18665 libraries. The simplest way to do that is to run the program to the
18666 main procedure. E.g., if debugging a C or C@t{++} program, start
18667 @code{gdbserver} like so:
18670 $ gdbserver :9999 myprogram
18673 Start GDB and connect to @code{gdbserver} like so, and run to main:
18677 (@value{GDBP}) target remote myhost:9999
18678 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18679 (@value{GDBP}) b main
18680 (@value{GDBP}) continue
18683 The in-process tracing agent library should now be loaded into the
18684 process; you can confirm it with the @code{info sharedlibrary}
18685 command, which will list @file{libinproctrace.so} as loaded in the
18686 process. You are now ready to install fast tracepoints, list static
18687 tracepoint markers, probe static tracepoints markers, and start
18690 @node Remote Configuration
18691 @section Remote Configuration
18694 @kindex show remote
18695 This section documents the configuration options available when
18696 debugging remote programs. For the options related to the File I/O
18697 extensions of the remote protocol, see @ref{system,
18698 system-call-allowed}.
18701 @item set remoteaddresssize @var{bits}
18702 @cindex address size for remote targets
18703 @cindex bits in remote address
18704 Set the maximum size of address in a memory packet to the specified
18705 number of bits. @value{GDBN} will mask off the address bits above
18706 that number, when it passes addresses to the remote target. The
18707 default value is the number of bits in the target's address.
18709 @item show remoteaddresssize
18710 Show the current value of remote address size in bits.
18712 @item set serial baud @var{n}
18713 @cindex baud rate for remote targets
18714 Set the baud rate for the remote serial I/O to @var{n} baud. The
18715 value is used to set the speed of the serial port used for debugging
18718 @item show serial baud
18719 Show the current speed of the remote connection.
18721 @item set remotebreak
18722 @cindex interrupt remote programs
18723 @cindex BREAK signal instead of Ctrl-C
18724 @anchor{set remotebreak}
18725 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18726 when you type @kbd{Ctrl-c} to interrupt the program running
18727 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18728 character instead. The default is off, since most remote systems
18729 expect to see @samp{Ctrl-C} as the interrupt signal.
18731 @item show remotebreak
18732 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18733 interrupt the remote program.
18735 @item set remoteflow on
18736 @itemx set remoteflow off
18737 @kindex set remoteflow
18738 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18739 on the serial port used to communicate to the remote target.
18741 @item show remoteflow
18742 @kindex show remoteflow
18743 Show the current setting of hardware flow control.
18745 @item set remotelogbase @var{base}
18746 Set the base (a.k.a.@: radix) of logging serial protocol
18747 communications to @var{base}. Supported values of @var{base} are:
18748 @code{ascii}, @code{octal}, and @code{hex}. The default is
18751 @item show remotelogbase
18752 Show the current setting of the radix for logging remote serial
18755 @item set remotelogfile @var{file}
18756 @cindex record serial communications on file
18757 Record remote serial communications on the named @var{file}. The
18758 default is not to record at all.
18760 @item show remotelogfile.
18761 Show the current setting of the file name on which to record the
18762 serial communications.
18764 @item set remotetimeout @var{num}
18765 @cindex timeout for serial communications
18766 @cindex remote timeout
18767 Set the timeout limit to wait for the remote target to respond to
18768 @var{num} seconds. The default is 2 seconds.
18770 @item show remotetimeout
18771 Show the current number of seconds to wait for the remote target
18774 @cindex limit hardware breakpoints and watchpoints
18775 @cindex remote target, limit break- and watchpoints
18776 @anchor{set remote hardware-watchpoint-limit}
18777 @anchor{set remote hardware-breakpoint-limit}
18778 @item set remote hardware-watchpoint-limit @var{limit}
18779 @itemx set remote hardware-breakpoint-limit @var{limit}
18780 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18781 watchpoints. A limit of -1, the default, is treated as unlimited.
18783 @cindex limit hardware watchpoints length
18784 @cindex remote target, limit watchpoints length
18785 @anchor{set remote hardware-watchpoint-length-limit}
18786 @item set remote hardware-watchpoint-length-limit @var{limit}
18787 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18788 a remote hardware watchpoint. A limit of -1, the default, is treated
18791 @item show remote hardware-watchpoint-length-limit
18792 Show the current limit (in bytes) of the maximum length of
18793 a remote hardware watchpoint.
18795 @item set remote exec-file @var{filename}
18796 @itemx show remote exec-file
18797 @anchor{set remote exec-file}
18798 @cindex executable file, for remote target
18799 Select the file used for @code{run} with @code{target
18800 extended-remote}. This should be set to a filename valid on the
18801 target system. If it is not set, the target will use a default
18802 filename (e.g.@: the last program run).
18804 @item set remote interrupt-sequence
18805 @cindex interrupt remote programs
18806 @cindex select Ctrl-C, BREAK or BREAK-g
18807 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18808 @samp{BREAK-g} as the
18809 sequence to the remote target in order to interrupt the execution.
18810 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18811 is high level of serial line for some certain time.
18812 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18813 It is @code{BREAK} signal followed by character @code{g}.
18815 @item show interrupt-sequence
18816 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18817 is sent by @value{GDBN} to interrupt the remote program.
18818 @code{BREAK-g} is BREAK signal followed by @code{g} and
18819 also known as Magic SysRq g.
18821 @item set remote interrupt-on-connect
18822 @cindex send interrupt-sequence on start
18823 Specify whether interrupt-sequence is sent to remote target when
18824 @value{GDBN} connects to it. This is mostly needed when you debug
18825 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18826 which is known as Magic SysRq g in order to connect @value{GDBN}.
18828 @item show interrupt-on-connect
18829 Show whether interrupt-sequence is sent
18830 to remote target when @value{GDBN} connects to it.
18834 @item set tcp auto-retry on
18835 @cindex auto-retry, for remote TCP target
18836 Enable auto-retry for remote TCP connections. This is useful if the remote
18837 debugging agent is launched in parallel with @value{GDBN}; there is a race
18838 condition because the agent may not become ready to accept the connection
18839 before @value{GDBN} attempts to connect. When auto-retry is
18840 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18841 to establish the connection using the timeout specified by
18842 @code{set tcp connect-timeout}.
18844 @item set tcp auto-retry off
18845 Do not auto-retry failed TCP connections.
18847 @item show tcp auto-retry
18848 Show the current auto-retry setting.
18850 @item set tcp connect-timeout @var{seconds}
18851 @itemx set tcp connect-timeout unlimited
18852 @cindex connection timeout, for remote TCP target
18853 @cindex timeout, for remote target connection
18854 Set the timeout for establishing a TCP connection to the remote target to
18855 @var{seconds}. The timeout affects both polling to retry failed connections
18856 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18857 that are merely slow to complete, and represents an approximate cumulative
18858 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18859 @value{GDBN} will keep attempting to establish a connection forever,
18860 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18862 @item show tcp connect-timeout
18863 Show the current connection timeout setting.
18866 @cindex remote packets, enabling and disabling
18867 The @value{GDBN} remote protocol autodetects the packets supported by
18868 your debugging stub. If you need to override the autodetection, you
18869 can use these commands to enable or disable individual packets. Each
18870 packet can be set to @samp{on} (the remote target supports this
18871 packet), @samp{off} (the remote target does not support this packet),
18872 or @samp{auto} (detect remote target support for this packet). They
18873 all default to @samp{auto}. For more information about each packet,
18874 see @ref{Remote Protocol}.
18876 During normal use, you should not have to use any of these commands.
18877 If you do, that may be a bug in your remote debugging stub, or a bug
18878 in @value{GDBN}. You may want to report the problem to the
18879 @value{GDBN} developers.
18881 For each packet @var{name}, the command to enable or disable the
18882 packet is @code{set remote @var{name}-packet}. The available settings
18885 @multitable @columnfractions 0.28 0.32 0.25
18888 @tab Related Features
18890 @item @code{fetch-register}
18892 @tab @code{info registers}
18894 @item @code{set-register}
18898 @item @code{binary-download}
18900 @tab @code{load}, @code{set}
18902 @item @code{read-aux-vector}
18903 @tab @code{qXfer:auxv:read}
18904 @tab @code{info auxv}
18906 @item @code{symbol-lookup}
18907 @tab @code{qSymbol}
18908 @tab Detecting multiple threads
18910 @item @code{attach}
18911 @tab @code{vAttach}
18914 @item @code{verbose-resume}
18916 @tab Stepping or resuming multiple threads
18922 @item @code{software-breakpoint}
18926 @item @code{hardware-breakpoint}
18930 @item @code{write-watchpoint}
18934 @item @code{read-watchpoint}
18938 @item @code{access-watchpoint}
18942 @item @code{target-features}
18943 @tab @code{qXfer:features:read}
18944 @tab @code{set architecture}
18946 @item @code{library-info}
18947 @tab @code{qXfer:libraries:read}
18948 @tab @code{info sharedlibrary}
18950 @item @code{memory-map}
18951 @tab @code{qXfer:memory-map:read}
18952 @tab @code{info mem}
18954 @item @code{read-sdata-object}
18955 @tab @code{qXfer:sdata:read}
18956 @tab @code{print $_sdata}
18958 @item @code{read-spu-object}
18959 @tab @code{qXfer:spu:read}
18960 @tab @code{info spu}
18962 @item @code{write-spu-object}
18963 @tab @code{qXfer:spu:write}
18964 @tab @code{info spu}
18966 @item @code{read-siginfo-object}
18967 @tab @code{qXfer:siginfo:read}
18968 @tab @code{print $_siginfo}
18970 @item @code{write-siginfo-object}
18971 @tab @code{qXfer:siginfo:write}
18972 @tab @code{set $_siginfo}
18974 @item @code{threads}
18975 @tab @code{qXfer:threads:read}
18976 @tab @code{info threads}
18978 @item @code{get-thread-local-@*storage-address}
18979 @tab @code{qGetTLSAddr}
18980 @tab Displaying @code{__thread} variables
18982 @item @code{get-thread-information-block-address}
18983 @tab @code{qGetTIBAddr}
18984 @tab Display MS-Windows Thread Information Block.
18986 @item @code{search-memory}
18987 @tab @code{qSearch:memory}
18990 @item @code{supported-packets}
18991 @tab @code{qSupported}
18992 @tab Remote communications parameters
18994 @item @code{pass-signals}
18995 @tab @code{QPassSignals}
18996 @tab @code{handle @var{signal}}
18998 @item @code{program-signals}
18999 @tab @code{QProgramSignals}
19000 @tab @code{handle @var{signal}}
19002 @item @code{hostio-close-packet}
19003 @tab @code{vFile:close}
19004 @tab @code{remote get}, @code{remote put}
19006 @item @code{hostio-open-packet}
19007 @tab @code{vFile:open}
19008 @tab @code{remote get}, @code{remote put}
19010 @item @code{hostio-pread-packet}
19011 @tab @code{vFile:pread}
19012 @tab @code{remote get}, @code{remote put}
19014 @item @code{hostio-pwrite-packet}
19015 @tab @code{vFile:pwrite}
19016 @tab @code{remote get}, @code{remote put}
19018 @item @code{hostio-unlink-packet}
19019 @tab @code{vFile:unlink}
19020 @tab @code{remote delete}
19022 @item @code{hostio-readlink-packet}
19023 @tab @code{vFile:readlink}
19026 @item @code{noack-packet}
19027 @tab @code{QStartNoAckMode}
19028 @tab Packet acknowledgment
19030 @item @code{osdata}
19031 @tab @code{qXfer:osdata:read}
19032 @tab @code{info os}
19034 @item @code{query-attached}
19035 @tab @code{qAttached}
19036 @tab Querying remote process attach state.
19038 @item @code{trace-buffer-size}
19039 @tab @code{QTBuffer:size}
19040 @tab @code{set trace-buffer-size}
19042 @item @code{trace-status}
19043 @tab @code{qTStatus}
19044 @tab @code{tstatus}
19046 @item @code{traceframe-info}
19047 @tab @code{qXfer:traceframe-info:read}
19048 @tab Traceframe info
19050 @item @code{install-in-trace}
19051 @tab @code{InstallInTrace}
19052 @tab Install tracepoint in tracing
19054 @item @code{disable-randomization}
19055 @tab @code{QDisableRandomization}
19056 @tab @code{set disable-randomization}
19058 @item @code{conditional-breakpoints-packet}
19059 @tab @code{Z0 and Z1}
19060 @tab @code{Support for target-side breakpoint condition evaluation}
19064 @section Implementing a Remote Stub
19066 @cindex debugging stub, example
19067 @cindex remote stub, example
19068 @cindex stub example, remote debugging
19069 The stub files provided with @value{GDBN} implement the target side of the
19070 communication protocol, and the @value{GDBN} side is implemented in the
19071 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
19072 these subroutines to communicate, and ignore the details. (If you're
19073 implementing your own stub file, you can still ignore the details: start
19074 with one of the existing stub files. @file{sparc-stub.c} is the best
19075 organized, and therefore the easiest to read.)
19077 @cindex remote serial debugging, overview
19078 To debug a program running on another machine (the debugging
19079 @dfn{target} machine), you must first arrange for all the usual
19080 prerequisites for the program to run by itself. For example, for a C
19085 A startup routine to set up the C runtime environment; these usually
19086 have a name like @file{crt0}. The startup routine may be supplied by
19087 your hardware supplier, or you may have to write your own.
19090 A C subroutine library to support your program's
19091 subroutine calls, notably managing input and output.
19094 A way of getting your program to the other machine---for example, a
19095 download program. These are often supplied by the hardware
19096 manufacturer, but you may have to write your own from hardware
19100 The next step is to arrange for your program to use a serial port to
19101 communicate with the machine where @value{GDBN} is running (the @dfn{host}
19102 machine). In general terms, the scheme looks like this:
19106 @value{GDBN} already understands how to use this protocol; when everything
19107 else is set up, you can simply use the @samp{target remote} command
19108 (@pxref{Targets,,Specifying a Debugging Target}).
19110 @item On the target,
19111 you must link with your program a few special-purpose subroutines that
19112 implement the @value{GDBN} remote serial protocol. The file containing these
19113 subroutines is called a @dfn{debugging stub}.
19115 On certain remote targets, you can use an auxiliary program
19116 @code{gdbserver} instead of linking a stub into your program.
19117 @xref{Server,,Using the @code{gdbserver} Program}, for details.
19120 The debugging stub is specific to the architecture of the remote
19121 machine; for example, use @file{sparc-stub.c} to debug programs on
19124 @cindex remote serial stub list
19125 These working remote stubs are distributed with @value{GDBN}:
19130 @cindex @file{i386-stub.c}
19133 For Intel 386 and compatible architectures.
19136 @cindex @file{m68k-stub.c}
19137 @cindex Motorola 680x0
19139 For Motorola 680x0 architectures.
19142 @cindex @file{sh-stub.c}
19145 For Renesas SH architectures.
19148 @cindex @file{sparc-stub.c}
19150 For @sc{sparc} architectures.
19152 @item sparcl-stub.c
19153 @cindex @file{sparcl-stub.c}
19156 For Fujitsu @sc{sparclite} architectures.
19160 The @file{README} file in the @value{GDBN} distribution may list other
19161 recently added stubs.
19164 * Stub Contents:: What the stub can do for you
19165 * Bootstrapping:: What you must do for the stub
19166 * Debug Session:: Putting it all together
19169 @node Stub Contents
19170 @subsection What the Stub Can Do for You
19172 @cindex remote serial stub
19173 The debugging stub for your architecture supplies these three
19177 @item set_debug_traps
19178 @findex set_debug_traps
19179 @cindex remote serial stub, initialization
19180 This routine arranges for @code{handle_exception} to run when your
19181 program stops. You must call this subroutine explicitly in your
19182 program's startup code.
19184 @item handle_exception
19185 @findex handle_exception
19186 @cindex remote serial stub, main routine
19187 This is the central workhorse, but your program never calls it
19188 explicitly---the setup code arranges for @code{handle_exception} to
19189 run when a trap is triggered.
19191 @code{handle_exception} takes control when your program stops during
19192 execution (for example, on a breakpoint), and mediates communications
19193 with @value{GDBN} on the host machine. This is where the communications
19194 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
19195 representative on the target machine. It begins by sending summary
19196 information on the state of your program, then continues to execute,
19197 retrieving and transmitting any information @value{GDBN} needs, until you
19198 execute a @value{GDBN} command that makes your program resume; at that point,
19199 @code{handle_exception} returns control to your own code on the target
19203 @cindex @code{breakpoint} subroutine, remote
19204 Use this auxiliary subroutine to make your program contain a
19205 breakpoint. Depending on the particular situation, this may be the only
19206 way for @value{GDBN} to get control. For instance, if your target
19207 machine has some sort of interrupt button, you won't need to call this;
19208 pressing the interrupt button transfers control to
19209 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
19210 simply receiving characters on the serial port may also trigger a trap;
19211 again, in that situation, you don't need to call @code{breakpoint} from
19212 your own program---simply running @samp{target remote} from the host
19213 @value{GDBN} session gets control.
19215 Call @code{breakpoint} if none of these is true, or if you simply want
19216 to make certain your program stops at a predetermined point for the
19217 start of your debugging session.
19220 @node Bootstrapping
19221 @subsection What You Must Do for the Stub
19223 @cindex remote stub, support routines
19224 The debugging stubs that come with @value{GDBN} are set up for a particular
19225 chip architecture, but they have no information about the rest of your
19226 debugging target machine.
19228 First of all you need to tell the stub how to communicate with the
19232 @item int getDebugChar()
19233 @findex getDebugChar
19234 Write this subroutine to read a single character from the serial port.
19235 It may be identical to @code{getchar} for your target system; a
19236 different name is used to allow you to distinguish the two if you wish.
19238 @item void putDebugChar(int)
19239 @findex putDebugChar
19240 Write this subroutine to write a single character to the serial port.
19241 It may be identical to @code{putchar} for your target system; a
19242 different name is used to allow you to distinguish the two if you wish.
19245 @cindex control C, and remote debugging
19246 @cindex interrupting remote targets
19247 If you want @value{GDBN} to be able to stop your program while it is
19248 running, you need to use an interrupt-driven serial driver, and arrange
19249 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19250 character). That is the character which @value{GDBN} uses to tell the
19251 remote system to stop.
19253 Getting the debugging target to return the proper status to @value{GDBN}
19254 probably requires changes to the standard stub; one quick and dirty way
19255 is to just execute a breakpoint instruction (the ``dirty'' part is that
19256 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19258 Other routines you need to supply are:
19261 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19262 @findex exceptionHandler
19263 Write this function to install @var{exception_address} in the exception
19264 handling tables. You need to do this because the stub does not have any
19265 way of knowing what the exception handling tables on your target system
19266 are like (for example, the processor's table might be in @sc{rom},
19267 containing entries which point to a table in @sc{ram}).
19268 @var{exception_number} is the exception number which should be changed;
19269 its meaning is architecture-dependent (for example, different numbers
19270 might represent divide by zero, misaligned access, etc). When this
19271 exception occurs, control should be transferred directly to
19272 @var{exception_address}, and the processor state (stack, registers,
19273 and so on) should be just as it is when a processor exception occurs. So if
19274 you want to use a jump instruction to reach @var{exception_address}, it
19275 should be a simple jump, not a jump to subroutine.
19277 For the 386, @var{exception_address} should be installed as an interrupt
19278 gate so that interrupts are masked while the handler runs. The gate
19279 should be at privilege level 0 (the most privileged level). The
19280 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19281 help from @code{exceptionHandler}.
19283 @item void flush_i_cache()
19284 @findex flush_i_cache
19285 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19286 instruction cache, if any, on your target machine. If there is no
19287 instruction cache, this subroutine may be a no-op.
19289 On target machines that have instruction caches, @value{GDBN} requires this
19290 function to make certain that the state of your program is stable.
19294 You must also make sure this library routine is available:
19297 @item void *memset(void *, int, int)
19299 This is the standard library function @code{memset} that sets an area of
19300 memory to a known value. If you have one of the free versions of
19301 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19302 either obtain it from your hardware manufacturer, or write your own.
19305 If you do not use the GNU C compiler, you may need other standard
19306 library subroutines as well; this varies from one stub to another,
19307 but in general the stubs are likely to use any of the common library
19308 subroutines which @code{@value{NGCC}} generates as inline code.
19311 @node Debug Session
19312 @subsection Putting it All Together
19314 @cindex remote serial debugging summary
19315 In summary, when your program is ready to debug, you must follow these
19320 Make sure you have defined the supporting low-level routines
19321 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19323 @code{getDebugChar}, @code{putDebugChar},
19324 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19328 Insert these lines in your program's startup code, before the main
19329 procedure is called:
19336 On some machines, when a breakpoint trap is raised, the hardware
19337 automatically makes the PC point to the instruction after the
19338 breakpoint. If your machine doesn't do that, you may need to adjust
19339 @code{handle_exception} to arrange for it to return to the instruction
19340 after the breakpoint on this first invocation, so that your program
19341 doesn't keep hitting the initial breakpoint instead of making
19345 For the 680x0 stub only, you need to provide a variable called
19346 @code{exceptionHook}. Normally you just use:
19349 void (*exceptionHook)() = 0;
19353 but if before calling @code{set_debug_traps}, you set it to point to a
19354 function in your program, that function is called when
19355 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19356 error). The function indicated by @code{exceptionHook} is called with
19357 one parameter: an @code{int} which is the exception number.
19360 Compile and link together: your program, the @value{GDBN} debugging stub for
19361 your target architecture, and the supporting subroutines.
19364 Make sure you have a serial connection between your target machine and
19365 the @value{GDBN} host, and identify the serial port on the host.
19368 @c The "remote" target now provides a `load' command, so we should
19369 @c document that. FIXME.
19370 Download your program to your target machine (or get it there by
19371 whatever means the manufacturer provides), and start it.
19374 Start @value{GDBN} on the host, and connect to the target
19375 (@pxref{Connecting,,Connecting to a Remote Target}).
19379 @node Configurations
19380 @chapter Configuration-Specific Information
19382 While nearly all @value{GDBN} commands are available for all native and
19383 cross versions of the debugger, there are some exceptions. This chapter
19384 describes things that are only available in certain configurations.
19386 There are three major categories of configurations: native
19387 configurations, where the host and target are the same, embedded
19388 operating system configurations, which are usually the same for several
19389 different processor architectures, and bare embedded processors, which
19390 are quite different from each other.
19395 * Embedded Processors::
19402 This section describes details specific to particular native
19407 * BSD libkvm Interface:: Debugging BSD kernel memory images
19408 * SVR4 Process Information:: SVR4 process information
19409 * DJGPP Native:: Features specific to the DJGPP port
19410 * Cygwin Native:: Features specific to the Cygwin port
19411 * Hurd Native:: Features specific to @sc{gnu} Hurd
19412 * Darwin:: Features specific to Darwin
19418 On HP-UX systems, if you refer to a function or variable name that
19419 begins with a dollar sign, @value{GDBN} searches for a user or system
19420 name first, before it searches for a convenience variable.
19423 @node BSD libkvm Interface
19424 @subsection BSD libkvm Interface
19427 @cindex kernel memory image
19428 @cindex kernel crash dump
19430 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19431 interface that provides a uniform interface for accessing kernel virtual
19432 memory images, including live systems and crash dumps. @value{GDBN}
19433 uses this interface to allow you to debug live kernels and kernel crash
19434 dumps on many native BSD configurations. This is implemented as a
19435 special @code{kvm} debugging target. For debugging a live system, load
19436 the currently running kernel into @value{GDBN} and connect to the
19440 (@value{GDBP}) @b{target kvm}
19443 For debugging crash dumps, provide the file name of the crash dump as an
19447 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19450 Once connected to the @code{kvm} target, the following commands are
19456 Set current context from the @dfn{Process Control Block} (PCB) address.
19459 Set current context from proc address. This command isn't available on
19460 modern FreeBSD systems.
19463 @node SVR4 Process Information
19464 @subsection SVR4 Process Information
19466 @cindex examine process image
19467 @cindex process info via @file{/proc}
19469 Many versions of SVR4 and compatible systems provide a facility called
19470 @samp{/proc} that can be used to examine the image of a running
19471 process using file-system subroutines.
19473 If @value{GDBN} is configured for an operating system with this
19474 facility, the command @code{info proc} is available to report
19475 information about the process running your program, or about any
19476 process running on your system. This includes, as of this writing,
19477 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19478 not HP-UX, for example.
19480 This command may also work on core files that were created on a system
19481 that has the @samp{/proc} facility.
19487 @itemx info proc @var{process-id}
19488 Summarize available information about any running process. If a
19489 process ID is specified by @var{process-id}, display information about
19490 that process; otherwise display information about the program being
19491 debugged. The summary includes the debugged process ID, the command
19492 line used to invoke it, its current working directory, and its
19493 executable file's absolute file name.
19495 On some systems, @var{process-id} can be of the form
19496 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19497 within a process. If the optional @var{pid} part is missing, it means
19498 a thread from the process being debugged (the leading @samp{/} still
19499 needs to be present, or else @value{GDBN} will interpret the number as
19500 a process ID rather than a thread ID).
19502 @item info proc cmdline
19503 @cindex info proc cmdline
19504 Show the original command line of the process. This command is
19505 specific to @sc{gnu}/Linux.
19507 @item info proc cwd
19508 @cindex info proc cwd
19509 Show the current working directory of the process. This command is
19510 specific to @sc{gnu}/Linux.
19512 @item info proc exe
19513 @cindex info proc exe
19514 Show the name of executable of the process. This command is specific
19517 @item info proc mappings
19518 @cindex memory address space mappings
19519 Report the memory address space ranges accessible in the program, with
19520 information on whether the process has read, write, or execute access
19521 rights to each range. On @sc{gnu}/Linux systems, each memory range
19522 includes the object file which is mapped to that range, instead of the
19523 memory access rights to that range.
19525 @item info proc stat
19526 @itemx info proc status
19527 @cindex process detailed status information
19528 These subcommands are specific to @sc{gnu}/Linux systems. They show
19529 the process-related information, including the user ID and group ID;
19530 how many threads are there in the process; its virtual memory usage;
19531 the signals that are pending, blocked, and ignored; its TTY; its
19532 consumption of system and user time; its stack size; its @samp{nice}
19533 value; etc. For more information, see the @samp{proc} man page
19534 (type @kbd{man 5 proc} from your shell prompt).
19536 @item info proc all
19537 Show all the information about the process described under all of the
19538 above @code{info proc} subcommands.
19541 @comment These sub-options of 'info proc' were not included when
19542 @comment procfs.c was re-written. Keep their descriptions around
19543 @comment against the day when someone finds the time to put them back in.
19544 @kindex info proc times
19545 @item info proc times
19546 Starting time, user CPU time, and system CPU time for your program and
19549 @kindex info proc id
19551 Report on the process IDs related to your program: its own process ID,
19552 the ID of its parent, the process group ID, and the session ID.
19555 @item set procfs-trace
19556 @kindex set procfs-trace
19557 @cindex @code{procfs} API calls
19558 This command enables and disables tracing of @code{procfs} API calls.
19560 @item show procfs-trace
19561 @kindex show procfs-trace
19562 Show the current state of @code{procfs} API call tracing.
19564 @item set procfs-file @var{file}
19565 @kindex set procfs-file
19566 Tell @value{GDBN} to write @code{procfs} API trace to the named
19567 @var{file}. @value{GDBN} appends the trace info to the previous
19568 contents of the file. The default is to display the trace on the
19571 @item show procfs-file
19572 @kindex show procfs-file
19573 Show the file to which @code{procfs} API trace is written.
19575 @item proc-trace-entry
19576 @itemx proc-trace-exit
19577 @itemx proc-untrace-entry
19578 @itemx proc-untrace-exit
19579 @kindex proc-trace-entry
19580 @kindex proc-trace-exit
19581 @kindex proc-untrace-entry
19582 @kindex proc-untrace-exit
19583 These commands enable and disable tracing of entries into and exits
19584 from the @code{syscall} interface.
19587 @kindex info pidlist
19588 @cindex process list, QNX Neutrino
19589 For QNX Neutrino only, this command displays the list of all the
19590 processes and all the threads within each process.
19593 @kindex info meminfo
19594 @cindex mapinfo list, QNX Neutrino
19595 For QNX Neutrino only, this command displays the list of all mapinfos.
19599 @subsection Features for Debugging @sc{djgpp} Programs
19600 @cindex @sc{djgpp} debugging
19601 @cindex native @sc{djgpp} debugging
19602 @cindex MS-DOS-specific commands
19605 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19606 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19607 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19608 top of real-mode DOS systems and their emulations.
19610 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19611 defines a few commands specific to the @sc{djgpp} port. This
19612 subsection describes those commands.
19617 This is a prefix of @sc{djgpp}-specific commands which print
19618 information about the target system and important OS structures.
19621 @cindex MS-DOS system info
19622 @cindex free memory information (MS-DOS)
19623 @item info dos sysinfo
19624 This command displays assorted information about the underlying
19625 platform: the CPU type and features, the OS version and flavor, the
19626 DPMI version, and the available conventional and DPMI memory.
19631 @cindex segment descriptor tables
19632 @cindex descriptor tables display
19634 @itemx info dos ldt
19635 @itemx info dos idt
19636 These 3 commands display entries from, respectively, Global, Local,
19637 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19638 tables are data structures which store a descriptor for each segment
19639 that is currently in use. The segment's selector is an index into a
19640 descriptor table; the table entry for that index holds the
19641 descriptor's base address and limit, and its attributes and access
19644 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19645 segment (used for both data and the stack), and a DOS segment (which
19646 allows access to DOS/BIOS data structures and absolute addresses in
19647 conventional memory). However, the DPMI host will usually define
19648 additional segments in order to support the DPMI environment.
19650 @cindex garbled pointers
19651 These commands allow to display entries from the descriptor tables.
19652 Without an argument, all entries from the specified table are
19653 displayed. An argument, which should be an integer expression, means
19654 display a single entry whose index is given by the argument. For
19655 example, here's a convenient way to display information about the
19656 debugged program's data segment:
19659 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19660 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19664 This comes in handy when you want to see whether a pointer is outside
19665 the data segment's limit (i.e.@: @dfn{garbled}).
19667 @cindex page tables display (MS-DOS)
19669 @itemx info dos pte
19670 These two commands display entries from, respectively, the Page
19671 Directory and the Page Tables. Page Directories and Page Tables are
19672 data structures which control how virtual memory addresses are mapped
19673 into physical addresses. A Page Table includes an entry for every
19674 page of memory that is mapped into the program's address space; there
19675 may be several Page Tables, each one holding up to 4096 entries. A
19676 Page Directory has up to 4096 entries, one each for every Page Table
19677 that is currently in use.
19679 Without an argument, @kbd{info dos pde} displays the entire Page
19680 Directory, and @kbd{info dos pte} displays all the entries in all of
19681 the Page Tables. An argument, an integer expression, given to the
19682 @kbd{info dos pde} command means display only that entry from the Page
19683 Directory table. An argument given to the @kbd{info dos pte} command
19684 means display entries from a single Page Table, the one pointed to by
19685 the specified entry in the Page Directory.
19687 @cindex direct memory access (DMA) on MS-DOS
19688 These commands are useful when your program uses @dfn{DMA} (Direct
19689 Memory Access), which needs physical addresses to program the DMA
19692 These commands are supported only with some DPMI servers.
19694 @cindex physical address from linear address
19695 @item info dos address-pte @var{addr}
19696 This command displays the Page Table entry for a specified linear
19697 address. The argument @var{addr} is a linear address which should
19698 already have the appropriate segment's base address added to it,
19699 because this command accepts addresses which may belong to @emph{any}
19700 segment. For example, here's how to display the Page Table entry for
19701 the page where a variable @code{i} is stored:
19704 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19705 @exdent @code{Page Table entry for address 0x11a00d30:}
19706 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19710 This says that @code{i} is stored at offset @code{0xd30} from the page
19711 whose physical base address is @code{0x02698000}, and shows all the
19712 attributes of that page.
19714 Note that you must cast the addresses of variables to a @code{char *},
19715 since otherwise the value of @code{__djgpp_base_address}, the base
19716 address of all variables and functions in a @sc{djgpp} program, will
19717 be added using the rules of C pointer arithmetics: if @code{i} is
19718 declared an @code{int}, @value{GDBN} will add 4 times the value of
19719 @code{__djgpp_base_address} to the address of @code{i}.
19721 Here's another example, it displays the Page Table entry for the
19725 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19726 @exdent @code{Page Table entry for address 0x29110:}
19727 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19731 (The @code{+ 3} offset is because the transfer buffer's address is the
19732 3rd member of the @code{_go32_info_block} structure.) The output
19733 clearly shows that this DPMI server maps the addresses in conventional
19734 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19735 linear (@code{0x29110}) addresses are identical.
19737 This command is supported only with some DPMI servers.
19740 @cindex DOS serial data link, remote debugging
19741 In addition to native debugging, the DJGPP port supports remote
19742 debugging via a serial data link. The following commands are specific
19743 to remote serial debugging in the DJGPP port of @value{GDBN}.
19746 @kindex set com1base
19747 @kindex set com1irq
19748 @kindex set com2base
19749 @kindex set com2irq
19750 @kindex set com3base
19751 @kindex set com3irq
19752 @kindex set com4base
19753 @kindex set com4irq
19754 @item set com1base @var{addr}
19755 This command sets the base I/O port address of the @file{COM1} serial
19758 @item set com1irq @var{irq}
19759 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19760 for the @file{COM1} serial port.
19762 There are similar commands @samp{set com2base}, @samp{set com3irq},
19763 etc.@: for setting the port address and the @code{IRQ} lines for the
19766 @kindex show com1base
19767 @kindex show com1irq
19768 @kindex show com2base
19769 @kindex show com2irq
19770 @kindex show com3base
19771 @kindex show com3irq
19772 @kindex show com4base
19773 @kindex show com4irq
19774 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19775 display the current settings of the base address and the @code{IRQ}
19776 lines used by the COM ports.
19779 @kindex info serial
19780 @cindex DOS serial port status
19781 This command prints the status of the 4 DOS serial ports. For each
19782 port, it prints whether it's active or not, its I/O base address and
19783 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19784 counts of various errors encountered so far.
19788 @node Cygwin Native
19789 @subsection Features for Debugging MS Windows PE Executables
19790 @cindex MS Windows debugging
19791 @cindex native Cygwin debugging
19792 @cindex Cygwin-specific commands
19794 @value{GDBN} supports native debugging of MS Windows programs, including
19795 DLLs with and without symbolic debugging information.
19797 @cindex Ctrl-BREAK, MS-Windows
19798 @cindex interrupt debuggee on MS-Windows
19799 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19800 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19801 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19802 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19803 sequence, which can be used to interrupt the debuggee even if it
19806 There are various additional Cygwin-specific commands, described in
19807 this section. Working with DLLs that have no debugging symbols is
19808 described in @ref{Non-debug DLL Symbols}.
19813 This is a prefix of MS Windows-specific commands which print
19814 information about the target system and important OS structures.
19816 @item info w32 selector
19817 This command displays information returned by
19818 the Win32 API @code{GetThreadSelectorEntry} function.
19819 It takes an optional argument that is evaluated to
19820 a long value to give the information about this given selector.
19821 Without argument, this command displays information
19822 about the six segment registers.
19824 @item info w32 thread-information-block
19825 This command displays thread specific information stored in the
19826 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19827 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19831 This is a Cygwin-specific alias of @code{info shared}.
19833 @kindex dll-symbols
19835 This command loads symbols from a dll similarly to
19836 add-sym command but without the need to specify a base address.
19838 @kindex set cygwin-exceptions
19839 @cindex debugging the Cygwin DLL
19840 @cindex Cygwin DLL, debugging
19841 @item set cygwin-exceptions @var{mode}
19842 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19843 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19844 @value{GDBN} will delay recognition of exceptions, and may ignore some
19845 exceptions which seem to be caused by internal Cygwin DLL
19846 ``bookkeeping''. This option is meant primarily for debugging the
19847 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19848 @value{GDBN} users with false @code{SIGSEGV} signals.
19850 @kindex show cygwin-exceptions
19851 @item show cygwin-exceptions
19852 Displays whether @value{GDBN} will break on exceptions that happen
19853 inside the Cygwin DLL itself.
19855 @kindex set new-console
19856 @item set new-console @var{mode}
19857 If @var{mode} is @code{on} the debuggee will
19858 be started in a new console on next start.
19859 If @var{mode} is @code{off}, the debuggee will
19860 be started in the same console as the debugger.
19862 @kindex show new-console
19863 @item show new-console
19864 Displays whether a new console is used
19865 when the debuggee is started.
19867 @kindex set new-group
19868 @item set new-group @var{mode}
19869 This boolean value controls whether the debuggee should
19870 start a new group or stay in the same group as the debugger.
19871 This affects the way the Windows OS handles
19874 @kindex show new-group
19875 @item show new-group
19876 Displays current value of new-group boolean.
19878 @kindex set debugevents
19879 @item set debugevents
19880 This boolean value adds debug output concerning kernel events related
19881 to the debuggee seen by the debugger. This includes events that
19882 signal thread and process creation and exit, DLL loading and
19883 unloading, console interrupts, and debugging messages produced by the
19884 Windows @code{OutputDebugString} API call.
19886 @kindex set debugexec
19887 @item set debugexec
19888 This boolean value adds debug output concerning execute events
19889 (such as resume thread) seen by the debugger.
19891 @kindex set debugexceptions
19892 @item set debugexceptions
19893 This boolean value adds debug output concerning exceptions in the
19894 debuggee seen by the debugger.
19896 @kindex set debugmemory
19897 @item set debugmemory
19898 This boolean value adds debug output concerning debuggee memory reads
19899 and writes by the debugger.
19903 This boolean values specifies whether the debuggee is called
19904 via a shell or directly (default value is on).
19908 Displays if the debuggee will be started with a shell.
19913 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19916 @node Non-debug DLL Symbols
19917 @subsubsection Support for DLLs without Debugging Symbols
19918 @cindex DLLs with no debugging symbols
19919 @cindex Minimal symbols and DLLs
19921 Very often on windows, some of the DLLs that your program relies on do
19922 not include symbolic debugging information (for example,
19923 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19924 symbols in a DLL, it relies on the minimal amount of symbolic
19925 information contained in the DLL's export table. This section
19926 describes working with such symbols, known internally to @value{GDBN} as
19927 ``minimal symbols''.
19929 Note that before the debugged program has started execution, no DLLs
19930 will have been loaded. The easiest way around this problem is simply to
19931 start the program --- either by setting a breakpoint or letting the
19932 program run once to completion. It is also possible to force
19933 @value{GDBN} to load a particular DLL before starting the executable ---
19934 see the shared library information in @ref{Files}, or the
19935 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19936 explicitly loading symbols from a DLL with no debugging information will
19937 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19938 which may adversely affect symbol lookup performance.
19940 @subsubsection DLL Name Prefixes
19942 In keeping with the naming conventions used by the Microsoft debugging
19943 tools, DLL export symbols are made available with a prefix based on the
19944 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19945 also entered into the symbol table, so @code{CreateFileA} is often
19946 sufficient. In some cases there will be name clashes within a program
19947 (particularly if the executable itself includes full debugging symbols)
19948 necessitating the use of the fully qualified name when referring to the
19949 contents of the DLL. Use single-quotes around the name to avoid the
19950 exclamation mark (``!'') being interpreted as a language operator.
19952 Note that the internal name of the DLL may be all upper-case, even
19953 though the file name of the DLL is lower-case, or vice-versa. Since
19954 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19955 some confusion. If in doubt, try the @code{info functions} and
19956 @code{info variables} commands or even @code{maint print msymbols}
19957 (@pxref{Symbols}). Here's an example:
19960 (@value{GDBP}) info function CreateFileA
19961 All functions matching regular expression "CreateFileA":
19963 Non-debugging symbols:
19964 0x77e885f4 CreateFileA
19965 0x77e885f4 KERNEL32!CreateFileA
19969 (@value{GDBP}) info function !
19970 All functions matching regular expression "!":
19972 Non-debugging symbols:
19973 0x6100114c cygwin1!__assert
19974 0x61004034 cygwin1!_dll_crt0@@0
19975 0x61004240 cygwin1!dll_crt0(per_process *)
19979 @subsubsection Working with Minimal Symbols
19981 Symbols extracted from a DLL's export table do not contain very much
19982 type information. All that @value{GDBN} can do is guess whether a symbol
19983 refers to a function or variable depending on the linker section that
19984 contains the symbol. Also note that the actual contents of the memory
19985 contained in a DLL are not available unless the program is running. This
19986 means that you cannot examine the contents of a variable or disassemble
19987 a function within a DLL without a running program.
19989 Variables are generally treated as pointers and dereferenced
19990 automatically. For this reason, it is often necessary to prefix a
19991 variable name with the address-of operator (``&'') and provide explicit
19992 type information in the command. Here's an example of the type of
19996 (@value{GDBP}) print 'cygwin1!__argv'
20001 (@value{GDBP}) x 'cygwin1!__argv'
20002 0x10021610: "\230y\""
20005 And two possible solutions:
20008 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
20009 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
20013 (@value{GDBP}) x/2x &'cygwin1!__argv'
20014 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
20015 (@value{GDBP}) x/x 0x10021608
20016 0x10021608: 0x0022fd98
20017 (@value{GDBP}) x/s 0x0022fd98
20018 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
20021 Setting a break point within a DLL is possible even before the program
20022 starts execution. However, under these circumstances, @value{GDBN} can't
20023 examine the initial instructions of the function in order to skip the
20024 function's frame set-up code. You can work around this by using ``*&''
20025 to set the breakpoint at a raw memory address:
20028 (@value{GDBP}) break *&'python22!PyOS_Readline'
20029 Breakpoint 1 at 0x1e04eff0
20032 The author of these extensions is not entirely convinced that setting a
20033 break point within a shared DLL like @file{kernel32.dll} is completely
20037 @subsection Commands Specific to @sc{gnu} Hurd Systems
20038 @cindex @sc{gnu} Hurd debugging
20040 This subsection describes @value{GDBN} commands specific to the
20041 @sc{gnu} Hurd native debugging.
20046 @kindex set signals@r{, Hurd command}
20047 @kindex set sigs@r{, Hurd command}
20048 This command toggles the state of inferior signal interception by
20049 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
20050 affected by this command. @code{sigs} is a shorthand alias for
20055 @kindex show signals@r{, Hurd command}
20056 @kindex show sigs@r{, Hurd command}
20057 Show the current state of intercepting inferior's signals.
20059 @item set signal-thread
20060 @itemx set sigthread
20061 @kindex set signal-thread
20062 @kindex set sigthread
20063 This command tells @value{GDBN} which thread is the @code{libc} signal
20064 thread. That thread is run when a signal is delivered to a running
20065 process. @code{set sigthread} is the shorthand alias of @code{set
20068 @item show signal-thread
20069 @itemx show sigthread
20070 @kindex show signal-thread
20071 @kindex show sigthread
20072 These two commands show which thread will run when the inferior is
20073 delivered a signal.
20076 @kindex set stopped@r{, Hurd command}
20077 This commands tells @value{GDBN} that the inferior process is stopped,
20078 as with the @code{SIGSTOP} signal. The stopped process can be
20079 continued by delivering a signal to it.
20082 @kindex show stopped@r{, Hurd command}
20083 This command shows whether @value{GDBN} thinks the debuggee is
20086 @item set exceptions
20087 @kindex set exceptions@r{, Hurd command}
20088 Use this command to turn off trapping of exceptions in the inferior.
20089 When exception trapping is off, neither breakpoints nor
20090 single-stepping will work. To restore the default, set exception
20093 @item show exceptions
20094 @kindex show exceptions@r{, Hurd command}
20095 Show the current state of trapping exceptions in the inferior.
20097 @item set task pause
20098 @kindex set task@r{, Hurd commands}
20099 @cindex task attributes (@sc{gnu} Hurd)
20100 @cindex pause current task (@sc{gnu} Hurd)
20101 This command toggles task suspension when @value{GDBN} has control.
20102 Setting it to on takes effect immediately, and the task is suspended
20103 whenever @value{GDBN} gets control. Setting it to off will take
20104 effect the next time the inferior is continued. If this option is set
20105 to off, you can use @code{set thread default pause on} or @code{set
20106 thread pause on} (see below) to pause individual threads.
20108 @item show task pause
20109 @kindex show task@r{, Hurd commands}
20110 Show the current state of task suspension.
20112 @item set task detach-suspend-count
20113 @cindex task suspend count
20114 @cindex detach from task, @sc{gnu} Hurd
20115 This command sets the suspend count the task will be left with when
20116 @value{GDBN} detaches from it.
20118 @item show task detach-suspend-count
20119 Show the suspend count the task will be left with when detaching.
20121 @item set task exception-port
20122 @itemx set task excp
20123 @cindex task exception port, @sc{gnu} Hurd
20124 This command sets the task exception port to which @value{GDBN} will
20125 forward exceptions. The argument should be the value of the @dfn{send
20126 rights} of the task. @code{set task excp} is a shorthand alias.
20128 @item set noninvasive
20129 @cindex noninvasive task options
20130 This command switches @value{GDBN} to a mode that is the least
20131 invasive as far as interfering with the inferior is concerned. This
20132 is the same as using @code{set task pause}, @code{set exceptions}, and
20133 @code{set signals} to values opposite to the defaults.
20135 @item info send-rights
20136 @itemx info receive-rights
20137 @itemx info port-rights
20138 @itemx info port-sets
20139 @itemx info dead-names
20142 @cindex send rights, @sc{gnu} Hurd
20143 @cindex receive rights, @sc{gnu} Hurd
20144 @cindex port rights, @sc{gnu} Hurd
20145 @cindex port sets, @sc{gnu} Hurd
20146 @cindex dead names, @sc{gnu} Hurd
20147 These commands display information about, respectively, send rights,
20148 receive rights, port rights, port sets, and dead names of a task.
20149 There are also shorthand aliases: @code{info ports} for @code{info
20150 port-rights} and @code{info psets} for @code{info port-sets}.
20152 @item set thread pause
20153 @kindex set thread@r{, Hurd command}
20154 @cindex thread properties, @sc{gnu} Hurd
20155 @cindex pause current thread (@sc{gnu} Hurd)
20156 This command toggles current thread suspension when @value{GDBN} has
20157 control. Setting it to on takes effect immediately, and the current
20158 thread is suspended whenever @value{GDBN} gets control. Setting it to
20159 off will take effect the next time the inferior is continued.
20160 Normally, this command has no effect, since when @value{GDBN} has
20161 control, the whole task is suspended. However, if you used @code{set
20162 task pause off} (see above), this command comes in handy to suspend
20163 only the current thread.
20165 @item show thread pause
20166 @kindex show thread@r{, Hurd command}
20167 This command shows the state of current thread suspension.
20169 @item set thread run
20170 This command sets whether the current thread is allowed to run.
20172 @item show thread run
20173 Show whether the current thread is allowed to run.
20175 @item set thread detach-suspend-count
20176 @cindex thread suspend count, @sc{gnu} Hurd
20177 @cindex detach from thread, @sc{gnu} Hurd
20178 This command sets the suspend count @value{GDBN} will leave on a
20179 thread when detaching. This number is relative to the suspend count
20180 found by @value{GDBN} when it notices the thread; use @code{set thread
20181 takeover-suspend-count} to force it to an absolute value.
20183 @item show thread detach-suspend-count
20184 Show the suspend count @value{GDBN} will leave on the thread when
20187 @item set thread exception-port
20188 @itemx set thread excp
20189 Set the thread exception port to which to forward exceptions. This
20190 overrides the port set by @code{set task exception-port} (see above).
20191 @code{set thread excp} is the shorthand alias.
20193 @item set thread takeover-suspend-count
20194 Normally, @value{GDBN}'s thread suspend counts are relative to the
20195 value @value{GDBN} finds when it notices each thread. This command
20196 changes the suspend counts to be absolute instead.
20198 @item set thread default
20199 @itemx show thread default
20200 @cindex thread default settings, @sc{gnu} Hurd
20201 Each of the above @code{set thread} commands has a @code{set thread
20202 default} counterpart (e.g., @code{set thread default pause}, @code{set
20203 thread default exception-port}, etc.). The @code{thread default}
20204 variety of commands sets the default thread properties for all
20205 threads; you can then change the properties of individual threads with
20206 the non-default commands.
20213 @value{GDBN} provides the following commands specific to the Darwin target:
20216 @item set debug darwin @var{num}
20217 @kindex set debug darwin
20218 When set to a non zero value, enables debugging messages specific to
20219 the Darwin support. Higher values produce more verbose output.
20221 @item show debug darwin
20222 @kindex show debug darwin
20223 Show the current state of Darwin messages.
20225 @item set debug mach-o @var{num}
20226 @kindex set debug mach-o
20227 When set to a non zero value, enables debugging messages while
20228 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
20229 file format used on Darwin for object and executable files.) Higher
20230 values produce more verbose output. This is a command to diagnose
20231 problems internal to @value{GDBN} and should not be needed in normal
20234 @item show debug mach-o
20235 @kindex show debug mach-o
20236 Show the current state of Mach-O file messages.
20238 @item set mach-exceptions on
20239 @itemx set mach-exceptions off
20240 @kindex set mach-exceptions
20241 On Darwin, faults are first reported as a Mach exception and are then
20242 mapped to a Posix signal. Use this command to turn on trapping of
20243 Mach exceptions in the inferior. This might be sometimes useful to
20244 better understand the cause of a fault. The default is off.
20246 @item show mach-exceptions
20247 @kindex show mach-exceptions
20248 Show the current state of exceptions trapping.
20253 @section Embedded Operating Systems
20255 This section describes configurations involving the debugging of
20256 embedded operating systems that are available for several different
20260 * VxWorks:: Using @value{GDBN} with VxWorks
20263 @value{GDBN} includes the ability to debug programs running on
20264 various real-time operating systems.
20267 @subsection Using @value{GDBN} with VxWorks
20273 @kindex target vxworks
20274 @item target vxworks @var{machinename}
20275 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20276 is the target system's machine name or IP address.
20280 On VxWorks, @code{load} links @var{filename} dynamically on the
20281 current target system as well as adding its symbols in @value{GDBN}.
20283 @value{GDBN} enables developers to spawn and debug tasks running on networked
20284 VxWorks targets from a Unix host. Already-running tasks spawned from
20285 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20286 both the Unix host and on the VxWorks target. The program
20287 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20288 installed with the name @code{vxgdb}, to distinguish it from a
20289 @value{GDBN} for debugging programs on the host itself.)
20292 @item VxWorks-timeout @var{args}
20293 @kindex vxworks-timeout
20294 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20295 This option is set by the user, and @var{args} represents the number of
20296 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20297 your VxWorks target is a slow software simulator or is on the far side
20298 of a thin network line.
20301 The following information on connecting to VxWorks was current when
20302 this manual was produced; newer releases of VxWorks may use revised
20305 @findex INCLUDE_RDB
20306 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20307 to include the remote debugging interface routines in the VxWorks
20308 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20309 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20310 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20311 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20312 information on configuring and remaking VxWorks, see the manufacturer's
20314 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20316 Once you have included @file{rdb.a} in your VxWorks system image and set
20317 your Unix execution search path to find @value{GDBN}, you are ready to
20318 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20319 @code{vxgdb}, depending on your installation).
20321 @value{GDBN} comes up showing the prompt:
20328 * VxWorks Connection:: Connecting to VxWorks
20329 * VxWorks Download:: VxWorks download
20330 * VxWorks Attach:: Running tasks
20333 @node VxWorks Connection
20334 @subsubsection Connecting to VxWorks
20336 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20337 network. To connect to a target whose host name is ``@code{tt}'', type:
20340 (vxgdb) target vxworks tt
20344 @value{GDBN} displays messages like these:
20347 Attaching remote machine across net...
20352 @value{GDBN} then attempts to read the symbol tables of any object modules
20353 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20354 these files by searching the directories listed in the command search
20355 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20356 to find an object file, it displays a message such as:
20359 prog.o: No such file or directory.
20362 When this happens, add the appropriate directory to the search path with
20363 the @value{GDBN} command @code{path}, and execute the @code{target}
20366 @node VxWorks Download
20367 @subsubsection VxWorks Download
20369 @cindex download to VxWorks
20370 If you have connected to the VxWorks target and you want to debug an
20371 object that has not yet been loaded, you can use the @value{GDBN}
20372 @code{load} command to download a file from Unix to VxWorks
20373 incrementally. The object file given as an argument to the @code{load}
20374 command is actually opened twice: first by the VxWorks target in order
20375 to download the code, then by @value{GDBN} in order to read the symbol
20376 table. This can lead to problems if the current working directories on
20377 the two systems differ. If both systems have NFS mounted the same
20378 filesystems, you can avoid these problems by using absolute paths.
20379 Otherwise, it is simplest to set the working directory on both systems
20380 to the directory in which the object file resides, and then to reference
20381 the file by its name, without any path. For instance, a program
20382 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20383 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20384 program, type this on VxWorks:
20387 -> cd "@var{vxpath}/vw/demo/rdb"
20391 Then, in @value{GDBN}, type:
20394 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20395 (vxgdb) load prog.o
20398 @value{GDBN} displays a response similar to this:
20401 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20404 You can also use the @code{load} command to reload an object module
20405 after editing and recompiling the corresponding source file. Note that
20406 this makes @value{GDBN} delete all currently-defined breakpoints,
20407 auto-displays, and convenience variables, and to clear the value
20408 history. (This is necessary in order to preserve the integrity of
20409 debugger's data structures that reference the target system's symbol
20412 @node VxWorks Attach
20413 @subsubsection Running Tasks
20415 @cindex running VxWorks tasks
20416 You can also attach to an existing task using the @code{attach} command as
20420 (vxgdb) attach @var{task}
20424 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20425 or suspended when you attach to it. Running tasks are suspended at
20426 the time of attachment.
20428 @node Embedded Processors
20429 @section Embedded Processors
20431 This section goes into details specific to particular embedded
20434 @cindex send command to simulator
20435 Whenever a specific embedded processor has a simulator, @value{GDBN}
20436 allows to send an arbitrary command to the simulator.
20439 @item sim @var{command}
20440 @kindex sim@r{, a command}
20441 Send an arbitrary @var{command} string to the simulator. Consult the
20442 documentation for the specific simulator in use for information about
20443 acceptable commands.
20449 * M32R/D:: Renesas M32R/D
20450 * M68K:: Motorola M68K
20451 * MicroBlaze:: Xilinx MicroBlaze
20452 * MIPS Embedded:: MIPS Embedded
20453 * PowerPC Embedded:: PowerPC Embedded
20454 * PA:: HP PA Embedded
20455 * Sparclet:: Tsqware Sparclet
20456 * Sparclite:: Fujitsu Sparclite
20457 * Z8000:: Zilog Z8000
20460 * Super-H:: Renesas Super-H
20469 @item target rdi @var{dev}
20470 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20471 use this target to communicate with both boards running the Angel
20472 monitor, or with the EmbeddedICE JTAG debug device.
20475 @item target rdp @var{dev}
20480 @value{GDBN} provides the following ARM-specific commands:
20483 @item set arm disassembler
20485 This commands selects from a list of disassembly styles. The
20486 @code{"std"} style is the standard style.
20488 @item show arm disassembler
20490 Show the current disassembly style.
20492 @item set arm apcs32
20493 @cindex ARM 32-bit mode
20494 This command toggles ARM operation mode between 32-bit and 26-bit.
20496 @item show arm apcs32
20497 Display the current usage of the ARM 32-bit mode.
20499 @item set arm fpu @var{fputype}
20500 This command sets the ARM floating-point unit (FPU) type. The
20501 argument @var{fputype} can be one of these:
20505 Determine the FPU type by querying the OS ABI.
20507 Software FPU, with mixed-endian doubles on little-endian ARM
20510 GCC-compiled FPA co-processor.
20512 Software FPU with pure-endian doubles.
20518 Show the current type of the FPU.
20521 This command forces @value{GDBN} to use the specified ABI.
20524 Show the currently used ABI.
20526 @item set arm fallback-mode (arm|thumb|auto)
20527 @value{GDBN} uses the symbol table, when available, to determine
20528 whether instructions are ARM or Thumb. This command controls
20529 @value{GDBN}'s default behavior when the symbol table is not
20530 available. The default is @samp{auto}, which causes @value{GDBN} to
20531 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20534 @item show arm fallback-mode
20535 Show the current fallback instruction mode.
20537 @item set arm force-mode (arm|thumb|auto)
20538 This command overrides use of the symbol table to determine whether
20539 instructions are ARM or Thumb. The default is @samp{auto}, which
20540 causes @value{GDBN} to use the symbol table and then the setting
20541 of @samp{set arm fallback-mode}.
20543 @item show arm force-mode
20544 Show the current forced instruction mode.
20546 @item set debug arm
20547 Toggle whether to display ARM-specific debugging messages from the ARM
20548 target support subsystem.
20550 @item show debug arm
20551 Show whether ARM-specific debugging messages are enabled.
20554 The following commands are available when an ARM target is debugged
20555 using the RDI interface:
20558 @item rdilogfile @r{[}@var{file}@r{]}
20560 @cindex ADP (Angel Debugger Protocol) logging
20561 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20562 With an argument, sets the log file to the specified @var{file}. With
20563 no argument, show the current log file name. The default log file is
20566 @item rdilogenable @r{[}@var{arg}@r{]}
20567 @kindex rdilogenable
20568 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20569 enables logging, with an argument 0 or @code{"no"} disables it. With
20570 no arguments displays the current setting. When logging is enabled,
20571 ADP packets exchanged between @value{GDBN} and the RDI target device
20572 are logged to a file.
20574 @item set rdiromatzero
20575 @kindex set rdiromatzero
20576 @cindex ROM at zero address, RDI
20577 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20578 vector catching is disabled, so that zero address can be used. If off
20579 (the default), vector catching is enabled. For this command to take
20580 effect, it needs to be invoked prior to the @code{target rdi} command.
20582 @item show rdiromatzero
20583 @kindex show rdiromatzero
20584 Show the current setting of ROM at zero address.
20586 @item set rdiheartbeat
20587 @kindex set rdiheartbeat
20588 @cindex RDI heartbeat
20589 Enable or disable RDI heartbeat packets. It is not recommended to
20590 turn on this option, since it confuses ARM and EPI JTAG interface, as
20591 well as the Angel monitor.
20593 @item show rdiheartbeat
20594 @kindex show rdiheartbeat
20595 Show the setting of RDI heartbeat packets.
20599 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20600 The @value{GDBN} ARM simulator accepts the following optional arguments.
20603 @item --swi-support=@var{type}
20604 Tell the simulator which SWI interfaces to support.
20605 @var{type} may be a comma separated list of the following values.
20606 The default value is @code{all}.
20619 @subsection Renesas M32R/D and M32R/SDI
20622 @kindex target m32r
20623 @item target m32r @var{dev}
20624 Renesas M32R/D ROM monitor.
20626 @kindex target m32rsdi
20627 @item target m32rsdi @var{dev}
20628 Renesas M32R SDI server, connected via parallel port to the board.
20631 The following @value{GDBN} commands are specific to the M32R monitor:
20634 @item set download-path @var{path}
20635 @kindex set download-path
20636 @cindex find downloadable @sc{srec} files (M32R)
20637 Set the default path for finding downloadable @sc{srec} files.
20639 @item show download-path
20640 @kindex show download-path
20641 Show the default path for downloadable @sc{srec} files.
20643 @item set board-address @var{addr}
20644 @kindex set board-address
20645 @cindex M32-EVA target board address
20646 Set the IP address for the M32R-EVA target board.
20648 @item show board-address
20649 @kindex show board-address
20650 Show the current IP address of the target board.
20652 @item set server-address @var{addr}
20653 @kindex set server-address
20654 @cindex download server address (M32R)
20655 Set the IP address for the download server, which is the @value{GDBN}'s
20658 @item show server-address
20659 @kindex show server-address
20660 Display the IP address of the download server.
20662 @item upload @r{[}@var{file}@r{]}
20663 @kindex upload@r{, M32R}
20664 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20665 upload capability. If no @var{file} argument is given, the current
20666 executable file is uploaded.
20668 @item tload @r{[}@var{file}@r{]}
20669 @kindex tload@r{, M32R}
20670 Test the @code{upload} command.
20673 The following commands are available for M32R/SDI:
20678 @cindex reset SDI connection, M32R
20679 This command resets the SDI connection.
20683 This command shows the SDI connection status.
20686 @kindex debug_chaos
20687 @cindex M32R/Chaos debugging
20688 Instructs the remote that M32R/Chaos debugging is to be used.
20690 @item use_debug_dma
20691 @kindex use_debug_dma
20692 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20695 @kindex use_mon_code
20696 Instructs the remote to use the MON_CODE method of accessing memory.
20699 @kindex use_ib_break
20700 Instructs the remote to set breakpoints by IB break.
20702 @item use_dbt_break
20703 @kindex use_dbt_break
20704 Instructs the remote to set breakpoints by DBT.
20710 The Motorola m68k configuration includes ColdFire support, and a
20711 target command for the following ROM monitor.
20715 @kindex target dbug
20716 @item target dbug @var{dev}
20717 dBUG ROM monitor for Motorola ColdFire.
20722 @subsection MicroBlaze
20723 @cindex Xilinx MicroBlaze
20724 @cindex XMD, Xilinx Microprocessor Debugger
20726 The MicroBlaze is a soft-core processor supported on various Xilinx
20727 FPGAs, such as Spartan or Virtex series. Boards with these processors
20728 usually have JTAG ports which connect to a host system running the Xilinx
20729 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20730 This host system is used to download the configuration bitstream to
20731 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20732 communicates with the target board using the JTAG interface and
20733 presents a @code{gdbserver} interface to the board. By default
20734 @code{xmd} uses port @code{1234}. (While it is possible to change
20735 this default port, it requires the use of undocumented @code{xmd}
20736 commands. Contact Xilinx support if you need to do this.)
20738 Use these GDB commands to connect to the MicroBlaze target processor.
20741 @item target remote :1234
20742 Use this command to connect to the target if you are running @value{GDBN}
20743 on the same system as @code{xmd}.
20745 @item target remote @var{xmd-host}:1234
20746 Use this command to connect to the target if it is connected to @code{xmd}
20747 running on a different system named @var{xmd-host}.
20750 Use this command to download a program to the MicroBlaze target.
20752 @item set debug microblaze @var{n}
20753 Enable MicroBlaze-specific debugging messages if non-zero.
20755 @item show debug microblaze @var{n}
20756 Show MicroBlaze-specific debugging level.
20759 @node MIPS Embedded
20760 @subsection @acronym{MIPS} Embedded
20762 @cindex @acronym{MIPS} boards
20763 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20764 @acronym{MIPS} board attached to a serial line. This is available when
20765 you configure @value{GDBN} with @samp{--target=mips-elf}.
20768 Use these @value{GDBN} commands to specify the connection to your target board:
20771 @item target mips @var{port}
20772 @kindex target mips @var{port}
20773 To run a program on the board, start up @code{@value{GDBP}} with the
20774 name of your program as the argument. To connect to the board, use the
20775 command @samp{target mips @var{port}}, where @var{port} is the name of
20776 the serial port connected to the board. If the program has not already
20777 been downloaded to the board, you may use the @code{load} command to
20778 download it. You can then use all the usual @value{GDBN} commands.
20780 For example, this sequence connects to the target board through a serial
20781 port, and loads and runs a program called @var{prog} through the
20785 host$ @value{GDBP} @var{prog}
20786 @value{GDBN} is free software and @dots{}
20787 (@value{GDBP}) target mips /dev/ttyb
20788 (@value{GDBP}) load @var{prog}
20792 @item target mips @var{hostname}:@var{portnumber}
20793 On some @value{GDBN} host configurations, you can specify a TCP
20794 connection (for instance, to a serial line managed by a terminal
20795 concentrator) instead of a serial port, using the syntax
20796 @samp{@var{hostname}:@var{portnumber}}.
20798 @item target pmon @var{port}
20799 @kindex target pmon @var{port}
20802 @item target ddb @var{port}
20803 @kindex target ddb @var{port}
20804 NEC's DDB variant of PMON for Vr4300.
20806 @item target lsi @var{port}
20807 @kindex target lsi @var{port}
20808 LSI variant of PMON.
20810 @kindex target r3900
20811 @item target r3900 @var{dev}
20812 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20814 @kindex target array
20815 @item target array @var{dev}
20816 Array Tech LSI33K RAID controller board.
20822 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20825 @item set mipsfpu double
20826 @itemx set mipsfpu single
20827 @itemx set mipsfpu none
20828 @itemx set mipsfpu auto
20829 @itemx show mipsfpu
20830 @kindex set mipsfpu
20831 @kindex show mipsfpu
20832 @cindex @acronym{MIPS} remote floating point
20833 @cindex floating point, @acronym{MIPS} remote
20834 If your target board does not support the @acronym{MIPS} floating point
20835 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20836 need this, you may wish to put the command in your @value{GDBN} init
20837 file). This tells @value{GDBN} how to find the return value of
20838 functions which return floating point values. It also allows
20839 @value{GDBN} to avoid saving the floating point registers when calling
20840 functions on the board. If you are using a floating point coprocessor
20841 with only single precision floating point support, as on the @sc{r4650}
20842 processor, use the command @samp{set mipsfpu single}. The default
20843 double precision floating point coprocessor may be selected using
20844 @samp{set mipsfpu double}.
20846 In previous versions the only choices were double precision or no
20847 floating point, so @samp{set mipsfpu on} will select double precision
20848 and @samp{set mipsfpu off} will select no floating point.
20850 As usual, you can inquire about the @code{mipsfpu} variable with
20851 @samp{show mipsfpu}.
20853 @item set timeout @var{seconds}
20854 @itemx set retransmit-timeout @var{seconds}
20855 @itemx show timeout
20856 @itemx show retransmit-timeout
20857 @cindex @code{timeout}, @acronym{MIPS} protocol
20858 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20859 @kindex set timeout
20860 @kindex show timeout
20861 @kindex set retransmit-timeout
20862 @kindex show retransmit-timeout
20863 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20864 remote protocol, with the @code{set timeout @var{seconds}} command. The
20865 default is 5 seconds. Similarly, you can control the timeout used while
20866 waiting for an acknowledgment of a packet with the @code{set
20867 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20868 You can inspect both values with @code{show timeout} and @code{show
20869 retransmit-timeout}. (These commands are @emph{only} available when
20870 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20872 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20873 is waiting for your program to stop. In that case, @value{GDBN} waits
20874 forever because it has no way of knowing how long the program is going
20875 to run before stopping.
20877 @item set syn-garbage-limit @var{num}
20878 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20879 @cindex synchronize with remote @acronym{MIPS} target
20880 Limit the maximum number of characters @value{GDBN} should ignore when
20881 it tries to synchronize with the remote target. The default is 10
20882 characters. Setting the limit to -1 means there's no limit.
20884 @item show syn-garbage-limit
20885 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20886 Show the current limit on the number of characters to ignore when
20887 trying to synchronize with the remote system.
20889 @item set monitor-prompt @var{prompt}
20890 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20891 @cindex remote monitor prompt
20892 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20893 remote monitor. The default depends on the target:
20903 @item show monitor-prompt
20904 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20905 Show the current strings @value{GDBN} expects as the prompt from the
20908 @item set monitor-warnings
20909 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20910 Enable or disable monitor warnings about hardware breakpoints. This
20911 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20912 display warning messages whose codes are returned by the @code{lsi}
20913 PMON monitor for breakpoint commands.
20915 @item show monitor-warnings
20916 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20917 Show the current setting of printing monitor warnings.
20919 @item pmon @var{command}
20920 @kindex pmon@r{, @acronym{MIPS} remote}
20921 @cindex send PMON command
20922 This command allows sending an arbitrary @var{command} string to the
20923 monitor. The monitor must be in debug mode for this to work.
20926 @node PowerPC Embedded
20927 @subsection PowerPC Embedded
20929 @cindex DVC register
20930 @value{GDBN} supports using the DVC (Data Value Compare) register to
20931 implement in hardware simple hardware watchpoint conditions of the form:
20934 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20935 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20938 The DVC register will be automatically used when @value{GDBN} detects
20939 such pattern in a condition expression, and the created watchpoint uses one
20940 debug register (either the @code{exact-watchpoints} option is on and the
20941 variable is scalar, or the variable has a length of one byte). This feature
20942 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20945 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20946 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20947 in which case watchpoints using only one debug register are created when
20948 watching variables of scalar types.
20950 You can create an artificial array to watch an arbitrary memory
20951 region using one of the following commands (@pxref{Expressions}):
20954 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20955 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20958 PowerPC embedded processors support masked watchpoints. See the discussion
20959 about the @code{mask} argument in @ref{Set Watchpoints}.
20961 @cindex ranged breakpoint
20962 PowerPC embedded processors support hardware accelerated
20963 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20964 the inferior whenever it executes an instruction at any address within
20965 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20966 use the @code{break-range} command.
20968 @value{GDBN} provides the following PowerPC-specific commands:
20971 @kindex break-range
20972 @item break-range @var{start-location}, @var{end-location}
20973 Set a breakpoint for an address range.
20974 @var{start-location} and @var{end-location} can specify a function name,
20975 a line number, an offset of lines from the current line or from the start
20976 location, or an address of an instruction (see @ref{Specify Location},
20977 for a list of all the possible ways to specify a @var{location}.)
20978 The breakpoint will stop execution of the inferior whenever it
20979 executes an instruction at any address within the specified range,
20980 (including @var{start-location} and @var{end-location}.)
20982 @kindex set powerpc
20983 @item set powerpc soft-float
20984 @itemx show powerpc soft-float
20985 Force @value{GDBN} to use (or not use) a software floating point calling
20986 convention. By default, @value{GDBN} selects the calling convention based
20987 on the selected architecture and the provided executable file.
20989 @item set powerpc vector-abi
20990 @itemx show powerpc vector-abi
20991 Force @value{GDBN} to use the specified calling convention for vector
20992 arguments and return values. The valid options are @samp{auto};
20993 @samp{generic}, to avoid vector registers even if they are present;
20994 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20995 registers. By default, @value{GDBN} selects the calling convention
20996 based on the selected architecture and the provided executable file.
20998 @item set powerpc exact-watchpoints
20999 @itemx show powerpc exact-watchpoints
21000 Allow @value{GDBN} to use only one debug register when watching a variable
21001 of scalar type, thus assuming that the variable is accessed through the
21002 address of its first byte.
21004 @kindex target dink32
21005 @item target dink32 @var{dev}
21006 DINK32 ROM monitor.
21008 @kindex target ppcbug
21009 @item target ppcbug @var{dev}
21010 @kindex target ppcbug1
21011 @item target ppcbug1 @var{dev}
21012 PPCBUG ROM monitor for PowerPC.
21015 @item target sds @var{dev}
21016 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
21019 @cindex SDS protocol
21020 The following commands specific to the SDS protocol are supported
21024 @item set sdstimeout @var{nsec}
21025 @kindex set sdstimeout
21026 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
21027 default is 2 seconds.
21029 @item show sdstimeout
21030 @kindex show sdstimeout
21031 Show the current value of the SDS timeout.
21033 @item sds @var{command}
21034 @kindex sds@r{, a command}
21035 Send the specified @var{command} string to the SDS monitor.
21040 @subsection HP PA Embedded
21044 @kindex target op50n
21045 @item target op50n @var{dev}
21046 OP50N monitor, running on an OKI HPPA board.
21048 @kindex target w89k
21049 @item target w89k @var{dev}
21050 W89K monitor, running on a Winbond HPPA board.
21055 @subsection Tsqware Sparclet
21059 @value{GDBN} enables developers to debug tasks running on
21060 Sparclet targets from a Unix host.
21061 @value{GDBN} uses code that runs on
21062 both the Unix host and on the Sparclet target. The program
21063 @code{@value{GDBP}} is installed and executed on the Unix host.
21066 @item remotetimeout @var{args}
21067 @kindex remotetimeout
21068 @value{GDBN} supports the option @code{remotetimeout}.
21069 This option is set by the user, and @var{args} represents the number of
21070 seconds @value{GDBN} waits for responses.
21073 @cindex compiling, on Sparclet
21074 When compiling for debugging, include the options @samp{-g} to get debug
21075 information and @samp{-Ttext} to relocate the program to where you wish to
21076 load it on the target. You may also want to add the options @samp{-n} or
21077 @samp{-N} in order to reduce the size of the sections. Example:
21080 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
21083 You can use @code{objdump} to verify that the addresses are what you intended:
21086 sparclet-aout-objdump --headers --syms prog
21089 @cindex running, on Sparclet
21091 your Unix execution search path to find @value{GDBN}, you are ready to
21092 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
21093 (or @code{sparclet-aout-gdb}, depending on your installation).
21095 @value{GDBN} comes up showing the prompt:
21102 * Sparclet File:: Setting the file to debug
21103 * Sparclet Connection:: Connecting to Sparclet
21104 * Sparclet Download:: Sparclet download
21105 * Sparclet Execution:: Running and debugging
21108 @node Sparclet File
21109 @subsubsection Setting File to Debug
21111 The @value{GDBN} command @code{file} lets you choose with program to debug.
21114 (gdbslet) file prog
21118 @value{GDBN} then attempts to read the symbol table of @file{prog}.
21119 @value{GDBN} locates
21120 the file by searching the directories listed in the command search
21122 If the file was compiled with debug information (option @samp{-g}), source
21123 files will be searched as well.
21124 @value{GDBN} locates
21125 the source files by searching the directories listed in the directory search
21126 path (@pxref{Environment, ,Your Program's Environment}).
21128 to find a file, it displays a message such as:
21131 prog: No such file or directory.
21134 When this happens, add the appropriate directories to the search paths with
21135 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
21136 @code{target} command again.
21138 @node Sparclet Connection
21139 @subsubsection Connecting to Sparclet
21141 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
21142 To connect to a target on serial port ``@code{ttya}'', type:
21145 (gdbslet) target sparclet /dev/ttya
21146 Remote target sparclet connected to /dev/ttya
21147 main () at ../prog.c:3
21151 @value{GDBN} displays messages like these:
21157 @node Sparclet Download
21158 @subsubsection Sparclet Download
21160 @cindex download to Sparclet
21161 Once connected to the Sparclet target,
21162 you can use the @value{GDBN}
21163 @code{load} command to download the file from the host to the target.
21164 The file name and load offset should be given as arguments to the @code{load}
21166 Since the file format is aout, the program must be loaded to the starting
21167 address. You can use @code{objdump} to find out what this value is. The load
21168 offset is an offset which is added to the VMA (virtual memory address)
21169 of each of the file's sections.
21170 For instance, if the program
21171 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
21172 and bss at 0x12010170, in @value{GDBN}, type:
21175 (gdbslet) load prog 0x12010000
21176 Loading section .text, size 0xdb0 vma 0x12010000
21179 If the code is loaded at a different address then what the program was linked
21180 to, you may need to use the @code{section} and @code{add-symbol-file} commands
21181 to tell @value{GDBN} where to map the symbol table.
21183 @node Sparclet Execution
21184 @subsubsection Running and Debugging
21186 @cindex running and debugging Sparclet programs
21187 You can now begin debugging the task using @value{GDBN}'s execution control
21188 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
21189 manual for the list of commands.
21193 Breakpoint 1 at 0x12010000: file prog.c, line 3.
21195 Starting program: prog
21196 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
21197 3 char *symarg = 0;
21199 4 char *execarg = "hello!";
21204 @subsection Fujitsu Sparclite
21208 @kindex target sparclite
21209 @item target sparclite @var{dev}
21210 Fujitsu sparclite boards, used only for the purpose of loading.
21211 You must use an additional command to debug the program.
21212 For example: target remote @var{dev} using @value{GDBN} standard
21218 @subsection Zilog Z8000
21221 @cindex simulator, Z8000
21222 @cindex Zilog Z8000 simulator
21224 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
21227 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
21228 unsegmented variant of the Z8000 architecture) or the Z8001 (the
21229 segmented variant). The simulator recognizes which architecture is
21230 appropriate by inspecting the object code.
21233 @item target sim @var{args}
21235 @kindex target sim@r{, with Z8000}
21236 Debug programs on a simulated CPU. If the simulator supports setup
21237 options, specify them via @var{args}.
21241 After specifying this target, you can debug programs for the simulated
21242 CPU in the same style as programs for your host computer; use the
21243 @code{file} command to load a new program image, the @code{run} command
21244 to run your program, and so on.
21246 As well as making available all the usual machine registers
21247 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21248 additional items of information as specially named registers:
21253 Counts clock-ticks in the simulator.
21256 Counts instructions run in the simulator.
21259 Execution time in 60ths of a second.
21263 You can refer to these values in @value{GDBN} expressions with the usual
21264 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21265 conditional breakpoint that suspends only after at least 5000
21266 simulated clock ticks.
21269 @subsection Atmel AVR
21272 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21273 following AVR-specific commands:
21276 @item info io_registers
21277 @kindex info io_registers@r{, AVR}
21278 @cindex I/O registers (Atmel AVR)
21279 This command displays information about the AVR I/O registers. For
21280 each register, @value{GDBN} prints its number and value.
21287 When configured for debugging CRIS, @value{GDBN} provides the
21288 following CRIS-specific commands:
21291 @item set cris-version @var{ver}
21292 @cindex CRIS version
21293 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21294 The CRIS version affects register names and sizes. This command is useful in
21295 case autodetection of the CRIS version fails.
21297 @item show cris-version
21298 Show the current CRIS version.
21300 @item set cris-dwarf2-cfi
21301 @cindex DWARF-2 CFI and CRIS
21302 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21303 Change to @samp{off} when using @code{gcc-cris} whose version is below
21306 @item show cris-dwarf2-cfi
21307 Show the current state of using DWARF-2 CFI.
21309 @item set cris-mode @var{mode}
21311 Set the current CRIS mode to @var{mode}. It should only be changed when
21312 debugging in guru mode, in which case it should be set to
21313 @samp{guru} (the default is @samp{normal}).
21315 @item show cris-mode
21316 Show the current CRIS mode.
21320 @subsection Renesas Super-H
21323 For the Renesas Super-H processor, @value{GDBN} provides these
21327 @item set sh calling-convention @var{convention}
21328 @kindex set sh calling-convention
21329 Set the calling-convention used when calling functions from @value{GDBN}.
21330 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21331 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21332 convention. If the DWARF-2 information of the called function specifies
21333 that the function follows the Renesas calling convention, the function
21334 is called using the Renesas calling convention. If the calling convention
21335 is set to @samp{renesas}, the Renesas calling convention is always used,
21336 regardless of the DWARF-2 information. This can be used to override the
21337 default of @samp{gcc} if debug information is missing, or the compiler
21338 does not emit the DWARF-2 calling convention entry for a function.
21340 @item show sh calling-convention
21341 @kindex show sh calling-convention
21342 Show the current calling convention setting.
21347 @node Architectures
21348 @section Architectures
21350 This section describes characteristics of architectures that affect
21351 all uses of @value{GDBN} with the architecture, both native and cross.
21358 * HPPA:: HP PA architecture
21359 * SPU:: Cell Broadband Engine SPU architecture
21365 @subsection AArch64
21366 @cindex AArch64 support
21368 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21369 following special commands:
21372 @item set debug aarch64
21373 @kindex set debug aarch64
21374 This command determines whether AArch64 architecture-specific debugging
21375 messages are to be displayed.
21377 @item show debug aarch64
21378 Show whether AArch64 debugging messages are displayed.
21383 @subsection x86 Architecture-specific Issues
21386 @item set struct-convention @var{mode}
21387 @kindex set struct-convention
21388 @cindex struct return convention
21389 @cindex struct/union returned in registers
21390 Set the convention used by the inferior to return @code{struct}s and
21391 @code{union}s from functions to @var{mode}. Possible values of
21392 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21393 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21394 are returned on the stack, while @code{"reg"} means that a
21395 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21396 be returned in a register.
21398 @item show struct-convention
21399 @kindex show struct-convention
21400 Show the current setting of the convention to return @code{struct}s
21404 @subsubsection Intel(R) @dfn{Memory Protection Extensions} (MPX).
21405 @cindex Intel(R) Memory Protection Extensions (MPX).
21407 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
21408 @footnote{The register named with capital letters represent the architecture
21409 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
21410 which are the lower bound and upper bound. Bounds are effective addresses or
21411 memory locations. The upper bounds are architecturally represented in 1's
21412 complement form. A bound having lower bound = 0, and upper bound = 0
21413 (1's complement of all bits set) will allow access to the entire address space.
21415 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
21416 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
21417 display the upper bound performing the complement of one operation on the
21418 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
21419 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
21420 can also be noted that the upper bounds are inclusive.
21422 As an example, assume that the register BND0 holds bounds for a pointer having
21423 access allowed for the range between 0x32 and 0x71. The values present on
21424 bnd0raw and bnd registers are presented as follows:
21427 bnd0raw = @{0x32, 0xffffffff8e@}
21428 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
21431 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
21432 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
21433 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
21434 Python, the display includes the memory size, in bits, accessible to
21440 See the following section.
21443 @subsection @acronym{MIPS}
21445 @cindex stack on Alpha
21446 @cindex stack on @acronym{MIPS}
21447 @cindex Alpha stack
21448 @cindex @acronym{MIPS} stack
21449 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21450 sometimes requires @value{GDBN} to search backward in the object code to
21451 find the beginning of a function.
21453 @cindex response time, @acronym{MIPS} debugging
21454 To improve response time (especially for embedded applications, where
21455 @value{GDBN} may be restricted to a slow serial line for this search)
21456 you may want to limit the size of this search, using one of these
21460 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21461 @item set heuristic-fence-post @var{limit}
21462 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21463 search for the beginning of a function. A value of @var{0} (the
21464 default) means there is no limit. However, except for @var{0}, the
21465 larger the limit the more bytes @code{heuristic-fence-post} must search
21466 and therefore the longer it takes to run. You should only need to use
21467 this command when debugging a stripped executable.
21469 @item show heuristic-fence-post
21470 Display the current limit.
21474 These commands are available @emph{only} when @value{GDBN} is configured
21475 for debugging programs on Alpha or @acronym{MIPS} processors.
21477 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21481 @item set mips abi @var{arg}
21482 @kindex set mips abi
21483 @cindex set ABI for @acronym{MIPS}
21484 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21485 values of @var{arg} are:
21489 The default ABI associated with the current binary (this is the
21499 @item show mips abi
21500 @kindex show mips abi
21501 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21503 @item set mips compression @var{arg}
21504 @kindex set mips compression
21505 @cindex code compression, @acronym{MIPS}
21506 Tell @value{GDBN} which @acronym{MIPS} compressed
21507 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21508 inferior. @value{GDBN} uses this for code disassembly and other
21509 internal interpretation purposes. This setting is only referred to
21510 when no executable has been associated with the debugging session or
21511 the executable does not provide information about the encoding it uses.
21512 Otherwise this setting is automatically updated from information
21513 provided by the executable.
21515 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21516 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21517 executables containing @acronym{MIPS16} code frequently are not
21518 identified as such.
21520 This setting is ``sticky''; that is, it retains its value across
21521 debugging sessions until reset either explicitly with this command or
21522 implicitly from an executable.
21524 The compiler and/or assembler typically add symbol table annotations to
21525 identify functions compiled for the @acronym{MIPS16} or
21526 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21527 are present, @value{GDBN} uses them in preference to the global
21528 compressed @acronym{ISA} encoding setting.
21530 @item show mips compression
21531 @kindex show mips compression
21532 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21533 @value{GDBN} to debug the inferior.
21536 @itemx show mipsfpu
21537 @xref{MIPS Embedded, set mipsfpu}.
21539 @item set mips mask-address @var{arg}
21540 @kindex set mips mask-address
21541 @cindex @acronym{MIPS} addresses, masking
21542 This command determines whether the most-significant 32 bits of 64-bit
21543 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21544 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21545 setting, which lets @value{GDBN} determine the correct value.
21547 @item show mips mask-address
21548 @kindex show mips mask-address
21549 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21552 @item set remote-mips64-transfers-32bit-regs
21553 @kindex set remote-mips64-transfers-32bit-regs
21554 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21555 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21556 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21557 and 64 bits for other registers, set this option to @samp{on}.
21559 @item show remote-mips64-transfers-32bit-regs
21560 @kindex show remote-mips64-transfers-32bit-regs
21561 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21563 @item set debug mips
21564 @kindex set debug mips
21565 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21566 target code in @value{GDBN}.
21568 @item show debug mips
21569 @kindex show debug mips
21570 Show the current setting of @acronym{MIPS} debugging messages.
21576 @cindex HPPA support
21578 When @value{GDBN} is debugging the HP PA architecture, it provides the
21579 following special commands:
21582 @item set debug hppa
21583 @kindex set debug hppa
21584 This command determines whether HPPA architecture-specific debugging
21585 messages are to be displayed.
21587 @item show debug hppa
21588 Show whether HPPA debugging messages are displayed.
21590 @item maint print unwind @var{address}
21591 @kindex maint print unwind@r{, HPPA}
21592 This command displays the contents of the unwind table entry at the
21593 given @var{address}.
21599 @subsection Cell Broadband Engine SPU architecture
21600 @cindex Cell Broadband Engine
21603 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21604 it provides the following special commands:
21607 @item info spu event
21609 Display SPU event facility status. Shows current event mask
21610 and pending event status.
21612 @item info spu signal
21613 Display SPU signal notification facility status. Shows pending
21614 signal-control word and signal notification mode of both signal
21615 notification channels.
21617 @item info spu mailbox
21618 Display SPU mailbox facility status. Shows all pending entries,
21619 in order of processing, in each of the SPU Write Outbound,
21620 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21623 Display MFC DMA status. Shows all pending commands in the MFC
21624 DMA queue. For each entry, opcode, tag, class IDs, effective
21625 and local store addresses and transfer size are shown.
21627 @item info spu proxydma
21628 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21629 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21630 and local store addresses and transfer size are shown.
21634 When @value{GDBN} is debugging a combined PowerPC/SPU application
21635 on the Cell Broadband Engine, it provides in addition the following
21639 @item set spu stop-on-load @var{arg}
21641 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21642 will give control to the user when a new SPE thread enters its @code{main}
21643 function. The default is @code{off}.
21645 @item show spu stop-on-load
21647 Show whether to stop for new SPE threads.
21649 @item set spu auto-flush-cache @var{arg}
21650 Set whether to automatically flush the software-managed cache. When set to
21651 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21652 cache to be flushed whenever SPE execution stops. This provides a consistent
21653 view of PowerPC memory that is accessed via the cache. If an application
21654 does not use the software-managed cache, this option has no effect.
21656 @item show spu auto-flush-cache
21657 Show whether to automatically flush the software-managed cache.
21662 @subsection PowerPC
21663 @cindex PowerPC architecture
21665 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21666 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21667 numbers stored in the floating point registers. These values must be stored
21668 in two consecutive registers, always starting at an even register like
21669 @code{f0} or @code{f2}.
21671 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21672 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21673 @code{f2} and @code{f3} for @code{$dl1} and so on.
21675 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21676 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21679 @subsection Nios II
21680 @cindex Nios II architecture
21682 When @value{GDBN} is debugging the Nios II architecture,
21683 it provides the following special commands:
21687 @item set debug nios2
21688 @kindex set debug nios2
21689 This command turns on and off debugging messages for the Nios II
21690 target code in @value{GDBN}.
21692 @item show debug nios2
21693 @kindex show debug nios2
21694 Show the current setting of Nios II debugging messages.
21697 @node Controlling GDB
21698 @chapter Controlling @value{GDBN}
21700 You can alter the way @value{GDBN} interacts with you by using the
21701 @code{set} command. For commands controlling how @value{GDBN} displays
21702 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21707 * Editing:: Command editing
21708 * Command History:: Command history
21709 * Screen Size:: Screen size
21710 * Numbers:: Numbers
21711 * ABI:: Configuring the current ABI
21712 * Auto-loading:: Automatically loading associated files
21713 * Messages/Warnings:: Optional warnings and messages
21714 * Debugging Output:: Optional messages about internal happenings
21715 * Other Misc Settings:: Other Miscellaneous Settings
21723 @value{GDBN} indicates its readiness to read a command by printing a string
21724 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21725 can change the prompt string with the @code{set prompt} command. For
21726 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21727 the prompt in one of the @value{GDBN} sessions so that you can always tell
21728 which one you are talking to.
21730 @emph{Note:} @code{set prompt} does not add a space for you after the
21731 prompt you set. This allows you to set a prompt which ends in a space
21732 or a prompt that does not.
21736 @item set prompt @var{newprompt}
21737 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21739 @kindex show prompt
21741 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21744 Versions of @value{GDBN} that ship with Python scripting enabled have
21745 prompt extensions. The commands for interacting with these extensions
21749 @kindex set extended-prompt
21750 @item set extended-prompt @var{prompt}
21751 Set an extended prompt that allows for substitutions.
21752 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21753 substitution. Any escape sequences specified as part of the prompt
21754 string are replaced with the corresponding strings each time the prompt
21760 set extended-prompt Current working directory: \w (gdb)
21763 Note that when an extended-prompt is set, it takes control of the
21764 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21766 @kindex show extended-prompt
21767 @item show extended-prompt
21768 Prints the extended prompt. Any escape sequences specified as part of
21769 the prompt string with @code{set extended-prompt}, are replaced with the
21770 corresponding strings each time the prompt is displayed.
21774 @section Command Editing
21776 @cindex command line editing
21778 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21779 @sc{gnu} library provides consistent behavior for programs which provide a
21780 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21781 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21782 substitution, and a storage and recall of command history across
21783 debugging sessions.
21785 You may control the behavior of command line editing in @value{GDBN} with the
21786 command @code{set}.
21789 @kindex set editing
21792 @itemx set editing on
21793 Enable command line editing (enabled by default).
21795 @item set editing off
21796 Disable command line editing.
21798 @kindex show editing
21800 Show whether command line editing is enabled.
21803 @ifset SYSTEM_READLINE
21804 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21806 @ifclear SYSTEM_READLINE
21807 @xref{Command Line Editing},
21809 for more details about the Readline
21810 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21811 encouraged to read that chapter.
21813 @node Command History
21814 @section Command History
21815 @cindex command history
21817 @value{GDBN} can keep track of the commands you type during your
21818 debugging sessions, so that you can be certain of precisely what
21819 happened. Use these commands to manage the @value{GDBN} command
21822 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21823 package, to provide the history facility.
21824 @ifset SYSTEM_READLINE
21825 @xref{Using History Interactively, , , history, GNU History Library},
21827 @ifclear SYSTEM_READLINE
21828 @xref{Using History Interactively},
21830 for the detailed description of the History library.
21832 To issue a command to @value{GDBN} without affecting certain aspects of
21833 the state which is seen by users, prefix it with @samp{server }
21834 (@pxref{Server Prefix}). This
21835 means that this command will not affect the command history, nor will it
21836 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21837 pressed on a line by itself.
21839 @cindex @code{server}, command prefix
21840 The server prefix does not affect the recording of values into the value
21841 history; to print a value without recording it into the value history,
21842 use the @code{output} command instead of the @code{print} command.
21844 Here is the description of @value{GDBN} commands related to command
21848 @cindex history substitution
21849 @cindex history file
21850 @kindex set history filename
21851 @cindex @env{GDBHISTFILE}, environment variable
21852 @item set history filename @var{fname}
21853 Set the name of the @value{GDBN} command history file to @var{fname}.
21854 This is the file where @value{GDBN} reads an initial command history
21855 list, and where it writes the command history from this session when it
21856 exits. You can access this list through history expansion or through
21857 the history command editing characters listed below. This file defaults
21858 to the value of the environment variable @code{GDBHISTFILE}, or to
21859 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21862 @cindex save command history
21863 @kindex set history save
21864 @item set history save
21865 @itemx set history save on
21866 Record command history in a file, whose name may be specified with the
21867 @code{set history filename} command. By default, this option is disabled.
21869 @item set history save off
21870 Stop recording command history in a file.
21872 @cindex history size
21873 @kindex set history size
21874 @cindex @env{HISTSIZE}, environment variable
21875 @item set history size @var{size}
21876 @itemx set history size unlimited
21877 Set the number of commands which @value{GDBN} keeps in its history list.
21878 This defaults to the value of the environment variable
21879 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21880 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21881 history list is unlimited.
21884 History expansion assigns special meaning to the character @kbd{!}.
21885 @ifset SYSTEM_READLINE
21886 @xref{Event Designators, , , history, GNU History Library},
21888 @ifclear SYSTEM_READLINE
21889 @xref{Event Designators},
21893 @cindex history expansion, turn on/off
21894 Since @kbd{!} is also the logical not operator in C, history expansion
21895 is off by default. If you decide to enable history expansion with the
21896 @code{set history expansion on} command, you may sometimes need to
21897 follow @kbd{!} (when it is used as logical not, in an expression) with
21898 a space or a tab to prevent it from being expanded. The readline
21899 history facilities do not attempt substitution on the strings
21900 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21902 The commands to control history expansion are:
21905 @item set history expansion on
21906 @itemx set history expansion
21907 @kindex set history expansion
21908 Enable history expansion. History expansion is off by default.
21910 @item set history expansion off
21911 Disable history expansion.
21914 @kindex show history
21916 @itemx show history filename
21917 @itemx show history save
21918 @itemx show history size
21919 @itemx show history expansion
21920 These commands display the state of the @value{GDBN} history parameters.
21921 @code{show history} by itself displays all four states.
21926 @kindex show commands
21927 @cindex show last commands
21928 @cindex display command history
21929 @item show commands
21930 Display the last ten commands in the command history.
21932 @item show commands @var{n}
21933 Print ten commands centered on command number @var{n}.
21935 @item show commands +
21936 Print ten commands just after the commands last printed.
21940 @section Screen Size
21941 @cindex size of screen
21942 @cindex pauses in output
21944 Certain commands to @value{GDBN} may produce large amounts of
21945 information output to the screen. To help you read all of it,
21946 @value{GDBN} pauses and asks you for input at the end of each page of
21947 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21948 to discard the remaining output. Also, the screen width setting
21949 determines when to wrap lines of output. Depending on what is being
21950 printed, @value{GDBN} tries to break the line at a readable place,
21951 rather than simply letting it overflow onto the following line.
21953 Normally @value{GDBN} knows the size of the screen from the terminal
21954 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21955 together with the value of the @code{TERM} environment variable and the
21956 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21957 you can override it with the @code{set height} and @code{set
21964 @kindex show height
21965 @item set height @var{lpp}
21966 @itemx set height unlimited
21968 @itemx set width @var{cpl}
21969 @itemx set width unlimited
21971 These @code{set} commands specify a screen height of @var{lpp} lines and
21972 a screen width of @var{cpl} characters. The associated @code{show}
21973 commands display the current settings.
21975 If you specify a height of either @code{unlimited} or zero lines,
21976 @value{GDBN} does not pause during output no matter how long the
21977 output is. This is useful if output is to a file or to an editor
21980 Likewise, you can specify @samp{set width unlimited} or @samp{set
21981 width 0} to prevent @value{GDBN} from wrapping its output.
21983 @item set pagination on
21984 @itemx set pagination off
21985 @kindex set pagination
21986 Turn the output pagination on or off; the default is on. Turning
21987 pagination off is the alternative to @code{set height unlimited}. Note that
21988 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21989 Options, -batch}) also automatically disables pagination.
21991 @item show pagination
21992 @kindex show pagination
21993 Show the current pagination mode.
21998 @cindex number representation
21999 @cindex entering numbers
22001 You can always enter numbers in octal, decimal, or hexadecimal in
22002 @value{GDBN} by the usual conventions: octal numbers begin with
22003 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22004 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22005 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22006 10; likewise, the default display for numbers---when no particular
22007 format is specified---is base 10. You can change the default base for
22008 both input and output with the commands described below.
22011 @kindex set input-radix
22012 @item set input-radix @var{base}
22013 Set the default base for numeric input. Supported choices
22014 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22015 specified either unambiguously or using the current input radix; for
22019 set input-radix 012
22020 set input-radix 10.
22021 set input-radix 0xa
22025 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22026 leaves the input radix unchanged, no matter what it was, since
22027 @samp{10}, being without any leading or trailing signs of its base, is
22028 interpreted in the current radix. Thus, if the current radix is 16,
22029 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22032 @kindex set output-radix
22033 @item set output-radix @var{base}
22034 Set the default base for numeric display. Supported choices
22035 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
22036 specified either unambiguously or using the current input radix.
22038 @kindex show input-radix
22039 @item show input-radix
22040 Display the current default base for numeric input.
22042 @kindex show output-radix
22043 @item show output-radix
22044 Display the current default base for numeric display.
22046 @item set radix @r{[}@var{base}@r{]}
22050 These commands set and show the default base for both input and output
22051 of numbers. @code{set radix} sets the radix of input and output to
22052 the same base; without an argument, it resets the radix back to its
22053 default value of 10.
22058 @section Configuring the Current ABI
22060 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22061 application automatically. However, sometimes you need to override its
22062 conclusions. Use these commands to manage @value{GDBN}'s view of the
22068 @cindex Newlib OS ABI and its influence on the longjmp handling
22070 One @value{GDBN} configuration can debug binaries for multiple operating
22071 system targets, either via remote debugging or native emulation.
22072 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22073 but you can override its conclusion using the @code{set osabi} command.
22074 One example where this is useful is in debugging of binaries which use
22075 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22076 not have the same identifying marks that the standard C library for your
22079 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22080 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22081 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22082 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22086 Show the OS ABI currently in use.
22089 With no argument, show the list of registered available OS ABI's.
22091 @item set osabi @var{abi}
22092 Set the current OS ABI to @var{abi}.
22095 @cindex float promotion
22097 Generally, the way that an argument of type @code{float} is passed to a
22098 function depends on whether the function is prototyped. For a prototyped
22099 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22100 according to the architecture's convention for @code{float}. For unprototyped
22101 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22102 @code{double} and then passed.
22104 Unfortunately, some forms of debug information do not reliably indicate whether
22105 a function is prototyped. If @value{GDBN} calls a function that is not marked
22106 as prototyped, it consults @kbd{set coerce-float-to-double}.
22109 @kindex set coerce-float-to-double
22110 @item set coerce-float-to-double
22111 @itemx set coerce-float-to-double on
22112 Arguments of type @code{float} will be promoted to @code{double} when passed
22113 to an unprototyped function. This is the default setting.
22115 @item set coerce-float-to-double off
22116 Arguments of type @code{float} will be passed directly to unprototyped
22119 @kindex show coerce-float-to-double
22120 @item show coerce-float-to-double
22121 Show the current setting of promoting @code{float} to @code{double}.
22125 @kindex show cp-abi
22126 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22127 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22128 used to build your application. @value{GDBN} only fully supports
22129 programs with a single C@t{++} ABI; if your program contains code using
22130 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22131 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22132 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22133 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22134 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22135 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22140 Show the C@t{++} ABI currently in use.
22143 With no argument, show the list of supported C@t{++} ABI's.
22145 @item set cp-abi @var{abi}
22146 @itemx set cp-abi auto
22147 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22151 @section Automatically loading associated files
22152 @cindex auto-loading
22154 @value{GDBN} sometimes reads files with commands and settings automatically,
22155 without being explicitly told so by the user. We call this feature
22156 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22157 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22158 results or introduce security risks (e.g., if the file comes from untrusted
22162 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22163 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22165 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22166 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22169 There are various kinds of files @value{GDBN} can automatically load.
22170 In addition to these files, @value{GDBN} supports auto-loading code written
22171 in various extension languages. @xref{Auto-loading extensions}.
22173 Note that loading of these associated files (including the local @file{.gdbinit}
22174 file) requires accordingly configured @code{auto-load safe-path}
22175 (@pxref{Auto-loading safe path}).
22177 For these reasons, @value{GDBN} includes commands and options to let you
22178 control when to auto-load files and which files should be auto-loaded.
22181 @anchor{set auto-load off}
22182 @kindex set auto-load off
22183 @item set auto-load off
22184 Globally disable loading of all auto-loaded files.
22185 You may want to use this command with the @samp{-iex} option
22186 (@pxref{Option -init-eval-command}) such as:
22188 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
22191 Be aware that system init file (@pxref{System-wide configuration})
22192 and init files from your home directory (@pxref{Home Directory Init File})
22193 still get read (as they come from generally trusted directories).
22194 To prevent @value{GDBN} from auto-loading even those init files, use the
22195 @option{-nx} option (@pxref{Mode Options}), in addition to
22196 @code{set auto-load no}.
22198 @anchor{show auto-load}
22199 @kindex show auto-load
22200 @item show auto-load
22201 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
22205 (gdb) show auto-load
22206 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
22207 libthread-db: Auto-loading of inferior specific libthread_db is on.
22208 local-gdbinit: Auto-loading of .gdbinit script from current directory
22210 python-scripts: Auto-loading of Python scripts is on.
22211 safe-path: List of directories from which it is safe to auto-load files
22212 is $debugdir:$datadir/auto-load.
22213 scripts-directory: List of directories from which to load auto-loaded scripts
22214 is $debugdir:$datadir/auto-load.
22217 @anchor{info auto-load}
22218 @kindex info auto-load
22219 @item info auto-load
22220 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
22224 (gdb) info auto-load
22227 Yes /home/user/gdb/gdb-gdb.gdb
22228 libthread-db: No auto-loaded libthread-db.
22229 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
22233 Yes /home/user/gdb/gdb-gdb.py
22237 These are @value{GDBN} control commands for the auto-loading:
22239 @multitable @columnfractions .5 .5
22240 @item @xref{set auto-load off}.
22241 @tab Disable auto-loading globally.
22242 @item @xref{show auto-load}.
22243 @tab Show setting of all kinds of files.
22244 @item @xref{info auto-load}.
22245 @tab Show state of all kinds of files.
22246 @item @xref{set auto-load gdb-scripts}.
22247 @tab Control for @value{GDBN} command scripts.
22248 @item @xref{show auto-load gdb-scripts}.
22249 @tab Show setting of @value{GDBN} command scripts.
22250 @item @xref{info auto-load gdb-scripts}.
22251 @tab Show state of @value{GDBN} command scripts.
22252 @item @xref{set auto-load python-scripts}.
22253 @tab Control for @value{GDBN} Python scripts.
22254 @item @xref{show auto-load python-scripts}.
22255 @tab Show setting of @value{GDBN} Python scripts.
22256 @item @xref{info auto-load python-scripts}.
22257 @tab Show state of @value{GDBN} Python scripts.
22258 @item @xref{set auto-load scripts-directory}.
22259 @tab Control for @value{GDBN} auto-loaded scripts location.
22260 @item @xref{show auto-load scripts-directory}.
22261 @tab Show @value{GDBN} auto-loaded scripts location.
22262 @item @xref{set auto-load local-gdbinit}.
22263 @tab Control for init file in the current directory.
22264 @item @xref{show auto-load local-gdbinit}.
22265 @tab Show setting of init file in the current directory.
22266 @item @xref{info auto-load local-gdbinit}.
22267 @tab Show state of init file in the current directory.
22268 @item @xref{set auto-load libthread-db}.
22269 @tab Control for thread debugging library.
22270 @item @xref{show auto-load libthread-db}.
22271 @tab Show setting of thread debugging library.
22272 @item @xref{info auto-load libthread-db}.
22273 @tab Show state of thread debugging library.
22274 @item @xref{set auto-load safe-path}.
22275 @tab Control directories trusted for automatic loading.
22276 @item @xref{show auto-load safe-path}.
22277 @tab Show directories trusted for automatic loading.
22278 @item @xref{add-auto-load-safe-path}.
22279 @tab Add directory trusted for automatic loading.
22282 @node Init File in the Current Directory
22283 @subsection Automatically loading init file in the current directory
22284 @cindex auto-loading init file in the current directory
22286 By default, @value{GDBN} reads and executes the canned sequences of commands
22287 from init file (if any) in the current working directory,
22288 see @ref{Init File in the Current Directory during Startup}.
22290 Note that loading of this local @file{.gdbinit} file also requires accordingly
22291 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22294 @anchor{set auto-load local-gdbinit}
22295 @kindex set auto-load local-gdbinit
22296 @item set auto-load local-gdbinit [on|off]
22297 Enable or disable the auto-loading of canned sequences of commands
22298 (@pxref{Sequences}) found in init file in the current directory.
22300 @anchor{show auto-load local-gdbinit}
22301 @kindex show auto-load local-gdbinit
22302 @item show auto-load local-gdbinit
22303 Show whether auto-loading of canned sequences of commands from init file in the
22304 current directory is enabled or disabled.
22306 @anchor{info auto-load local-gdbinit}
22307 @kindex info auto-load local-gdbinit
22308 @item info auto-load local-gdbinit
22309 Print whether canned sequences of commands from init file in the
22310 current directory have been auto-loaded.
22313 @node libthread_db.so.1 file
22314 @subsection Automatically loading thread debugging library
22315 @cindex auto-loading libthread_db.so.1
22317 This feature is currently present only on @sc{gnu}/Linux native hosts.
22319 @value{GDBN} reads in some cases thread debugging library from places specific
22320 to the inferior (@pxref{set libthread-db-search-path}).
22322 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22323 without checking this @samp{set auto-load libthread-db} switch as system
22324 libraries have to be trusted in general. In all other cases of
22325 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22326 auto-load libthread-db} is enabled before trying to open such thread debugging
22329 Note that loading of this debugging library also requires accordingly configured
22330 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22333 @anchor{set auto-load libthread-db}
22334 @kindex set auto-load libthread-db
22335 @item set auto-load libthread-db [on|off]
22336 Enable or disable the auto-loading of inferior specific thread debugging library.
22338 @anchor{show auto-load libthread-db}
22339 @kindex show auto-load libthread-db
22340 @item show auto-load libthread-db
22341 Show whether auto-loading of inferior specific thread debugging library is
22342 enabled or disabled.
22344 @anchor{info auto-load libthread-db}
22345 @kindex info auto-load libthread-db
22346 @item info auto-load libthread-db
22347 Print the list of all loaded inferior specific thread debugging libraries and
22348 for each such library print list of inferior @var{pid}s using it.
22351 @node Auto-loading safe path
22352 @subsection Security restriction for auto-loading
22353 @cindex auto-loading safe-path
22355 As the files of inferior can come from untrusted source (such as submitted by
22356 an application user) @value{GDBN} does not always load any files automatically.
22357 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22358 directories trusted for loading files not explicitly requested by user.
22359 Each directory can also be a shell wildcard pattern.
22361 If the path is not set properly you will see a warning and the file will not
22366 Reading symbols from /home/user/gdb/gdb...done.
22367 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22368 declined by your `auto-load safe-path' set
22369 to "$debugdir:$datadir/auto-load".
22370 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22371 declined by your `auto-load safe-path' set
22372 to "$debugdir:$datadir/auto-load".
22376 To instruct @value{GDBN} to go ahead and use the init files anyway,
22377 invoke @value{GDBN} like this:
22380 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22383 The list of trusted directories is controlled by the following commands:
22386 @anchor{set auto-load safe-path}
22387 @kindex set auto-load safe-path
22388 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22389 Set the list of directories (and their subdirectories) trusted for automatic
22390 loading and execution of scripts. You can also enter a specific trusted file.
22391 Each directory can also be a shell wildcard pattern; wildcards do not match
22392 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22393 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22394 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22395 its default value as specified during @value{GDBN} compilation.
22397 The list of directories uses path separator (@samp{:} on GNU and Unix
22398 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22399 to the @env{PATH} environment variable.
22401 @anchor{show auto-load safe-path}
22402 @kindex show auto-load safe-path
22403 @item show auto-load safe-path
22404 Show the list of directories trusted for automatic loading and execution of
22407 @anchor{add-auto-load-safe-path}
22408 @kindex add-auto-load-safe-path
22409 @item add-auto-load-safe-path
22410 Add an entry (or list of entries) the list of directories trusted for automatic
22411 loading and execution of scripts. Multiple entries may be delimited by the
22412 host platform path separator in use.
22415 This variable defaults to what @code{--with-auto-load-dir} has been configured
22416 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22417 substitution applies the same as for @ref{set auto-load scripts-directory}.
22418 The default @code{set auto-load safe-path} value can be also overriden by
22419 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22421 Setting this variable to @file{/} disables this security protection,
22422 corresponding @value{GDBN} configuration option is
22423 @option{--without-auto-load-safe-path}.
22424 This variable is supposed to be set to the system directories writable by the
22425 system superuser only. Users can add their source directories in init files in
22426 their home directories (@pxref{Home Directory Init File}). See also deprecated
22427 init file in the current directory
22428 (@pxref{Init File in the Current Directory during Startup}).
22430 To force @value{GDBN} to load the files it declined to load in the previous
22431 example, you could use one of the following ways:
22434 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22435 Specify this trusted directory (or a file) as additional component of the list.
22436 You have to specify also any existing directories displayed by
22437 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22439 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22440 Specify this directory as in the previous case but just for a single
22441 @value{GDBN} session.
22443 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22444 Disable auto-loading safety for a single @value{GDBN} session.
22445 This assumes all the files you debug during this @value{GDBN} session will come
22446 from trusted sources.
22448 @item @kbd{./configure --without-auto-load-safe-path}
22449 During compilation of @value{GDBN} you may disable any auto-loading safety.
22450 This assumes all the files you will ever debug with this @value{GDBN} come from
22454 On the other hand you can also explicitly forbid automatic files loading which
22455 also suppresses any such warning messages:
22458 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22459 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22461 @item @file{~/.gdbinit}: @samp{set auto-load no}
22462 Disable auto-loading globally for the user
22463 (@pxref{Home Directory Init File}). While it is improbable, you could also
22464 use system init file instead (@pxref{System-wide configuration}).
22467 This setting applies to the file names as entered by user. If no entry matches
22468 @value{GDBN} tries as a last resort to also resolve all the file names into
22469 their canonical form (typically resolving symbolic links) and compare the
22470 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22471 own before starting the comparison so a canonical form of directories is
22472 recommended to be entered.
22474 @node Auto-loading verbose mode
22475 @subsection Displaying files tried for auto-load
22476 @cindex auto-loading verbose mode
22478 For better visibility of all the file locations where you can place scripts to
22479 be auto-loaded with inferior --- or to protect yourself against accidental
22480 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22481 all the files attempted to be loaded. Both existing and non-existing files may
22484 For example the list of directories from which it is safe to auto-load files
22485 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22486 may not be too obvious while setting it up.
22489 (gdb) set debug auto-load on
22490 (gdb) file ~/src/t/true
22491 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22492 for objfile "/tmp/true".
22493 auto-load: Updating directories of "/usr:/opt".
22494 auto-load: Using directory "/usr".
22495 auto-load: Using directory "/opt".
22496 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22497 by your `auto-load safe-path' set to "/usr:/opt".
22501 @anchor{set debug auto-load}
22502 @kindex set debug auto-load
22503 @item set debug auto-load [on|off]
22504 Set whether to print the filenames attempted to be auto-loaded.
22506 @anchor{show debug auto-load}
22507 @kindex show debug auto-load
22508 @item show debug auto-load
22509 Show whether printing of the filenames attempted to be auto-loaded is turned
22513 @node Messages/Warnings
22514 @section Optional Warnings and Messages
22516 @cindex verbose operation
22517 @cindex optional warnings
22518 By default, @value{GDBN} is silent about its inner workings. If you are
22519 running on a slow machine, you may want to use the @code{set verbose}
22520 command. This makes @value{GDBN} tell you when it does a lengthy
22521 internal operation, so you will not think it has crashed.
22523 Currently, the messages controlled by @code{set verbose} are those
22524 which announce that the symbol table for a source file is being read;
22525 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22528 @kindex set verbose
22529 @item set verbose on
22530 Enables @value{GDBN} output of certain informational messages.
22532 @item set verbose off
22533 Disables @value{GDBN} output of certain informational messages.
22535 @kindex show verbose
22537 Displays whether @code{set verbose} is on or off.
22540 By default, if @value{GDBN} encounters bugs in the symbol table of an
22541 object file, it is silent; but if you are debugging a compiler, you may
22542 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22547 @kindex set complaints
22548 @item set complaints @var{limit}
22549 Permits @value{GDBN} to output @var{limit} complaints about each type of
22550 unusual symbols before becoming silent about the problem. Set
22551 @var{limit} to zero to suppress all complaints; set it to a large number
22552 to prevent complaints from being suppressed.
22554 @kindex show complaints
22555 @item show complaints
22556 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22560 @anchor{confirmation requests}
22561 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22562 lot of stupid questions to confirm certain commands. For example, if
22563 you try to run a program which is already running:
22567 The program being debugged has been started already.
22568 Start it from the beginning? (y or n)
22571 If you are willing to unflinchingly face the consequences of your own
22572 commands, you can disable this ``feature'':
22576 @kindex set confirm
22578 @cindex confirmation
22579 @cindex stupid questions
22580 @item set confirm off
22581 Disables confirmation requests. Note that running @value{GDBN} with
22582 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22583 automatically disables confirmation requests.
22585 @item set confirm on
22586 Enables confirmation requests (the default).
22588 @kindex show confirm
22590 Displays state of confirmation requests.
22594 @cindex command tracing
22595 If you need to debug user-defined commands or sourced files you may find it
22596 useful to enable @dfn{command tracing}. In this mode each command will be
22597 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22598 quantity denoting the call depth of each command.
22601 @kindex set trace-commands
22602 @cindex command scripts, debugging
22603 @item set trace-commands on
22604 Enable command tracing.
22605 @item set trace-commands off
22606 Disable command tracing.
22607 @item show trace-commands
22608 Display the current state of command tracing.
22611 @node Debugging Output
22612 @section Optional Messages about Internal Happenings
22613 @cindex optional debugging messages
22615 @value{GDBN} has commands that enable optional debugging messages from
22616 various @value{GDBN} subsystems; normally these commands are of
22617 interest to @value{GDBN} maintainers, or when reporting a bug. This
22618 section documents those commands.
22621 @kindex set exec-done-display
22622 @item set exec-done-display
22623 Turns on or off the notification of asynchronous commands'
22624 completion. When on, @value{GDBN} will print a message when an
22625 asynchronous command finishes its execution. The default is off.
22626 @kindex show exec-done-display
22627 @item show exec-done-display
22628 Displays the current setting of asynchronous command completion
22631 @cindex ARM AArch64
22632 @item set debug aarch64
22633 Turns on or off display of debugging messages related to ARM AArch64.
22634 The default is off.
22636 @item show debug aarch64
22637 Displays the current state of displaying debugging messages related to
22639 @cindex gdbarch debugging info
22640 @cindex architecture debugging info
22641 @item set debug arch
22642 Turns on or off display of gdbarch debugging info. The default is off
22643 @item show debug arch
22644 Displays the current state of displaying gdbarch debugging info.
22645 @item set debug aix-solib
22646 @cindex AIX shared library debugging
22647 Control display of debugging messages from the AIX shared library
22648 support module. The default is off.
22649 @item show debug aix-thread
22650 Show the current state of displaying AIX shared library debugging messages.
22651 @item set debug aix-thread
22652 @cindex AIX threads
22653 Display debugging messages about inner workings of the AIX thread
22655 @item show debug aix-thread
22656 Show the current state of AIX thread debugging info display.
22657 @item set debug check-physname
22659 Check the results of the ``physname'' computation. When reading DWARF
22660 debugging information for C@t{++}, @value{GDBN} attempts to compute
22661 each entity's name. @value{GDBN} can do this computation in two
22662 different ways, depending on exactly what information is present.
22663 When enabled, this setting causes @value{GDBN} to compute the names
22664 both ways and display any discrepancies.
22665 @item show debug check-physname
22666 Show the current state of ``physname'' checking.
22667 @item set debug coff-pe-read
22668 @cindex COFF/PE exported symbols
22669 Control display of debugging messages related to reading of COFF/PE
22670 exported symbols. The default is off.
22671 @item show debug coff-pe-read
22672 Displays the current state of displaying debugging messages related to
22673 reading of COFF/PE exported symbols.
22674 @item set debug dwarf2-die
22675 @cindex DWARF2 DIEs
22676 Dump DWARF2 DIEs after they are read in.
22677 The value is the number of nesting levels to print.
22678 A value of zero turns off the display.
22679 @item show debug dwarf2-die
22680 Show the current state of DWARF2 DIE debugging.
22681 @item set debug dwarf2-read
22682 @cindex DWARF2 Reading
22683 Turns on or off display of debugging messages related to reading
22684 DWARF debug info. The default is 0 (off).
22685 A value of 1 provides basic information.
22686 A value greater than 1 provides more verbose information.
22687 @item show debug dwarf2-read
22688 Show the current state of DWARF2 reader debugging.
22689 @item set debug displaced
22690 @cindex displaced stepping debugging info
22691 Turns on or off display of @value{GDBN} debugging info for the
22692 displaced stepping support. The default is off.
22693 @item show debug displaced
22694 Displays the current state of displaying @value{GDBN} debugging info
22695 related to displaced stepping.
22696 @item set debug event
22697 @cindex event debugging info
22698 Turns on or off display of @value{GDBN} event debugging info. The
22700 @item show debug event
22701 Displays the current state of displaying @value{GDBN} event debugging
22703 @item set debug expression
22704 @cindex expression debugging info
22705 Turns on or off display of debugging info about @value{GDBN}
22706 expression parsing. The default is off.
22707 @item show debug expression
22708 Displays the current state of displaying debugging info about
22709 @value{GDBN} expression parsing.
22710 @item set debug frame
22711 @cindex frame debugging info
22712 Turns on or off display of @value{GDBN} frame debugging info. The
22714 @item show debug frame
22715 Displays the current state of displaying @value{GDBN} frame debugging
22717 @item set debug gnu-nat
22718 @cindex @sc{gnu}/Hurd debug messages
22719 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22720 @item show debug gnu-nat
22721 Show the current state of @sc{gnu}/Hurd debugging messages.
22722 @item set debug infrun
22723 @cindex inferior debugging info
22724 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22725 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22726 for implementing operations such as single-stepping the inferior.
22727 @item show debug infrun
22728 Displays the current state of @value{GDBN} inferior debugging.
22729 @item set debug jit
22730 @cindex just-in-time compilation, debugging messages
22731 Turns on or off debugging messages from JIT debug support.
22732 @item show debug jit
22733 Displays the current state of @value{GDBN} JIT debugging.
22734 @item set debug lin-lwp
22735 @cindex @sc{gnu}/Linux LWP debug messages
22736 @cindex Linux lightweight processes
22737 Turns on or off debugging messages from the Linux LWP debug support.
22738 @item show debug lin-lwp
22739 Show the current state of Linux LWP debugging messages.
22740 @item set debug mach-o
22741 @cindex Mach-O symbols processing
22742 Control display of debugging messages related to Mach-O symbols
22743 processing. The default is off.
22744 @item show debug mach-o
22745 Displays the current state of displaying debugging messages related to
22746 reading of COFF/PE exported symbols.
22747 @item set debug notification
22748 @cindex remote async notification debugging info
22749 Turns on or off debugging messages about remote async notification.
22750 The default is off.
22751 @item show debug notification
22752 Displays the current state of remote async notification debugging messages.
22753 @item set debug observer
22754 @cindex observer debugging info
22755 Turns on or off display of @value{GDBN} observer debugging. This
22756 includes info such as the notification of observable events.
22757 @item show debug observer
22758 Displays the current state of observer debugging.
22759 @item set debug overload
22760 @cindex C@t{++} overload debugging info
22761 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22762 info. This includes info such as ranking of functions, etc. The default
22764 @item show debug overload
22765 Displays the current state of displaying @value{GDBN} C@t{++} overload
22767 @cindex expression parser, debugging info
22768 @cindex debug expression parser
22769 @item set debug parser
22770 Turns on or off the display of expression parser debugging output.
22771 Internally, this sets the @code{yydebug} variable in the expression
22772 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22773 details. The default is off.
22774 @item show debug parser
22775 Show the current state of expression parser debugging.
22776 @cindex packets, reporting on stdout
22777 @cindex serial connections, debugging
22778 @cindex debug remote protocol
22779 @cindex remote protocol debugging
22780 @cindex display remote packets
22781 @item set debug remote
22782 Turns on or off display of reports on all packets sent back and forth across
22783 the serial line to the remote machine. The info is printed on the
22784 @value{GDBN} standard output stream. The default is off.
22785 @item show debug remote
22786 Displays the state of display of remote packets.
22787 @item set debug serial
22788 Turns on or off display of @value{GDBN} serial debugging info. The
22790 @item show debug serial
22791 Displays the current state of displaying @value{GDBN} serial debugging
22793 @item set debug solib-frv
22794 @cindex FR-V shared-library debugging
22795 Turns on or off debugging messages for FR-V shared-library code.
22796 @item show debug solib-frv
22797 Display the current state of FR-V shared-library code debugging
22799 @item set debug symfile
22800 @cindex symbol file functions
22801 Turns on or off display of debugging messages related to symbol file functions.
22802 The default is off. @xref{Files}.
22803 @item show debug symfile
22804 Show the current state of symbol file debugging messages.
22805 @item set debug symtab-create
22806 @cindex symbol table creation
22807 Turns on or off display of debugging messages related to symbol table creation.
22808 The default is 0 (off).
22809 A value of 1 provides basic information.
22810 A value greater than 1 provides more verbose information.
22811 @item show debug symtab-create
22812 Show the current state of symbol table creation debugging.
22813 @item set debug target
22814 @cindex target debugging info
22815 Turns on or off display of @value{GDBN} target debugging info. This info
22816 includes what is going on at the target level of GDB, as it happens. The
22817 default is 0. Set it to 1 to track events, and to 2 to also track the
22818 value of large memory transfers. Changes to this flag do not take effect
22819 until the next time you connect to a target or use the @code{run} command.
22820 @item show debug target
22821 Displays the current state of displaying @value{GDBN} target debugging
22823 @item set debug timestamp
22824 @cindex timestampping debugging info
22825 Turns on or off display of timestamps with @value{GDBN} debugging info.
22826 When enabled, seconds and microseconds are displayed before each debugging
22828 @item show debug timestamp
22829 Displays the current state of displaying timestamps with @value{GDBN}
22831 @item set debugvarobj
22832 @cindex variable object debugging info
22833 Turns on or off display of @value{GDBN} variable object debugging
22834 info. The default is off.
22835 @item show debugvarobj
22836 Displays the current state of displaying @value{GDBN} variable object
22838 @item set debug xml
22839 @cindex XML parser debugging
22840 Turns on or off debugging messages for built-in XML parsers.
22841 @item show debug xml
22842 Displays the current state of XML debugging messages.
22845 @node Other Misc Settings
22846 @section Other Miscellaneous Settings
22847 @cindex miscellaneous settings
22850 @kindex set interactive-mode
22851 @item set interactive-mode
22852 If @code{on}, forces @value{GDBN} to assume that GDB was started
22853 in a terminal. In practice, this means that @value{GDBN} should wait
22854 for the user to answer queries generated by commands entered at
22855 the command prompt. If @code{off}, forces @value{GDBN} to operate
22856 in the opposite mode, and it uses the default answers to all queries.
22857 If @code{auto} (the default), @value{GDBN} tries to determine whether
22858 its standard input is a terminal, and works in interactive-mode if it
22859 is, non-interactively otherwise.
22861 In the vast majority of cases, the debugger should be able to guess
22862 correctly which mode should be used. But this setting can be useful
22863 in certain specific cases, such as running a MinGW @value{GDBN}
22864 inside a cygwin window.
22866 @kindex show interactive-mode
22867 @item show interactive-mode
22868 Displays whether the debugger is operating in interactive mode or not.
22871 @node Extending GDB
22872 @chapter Extending @value{GDBN}
22873 @cindex extending GDB
22875 @value{GDBN} provides several mechanisms for extension.
22876 @value{GDBN} also provides the ability to automatically load
22877 extensions when it reads a file for debugging. This allows the
22878 user to automatically customize @value{GDBN} for the program
22882 * Sequences:: Canned Sequences of @value{GDBN} Commands
22883 * Python:: Extending @value{GDBN} using Python
22884 * Auto-loading extensions:: Automatically loading extensions
22885 * Aliases:: Creating new spellings of existing commands
22888 To facilitate the use of extension languages, @value{GDBN} is capable
22889 of evaluating the contents of a file. When doing so, @value{GDBN}
22890 can recognize which extension language is being used by looking at
22891 the filename extension. Files with an unrecognized filename extension
22892 are always treated as a @value{GDBN} Command Files.
22893 @xref{Command Files,, Command files}.
22895 You can control how @value{GDBN} evaluates these files with the following
22899 @kindex set script-extension
22900 @kindex show script-extension
22901 @item set script-extension off
22902 All scripts are always evaluated as @value{GDBN} Command Files.
22904 @item set script-extension soft
22905 The debugger determines the scripting language based on filename
22906 extension. If this scripting language is supported, @value{GDBN}
22907 evaluates the script using that language. Otherwise, it evaluates
22908 the file as a @value{GDBN} Command File.
22910 @item set script-extension strict
22911 The debugger determines the scripting language based on filename
22912 extension, and evaluates the script using that language. If the
22913 language is not supported, then the evaluation fails.
22915 @item show script-extension
22916 Display the current value of the @code{script-extension} option.
22921 @section Canned Sequences of Commands
22923 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22924 Command Lists}), @value{GDBN} provides two ways to store sequences of
22925 commands for execution as a unit: user-defined commands and command
22929 * Define:: How to define your own commands
22930 * Hooks:: Hooks for user-defined commands
22931 * Command Files:: How to write scripts of commands to be stored in a file
22932 * Output:: Commands for controlled output
22933 * Auto-loading sequences:: Controlling auto-loaded command files
22937 @subsection User-defined Commands
22939 @cindex user-defined command
22940 @cindex arguments, to user-defined commands
22941 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22942 which you assign a new name as a command. This is done with the
22943 @code{define} command. User commands may accept up to 10 arguments
22944 separated by whitespace. Arguments are accessed within the user command
22945 via @code{$arg0@dots{}$arg9}. A trivial example:
22949 print $arg0 + $arg1 + $arg2
22954 To execute the command use:
22961 This defines the command @code{adder}, which prints the sum of
22962 its three arguments. Note the arguments are text substitutions, so they may
22963 reference variables, use complex expressions, or even perform inferior
22966 @cindex argument count in user-defined commands
22967 @cindex how many arguments (user-defined commands)
22968 In addition, @code{$argc} may be used to find out how many arguments have
22969 been passed. This expands to a number in the range 0@dots{}10.
22974 print $arg0 + $arg1
22977 print $arg0 + $arg1 + $arg2
22985 @item define @var{commandname}
22986 Define a command named @var{commandname}. If there is already a command
22987 by that name, you are asked to confirm that you want to redefine it.
22988 @var{commandname} may be a bare command name consisting of letters,
22989 numbers, dashes, and underscores. It may also start with any predefined
22990 prefix command. For example, @samp{define target my-target} creates
22991 a user-defined @samp{target my-target} command.
22993 The definition of the command is made up of other @value{GDBN} command lines,
22994 which are given following the @code{define} command. The end of these
22995 commands is marked by a line containing @code{end}.
22998 @kindex end@r{ (user-defined commands)}
22999 @item document @var{commandname}
23000 Document the user-defined command @var{commandname}, so that it can be
23001 accessed by @code{help}. The command @var{commandname} must already be
23002 defined. This command reads lines of documentation just as @code{define}
23003 reads the lines of the command definition, ending with @code{end}.
23004 After the @code{document} command is finished, @code{help} on command
23005 @var{commandname} displays the documentation you have written.
23007 You may use the @code{document} command again to change the
23008 documentation of a command. Redefining the command with @code{define}
23009 does not change the documentation.
23011 @kindex dont-repeat
23012 @cindex don't repeat command
23014 Used inside a user-defined command, this tells @value{GDBN} that this
23015 command should not be repeated when the user hits @key{RET}
23016 (@pxref{Command Syntax, repeat last command}).
23018 @kindex help user-defined
23019 @item help user-defined
23020 List all user-defined commands and all python commands defined in class
23021 COMAND_USER. The first line of the documentation or docstring is
23026 @itemx show user @var{commandname}
23027 Display the @value{GDBN} commands used to define @var{commandname} (but
23028 not its documentation). If no @var{commandname} is given, display the
23029 definitions for all user-defined commands.
23030 This does not work for user-defined python commands.
23032 @cindex infinite recursion in user-defined commands
23033 @kindex show max-user-call-depth
23034 @kindex set max-user-call-depth
23035 @item show max-user-call-depth
23036 @itemx set max-user-call-depth
23037 The value of @code{max-user-call-depth} controls how many recursion
23038 levels are allowed in user-defined commands before @value{GDBN} suspects an
23039 infinite recursion and aborts the command.
23040 This does not apply to user-defined python commands.
23043 In addition to the above commands, user-defined commands frequently
23044 use control flow commands, described in @ref{Command Files}.
23046 When user-defined commands are executed, the
23047 commands of the definition are not printed. An error in any command
23048 stops execution of the user-defined command.
23050 If used interactively, commands that would ask for confirmation proceed
23051 without asking when used inside a user-defined command. Many @value{GDBN}
23052 commands that normally print messages to say what they are doing omit the
23053 messages when used in a user-defined command.
23056 @subsection User-defined Command Hooks
23057 @cindex command hooks
23058 @cindex hooks, for commands
23059 @cindex hooks, pre-command
23062 You may define @dfn{hooks}, which are a special kind of user-defined
23063 command. Whenever you run the command @samp{foo}, if the user-defined
23064 command @samp{hook-foo} exists, it is executed (with no arguments)
23065 before that command.
23067 @cindex hooks, post-command
23069 A hook may also be defined which is run after the command you executed.
23070 Whenever you run the command @samp{foo}, if the user-defined command
23071 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23072 that command. Post-execution hooks may exist simultaneously with
23073 pre-execution hooks, for the same command.
23075 It is valid for a hook to call the command which it hooks. If this
23076 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23078 @c It would be nice if hookpost could be passed a parameter indicating
23079 @c if the command it hooks executed properly or not. FIXME!
23081 @kindex stop@r{, a pseudo-command}
23082 In addition, a pseudo-command, @samp{stop} exists. Defining
23083 (@samp{hook-stop}) makes the associated commands execute every time
23084 execution stops in your program: before breakpoint commands are run,
23085 displays are printed, or the stack frame is printed.
23087 For example, to ignore @code{SIGALRM} signals while
23088 single-stepping, but treat them normally during normal execution,
23093 handle SIGALRM nopass
23097 handle SIGALRM pass
23100 define hook-continue
23101 handle SIGALRM pass
23105 As a further example, to hook at the beginning and end of the @code{echo}
23106 command, and to add extra text to the beginning and end of the message,
23114 define hookpost-echo
23118 (@value{GDBP}) echo Hello World
23119 <<<---Hello World--->>>
23124 You can define a hook for any single-word command in @value{GDBN}, but
23125 not for command aliases; you should define a hook for the basic command
23126 name, e.g.@: @code{backtrace} rather than @code{bt}.
23127 @c FIXME! So how does Joe User discover whether a command is an alias
23129 You can hook a multi-word command by adding @code{hook-} or
23130 @code{hookpost-} to the last word of the command, e.g.@:
23131 @samp{define target hook-remote} to add a hook to @samp{target remote}.
23133 If an error occurs during the execution of your hook, execution of
23134 @value{GDBN} commands stops and @value{GDBN} issues a prompt
23135 (before the command that you actually typed had a chance to run).
23137 If you try to define a hook which does not match any known command, you
23138 get a warning from the @code{define} command.
23140 @node Command Files
23141 @subsection Command Files
23143 @cindex command files
23144 @cindex scripting commands
23145 A command file for @value{GDBN} is a text file made of lines that are
23146 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
23147 also be included. An empty line in a command file does nothing; it
23148 does not mean to repeat the last command, as it would from the
23151 You can request the execution of a command file with the @code{source}
23152 command. Note that the @code{source} command is also used to evaluate
23153 scripts that are not Command Files. The exact behavior can be configured
23154 using the @code{script-extension} setting.
23155 @xref{Extending GDB,, Extending GDB}.
23159 @cindex execute commands from a file
23160 @item source [-s] [-v] @var{filename}
23161 Execute the command file @var{filename}.
23164 The lines in a command file are generally executed sequentially,
23165 unless the order of execution is changed by one of the
23166 @emph{flow-control commands} described below. The commands are not
23167 printed as they are executed. An error in any command terminates
23168 execution of the command file and control is returned to the console.
23170 @value{GDBN} first searches for @var{filename} in the current directory.
23171 If the file is not found there, and @var{filename} does not specify a
23172 directory, then @value{GDBN} also looks for the file on the source search path
23173 (specified with the @samp{directory} command);
23174 except that @file{$cdir} is not searched because the compilation directory
23175 is not relevant to scripts.
23177 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
23178 on the search path even if @var{filename} specifies a directory.
23179 The search is done by appending @var{filename} to each element of the
23180 search path. So, for example, if @var{filename} is @file{mylib/myscript}
23181 and the search path contains @file{/home/user} then @value{GDBN} will
23182 look for the script @file{/home/user/mylib/myscript}.
23183 The search is also done if @var{filename} is an absolute path.
23184 For example, if @var{filename} is @file{/tmp/myscript} and
23185 the search path contains @file{/home/user} then @value{GDBN} will
23186 look for the script @file{/home/user/tmp/myscript}.
23187 For DOS-like systems, if @var{filename} contains a drive specification,
23188 it is stripped before concatenation. For example, if @var{filename} is
23189 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
23190 will look for the script @file{c:/tmp/myscript}.
23192 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
23193 each command as it is executed. The option must be given before
23194 @var{filename}, and is interpreted as part of the filename anywhere else.
23196 Commands that would ask for confirmation if used interactively proceed
23197 without asking when used in a command file. Many @value{GDBN} commands that
23198 normally print messages to say what they are doing omit the messages
23199 when called from command files.
23201 @value{GDBN} also accepts command input from standard input. In this
23202 mode, normal output goes to standard output and error output goes to
23203 standard error. Errors in a command file supplied on standard input do
23204 not terminate execution of the command file---execution continues with
23208 gdb < cmds > log 2>&1
23211 (The syntax above will vary depending on the shell used.) This example
23212 will execute commands from the file @file{cmds}. All output and errors
23213 would be directed to @file{log}.
23215 Since commands stored on command files tend to be more general than
23216 commands typed interactively, they frequently need to deal with
23217 complicated situations, such as different or unexpected values of
23218 variables and symbols, changes in how the program being debugged is
23219 built, etc. @value{GDBN} provides a set of flow-control commands to
23220 deal with these complexities. Using these commands, you can write
23221 complex scripts that loop over data structures, execute commands
23222 conditionally, etc.
23229 This command allows to include in your script conditionally executed
23230 commands. The @code{if} command takes a single argument, which is an
23231 expression to evaluate. It is followed by a series of commands that
23232 are executed only if the expression is true (its value is nonzero).
23233 There can then optionally be an @code{else} line, followed by a series
23234 of commands that are only executed if the expression was false. The
23235 end of the list is marked by a line containing @code{end}.
23239 This command allows to write loops. Its syntax is similar to
23240 @code{if}: the command takes a single argument, which is an expression
23241 to evaluate, and must be followed by the commands to execute, one per
23242 line, terminated by an @code{end}. These commands are called the
23243 @dfn{body} of the loop. The commands in the body of @code{while} are
23244 executed repeatedly as long as the expression evaluates to true.
23248 This command exits the @code{while} loop in whose body it is included.
23249 Execution of the script continues after that @code{while}s @code{end}
23252 @kindex loop_continue
23253 @item loop_continue
23254 This command skips the execution of the rest of the body of commands
23255 in the @code{while} loop in whose body it is included. Execution
23256 branches to the beginning of the @code{while} loop, where it evaluates
23257 the controlling expression.
23259 @kindex end@r{ (if/else/while commands)}
23261 Terminate the block of commands that are the body of @code{if},
23262 @code{else}, or @code{while} flow-control commands.
23267 @subsection Commands for Controlled Output
23269 During the execution of a command file or a user-defined command, normal
23270 @value{GDBN} output is suppressed; the only output that appears is what is
23271 explicitly printed by the commands in the definition. This section
23272 describes three commands useful for generating exactly the output you
23277 @item echo @var{text}
23278 @c I do not consider backslash-space a standard C escape sequence
23279 @c because it is not in ANSI.
23280 Print @var{text}. Nonprinting characters can be included in
23281 @var{text} using C escape sequences, such as @samp{\n} to print a
23282 newline. @strong{No newline is printed unless you specify one.}
23283 In addition to the standard C escape sequences, a backslash followed
23284 by a space stands for a space. This is useful for displaying a
23285 string with spaces at the beginning or the end, since leading and
23286 trailing spaces are otherwise trimmed from all arguments.
23287 To print @samp{@w{ }and foo =@w{ }}, use the command
23288 @samp{echo \@w{ }and foo = \@w{ }}.
23290 A backslash at the end of @var{text} can be used, as in C, to continue
23291 the command onto subsequent lines. For example,
23294 echo This is some text\n\
23295 which is continued\n\
23296 onto several lines.\n
23299 produces the same output as
23302 echo This is some text\n
23303 echo which is continued\n
23304 echo onto several lines.\n
23308 @item output @var{expression}
23309 Print the value of @var{expression} and nothing but that value: no
23310 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23311 value history either. @xref{Expressions, ,Expressions}, for more information
23314 @item output/@var{fmt} @var{expression}
23315 Print the value of @var{expression} in format @var{fmt}. You can use
23316 the same formats as for @code{print}. @xref{Output Formats,,Output
23317 Formats}, for more information.
23320 @item printf @var{template}, @var{expressions}@dots{}
23321 Print the values of one or more @var{expressions} under the control of
23322 the string @var{template}. To print several values, make
23323 @var{expressions} be a comma-separated list of individual expressions,
23324 which may be either numbers or pointers. Their values are printed as
23325 specified by @var{template}, exactly as a C program would do by
23326 executing the code below:
23329 printf (@var{template}, @var{expressions}@dots{});
23332 As in @code{C} @code{printf}, ordinary characters in @var{template}
23333 are printed verbatim, while @dfn{conversion specification} introduced
23334 by the @samp{%} character cause subsequent @var{expressions} to be
23335 evaluated, their values converted and formatted according to type and
23336 style information encoded in the conversion specifications, and then
23339 For example, you can print two values in hex like this:
23342 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23345 @code{printf} supports all the standard @code{C} conversion
23346 specifications, including the flags and modifiers between the @samp{%}
23347 character and the conversion letter, with the following exceptions:
23351 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23354 The modifier @samp{*} is not supported for specifying precision or
23358 The @samp{'} flag (for separation of digits into groups according to
23359 @code{LC_NUMERIC'}) is not supported.
23362 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23366 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23369 The conversion letters @samp{a} and @samp{A} are not supported.
23373 Note that the @samp{ll} type modifier is supported only if the
23374 underlying @code{C} implementation used to build @value{GDBN} supports
23375 the @code{long long int} type, and the @samp{L} type modifier is
23376 supported only if @code{long double} type is available.
23378 As in @code{C}, @code{printf} supports simple backslash-escape
23379 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23380 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23381 single character. Octal and hexadecimal escape sequences are not
23384 Additionally, @code{printf} supports conversion specifications for DFP
23385 (@dfn{Decimal Floating Point}) types using the following length modifiers
23386 together with a floating point specifier.
23391 @samp{H} for printing @code{Decimal32} types.
23394 @samp{D} for printing @code{Decimal64} types.
23397 @samp{DD} for printing @code{Decimal128} types.
23400 If the underlying @code{C} implementation used to build @value{GDBN} has
23401 support for the three length modifiers for DFP types, other modifiers
23402 such as width and precision will also be available for @value{GDBN} to use.
23404 In case there is no such @code{C} support, no additional modifiers will be
23405 available and the value will be printed in the standard way.
23407 Here's an example of printing DFP types using the above conversion letters:
23409 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23413 @item eval @var{template}, @var{expressions}@dots{}
23414 Convert the values of one or more @var{expressions} under the control of
23415 the string @var{template} to a command line, and call it.
23419 @node Auto-loading sequences
23420 @subsection Controlling auto-loading native @value{GDBN} scripts
23421 @cindex native script auto-loading
23423 When a new object file is read (for example, due to the @code{file}
23424 command, or because the inferior has loaded a shared library),
23425 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
23426 @xref{Auto-loading extensions}.
23428 Auto-loading can be enabled or disabled,
23429 and the list of auto-loaded scripts can be printed.
23432 @anchor{set auto-load gdb-scripts}
23433 @kindex set auto-load gdb-scripts
23434 @item set auto-load gdb-scripts [on|off]
23435 Enable or disable the auto-loading of canned sequences of commands scripts.
23437 @anchor{show auto-load gdb-scripts}
23438 @kindex show auto-load gdb-scripts
23439 @item show auto-load gdb-scripts
23440 Show whether auto-loading of canned sequences of commands scripts is enabled or
23443 @anchor{info auto-load gdb-scripts}
23444 @kindex info auto-load gdb-scripts
23445 @cindex print list of auto-loaded canned sequences of commands scripts
23446 @item info auto-load gdb-scripts [@var{regexp}]
23447 Print the list of all canned sequences of commands scripts that @value{GDBN}
23451 If @var{regexp} is supplied only canned sequences of commands scripts with
23452 matching names are printed.
23455 @section Extending @value{GDBN} using Python
23456 @cindex python scripting
23457 @cindex scripting with python
23459 You can extend @value{GDBN} using the @uref{http://www.python.org/,
23460 Python programming language}. This feature is available only if
23461 @value{GDBN} was configured using @option{--with-python}.
23463 @cindex python directory
23464 Python scripts used by @value{GDBN} should be installed in
23465 @file{@var{data-directory}/python}, where @var{data-directory} is
23466 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23467 This directory, known as the @dfn{python directory},
23468 is automatically added to the Python Search Path in order to allow
23469 the Python interpreter to locate all scripts installed at this location.
23471 Additionally, @value{GDBN} commands and convenience functions which
23472 are written in Python and are located in the
23473 @file{@var{data-directory}/python/gdb/command} or
23474 @file{@var{data-directory}/python/gdb/function} directories are
23475 automatically imported when @value{GDBN} starts.
23478 * Python Commands:: Accessing Python from @value{GDBN}.
23479 * Python API:: Accessing @value{GDBN} from Python.
23480 * Python Auto-loading:: Automatically loading Python code.
23481 * Python modules:: Python modules provided by @value{GDBN}.
23484 @node Python Commands
23485 @subsection Python Commands
23486 @cindex python commands
23487 @cindex commands to access python
23489 @value{GDBN} provides two commands for accessing the Python interpreter,
23490 and one related setting:
23493 @kindex python-interactive
23495 @item python-interactive @r{[}@var{command}@r{]}
23496 @itemx pi @r{[}@var{command}@r{]}
23497 Without an argument, the @code{python-interactive} command can be used
23498 to start an interactive Python prompt. To return to @value{GDBN},
23499 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23501 Alternatively, a single-line Python command can be given as an
23502 argument and evaluated. If the command is an expression, the result
23503 will be printed; otherwise, nothing will be printed. For example:
23506 (@value{GDBP}) python-interactive 2 + 3
23512 @item python @r{[}@var{command}@r{]}
23513 @itemx py @r{[}@var{command}@r{]}
23514 The @code{python} command can be used to evaluate Python code.
23516 If given an argument, the @code{python} command will evaluate the
23517 argument as a Python command. For example:
23520 (@value{GDBP}) python print 23
23524 If you do not provide an argument to @code{python}, it will act as a
23525 multi-line command, like @code{define}. In this case, the Python
23526 script is made up of subsequent command lines, given after the
23527 @code{python} command. This command list is terminated using a line
23528 containing @code{end}. For example:
23531 (@value{GDBP}) python
23533 End with a line saying just "end".
23539 @kindex set python print-stack
23540 @item set python print-stack
23541 By default, @value{GDBN} will print only the message component of a
23542 Python exception when an error occurs in a Python script. This can be
23543 controlled using @code{set python print-stack}: if @code{full}, then
23544 full Python stack printing is enabled; if @code{none}, then Python stack
23545 and message printing is disabled; if @code{message}, the default, only
23546 the message component of the error is printed.
23549 It is also possible to execute a Python script from the @value{GDBN}
23553 @item source @file{script-name}
23554 The script name must end with @samp{.py} and @value{GDBN} must be configured
23555 to recognize the script language based on filename extension using
23556 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23558 @item python execfile ("script-name")
23559 This method is based on the @code{execfile} Python built-in function,
23560 and thus is always available.
23564 @subsection Python API
23566 @cindex programming in python
23568 You can get quick online help for @value{GDBN}'s Python API by issuing
23569 the command @w{@kbd{python help (gdb)}}.
23571 Functions and methods which have two or more optional arguments allow
23572 them to be specified using keyword syntax. This allows passing some
23573 optional arguments while skipping others. Example:
23574 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23577 * Basic Python:: Basic Python Functions.
23578 * Exception Handling:: How Python exceptions are translated.
23579 * Values From Inferior:: Python representation of values.
23580 * Types In Python:: Python representation of types.
23581 * Pretty Printing API:: Pretty-printing values.
23582 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23583 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23584 * Type Printing API:: Pretty-printing types.
23585 * Frame Filter API:: Filtering Frames.
23586 * Frame Decorator API:: Decorating Frames.
23587 * Writing a Frame Filter:: Writing a Frame Filter.
23588 * Inferiors In Python:: Python representation of inferiors (processes)
23589 * Events In Python:: Listening for events from @value{GDBN}.
23590 * Threads In Python:: Accessing inferior threads from Python.
23591 * Commands In Python:: Implementing new commands in Python.
23592 * Parameters In Python:: Adding new @value{GDBN} parameters.
23593 * Functions In Python:: Writing new convenience functions.
23594 * Progspaces In Python:: Program spaces.
23595 * Objfiles In Python:: Object files.
23596 * Frames In Python:: Accessing inferior stack frames from Python.
23597 * Blocks In Python:: Accessing blocks from Python.
23598 * Symbols In Python:: Python representation of symbols.
23599 * Symbol Tables In Python:: Python representation of symbol tables.
23600 * Line Tables In Python:: Python representation of line tables.
23601 * Breakpoints In Python:: Manipulating breakpoints using Python.
23602 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23604 * Lazy Strings In Python:: Python representation of lazy strings.
23605 * Architectures In Python:: Python representation of architectures.
23609 @subsubsection Basic Python
23611 @cindex python stdout
23612 @cindex python pagination
23613 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23614 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23615 A Python program which outputs to one of these streams may have its
23616 output interrupted by the user (@pxref{Screen Size}). In this
23617 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23619 Some care must be taken when writing Python code to run in
23620 @value{GDBN}. Two things worth noting in particular:
23624 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23625 Python code must not override these, or even change the options using
23626 @code{sigaction}. If your program changes the handling of these
23627 signals, @value{GDBN} will most likely stop working correctly. Note
23628 that it is unfortunately common for GUI toolkits to install a
23629 @code{SIGCHLD} handler.
23632 @value{GDBN} takes care to mark its internal file descriptors as
23633 close-on-exec. However, this cannot be done in a thread-safe way on
23634 all platforms. Your Python programs should be aware of this and
23635 should both create new file descriptors with the close-on-exec flag
23636 set and arrange to close unneeded file descriptors before starting a
23640 @cindex python functions
23641 @cindex python module
23643 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23644 methods and classes added by @value{GDBN} are placed in this module.
23645 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23646 use in all scripts evaluated by the @code{python} command.
23648 @findex gdb.PYTHONDIR
23649 @defvar gdb.PYTHONDIR
23650 A string containing the python directory (@pxref{Python}).
23653 @findex gdb.execute
23654 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23655 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23656 If a GDB exception happens while @var{command} runs, it is
23657 translated as described in @ref{Exception Handling,,Exception Handling}.
23659 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23660 command as having originated from the user invoking it interactively.
23661 It must be a boolean value. If omitted, it defaults to @code{False}.
23663 By default, any output produced by @var{command} is sent to
23664 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23665 @code{True}, then output will be collected by @code{gdb.execute} and
23666 returned as a string. The default is @code{False}, in which case the
23667 return value is @code{None}. If @var{to_string} is @code{True}, the
23668 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23669 and height, and its pagination will be disabled; @pxref{Screen Size}.
23672 @findex gdb.breakpoints
23673 @defun gdb.breakpoints ()
23674 Return a sequence holding all of @value{GDBN}'s breakpoints.
23675 @xref{Breakpoints In Python}, for more information.
23678 @findex gdb.parameter
23679 @defun gdb.parameter (parameter)
23680 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23681 string naming the parameter to look up; @var{parameter} may contain
23682 spaces if the parameter has a multi-part name. For example,
23683 @samp{print object} is a valid parameter name.
23685 If the named parameter does not exist, this function throws a
23686 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23687 parameter's value is converted to a Python value of the appropriate
23688 type, and returned.
23691 @findex gdb.history
23692 @defun gdb.history (number)
23693 Return a value from @value{GDBN}'s value history (@pxref{Value
23694 History}). @var{number} indicates which history element to return.
23695 If @var{number} is negative, then @value{GDBN} will take its absolute value
23696 and count backward from the last element (i.e., the most recent element) to
23697 find the value to return. If @var{number} is zero, then @value{GDBN} will
23698 return the most recent element. If the element specified by @var{number}
23699 doesn't exist in the value history, a @code{gdb.error} exception will be
23702 If no exception is raised, the return value is always an instance of
23703 @code{gdb.Value} (@pxref{Values From Inferior}).
23706 @findex gdb.parse_and_eval
23707 @defun gdb.parse_and_eval (expression)
23708 Parse @var{expression} as an expression in the current language,
23709 evaluate it, and return the result as a @code{gdb.Value}.
23710 @var{expression} must be a string.
23712 This function can be useful when implementing a new command
23713 (@pxref{Commands In Python}), as it provides a way to parse the
23714 command's argument as an expression. It is also useful simply to
23715 compute values, for example, it is the only way to get the value of a
23716 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23719 @findex gdb.find_pc_line
23720 @defun gdb.find_pc_line (pc)
23721 Return the @code{gdb.Symtab_and_line} object corresponding to the
23722 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23723 value of @var{pc} is passed as an argument, then the @code{symtab} and
23724 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23725 will be @code{None} and 0 respectively.
23728 @findex gdb.post_event
23729 @defun gdb.post_event (event)
23730 Put @var{event}, a callable object taking no arguments, into
23731 @value{GDBN}'s internal event queue. This callable will be invoked at
23732 some later point, during @value{GDBN}'s event processing. Events
23733 posted using @code{post_event} will be run in the order in which they
23734 were posted; however, there is no way to know when they will be
23735 processed relative to other events inside @value{GDBN}.
23737 @value{GDBN} is not thread-safe. If your Python program uses multiple
23738 threads, you must be careful to only call @value{GDBN}-specific
23739 functions in the main @value{GDBN} thread. @code{post_event} ensures
23743 (@value{GDBP}) python
23747 > def __init__(self, message):
23748 > self.message = message;
23749 > def __call__(self):
23750 > gdb.write(self.message)
23752 >class MyThread1 (threading.Thread):
23754 > gdb.post_event(Writer("Hello "))
23756 >class MyThread2 (threading.Thread):
23758 > gdb.post_event(Writer("World\n"))
23760 >MyThread1().start()
23761 >MyThread2().start()
23763 (@value{GDBP}) Hello World
23768 @defun gdb.write (string @r{[}, stream{]})
23769 Print a string to @value{GDBN}'s paginated output stream. The
23770 optional @var{stream} determines the stream to print to. The default
23771 stream is @value{GDBN}'s standard output stream. Possible stream
23778 @value{GDBN}'s standard output stream.
23783 @value{GDBN}'s standard error stream.
23788 @value{GDBN}'s log stream (@pxref{Logging Output}).
23791 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23792 call this function and will automatically direct the output to the
23797 @defun gdb.flush ()
23798 Flush the buffer of a @value{GDBN} paginated stream so that the
23799 contents are displayed immediately. @value{GDBN} will flush the
23800 contents of a stream automatically when it encounters a newline in the
23801 buffer. The optional @var{stream} determines the stream to flush. The
23802 default stream is @value{GDBN}'s standard output stream. Possible
23809 @value{GDBN}'s standard output stream.
23814 @value{GDBN}'s standard error stream.
23819 @value{GDBN}'s log stream (@pxref{Logging Output}).
23823 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23824 call this function for the relevant stream.
23827 @findex gdb.target_charset
23828 @defun gdb.target_charset ()
23829 Return the name of the current target character set (@pxref{Character
23830 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23831 that @samp{auto} is never returned.
23834 @findex gdb.target_wide_charset
23835 @defun gdb.target_wide_charset ()
23836 Return the name of the current target wide character set
23837 (@pxref{Character Sets}). This differs from
23838 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23842 @findex gdb.solib_name
23843 @defun gdb.solib_name (address)
23844 Return the name of the shared library holding the given @var{address}
23845 as a string, or @code{None}.
23848 @findex gdb.decode_line
23849 @defun gdb.decode_line @r{[}expression@r{]}
23850 Return locations of the line specified by @var{expression}, or of the
23851 current line if no argument was given. This function returns a Python
23852 tuple containing two elements. The first element contains a string
23853 holding any unparsed section of @var{expression} (or @code{None} if
23854 the expression has been fully parsed). The second element contains
23855 either @code{None} or another tuple that contains all the locations
23856 that match the expression represented as @code{gdb.Symtab_and_line}
23857 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23858 provided, it is decoded the way that @value{GDBN}'s inbuilt
23859 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23862 @defun gdb.prompt_hook (current_prompt)
23863 @anchor{prompt_hook}
23865 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23866 assigned to this operation before a prompt is displayed by
23869 The parameter @code{current_prompt} contains the current @value{GDBN}
23870 prompt. This method must return a Python string, or @code{None}. If
23871 a string is returned, the @value{GDBN} prompt will be set to that
23872 string. If @code{None} is returned, @value{GDBN} will continue to use
23873 the current prompt.
23875 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23876 such as those used by readline for command input, and annotation
23877 related prompts are prohibited from being changed.
23880 @node Exception Handling
23881 @subsubsection Exception Handling
23882 @cindex python exceptions
23883 @cindex exceptions, python
23885 When executing the @code{python} command, Python exceptions
23886 uncaught within the Python code are translated to calls to
23887 @value{GDBN} error-reporting mechanism. If the command that called
23888 @code{python} does not handle the error, @value{GDBN} will
23889 terminate it and print an error message containing the Python
23890 exception name, the associated value, and the Python call stack
23891 backtrace at the point where the exception was raised. Example:
23894 (@value{GDBP}) python print foo
23895 Traceback (most recent call last):
23896 File "<string>", line 1, in <module>
23897 NameError: name 'foo' is not defined
23900 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23901 Python code are converted to Python exceptions. The type of the
23902 Python exception depends on the error.
23906 This is the base class for most exceptions generated by @value{GDBN}.
23907 It is derived from @code{RuntimeError}, for compatibility with earlier
23908 versions of @value{GDBN}.
23910 If an error occurring in @value{GDBN} does not fit into some more
23911 specific category, then the generated exception will have this type.
23913 @item gdb.MemoryError
23914 This is a subclass of @code{gdb.error} which is thrown when an
23915 operation tried to access invalid memory in the inferior.
23917 @item KeyboardInterrupt
23918 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23919 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23922 In all cases, your exception handler will see the @value{GDBN} error
23923 message as its value and the Python call stack backtrace at the Python
23924 statement closest to where the @value{GDBN} error occured as the
23927 @findex gdb.GdbError
23928 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23929 it is useful to be able to throw an exception that doesn't cause a
23930 traceback to be printed. For example, the user may have invoked the
23931 command incorrectly. Use the @code{gdb.GdbError} exception
23932 to handle this case. Example:
23936 >class HelloWorld (gdb.Command):
23937 > """Greet the whole world."""
23938 > def __init__ (self):
23939 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23940 > def invoke (self, args, from_tty):
23941 > argv = gdb.string_to_argv (args)
23942 > if len (argv) != 0:
23943 > raise gdb.GdbError ("hello-world takes no arguments")
23944 > print "Hello, World!"
23947 (gdb) hello-world 42
23948 hello-world takes no arguments
23951 @node Values From Inferior
23952 @subsubsection Values From Inferior
23953 @cindex values from inferior, with Python
23954 @cindex python, working with values from inferior
23956 @cindex @code{gdb.Value}
23957 @value{GDBN} provides values it obtains from the inferior program in
23958 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23959 for its internal bookkeeping of the inferior's values, and for
23960 fetching values when necessary.
23962 Inferior values that are simple scalars can be used directly in
23963 Python expressions that are valid for the value's data type. Here's
23964 an example for an integer or floating-point value @code{some_val}:
23971 As result of this, @code{bar} will also be a @code{gdb.Value} object
23972 whose values are of the same type as those of @code{some_val}.
23974 Inferior values that are structures or instances of some class can
23975 be accessed using the Python @dfn{dictionary syntax}. For example, if
23976 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23977 can access its @code{foo} element with:
23980 bar = some_val['foo']
23983 @cindex getting structure elements using gdb.Field objects as subscripts
23984 Again, @code{bar} will also be a @code{gdb.Value} object. Structure
23985 elements can also be accessed by using @code{gdb.Field} objects as
23986 subscripts (@pxref{Types In Python}, for more information on
23987 @code{gdb.Field} objects). For example, if @code{foo_field} is a
23988 @code{gdb.Field} object corresponding to element @code{foo} of the above
23989 structure, then @code{bar} can also be accessed as follows:
23992 bar = some_val[foo_field]
23995 A @code{gdb.Value} that represents a function can be executed via
23996 inferior function call. Any arguments provided to the call must match
23997 the function's prototype, and must be provided in the order specified
24000 For example, @code{some_val} is a @code{gdb.Value} instance
24001 representing a function that takes two integers as arguments. To
24002 execute this function, call it like so:
24005 result = some_val (10,20)
24008 Any values returned from a function call will be stored as a
24011 The following attributes are provided:
24013 @defvar Value.address
24014 If this object is addressable, this read-only attribute holds a
24015 @code{gdb.Value} object representing the address. Otherwise,
24016 this attribute holds @code{None}.
24019 @cindex optimized out value in Python
24020 @defvar Value.is_optimized_out
24021 This read-only boolean attribute is true if the compiler optimized out
24022 this value, thus it is not available for fetching from the inferior.
24026 The type of this @code{gdb.Value}. The value of this attribute is a
24027 @code{gdb.Type} object (@pxref{Types In Python}).
24030 @defvar Value.dynamic_type
24031 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
24032 type information (@acronym{RTTI}) to determine the dynamic type of the
24033 value. If this value is of class type, it will return the class in
24034 which the value is embedded, if any. If this value is of pointer or
24035 reference to a class type, it will compute the dynamic type of the
24036 referenced object, and return a pointer or reference to that type,
24037 respectively. In all other cases, it will return the value's static
24040 Note that this feature will only work when debugging a C@t{++} program
24041 that includes @acronym{RTTI} for the object in question. Otherwise,
24042 it will just return the static type of the value as in @kbd{ptype foo}
24043 (@pxref{Symbols, ptype}).
24046 @defvar Value.is_lazy
24047 The value of this read-only boolean attribute is @code{True} if this
24048 @code{gdb.Value} has not yet been fetched from the inferior.
24049 @value{GDBN} does not fetch values until necessary, for efficiency.
24053 myval = gdb.parse_and_eval ('somevar')
24056 The value of @code{somevar} is not fetched at this time. It will be
24057 fetched when the value is needed, or when the @code{fetch_lazy}
24061 The following methods are provided:
24063 @defun Value.__init__ (@var{val})
24064 Many Python values can be converted directly to a @code{gdb.Value} via
24065 this object initializer. Specifically:
24068 @item Python boolean
24069 A Python boolean is converted to the boolean type from the current
24072 @item Python integer
24073 A Python integer is converted to the C @code{long} type for the
24074 current architecture.
24077 A Python long is converted to the C @code{long long} type for the
24078 current architecture.
24081 A Python float is converted to the C @code{double} type for the
24082 current architecture.
24084 @item Python string
24085 A Python string is converted to a target string, using the current
24088 @item @code{gdb.Value}
24089 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
24091 @item @code{gdb.LazyString}
24092 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
24093 Python}), then the lazy string's @code{value} method is called, and
24094 its result is used.
24098 @defun Value.cast (type)
24099 Return a new instance of @code{gdb.Value} that is the result of
24100 casting this instance to the type described by @var{type}, which must
24101 be a @code{gdb.Type} object. If the cast cannot be performed for some
24102 reason, this method throws an exception.
24105 @defun Value.dereference ()
24106 For pointer data types, this method returns a new @code{gdb.Value} object
24107 whose contents is the object pointed to by the pointer. For example, if
24108 @code{foo} is a C pointer to an @code{int}, declared in your C program as
24115 then you can use the corresponding @code{gdb.Value} to access what
24116 @code{foo} points to like this:
24119 bar = foo.dereference ()
24122 The result @code{bar} will be a @code{gdb.Value} object holding the
24123 value pointed to by @code{foo}.
24125 A similar function @code{Value.referenced_value} exists which also
24126 returns @code{gdb.Value} objects corresonding to the values pointed to
24127 by pointer values (and additionally, values referenced by reference
24128 values). However, the behavior of @code{Value.dereference}
24129 differs from @code{Value.referenced_value} by the fact that the
24130 behavior of @code{Value.dereference} is identical to applying the C
24131 unary operator @code{*} on a given value. For example, consider a
24132 reference to a pointer @code{ptrref}, declared in your C@t{++} program
24136 typedef int *intptr;
24140 intptr &ptrref = ptr;
24143 Though @code{ptrref} is a reference value, one can apply the method
24144 @code{Value.dereference} to the @code{gdb.Value} object corresponding
24145 to it and obtain a @code{gdb.Value} which is identical to that
24146 corresponding to @code{val}. However, if you apply the method
24147 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
24148 object identical to that corresponding to @code{ptr}.
24151 py_ptrref = gdb.parse_and_eval ("ptrref")
24152 py_val = py_ptrref.dereference ()
24153 py_ptr = py_ptrref.referenced_value ()
24156 The @code{gdb.Value} object @code{py_val} is identical to that
24157 corresponding to @code{val}, and @code{py_ptr} is identical to that
24158 corresponding to @code{ptr}. In general, @code{Value.dereference} can
24159 be applied whenever the C unary operator @code{*} can be applied
24160 to the corresponding C value. For those cases where applying both
24161 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
24162 the results obtained need not be identical (as we have seen in the above
24163 example). The results are however identical when applied on
24164 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
24165 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
24168 @defun Value.referenced_value ()
24169 For pointer or reference data types, this method returns a new
24170 @code{gdb.Value} object corresponding to the value referenced by the
24171 pointer/reference value. For pointer data types,
24172 @code{Value.dereference} and @code{Value.referenced_value} produce
24173 identical results. The difference between these methods is that
24174 @code{Value.dereference} cannot get the values referenced by reference
24175 values. For example, consider a reference to an @code{int}, declared
24176 in your C@t{++} program as
24184 then applying @code{Value.dereference} to the @code{gdb.Value} object
24185 corresponding to @code{ref} will result in an error, while applying
24186 @code{Value.referenced_value} will result in a @code{gdb.Value} object
24187 identical to that corresponding to @code{val}.
24190 py_ref = gdb.parse_and_eval ("ref")
24191 er_ref = py_ref.dereference () # Results in error
24192 py_val = py_ref.referenced_value () # Returns the referenced value
24195 The @code{gdb.Value} object @code{py_val} is identical to that
24196 corresponding to @code{val}.
24199 @defun Value.dynamic_cast (type)
24200 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
24201 operator were used. Consult a C@t{++} reference for details.
24204 @defun Value.reinterpret_cast (type)
24205 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
24206 operator were used. Consult a C@t{++} reference for details.
24209 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
24210 If this @code{gdb.Value} represents a string, then this method
24211 converts the contents to a Python string. Otherwise, this method will
24212 throw an exception.
24214 Strings are recognized in a language-specific way; whether a given
24215 @code{gdb.Value} represents a string is determined by the current
24218 For C-like languages, a value is a string if it is a pointer to or an
24219 array of characters or ints. The string is assumed to be terminated
24220 by a zero of the appropriate width. However if the optional length
24221 argument is given, the string will be converted to that given length,
24222 ignoring any embedded zeros that the string may contain.
24224 If the optional @var{encoding} argument is given, it must be a string
24225 naming the encoding of the string in the @code{gdb.Value}, such as
24226 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
24227 the same encodings as the corresponding argument to Python's
24228 @code{string.decode} method, and the Python codec machinery will be used
24229 to convert the string. If @var{encoding} is not given, or if
24230 @var{encoding} is the empty string, then either the @code{target-charset}
24231 (@pxref{Character Sets}) will be used, or a language-specific encoding
24232 will be used, if the current language is able to supply one.
24234 The optional @var{errors} argument is the same as the corresponding
24235 argument to Python's @code{string.decode} method.
24237 If the optional @var{length} argument is given, the string will be
24238 fetched and converted to the given length.
24241 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
24242 If this @code{gdb.Value} represents a string, then this method
24243 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
24244 In Python}). Otherwise, this method will throw an exception.
24246 If the optional @var{encoding} argument is given, it must be a string
24247 naming the encoding of the @code{gdb.LazyString}. Some examples are:
24248 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
24249 @var{encoding} argument is an encoding that @value{GDBN} does
24250 recognize, @value{GDBN} will raise an error.
24252 When a lazy string is printed, the @value{GDBN} encoding machinery is
24253 used to convert the string during printing. If the optional
24254 @var{encoding} argument is not provided, or is an empty string,
24255 @value{GDBN} will automatically select the encoding most suitable for
24256 the string type. For further information on encoding in @value{GDBN}
24257 please see @ref{Character Sets}.
24259 If the optional @var{length} argument is given, the string will be
24260 fetched and encoded to the length of characters specified. If
24261 the @var{length} argument is not provided, the string will be fetched
24262 and encoded until a null of appropriate width is found.
24265 @defun Value.fetch_lazy ()
24266 If the @code{gdb.Value} object is currently a lazy value
24267 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
24268 fetched from the inferior. Any errors that occur in the process
24269 will produce a Python exception.
24271 If the @code{gdb.Value} object is not a lazy value, this method
24274 This method does not return a value.
24278 @node Types In Python
24279 @subsubsection Types In Python
24280 @cindex types in Python
24281 @cindex Python, working with types
24284 @value{GDBN} represents types from the inferior using the class
24287 The following type-related functions are available in the @code{gdb}
24290 @findex gdb.lookup_type
24291 @defun gdb.lookup_type (name @r{[}, block@r{]})
24292 This function looks up a type by name. @var{name} is the name of the
24293 type to look up. It must be a string.
24295 If @var{block} is given, then @var{name} is looked up in that scope.
24296 Otherwise, it is searched for globally.
24298 Ordinarily, this function will return an instance of @code{gdb.Type}.
24299 If the named type cannot be found, it will throw an exception.
24302 If the type is a structure or class type, or an enum type, the fields
24303 of that type can be accessed using the Python @dfn{dictionary syntax}.
24304 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24305 a structure type, you can access its @code{foo} field with:
24308 bar = some_type['foo']
24311 @code{bar} will be a @code{gdb.Field} object; see below under the
24312 description of the @code{Type.fields} method for a description of the
24313 @code{gdb.Field} class.
24315 An instance of @code{Type} has the following attributes:
24318 The type code for this type. The type code will be one of the
24319 @code{TYPE_CODE_} constants defined below.
24323 The name of this type. If this type has no name, then @code{None}
24327 @defvar Type.sizeof
24328 The size of this type, in target @code{char} units. Usually, a
24329 target's @code{char} type will be an 8-bit byte. However, on some
24330 unusual platforms, this type may have a different size.
24334 The tag name for this type. The tag name is the name after
24335 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24336 languages have this concept. If this type has no tag name, then
24337 @code{None} is returned.
24340 The following methods are provided:
24342 @defun Type.fields ()
24343 For structure and union types, this method returns the fields. Range
24344 types have two fields, the minimum and maximum values. Enum types
24345 have one field per enum constant. Function and method types have one
24346 field per parameter. The base types of C@t{++} classes are also
24347 represented as fields. If the type has no fields, or does not fit
24348 into one of these categories, an empty sequence will be returned.
24350 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24353 This attribute is not available for @code{enum} or @code{static}
24354 (as in C@t{++} or Java) fields. The value is the position, counting
24355 in bits, from the start of the containing type.
24358 This attribute is only available for @code{enum} fields, and its value
24359 is the enumeration member's integer representation.
24362 The name of the field, or @code{None} for anonymous fields.
24365 This is @code{True} if the field is artificial, usually meaning that
24366 it was provided by the compiler and not the user. This attribute is
24367 always provided, and is @code{False} if the field is not artificial.
24369 @item is_base_class
24370 This is @code{True} if the field represents a base class of a C@t{++}
24371 structure. This attribute is always provided, and is @code{False}
24372 if the field is not a base class of the type that is the argument of
24373 @code{fields}, or if that type was not a C@t{++} class.
24376 If the field is packed, or is a bitfield, then this will have a
24377 non-zero value, which is the size of the field in bits. Otherwise,
24378 this will be zero; in this case the field's size is given by its type.
24381 The type of the field. This is usually an instance of @code{Type},
24382 but it can be @code{None} in some situations.
24385 The type which contains this field. This is an instance of
24390 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24391 Return a new @code{gdb.Type} object which represents an array of this
24392 type. If one argument is given, it is the inclusive upper bound of
24393 the array; in this case the lower bound is zero. If two arguments are
24394 given, the first argument is the lower bound of the array, and the
24395 second argument is the upper bound of the array. An array's length
24396 must not be negative, but the bounds can be.
24399 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24400 Return a new @code{gdb.Type} object which represents a vector of this
24401 type. If one argument is given, it is the inclusive upper bound of
24402 the vector; in this case the lower bound is zero. If two arguments are
24403 given, the first argument is the lower bound of the vector, and the
24404 second argument is the upper bound of the vector. A vector's length
24405 must not be negative, but the bounds can be.
24407 The difference between an @code{array} and a @code{vector} is that
24408 arrays behave like in C: when used in expressions they decay to a pointer
24409 to the first element whereas vectors are treated as first class values.
24412 @defun Type.const ()
24413 Return a new @code{gdb.Type} object which represents a
24414 @code{const}-qualified variant of this type.
24417 @defun Type.volatile ()
24418 Return a new @code{gdb.Type} object which represents a
24419 @code{volatile}-qualified variant of this type.
24422 @defun Type.unqualified ()
24423 Return a new @code{gdb.Type} object which represents an unqualified
24424 variant of this type. That is, the result is neither @code{const} nor
24428 @defun Type.range ()
24429 Return a Python @code{Tuple} object that contains two elements: the
24430 low bound of the argument type and the high bound of that type. If
24431 the type does not have a range, @value{GDBN} will raise a
24432 @code{gdb.error} exception (@pxref{Exception Handling}).
24435 @defun Type.reference ()
24436 Return a new @code{gdb.Type} object which represents a reference to this
24440 @defun Type.pointer ()
24441 Return a new @code{gdb.Type} object which represents a pointer to this
24445 @defun Type.strip_typedefs ()
24446 Return a new @code{gdb.Type} that represents the real type,
24447 after removing all layers of typedefs.
24450 @defun Type.target ()
24451 Return a new @code{gdb.Type} object which represents the target type
24454 For a pointer type, the target type is the type of the pointed-to
24455 object. For an array type (meaning C-like arrays), the target type is
24456 the type of the elements of the array. For a function or method type,
24457 the target type is the type of the return value. For a complex type,
24458 the target type is the type of the elements. For a typedef, the
24459 target type is the aliased type.
24461 If the type does not have a target, this method will throw an
24465 @defun Type.template_argument (n @r{[}, block@r{]})
24466 If this @code{gdb.Type} is an instantiation of a template, this will
24467 return a new @code{gdb.Type} which represents the type of the
24468 @var{n}th template argument.
24470 If this @code{gdb.Type} is not a template type, this will throw an
24471 exception. Ordinarily, only C@t{++} code will have template types.
24473 If @var{block} is given, then @var{name} is looked up in that scope.
24474 Otherwise, it is searched for globally.
24478 Each type has a code, which indicates what category this type falls
24479 into. The available type categories are represented by constants
24480 defined in the @code{gdb} module:
24483 @findex TYPE_CODE_PTR
24484 @findex gdb.TYPE_CODE_PTR
24485 @item gdb.TYPE_CODE_PTR
24486 The type is a pointer.
24488 @findex TYPE_CODE_ARRAY
24489 @findex gdb.TYPE_CODE_ARRAY
24490 @item gdb.TYPE_CODE_ARRAY
24491 The type is an array.
24493 @findex TYPE_CODE_STRUCT
24494 @findex gdb.TYPE_CODE_STRUCT
24495 @item gdb.TYPE_CODE_STRUCT
24496 The type is a structure.
24498 @findex TYPE_CODE_UNION
24499 @findex gdb.TYPE_CODE_UNION
24500 @item gdb.TYPE_CODE_UNION
24501 The type is a union.
24503 @findex TYPE_CODE_ENUM
24504 @findex gdb.TYPE_CODE_ENUM
24505 @item gdb.TYPE_CODE_ENUM
24506 The type is an enum.
24508 @findex TYPE_CODE_FLAGS
24509 @findex gdb.TYPE_CODE_FLAGS
24510 @item gdb.TYPE_CODE_FLAGS
24511 A bit flags type, used for things such as status registers.
24513 @findex TYPE_CODE_FUNC
24514 @findex gdb.TYPE_CODE_FUNC
24515 @item gdb.TYPE_CODE_FUNC
24516 The type is a function.
24518 @findex TYPE_CODE_INT
24519 @findex gdb.TYPE_CODE_INT
24520 @item gdb.TYPE_CODE_INT
24521 The type is an integer type.
24523 @findex TYPE_CODE_FLT
24524 @findex gdb.TYPE_CODE_FLT
24525 @item gdb.TYPE_CODE_FLT
24526 A floating point type.
24528 @findex TYPE_CODE_VOID
24529 @findex gdb.TYPE_CODE_VOID
24530 @item gdb.TYPE_CODE_VOID
24531 The special type @code{void}.
24533 @findex TYPE_CODE_SET
24534 @findex gdb.TYPE_CODE_SET
24535 @item gdb.TYPE_CODE_SET
24538 @findex TYPE_CODE_RANGE
24539 @findex gdb.TYPE_CODE_RANGE
24540 @item gdb.TYPE_CODE_RANGE
24541 A range type, that is, an integer type with bounds.
24543 @findex TYPE_CODE_STRING
24544 @findex gdb.TYPE_CODE_STRING
24545 @item gdb.TYPE_CODE_STRING
24546 A string type. Note that this is only used for certain languages with
24547 language-defined string types; C strings are not represented this way.
24549 @findex TYPE_CODE_BITSTRING
24550 @findex gdb.TYPE_CODE_BITSTRING
24551 @item gdb.TYPE_CODE_BITSTRING
24552 A string of bits. It is deprecated.
24554 @findex TYPE_CODE_ERROR
24555 @findex gdb.TYPE_CODE_ERROR
24556 @item gdb.TYPE_CODE_ERROR
24557 An unknown or erroneous type.
24559 @findex TYPE_CODE_METHOD
24560 @findex gdb.TYPE_CODE_METHOD
24561 @item gdb.TYPE_CODE_METHOD
24562 A method type, as found in C@t{++} or Java.
24564 @findex TYPE_CODE_METHODPTR
24565 @findex gdb.TYPE_CODE_METHODPTR
24566 @item gdb.TYPE_CODE_METHODPTR
24567 A pointer-to-member-function.
24569 @findex TYPE_CODE_MEMBERPTR
24570 @findex gdb.TYPE_CODE_MEMBERPTR
24571 @item gdb.TYPE_CODE_MEMBERPTR
24572 A pointer-to-member.
24574 @findex TYPE_CODE_REF
24575 @findex gdb.TYPE_CODE_REF
24576 @item gdb.TYPE_CODE_REF
24579 @findex TYPE_CODE_CHAR
24580 @findex gdb.TYPE_CODE_CHAR
24581 @item gdb.TYPE_CODE_CHAR
24584 @findex TYPE_CODE_BOOL
24585 @findex gdb.TYPE_CODE_BOOL
24586 @item gdb.TYPE_CODE_BOOL
24589 @findex TYPE_CODE_COMPLEX
24590 @findex gdb.TYPE_CODE_COMPLEX
24591 @item gdb.TYPE_CODE_COMPLEX
24592 A complex float type.
24594 @findex TYPE_CODE_TYPEDEF
24595 @findex gdb.TYPE_CODE_TYPEDEF
24596 @item gdb.TYPE_CODE_TYPEDEF
24597 A typedef to some other type.
24599 @findex TYPE_CODE_NAMESPACE
24600 @findex gdb.TYPE_CODE_NAMESPACE
24601 @item gdb.TYPE_CODE_NAMESPACE
24602 A C@t{++} namespace.
24604 @findex TYPE_CODE_DECFLOAT
24605 @findex gdb.TYPE_CODE_DECFLOAT
24606 @item gdb.TYPE_CODE_DECFLOAT
24607 A decimal floating point type.
24609 @findex TYPE_CODE_INTERNAL_FUNCTION
24610 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24611 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24612 A function internal to @value{GDBN}. This is the type used to represent
24613 convenience functions.
24616 Further support for types is provided in the @code{gdb.types}
24617 Python module (@pxref{gdb.types}).
24619 @node Pretty Printing API
24620 @subsubsection Pretty Printing API
24622 An example output is provided (@pxref{Pretty Printing}).
24624 A pretty-printer is just an object that holds a value and implements a
24625 specific interface, defined here.
24627 @defun pretty_printer.children (self)
24628 @value{GDBN} will call this method on a pretty-printer to compute the
24629 children of the pretty-printer's value.
24631 This method must return an object conforming to the Python iterator
24632 protocol. Each item returned by the iterator must be a tuple holding
24633 two elements. The first element is the ``name'' of the child; the
24634 second element is the child's value. The value can be any Python
24635 object which is convertible to a @value{GDBN} value.
24637 This method is optional. If it does not exist, @value{GDBN} will act
24638 as though the value has no children.
24641 @defun pretty_printer.display_hint (self)
24642 The CLI may call this method and use its result to change the
24643 formatting of a value. The result will also be supplied to an MI
24644 consumer as a @samp{displayhint} attribute of the variable being
24647 This method is optional. If it does exist, this method must return a
24650 Some display hints are predefined by @value{GDBN}:
24654 Indicate that the object being printed is ``array-like''. The CLI
24655 uses this to respect parameters such as @code{set print elements} and
24656 @code{set print array}.
24659 Indicate that the object being printed is ``map-like'', and that the
24660 children of this value can be assumed to alternate between keys and
24664 Indicate that the object being printed is ``string-like''. If the
24665 printer's @code{to_string} method returns a Python string of some
24666 kind, then @value{GDBN} will call its internal language-specific
24667 string-printing function to format the string. For the CLI this means
24668 adding quotation marks, possibly escaping some characters, respecting
24669 @code{set print elements}, and the like.
24673 @defun pretty_printer.to_string (self)
24674 @value{GDBN} will call this method to display the string
24675 representation of the value passed to the object's constructor.
24677 When printing from the CLI, if the @code{to_string} method exists,
24678 then @value{GDBN} will prepend its result to the values returned by
24679 @code{children}. Exactly how this formatting is done is dependent on
24680 the display hint, and may change as more hints are added. Also,
24681 depending on the print settings (@pxref{Print Settings}), the CLI may
24682 print just the result of @code{to_string} in a stack trace, omitting
24683 the result of @code{children}.
24685 If this method returns a string, it is printed verbatim.
24687 Otherwise, if this method returns an instance of @code{gdb.Value},
24688 then @value{GDBN} prints this value. This may result in a call to
24689 another pretty-printer.
24691 If instead the method returns a Python value which is convertible to a
24692 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24693 the resulting value. Again, this may result in a call to another
24694 pretty-printer. Python scalars (integers, floats, and booleans) and
24695 strings are convertible to @code{gdb.Value}; other types are not.
24697 Finally, if this method returns @code{None} then no further operations
24698 are peformed in this method and nothing is printed.
24700 If the result is not one of these types, an exception is raised.
24703 @value{GDBN} provides a function which can be used to look up the
24704 default pretty-printer for a @code{gdb.Value}:
24706 @findex gdb.default_visualizer
24707 @defun gdb.default_visualizer (value)
24708 This function takes a @code{gdb.Value} object as an argument. If a
24709 pretty-printer for this value exists, then it is returned. If no such
24710 printer exists, then this returns @code{None}.
24713 @node Selecting Pretty-Printers
24714 @subsubsection Selecting Pretty-Printers
24716 The Python list @code{gdb.pretty_printers} contains an array of
24717 functions or callable objects that have been registered via addition
24718 as a pretty-printer. Printers in this list are called @code{global}
24719 printers, they're available when debugging all inferiors.
24720 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24721 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24724 Each function on these lists is passed a single @code{gdb.Value}
24725 argument and should return a pretty-printer object conforming to the
24726 interface definition above (@pxref{Pretty Printing API}). If a function
24727 cannot create a pretty-printer for the value, it should return
24730 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24731 @code{gdb.Objfile} in the current program space and iteratively calls
24732 each enabled lookup routine in the list for that @code{gdb.Objfile}
24733 until it receives a pretty-printer object.
24734 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24735 searches the pretty-printer list of the current program space,
24736 calling each enabled function until an object is returned.
24737 After these lists have been exhausted, it tries the global
24738 @code{gdb.pretty_printers} list, again calling each enabled function until an
24739 object is returned.
24741 The order in which the objfiles are searched is not specified. For a
24742 given list, functions are always invoked from the head of the list,
24743 and iterated over sequentially until the end of the list, or a printer
24744 object is returned.
24746 For various reasons a pretty-printer may not work.
24747 For example, the underlying data structure may have changed and
24748 the pretty-printer is out of date.
24750 The consequences of a broken pretty-printer are severe enough that
24751 @value{GDBN} provides support for enabling and disabling individual
24752 printers. For example, if @code{print frame-arguments} is on,
24753 a backtrace can become highly illegible if any argument is printed
24754 with a broken printer.
24756 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24757 attribute to the registered function or callable object. If this attribute
24758 is present and its value is @code{False}, the printer is disabled, otherwise
24759 the printer is enabled.
24761 @node Writing a Pretty-Printer
24762 @subsubsection Writing a Pretty-Printer
24763 @cindex writing a pretty-printer
24765 A pretty-printer consists of two parts: a lookup function to detect
24766 if the type is supported, and the printer itself.
24768 Here is an example showing how a @code{std::string} printer might be
24769 written. @xref{Pretty Printing API}, for details on the API this class
24773 class StdStringPrinter(object):
24774 "Print a std::string"
24776 def __init__(self, val):
24779 def to_string(self):
24780 return self.val['_M_dataplus']['_M_p']
24782 def display_hint(self):
24786 And here is an example showing how a lookup function for the printer
24787 example above might be written.
24790 def str_lookup_function(val):
24791 lookup_tag = val.type.tag
24792 if lookup_tag == None:
24794 regex = re.compile("^std::basic_string<char,.*>$")
24795 if regex.match(lookup_tag):
24796 return StdStringPrinter(val)
24800 The example lookup function extracts the value's type, and attempts to
24801 match it to a type that it can pretty-print. If it is a type the
24802 printer can pretty-print, it will return a printer object. If not, it
24803 returns @code{None}.
24805 We recommend that you put your core pretty-printers into a Python
24806 package. If your pretty-printers are for use with a library, we
24807 further recommend embedding a version number into the package name.
24808 This practice will enable @value{GDBN} to load multiple versions of
24809 your pretty-printers at the same time, because they will have
24812 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24813 can be evaluated multiple times without changing its meaning. An
24814 ideal auto-load file will consist solely of @code{import}s of your
24815 printer modules, followed by a call to a register pretty-printers with
24816 the current objfile.
24818 Taken as a whole, this approach will scale nicely to multiple
24819 inferiors, each potentially using a different library version.
24820 Embedding a version number in the Python package name will ensure that
24821 @value{GDBN} is able to load both sets of printers simultaneously.
24822 Then, because the search for pretty-printers is done by objfile, and
24823 because your auto-loaded code took care to register your library's
24824 printers with a specific objfile, @value{GDBN} will find the correct
24825 printers for the specific version of the library used by each
24828 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24829 this code might appear in @code{gdb.libstdcxx.v6}:
24832 def register_printers(objfile):
24833 objfile.pretty_printers.append(str_lookup_function)
24837 And then the corresponding contents of the auto-load file would be:
24840 import gdb.libstdcxx.v6
24841 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24844 The previous example illustrates a basic pretty-printer.
24845 There are a few things that can be improved on.
24846 The printer doesn't have a name, making it hard to identify in a
24847 list of installed printers. The lookup function has a name, but
24848 lookup functions can have arbitrary, even identical, names.
24850 Second, the printer only handles one type, whereas a library typically has
24851 several types. One could install a lookup function for each desired type
24852 in the library, but one could also have a single lookup function recognize
24853 several types. The latter is the conventional way this is handled.
24854 If a pretty-printer can handle multiple data types, then its
24855 @dfn{subprinters} are the printers for the individual data types.
24857 The @code{gdb.printing} module provides a formal way of solving these
24858 problems (@pxref{gdb.printing}).
24859 Here is another example that handles multiple types.
24861 These are the types we are going to pretty-print:
24864 struct foo @{ int a, b; @};
24865 struct bar @{ struct foo x, y; @};
24868 Here are the printers:
24872 """Print a foo object."""
24874 def __init__(self, val):
24877 def to_string(self):
24878 return ("a=<" + str(self.val["a"]) +
24879 "> b=<" + str(self.val["b"]) + ">")
24882 """Print a bar object."""
24884 def __init__(self, val):
24887 def to_string(self):
24888 return ("x=<" + str(self.val["x"]) +
24889 "> y=<" + str(self.val["y"]) + ">")
24892 This example doesn't need a lookup function, that is handled by the
24893 @code{gdb.printing} module. Instead a function is provided to build up
24894 the object that handles the lookup.
24897 import gdb.printing
24899 def build_pretty_printer():
24900 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24902 pp.add_printer('foo', '^foo$', fooPrinter)
24903 pp.add_printer('bar', '^bar$', barPrinter)
24907 And here is the autoload support:
24910 import gdb.printing
24912 gdb.printing.register_pretty_printer(
24913 gdb.current_objfile(),
24914 my_library.build_pretty_printer())
24917 Finally, when this printer is loaded into @value{GDBN}, here is the
24918 corresponding output of @samp{info pretty-printer}:
24921 (gdb) info pretty-printer
24928 @node Type Printing API
24929 @subsubsection Type Printing API
24930 @cindex type printing API for Python
24932 @value{GDBN} provides a way for Python code to customize type display.
24933 This is mainly useful for substituting canonical typedef names for
24936 @cindex type printer
24937 A @dfn{type printer} is just a Python object conforming to a certain
24938 protocol. A simple base class implementing the protocol is provided;
24939 see @ref{gdb.types}. A type printer must supply at least:
24941 @defivar type_printer enabled
24942 A boolean which is True if the printer is enabled, and False
24943 otherwise. This is manipulated by the @code{enable type-printer}
24944 and @code{disable type-printer} commands.
24947 @defivar type_printer name
24948 The name of the type printer. This must be a string. This is used by
24949 the @code{enable type-printer} and @code{disable type-printer}
24953 @defmethod type_printer instantiate (self)
24954 This is called by @value{GDBN} at the start of type-printing. It is
24955 only called if the type printer is enabled. This method must return a
24956 new object that supplies a @code{recognize} method, as described below.
24960 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24961 will compute a list of type recognizers. This is done by iterating
24962 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24963 followed by the per-progspace type printers (@pxref{Progspaces In
24964 Python}), and finally the global type printers.
24966 @value{GDBN} will call the @code{instantiate} method of each enabled
24967 type printer. If this method returns @code{None}, then the result is
24968 ignored; otherwise, it is appended to the list of recognizers.
24970 Then, when @value{GDBN} is going to display a type name, it iterates
24971 over the list of recognizers. For each one, it calls the recognition
24972 function, stopping if the function returns a non-@code{None} value.
24973 The recognition function is defined as:
24975 @defmethod type_recognizer recognize (self, type)
24976 If @var{type} is not recognized, return @code{None}. Otherwise,
24977 return a string which is to be printed as the name of @var{type}.
24978 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24982 @value{GDBN} uses this two-pass approach so that type printers can
24983 efficiently cache information without holding on to it too long. For
24984 example, it can be convenient to look up type information in a type
24985 printer and hold it for a recognizer's lifetime; if a single pass were
24986 done then type printers would have to make use of the event system in
24987 order to avoid holding information that could become stale as the
24990 @node Frame Filter API
24991 @subsubsection Filtering Frames.
24992 @cindex frame filters api
24994 Frame filters are Python objects that manipulate the visibility of a
24995 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24998 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24999 commands (@pxref{GDB/MI}), those that return a collection of frames
25000 are affected. The commands that work with frame filters are:
25002 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
25003 @code{-stack-list-frames}
25004 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
25005 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
25006 -stack-list-variables command}), @code{-stack-list-arguments}
25007 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
25008 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
25009 -stack-list-locals command}).
25011 A frame filter works by taking an iterator as an argument, applying
25012 actions to the contents of that iterator, and returning another
25013 iterator (or, possibly, the same iterator it was provided in the case
25014 where the filter does not perform any operations). Typically, frame
25015 filters utilize tools such as the Python's @code{itertools} module to
25016 work with and create new iterators from the source iterator.
25017 Regardless of how a filter chooses to apply actions, it must not alter
25018 the underlying @value{GDBN} frame or frames, or attempt to alter the
25019 call-stack within @value{GDBN}. This preserves data integrity within
25020 @value{GDBN}. Frame filters are executed on a priority basis and care
25021 should be taken that some frame filters may have been executed before,
25022 and that some frame filters will be executed after.
25024 An important consideration when designing frame filters, and well
25025 worth reflecting upon, is that frame filters should avoid unwinding
25026 the call stack if possible. Some stacks can run very deep, into the
25027 tens of thousands in some cases. To search every frame when a frame
25028 filter executes may be too expensive at that step. The frame filter
25029 cannot know how many frames it has to iterate over, and it may have to
25030 iterate through them all. This ends up duplicating effort as
25031 @value{GDBN} performs this iteration when it prints the frames. If
25032 the filter can defer unwinding frames until frame decorators are
25033 executed, after the last filter has executed, it should. @xref{Frame
25034 Decorator API}, for more information on decorators. Also, there are
25035 examples for both frame decorators and filters in later chapters.
25036 @xref{Writing a Frame Filter}, for more information.
25038 The Python dictionary @code{gdb.frame_filters} contains key/object
25039 pairings that comprise a frame filter. Frame filters in this
25040 dictionary are called @code{global} frame filters, and they are
25041 available when debugging all inferiors. These frame filters must
25042 register with the dictionary directly. In addition to the
25043 @code{global} dictionary, there are other dictionaries that are loaded
25044 with different inferiors via auto-loading (@pxref{Python
25045 Auto-loading}). The two other areas where frame filter dictionaries
25046 can be found are: @code{gdb.Progspace} which contains a
25047 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
25048 object which also contains a @code{frame_filters} dictionary
25051 When a command is executed from @value{GDBN} that is compatible with
25052 frame filters, @value{GDBN} combines the @code{global},
25053 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
25054 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
25055 several frames, and thus several object files, might be in use.
25056 @value{GDBN} then prunes any frame filter whose @code{enabled}
25057 attribute is @code{False}. This pruned list is then sorted according
25058 to the @code{priority} attribute in each filter.
25060 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
25061 creates an iterator which wraps each frame in the call stack in a
25062 @code{FrameDecorator} object, and calls each filter in order. The
25063 output from the previous filter will always be the input to the next
25066 Frame filters have a mandatory interface which each frame filter must
25067 implement, defined here:
25069 @defun FrameFilter.filter (iterator)
25070 @value{GDBN} will call this method on a frame filter when it has
25071 reached the order in the priority list for that filter.
25073 For example, if there are four frame filters:
25084 The order that the frame filters will be called is:
25087 Filter3 -> Filter2 -> Filter1 -> Filter4
25090 Note that the output from @code{Filter3} is passed to the input of
25091 @code{Filter2}, and so on.
25093 This @code{filter} method is passed a Python iterator. This iterator
25094 contains a sequence of frame decorators that wrap each
25095 @code{gdb.Frame}, or a frame decorator that wraps another frame
25096 decorator. The first filter that is executed in the sequence of frame
25097 filters will receive an iterator entirely comprised of default
25098 @code{FrameDecorator} objects. However, after each frame filter is
25099 executed, the previous frame filter may have wrapped some or all of
25100 the frame decorators with their own frame decorator. As frame
25101 decorators must also conform to a mandatory interface, these
25102 decorators can be assumed to act in a uniform manner (@pxref{Frame
25105 This method must return an object conforming to the Python iterator
25106 protocol. Each item in the iterator must be an object conforming to
25107 the frame decorator interface. If a frame filter does not wish to
25108 perform any operations on this iterator, it should return that
25109 iterator untouched.
25111 This method is not optional. If it does not exist, @value{GDBN} will
25112 raise and print an error.
25115 @defvar FrameFilter.name
25116 The @code{name} attribute must be Python string which contains the
25117 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
25118 Management}). This attribute may contain any combination of letters
25119 or numbers. Care should be taken to ensure that it is unique. This
25120 attribute is mandatory.
25123 @defvar FrameFilter.enabled
25124 The @code{enabled} attribute must be Python boolean. This attribute
25125 indicates to @value{GDBN} whether the frame filter is enabled, and
25126 should be considered when frame filters are executed. If
25127 @code{enabled} is @code{True}, then the frame filter will be executed
25128 when any of the backtrace commands detailed earlier in this chapter
25129 are executed. If @code{enabled} is @code{False}, then the frame
25130 filter will not be executed. This attribute is mandatory.
25133 @defvar FrameFilter.priority
25134 The @code{priority} attribute must be Python integer. This attribute
25135 controls the order of execution in relation to other frame filters.
25136 There are no imposed limits on the range of @code{priority} other than
25137 it must be a valid integer. The higher the @code{priority} attribute,
25138 the sooner the frame filter will be executed in relation to other
25139 frame filters. Although @code{priority} can be negative, it is
25140 recommended practice to assume zero is the lowest priority that a
25141 frame filter can be assigned. Frame filters that have the same
25142 priority are executed in unsorted order in that priority slot. This
25143 attribute is mandatory.
25146 @node Frame Decorator API
25147 @subsubsection Decorating Frames.
25148 @cindex frame decorator api
25150 Frame decorators are sister objects to frame filters (@pxref{Frame
25151 Filter API}). Frame decorators are applied by a frame filter and can
25152 only be used in conjunction with frame filters.
25154 The purpose of a frame decorator is to customize the printed content
25155 of each @code{gdb.Frame} in commands where frame filters are executed.
25156 This concept is called decorating a frame. Frame decorators decorate
25157 a @code{gdb.Frame} with Python code contained within each API call.
25158 This separates the actual data contained in a @code{gdb.Frame} from
25159 the decorated data produced by a frame decorator. This abstraction is
25160 necessary to maintain integrity of the data contained in each
25163 Frame decorators have a mandatory interface, defined below.
25165 @value{GDBN} already contains a frame decorator called
25166 @code{FrameDecorator}. This contains substantial amounts of
25167 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
25168 recommended that other frame decorators inherit and extend this
25169 object, and only to override the methods needed.
25171 @defun FrameDecorator.elided (self)
25173 The @code{elided} method groups frames together in a hierarchical
25174 system. An example would be an interpreter, where multiple low-level
25175 frames make up a single call in the interpreted language. In this
25176 example, the frame filter would elide the low-level frames and present
25177 a single high-level frame, representing the call in the interpreted
25178 language, to the user.
25180 The @code{elided} function must return an iterable and this iterable
25181 must contain the frames that are being elided wrapped in a suitable
25182 frame decorator. If no frames are being elided this function may
25183 return an empty iterable, or @code{None}. Elided frames are indented
25184 from normal frames in a @code{CLI} backtrace, or in the case of
25185 @code{GDB/MI}, are placed in the @code{children} field of the eliding
25188 It is the frame filter's task to also filter out the elided frames from
25189 the source iterator. This will avoid printing the frame twice.
25192 @defun FrameDecorator.function (self)
25194 This method returns the name of the function in the frame that is to
25197 This method must return a Python string describing the function, or
25200 If this function returns @code{None}, @value{GDBN} will not print any
25201 data for this field.
25204 @defun FrameDecorator.address (self)
25206 This method returns the address of the frame that is to be printed.
25208 This method must return a Python numeric integer type of sufficient
25209 size to describe the address of the frame, or @code{None}.
25211 If this function returns a @code{None}, @value{GDBN} will not print
25212 any data for this field.
25215 @defun FrameDecorator.filename (self)
25217 This method returns the filename and path associated with this frame.
25219 This method must return a Python string containing the filename and
25220 the path to the object file backing the frame, or @code{None}.
25222 If this function returns a @code{None}, @value{GDBN} will not print
25223 any data for this field.
25226 @defun FrameDecorator.line (self):
25228 This method returns the line number associated with the current
25229 position within the function addressed by this frame.
25231 This method must return a Python integer type, or @code{None}.
25233 If this function returns a @code{None}, @value{GDBN} will not print
25234 any data for this field.
25237 @defun FrameDecorator.frame_args (self)
25238 @anchor{frame_args}
25240 This method must return an iterable, or @code{None}. Returning an
25241 empty iterable, or @code{None} means frame arguments will not be
25242 printed for this frame. This iterable must contain objects that
25243 implement two methods, described here.
25245 This object must implement a @code{argument} method which takes a
25246 single @code{self} parameter and must return a @code{gdb.Symbol}
25247 (@pxref{Symbols In Python}), or a Python string. The object must also
25248 implement a @code{value} method which takes a single @code{self}
25249 parameter and must return a @code{gdb.Value} (@pxref{Values From
25250 Inferior}), a Python value, or @code{None}. If the @code{value}
25251 method returns @code{None}, and the @code{argument} method returns a
25252 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
25253 the @code{gdb.Symbol} automatically.
25258 class SymValueWrapper():
25260 def __init__(self, symbol, value):
25270 class SomeFrameDecorator()
25273 def frame_args(self):
25276 block = self.inferior_frame.block()
25280 # Iterate over all symbols in a block. Only add
25281 # symbols that are arguments.
25283 if not sym.is_argument:
25285 args.append(SymValueWrapper(sym,None))
25287 # Add example synthetic argument.
25288 args.append(SymValueWrapper(``foo'', 42))
25294 @defun FrameDecorator.frame_locals (self)
25296 This method must return an iterable or @code{None}. Returning an
25297 empty iterable, or @code{None} means frame local arguments will not be
25298 printed for this frame.
25300 The object interface, the description of the various strategies for
25301 reading frame locals, and the example are largely similar to those
25302 described in the @code{frame_args} function, (@pxref{frame_args,,The
25303 frame filter frame_args function}). Below is a modified example:
25306 class SomeFrameDecorator()
25309 def frame_locals(self):
25312 block = self.inferior_frame.block()
25316 # Iterate over all symbols in a block. Add all
25317 # symbols, except arguments.
25319 if sym.is_argument:
25321 vars.append(SymValueWrapper(sym,None))
25323 # Add an example of a synthetic local variable.
25324 vars.append(SymValueWrapper(``bar'', 99))
25330 @defun FrameDecorator.inferior_frame (self):
25332 This method must return the underlying @code{gdb.Frame} that this
25333 frame decorator is decorating. @value{GDBN} requires the underlying
25334 frame for internal frame information to determine how to print certain
25335 values when printing a frame.
25338 @node Writing a Frame Filter
25339 @subsubsection Writing a Frame Filter
25340 @cindex writing a frame filter
25342 There are three basic elements that a frame filter must implement: it
25343 must correctly implement the documented interface (@pxref{Frame Filter
25344 API}), it must register itself with @value{GDBN}, and finally, it must
25345 decide if it is to work on the data provided by @value{GDBN}. In all
25346 cases, whether it works on the iterator or not, each frame filter must
25347 return an iterator. A bare-bones frame filter follows the pattern in
25348 the following example.
25353 class FrameFilter():
25355 def __init__(self):
25356 # Frame filter attribute creation.
25358 # 'name' is the name of the filter that GDB will display.
25360 # 'priority' is the priority of the filter relative to other
25363 # 'enabled' is a boolean that indicates whether this filter is
25364 # enabled and should be executed.
25367 self.priority = 100
25368 self.enabled = True
25370 # Register this frame filter with the global frame_filters
25372 gdb.frame_filters[self.name] = self
25374 def filter(self, frame_iter):
25375 # Just return the iterator.
25379 The frame filter in the example above implements the three
25380 requirements for all frame filters. It implements the API, self
25381 registers, and makes a decision on the iterator (in this case, it just
25382 returns the iterator untouched).
25384 The first step is attribute creation and assignment, and as shown in
25385 the comments the filter assigns the following attributes: @code{name},
25386 @code{priority} and whether the filter should be enabled with the
25387 @code{enabled} attribute.
25389 The second step is registering the frame filter with the dictionary or
25390 dictionaries that the frame filter has interest in. As shown in the
25391 comments, this filter just registers itself with the global dictionary
25392 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25393 is a dictionary that is initialized in the @code{gdb} module when
25394 @value{GDBN} starts. What dictionary a filter registers with is an
25395 important consideration. Generally, if a filter is specific to a set
25396 of code, it should be registered either in the @code{objfile} or
25397 @code{progspace} dictionaries as they are specific to the program
25398 currently loaded in @value{GDBN}. The global dictionary is always
25399 present in @value{GDBN} and is never unloaded. Any filters registered
25400 with the global dictionary will exist until @value{GDBN} exits. To
25401 avoid filters that may conflict, it is generally better to register
25402 frame filters against the dictionaries that more closely align with
25403 the usage of the filter currently in question. @xref{Python
25404 Auto-loading}, for further information on auto-loading Python scripts.
25406 @value{GDBN} takes a hands-off approach to frame filter registration,
25407 therefore it is the frame filter's responsibility to ensure
25408 registration has occurred, and that any exceptions are handled
25409 appropriately. In particular, you may wish to handle exceptions
25410 relating to Python dictionary key uniqueness. It is mandatory that
25411 the dictionary key is the same as frame filter's @code{name}
25412 attribute. When a user manages frame filters (@pxref{Frame Filter
25413 Management}), the names @value{GDBN} will display are those contained
25414 in the @code{name} attribute.
25416 The final step of this example is the implementation of the
25417 @code{filter} method. As shown in the example comments, we define the
25418 @code{filter} method and note that the method must take an iterator,
25419 and also must return an iterator. In this bare-bones example, the
25420 frame filter is not very useful as it just returns the iterator
25421 untouched. However this is a valid operation for frame filters that
25422 have the @code{enabled} attribute set, but decide not to operate on
25425 In the next example, the frame filter operates on all frames and
25426 utilizes a frame decorator to perform some work on the frames.
25427 @xref{Frame Decorator API}, for further information on the frame
25428 decorator interface.
25430 This example works on inlined frames. It highlights frames which are
25431 inlined by tagging them with an ``[inlined]'' tag. By applying a
25432 frame decorator to all frames with the Python @code{itertools imap}
25433 method, the example defers actions to the frame decorator. Frame
25434 decorators are only processed when @value{GDBN} prints the backtrace.
25436 This introduces a new decision making topic: whether to perform
25437 decision making operations at the filtering step, or at the printing
25438 step. In this example's approach, it does not perform any filtering
25439 decisions at the filtering step beyond mapping a frame decorator to
25440 each frame. This allows the actual decision making to be performed
25441 when each frame is printed. This is an important consideration, and
25442 well worth reflecting upon when designing a frame filter. An issue
25443 that frame filters should avoid is unwinding the stack if possible.
25444 Some stacks can run very deep, into the tens of thousands in some
25445 cases. To search every frame to determine if it is inlined ahead of
25446 time may be too expensive at the filtering step. The frame filter
25447 cannot know how many frames it has to iterate over, and it would have
25448 to iterate through them all. This ends up duplicating effort as
25449 @value{GDBN} performs this iteration when it prints the frames.
25451 In this example decision making can be deferred to the printing step.
25452 As each frame is printed, the frame decorator can examine each frame
25453 in turn when @value{GDBN} iterates. From a performance viewpoint,
25454 this is the most appropriate decision to make as it avoids duplicating
25455 the effort that the printing step would undertake anyway. Also, if
25456 there are many frame filters unwinding the stack during filtering, it
25457 can substantially delay the printing of the backtrace which will
25458 result in large memory usage, and a poor user experience.
25461 class InlineFilter():
25463 def __init__(self):
25464 self.name = "InlinedFrameFilter"
25465 self.priority = 100
25466 self.enabled = True
25467 gdb.frame_filters[self.name] = self
25469 def filter(self, frame_iter):
25470 frame_iter = itertools.imap(InlinedFrameDecorator,
25475 This frame filter is somewhat similar to the earlier example, except
25476 that the @code{filter} method applies a frame decorator object called
25477 @code{InlinedFrameDecorator} to each element in the iterator. The
25478 @code{imap} Python method is light-weight. It does not proactively
25479 iterate over the iterator, but rather creates a new iterator which
25480 wraps the existing one.
25482 Below is the frame decorator for this example.
25485 class InlinedFrameDecorator(FrameDecorator):
25487 def __init__(self, fobj):
25488 super(InlinedFrameDecorator, self).__init__(fobj)
25490 def function(self):
25491 frame = fobj.inferior_frame()
25492 name = str(frame.name())
25494 if frame.type() == gdb.INLINE_FRAME:
25495 name = name + " [inlined]"
25500 This frame decorator only defines and overrides the @code{function}
25501 method. It lets the supplied @code{FrameDecorator}, which is shipped
25502 with @value{GDBN}, perform the other work associated with printing
25505 The combination of these two objects create this output from a
25509 #0 0x004004e0 in bar () at inline.c:11
25510 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25511 #2 0x00400566 in main () at inline.c:31
25514 So in the case of this example, a frame decorator is applied to all
25515 frames, regardless of whether they may be inlined or not. As
25516 @value{GDBN} iterates over the iterator produced by the frame filters,
25517 @value{GDBN} executes each frame decorator which then makes a decision
25518 on what to print in the @code{function} callback. Using a strategy
25519 like this is a way to defer decisions on the frame content to printing
25522 @subheading Eliding Frames
25524 It might be that the above example is not desirable for representing
25525 inlined frames, and a hierarchical approach may be preferred. If we
25526 want to hierarchically represent frames, the @code{elided} frame
25527 decorator interface might be preferable.
25529 This example approaches the issue with the @code{elided} method. This
25530 example is quite long, but very simplistic. It is out-of-scope for
25531 this section to write a complete example that comprehensively covers
25532 all approaches of finding and printing inlined frames. However, this
25533 example illustrates the approach an author might use.
25535 This example comprises of three sections.
25538 class InlineFrameFilter():
25540 def __init__(self):
25541 self.name = "InlinedFrameFilter"
25542 self.priority = 100
25543 self.enabled = True
25544 gdb.frame_filters[self.name] = self
25546 def filter(self, frame_iter):
25547 return ElidingInlineIterator(frame_iter)
25550 This frame filter is very similar to the other examples. The only
25551 difference is this frame filter is wrapping the iterator provided to
25552 it (@code{frame_iter}) with a custom iterator called
25553 @code{ElidingInlineIterator}. This again defers actions to when
25554 @value{GDBN} prints the backtrace, as the iterator is not traversed
25557 The iterator for this example is as follows. It is in this section of
25558 the example where decisions are made on the content of the backtrace.
25561 class ElidingInlineIterator:
25562 def __init__(self, ii):
25563 self.input_iterator = ii
25565 def __iter__(self):
25569 frame = next(self.input_iterator)
25571 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25575 eliding_frame = next(self.input_iterator)
25576 except StopIteration:
25578 return ElidingFrameDecorator(eliding_frame, [frame])
25581 This iterator implements the Python iterator protocol. When the
25582 @code{next} function is called (when @value{GDBN} prints each frame),
25583 the iterator checks if this frame decorator, @code{frame}, is wrapping
25584 an inlined frame. If it is not, it returns the existing frame decorator
25585 untouched. If it is wrapping an inlined frame, it assumes that the
25586 inlined frame was contained within the next oldest frame,
25587 @code{eliding_frame}, which it fetches. It then creates and returns a
25588 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25589 elided frame, and the eliding frame.
25592 class ElidingInlineDecorator(FrameDecorator):
25594 def __init__(self, frame, elided_frames):
25595 super(ElidingInlineDecorator, self).__init__(frame)
25597 self.elided_frames = elided_frames
25600 return iter(self.elided_frames)
25603 This frame decorator overrides one function and returns the inlined
25604 frame in the @code{elided} method. As before it lets
25605 @code{FrameDecorator} do the rest of the work involved in printing
25606 this frame. This produces the following output.
25609 #0 0x004004e0 in bar () at inline.c:11
25610 #2 0x00400529 in main () at inline.c:25
25611 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25614 In that output, @code{max} which has been inlined into @code{main} is
25615 printed hierarchically. Another approach would be to combine the
25616 @code{function} method, and the @code{elided} method to both print a
25617 marker in the inlined frame, and also show the hierarchical
25620 @node Inferiors In Python
25621 @subsubsection Inferiors In Python
25622 @cindex inferiors in Python
25624 @findex gdb.Inferior
25625 Programs which are being run under @value{GDBN} are called inferiors
25626 (@pxref{Inferiors and Programs}). Python scripts can access
25627 information about and manipulate inferiors controlled by @value{GDBN}
25628 via objects of the @code{gdb.Inferior} class.
25630 The following inferior-related functions are available in the @code{gdb}
25633 @defun gdb.inferiors ()
25634 Return a tuple containing all inferior objects.
25637 @defun gdb.selected_inferior ()
25638 Return an object representing the current inferior.
25641 A @code{gdb.Inferior} object has the following attributes:
25643 @defvar Inferior.num
25644 ID of inferior, as assigned by GDB.
25647 @defvar Inferior.pid
25648 Process ID of the inferior, as assigned by the underlying operating
25652 @defvar Inferior.was_attached
25653 Boolean signaling whether the inferior was created using `attach', or
25654 started by @value{GDBN} itself.
25657 A @code{gdb.Inferior} object has the following methods:
25659 @defun Inferior.is_valid ()
25660 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25661 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25662 if the inferior no longer exists within @value{GDBN}. All other
25663 @code{gdb.Inferior} methods will throw an exception if it is invalid
25664 at the time the method is called.
25667 @defun Inferior.threads ()
25668 This method returns a tuple holding all the threads which are valid
25669 when it is called. If there are no valid threads, the method will
25670 return an empty tuple.
25673 @findex Inferior.read_memory
25674 @defun Inferior.read_memory (address, length)
25675 Read @var{length} bytes of memory from the inferior, starting at
25676 @var{address}. Returns a buffer object, which behaves much like an array
25677 or a string. It can be modified and given to the
25678 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25679 value is a @code{memoryview} object.
25682 @findex Inferior.write_memory
25683 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25684 Write the contents of @var{buffer} to the inferior, starting at
25685 @var{address}. The @var{buffer} parameter must be a Python object
25686 which supports the buffer protocol, i.e., a string, an array or the
25687 object returned from @code{Inferior.read_memory}. If given, @var{length}
25688 determines the number of bytes from @var{buffer} to be written.
25691 @findex gdb.search_memory
25692 @defun Inferior.search_memory (address, length, pattern)
25693 Search a region of the inferior memory starting at @var{address} with
25694 the given @var{length} using the search pattern supplied in
25695 @var{pattern}. The @var{pattern} parameter must be a Python object
25696 which supports the buffer protocol, i.e., a string, an array or the
25697 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25698 containing the address where the pattern was found, or @code{None} if
25699 the pattern could not be found.
25702 @node Events In Python
25703 @subsubsection Events In Python
25704 @cindex inferior events in Python
25706 @value{GDBN} provides a general event facility so that Python code can be
25707 notified of various state changes, particularly changes that occur in
25710 An @dfn{event} is just an object that describes some state change. The
25711 type of the object and its attributes will vary depending on the details
25712 of the change. All the existing events are described below.
25714 In order to be notified of an event, you must register an event handler
25715 with an @dfn{event registry}. An event registry is an object in the
25716 @code{gdb.events} module which dispatches particular events. A registry
25717 provides methods to register and unregister event handlers:
25719 @defun EventRegistry.connect (object)
25720 Add the given callable @var{object} to the registry. This object will be
25721 called when an event corresponding to this registry occurs.
25724 @defun EventRegistry.disconnect (object)
25725 Remove the given @var{object} from the registry. Once removed, the object
25726 will no longer receive notifications of events.
25729 Here is an example:
25732 def exit_handler (event):
25733 print "event type: exit"
25734 print "exit code: %d" % (event.exit_code)
25736 gdb.events.exited.connect (exit_handler)
25739 In the above example we connect our handler @code{exit_handler} to the
25740 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25741 called when the inferior exits. The argument @dfn{event} in this example is
25742 of type @code{gdb.ExitedEvent}. As you can see in the example the
25743 @code{ExitedEvent} object has an attribute which indicates the exit code of
25746 The following is a listing of the event registries that are available and
25747 details of the events they emit:
25752 Emits @code{gdb.ThreadEvent}.
25754 Some events can be thread specific when @value{GDBN} is running in non-stop
25755 mode. When represented in Python, these events all extend
25756 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25757 events which are emitted by this or other modules might extend this event.
25758 Examples of these events are @code{gdb.BreakpointEvent} and
25759 @code{gdb.ContinueEvent}.
25761 @defvar ThreadEvent.inferior_thread
25762 In non-stop mode this attribute will be set to the specific thread which was
25763 involved in the emitted event. Otherwise, it will be set to @code{None}.
25766 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25768 This event indicates that the inferior has been continued after a stop. For
25769 inherited attribute refer to @code{gdb.ThreadEvent} above.
25771 @item events.exited
25772 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25773 @code{events.ExitedEvent} has two attributes:
25774 @defvar ExitedEvent.exit_code
25775 An integer representing the exit code, if available, which the inferior
25776 has returned. (The exit code could be unavailable if, for example,
25777 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25778 the attribute does not exist.
25780 @defvar ExitedEvent inferior
25781 A reference to the inferior which triggered the @code{exited} event.
25785 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25787 Indicates that the inferior has stopped. All events emitted by this registry
25788 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25789 will indicate the stopped thread when @value{GDBN} is running in non-stop
25790 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25792 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25794 This event indicates that the inferior or one of its threads has received as
25795 signal. @code{gdb.SignalEvent} has the following attributes:
25797 @defvar SignalEvent.stop_signal
25798 A string representing the signal received by the inferior. A list of possible
25799 signal values can be obtained by running the command @code{info signals} in
25800 the @value{GDBN} command prompt.
25803 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25805 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25806 been hit, and has the following attributes:
25808 @defvar BreakpointEvent.breakpoints
25809 A sequence containing references to all the breakpoints (type
25810 @code{gdb.Breakpoint}) that were hit.
25811 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25813 @defvar BreakpointEvent.breakpoint
25814 A reference to the first breakpoint that was hit.
25815 This function is maintained for backward compatibility and is now deprecated
25816 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25819 @item events.new_objfile
25820 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25821 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25823 @defvar NewObjFileEvent.new_objfile
25824 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25825 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25830 @node Threads In Python
25831 @subsubsection Threads In Python
25832 @cindex threads in python
25834 @findex gdb.InferiorThread
25835 Python scripts can access information about, and manipulate inferior threads
25836 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25838 The following thread-related functions are available in the @code{gdb}
25841 @findex gdb.selected_thread
25842 @defun gdb.selected_thread ()
25843 This function returns the thread object for the selected thread. If there
25844 is no selected thread, this will return @code{None}.
25847 A @code{gdb.InferiorThread} object has the following attributes:
25849 @defvar InferiorThread.name
25850 The name of the thread. If the user specified a name using
25851 @code{thread name}, then this returns that name. Otherwise, if an
25852 OS-supplied name is available, then it is returned. Otherwise, this
25853 returns @code{None}.
25855 This attribute can be assigned to. The new value must be a string
25856 object, which sets the new name, or @code{None}, which removes any
25857 user-specified thread name.
25860 @defvar InferiorThread.num
25861 ID of the thread, as assigned by GDB.
25864 @defvar InferiorThread.ptid
25865 ID of the thread, as assigned by the operating system. This attribute is a
25866 tuple containing three integers. The first is the Process ID (PID); the second
25867 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25868 Either the LWPID or TID may be 0, which indicates that the operating system
25869 does not use that identifier.
25872 A @code{gdb.InferiorThread} object has the following methods:
25874 @defun InferiorThread.is_valid ()
25875 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25876 @code{False} if not. A @code{gdb.InferiorThread} object will become
25877 invalid if the thread exits, or the inferior that the thread belongs
25878 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25879 exception if it is invalid at the time the method is called.
25882 @defun InferiorThread.switch ()
25883 This changes @value{GDBN}'s currently selected thread to the one represented
25887 @defun InferiorThread.is_stopped ()
25888 Return a Boolean indicating whether the thread is stopped.
25891 @defun InferiorThread.is_running ()
25892 Return a Boolean indicating whether the thread is running.
25895 @defun InferiorThread.is_exited ()
25896 Return a Boolean indicating whether the thread is exited.
25899 @node Commands In Python
25900 @subsubsection Commands In Python
25902 @cindex commands in python
25903 @cindex python commands
25904 You can implement new @value{GDBN} CLI commands in Python. A CLI
25905 command is implemented using an instance of the @code{gdb.Command}
25906 class, most commonly using a subclass.
25908 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25909 The object initializer for @code{Command} registers the new command
25910 with @value{GDBN}. This initializer is normally invoked from the
25911 subclass' own @code{__init__} method.
25913 @var{name} is the name of the command. If @var{name} consists of
25914 multiple words, then the initial words are looked for as prefix
25915 commands. In this case, if one of the prefix commands does not exist,
25916 an exception is raised.
25918 There is no support for multi-line commands.
25920 @var{command_class} should be one of the @samp{COMMAND_} constants
25921 defined below. This argument tells @value{GDBN} how to categorize the
25922 new command in the help system.
25924 @var{completer_class} is an optional argument. If given, it should be
25925 one of the @samp{COMPLETE_} constants defined below. This argument
25926 tells @value{GDBN} how to perform completion for this command. If not
25927 given, @value{GDBN} will attempt to complete using the object's
25928 @code{complete} method (see below); if no such method is found, an
25929 error will occur when completion is attempted.
25931 @var{prefix} is an optional argument. If @code{True}, then the new
25932 command is a prefix command; sub-commands of this command may be
25935 The help text for the new command is taken from the Python
25936 documentation string for the command's class, if there is one. If no
25937 documentation string is provided, the default value ``This command is
25938 not documented.'' is used.
25941 @cindex don't repeat Python command
25942 @defun Command.dont_repeat ()
25943 By default, a @value{GDBN} command is repeated when the user enters a
25944 blank line at the command prompt. A command can suppress this
25945 behavior by invoking the @code{dont_repeat} method. This is similar
25946 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25949 @defun Command.invoke (argument, from_tty)
25950 This method is called by @value{GDBN} when this command is invoked.
25952 @var{argument} is a string. It is the argument to the command, after
25953 leading and trailing whitespace has been stripped.
25955 @var{from_tty} is a boolean argument. When true, this means that the
25956 command was entered by the user at the terminal; when false it means
25957 that the command came from elsewhere.
25959 If this method throws an exception, it is turned into a @value{GDBN}
25960 @code{error} call. Otherwise, the return value is ignored.
25962 @findex gdb.string_to_argv
25963 To break @var{argument} up into an argv-like string use
25964 @code{gdb.string_to_argv}. This function behaves identically to
25965 @value{GDBN}'s internal argument lexer @code{buildargv}.
25966 It is recommended to use this for consistency.
25967 Arguments are separated by spaces and may be quoted.
25971 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25972 ['1', '2 "3', '4 "5', "6 '7"]
25977 @cindex completion of Python commands
25978 @defun Command.complete (text, word)
25979 This method is called by @value{GDBN} when the user attempts
25980 completion on this command. All forms of completion are handled by
25981 this method, that is, the @key{TAB} and @key{M-?} key bindings
25982 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25985 The arguments @var{text} and @var{word} are both strings. @var{text}
25986 holds the complete command line up to the cursor's location.
25987 @var{word} holds the last word of the command line; this is computed
25988 using a word-breaking heuristic.
25990 The @code{complete} method can return several values:
25993 If the return value is a sequence, the contents of the sequence are
25994 used as the completions. It is up to @code{complete} to ensure that the
25995 contents actually do complete the word. A zero-length sequence is
25996 allowed, it means that there were no completions available. Only
25997 string elements of the sequence are used; other elements in the
25998 sequence are ignored.
26001 If the return value is one of the @samp{COMPLETE_} constants defined
26002 below, then the corresponding @value{GDBN}-internal completion
26003 function is invoked, and its result is used.
26006 All other results are treated as though there were no available
26011 When a new command is registered, it must be declared as a member of
26012 some general class of commands. This is used to classify top-level
26013 commands in the on-line help system; note that prefix commands are not
26014 listed under their own category but rather that of their top-level
26015 command. The available classifications are represented by constants
26016 defined in the @code{gdb} module:
26019 @findex COMMAND_NONE
26020 @findex gdb.COMMAND_NONE
26021 @item gdb.COMMAND_NONE
26022 The command does not belong to any particular class. A command in
26023 this category will not be displayed in any of the help categories.
26025 @findex COMMAND_RUNNING
26026 @findex gdb.COMMAND_RUNNING
26027 @item gdb.COMMAND_RUNNING
26028 The command is related to running the inferior. For example,
26029 @code{start}, @code{step}, and @code{continue} are in this category.
26030 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
26031 commands in this category.
26033 @findex COMMAND_DATA
26034 @findex gdb.COMMAND_DATA
26035 @item gdb.COMMAND_DATA
26036 The command is related to data or variables. For example,
26037 @code{call}, @code{find}, and @code{print} are in this category. Type
26038 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
26041 @findex COMMAND_STACK
26042 @findex gdb.COMMAND_STACK
26043 @item gdb.COMMAND_STACK
26044 The command has to do with manipulation of the stack. For example,
26045 @code{backtrace}, @code{frame}, and @code{return} are in this
26046 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
26047 list of commands in this category.
26049 @findex COMMAND_FILES
26050 @findex gdb.COMMAND_FILES
26051 @item gdb.COMMAND_FILES
26052 This class is used for file-related commands. For example,
26053 @code{file}, @code{list} and @code{section} are in this category.
26054 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
26055 commands in this category.
26057 @findex COMMAND_SUPPORT
26058 @findex gdb.COMMAND_SUPPORT
26059 @item gdb.COMMAND_SUPPORT
26060 This should be used for ``support facilities'', generally meaning
26061 things that are useful to the user when interacting with @value{GDBN},
26062 but not related to the state of the inferior. For example,
26063 @code{help}, @code{make}, and @code{shell} are in this category. Type
26064 @kbd{help support} at the @value{GDBN} prompt to see a list of
26065 commands in this category.
26067 @findex COMMAND_STATUS
26068 @findex gdb.COMMAND_STATUS
26069 @item gdb.COMMAND_STATUS
26070 The command is an @samp{info}-related command, that is, related to the
26071 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
26072 and @code{show} are in this category. Type @kbd{help status} at the
26073 @value{GDBN} prompt to see a list of commands in this category.
26075 @findex COMMAND_BREAKPOINTS
26076 @findex gdb.COMMAND_BREAKPOINTS
26077 @item gdb.COMMAND_BREAKPOINTS
26078 The command has to do with breakpoints. For example, @code{break},
26079 @code{clear}, and @code{delete} are in this category. Type @kbd{help
26080 breakpoints} at the @value{GDBN} prompt to see a list of commands in
26083 @findex COMMAND_TRACEPOINTS
26084 @findex gdb.COMMAND_TRACEPOINTS
26085 @item gdb.COMMAND_TRACEPOINTS
26086 The command has to do with tracepoints. For example, @code{trace},
26087 @code{actions}, and @code{tfind} are in this category. Type
26088 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
26089 commands in this category.
26091 @findex COMMAND_USER
26092 @findex gdb.COMMAND_USER
26093 @item gdb.COMMAND_USER
26094 The command is a general purpose command for the user, and typically
26095 does not fit in one of the other categories.
26096 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
26097 a list of commands in this category, as well as the list of gdb macros
26098 (@pxref{Sequences}).
26100 @findex COMMAND_OBSCURE
26101 @findex gdb.COMMAND_OBSCURE
26102 @item gdb.COMMAND_OBSCURE
26103 The command is only used in unusual circumstances, or is not of
26104 general interest to users. For example, @code{checkpoint},
26105 @code{fork}, and @code{stop} are in this category. Type @kbd{help
26106 obscure} at the @value{GDBN} prompt to see a list of commands in this
26109 @findex COMMAND_MAINTENANCE
26110 @findex gdb.COMMAND_MAINTENANCE
26111 @item gdb.COMMAND_MAINTENANCE
26112 The command is only useful to @value{GDBN} maintainers. The
26113 @code{maintenance} and @code{flushregs} commands are in this category.
26114 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
26115 commands in this category.
26118 A new command can use a predefined completion function, either by
26119 specifying it via an argument at initialization, or by returning it
26120 from the @code{complete} method. These predefined completion
26121 constants are all defined in the @code{gdb} module:
26124 @findex COMPLETE_NONE
26125 @findex gdb.COMPLETE_NONE
26126 @item gdb.COMPLETE_NONE
26127 This constant means that no completion should be done.
26129 @findex COMPLETE_FILENAME
26130 @findex gdb.COMPLETE_FILENAME
26131 @item gdb.COMPLETE_FILENAME
26132 This constant means that filename completion should be performed.
26134 @findex COMPLETE_LOCATION
26135 @findex gdb.COMPLETE_LOCATION
26136 @item gdb.COMPLETE_LOCATION
26137 This constant means that location completion should be done.
26138 @xref{Specify Location}.
26140 @findex COMPLETE_COMMAND
26141 @findex gdb.COMPLETE_COMMAND
26142 @item gdb.COMPLETE_COMMAND
26143 This constant means that completion should examine @value{GDBN}
26146 @findex COMPLETE_SYMBOL
26147 @findex gdb.COMPLETE_SYMBOL
26148 @item gdb.COMPLETE_SYMBOL
26149 This constant means that completion should be done using symbol names
26152 @findex COMPLETE_EXPRESSION
26153 @findex gdb.COMPLETE_EXPRESSION
26154 @item gdb.COMPLETE_EXPRESSION
26155 This constant means that completion should be done on expressions.
26156 Often this means completing on symbol names, but some language
26157 parsers also have support for completing on field names.
26160 The following code snippet shows how a trivial CLI command can be
26161 implemented in Python:
26164 class HelloWorld (gdb.Command):
26165 """Greet the whole world."""
26167 def __init__ (self):
26168 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
26170 def invoke (self, arg, from_tty):
26171 print "Hello, World!"
26176 The last line instantiates the class, and is necessary to trigger the
26177 registration of the command with @value{GDBN}. Depending on how the
26178 Python code is read into @value{GDBN}, you may need to import the
26179 @code{gdb} module explicitly.
26181 @node Parameters In Python
26182 @subsubsection Parameters In Python
26184 @cindex parameters in python
26185 @cindex python parameters
26186 @tindex gdb.Parameter
26188 You can implement new @value{GDBN} parameters using Python. A new
26189 parameter is implemented as an instance of the @code{gdb.Parameter}
26192 Parameters are exposed to the user via the @code{set} and
26193 @code{show} commands. @xref{Help}.
26195 There are many parameters that already exist and can be set in
26196 @value{GDBN}. Two examples are: @code{set follow fork} and
26197 @code{set charset}. Setting these parameters influences certain
26198 behavior in @value{GDBN}. Similarly, you can define parameters that
26199 can be used to influence behavior in custom Python scripts and commands.
26201 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
26202 The object initializer for @code{Parameter} registers the new
26203 parameter with @value{GDBN}. This initializer is normally invoked
26204 from the subclass' own @code{__init__} method.
26206 @var{name} is the name of the new parameter. If @var{name} consists
26207 of multiple words, then the initial words are looked for as prefix
26208 parameters. An example of this can be illustrated with the
26209 @code{set print} set of parameters. If @var{name} is
26210 @code{print foo}, then @code{print} will be searched as the prefix
26211 parameter. In this case the parameter can subsequently be accessed in
26212 @value{GDBN} as @code{set print foo}.
26214 If @var{name} consists of multiple words, and no prefix parameter group
26215 can be found, an exception is raised.
26217 @var{command-class} should be one of the @samp{COMMAND_} constants
26218 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
26219 categorize the new parameter in the help system.
26221 @var{parameter-class} should be one of the @samp{PARAM_} constants
26222 defined below. This argument tells @value{GDBN} the type of the new
26223 parameter; this information is used for input validation and
26226 If @var{parameter-class} is @code{PARAM_ENUM}, then
26227 @var{enum-sequence} must be a sequence of strings. These strings
26228 represent the possible values for the parameter.
26230 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
26231 of a fourth argument will cause an exception to be thrown.
26233 The help text for the new parameter is taken from the Python
26234 documentation string for the parameter's class, if there is one. If
26235 there is no documentation string, a default value is used.
26238 @defvar Parameter.set_doc
26239 If this attribute exists, and is a string, then its value is used as
26240 the help text for this parameter's @code{set} command. The value is
26241 examined when @code{Parameter.__init__} is invoked; subsequent changes
26245 @defvar Parameter.show_doc
26246 If this attribute exists, and is a string, then its value is used as
26247 the help text for this parameter's @code{show} command. The value is
26248 examined when @code{Parameter.__init__} is invoked; subsequent changes
26252 @defvar Parameter.value
26253 The @code{value} attribute holds the underlying value of the
26254 parameter. It can be read and assigned to just as any other
26255 attribute. @value{GDBN} does validation when assignments are made.
26258 There are two methods that should be implemented in any
26259 @code{Parameter} class. These are:
26261 @defun Parameter.get_set_string (self)
26262 @value{GDBN} will call this method when a @var{parameter}'s value has
26263 been changed via the @code{set} API (for example, @kbd{set foo off}).
26264 The @code{value} attribute has already been populated with the new
26265 value and may be used in output. This method must return a string.
26268 @defun Parameter.get_show_string (self, svalue)
26269 @value{GDBN} will call this method when a @var{parameter}'s
26270 @code{show} API has been invoked (for example, @kbd{show foo}). The
26271 argument @code{svalue} receives the string representation of the
26272 current value. This method must return a string.
26275 When a new parameter is defined, its type must be specified. The
26276 available types are represented by constants defined in the @code{gdb}
26280 @findex PARAM_BOOLEAN
26281 @findex gdb.PARAM_BOOLEAN
26282 @item gdb.PARAM_BOOLEAN
26283 The value is a plain boolean. The Python boolean values, @code{True}
26284 and @code{False} are the only valid values.
26286 @findex PARAM_AUTO_BOOLEAN
26287 @findex gdb.PARAM_AUTO_BOOLEAN
26288 @item gdb.PARAM_AUTO_BOOLEAN
26289 The value has three possible states: true, false, and @samp{auto}. In
26290 Python, true and false are represented using boolean constants, and
26291 @samp{auto} is represented using @code{None}.
26293 @findex PARAM_UINTEGER
26294 @findex gdb.PARAM_UINTEGER
26295 @item gdb.PARAM_UINTEGER
26296 The value is an unsigned integer. The value of 0 should be
26297 interpreted to mean ``unlimited''.
26299 @findex PARAM_INTEGER
26300 @findex gdb.PARAM_INTEGER
26301 @item gdb.PARAM_INTEGER
26302 The value is a signed integer. The value of 0 should be interpreted
26303 to mean ``unlimited''.
26305 @findex PARAM_STRING
26306 @findex gdb.PARAM_STRING
26307 @item gdb.PARAM_STRING
26308 The value is a string. When the user modifies the string, any escape
26309 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26310 translated into corresponding characters and encoded into the current
26313 @findex PARAM_STRING_NOESCAPE
26314 @findex gdb.PARAM_STRING_NOESCAPE
26315 @item gdb.PARAM_STRING_NOESCAPE
26316 The value is a string. When the user modifies the string, escapes are
26317 passed through untranslated.
26319 @findex PARAM_OPTIONAL_FILENAME
26320 @findex gdb.PARAM_OPTIONAL_FILENAME
26321 @item gdb.PARAM_OPTIONAL_FILENAME
26322 The value is a either a filename (a string), or @code{None}.
26324 @findex PARAM_FILENAME
26325 @findex gdb.PARAM_FILENAME
26326 @item gdb.PARAM_FILENAME
26327 The value is a filename. This is just like
26328 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26330 @findex PARAM_ZINTEGER
26331 @findex gdb.PARAM_ZINTEGER
26332 @item gdb.PARAM_ZINTEGER
26333 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26334 is interpreted as itself.
26337 @findex gdb.PARAM_ENUM
26338 @item gdb.PARAM_ENUM
26339 The value is a string, which must be one of a collection string
26340 constants provided when the parameter is created.
26343 @node Functions In Python
26344 @subsubsection Writing new convenience functions
26346 @cindex writing convenience functions
26347 @cindex convenience functions in python
26348 @cindex python convenience functions
26349 @tindex gdb.Function
26351 You can implement new convenience functions (@pxref{Convenience Vars})
26352 in Python. A convenience function is an instance of a subclass of the
26353 class @code{gdb.Function}.
26355 @defun Function.__init__ (name)
26356 The initializer for @code{Function} registers the new function with
26357 @value{GDBN}. The argument @var{name} is the name of the function,
26358 a string. The function will be visible to the user as a convenience
26359 variable of type @code{internal function}, whose name is the same as
26360 the given @var{name}.
26362 The documentation for the new function is taken from the documentation
26363 string for the new class.
26366 @defun Function.invoke (@var{*args})
26367 When a convenience function is evaluated, its arguments are converted
26368 to instances of @code{gdb.Value}, and then the function's
26369 @code{invoke} method is called. Note that @value{GDBN} does not
26370 predetermine the arity of convenience functions. Instead, all
26371 available arguments are passed to @code{invoke}, following the
26372 standard Python calling convention. In particular, a convenience
26373 function can have default values for parameters without ill effect.
26375 The return value of this method is used as its value in the enclosing
26376 expression. If an ordinary Python value is returned, it is converted
26377 to a @code{gdb.Value} following the usual rules.
26380 The following code snippet shows how a trivial convenience function can
26381 be implemented in Python:
26384 class Greet (gdb.Function):
26385 """Return string to greet someone.
26386 Takes a name as argument."""
26388 def __init__ (self):
26389 super (Greet, self).__init__ ("greet")
26391 def invoke (self, name):
26392 return "Hello, %s!" % name.string ()
26397 The last line instantiates the class, and is necessary to trigger the
26398 registration of the function with @value{GDBN}. Depending on how the
26399 Python code is read into @value{GDBN}, you may need to import the
26400 @code{gdb} module explicitly.
26402 Now you can use the function in an expression:
26405 (gdb) print $greet("Bob")
26409 @node Progspaces In Python
26410 @subsubsection Program Spaces In Python
26412 @cindex progspaces in python
26413 @tindex gdb.Progspace
26415 A program space, or @dfn{progspace}, represents a symbolic view
26416 of an address space.
26417 It consists of all of the objfiles of the program.
26418 @xref{Objfiles In Python}.
26419 @xref{Inferiors and Programs, program spaces}, for more details
26420 about program spaces.
26422 The following progspace-related functions are available in the
26425 @findex gdb.current_progspace
26426 @defun gdb.current_progspace ()
26427 This function returns the program space of the currently selected inferior.
26428 @xref{Inferiors and Programs}.
26431 @findex gdb.progspaces
26432 @defun gdb.progspaces ()
26433 Return a sequence of all the progspaces currently known to @value{GDBN}.
26436 Each progspace is represented by an instance of the @code{gdb.Progspace}
26439 @defvar Progspace.filename
26440 The file name of the progspace as a string.
26443 @defvar Progspace.pretty_printers
26444 The @code{pretty_printers} attribute is a list of functions. It is
26445 used to look up pretty-printers. A @code{Value} is passed to each
26446 function in order; if the function returns @code{None}, then the
26447 search continues. Otherwise, the return value should be an object
26448 which is used to format the value. @xref{Pretty Printing API}, for more
26452 @defvar Progspace.type_printers
26453 The @code{type_printers} attribute is a list of type printer objects.
26454 @xref{Type Printing API}, for more information.
26457 @defvar Progspace.frame_filters
26458 The @code{frame_filters} attribute is a dictionary of frame filter
26459 objects. @xref{Frame Filter API}, for more information.
26462 @node Objfiles In Python
26463 @subsubsection Objfiles In Python
26465 @cindex objfiles in python
26466 @tindex gdb.Objfile
26468 @value{GDBN} loads symbols for an inferior from various
26469 symbol-containing files (@pxref{Files}). These include the primary
26470 executable file, any shared libraries used by the inferior, and any
26471 separate debug info files (@pxref{Separate Debug Files}).
26472 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26474 The following objfile-related functions are available in the
26477 @findex gdb.current_objfile
26478 @defun gdb.current_objfile ()
26479 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26480 sets the ``current objfile'' to the corresponding objfile. This
26481 function returns the current objfile. If there is no current objfile,
26482 this function returns @code{None}.
26485 @findex gdb.objfiles
26486 @defun gdb.objfiles ()
26487 Return a sequence of all the objfiles current known to @value{GDBN}.
26488 @xref{Objfiles In Python}.
26491 Each objfile is represented by an instance of the @code{gdb.Objfile}
26494 @defvar Objfile.filename
26495 The file name of the objfile as a string.
26498 @defvar Objfile.pretty_printers
26499 The @code{pretty_printers} attribute is a list of functions. It is
26500 used to look up pretty-printers. A @code{Value} is passed to each
26501 function in order; if the function returns @code{None}, then the
26502 search continues. Otherwise, the return value should be an object
26503 which is used to format the value. @xref{Pretty Printing API}, for more
26507 @defvar Objfile.type_printers
26508 The @code{type_printers} attribute is a list of type printer objects.
26509 @xref{Type Printing API}, for more information.
26512 @defvar Objfile.frame_filters
26513 The @code{frame_filters} attribute is a dictionary of frame filter
26514 objects. @xref{Frame Filter API}, for more information.
26517 A @code{gdb.Objfile} object has the following methods:
26519 @defun Objfile.is_valid ()
26520 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26521 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26522 if the object file it refers to is not loaded in @value{GDBN} any
26523 longer. All other @code{gdb.Objfile} methods will throw an exception
26524 if it is invalid at the time the method is called.
26527 @node Frames In Python
26528 @subsubsection Accessing inferior stack frames from Python.
26530 @cindex frames in python
26531 When the debugged program stops, @value{GDBN} is able to analyze its call
26532 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26533 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26534 while its corresponding frame exists in the inferior's stack. If you try
26535 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26536 exception (@pxref{Exception Handling}).
26538 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26542 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26546 The following frame-related functions are available in the @code{gdb} module:
26548 @findex gdb.selected_frame
26549 @defun gdb.selected_frame ()
26550 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26553 @findex gdb.newest_frame
26554 @defun gdb.newest_frame ()
26555 Return the newest frame object for the selected thread.
26558 @defun gdb.frame_stop_reason_string (reason)
26559 Return a string explaining the reason why @value{GDBN} stopped unwinding
26560 frames, as expressed by the given @var{reason} code (an integer, see the
26561 @code{unwind_stop_reason} method further down in this section).
26564 A @code{gdb.Frame} object has the following methods:
26566 @defun Frame.is_valid ()
26567 Returns true if the @code{gdb.Frame} object is valid, false if not.
26568 A frame object can become invalid if the frame it refers to doesn't
26569 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26570 an exception if it is invalid at the time the method is called.
26573 @defun Frame.name ()
26574 Returns the function name of the frame, or @code{None} if it can't be
26578 @defun Frame.architecture ()
26579 Returns the @code{gdb.Architecture} object corresponding to the frame's
26580 architecture. @xref{Architectures In Python}.
26583 @defun Frame.type ()
26584 Returns the type of the frame. The value can be one of:
26586 @item gdb.NORMAL_FRAME
26587 An ordinary stack frame.
26589 @item gdb.DUMMY_FRAME
26590 A fake stack frame that was created by @value{GDBN} when performing an
26591 inferior function call.
26593 @item gdb.INLINE_FRAME
26594 A frame representing an inlined function. The function was inlined
26595 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26597 @item gdb.TAILCALL_FRAME
26598 A frame representing a tail call. @xref{Tail Call Frames}.
26600 @item gdb.SIGTRAMP_FRAME
26601 A signal trampoline frame. This is the frame created by the OS when
26602 it calls into a signal handler.
26604 @item gdb.ARCH_FRAME
26605 A fake stack frame representing a cross-architecture call.
26607 @item gdb.SENTINEL_FRAME
26608 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26613 @defun Frame.unwind_stop_reason ()
26614 Return an integer representing the reason why it's not possible to find
26615 more frames toward the outermost frame. Use
26616 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26617 function to a string. The value can be one of:
26620 @item gdb.FRAME_UNWIND_NO_REASON
26621 No particular reason (older frames should be available).
26623 @item gdb.FRAME_UNWIND_NULL_ID
26624 The previous frame's analyzer returns an invalid result. This is no
26625 longer used by @value{GDBN}, and is kept only for backward
26628 @item gdb.FRAME_UNWIND_OUTERMOST
26629 This frame is the outermost.
26631 @item gdb.FRAME_UNWIND_UNAVAILABLE
26632 Cannot unwind further, because that would require knowing the
26633 values of registers or memory that have not been collected.
26635 @item gdb.FRAME_UNWIND_INNER_ID
26636 This frame ID looks like it ought to belong to a NEXT frame,
26637 but we got it for a PREV frame. Normally, this is a sign of
26638 unwinder failure. It could also indicate stack corruption.
26640 @item gdb.FRAME_UNWIND_SAME_ID
26641 This frame has the same ID as the previous one. That means
26642 that unwinding further would almost certainly give us another
26643 frame with exactly the same ID, so break the chain. Normally,
26644 this is a sign of unwinder failure. It could also indicate
26647 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26648 The frame unwinder did not find any saved PC, but we needed
26649 one to unwind further.
26651 @item gdb.FRAME_UNWIND_FIRST_ERROR
26652 Any stop reason greater or equal to this value indicates some kind
26653 of error. This special value facilitates writing code that tests
26654 for errors in unwinding in a way that will work correctly even if
26655 the list of the other values is modified in future @value{GDBN}
26656 versions. Using it, you could write:
26658 reason = gdb.selected_frame().unwind_stop_reason ()
26659 reason_str = gdb.frame_stop_reason_string (reason)
26660 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26661 print "An error occured: %s" % reason_str
26668 Returns the frame's resume address.
26671 @defun Frame.block ()
26672 Return the frame's code block. @xref{Blocks In Python}.
26675 @defun Frame.function ()
26676 Return the symbol for the function corresponding to this frame.
26677 @xref{Symbols In Python}.
26680 @defun Frame.older ()
26681 Return the frame that called this frame.
26684 @defun Frame.newer ()
26685 Return the frame called by this frame.
26688 @defun Frame.find_sal ()
26689 Return the frame's symtab and line object.
26690 @xref{Symbol Tables In Python}.
26693 @defun Frame.read_var (variable @r{[}, block@r{]})
26694 Return the value of @var{variable} in this frame. If the optional
26695 argument @var{block} is provided, search for the variable from that
26696 block; otherwise start at the frame's current block (which is
26697 determined by the frame's current program counter). @var{variable}
26698 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26699 @code{gdb.Block} object.
26702 @defun Frame.select ()
26703 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26707 @node Blocks In Python
26708 @subsubsection Accessing blocks from Python.
26710 @cindex blocks in python
26713 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26714 roughly to a scope in the source code. Blocks are organized
26715 hierarchically, and are represented individually in Python as a
26716 @code{gdb.Block}. Blocks rely on debugging information being
26719 A frame has a block. Please see @ref{Frames In Python}, for a more
26720 in-depth discussion of frames.
26722 The outermost block is known as the @dfn{global block}. The global
26723 block typically holds public global variables and functions.
26725 The block nested just inside the global block is the @dfn{static
26726 block}. The static block typically holds file-scoped variables and
26729 @value{GDBN} provides a method to get a block's superblock, but there
26730 is currently no way to examine the sub-blocks of a block, or to
26731 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26734 Here is a short example that should help explain blocks:
26737 /* This is in the global block. */
26740 /* This is in the static block. */
26741 static int file_scope;
26743 /* 'function' is in the global block, and 'argument' is
26744 in a block nested inside of 'function'. */
26745 int function (int argument)
26747 /* 'local' is in a block inside 'function'. It may or may
26748 not be in the same block as 'argument'. */
26752 /* 'inner' is in a block whose superblock is the one holding
26756 /* If this call is expanded by the compiler, you may see
26757 a nested block here whose function is 'inline_function'
26758 and whose superblock is the one holding 'inner'. */
26759 inline_function ();
26764 A @code{gdb.Block} is iterable. The iterator returns the symbols
26765 (@pxref{Symbols In Python}) local to the block. Python programs
26766 should not assume that a specific block object will always contain a
26767 given symbol, since changes in @value{GDBN} features and
26768 infrastructure may cause symbols move across blocks in a symbol
26771 The following block-related functions are available in the @code{gdb}
26774 @findex gdb.block_for_pc
26775 @defun gdb.block_for_pc (pc)
26776 Return the innermost @code{gdb.Block} containing the given @var{pc}
26777 value. If the block cannot be found for the @var{pc} value specified,
26778 the function will return @code{None}.
26781 A @code{gdb.Block} object has the following methods:
26783 @defun Block.is_valid ()
26784 Returns @code{True} if the @code{gdb.Block} object is valid,
26785 @code{False} if not. A block object can become invalid if the block it
26786 refers to doesn't exist anymore in the inferior. All other
26787 @code{gdb.Block} methods will throw an exception if it is invalid at
26788 the time the method is called. The block's validity is also checked
26789 during iteration over symbols of the block.
26792 A @code{gdb.Block} object has the following attributes:
26794 @defvar Block.start
26795 The start address of the block. This attribute is not writable.
26799 The end address of the block. This attribute is not writable.
26802 @defvar Block.function
26803 The name of the block represented as a @code{gdb.Symbol}. If the
26804 block is not named, then this attribute holds @code{None}. This
26805 attribute is not writable.
26807 For ordinary function blocks, the superblock is the static block.
26808 However, you should note that it is possible for a function block to
26809 have a superblock that is not the static block -- for instance this
26810 happens for an inlined function.
26813 @defvar Block.superblock
26814 The block containing this block. If this parent block does not exist,
26815 this attribute holds @code{None}. This attribute is not writable.
26818 @defvar Block.global_block
26819 The global block associated with this block. This attribute is not
26823 @defvar Block.static_block
26824 The static block associated with this block. This attribute is not
26828 @defvar Block.is_global
26829 @code{True} if the @code{gdb.Block} object is a global block,
26830 @code{False} if not. This attribute is not
26834 @defvar Block.is_static
26835 @code{True} if the @code{gdb.Block} object is a static block,
26836 @code{False} if not. This attribute is not writable.
26839 @node Symbols In Python
26840 @subsubsection Python representation of Symbols.
26842 @cindex symbols in python
26845 @value{GDBN} represents every variable, function and type as an
26846 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26847 Similarly, Python represents these symbols in @value{GDBN} with the
26848 @code{gdb.Symbol} object.
26850 The following symbol-related functions are available in the @code{gdb}
26853 @findex gdb.lookup_symbol
26854 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26855 This function searches for a symbol by name. The search scope can be
26856 restricted to the parameters defined in the optional domain and block
26859 @var{name} is the name of the symbol. It must be a string. The
26860 optional @var{block} argument restricts the search to symbols visible
26861 in that @var{block}. The @var{block} argument must be a
26862 @code{gdb.Block} object. If omitted, the block for the current frame
26863 is used. The optional @var{domain} argument restricts
26864 the search to the domain type. The @var{domain} argument must be a
26865 domain constant defined in the @code{gdb} module and described later
26868 The result is a tuple of two elements.
26869 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26871 If the symbol is found, the second element is @code{True} if the symbol
26872 is a field of a method's object (e.g., @code{this} in C@t{++}),
26873 otherwise it is @code{False}.
26874 If the symbol is not found, the second element is @code{False}.
26877 @findex gdb.lookup_global_symbol
26878 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26879 This function searches for a global symbol by name.
26880 The search scope can be restricted to by the domain argument.
26882 @var{name} is the name of the symbol. It must be a string.
26883 The optional @var{domain} argument restricts the search to the domain type.
26884 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26885 module and described later in this chapter.
26887 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26891 A @code{gdb.Symbol} object has the following attributes:
26893 @defvar Symbol.type
26894 The type of the symbol or @code{None} if no type is recorded.
26895 This attribute is represented as a @code{gdb.Type} object.
26896 @xref{Types In Python}. This attribute is not writable.
26899 @defvar Symbol.symtab
26900 The symbol table in which the symbol appears. This attribute is
26901 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26902 Python}. This attribute is not writable.
26905 @defvar Symbol.line
26906 The line number in the source code at which the symbol was defined.
26907 This is an integer.
26910 @defvar Symbol.name
26911 The name of the symbol as a string. This attribute is not writable.
26914 @defvar Symbol.linkage_name
26915 The name of the symbol, as used by the linker (i.e., may be mangled).
26916 This attribute is not writable.
26919 @defvar Symbol.print_name
26920 The name of the symbol in a form suitable for output. This is either
26921 @code{name} or @code{linkage_name}, depending on whether the user
26922 asked @value{GDBN} to display demangled or mangled names.
26925 @defvar Symbol.addr_class
26926 The address class of the symbol. This classifies how to find the value
26927 of a symbol. Each address class is a constant defined in the
26928 @code{gdb} module and described later in this chapter.
26931 @defvar Symbol.needs_frame
26932 This is @code{True} if evaluating this symbol's value requires a frame
26933 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26934 local variables will require a frame, but other symbols will not.
26937 @defvar Symbol.is_argument
26938 @code{True} if the symbol is an argument of a function.
26941 @defvar Symbol.is_constant
26942 @code{True} if the symbol is a constant.
26945 @defvar Symbol.is_function
26946 @code{True} if the symbol is a function or a method.
26949 @defvar Symbol.is_variable
26950 @code{True} if the symbol is a variable.
26953 A @code{gdb.Symbol} object has the following methods:
26955 @defun Symbol.is_valid ()
26956 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26957 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26958 the symbol it refers to does not exist in @value{GDBN} any longer.
26959 All other @code{gdb.Symbol} methods will throw an exception if it is
26960 invalid at the time the method is called.
26963 @defun Symbol.value (@r{[}frame@r{]})
26964 Compute the value of the symbol, as a @code{gdb.Value}. For
26965 functions, this computes the address of the function, cast to the
26966 appropriate type. If the symbol requires a frame in order to compute
26967 its value, then @var{frame} must be given. If @var{frame} is not
26968 given, or if @var{frame} is invalid, then this method will throw an
26972 The available domain categories in @code{gdb.Symbol} are represented
26973 as constants in the @code{gdb} module:
26976 @findex SYMBOL_UNDEF_DOMAIN
26977 @findex gdb.SYMBOL_UNDEF_DOMAIN
26978 @item gdb.SYMBOL_UNDEF_DOMAIN
26979 This is used when a domain has not been discovered or none of the
26980 following domains apply. This usually indicates an error either
26981 in the symbol information or in @value{GDBN}'s handling of symbols.
26982 @findex SYMBOL_VAR_DOMAIN
26983 @findex gdb.SYMBOL_VAR_DOMAIN
26984 @item gdb.SYMBOL_VAR_DOMAIN
26985 This domain contains variables, function names, typedef names and enum
26987 @findex SYMBOL_STRUCT_DOMAIN
26988 @findex gdb.SYMBOL_STRUCT_DOMAIN
26989 @item gdb.SYMBOL_STRUCT_DOMAIN
26990 This domain holds struct, union and enum type names.
26991 @findex SYMBOL_LABEL_DOMAIN
26992 @findex gdb.SYMBOL_LABEL_DOMAIN
26993 @item gdb.SYMBOL_LABEL_DOMAIN
26994 This domain contains names of labels (for gotos).
26995 @findex SYMBOL_VARIABLES_DOMAIN
26996 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26997 @item gdb.SYMBOL_VARIABLES_DOMAIN
26998 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26999 contains everything minus functions and types.
27000 @findex SYMBOL_FUNCTIONS_DOMAIN
27001 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
27002 @item gdb.SYMBOL_FUNCTION_DOMAIN
27003 This domain contains all functions.
27004 @findex SYMBOL_TYPES_DOMAIN
27005 @findex gdb.SYMBOL_TYPES_DOMAIN
27006 @item gdb.SYMBOL_TYPES_DOMAIN
27007 This domain contains all types.
27010 The available address class categories in @code{gdb.Symbol} are represented
27011 as constants in the @code{gdb} module:
27014 @findex SYMBOL_LOC_UNDEF
27015 @findex gdb.SYMBOL_LOC_UNDEF
27016 @item gdb.SYMBOL_LOC_UNDEF
27017 If this is returned by address class, it indicates an error either in
27018 the symbol information or in @value{GDBN}'s handling of symbols.
27019 @findex SYMBOL_LOC_CONST
27020 @findex gdb.SYMBOL_LOC_CONST
27021 @item gdb.SYMBOL_LOC_CONST
27022 Value is constant int.
27023 @findex SYMBOL_LOC_STATIC
27024 @findex gdb.SYMBOL_LOC_STATIC
27025 @item gdb.SYMBOL_LOC_STATIC
27026 Value is at a fixed address.
27027 @findex SYMBOL_LOC_REGISTER
27028 @findex gdb.SYMBOL_LOC_REGISTER
27029 @item gdb.SYMBOL_LOC_REGISTER
27030 Value is in a register.
27031 @findex SYMBOL_LOC_ARG
27032 @findex gdb.SYMBOL_LOC_ARG
27033 @item gdb.SYMBOL_LOC_ARG
27034 Value is an argument. This value is at the offset stored within the
27035 symbol inside the frame's argument list.
27036 @findex SYMBOL_LOC_REF_ARG
27037 @findex gdb.SYMBOL_LOC_REF_ARG
27038 @item gdb.SYMBOL_LOC_REF_ARG
27039 Value address is stored in the frame's argument list. Just like
27040 @code{LOC_ARG} except that the value's address is stored at the
27041 offset, not the value itself.
27042 @findex SYMBOL_LOC_REGPARM_ADDR
27043 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
27044 @item gdb.SYMBOL_LOC_REGPARM_ADDR
27045 Value is a specified register. Just like @code{LOC_REGISTER} except
27046 the register holds the address of the argument instead of the argument
27048 @findex SYMBOL_LOC_LOCAL
27049 @findex gdb.SYMBOL_LOC_LOCAL
27050 @item gdb.SYMBOL_LOC_LOCAL
27051 Value is a local variable.
27052 @findex SYMBOL_LOC_TYPEDEF
27053 @findex gdb.SYMBOL_LOC_TYPEDEF
27054 @item gdb.SYMBOL_LOC_TYPEDEF
27055 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
27057 @findex SYMBOL_LOC_BLOCK
27058 @findex gdb.SYMBOL_LOC_BLOCK
27059 @item gdb.SYMBOL_LOC_BLOCK
27061 @findex SYMBOL_LOC_CONST_BYTES
27062 @findex gdb.SYMBOL_LOC_CONST_BYTES
27063 @item gdb.SYMBOL_LOC_CONST_BYTES
27064 Value is a byte-sequence.
27065 @findex SYMBOL_LOC_UNRESOLVED
27066 @findex gdb.SYMBOL_LOC_UNRESOLVED
27067 @item gdb.SYMBOL_LOC_UNRESOLVED
27068 Value is at a fixed address, but the address of the variable has to be
27069 determined from the minimal symbol table whenever the variable is
27071 @findex SYMBOL_LOC_OPTIMIZED_OUT
27072 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
27073 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
27074 The value does not actually exist in the program.
27075 @findex SYMBOL_LOC_COMPUTED
27076 @findex gdb.SYMBOL_LOC_COMPUTED
27077 @item gdb.SYMBOL_LOC_COMPUTED
27078 The value's address is a computed location.
27081 @node Symbol Tables In Python
27082 @subsubsection Symbol table representation in Python.
27084 @cindex symbol tables in python
27086 @tindex gdb.Symtab_and_line
27088 Access to symbol table data maintained by @value{GDBN} on the inferior
27089 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
27090 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
27091 from the @code{find_sal} method in @code{gdb.Frame} object.
27092 @xref{Frames In Python}.
27094 For more information on @value{GDBN}'s symbol table management, see
27095 @ref{Symbols, ,Examining the Symbol Table}, for more information.
27097 A @code{gdb.Symtab_and_line} object has the following attributes:
27099 @defvar Symtab_and_line.symtab
27100 The symbol table object (@code{gdb.Symtab}) for this frame.
27101 This attribute is not writable.
27104 @defvar Symtab_and_line.pc
27105 Indicates the start of the address range occupied by code for the
27106 current source line. This attribute is not writable.
27109 @defvar Symtab_and_line.last
27110 Indicates the end of the address range occupied by code for the current
27111 source line. This attribute is not writable.
27114 @defvar Symtab_and_line.line
27115 Indicates the current line number for this object. This
27116 attribute is not writable.
27119 A @code{gdb.Symtab_and_line} object has the following methods:
27121 @defun Symtab_and_line.is_valid ()
27122 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
27123 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
27124 invalid if the Symbol table and line object it refers to does not
27125 exist in @value{GDBN} any longer. All other
27126 @code{gdb.Symtab_and_line} methods will throw an exception if it is
27127 invalid at the time the method is called.
27130 A @code{gdb.Symtab} object has the following attributes:
27132 @defvar Symtab.filename
27133 The symbol table's source filename. This attribute is not writable.
27136 @defvar Symtab.objfile
27137 The symbol table's backing object file. @xref{Objfiles In Python}.
27138 This attribute is not writable.
27141 A @code{gdb.Symtab} object has the following methods:
27143 @defun Symtab.is_valid ()
27144 Returns @code{True} if the @code{gdb.Symtab} object is valid,
27145 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
27146 the symbol table it refers to does not exist in @value{GDBN} any
27147 longer. All other @code{gdb.Symtab} methods will throw an exception
27148 if it is invalid at the time the method is called.
27151 @defun Symtab.fullname ()
27152 Return the symbol table's source absolute file name.
27155 @defun Symtab.global_block ()
27156 Return the global block of the underlying symbol table.
27157 @xref{Blocks In Python}.
27160 @defun Symtab.static_block ()
27161 Return the static block of the underlying symbol table.
27162 @xref{Blocks In Python}.
27165 @defun Symtab.linetable ()
27166 Return the line table associated with the symbol table.
27167 @xref{Line Tables In Python}.
27170 @node Line Tables In Python
27171 @subsubsection Manipulating line tables using Python
27173 @cindex line tables in python
27174 @tindex gdb.LineTable
27176 Python code can request and inspect line table information from a
27177 symbol table that is loaded in @value{GDBN}. A line table is a
27178 mapping of source lines to their executable locations in memory. To
27179 acquire the line table information for a particular symbol table, use
27180 the @code{linetable} function (@pxref{Symbol Tables In Python}).
27182 A @code{gdb.LineTable} is iterable. The iterator returns
27183 @code{LineTableEntry} objects that correspond to the source line and
27184 address for each line table entry. @code{LineTableEntry} objects have
27185 the following attributes:
27187 @defvar LineTableEntry.line
27188 The source line number for this line table entry. This number
27189 corresponds to the actual line of source. This attribute is not
27193 @defvar LineTableEntry.pc
27194 The address that is associated with the line table entry where the
27195 executable code for that source line resides in memory. This
27196 attribute is not writable.
27199 As there can be multiple addresses for a single source line, you may
27200 receive multiple @code{LineTableEntry} objects with matching
27201 @code{line} attributes, but with different @code{pc} attributes. The
27202 iterator is sorted in ascending @code{pc} order. Here is a small
27203 example illustrating iterating over a line table.
27206 symtab = gdb.selected_frame().find_sal().symtab
27207 linetable = symtab.linetable()
27208 for line in linetable:
27209 print "Line: "+str(line.line)+" Address: "+hex(line.pc)
27212 This will have the following output:
27215 Line: 33 Address: 0x4005c8L
27216 Line: 37 Address: 0x4005caL
27217 Line: 39 Address: 0x4005d2L
27218 Line: 40 Address: 0x4005f8L
27219 Line: 42 Address: 0x4005ffL
27220 Line: 44 Address: 0x400608L
27221 Line: 42 Address: 0x40060cL
27222 Line: 45 Address: 0x400615L
27225 In addition to being able to iterate over a @code{LineTable}, it also
27226 has the following direct access methods:
27228 @defun LineTable.line (line)
27229 Return a Python @code{Tuple} of @code{LineTableEntry} objects for any
27230 entries in the line table for the given @var{line}. @var{line} refers
27231 to the source code line. If there are no entries for that source code
27232 @var{line}, the Python @code{None} is returned.
27235 @defun LineTable.has_line (line)
27236 Return a Python @code{Boolean} indicating whether there is an entry in
27237 the line table for this source line. Return @code{True} if an entry
27238 is found, or @code{False} if not.
27241 @defun LineTable.source_lines ()
27242 Return a Python @code{List} of the source line numbers in the symbol
27243 table. Only lines with executable code locations are returned. The
27244 contents of the @code{List} will just be the source line entries
27245 represented as Python @code{Long} values.
27248 @node Breakpoints In Python
27249 @subsubsection Manipulating breakpoints using Python
27251 @cindex breakpoints in python
27252 @tindex gdb.Breakpoint
27254 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
27257 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal @r{[},temporary@r{]]]]})
27258 Create a new breakpoint. @var{spec} is a string naming the location
27259 of the breakpoint, or an expression that defines a watchpoint. The
27260 contents can be any location recognized by the @code{break} command,
27261 or in the case of a watchpoint, by the @code{watch} command. The
27262 optional @var{type} denotes the breakpoint to create from the types
27263 defined later in this chapter. This argument can be either:
27264 @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
27265 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal}
27266 argument allows the breakpoint to become invisible to the user. The
27267 breakpoint will neither be reported when created, nor will it be
27268 listed in the output from @code{info breakpoints} (but will be listed
27269 with the @code{maint info breakpoints} command). The optional
27270 @var{temporary} argument makes the breakpoint a temporary breakpoint.
27271 Temporary breakpoints are deleted after they have been hit. Any
27272 further access to the Python breakpoint after it has been hit will
27273 result in a runtime error (as that breakpoint has now been
27274 automatically deleted). The optional @var{wp_class} argument defines
27275 the class of watchpoint to create, if @var{type} is
27276 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it
27277 is assumed to be a @code{gdb.WP_WRITE} class.
27280 @defun Breakpoint.stop (self)
27281 The @code{gdb.Breakpoint} class can be sub-classed and, in
27282 particular, you may choose to implement the @code{stop} method.
27283 If this method is defined in a sub-class of @code{gdb.Breakpoint},
27284 it will be called when the inferior reaches any location of a
27285 breakpoint which instantiates that sub-class. If the method returns
27286 @code{True}, the inferior will be stopped at the location of the
27287 breakpoint, otherwise the inferior will continue.
27289 If there are multiple breakpoints at the same location with a
27290 @code{stop} method, each one will be called regardless of the
27291 return status of the previous. This ensures that all @code{stop}
27292 methods have a chance to execute at that location. In this scenario
27293 if one of the methods returns @code{True} but the others return
27294 @code{False}, the inferior will still be stopped.
27296 You should not alter the execution state of the inferior (i.e.@:, step,
27297 next, etc.), alter the current frame context (i.e.@:, change the current
27298 active frame), or alter, add or delete any breakpoint. As a general
27299 rule, you should not alter any data within @value{GDBN} or the inferior
27302 Example @code{stop} implementation:
27305 class MyBreakpoint (gdb.Breakpoint):
27307 inf_val = gdb.parse_and_eval("foo")
27314 The available watchpoint types represented by constants are defined in the
27319 @findex gdb.WP_READ
27321 Read only watchpoint.
27324 @findex gdb.WP_WRITE
27326 Write only watchpoint.
27329 @findex gdb.WP_ACCESS
27330 @item gdb.WP_ACCESS
27331 Read/Write watchpoint.
27334 @defun Breakpoint.is_valid ()
27335 Return @code{True} if this @code{Breakpoint} object is valid,
27336 @code{False} otherwise. A @code{Breakpoint} object can become invalid
27337 if the user deletes the breakpoint. In this case, the object still
27338 exists, but the underlying breakpoint does not. In the cases of
27339 watchpoint scope, the watchpoint remains valid even if execution of the
27340 inferior leaves the scope of that watchpoint.
27343 @defun Breakpoint.delete
27344 Permanently deletes the @value{GDBN} breakpoint. This also
27345 invalidates the Python @code{Breakpoint} object. Any further access
27346 to this object's attributes or methods will raise an error.
27349 @defvar Breakpoint.enabled
27350 This attribute is @code{True} if the breakpoint is enabled, and
27351 @code{False} otherwise. This attribute is writable.
27354 @defvar Breakpoint.silent
27355 This attribute is @code{True} if the breakpoint is silent, and
27356 @code{False} otherwise. This attribute is writable.
27358 Note that a breakpoint can also be silent if it has commands and the
27359 first command is @code{silent}. This is not reported by the
27360 @code{silent} attribute.
27363 @defvar Breakpoint.thread
27364 If the breakpoint is thread-specific, this attribute holds the thread
27365 id. If the breakpoint is not thread-specific, this attribute is
27366 @code{None}. This attribute is writable.
27369 @defvar Breakpoint.task
27370 If the breakpoint is Ada task-specific, this attribute holds the Ada task
27371 id. If the breakpoint is not task-specific (or the underlying
27372 language is not Ada), this attribute is @code{None}. This attribute
27376 @defvar Breakpoint.ignore_count
27377 This attribute holds the ignore count for the breakpoint, an integer.
27378 This attribute is writable.
27381 @defvar Breakpoint.number
27382 This attribute holds the breakpoint's number --- the identifier used by
27383 the user to manipulate the breakpoint. This attribute is not writable.
27386 @defvar Breakpoint.type
27387 This attribute holds the breakpoint's type --- the identifier used to
27388 determine the actual breakpoint type or use-case. This attribute is not
27392 @defvar Breakpoint.visible
27393 This attribute tells whether the breakpoint is visible to the user
27394 when set, or when the @samp{info breakpoints} command is run. This
27395 attribute is not writable.
27398 @defvar Breakpoint.temporary
27399 This attribute indicates whether the breakpoint was created as a
27400 temporary breakpoint. Temporary breakpoints are automatically deleted
27401 after that breakpoint has been hit. Access to this attribute, and all
27402 other attributes and functions other than the @code{is_valid}
27403 function, will result in an error after the breakpoint has been hit
27404 (as it has been automatically deleted). This attribute is not
27408 The available types are represented by constants defined in the @code{gdb}
27412 @findex BP_BREAKPOINT
27413 @findex gdb.BP_BREAKPOINT
27414 @item gdb.BP_BREAKPOINT
27415 Normal code breakpoint.
27417 @findex BP_WATCHPOINT
27418 @findex gdb.BP_WATCHPOINT
27419 @item gdb.BP_WATCHPOINT
27420 Watchpoint breakpoint.
27422 @findex BP_HARDWARE_WATCHPOINT
27423 @findex gdb.BP_HARDWARE_WATCHPOINT
27424 @item gdb.BP_HARDWARE_WATCHPOINT
27425 Hardware assisted watchpoint.
27427 @findex BP_READ_WATCHPOINT
27428 @findex gdb.BP_READ_WATCHPOINT
27429 @item gdb.BP_READ_WATCHPOINT
27430 Hardware assisted read watchpoint.
27432 @findex BP_ACCESS_WATCHPOINT
27433 @findex gdb.BP_ACCESS_WATCHPOINT
27434 @item gdb.BP_ACCESS_WATCHPOINT
27435 Hardware assisted access watchpoint.
27438 @defvar Breakpoint.hit_count
27439 This attribute holds the hit count for the breakpoint, an integer.
27440 This attribute is writable, but currently it can only be set to zero.
27443 @defvar Breakpoint.location
27444 This attribute holds the location of the breakpoint, as specified by
27445 the user. It is a string. If the breakpoint does not have a location
27446 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27447 attribute is not writable.
27450 @defvar Breakpoint.expression
27451 This attribute holds a breakpoint expression, as specified by
27452 the user. It is a string. If the breakpoint does not have an
27453 expression (the breakpoint is not a watchpoint) the attribute's value
27454 is @code{None}. This attribute is not writable.
27457 @defvar Breakpoint.condition
27458 This attribute holds the condition of the breakpoint, as specified by
27459 the user. It is a string. If there is no condition, this attribute's
27460 value is @code{None}. This attribute is writable.
27463 @defvar Breakpoint.commands
27464 This attribute holds the commands attached to the breakpoint. If
27465 there are commands, this attribute's value is a string holding all the
27466 commands, separated by newlines. If there are no commands, this
27467 attribute is @code{None}. This attribute is not writable.
27470 @node Finish Breakpoints in Python
27471 @subsubsection Finish Breakpoints
27473 @cindex python finish breakpoints
27474 @tindex gdb.FinishBreakpoint
27476 A finish breakpoint is a temporary breakpoint set at the return address of
27477 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27478 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27479 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27480 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27481 Finish breakpoints are thread specific and must be create with the right
27484 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27485 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27486 object @var{frame}. If @var{frame} is not provided, this defaults to the
27487 newest frame. The optional @var{internal} argument allows the breakpoint to
27488 become invisible to the user. @xref{Breakpoints In Python}, for further
27489 details about this argument.
27492 @defun FinishBreakpoint.out_of_scope (self)
27493 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27494 @code{return} command, @dots{}), a function may not properly terminate, and
27495 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27496 situation, the @code{out_of_scope} callback will be triggered.
27498 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27502 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27504 print "normal finish"
27507 def out_of_scope ():
27508 print "abnormal finish"
27512 @defvar FinishBreakpoint.return_value
27513 When @value{GDBN} is stopped at a finish breakpoint and the frame
27514 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27515 attribute will contain a @code{gdb.Value} object corresponding to the return
27516 value of the function. The value will be @code{None} if the function return
27517 type is @code{void} or if the return value was not computable. This attribute
27521 @node Lazy Strings In Python
27522 @subsubsection Python representation of lazy strings.
27524 @cindex lazy strings in python
27525 @tindex gdb.LazyString
27527 A @dfn{lazy string} is a string whose contents is not retrieved or
27528 encoded until it is needed.
27530 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27531 @code{address} that points to a region of memory, an @code{encoding}
27532 that will be used to encode that region of memory, and a @code{length}
27533 to delimit the region of memory that represents the string. The
27534 difference between a @code{gdb.LazyString} and a string wrapped within
27535 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27536 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27537 retrieved and encoded during printing, while a @code{gdb.Value}
27538 wrapping a string is immediately retrieved and encoded on creation.
27540 A @code{gdb.LazyString} object has the following functions:
27542 @defun LazyString.value ()
27543 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27544 will point to the string in memory, but will lose all the delayed
27545 retrieval, encoding and handling that @value{GDBN} applies to a
27546 @code{gdb.LazyString}.
27549 @defvar LazyString.address
27550 This attribute holds the address of the string. This attribute is not
27554 @defvar LazyString.length
27555 This attribute holds the length of the string in characters. If the
27556 length is -1, then the string will be fetched and encoded up to the
27557 first null of appropriate width. This attribute is not writable.
27560 @defvar LazyString.encoding
27561 This attribute holds the encoding that will be applied to the string
27562 when the string is printed by @value{GDBN}. If the encoding is not
27563 set, or contains an empty string, then @value{GDBN} will select the
27564 most appropriate encoding when the string is printed. This attribute
27568 @defvar LazyString.type
27569 This attribute holds the type that is represented by the lazy string's
27570 type. For a lazy string this will always be a pointer type. To
27571 resolve this to the lazy string's character type, use the type's
27572 @code{target} method. @xref{Types In Python}. This attribute is not
27576 @node Architectures In Python
27577 @subsubsection Python representation of architectures
27578 @cindex Python architectures
27580 @value{GDBN} uses architecture specific parameters and artifacts in a
27581 number of its various computations. An architecture is represented
27582 by an instance of the @code{gdb.Architecture} class.
27584 A @code{gdb.Architecture} class has the following methods:
27586 @defun Architecture.name ()
27587 Return the name (string value) of the architecture.
27590 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27591 Return a list of disassembled instructions starting from the memory
27592 address @var{start_pc}. The optional arguments @var{end_pc} and
27593 @var{count} determine the number of instructions in the returned list.
27594 If both the optional arguments @var{end_pc} and @var{count} are
27595 specified, then a list of at most @var{count} disassembled instructions
27596 whose start address falls in the closed memory address interval from
27597 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27598 specified, but @var{count} is specified, then @var{count} number of
27599 instructions starting from the address @var{start_pc} are returned. If
27600 @var{count} is not specified but @var{end_pc} is specified, then all
27601 instructions whose start address falls in the closed memory address
27602 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27603 @var{end_pc} nor @var{count} are specified, then a single instruction at
27604 @var{start_pc} is returned. For all of these cases, each element of the
27605 returned list is a Python @code{dict} with the following string keys:
27610 The value corresponding to this key is a Python long integer capturing
27611 the memory address of the instruction.
27614 The value corresponding to this key is a string value which represents
27615 the instruction with assembly language mnemonics. The assembly
27616 language flavor used is the same as that specified by the current CLI
27617 variable @code{disassembly-flavor}. @xref{Machine Code}.
27620 The value corresponding to this key is the length (integer value) of the
27621 instruction in bytes.
27626 @node Python Auto-loading
27627 @subsection Python Auto-loading
27628 @cindex Python auto-loading
27630 When a new object file is read (for example, due to the @code{file}
27631 command, or because the inferior has loaded a shared library),
27632 @value{GDBN} will look for Python support scripts in several ways:
27633 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
27634 @xref{Auto-loading extensions}.
27636 The auto-loading feature is useful for supplying application-specific
27637 debugging commands and scripts.
27639 Auto-loading can be enabled or disabled,
27640 and the list of auto-loaded scripts can be printed.
27643 @anchor{set auto-load python-scripts}
27644 @kindex set auto-load python-scripts
27645 @item set auto-load python-scripts [on|off]
27646 Enable or disable the auto-loading of Python scripts.
27648 @anchor{show auto-load python-scripts}
27649 @kindex show auto-load python-scripts
27650 @item show auto-load python-scripts
27651 Show whether auto-loading of Python scripts is enabled or disabled.
27653 @anchor{info auto-load python-scripts}
27654 @kindex info auto-load python-scripts
27655 @cindex print list of auto-loaded Python scripts
27656 @item info auto-load python-scripts [@var{regexp}]
27657 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27659 Also printed is the list of Python scripts that were mentioned in
27660 the @code{.debug_gdb_scripts} section and were not found
27661 (@pxref{dotdebug_gdb_scripts section}).
27662 This is useful because their names are not printed when @value{GDBN}
27663 tries to load them and fails. There may be many of them, and printing
27664 an error message for each one is problematic.
27666 If @var{regexp} is supplied only Python scripts with matching names are printed.
27671 (gdb) info auto-load python-scripts
27673 Yes py-section-script.py
27674 full name: /tmp/py-section-script.py
27675 No my-foo-pretty-printers.py
27679 When reading an auto-loaded file, @value{GDBN} sets the
27680 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27681 function (@pxref{Objfiles In Python}). This can be useful for
27682 registering objfile-specific pretty-printers and frame-filters.
27684 @node Python modules
27685 @subsection Python modules
27686 @cindex python modules
27688 @value{GDBN} comes with several modules to assist writing Python code.
27691 * gdb.printing:: Building and registering pretty-printers.
27692 * gdb.types:: Utilities for working with types.
27693 * gdb.prompt:: Utilities for prompt value substitution.
27697 @subsubsection gdb.printing
27698 @cindex gdb.printing
27700 This module provides a collection of utilities for working with
27704 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27705 This class specifies the API that makes @samp{info pretty-printer},
27706 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27707 Pretty-printers should generally inherit from this class.
27709 @item SubPrettyPrinter (@var{name})
27710 For printers that handle multiple types, this class specifies the
27711 corresponding API for the subprinters.
27713 @item RegexpCollectionPrettyPrinter (@var{name})
27714 Utility class for handling multiple printers, all recognized via
27715 regular expressions.
27716 @xref{Writing a Pretty-Printer}, for an example.
27718 @item FlagEnumerationPrinter (@var{name})
27719 A pretty-printer which handles printing of @code{enum} values. Unlike
27720 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27721 work properly when there is some overlap between the enumeration
27722 constants. @var{name} is the name of the printer and also the name of
27723 the @code{enum} type to look up.
27725 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27726 Register @var{printer} with the pretty-printer list of @var{obj}.
27727 If @var{replace} is @code{True} then any existing copy of the printer
27728 is replaced. Otherwise a @code{RuntimeError} exception is raised
27729 if a printer with the same name already exists.
27733 @subsubsection gdb.types
27736 This module provides a collection of utilities for working with
27737 @code{gdb.Type} objects.
27740 @item get_basic_type (@var{type})
27741 Return @var{type} with const and volatile qualifiers stripped,
27742 and with typedefs and C@t{++} references converted to the underlying type.
27747 typedef const int const_int;
27749 const_int& foo_ref (foo);
27750 int main () @{ return 0; @}
27757 (gdb) python import gdb.types
27758 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27759 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27763 @item has_field (@var{type}, @var{field})
27764 Return @code{True} if @var{type}, assumed to be a type with fields
27765 (e.g., a structure or union), has field @var{field}.
27767 @item make_enum_dict (@var{enum_type})
27768 Return a Python @code{dictionary} type produced from @var{enum_type}.
27770 @item deep_items (@var{type})
27771 Returns a Python iterator similar to the standard
27772 @code{gdb.Type.iteritems} method, except that the iterator returned
27773 by @code{deep_items} will recursively traverse anonymous struct or
27774 union fields. For example:
27788 Then in @value{GDBN}:
27790 (@value{GDBP}) python import gdb.types
27791 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27792 (@value{GDBP}) python print struct_a.keys ()
27794 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27795 @{['a', 'b0', 'b1']@}
27798 @item get_type_recognizers ()
27799 Return a list of the enabled type recognizers for the current context.
27800 This is called by @value{GDBN} during the type-printing process
27801 (@pxref{Type Printing API}).
27803 @item apply_type_recognizers (recognizers, type_obj)
27804 Apply the type recognizers, @var{recognizers}, to the type object
27805 @var{type_obj}. If any recognizer returns a string, return that
27806 string. Otherwise, return @code{None}. This is called by
27807 @value{GDBN} during the type-printing process (@pxref{Type Printing
27810 @item register_type_printer (locus, printer)
27811 This is a convenience function to register a type printer.
27812 @var{printer} is the type printer to register. It must implement the
27813 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27814 which case the printer is registered with that objfile; a
27815 @code{gdb.Progspace}, in which case the printer is registered with
27816 that progspace; or @code{None}, in which case the printer is
27817 registered globally.
27820 This is a base class that implements the type printer protocol. Type
27821 printers are encouraged, but not required, to derive from this class.
27822 It defines a constructor:
27824 @defmethod TypePrinter __init__ (self, name)
27825 Initialize the type printer with the given name. The new printer
27826 starts in the enabled state.
27832 @subsubsection gdb.prompt
27835 This module provides a method for prompt value-substitution.
27838 @item substitute_prompt (@var{string})
27839 Return @var{string} with escape sequences substituted by values. Some
27840 escape sequences take arguments. You can specify arguments inside
27841 ``@{@}'' immediately following the escape sequence.
27843 The escape sequences you can pass to this function are:
27847 Substitute a backslash.
27849 Substitute an ESC character.
27851 Substitute the selected frame; an argument names a frame parameter.
27853 Substitute a newline.
27855 Substitute a parameter's value; the argument names the parameter.
27857 Substitute a carriage return.
27859 Substitute the selected thread; an argument names a thread parameter.
27861 Substitute the version of GDB.
27863 Substitute the current working directory.
27865 Begin a sequence of non-printing characters. These sequences are
27866 typically used with the ESC character, and are not counted in the string
27867 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27868 blue-colored ``(gdb)'' prompt where the length is five.
27870 End a sequence of non-printing characters.
27876 substitute_prompt (``frame: \f,
27877 print arguments: \p@{print frame-arguments@}'')
27880 @exdent will return the string:
27883 "frame: main, print arguments: scalars"
27887 @node Auto-loading extensions
27888 @section Auto-loading extensions
27889 @cindex auto-loading extensions
27891 @value{GDBN} provides two mechanisms for automatically loading extensions
27892 when a new object file is read (for example, due to the @code{file}
27893 command, or because the inferior has loaded a shared library):
27894 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
27895 section of modern file formats like ELF.
27898 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
27899 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
27900 * Which flavor to choose?::
27903 The auto-loading feature is useful for supplying application-specific
27904 debugging commands and features.
27906 Auto-loading can be enabled or disabled,
27907 and the list of auto-loaded scripts can be printed.
27908 See the @samp{auto-loading} section of each extension language
27909 for more information.
27910 For @value{GDBN} command files see @ref{Auto-loading sequences}.
27911 For Python files see @ref{Python Auto-loading}.
27913 Note that loading of this script file also requires accordingly configured
27914 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27916 @node objfile-gdbdotext file
27917 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
27918 @cindex @file{@var{objfile}-gdb.gdb}
27919 @cindex @file{@var{objfile}-gdb.py}
27920 @cindex @file{@var{objfile}-gdb.scm}
27922 When a new object file is read, @value{GDBN} looks for a file named
27923 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
27924 where @var{objfile} is the object file's name and
27925 where @var{ext} is the file extension for the extension language:
27928 @item @file{@var{objfile}-gdb.gdb}
27929 GDB's own command language
27930 @item @file{@var{objfile}-gdb.py}
27934 @var{script-name} is formed by ensuring that the file name of @var{objfile}
27935 is absolute, following all symlinks, and resolving @code{.} and @code{..}
27936 components, and appending the @file{-gdb.@var{ext}} suffix.
27937 If this file exists and is readable, @value{GDBN} will evaluate it as a
27938 script in the specified extension language.
27940 If this file does not exist, then @value{GDBN} will look for
27941 @var{script-name} file in all of the directories as specified below.
27943 Note that loading of these files requires an accordingly configured
27944 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27946 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27947 scripts normally according to its @file{.exe} filename. But if no scripts are
27948 found @value{GDBN} also tries script filenames matching the object file without
27949 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27950 is attempted on any platform. This makes the script filenames compatible
27951 between Unix and MS-Windows hosts.
27954 @anchor{set auto-load scripts-directory}
27955 @kindex set auto-load scripts-directory
27956 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27957 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27958 may be delimited by the host platform path separator in use
27959 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27961 Each entry here needs to be covered also by the security setting
27962 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27964 @anchor{with-auto-load-dir}
27965 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27966 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27967 configuration option @option{--with-auto-load-dir}.
27969 Any reference to @file{$debugdir} will get replaced by
27970 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27971 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27972 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27973 @file{$datadir} must be placed as a directory component --- either alone or
27974 delimited by @file{/} or @file{\} directory separators, depending on the host
27977 The list of directories uses path separator (@samp{:} on GNU and Unix
27978 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27979 to the @env{PATH} environment variable.
27981 @anchor{show auto-load scripts-directory}
27982 @kindex show auto-load scripts-directory
27983 @item show auto-load scripts-directory
27984 Show @value{GDBN} auto-loaded scripts location.
27987 @value{GDBN} does not track which files it has already auto-loaded this way.
27988 @value{GDBN} will load the associated script every time the corresponding
27989 @var{objfile} is opened.
27990 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
27991 is evaluated more than once.
27993 @node dotdebug_gdb_scripts section
27994 @subsection The @code{.debug_gdb_scripts} section
27995 @cindex @code{.debug_gdb_scripts} section
27997 For systems using file formats like ELF and COFF,
27998 when @value{GDBN} loads a new object file
27999 it will look for a special section named @code{.debug_gdb_scripts}.
28000 If this section exists, its contents is a list of NUL-terminated names
28001 of scripts to load. Each entry begins with a non-NULL prefix byte that
28002 specifies the kind of entry, typically the extension language.
28004 @value{GDBN} will look for each specified script file first in the
28005 current directory and then along the source search path
28006 (@pxref{Source Path, ,Specifying Source Directories}),
28007 except that @file{$cdir} is not searched, since the compilation
28008 directory is not relevant to scripts.
28010 Entries can be placed in section @code{.debug_gdb_scripts} with,
28011 for example, this GCC macro for Python scripts.
28014 /* Note: The "MS" section flags are to remove duplicates. */
28015 #define DEFINE_GDB_PY_SCRIPT(script_name) \
28017 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
28018 .byte 1 /* Python */\n\
28019 .asciz \"" script_name "\"\n\
28025 Then one can reference the macro in a header or source file like this:
28028 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
28031 The script name may include directories if desired.
28033 Note that loading of this script file also requires accordingly configured
28034 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
28036 If the macro invocation is put in a header, any application or library
28037 using this header will get a reference to the specified script,
28038 and with the use of @code{"MS"} attributes on the section, the linker
28039 will remove duplicates.
28041 @node Which flavor to choose?
28042 @subsection Which flavor to choose?
28044 Given the multiple ways of auto-loading extensions, it might not always
28045 be clear which one to choose. This section provides some guidance.
28048 Benefits of the @file{-gdb.@var{ext}} way:
28052 Can be used with file formats that don't support multiple sections.
28055 Ease of finding scripts for public libraries.
28057 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
28058 in the source search path.
28059 For publicly installed libraries, e.g., @file{libstdc++}, there typically
28060 isn't a source directory in which to find the script.
28063 Doesn't require source code additions.
28067 Benefits of the @code{.debug_gdb_scripts} way:
28071 Works with static linking.
28073 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
28074 trigger their loading. When an application is statically linked the only
28075 objfile available is the executable, and it is cumbersome to attach all the
28076 scripts from all the input libraries to the executable's
28077 @file{-gdb.@var{ext}} script.
28080 Works with classes that are entirely inlined.
28082 Some classes can be entirely inlined, and thus there may not be an associated
28083 shared library to attach a @file{-gdb.@var{ext}} script to.
28086 Scripts needn't be copied out of the source tree.
28088 In some circumstances, apps can be built out of large collections of internal
28089 libraries, and the build infrastructure necessary to install the
28090 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
28091 cumbersome. It may be easier to specify the scripts in the
28092 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
28093 top of the source tree to the source search path.
28097 @section Creating new spellings of existing commands
28098 @cindex aliases for commands
28100 It is often useful to define alternate spellings of existing commands.
28101 For example, if a new @value{GDBN} command defined in Python has
28102 a long name to type, it is handy to have an abbreviated version of it
28103 that involves less typing.
28105 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
28106 of the @samp{step} command even though it is otherwise an ambiguous
28107 abbreviation of other commands like @samp{set} and @samp{show}.
28109 Aliases are also used to provide shortened or more common versions
28110 of multi-word commands. For example, @value{GDBN} provides the
28111 @samp{tty} alias of the @samp{set inferior-tty} command.
28113 You can define a new alias with the @samp{alias} command.
28118 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
28122 @var{ALIAS} specifies the name of the new alias.
28123 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
28126 @var{COMMAND} specifies the name of an existing command
28127 that is being aliased.
28129 The @samp{-a} option specifies that the new alias is an abbreviation
28130 of the command. Abbreviations are not shown in command
28131 lists displayed by the @samp{help} command.
28133 The @samp{--} option specifies the end of options,
28134 and is useful when @var{ALIAS} begins with a dash.
28136 Here is a simple example showing how to make an abbreviation
28137 of a command so that there is less to type.
28138 Suppose you were tired of typing @samp{disas}, the current
28139 shortest unambiguous abbreviation of the @samp{disassemble} command
28140 and you wanted an even shorter version named @samp{di}.
28141 The following will accomplish this.
28144 (gdb) alias -a di = disas
28147 Note that aliases are different from user-defined commands.
28148 With a user-defined command, you also need to write documentation
28149 for it with the @samp{document} command.
28150 An alias automatically picks up the documentation of the existing command.
28152 Here is an example where we make @samp{elms} an abbreviation of
28153 @samp{elements} in the @samp{set print elements} command.
28154 This is to show that you can make an abbreviation of any part
28158 (gdb) alias -a set print elms = set print elements
28159 (gdb) alias -a show print elms = show print elements
28160 (gdb) set p elms 20
28162 Limit on string chars or array elements to print is 200.
28165 Note that if you are defining an alias of a @samp{set} command,
28166 and you want to have an alias for the corresponding @samp{show}
28167 command, then you need to define the latter separately.
28169 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
28170 @var{ALIAS}, just as they are normally.
28173 (gdb) alias -a set pr elms = set p ele
28176 Finally, here is an example showing the creation of a one word
28177 alias for a more complex command.
28178 This creates alias @samp{spe} of the command @samp{set print elements}.
28181 (gdb) alias spe = set print elements
28186 @chapter Command Interpreters
28187 @cindex command interpreters
28189 @value{GDBN} supports multiple command interpreters, and some command
28190 infrastructure to allow users or user interface writers to switch
28191 between interpreters or run commands in other interpreters.
28193 @value{GDBN} currently supports two command interpreters, the console
28194 interpreter (sometimes called the command-line interpreter or @sc{cli})
28195 and the machine interface interpreter (or @sc{gdb/mi}). This manual
28196 describes both of these interfaces in great detail.
28198 By default, @value{GDBN} will start with the console interpreter.
28199 However, the user may choose to start @value{GDBN} with another
28200 interpreter by specifying the @option{-i} or @option{--interpreter}
28201 startup options. Defined interpreters include:
28205 @cindex console interpreter
28206 The traditional console or command-line interpreter. This is the most often
28207 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
28208 @value{GDBN} will use this interpreter.
28211 @cindex mi interpreter
28212 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
28213 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
28214 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
28218 @cindex mi2 interpreter
28219 The current @sc{gdb/mi} interface.
28222 @cindex mi1 interpreter
28223 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
28227 @cindex invoke another interpreter
28228 The interpreter being used by @value{GDBN} may not be dynamically
28229 switched at runtime. Although possible, this could lead to a very
28230 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
28231 enters the command "interpreter-set console" in a console view,
28232 @value{GDBN} would switch to using the console interpreter, rendering
28233 the IDE inoperable!
28235 @kindex interpreter-exec
28236 Although you may only choose a single interpreter at startup, you may execute
28237 commands in any interpreter from the current interpreter using the appropriate
28238 command. If you are running the console interpreter, simply use the
28239 @code{interpreter-exec} command:
28242 interpreter-exec mi "-data-list-register-names"
28245 @sc{gdb/mi} has a similar command, although it is only available in versions of
28246 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
28249 @chapter @value{GDBN} Text User Interface
28251 @cindex Text User Interface
28254 * TUI Overview:: TUI overview
28255 * TUI Keys:: TUI key bindings
28256 * TUI Single Key Mode:: TUI single key mode
28257 * TUI Commands:: TUI-specific commands
28258 * TUI Configuration:: TUI configuration variables
28261 The @value{GDBN} Text User Interface (TUI) is a terminal
28262 interface which uses the @code{curses} library to show the source
28263 file, the assembly output, the program registers and @value{GDBN}
28264 commands in separate text windows. The TUI mode is supported only
28265 on platforms where a suitable version of the @code{curses} library
28268 The TUI mode is enabled by default when you invoke @value{GDBN} as
28269 @samp{@value{GDBP} -tui}.
28270 You can also switch in and out of TUI mode while @value{GDBN} runs by
28271 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
28272 @xref{TUI Keys, ,TUI Key Bindings}.
28275 @section TUI Overview
28277 In TUI mode, @value{GDBN} can display several text windows:
28281 This window is the @value{GDBN} command window with the @value{GDBN}
28282 prompt and the @value{GDBN} output. The @value{GDBN} input is still
28283 managed using readline.
28286 The source window shows the source file of the program. The current
28287 line and active breakpoints are displayed in this window.
28290 The assembly window shows the disassembly output of the program.
28293 This window shows the processor registers. Registers are highlighted
28294 when their values change.
28297 The source and assembly windows show the current program position
28298 by highlighting the current line and marking it with a @samp{>} marker.
28299 Breakpoints are indicated with two markers. The first marker
28300 indicates the breakpoint type:
28304 Breakpoint which was hit at least once.
28307 Breakpoint which was never hit.
28310 Hardware breakpoint which was hit at least once.
28313 Hardware breakpoint which was never hit.
28316 The second marker indicates whether the breakpoint is enabled or not:
28320 Breakpoint is enabled.
28323 Breakpoint is disabled.
28326 The source, assembly and register windows are updated when the current
28327 thread changes, when the frame changes, or when the program counter
28330 These windows are not all visible at the same time. The command
28331 window is always visible. The others can be arranged in several
28342 source and assembly,
28345 source and registers, or
28348 assembly and registers.
28351 A status line above the command window shows the following information:
28355 Indicates the current @value{GDBN} target.
28356 (@pxref{Targets, ,Specifying a Debugging Target}).
28359 Gives the current process or thread number.
28360 When no process is being debugged, this field is set to @code{No process}.
28363 Gives the current function name for the selected frame.
28364 The name is demangled if demangling is turned on (@pxref{Print Settings}).
28365 When there is no symbol corresponding to the current program counter,
28366 the string @code{??} is displayed.
28369 Indicates the current line number for the selected frame.
28370 When the current line number is not known, the string @code{??} is displayed.
28373 Indicates the current program counter address.
28377 @section TUI Key Bindings
28378 @cindex TUI key bindings
28380 The TUI installs several key bindings in the readline keymaps
28381 @ifset SYSTEM_READLINE
28382 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
28384 @ifclear SYSTEM_READLINE
28385 (@pxref{Command Line Editing}).
28387 The following key bindings are installed for both TUI mode and the
28388 @value{GDBN} standard mode.
28397 Enter or leave the TUI mode. When leaving the TUI mode,
28398 the curses window management stops and @value{GDBN} operates using
28399 its standard mode, writing on the terminal directly. When reentering
28400 the TUI mode, control is given back to the curses windows.
28401 The screen is then refreshed.
28405 Use a TUI layout with only one window. The layout will
28406 either be @samp{source} or @samp{assembly}. When the TUI mode
28407 is not active, it will switch to the TUI mode.
28409 Think of this key binding as the Emacs @kbd{C-x 1} binding.
28413 Use a TUI layout with at least two windows. When the current
28414 layout already has two windows, the next layout with two windows is used.
28415 When a new layout is chosen, one window will always be common to the
28416 previous layout and the new one.
28418 Think of it as the Emacs @kbd{C-x 2} binding.
28422 Change the active window. The TUI associates several key bindings
28423 (like scrolling and arrow keys) with the active window. This command
28424 gives the focus to the next TUI window.
28426 Think of it as the Emacs @kbd{C-x o} binding.
28430 Switch in and out of the TUI SingleKey mode that binds single
28431 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
28434 The following key bindings only work in the TUI mode:
28439 Scroll the active window one page up.
28443 Scroll the active window one page down.
28447 Scroll the active window one line up.
28451 Scroll the active window one line down.
28455 Scroll the active window one column left.
28459 Scroll the active window one column right.
28463 Refresh the screen.
28466 Because the arrow keys scroll the active window in the TUI mode, they
28467 are not available for their normal use by readline unless the command
28468 window has the focus. When another window is active, you must use
28469 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28470 and @kbd{C-f} to control the command window.
28472 @node TUI Single Key Mode
28473 @section TUI Single Key Mode
28474 @cindex TUI single key mode
28476 The TUI also provides a @dfn{SingleKey} mode, which binds several
28477 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28478 switch into this mode, where the following key bindings are used:
28481 @kindex c @r{(SingleKey TUI key)}
28485 @kindex d @r{(SingleKey TUI key)}
28489 @kindex f @r{(SingleKey TUI key)}
28493 @kindex n @r{(SingleKey TUI key)}
28497 @kindex q @r{(SingleKey TUI key)}
28499 exit the SingleKey mode.
28501 @kindex r @r{(SingleKey TUI key)}
28505 @kindex s @r{(SingleKey TUI key)}
28509 @kindex u @r{(SingleKey TUI key)}
28513 @kindex v @r{(SingleKey TUI key)}
28517 @kindex w @r{(SingleKey TUI key)}
28522 Other keys temporarily switch to the @value{GDBN} command prompt.
28523 The key that was pressed is inserted in the editing buffer so that
28524 it is possible to type most @value{GDBN} commands without interaction
28525 with the TUI SingleKey mode. Once the command is entered the TUI
28526 SingleKey mode is restored. The only way to permanently leave
28527 this mode is by typing @kbd{q} or @kbd{C-x s}.
28531 @section TUI-specific Commands
28532 @cindex TUI commands
28534 The TUI has specific commands to control the text windows.
28535 These commands are always available, even when @value{GDBN} is not in
28536 the TUI mode. When @value{GDBN} is in the standard mode, most
28537 of these commands will automatically switch to the TUI mode.
28539 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28540 terminal, or @value{GDBN} has been started with the machine interface
28541 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28542 these commands will fail with an error, because it would not be
28543 possible or desirable to enable curses window management.
28548 List and give the size of all displayed windows.
28552 Display the next layout.
28555 Display the previous layout.
28558 Display the source window only.
28561 Display the assembly window only.
28564 Display the source and assembly window.
28567 Display the register window together with the source or assembly window.
28571 Make the next window active for scrolling.
28574 Make the previous window active for scrolling.
28577 Make the source window active for scrolling.
28580 Make the assembly window active for scrolling.
28583 Make the register window active for scrolling.
28586 Make the command window active for scrolling.
28590 Refresh the screen. This is similar to typing @kbd{C-L}.
28592 @item tui reg float
28594 Show the floating point registers in the register window.
28596 @item tui reg general
28597 Show the general registers in the register window.
28600 Show the next register group. The list of register groups as well as
28601 their order is target specific. The predefined register groups are the
28602 following: @code{general}, @code{float}, @code{system}, @code{vector},
28603 @code{all}, @code{save}, @code{restore}.
28605 @item tui reg system
28606 Show the system registers in the register window.
28610 Update the source window and the current execution point.
28612 @item winheight @var{name} +@var{count}
28613 @itemx winheight @var{name} -@var{count}
28615 Change the height of the window @var{name} by @var{count}
28616 lines. Positive counts increase the height, while negative counts
28619 @item tabset @var{nchars}
28621 Set the width of tab stops to be @var{nchars} characters.
28624 @node TUI Configuration
28625 @section TUI Configuration Variables
28626 @cindex TUI configuration variables
28628 Several configuration variables control the appearance of TUI windows.
28631 @item set tui border-kind @var{kind}
28632 @kindex set tui border-kind
28633 Select the border appearance for the source, assembly and register windows.
28634 The possible values are the following:
28637 Use a space character to draw the border.
28640 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28643 Use the Alternate Character Set to draw the border. The border is
28644 drawn using character line graphics if the terminal supports them.
28647 @item set tui border-mode @var{mode}
28648 @kindex set tui border-mode
28649 @itemx set tui active-border-mode @var{mode}
28650 @kindex set tui active-border-mode
28651 Select the display attributes for the borders of the inactive windows
28652 or the active window. The @var{mode} can be one of the following:
28655 Use normal attributes to display the border.
28661 Use reverse video mode.
28664 Use half bright mode.
28666 @item half-standout
28667 Use half bright and standout mode.
28670 Use extra bright or bold mode.
28672 @item bold-standout
28673 Use extra bright or bold and standout mode.
28678 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28681 @cindex @sc{gnu} Emacs
28682 A special interface allows you to use @sc{gnu} Emacs to view (and
28683 edit) the source files for the program you are debugging with
28686 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28687 executable file you want to debug as an argument. This command starts
28688 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28689 created Emacs buffer.
28690 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28692 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28697 All ``terminal'' input and output goes through an Emacs buffer, called
28700 This applies both to @value{GDBN} commands and their output, and to the input
28701 and output done by the program you are debugging.
28703 This is useful because it means that you can copy the text of previous
28704 commands and input them again; you can even use parts of the output
28707 All the facilities of Emacs' Shell mode are available for interacting
28708 with your program. In particular, you can send signals the usual
28709 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28713 @value{GDBN} displays source code through Emacs.
28715 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28716 source file for that frame and puts an arrow (@samp{=>}) at the
28717 left margin of the current line. Emacs uses a separate buffer for
28718 source display, and splits the screen to show both your @value{GDBN} session
28721 Explicit @value{GDBN} @code{list} or search commands still produce output as
28722 usual, but you probably have no reason to use them from Emacs.
28725 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28726 a graphical mode, enabled by default, which provides further buffers
28727 that can control the execution and describe the state of your program.
28728 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28730 If you specify an absolute file name when prompted for the @kbd{M-x
28731 gdb} argument, then Emacs sets your current working directory to where
28732 your program resides. If you only specify the file name, then Emacs
28733 sets your current working directory to the directory associated
28734 with the previous buffer. In this case, @value{GDBN} may find your
28735 program by searching your environment's @code{PATH} variable, but on
28736 some operating systems it might not find the source. So, although the
28737 @value{GDBN} input and output session proceeds normally, the auxiliary
28738 buffer does not display the current source and line of execution.
28740 The initial working directory of @value{GDBN} is printed on the top
28741 line of the GUD buffer and this serves as a default for the commands
28742 that specify files for @value{GDBN} to operate on. @xref{Files,
28743 ,Commands to Specify Files}.
28745 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28746 need to call @value{GDBN} by a different name (for example, if you
28747 keep several configurations around, with different names) you can
28748 customize the Emacs variable @code{gud-gdb-command-name} to run the
28751 In the GUD buffer, you can use these special Emacs commands in
28752 addition to the standard Shell mode commands:
28756 Describe the features of Emacs' GUD Mode.
28759 Execute to another source line, like the @value{GDBN} @code{step} command; also
28760 update the display window to show the current file and location.
28763 Execute to next source line in this function, skipping all function
28764 calls, like the @value{GDBN} @code{next} command. Then update the display window
28765 to show the current file and location.
28768 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28769 display window accordingly.
28772 Execute until exit from the selected stack frame, like the @value{GDBN}
28773 @code{finish} command.
28776 Continue execution of your program, like the @value{GDBN} @code{continue}
28780 Go up the number of frames indicated by the numeric argument
28781 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28782 like the @value{GDBN} @code{up} command.
28785 Go down the number of frames indicated by the numeric argument, like the
28786 @value{GDBN} @code{down} command.
28789 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28790 tells @value{GDBN} to set a breakpoint on the source line point is on.
28792 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28793 separate frame which shows a backtrace when the GUD buffer is current.
28794 Move point to any frame in the stack and type @key{RET} to make it
28795 become the current frame and display the associated source in the
28796 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28797 selected frame become the current one. In graphical mode, the
28798 speedbar displays watch expressions.
28800 If you accidentally delete the source-display buffer, an easy way to get
28801 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28802 request a frame display; when you run under Emacs, this recreates
28803 the source buffer if necessary to show you the context of the current
28806 The source files displayed in Emacs are in ordinary Emacs buffers
28807 which are visiting the source files in the usual way. You can edit
28808 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28809 communicates with Emacs in terms of line numbers. If you add or
28810 delete lines from the text, the line numbers that @value{GDBN} knows cease
28811 to correspond properly with the code.
28813 A more detailed description of Emacs' interaction with @value{GDBN} is
28814 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28818 @chapter The @sc{gdb/mi} Interface
28820 @unnumberedsec Function and Purpose
28822 @cindex @sc{gdb/mi}, its purpose
28823 @sc{gdb/mi} is a line based machine oriented text interface to
28824 @value{GDBN} and is activated by specifying using the
28825 @option{--interpreter} command line option (@pxref{Mode Options}). It
28826 is specifically intended to support the development of systems which
28827 use the debugger as just one small component of a larger system.
28829 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28830 in the form of a reference manual.
28832 Note that @sc{gdb/mi} is still under construction, so some of the
28833 features described below are incomplete and subject to change
28834 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28836 @unnumberedsec Notation and Terminology
28838 @cindex notational conventions, for @sc{gdb/mi}
28839 This chapter uses the following notation:
28843 @code{|} separates two alternatives.
28846 @code{[ @var{something} ]} indicates that @var{something} is optional:
28847 it may or may not be given.
28850 @code{( @var{group} )*} means that @var{group} inside the parentheses
28851 may repeat zero or more times.
28854 @code{( @var{group} )+} means that @var{group} inside the parentheses
28855 may repeat one or more times.
28858 @code{"@var{string}"} means a literal @var{string}.
28862 @heading Dependencies
28866 * GDB/MI General Design::
28867 * GDB/MI Command Syntax::
28868 * GDB/MI Compatibility with CLI::
28869 * GDB/MI Development and Front Ends::
28870 * GDB/MI Output Records::
28871 * GDB/MI Simple Examples::
28872 * GDB/MI Command Description Format::
28873 * GDB/MI Breakpoint Commands::
28874 * GDB/MI Catchpoint Commands::
28875 * GDB/MI Program Context::
28876 * GDB/MI Thread Commands::
28877 * GDB/MI Ada Tasking Commands::
28878 * GDB/MI Program Execution::
28879 * GDB/MI Stack Manipulation::
28880 * GDB/MI Variable Objects::
28881 * GDB/MI Data Manipulation::
28882 * GDB/MI Tracepoint Commands::
28883 * GDB/MI Symbol Query::
28884 * GDB/MI File Commands::
28886 * GDB/MI Kod Commands::
28887 * GDB/MI Memory Overlay Commands::
28888 * GDB/MI Signal Handling Commands::
28890 * GDB/MI Target Manipulation::
28891 * GDB/MI File Transfer Commands::
28892 * GDB/MI Ada Exceptions Commands::
28893 * GDB/MI Support Commands::
28894 * GDB/MI Miscellaneous Commands::
28897 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28898 @node GDB/MI General Design
28899 @section @sc{gdb/mi} General Design
28900 @cindex GDB/MI General Design
28902 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28903 parts---commands sent to @value{GDBN}, responses to those commands
28904 and notifications. Each command results in exactly one response,
28905 indicating either successful completion of the command, or an error.
28906 For the commands that do not resume the target, the response contains the
28907 requested information. For the commands that resume the target, the
28908 response only indicates whether the target was successfully resumed.
28909 Notifications is the mechanism for reporting changes in the state of the
28910 target, or in @value{GDBN} state, that cannot conveniently be associated with
28911 a command and reported as part of that command response.
28913 The important examples of notifications are:
28917 Exec notifications. These are used to report changes in
28918 target state---when a target is resumed, or stopped. It would not
28919 be feasible to include this information in response of resuming
28920 commands, because one resume commands can result in multiple events in
28921 different threads. Also, quite some time may pass before any event
28922 happens in the target, while a frontend needs to know whether the resuming
28923 command itself was successfully executed.
28926 Console output, and status notifications. Console output
28927 notifications are used to report output of CLI commands, as well as
28928 diagnostics for other commands. Status notifications are used to
28929 report the progress of a long-running operation. Naturally, including
28930 this information in command response would mean no output is produced
28931 until the command is finished, which is undesirable.
28934 General notifications. Commands may have various side effects on
28935 the @value{GDBN} or target state beyond their official purpose. For example,
28936 a command may change the selected thread. Although such changes can
28937 be included in command response, using notification allows for more
28938 orthogonal frontend design.
28942 There's no guarantee that whenever an MI command reports an error,
28943 @value{GDBN} or the target are in any specific state, and especially,
28944 the state is not reverted to the state before the MI command was
28945 processed. Therefore, whenever an MI command results in an error,
28946 we recommend that the frontend refreshes all the information shown in
28947 the user interface.
28951 * Context management::
28952 * Asynchronous and non-stop modes::
28956 @node Context management
28957 @subsection Context management
28959 @subsubsection Threads and Frames
28961 In most cases when @value{GDBN} accesses the target, this access is
28962 done in context of a specific thread and frame (@pxref{Frames}).
28963 Often, even when accessing global data, the target requires that a thread
28964 be specified. The CLI interface maintains the selected thread and frame,
28965 and supplies them to target on each command. This is convenient,
28966 because a command line user would not want to specify that information
28967 explicitly on each command, and because user interacts with
28968 @value{GDBN} via a single terminal, so no confusion is possible as
28969 to what thread and frame are the current ones.
28971 In the case of MI, the concept of selected thread and frame is less
28972 useful. First, a frontend can easily remember this information
28973 itself. Second, a graphical frontend can have more than one window,
28974 each one used for debugging a different thread, and the frontend might
28975 want to access additional threads for internal purposes. This
28976 increases the risk that by relying on implicitly selected thread, the
28977 frontend may be operating on a wrong one. Therefore, each MI command
28978 should explicitly specify which thread and frame to operate on. To
28979 make it possible, each MI command accepts the @samp{--thread} and
28980 @samp{--frame} options, the value to each is @value{GDBN} identifier
28981 for thread and frame to operate on.
28983 Usually, each top-level window in a frontend allows the user to select
28984 a thread and a frame, and remembers the user selection for further
28985 operations. However, in some cases @value{GDBN} may suggest that the
28986 current thread be changed. For example, when stopping on a breakpoint
28987 it is reasonable to switch to the thread where breakpoint is hit. For
28988 another example, if the user issues the CLI @samp{thread} command via
28989 the frontend, it is desirable to change the frontend's selected thread to the
28990 one specified by user. @value{GDBN} communicates the suggestion to
28991 change current thread using the @samp{=thread-selected} notification.
28992 No such notification is available for the selected frame at the moment.
28994 Note that historically, MI shares the selected thread with CLI, so
28995 frontends used the @code{-thread-select} to execute commands in the
28996 right context. However, getting this to work right is cumbersome. The
28997 simplest way is for frontend to emit @code{-thread-select} command
28998 before every command. This doubles the number of commands that need
28999 to be sent. The alternative approach is to suppress @code{-thread-select}
29000 if the selected thread in @value{GDBN} is supposed to be identical to the
29001 thread the frontend wants to operate on. However, getting this
29002 optimization right can be tricky. In particular, if the frontend
29003 sends several commands to @value{GDBN}, and one of the commands changes the
29004 selected thread, then the behaviour of subsequent commands will
29005 change. So, a frontend should either wait for response from such
29006 problematic commands, or explicitly add @code{-thread-select} for
29007 all subsequent commands. No frontend is known to do this exactly
29008 right, so it is suggested to just always pass the @samp{--thread} and
29009 @samp{--frame} options.
29011 @subsubsection Language
29013 The execution of several commands depends on which language is selected.
29014 By default, the current language (@pxref{show language}) is used.
29015 But for commands known to be language-sensitive, it is recommended
29016 to use the @samp{--language} option. This option takes one argument,
29017 which is the name of the language to use while executing the command.
29021 -data-evaluate-expression --language c "sizeof (void*)"
29026 The valid language names are the same names accepted by the
29027 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
29028 @samp{local} or @samp{unknown}.
29030 @node Asynchronous and non-stop modes
29031 @subsection Asynchronous command execution and non-stop mode
29033 On some targets, @value{GDBN} is capable of processing MI commands
29034 even while the target is running. This is called @dfn{asynchronous
29035 command execution} (@pxref{Background Execution}). The frontend may
29036 specify a preferrence for asynchronous execution using the
29037 @code{-gdb-set target-async 1} command, which should be emitted before
29038 either running the executable or attaching to the target. After the
29039 frontend has started the executable or attached to the target, it can
29040 find if asynchronous execution is enabled using the
29041 @code{-list-target-features} command.
29043 Even if @value{GDBN} can accept a command while target is running,
29044 many commands that access the target do not work when the target is
29045 running. Therefore, asynchronous command execution is most useful
29046 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
29047 it is possible to examine the state of one thread, while other threads
29050 When a given thread is running, MI commands that try to access the
29051 target in the context of that thread may not work, or may work only on
29052 some targets. In particular, commands that try to operate on thread's
29053 stack will not work, on any target. Commands that read memory, or
29054 modify breakpoints, may work or not work, depending on the target. Note
29055 that even commands that operate on global state, such as @code{print},
29056 @code{set}, and breakpoint commands, still access the target in the
29057 context of a specific thread, so frontend should try to find a
29058 stopped thread and perform the operation on that thread (using the
29059 @samp{--thread} option).
29061 Which commands will work in the context of a running thread is
29062 highly target dependent. However, the two commands
29063 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
29064 to find the state of a thread, will always work.
29066 @node Thread groups
29067 @subsection Thread groups
29068 @value{GDBN} may be used to debug several processes at the same time.
29069 On some platfroms, @value{GDBN} may support debugging of several
29070 hardware systems, each one having several cores with several different
29071 processes running on each core. This section describes the MI
29072 mechanism to support such debugging scenarios.
29074 The key observation is that regardless of the structure of the
29075 target, MI can have a global list of threads, because most commands that
29076 accept the @samp{--thread} option do not need to know what process that
29077 thread belongs to. Therefore, it is not necessary to introduce
29078 neither additional @samp{--process} option, nor an notion of the
29079 current process in the MI interface. The only strictly new feature
29080 that is required is the ability to find how the threads are grouped
29083 To allow the user to discover such grouping, and to support arbitrary
29084 hierarchy of machines/cores/processes, MI introduces the concept of a
29085 @dfn{thread group}. Thread group is a collection of threads and other
29086 thread groups. A thread group always has a string identifier, a type,
29087 and may have additional attributes specific to the type. A new
29088 command, @code{-list-thread-groups}, returns the list of top-level
29089 thread groups, which correspond to processes that @value{GDBN} is
29090 debugging at the moment. By passing an identifier of a thread group
29091 to the @code{-list-thread-groups} command, it is possible to obtain
29092 the members of specific thread group.
29094 To allow the user to easily discover processes, and other objects, he
29095 wishes to debug, a concept of @dfn{available thread group} is
29096 introduced. Available thread group is an thread group that
29097 @value{GDBN} is not debugging, but that can be attached to, using the
29098 @code{-target-attach} command. The list of available top-level thread
29099 groups can be obtained using @samp{-list-thread-groups --available}.
29100 In general, the content of a thread group may be only retrieved only
29101 after attaching to that thread group.
29103 Thread groups are related to inferiors (@pxref{Inferiors and
29104 Programs}). Each inferior corresponds to a thread group of a special
29105 type @samp{process}, and some additional operations are permitted on
29106 such thread groups.
29108 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29109 @node GDB/MI Command Syntax
29110 @section @sc{gdb/mi} Command Syntax
29113 * GDB/MI Input Syntax::
29114 * GDB/MI Output Syntax::
29117 @node GDB/MI Input Syntax
29118 @subsection @sc{gdb/mi} Input Syntax
29120 @cindex input syntax for @sc{gdb/mi}
29121 @cindex @sc{gdb/mi}, input syntax
29123 @item @var{command} @expansion{}
29124 @code{@var{cli-command} | @var{mi-command}}
29126 @item @var{cli-command} @expansion{}
29127 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
29128 @var{cli-command} is any existing @value{GDBN} CLI command.
29130 @item @var{mi-command} @expansion{}
29131 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
29132 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
29134 @item @var{token} @expansion{}
29135 "any sequence of digits"
29137 @item @var{option} @expansion{}
29138 @code{"-" @var{parameter} [ " " @var{parameter} ]}
29140 @item @var{parameter} @expansion{}
29141 @code{@var{non-blank-sequence} | @var{c-string}}
29143 @item @var{operation} @expansion{}
29144 @emph{any of the operations described in this chapter}
29146 @item @var{non-blank-sequence} @expansion{}
29147 @emph{anything, provided it doesn't contain special characters such as
29148 "-", @var{nl}, """ and of course " "}
29150 @item @var{c-string} @expansion{}
29151 @code{""" @var{seven-bit-iso-c-string-content} """}
29153 @item @var{nl} @expansion{}
29162 The CLI commands are still handled by the @sc{mi} interpreter; their
29163 output is described below.
29166 The @code{@var{token}}, when present, is passed back when the command
29170 Some @sc{mi} commands accept optional arguments as part of the parameter
29171 list. Each option is identified by a leading @samp{-} (dash) and may be
29172 followed by an optional argument parameter. Options occur first in the
29173 parameter list and can be delimited from normal parameters using
29174 @samp{--} (this is useful when some parameters begin with a dash).
29181 We want easy access to the existing CLI syntax (for debugging).
29184 We want it to be easy to spot a @sc{mi} operation.
29187 @node GDB/MI Output Syntax
29188 @subsection @sc{gdb/mi} Output Syntax
29190 @cindex output syntax of @sc{gdb/mi}
29191 @cindex @sc{gdb/mi}, output syntax
29192 The output from @sc{gdb/mi} consists of zero or more out-of-band records
29193 followed, optionally, by a single result record. This result record
29194 is for the most recent command. The sequence of output records is
29195 terminated by @samp{(gdb)}.
29197 If an input command was prefixed with a @code{@var{token}} then the
29198 corresponding output for that command will also be prefixed by that same
29202 @item @var{output} @expansion{}
29203 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
29205 @item @var{result-record} @expansion{}
29206 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
29208 @item @var{out-of-band-record} @expansion{}
29209 @code{@var{async-record} | @var{stream-record}}
29211 @item @var{async-record} @expansion{}
29212 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
29214 @item @var{exec-async-output} @expansion{}
29215 @code{[ @var{token} ] "*" @var{async-output}}
29217 @item @var{status-async-output} @expansion{}
29218 @code{[ @var{token} ] "+" @var{async-output}}
29220 @item @var{notify-async-output} @expansion{}
29221 @code{[ @var{token} ] "=" @var{async-output}}
29223 @item @var{async-output} @expansion{}
29224 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
29226 @item @var{result-class} @expansion{}
29227 @code{"done" | "running" | "connected" | "error" | "exit"}
29229 @item @var{async-class} @expansion{}
29230 @code{"stopped" | @var{others}} (where @var{others} will be added
29231 depending on the needs---this is still in development).
29233 @item @var{result} @expansion{}
29234 @code{ @var{variable} "=" @var{value}}
29236 @item @var{variable} @expansion{}
29237 @code{ @var{string} }
29239 @item @var{value} @expansion{}
29240 @code{ @var{const} | @var{tuple} | @var{list} }
29242 @item @var{const} @expansion{}
29243 @code{@var{c-string}}
29245 @item @var{tuple} @expansion{}
29246 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
29248 @item @var{list} @expansion{}
29249 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
29250 @var{result} ( "," @var{result} )* "]" }
29252 @item @var{stream-record} @expansion{}
29253 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
29255 @item @var{console-stream-output} @expansion{}
29256 @code{"~" @var{c-string}}
29258 @item @var{target-stream-output} @expansion{}
29259 @code{"@@" @var{c-string}}
29261 @item @var{log-stream-output} @expansion{}
29262 @code{"&" @var{c-string}}
29264 @item @var{nl} @expansion{}
29267 @item @var{token} @expansion{}
29268 @emph{any sequence of digits}.
29276 All output sequences end in a single line containing a period.
29279 The @code{@var{token}} is from the corresponding request. Note that
29280 for all async output, while the token is allowed by the grammar and
29281 may be output by future versions of @value{GDBN} for select async
29282 output messages, it is generally omitted. Frontends should treat
29283 all async output as reporting general changes in the state of the
29284 target and there should be no need to associate async output to any
29288 @cindex status output in @sc{gdb/mi}
29289 @var{status-async-output} contains on-going status information about the
29290 progress of a slow operation. It can be discarded. All status output is
29291 prefixed by @samp{+}.
29294 @cindex async output in @sc{gdb/mi}
29295 @var{exec-async-output} contains asynchronous state change on the target
29296 (stopped, started, disappeared). All async output is prefixed by
29300 @cindex notify output in @sc{gdb/mi}
29301 @var{notify-async-output} contains supplementary information that the
29302 client should handle (e.g., a new breakpoint information). All notify
29303 output is prefixed by @samp{=}.
29306 @cindex console output in @sc{gdb/mi}
29307 @var{console-stream-output} is output that should be displayed as is in the
29308 console. It is the textual response to a CLI command. All the console
29309 output is prefixed by @samp{~}.
29312 @cindex target output in @sc{gdb/mi}
29313 @var{target-stream-output} is the output produced by the target program.
29314 All the target output is prefixed by @samp{@@}.
29317 @cindex log output in @sc{gdb/mi}
29318 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
29319 instance messages that should be displayed as part of an error log. All
29320 the log output is prefixed by @samp{&}.
29323 @cindex list output in @sc{gdb/mi}
29324 New @sc{gdb/mi} commands should only output @var{lists} containing
29330 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
29331 details about the various output records.
29333 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29334 @node GDB/MI Compatibility with CLI
29335 @section @sc{gdb/mi} Compatibility with CLI
29337 @cindex compatibility, @sc{gdb/mi} and CLI
29338 @cindex @sc{gdb/mi}, compatibility with CLI
29340 For the developers convenience CLI commands can be entered directly,
29341 but there may be some unexpected behaviour. For example, commands
29342 that query the user will behave as if the user replied yes, breakpoint
29343 command lists are not executed and some CLI commands, such as
29344 @code{if}, @code{when} and @code{define}, prompt for further input with
29345 @samp{>}, which is not valid MI output.
29347 This feature may be removed at some stage in the future and it is
29348 recommended that front ends use the @code{-interpreter-exec} command
29349 (@pxref{-interpreter-exec}).
29351 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29352 @node GDB/MI Development and Front Ends
29353 @section @sc{gdb/mi} Development and Front Ends
29354 @cindex @sc{gdb/mi} development
29356 The application which takes the MI output and presents the state of the
29357 program being debugged to the user is called a @dfn{front end}.
29359 Although @sc{gdb/mi} is still incomplete, it is currently being used
29360 by a variety of front ends to @value{GDBN}. This makes it difficult
29361 to introduce new functionality without breaking existing usage. This
29362 section tries to minimize the problems by describing how the protocol
29365 Some changes in MI need not break a carefully designed front end, and
29366 for these the MI version will remain unchanged. The following is a
29367 list of changes that may occur within one level, so front ends should
29368 parse MI output in a way that can handle them:
29372 New MI commands may be added.
29375 New fields may be added to the output of any MI command.
29378 The range of values for fields with specified values, e.g.,
29379 @code{in_scope} (@pxref{-var-update}) may be extended.
29381 @c The format of field's content e.g type prefix, may change so parse it
29382 @c at your own risk. Yes, in general?
29384 @c The order of fields may change? Shouldn't really matter but it might
29385 @c resolve inconsistencies.
29388 If the changes are likely to break front ends, the MI version level
29389 will be increased by one. This will allow the front end to parse the
29390 output according to the MI version. Apart from mi0, new versions of
29391 @value{GDBN} will not support old versions of MI and it will be the
29392 responsibility of the front end to work with the new one.
29394 @c Starting with mi3, add a new command -mi-version that prints the MI
29397 The best way to avoid unexpected changes in MI that might break your front
29398 end is to make your project known to @value{GDBN} developers and
29399 follow development on @email{gdb@@sourceware.org} and
29400 @email{gdb-patches@@sourceware.org}.
29401 @cindex mailing lists
29403 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29404 @node GDB/MI Output Records
29405 @section @sc{gdb/mi} Output Records
29408 * GDB/MI Result Records::
29409 * GDB/MI Stream Records::
29410 * GDB/MI Async Records::
29411 * GDB/MI Breakpoint Information::
29412 * GDB/MI Frame Information::
29413 * GDB/MI Thread Information::
29414 * GDB/MI Ada Exception Information::
29417 @node GDB/MI Result Records
29418 @subsection @sc{gdb/mi} Result Records
29420 @cindex result records in @sc{gdb/mi}
29421 @cindex @sc{gdb/mi}, result records
29422 In addition to a number of out-of-band notifications, the response to a
29423 @sc{gdb/mi} command includes one of the following result indications:
29427 @item "^done" [ "," @var{results} ]
29428 The synchronous operation was successful, @code{@var{results}} are the return
29433 This result record is equivalent to @samp{^done}. Historically, it
29434 was output instead of @samp{^done} if the command has resumed the
29435 target. This behaviour is maintained for backward compatibility, but
29436 all frontends should treat @samp{^done} and @samp{^running}
29437 identically and rely on the @samp{*running} output record to determine
29438 which threads are resumed.
29442 @value{GDBN} has connected to a remote target.
29444 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
29446 The operation failed. The @code{msg=@var{c-string}} variable contains
29447 the corresponding error message.
29449 If present, the @code{code=@var{c-string}} variable provides an error
29450 code on which consumers can rely on to detect the corresponding
29451 error condition. At present, only one error code is defined:
29454 @item "undefined-command"
29455 Indicates that the command causing the error does not exist.
29460 @value{GDBN} has terminated.
29464 @node GDB/MI Stream Records
29465 @subsection @sc{gdb/mi} Stream Records
29467 @cindex @sc{gdb/mi}, stream records
29468 @cindex stream records in @sc{gdb/mi}
29469 @value{GDBN} internally maintains a number of output streams: the console, the
29470 target, and the log. The output intended for each of these streams is
29471 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29473 Each stream record begins with a unique @dfn{prefix character} which
29474 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29475 Syntax}). In addition to the prefix, each stream record contains a
29476 @code{@var{string-output}}. This is either raw text (with an implicit new
29477 line) or a quoted C string (which does not contain an implicit newline).
29480 @item "~" @var{string-output}
29481 The console output stream contains text that should be displayed in the
29482 CLI console window. It contains the textual responses to CLI commands.
29484 @item "@@" @var{string-output}
29485 The target output stream contains any textual output from the running
29486 target. This is only present when GDB's event loop is truly
29487 asynchronous, which is currently only the case for remote targets.
29489 @item "&" @var{string-output}
29490 The log stream contains debugging messages being produced by @value{GDBN}'s
29494 @node GDB/MI Async Records
29495 @subsection @sc{gdb/mi} Async Records
29497 @cindex async records in @sc{gdb/mi}
29498 @cindex @sc{gdb/mi}, async records
29499 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29500 additional changes that have occurred. Those changes can either be a
29501 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29502 target activity (e.g., target stopped).
29504 The following is the list of possible async records:
29508 @item *running,thread-id="@var{thread}"
29509 The target is now running. The @var{thread} field tells which
29510 specific thread is now running, and can be @samp{all} if all threads
29511 are running. The frontend should assume that no interaction with a
29512 running thread is possible after this notification is produced.
29513 The frontend should not assume that this notification is output
29514 only once for any command. @value{GDBN} may emit this notification
29515 several times, either for different threads, because it cannot resume
29516 all threads together, or even for a single thread, if the thread must
29517 be stepped though some code before letting it run freely.
29519 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29520 The target has stopped. The @var{reason} field can have one of the
29524 @item breakpoint-hit
29525 A breakpoint was reached.
29526 @item watchpoint-trigger
29527 A watchpoint was triggered.
29528 @item read-watchpoint-trigger
29529 A read watchpoint was triggered.
29530 @item access-watchpoint-trigger
29531 An access watchpoint was triggered.
29532 @item function-finished
29533 An -exec-finish or similar CLI command was accomplished.
29534 @item location-reached
29535 An -exec-until or similar CLI command was accomplished.
29536 @item watchpoint-scope
29537 A watchpoint has gone out of scope.
29538 @item end-stepping-range
29539 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29540 similar CLI command was accomplished.
29541 @item exited-signalled
29542 The inferior exited because of a signal.
29544 The inferior exited.
29545 @item exited-normally
29546 The inferior exited normally.
29547 @item signal-received
29548 A signal was received by the inferior.
29550 The inferior has stopped due to a library being loaded or unloaded.
29551 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29552 set or when a @code{catch load} or @code{catch unload} catchpoint is
29553 in use (@pxref{Set Catchpoints}).
29555 The inferior has forked. This is reported when @code{catch fork}
29556 (@pxref{Set Catchpoints}) has been used.
29558 The inferior has vforked. This is reported in when @code{catch vfork}
29559 (@pxref{Set Catchpoints}) has been used.
29560 @item syscall-entry
29561 The inferior entered a system call. This is reported when @code{catch
29562 syscall} (@pxref{Set Catchpoints}) has been used.
29563 @item syscall-entry
29564 The inferior returned from a system call. This is reported when
29565 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29567 The inferior called @code{exec}. This is reported when @code{catch exec}
29568 (@pxref{Set Catchpoints}) has been used.
29571 The @var{id} field identifies the thread that directly caused the stop
29572 -- for example by hitting a breakpoint. Depending on whether all-stop
29573 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29574 stop all threads, or only the thread that directly triggered the stop.
29575 If all threads are stopped, the @var{stopped} field will have the
29576 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29577 field will be a list of thread identifiers. Presently, this list will
29578 always include a single thread, but frontend should be prepared to see
29579 several threads in the list. The @var{core} field reports the
29580 processor core on which the stop event has happened. This field may be absent
29581 if such information is not available.
29583 @item =thread-group-added,id="@var{id}"
29584 @itemx =thread-group-removed,id="@var{id}"
29585 A thread group was either added or removed. The @var{id} field
29586 contains the @value{GDBN} identifier of the thread group. When a thread
29587 group is added, it generally might not be associated with a running
29588 process. When a thread group is removed, its id becomes invalid and
29589 cannot be used in any way.
29591 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29592 A thread group became associated with a running program,
29593 either because the program was just started or the thread group
29594 was attached to a program. The @var{id} field contains the
29595 @value{GDBN} identifier of the thread group. The @var{pid} field
29596 contains process identifier, specific to the operating system.
29598 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29599 A thread group is no longer associated with a running program,
29600 either because the program has exited, or because it was detached
29601 from. The @var{id} field contains the @value{GDBN} identifier of the
29602 thread group. @var{code} is the exit code of the inferior; it exists
29603 only when the inferior exited with some code.
29605 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29606 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29607 A thread either was created, or has exited. The @var{id} field
29608 contains the @value{GDBN} identifier of the thread. The @var{gid}
29609 field identifies the thread group this thread belongs to.
29611 @item =thread-selected,id="@var{id}"
29612 Informs that the selected thread was changed as result of the last
29613 command. This notification is not emitted as result of @code{-thread-select}
29614 command but is emitted whenever an MI command that is not documented
29615 to change the selected thread actually changes it. In particular,
29616 invoking, directly or indirectly (via user-defined command), the CLI
29617 @code{thread} command, will generate this notification.
29619 We suggest that in response to this notification, front ends
29620 highlight the selected thread and cause subsequent commands to apply to
29623 @item =library-loaded,...
29624 Reports that a new library file was loaded by the program. This
29625 notification has 4 fields---@var{id}, @var{target-name},
29626 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29627 opaque identifier of the library. For remote debugging case,
29628 @var{target-name} and @var{host-name} fields give the name of the
29629 library file on the target, and on the host respectively. For native
29630 debugging, both those fields have the same value. The
29631 @var{symbols-loaded} field is emitted only for backward compatibility
29632 and should not be relied on to convey any useful information. The
29633 @var{thread-group} field, if present, specifies the id of the thread
29634 group in whose context the library was loaded. If the field is
29635 absent, it means the library was loaded in the context of all present
29638 @item =library-unloaded,...
29639 Reports that a library was unloaded by the program. This notification
29640 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29641 the same meaning as for the @code{=library-loaded} notification.
29642 The @var{thread-group} field, if present, specifies the id of the
29643 thread group in whose context the library was unloaded. If the field is
29644 absent, it means the library was unloaded in the context of all present
29647 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29648 @itemx =traceframe-changed,end
29649 Reports that the trace frame was changed and its new number is
29650 @var{tfnum}. The number of the tracepoint associated with this trace
29651 frame is @var{tpnum}.
29653 @item =tsv-created,name=@var{name},initial=@var{initial}
29654 Reports that the new trace state variable @var{name} is created with
29655 initial value @var{initial}.
29657 @item =tsv-deleted,name=@var{name}
29658 @itemx =tsv-deleted
29659 Reports that the trace state variable @var{name} is deleted or all
29660 trace state variables are deleted.
29662 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29663 Reports that the trace state variable @var{name} is modified with
29664 the initial value @var{initial}. The current value @var{current} of
29665 trace state variable is optional and is reported if the current
29666 value of trace state variable is known.
29668 @item =breakpoint-created,bkpt=@{...@}
29669 @itemx =breakpoint-modified,bkpt=@{...@}
29670 @itemx =breakpoint-deleted,id=@var{number}
29671 Reports that a breakpoint was created, modified, or deleted,
29672 respectively. Only user-visible breakpoints are reported to the MI
29675 The @var{bkpt} argument is of the same form as returned by the various
29676 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29677 @var{number} is the ordinal number of the breakpoint.
29679 Note that if a breakpoint is emitted in the result record of a
29680 command, then it will not also be emitted in an async record.
29682 @item =record-started,thread-group="@var{id}"
29683 @itemx =record-stopped,thread-group="@var{id}"
29684 Execution log recording was either started or stopped on an
29685 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29686 group corresponding to the affected inferior.
29688 @item =cmd-param-changed,param=@var{param},value=@var{value}
29689 Reports that a parameter of the command @code{set @var{param}} is
29690 changed to @var{value}. In the multi-word @code{set} command,
29691 the @var{param} is the whole parameter list to @code{set} command.
29692 For example, In command @code{set check type on}, @var{param}
29693 is @code{check type} and @var{value} is @code{on}.
29695 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29696 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29697 written in an inferior. The @var{id} is the identifier of the
29698 thread group corresponding to the affected inferior. The optional
29699 @code{type="code"} part is reported if the memory written to holds
29703 @node GDB/MI Breakpoint Information
29704 @subsection @sc{gdb/mi} Breakpoint Information
29706 When @value{GDBN} reports information about a breakpoint, a
29707 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29712 The breakpoint number. For a breakpoint that represents one location
29713 of a multi-location breakpoint, this will be a dotted pair, like
29717 The type of the breakpoint. For ordinary breakpoints this will be
29718 @samp{breakpoint}, but many values are possible.
29721 If the type of the breakpoint is @samp{catchpoint}, then this
29722 indicates the exact type of catchpoint.
29725 This is the breakpoint disposition---either @samp{del}, meaning that
29726 the breakpoint will be deleted at the next stop, or @samp{keep},
29727 meaning that the breakpoint will not be deleted.
29730 This indicates whether the breakpoint is enabled, in which case the
29731 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29732 Note that this is not the same as the field @code{enable}.
29735 The address of the breakpoint. This may be a hexidecimal number,
29736 giving the address; or the string @samp{<PENDING>}, for a pending
29737 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29738 multiple locations. This field will not be present if no address can
29739 be determined. For example, a watchpoint does not have an address.
29742 If known, the function in which the breakpoint appears.
29743 If not known, this field is not present.
29746 The name of the source file which contains this function, if known.
29747 If not known, this field is not present.
29750 The full file name of the source file which contains this function, if
29751 known. If not known, this field is not present.
29754 The line number at which this breakpoint appears, if known.
29755 If not known, this field is not present.
29758 If the source file is not known, this field may be provided. If
29759 provided, this holds the address of the breakpoint, possibly followed
29763 If this breakpoint is pending, this field is present and holds the
29764 text used to set the breakpoint, as entered by the user.
29767 Where this breakpoint's condition is evaluated, either @samp{host} or
29771 If this is a thread-specific breakpoint, then this identifies the
29772 thread in which the breakpoint can trigger.
29775 If this breakpoint is restricted to a particular Ada task, then this
29776 field will hold the task identifier.
29779 If the breakpoint is conditional, this is the condition expression.
29782 The ignore count of the breakpoint.
29785 The enable count of the breakpoint.
29787 @item traceframe-usage
29790 @item static-tracepoint-marker-string-id
29791 For a static tracepoint, the name of the static tracepoint marker.
29794 For a masked watchpoint, this is the mask.
29797 A tracepoint's pass count.
29799 @item original-location
29800 The location of the breakpoint as originally specified by the user.
29801 This field is optional.
29804 The number of times the breakpoint has been hit.
29807 This field is only given for tracepoints. This is either @samp{y},
29808 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29812 Some extra data, the exact contents of which are type-dependent.
29816 For example, here is what the output of @code{-break-insert}
29817 (@pxref{GDB/MI Breakpoint Commands}) might be:
29820 -> -break-insert main
29821 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29822 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29823 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29828 @node GDB/MI Frame Information
29829 @subsection @sc{gdb/mi} Frame Information
29831 Response from many MI commands includes an information about stack
29832 frame. This information is a tuple that may have the following
29837 The level of the stack frame. The innermost frame has the level of
29838 zero. This field is always present.
29841 The name of the function corresponding to the frame. This field may
29842 be absent if @value{GDBN} is unable to determine the function name.
29845 The code address for the frame. This field is always present.
29848 The name of the source files that correspond to the frame's code
29849 address. This field may be absent.
29852 The source line corresponding to the frames' code address. This field
29856 The name of the binary file (either executable or shared library) the
29857 corresponds to the frame's code address. This field may be absent.
29861 @node GDB/MI Thread Information
29862 @subsection @sc{gdb/mi} Thread Information
29864 Whenever @value{GDBN} has to report an information about a thread, it
29865 uses a tuple with the following fields:
29869 The numeric id assigned to the thread by @value{GDBN}. This field is
29873 Target-specific string identifying the thread. This field is always present.
29876 Additional information about the thread provided by the target.
29877 It is supposed to be human-readable and not interpreted by the
29878 frontend. This field is optional.
29881 Either @samp{stopped} or @samp{running}, depending on whether the
29882 thread is presently running. This field is always present.
29885 The value of this field is an integer number of the processor core the
29886 thread was last seen on. This field is optional.
29889 @node GDB/MI Ada Exception Information
29890 @subsection @sc{gdb/mi} Ada Exception Information
29892 Whenever a @code{*stopped} record is emitted because the program
29893 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29894 @value{GDBN} provides the name of the exception that was raised via
29895 the @code{exception-name} field.
29897 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29898 @node GDB/MI Simple Examples
29899 @section Simple Examples of @sc{gdb/mi} Interaction
29900 @cindex @sc{gdb/mi}, simple examples
29902 This subsection presents several simple examples of interaction using
29903 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29904 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29905 the output received from @sc{gdb/mi}.
29907 Note the line breaks shown in the examples are here only for
29908 readability, they don't appear in the real output.
29910 @subheading Setting a Breakpoint
29912 Setting a breakpoint generates synchronous output which contains detailed
29913 information of the breakpoint.
29916 -> -break-insert main
29917 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29918 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29919 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29924 @subheading Program Execution
29926 Program execution generates asynchronous records and MI gives the
29927 reason that execution stopped.
29933 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29934 frame=@{addr="0x08048564",func="main",
29935 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29936 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29941 <- *stopped,reason="exited-normally"
29945 @subheading Quitting @value{GDBN}
29947 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29955 Please note that @samp{^exit} is printed immediately, but it might
29956 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29957 performs necessary cleanups, including killing programs being debugged
29958 or disconnecting from debug hardware, so the frontend should wait till
29959 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29960 fails to exit in reasonable time.
29962 @subheading A Bad Command
29964 Here's what happens if you pass a non-existent command:
29968 <- ^error,msg="Undefined MI command: rubbish"
29973 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29974 @node GDB/MI Command Description Format
29975 @section @sc{gdb/mi} Command Description Format
29977 The remaining sections describe blocks of commands. Each block of
29978 commands is laid out in a fashion similar to this section.
29980 @subheading Motivation
29982 The motivation for this collection of commands.
29984 @subheading Introduction
29986 A brief introduction to this collection of commands as a whole.
29988 @subheading Commands
29990 For each command in the block, the following is described:
29992 @subsubheading Synopsis
29995 -command @var{args}@dots{}
29998 @subsubheading Result
30000 @subsubheading @value{GDBN} Command
30002 The corresponding @value{GDBN} CLI command(s), if any.
30004 @subsubheading Example
30006 Example(s) formatted for readability. Some of the described commands have
30007 not been implemented yet and these are labeled N.A.@: (not available).
30010 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30011 @node GDB/MI Breakpoint Commands
30012 @section @sc{gdb/mi} Breakpoint Commands
30014 @cindex breakpoint commands for @sc{gdb/mi}
30015 @cindex @sc{gdb/mi}, breakpoint commands
30016 This section documents @sc{gdb/mi} commands for manipulating
30019 @subheading The @code{-break-after} Command
30020 @findex -break-after
30022 @subsubheading Synopsis
30025 -break-after @var{number} @var{count}
30028 The breakpoint number @var{number} is not in effect until it has been
30029 hit @var{count} times. To see how this is reflected in the output of
30030 the @samp{-break-list} command, see the description of the
30031 @samp{-break-list} command below.
30033 @subsubheading @value{GDBN} Command
30035 The corresponding @value{GDBN} command is @samp{ignore}.
30037 @subsubheading Example
30042 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30043 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30044 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30052 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30053 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30054 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30055 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30056 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30057 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30058 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30059 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30060 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30061 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
30066 @subheading The @code{-break-catch} Command
30067 @findex -break-catch
30070 @subheading The @code{-break-commands} Command
30071 @findex -break-commands
30073 @subsubheading Synopsis
30076 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
30079 Specifies the CLI commands that should be executed when breakpoint
30080 @var{number} is hit. The parameters @var{command1} to @var{commandN}
30081 are the commands. If no command is specified, any previously-set
30082 commands are cleared. @xref{Break Commands}. Typical use of this
30083 functionality is tracing a program, that is, printing of values of
30084 some variables whenever breakpoint is hit and then continuing.
30086 @subsubheading @value{GDBN} Command
30088 The corresponding @value{GDBN} command is @samp{commands}.
30090 @subsubheading Example
30095 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
30096 enabled="y",addr="0x000100d0",func="main",file="hello.c",
30097 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
30100 -break-commands 1 "print v" "continue"
30105 @subheading The @code{-break-condition} Command
30106 @findex -break-condition
30108 @subsubheading Synopsis
30111 -break-condition @var{number} @var{expr}
30114 Breakpoint @var{number} will stop the program only if the condition in
30115 @var{expr} is true. The condition becomes part of the
30116 @samp{-break-list} output (see the description of the @samp{-break-list}
30119 @subsubheading @value{GDBN} Command
30121 The corresponding @value{GDBN} command is @samp{condition}.
30123 @subsubheading Example
30127 -break-condition 1 1
30131 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30132 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30133 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30134 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30135 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30136 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30137 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30138 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30139 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30140 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
30144 @subheading The @code{-break-delete} Command
30145 @findex -break-delete
30147 @subsubheading Synopsis
30150 -break-delete ( @var{breakpoint} )+
30153 Delete the breakpoint(s) whose number(s) are specified in the argument
30154 list. This is obviously reflected in the breakpoint list.
30156 @subsubheading @value{GDBN} Command
30158 The corresponding @value{GDBN} command is @samp{delete}.
30160 @subsubheading Example
30168 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30169 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30170 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30171 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30172 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30173 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30174 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30179 @subheading The @code{-break-disable} Command
30180 @findex -break-disable
30182 @subsubheading Synopsis
30185 -break-disable ( @var{breakpoint} )+
30188 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
30189 break list is now set to @samp{n} for the named @var{breakpoint}(s).
30191 @subsubheading @value{GDBN} Command
30193 The corresponding @value{GDBN} command is @samp{disable}.
30195 @subsubheading Example
30203 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30204 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30205 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30206 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30207 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30208 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30209 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30210 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
30211 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30212 line="5",thread-groups=["i1"],times="0"@}]@}
30216 @subheading The @code{-break-enable} Command
30217 @findex -break-enable
30219 @subsubheading Synopsis
30222 -break-enable ( @var{breakpoint} )+
30225 Enable (previously disabled) @var{breakpoint}(s).
30227 @subsubheading @value{GDBN} Command
30229 The corresponding @value{GDBN} command is @samp{enable}.
30231 @subsubheading Example
30239 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30240 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30241 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30242 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30243 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30244 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30245 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30246 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30247 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
30248 line="5",thread-groups=["i1"],times="0"@}]@}
30252 @subheading The @code{-break-info} Command
30253 @findex -break-info
30255 @subsubheading Synopsis
30258 -break-info @var{breakpoint}
30262 Get information about a single breakpoint.
30264 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
30265 Information}, for details on the format of each breakpoint in the
30268 @subsubheading @value{GDBN} Command
30270 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
30272 @subsubheading Example
30275 @subheading The @code{-break-insert} Command
30276 @findex -break-insert
30278 @subsubheading Synopsis
30281 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
30282 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30283 [ -p @var{thread-id} ] [ @var{location} ]
30287 If specified, @var{location}, can be one of:
30294 @item filename:linenum
30295 @item filename:function
30299 The possible optional parameters of this command are:
30303 Insert a temporary breakpoint.
30305 Insert a hardware breakpoint.
30307 If @var{location} cannot be parsed (for example if it
30308 refers to unknown files or functions), create a pending
30309 breakpoint. Without this flag, @value{GDBN} will report
30310 an error, and won't create a breakpoint, if @var{location}
30313 Create a disabled breakpoint.
30315 Create a tracepoint. @xref{Tracepoints}. When this parameter
30316 is used together with @samp{-h}, a fast tracepoint is created.
30317 @item -c @var{condition}
30318 Make the breakpoint conditional on @var{condition}.
30319 @item -i @var{ignore-count}
30320 Initialize the @var{ignore-count}.
30321 @item -p @var{thread-id}
30322 Restrict the breakpoint to the specified @var{thread-id}.
30325 @subsubheading Result
30327 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30328 resulting breakpoint.
30330 Note: this format is open to change.
30331 @c An out-of-band breakpoint instead of part of the result?
30333 @subsubheading @value{GDBN} Command
30335 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
30336 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
30338 @subsubheading Example
30343 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
30344 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
30347 -break-insert -t foo
30348 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
30349 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
30353 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30354 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30355 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30356 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30357 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30358 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30359 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30360 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30361 addr="0x0001072c", func="main",file="recursive2.c",
30362 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
30364 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
30365 addr="0x00010774",func="foo",file="recursive2.c",
30366 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30369 @c -break-insert -r foo.*
30370 @c ~int foo(int, int);
30371 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
30372 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
30377 @subheading The @code{-dprintf-insert} Command
30378 @findex -dprintf-insert
30380 @subsubheading Synopsis
30383 -dprintf-insert [ -t ] [ -f ] [ -d ]
30384 [ -c @var{condition} ] [ -i @var{ignore-count} ]
30385 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
30390 If specified, @var{location}, can be one of:
30393 @item @var{function}
30396 @c @item @var{linenum}
30397 @item @var{filename}:@var{linenum}
30398 @item @var{filename}:function
30399 @item *@var{address}
30402 The possible optional parameters of this command are:
30406 Insert a temporary breakpoint.
30408 If @var{location} cannot be parsed (for example, if it
30409 refers to unknown files or functions), create a pending
30410 breakpoint. Without this flag, @value{GDBN} will report
30411 an error, and won't create a breakpoint, if @var{location}
30414 Create a disabled breakpoint.
30415 @item -c @var{condition}
30416 Make the breakpoint conditional on @var{condition}.
30417 @item -i @var{ignore-count}
30418 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
30419 to @var{ignore-count}.
30420 @item -p @var{thread-id}
30421 Restrict the breakpoint to the specified @var{thread-id}.
30424 @subsubheading Result
30426 @xref{GDB/MI Breakpoint Information}, for details on the format of the
30427 resulting breakpoint.
30429 @c An out-of-band breakpoint instead of part of the result?
30431 @subsubheading @value{GDBN} Command
30433 The corresponding @value{GDBN} command is @samp{dprintf}.
30435 @subsubheading Example
30439 4-dprintf-insert foo "At foo entry\n"
30440 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
30441 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
30442 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
30443 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
30444 original-location="foo"@}
30446 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
30447 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
30448 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
30449 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
30450 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
30451 original-location="mi-dprintf.c:26"@}
30455 @subheading The @code{-break-list} Command
30456 @findex -break-list
30458 @subsubheading Synopsis
30464 Displays the list of inserted breakpoints, showing the following fields:
30468 number of the breakpoint
30470 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30472 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30475 is the breakpoint enabled or no: @samp{y} or @samp{n}
30477 memory location at which the breakpoint is set
30479 logical location of the breakpoint, expressed by function name, file
30481 @item Thread-groups
30482 list of thread groups to which this breakpoint applies
30484 number of times the breakpoint has been hit
30487 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30488 @code{body} field is an empty list.
30490 @subsubheading @value{GDBN} Command
30492 The corresponding @value{GDBN} command is @samp{info break}.
30494 @subsubheading Example
30499 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30500 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30501 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30502 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30503 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30504 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30505 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30506 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30507 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30509 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30510 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30511 line="13",thread-groups=["i1"],times="0"@}]@}
30515 Here's an example of the result when there are no breakpoints:
30520 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30521 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30522 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30523 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30524 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30525 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30526 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30531 @subheading The @code{-break-passcount} Command
30532 @findex -break-passcount
30534 @subsubheading Synopsis
30537 -break-passcount @var{tracepoint-number} @var{passcount}
30540 Set the passcount for tracepoint @var{tracepoint-number} to
30541 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30542 is not a tracepoint, error is emitted. This corresponds to CLI
30543 command @samp{passcount}.
30545 @subheading The @code{-break-watch} Command
30546 @findex -break-watch
30548 @subsubheading Synopsis
30551 -break-watch [ -a | -r ]
30554 Create a watchpoint. With the @samp{-a} option it will create an
30555 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30556 read from or on a write to the memory location. With the @samp{-r}
30557 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30558 trigger only when the memory location is accessed for reading. Without
30559 either of the options, the watchpoint created is a regular watchpoint,
30560 i.e., it will trigger when the memory location is accessed for writing.
30561 @xref{Set Watchpoints, , Setting Watchpoints}.
30563 Note that @samp{-break-list} will report a single list of watchpoints and
30564 breakpoints inserted.
30566 @subsubheading @value{GDBN} Command
30568 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30571 @subsubheading Example
30573 Setting a watchpoint on a variable in the @code{main} function:
30578 ^done,wpt=@{number="2",exp="x"@}
30583 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30584 value=@{old="-268439212",new="55"@},
30585 frame=@{func="main",args=[],file="recursive2.c",
30586 fullname="/home/foo/bar/recursive2.c",line="5"@}
30590 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30591 the program execution twice: first for the variable changing value, then
30592 for the watchpoint going out of scope.
30597 ^done,wpt=@{number="5",exp="C"@}
30602 *stopped,reason="watchpoint-trigger",
30603 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30604 frame=@{func="callee4",args=[],
30605 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30606 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30611 *stopped,reason="watchpoint-scope",wpnum="5",
30612 frame=@{func="callee3",args=[@{name="strarg",
30613 value="0x11940 \"A string argument.\""@}],
30614 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30615 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30619 Listing breakpoints and watchpoints, at different points in the program
30620 execution. Note that once the watchpoint goes out of scope, it is
30626 ^done,wpt=@{number="2",exp="C"@}
30629 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30630 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30631 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30632 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30633 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30634 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30635 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30636 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30637 addr="0x00010734",func="callee4",
30638 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30639 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30641 bkpt=@{number="2",type="watchpoint",disp="keep",
30642 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30647 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30648 value=@{old="-276895068",new="3"@},
30649 frame=@{func="callee4",args=[],
30650 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30651 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30654 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30655 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30656 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30657 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30658 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30659 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30660 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30661 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30662 addr="0x00010734",func="callee4",
30663 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30664 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30666 bkpt=@{number="2",type="watchpoint",disp="keep",
30667 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30671 ^done,reason="watchpoint-scope",wpnum="2",
30672 frame=@{func="callee3",args=[@{name="strarg",
30673 value="0x11940 \"A string argument.\""@}],
30674 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30675 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30678 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30679 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30680 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30681 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30682 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30683 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30684 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30685 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30686 addr="0x00010734",func="callee4",
30687 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30688 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30689 thread-groups=["i1"],times="1"@}]@}
30694 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30695 @node GDB/MI Catchpoint Commands
30696 @section @sc{gdb/mi} Catchpoint Commands
30698 This section documents @sc{gdb/mi} commands for manipulating
30702 * Shared Library GDB/MI Catchpoint Commands::
30703 * Ada Exception GDB/MI Catchpoint Commands::
30706 @node Shared Library GDB/MI Catchpoint Commands
30707 @subsection Shared Library @sc{gdb/mi} Catchpoints
30709 @subheading The @code{-catch-load} Command
30710 @findex -catch-load
30712 @subsubheading Synopsis
30715 -catch-load [ -t ] [ -d ] @var{regexp}
30718 Add a catchpoint for library load events. If the @samp{-t} option is used,
30719 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30720 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30721 in a disabled state. The @samp{regexp} argument is a regular
30722 expression used to match the name of the loaded library.
30725 @subsubheading @value{GDBN} Command
30727 The corresponding @value{GDBN} command is @samp{catch load}.
30729 @subsubheading Example
30732 -catch-load -t foo.so
30733 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30734 what="load of library matching foo.so",catch-type="load",times="0"@}
30739 @subheading The @code{-catch-unload} Command
30740 @findex -catch-unload
30742 @subsubheading Synopsis
30745 -catch-unload [ -t ] [ -d ] @var{regexp}
30748 Add a catchpoint for library unload events. If the @samp{-t} option is
30749 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30750 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30751 created in a disabled state. The @samp{regexp} argument is a regular
30752 expression used to match the name of the unloaded library.
30754 @subsubheading @value{GDBN} Command
30756 The corresponding @value{GDBN} command is @samp{catch unload}.
30758 @subsubheading Example
30761 -catch-unload -d bar.so
30762 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30763 what="load of library matching bar.so",catch-type="unload",times="0"@}
30767 @node Ada Exception GDB/MI Catchpoint Commands
30768 @subsection Ada Exception @sc{gdb/mi} Catchpoints
30770 The following @sc{gdb/mi} commands can be used to create catchpoints
30771 that stop the execution when Ada exceptions are being raised.
30773 @subheading The @code{-catch-assert} Command
30774 @findex -catch-assert
30776 @subsubheading Synopsis
30779 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
30782 Add a catchpoint for failed Ada assertions.
30784 The possible optional parameters for this command are:
30787 @item -c @var{condition}
30788 Make the catchpoint conditional on @var{condition}.
30790 Create a disabled catchpoint.
30792 Create a temporary catchpoint.
30795 @subsubheading @value{GDBN} Command
30797 The corresponding @value{GDBN} command is @samp{catch assert}.
30799 @subsubheading Example
30803 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
30804 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
30805 thread-groups=["i1"],times="0",
30806 original-location="__gnat_debug_raise_assert_failure"@}
30810 @subheading The @code{-catch-exception} Command
30811 @findex -catch-exception
30813 @subsubheading Synopsis
30816 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
30820 Add a catchpoint stopping when Ada exceptions are raised.
30821 By default, the command stops the program when any Ada exception
30822 gets raised. But it is also possible, by using some of the
30823 optional parameters described below, to create more selective
30826 The possible optional parameters for this command are:
30829 @item -c @var{condition}
30830 Make the catchpoint conditional on @var{condition}.
30832 Create a disabled catchpoint.
30833 @item -e @var{exception-name}
30834 Only stop when @var{exception-name} is raised. This option cannot
30835 be used combined with @samp{-u}.
30837 Create a temporary catchpoint.
30839 Stop only when an unhandled exception gets raised. This option
30840 cannot be used combined with @samp{-e}.
30843 @subsubheading @value{GDBN} Command
30845 The corresponding @value{GDBN} commands are @samp{catch exception}
30846 and @samp{catch exception unhandled}.
30848 @subsubheading Example
30851 -catch-exception -e Program_Error
30852 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
30853 enabled="y",addr="0x0000000000404874",
30854 what="`Program_Error' Ada exception", thread-groups=["i1"],
30855 times="0",original-location="__gnat_debug_raise_exception"@}
30859 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30860 @node GDB/MI Program Context
30861 @section @sc{gdb/mi} Program Context
30863 @subheading The @code{-exec-arguments} Command
30864 @findex -exec-arguments
30867 @subsubheading Synopsis
30870 -exec-arguments @var{args}
30873 Set the inferior program arguments, to be used in the next
30876 @subsubheading @value{GDBN} Command
30878 The corresponding @value{GDBN} command is @samp{set args}.
30880 @subsubheading Example
30884 -exec-arguments -v word
30891 @subheading The @code{-exec-show-arguments} Command
30892 @findex -exec-show-arguments
30894 @subsubheading Synopsis
30897 -exec-show-arguments
30900 Print the arguments of the program.
30902 @subsubheading @value{GDBN} Command
30904 The corresponding @value{GDBN} command is @samp{show args}.
30906 @subsubheading Example
30911 @subheading The @code{-environment-cd} Command
30912 @findex -environment-cd
30914 @subsubheading Synopsis
30917 -environment-cd @var{pathdir}
30920 Set @value{GDBN}'s working directory.
30922 @subsubheading @value{GDBN} Command
30924 The corresponding @value{GDBN} command is @samp{cd}.
30926 @subsubheading Example
30930 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30936 @subheading The @code{-environment-directory} Command
30937 @findex -environment-directory
30939 @subsubheading Synopsis
30942 -environment-directory [ -r ] [ @var{pathdir} ]+
30945 Add directories @var{pathdir} to beginning of search path for source files.
30946 If the @samp{-r} option is used, the search path is reset to the default
30947 search path. If directories @var{pathdir} are supplied in addition to the
30948 @samp{-r} option, the search path is first reset and then addition
30950 Multiple directories may be specified, separated by blanks. Specifying
30951 multiple directories in a single command
30952 results in the directories added to the beginning of the
30953 search path in the same order they were presented in the command.
30954 If blanks are needed as
30955 part of a directory name, double-quotes should be used around
30956 the name. In the command output, the path will show up separated
30957 by the system directory-separator character. The directory-separator
30958 character must not be used
30959 in any directory name.
30960 If no directories are specified, the current search path is displayed.
30962 @subsubheading @value{GDBN} Command
30964 The corresponding @value{GDBN} command is @samp{dir}.
30966 @subsubheading Example
30970 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30971 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30973 -environment-directory ""
30974 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30976 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30977 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30979 -environment-directory -r
30980 ^done,source-path="$cdir:$cwd"
30985 @subheading The @code{-environment-path} Command
30986 @findex -environment-path
30988 @subsubheading Synopsis
30991 -environment-path [ -r ] [ @var{pathdir} ]+
30994 Add directories @var{pathdir} to beginning of search path for object files.
30995 If the @samp{-r} option is used, the search path is reset to the original
30996 search path that existed at gdb start-up. If directories @var{pathdir} are
30997 supplied in addition to the
30998 @samp{-r} option, the search path is first reset and then addition
31000 Multiple directories may be specified, separated by blanks. Specifying
31001 multiple directories in a single command
31002 results in the directories added to the beginning of the
31003 search path in the same order they were presented in the command.
31004 If blanks are needed as
31005 part of a directory name, double-quotes should be used around
31006 the name. In the command output, the path will show up separated
31007 by the system directory-separator character. The directory-separator
31008 character must not be used
31009 in any directory name.
31010 If no directories are specified, the current path is displayed.
31013 @subsubheading @value{GDBN} Command
31015 The corresponding @value{GDBN} command is @samp{path}.
31017 @subsubheading Example
31022 ^done,path="/usr/bin"
31024 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
31025 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
31027 -environment-path -r /usr/local/bin
31028 ^done,path="/usr/local/bin:/usr/bin"
31033 @subheading The @code{-environment-pwd} Command
31034 @findex -environment-pwd
31036 @subsubheading Synopsis
31042 Show the current working directory.
31044 @subsubheading @value{GDBN} Command
31046 The corresponding @value{GDBN} command is @samp{pwd}.
31048 @subsubheading Example
31053 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
31057 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31058 @node GDB/MI Thread Commands
31059 @section @sc{gdb/mi} Thread Commands
31062 @subheading The @code{-thread-info} Command
31063 @findex -thread-info
31065 @subsubheading Synopsis
31068 -thread-info [ @var{thread-id} ]
31071 Reports information about either a specific thread, if
31072 the @var{thread-id} parameter is present, or about all
31073 threads. When printing information about all threads,
31074 also reports the current thread.
31076 @subsubheading @value{GDBN} Command
31078 The @samp{info thread} command prints the same information
31081 @subsubheading Result
31083 The result is a list of threads. The following attributes are
31084 defined for a given thread:
31088 This field exists only for the current thread. It has the value @samp{*}.
31091 The identifier that @value{GDBN} uses to refer to the thread.
31094 The identifier that the target uses to refer to the thread.
31097 Extra information about the thread, in a target-specific format. This
31101 The name of the thread. If the user specified a name using the
31102 @code{thread name} command, then this name is given. Otherwise, if
31103 @value{GDBN} can extract the thread name from the target, then that
31104 name is given. If @value{GDBN} cannot find the thread name, then this
31108 The stack frame currently executing in the thread.
31111 The thread's state. The @samp{state} field may have the following
31116 The thread is stopped. Frame information is available for stopped
31120 The thread is running. There's no frame information for running
31126 If @value{GDBN} can find the CPU core on which this thread is running,
31127 then this field is the core identifier. This field is optional.
31131 @subsubheading Example
31136 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31137 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
31138 args=[]@},state="running"@},
31139 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31140 frame=@{level="0",addr="0x0804891f",func="foo",
31141 args=[@{name="i",value="10"@}],
31142 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
31143 state="running"@}],
31144 current-thread-id="1"
31148 @subheading The @code{-thread-list-ids} Command
31149 @findex -thread-list-ids
31151 @subsubheading Synopsis
31157 Produces a list of the currently known @value{GDBN} thread ids. At the
31158 end of the list it also prints the total number of such threads.
31160 This command is retained for historical reasons, the
31161 @code{-thread-info} command should be used instead.
31163 @subsubheading @value{GDBN} Command
31165 Part of @samp{info threads} supplies the same information.
31167 @subsubheading Example
31172 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31173 current-thread-id="1",number-of-threads="3"
31178 @subheading The @code{-thread-select} Command
31179 @findex -thread-select
31181 @subsubheading Synopsis
31184 -thread-select @var{threadnum}
31187 Make @var{threadnum} the current thread. It prints the number of the new
31188 current thread, and the topmost frame for that thread.
31190 This command is deprecated in favor of explicitly using the
31191 @samp{--thread} option to each command.
31193 @subsubheading @value{GDBN} Command
31195 The corresponding @value{GDBN} command is @samp{thread}.
31197 @subsubheading Example
31204 *stopped,reason="end-stepping-range",thread-id="2",line="187",
31205 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
31209 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
31210 number-of-threads="3"
31213 ^done,new-thread-id="3",
31214 frame=@{level="0",func="vprintf",
31215 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
31216 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
31220 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31221 @node GDB/MI Ada Tasking Commands
31222 @section @sc{gdb/mi} Ada Tasking Commands
31224 @subheading The @code{-ada-task-info} Command
31225 @findex -ada-task-info
31227 @subsubheading Synopsis
31230 -ada-task-info [ @var{task-id} ]
31233 Reports information about either a specific Ada task, if the
31234 @var{task-id} parameter is present, or about all Ada tasks.
31236 @subsubheading @value{GDBN} Command
31238 The @samp{info tasks} command prints the same information
31239 about all Ada tasks (@pxref{Ada Tasks}).
31241 @subsubheading Result
31243 The result is a table of Ada tasks. The following columns are
31244 defined for each Ada task:
31248 This field exists only for the current thread. It has the value @samp{*}.
31251 The identifier that @value{GDBN} uses to refer to the Ada task.
31254 The identifier that the target uses to refer to the Ada task.
31257 The identifier of the thread corresponding to the Ada task.
31259 This field should always exist, as Ada tasks are always implemented
31260 on top of a thread. But if @value{GDBN} cannot find this corresponding
31261 thread for any reason, the field is omitted.
31264 This field exists only when the task was created by another task.
31265 In this case, it provides the ID of the parent task.
31268 The base priority of the task.
31271 The current state of the task. For a detailed description of the
31272 possible states, see @ref{Ada Tasks}.
31275 The name of the task.
31279 @subsubheading Example
31283 ^done,tasks=@{nr_rows="3",nr_cols="8",
31284 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
31285 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
31286 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
31287 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
31288 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
31289 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
31290 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
31291 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
31292 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
31293 state="Child Termination Wait",name="main_task"@}]@}
31297 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31298 @node GDB/MI Program Execution
31299 @section @sc{gdb/mi} Program Execution
31301 These are the asynchronous commands which generate the out-of-band
31302 record @samp{*stopped}. Currently @value{GDBN} only really executes
31303 asynchronously with remote targets and this interaction is mimicked in
31306 @subheading The @code{-exec-continue} Command
31307 @findex -exec-continue
31309 @subsubheading Synopsis
31312 -exec-continue [--reverse] [--all|--thread-group N]
31315 Resumes the execution of the inferior program, which will continue
31316 to execute until it reaches a debugger stop event. If the
31317 @samp{--reverse} option is specified, execution resumes in reverse until
31318 it reaches a stop event. Stop events may include
31321 breakpoints or watchpoints
31323 signals or exceptions
31325 the end of the process (or its beginning under @samp{--reverse})
31327 the end or beginning of a replay log if one is being used.
31329 In all-stop mode (@pxref{All-Stop
31330 Mode}), may resume only one thread, or all threads, depending on the
31331 value of the @samp{scheduler-locking} variable. If @samp{--all} is
31332 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
31333 ignored in all-stop mode. If the @samp{--thread-group} options is
31334 specified, then all threads in that thread group are resumed.
31336 @subsubheading @value{GDBN} Command
31338 The corresponding @value{GDBN} corresponding is @samp{continue}.
31340 @subsubheading Example
31347 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
31348 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
31354 @subheading The @code{-exec-finish} Command
31355 @findex -exec-finish
31357 @subsubheading Synopsis
31360 -exec-finish [--reverse]
31363 Resumes the execution of the inferior program until the current
31364 function is exited. Displays the results returned by the function.
31365 If the @samp{--reverse} option is specified, resumes the reverse
31366 execution of the inferior program until the point where current
31367 function was called.
31369 @subsubheading @value{GDBN} Command
31371 The corresponding @value{GDBN} command is @samp{finish}.
31373 @subsubheading Example
31375 Function returning @code{void}.
31382 *stopped,reason="function-finished",frame=@{func="main",args=[],
31383 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
31387 Function returning other than @code{void}. The name of the internal
31388 @value{GDBN} variable storing the result is printed, together with the
31395 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
31396 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
31397 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31398 gdb-result-var="$1",return-value="0"
31403 @subheading The @code{-exec-interrupt} Command
31404 @findex -exec-interrupt
31406 @subsubheading Synopsis
31409 -exec-interrupt [--all|--thread-group N]
31412 Interrupts the background execution of the target. Note how the token
31413 associated with the stop message is the one for the execution command
31414 that has been interrupted. The token for the interrupt itself only
31415 appears in the @samp{^done} output. If the user is trying to
31416 interrupt a non-running program, an error message will be printed.
31418 Note that when asynchronous execution is enabled, this command is
31419 asynchronous just like other execution commands. That is, first the
31420 @samp{^done} response will be printed, and the target stop will be
31421 reported after that using the @samp{*stopped} notification.
31423 In non-stop mode, only the context thread is interrupted by default.
31424 All threads (in all inferiors) will be interrupted if the
31425 @samp{--all} option is specified. If the @samp{--thread-group}
31426 option is specified, all threads in that group will be interrupted.
31428 @subsubheading @value{GDBN} Command
31430 The corresponding @value{GDBN} command is @samp{interrupt}.
31432 @subsubheading Example
31443 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
31444 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
31445 fullname="/home/foo/bar/try.c",line="13"@}
31450 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
31454 @subheading The @code{-exec-jump} Command
31457 @subsubheading Synopsis
31460 -exec-jump @var{location}
31463 Resumes execution of the inferior program at the location specified by
31464 parameter. @xref{Specify Location}, for a description of the
31465 different forms of @var{location}.
31467 @subsubheading @value{GDBN} Command
31469 The corresponding @value{GDBN} command is @samp{jump}.
31471 @subsubheading Example
31474 -exec-jump foo.c:10
31475 *running,thread-id="all"
31480 @subheading The @code{-exec-next} Command
31483 @subsubheading Synopsis
31486 -exec-next [--reverse]
31489 Resumes execution of the inferior program, stopping when the beginning
31490 of the next source line is reached.
31492 If the @samp{--reverse} option is specified, resumes reverse execution
31493 of the inferior program, stopping at the beginning of the previous
31494 source line. If you issue this command on the first line of a
31495 function, it will take you back to the caller of that function, to the
31496 source line where the function was called.
31499 @subsubheading @value{GDBN} Command
31501 The corresponding @value{GDBN} command is @samp{next}.
31503 @subsubheading Example
31509 *stopped,reason="end-stepping-range",line="8",file="hello.c"
31514 @subheading The @code{-exec-next-instruction} Command
31515 @findex -exec-next-instruction
31517 @subsubheading Synopsis
31520 -exec-next-instruction [--reverse]
31523 Executes one machine instruction. If the instruction is a function
31524 call, continues until the function returns. If the program stops at an
31525 instruction in the middle of a source line, the address will be
31528 If the @samp{--reverse} option is specified, resumes reverse execution
31529 of the inferior program, stopping at the previous instruction. If the
31530 previously executed instruction was a return from another function,
31531 it will continue to execute in reverse until the call to that function
31532 (from the current stack frame) is reached.
31534 @subsubheading @value{GDBN} Command
31536 The corresponding @value{GDBN} command is @samp{nexti}.
31538 @subsubheading Example
31542 -exec-next-instruction
31546 *stopped,reason="end-stepping-range",
31547 addr="0x000100d4",line="5",file="hello.c"
31552 @subheading The @code{-exec-return} Command
31553 @findex -exec-return
31555 @subsubheading Synopsis
31561 Makes current function return immediately. Doesn't execute the inferior.
31562 Displays the new current frame.
31564 @subsubheading @value{GDBN} Command
31566 The corresponding @value{GDBN} command is @samp{return}.
31568 @subsubheading Example
31572 200-break-insert callee4
31573 200^done,bkpt=@{number="1",addr="0x00010734",
31574 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31579 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31580 frame=@{func="callee4",args=[],
31581 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31582 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31588 111^done,frame=@{level="0",func="callee3",
31589 args=[@{name="strarg",
31590 value="0x11940 \"A string argument.\""@}],
31591 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31592 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31597 @subheading The @code{-exec-run} Command
31600 @subsubheading Synopsis
31603 -exec-run [ --all | --thread-group N ] [ --start ]
31606 Starts execution of the inferior from the beginning. The inferior
31607 executes until either a breakpoint is encountered or the program
31608 exits. In the latter case the output will include an exit code, if
31609 the program has exited exceptionally.
31611 When neither the @samp{--all} nor the @samp{--thread-group} option
31612 is specified, the current inferior is started. If the
31613 @samp{--thread-group} option is specified, it should refer to a thread
31614 group of type @samp{process}, and that thread group will be started.
31615 If the @samp{--all} option is specified, then all inferiors will be started.
31617 Using the @samp{--start} option instructs the debugger to stop
31618 the execution at the start of the inferior's main subprogram,
31619 following the same behavior as the @code{start} command
31620 (@pxref{Starting}).
31622 @subsubheading @value{GDBN} Command
31624 The corresponding @value{GDBN} command is @samp{run}.
31626 @subsubheading Examples
31631 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31636 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31637 frame=@{func="main",args=[],file="recursive2.c",
31638 fullname="/home/foo/bar/recursive2.c",line="4"@}
31643 Program exited normally:
31651 *stopped,reason="exited-normally"
31656 Program exited exceptionally:
31664 *stopped,reason="exited",exit-code="01"
31668 Another way the program can terminate is if it receives a signal such as
31669 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31673 *stopped,reason="exited-signalled",signal-name="SIGINT",
31674 signal-meaning="Interrupt"
31678 @c @subheading -exec-signal
31681 @subheading The @code{-exec-step} Command
31684 @subsubheading Synopsis
31687 -exec-step [--reverse]
31690 Resumes execution of the inferior program, stopping when the beginning
31691 of the next source line is reached, if the next source line is not a
31692 function call. If it is, stop at the first instruction of the called
31693 function. If the @samp{--reverse} option is specified, resumes reverse
31694 execution of the inferior program, stopping at the beginning of the
31695 previously executed source line.
31697 @subsubheading @value{GDBN} Command
31699 The corresponding @value{GDBN} command is @samp{step}.
31701 @subsubheading Example
31703 Stepping into a function:
31709 *stopped,reason="end-stepping-range",
31710 frame=@{func="foo",args=[@{name="a",value="10"@},
31711 @{name="b",value="0"@}],file="recursive2.c",
31712 fullname="/home/foo/bar/recursive2.c",line="11"@}
31722 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31727 @subheading The @code{-exec-step-instruction} Command
31728 @findex -exec-step-instruction
31730 @subsubheading Synopsis
31733 -exec-step-instruction [--reverse]
31736 Resumes the inferior which executes one machine instruction. If the
31737 @samp{--reverse} option is specified, resumes reverse execution of the
31738 inferior program, stopping at the previously executed instruction.
31739 The output, once @value{GDBN} has stopped, will vary depending on
31740 whether we have stopped in the middle of a source line or not. In the
31741 former case, the address at which the program stopped will be printed
31744 @subsubheading @value{GDBN} Command
31746 The corresponding @value{GDBN} command is @samp{stepi}.
31748 @subsubheading Example
31752 -exec-step-instruction
31756 *stopped,reason="end-stepping-range",
31757 frame=@{func="foo",args=[],file="try.c",
31758 fullname="/home/foo/bar/try.c",line="10"@}
31760 -exec-step-instruction
31764 *stopped,reason="end-stepping-range",
31765 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31766 fullname="/home/foo/bar/try.c",line="10"@}
31771 @subheading The @code{-exec-until} Command
31772 @findex -exec-until
31774 @subsubheading Synopsis
31777 -exec-until [ @var{location} ]
31780 Executes the inferior until the @var{location} specified in the
31781 argument is reached. If there is no argument, the inferior executes
31782 until a source line greater than the current one is reached. The
31783 reason for stopping in this case will be @samp{location-reached}.
31785 @subsubheading @value{GDBN} Command
31787 The corresponding @value{GDBN} command is @samp{until}.
31789 @subsubheading Example
31793 -exec-until recursive2.c:6
31797 *stopped,reason="location-reached",frame=@{func="main",args=[],
31798 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31803 @subheading -file-clear
31804 Is this going away????
31807 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31808 @node GDB/MI Stack Manipulation
31809 @section @sc{gdb/mi} Stack Manipulation Commands
31811 @subheading The @code{-enable-frame-filters} Command
31812 @findex -enable-frame-filters
31815 -enable-frame-filters
31818 @value{GDBN} allows Python-based frame filters to affect the output of
31819 the MI commands relating to stack traces. As there is no way to
31820 implement this in a fully backward-compatible way, a front end must
31821 request that this functionality be enabled.
31823 Once enabled, this feature cannot be disabled.
31825 Note that if Python support has not been compiled into @value{GDBN},
31826 this command will still succeed (and do nothing).
31828 @subheading The @code{-stack-info-frame} Command
31829 @findex -stack-info-frame
31831 @subsubheading Synopsis
31837 Get info on the selected frame.
31839 @subsubheading @value{GDBN} Command
31841 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31842 (without arguments).
31844 @subsubheading Example
31849 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31850 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31851 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31855 @subheading The @code{-stack-info-depth} Command
31856 @findex -stack-info-depth
31858 @subsubheading Synopsis
31861 -stack-info-depth [ @var{max-depth} ]
31864 Return the depth of the stack. If the integer argument @var{max-depth}
31865 is specified, do not count beyond @var{max-depth} frames.
31867 @subsubheading @value{GDBN} Command
31869 There's no equivalent @value{GDBN} command.
31871 @subsubheading Example
31873 For a stack with frame levels 0 through 11:
31880 -stack-info-depth 4
31883 -stack-info-depth 12
31886 -stack-info-depth 11
31889 -stack-info-depth 13
31894 @anchor{-stack-list-arguments}
31895 @subheading The @code{-stack-list-arguments} Command
31896 @findex -stack-list-arguments
31898 @subsubheading Synopsis
31901 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31902 [ @var{low-frame} @var{high-frame} ]
31905 Display a list of the arguments for the frames between @var{low-frame}
31906 and @var{high-frame} (inclusive). If @var{low-frame} and
31907 @var{high-frame} are not provided, list the arguments for the whole
31908 call stack. If the two arguments are equal, show the single frame
31909 at the corresponding level. It is an error if @var{low-frame} is
31910 larger than the actual number of frames. On the other hand,
31911 @var{high-frame} may be larger than the actual number of frames, in
31912 which case only existing frames will be returned.
31914 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31915 the variables; if it is 1 or @code{--all-values}, print also their
31916 values; and if it is 2 or @code{--simple-values}, print the name,
31917 type and value for simple data types, and the name and type for arrays,
31918 structures and unions. If the option @code{--no-frame-filters} is
31919 supplied, then Python frame filters will not be executed.
31921 If the @code{--skip-unavailable} option is specified, arguments that
31922 are not available are not listed. Partially available arguments
31923 are still displayed, however.
31925 Use of this command to obtain arguments in a single frame is
31926 deprecated in favor of the @samp{-stack-list-variables} command.
31928 @subsubheading @value{GDBN} Command
31930 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31931 @samp{gdb_get_args} command which partially overlaps with the
31932 functionality of @samp{-stack-list-arguments}.
31934 @subsubheading Example
31941 frame=@{level="0",addr="0x00010734",func="callee4",
31942 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31943 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31944 frame=@{level="1",addr="0x0001076c",func="callee3",
31945 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31946 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31947 frame=@{level="2",addr="0x0001078c",func="callee2",
31948 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31949 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31950 frame=@{level="3",addr="0x000107b4",func="callee1",
31951 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31952 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31953 frame=@{level="4",addr="0x000107e0",func="main",
31954 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31955 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31957 -stack-list-arguments 0
31960 frame=@{level="0",args=[]@},
31961 frame=@{level="1",args=[name="strarg"]@},
31962 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31963 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31964 frame=@{level="4",args=[]@}]
31966 -stack-list-arguments 1
31969 frame=@{level="0",args=[]@},
31971 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31972 frame=@{level="2",args=[
31973 @{name="intarg",value="2"@},
31974 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31975 @{frame=@{level="3",args=[
31976 @{name="intarg",value="2"@},
31977 @{name="strarg",value="0x11940 \"A string argument.\""@},
31978 @{name="fltarg",value="3.5"@}]@},
31979 frame=@{level="4",args=[]@}]
31981 -stack-list-arguments 0 2 2
31982 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31984 -stack-list-arguments 1 2 2
31985 ^done,stack-args=[frame=@{level="2",
31986 args=[@{name="intarg",value="2"@},
31987 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31991 @c @subheading -stack-list-exception-handlers
31994 @anchor{-stack-list-frames}
31995 @subheading The @code{-stack-list-frames} Command
31996 @findex -stack-list-frames
31998 @subsubheading Synopsis
32001 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
32004 List the frames currently on the stack. For each frame it displays the
32009 The frame number, 0 being the topmost frame, i.e., the innermost function.
32011 The @code{$pc} value for that frame.
32015 File name of the source file where the function lives.
32016 @item @var{fullname}
32017 The full file name of the source file where the function lives.
32019 Line number corresponding to the @code{$pc}.
32021 The shared library where this function is defined. This is only given
32022 if the frame's function is not known.
32025 If invoked without arguments, this command prints a backtrace for the
32026 whole stack. If given two integer arguments, it shows the frames whose
32027 levels are between the two arguments (inclusive). If the two arguments
32028 are equal, it shows the single frame at the corresponding level. It is
32029 an error if @var{low-frame} is larger than the actual number of
32030 frames. On the other hand, @var{high-frame} may be larger than the
32031 actual number of frames, in which case only existing frames will be
32032 returned. If the option @code{--no-frame-filters} is supplied, then
32033 Python frame filters will not be executed.
32035 @subsubheading @value{GDBN} Command
32037 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
32039 @subsubheading Example
32041 Full stack backtrace:
32047 [frame=@{level="0",addr="0x0001076c",func="foo",
32048 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
32049 frame=@{level="1",addr="0x000107a4",func="foo",
32050 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32051 frame=@{level="2",addr="0x000107a4",func="foo",
32052 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32053 frame=@{level="3",addr="0x000107a4",func="foo",
32054 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32055 frame=@{level="4",addr="0x000107a4",func="foo",
32056 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32057 frame=@{level="5",addr="0x000107a4",func="foo",
32058 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32059 frame=@{level="6",addr="0x000107a4",func="foo",
32060 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32061 frame=@{level="7",addr="0x000107a4",func="foo",
32062 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32063 frame=@{level="8",addr="0x000107a4",func="foo",
32064 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32065 frame=@{level="9",addr="0x000107a4",func="foo",
32066 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32067 frame=@{level="10",addr="0x000107a4",func="foo",
32068 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32069 frame=@{level="11",addr="0x00010738",func="main",
32070 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
32074 Show frames between @var{low_frame} and @var{high_frame}:
32078 -stack-list-frames 3 5
32080 [frame=@{level="3",addr="0x000107a4",func="foo",
32081 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32082 frame=@{level="4",addr="0x000107a4",func="foo",
32083 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
32084 frame=@{level="5",addr="0x000107a4",func="foo",
32085 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32089 Show a single frame:
32093 -stack-list-frames 3 3
32095 [frame=@{level="3",addr="0x000107a4",func="foo",
32096 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
32101 @subheading The @code{-stack-list-locals} Command
32102 @findex -stack-list-locals
32103 @anchor{-stack-list-locals}
32105 @subsubheading Synopsis
32108 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32111 Display the local variable names for the selected frame. If
32112 @var{print-values} is 0 or @code{--no-values}, print only the names of
32113 the variables; if it is 1 or @code{--all-values}, print also their
32114 values; and if it is 2 or @code{--simple-values}, print the name,
32115 type and value for simple data types, and the name and type for arrays,
32116 structures and unions. In this last case, a frontend can immediately
32117 display the value of simple data types and create variable objects for
32118 other data types when the user wishes to explore their values in
32119 more detail. If the option @code{--no-frame-filters} is supplied, then
32120 Python frame filters will not be executed.
32122 If the @code{--skip-unavailable} option is specified, local variables
32123 that are not available are not listed. Partially available local
32124 variables are still displayed, however.
32126 This command is deprecated in favor of the
32127 @samp{-stack-list-variables} command.
32129 @subsubheading @value{GDBN} Command
32131 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
32133 @subsubheading Example
32137 -stack-list-locals 0
32138 ^done,locals=[name="A",name="B",name="C"]
32140 -stack-list-locals --all-values
32141 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
32142 @{name="C",value="@{1, 2, 3@}"@}]
32143 -stack-list-locals --simple-values
32144 ^done,locals=[@{name="A",type="int",value="1"@},
32145 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
32149 @anchor{-stack-list-variables}
32150 @subheading The @code{-stack-list-variables} Command
32151 @findex -stack-list-variables
32153 @subsubheading Synopsis
32156 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
32159 Display the names of local variables and function arguments for the selected frame. If
32160 @var{print-values} is 0 or @code{--no-values}, print only the names of
32161 the variables; if it is 1 or @code{--all-values}, print also their
32162 values; and if it is 2 or @code{--simple-values}, print the name,
32163 type and value for simple data types, and the name and type for arrays,
32164 structures and unions. If the option @code{--no-frame-filters} is
32165 supplied, then Python frame filters will not be executed.
32167 If the @code{--skip-unavailable} option is specified, local variables
32168 and arguments that are not available are not listed. Partially
32169 available arguments and local variables are still displayed, however.
32171 @subsubheading Example
32175 -stack-list-variables --thread 1 --frame 0 --all-values
32176 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
32181 @subheading The @code{-stack-select-frame} Command
32182 @findex -stack-select-frame
32184 @subsubheading Synopsis
32187 -stack-select-frame @var{framenum}
32190 Change the selected frame. Select a different frame @var{framenum} on
32193 This command in deprecated in favor of passing the @samp{--frame}
32194 option to every command.
32196 @subsubheading @value{GDBN} Command
32198 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
32199 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
32201 @subsubheading Example
32205 -stack-select-frame 2
32210 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32211 @node GDB/MI Variable Objects
32212 @section @sc{gdb/mi} Variable Objects
32216 @subheading Motivation for Variable Objects in @sc{gdb/mi}
32218 For the implementation of a variable debugger window (locals, watched
32219 expressions, etc.), we are proposing the adaptation of the existing code
32220 used by @code{Insight}.
32222 The two main reasons for that are:
32226 It has been proven in practice (it is already on its second generation).
32229 It will shorten development time (needless to say how important it is
32233 The original interface was designed to be used by Tcl code, so it was
32234 slightly changed so it could be used through @sc{gdb/mi}. This section
32235 describes the @sc{gdb/mi} operations that will be available and gives some
32236 hints about their use.
32238 @emph{Note}: In addition to the set of operations described here, we
32239 expect the @sc{gui} implementation of a variable window to require, at
32240 least, the following operations:
32243 @item @code{-gdb-show} @code{output-radix}
32244 @item @code{-stack-list-arguments}
32245 @item @code{-stack-list-locals}
32246 @item @code{-stack-select-frame}
32251 @subheading Introduction to Variable Objects
32253 @cindex variable objects in @sc{gdb/mi}
32255 Variable objects are "object-oriented" MI interface for examining and
32256 changing values of expressions. Unlike some other MI interfaces that
32257 work with expressions, variable objects are specifically designed for
32258 simple and efficient presentation in the frontend. A variable object
32259 is identified by string name. When a variable object is created, the
32260 frontend specifies the expression for that variable object. The
32261 expression can be a simple variable, or it can be an arbitrary complex
32262 expression, and can even involve CPU registers. After creating a
32263 variable object, the frontend can invoke other variable object
32264 operations---for example to obtain or change the value of a variable
32265 object, or to change display format.
32267 Variable objects have hierarchical tree structure. Any variable object
32268 that corresponds to a composite type, such as structure in C, has
32269 a number of child variable objects, for example corresponding to each
32270 element of a structure. A child variable object can itself have
32271 children, recursively. Recursion ends when we reach
32272 leaf variable objects, which always have built-in types. Child variable
32273 objects are created only by explicit request, so if a frontend
32274 is not interested in the children of a particular variable object, no
32275 child will be created.
32277 For a leaf variable object it is possible to obtain its value as a
32278 string, or set the value from a string. String value can be also
32279 obtained for a non-leaf variable object, but it's generally a string
32280 that only indicates the type of the object, and does not list its
32281 contents. Assignment to a non-leaf variable object is not allowed.
32283 A frontend does not need to read the values of all variable objects each time
32284 the program stops. Instead, MI provides an update command that lists all
32285 variable objects whose values has changed since the last update
32286 operation. This considerably reduces the amount of data that must
32287 be transferred to the frontend. As noted above, children variable
32288 objects are created on demand, and only leaf variable objects have a
32289 real value. As result, gdb will read target memory only for leaf
32290 variables that frontend has created.
32292 The automatic update is not always desirable. For example, a frontend
32293 might want to keep a value of some expression for future reference,
32294 and never update it. For another example, fetching memory is
32295 relatively slow for embedded targets, so a frontend might want
32296 to disable automatic update for the variables that are either not
32297 visible on the screen, or ``closed''. This is possible using so
32298 called ``frozen variable objects''. Such variable objects are never
32299 implicitly updated.
32301 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
32302 fixed variable object, the expression is parsed when the variable
32303 object is created, including associating identifiers to specific
32304 variables. The meaning of expression never changes. For a floating
32305 variable object the values of variables whose names appear in the
32306 expressions are re-evaluated every time in the context of the current
32307 frame. Consider this example:
32312 struct work_state state;
32319 If a fixed variable object for the @code{state} variable is created in
32320 this function, and we enter the recursive call, the variable
32321 object will report the value of @code{state} in the top-level
32322 @code{do_work} invocation. On the other hand, a floating variable
32323 object will report the value of @code{state} in the current frame.
32325 If an expression specified when creating a fixed variable object
32326 refers to a local variable, the variable object becomes bound to the
32327 thread and frame in which the variable object is created. When such
32328 variable object is updated, @value{GDBN} makes sure that the
32329 thread/frame combination the variable object is bound to still exists,
32330 and re-evaluates the variable object in context of that thread/frame.
32332 The following is the complete set of @sc{gdb/mi} operations defined to
32333 access this functionality:
32335 @multitable @columnfractions .4 .6
32336 @item @strong{Operation}
32337 @tab @strong{Description}
32339 @item @code{-enable-pretty-printing}
32340 @tab enable Python-based pretty-printing
32341 @item @code{-var-create}
32342 @tab create a variable object
32343 @item @code{-var-delete}
32344 @tab delete the variable object and/or its children
32345 @item @code{-var-set-format}
32346 @tab set the display format of this variable
32347 @item @code{-var-show-format}
32348 @tab show the display format of this variable
32349 @item @code{-var-info-num-children}
32350 @tab tells how many children this object has
32351 @item @code{-var-list-children}
32352 @tab return a list of the object's children
32353 @item @code{-var-info-type}
32354 @tab show the type of this variable object
32355 @item @code{-var-info-expression}
32356 @tab print parent-relative expression that this variable object represents
32357 @item @code{-var-info-path-expression}
32358 @tab print full expression that this variable object represents
32359 @item @code{-var-show-attributes}
32360 @tab is this variable editable? does it exist here?
32361 @item @code{-var-evaluate-expression}
32362 @tab get the value of this variable
32363 @item @code{-var-assign}
32364 @tab set the value of this variable
32365 @item @code{-var-update}
32366 @tab update the variable and its children
32367 @item @code{-var-set-frozen}
32368 @tab set frozeness attribute
32369 @item @code{-var-set-update-range}
32370 @tab set range of children to display on update
32373 In the next subsection we describe each operation in detail and suggest
32374 how it can be used.
32376 @subheading Description And Use of Operations on Variable Objects
32378 @subheading The @code{-enable-pretty-printing} Command
32379 @findex -enable-pretty-printing
32382 -enable-pretty-printing
32385 @value{GDBN} allows Python-based visualizers to affect the output of the
32386 MI variable object commands. However, because there was no way to
32387 implement this in a fully backward-compatible way, a front end must
32388 request that this functionality be enabled.
32390 Once enabled, this feature cannot be disabled.
32392 Note that if Python support has not been compiled into @value{GDBN},
32393 this command will still succeed (and do nothing).
32395 This feature is currently (as of @value{GDBN} 7.0) experimental, and
32396 may work differently in future versions of @value{GDBN}.
32398 @subheading The @code{-var-create} Command
32399 @findex -var-create
32401 @subsubheading Synopsis
32404 -var-create @{@var{name} | "-"@}
32405 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
32408 This operation creates a variable object, which allows the monitoring of
32409 a variable, the result of an expression, a memory cell or a CPU
32412 The @var{name} parameter is the string by which the object can be
32413 referenced. It must be unique. If @samp{-} is specified, the varobj
32414 system will generate a string ``varNNNNNN'' automatically. It will be
32415 unique provided that one does not specify @var{name} of that format.
32416 The command fails if a duplicate name is found.
32418 The frame under which the expression should be evaluated can be
32419 specified by @var{frame-addr}. A @samp{*} indicates that the current
32420 frame should be used. A @samp{@@} indicates that a floating variable
32421 object must be created.
32423 @var{expression} is any expression valid on the current language set (must not
32424 begin with a @samp{*}), or one of the following:
32428 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
32431 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
32434 @samp{$@var{regname}} --- a CPU register name
32437 @cindex dynamic varobj
32438 A varobj's contents may be provided by a Python-based pretty-printer. In this
32439 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
32440 have slightly different semantics in some cases. If the
32441 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
32442 will never create a dynamic varobj. This ensures backward
32443 compatibility for existing clients.
32445 @subsubheading Result
32447 This operation returns attributes of the newly-created varobj. These
32452 The name of the varobj.
32455 The number of children of the varobj. This number is not necessarily
32456 reliable for a dynamic varobj. Instead, you must examine the
32457 @samp{has_more} attribute.
32460 The varobj's scalar value. For a varobj whose type is some sort of
32461 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
32462 will not be interesting.
32465 The varobj's type. This is a string representation of the type, as
32466 would be printed by the @value{GDBN} CLI. If @samp{print object}
32467 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32468 @emph{actual} (derived) type of the object is shown rather than the
32469 @emph{declared} one.
32472 If a variable object is bound to a specific thread, then this is the
32473 thread's identifier.
32476 For a dynamic varobj, this indicates whether there appear to be any
32477 children available. For a non-dynamic varobj, this will be 0.
32480 This attribute will be present and have the value @samp{1} if the
32481 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32482 then this attribute will not be present.
32485 A dynamic varobj can supply a display hint to the front end. The
32486 value comes directly from the Python pretty-printer object's
32487 @code{display_hint} method. @xref{Pretty Printing API}.
32490 Typical output will look like this:
32493 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
32494 has_more="@var{has_more}"
32498 @subheading The @code{-var-delete} Command
32499 @findex -var-delete
32501 @subsubheading Synopsis
32504 -var-delete [ -c ] @var{name}
32507 Deletes a previously created variable object and all of its children.
32508 With the @samp{-c} option, just deletes the children.
32510 Returns an error if the object @var{name} is not found.
32513 @subheading The @code{-var-set-format} Command
32514 @findex -var-set-format
32516 @subsubheading Synopsis
32519 -var-set-format @var{name} @var{format-spec}
32522 Sets the output format for the value of the object @var{name} to be
32525 @anchor{-var-set-format}
32526 The syntax for the @var{format-spec} is as follows:
32529 @var{format-spec} @expansion{}
32530 @{binary | decimal | hexadecimal | octal | natural@}
32533 The natural format is the default format choosen automatically
32534 based on the variable type (like decimal for an @code{int}, hex
32535 for pointers, etc.).
32537 For a variable with children, the format is set only on the
32538 variable itself, and the children are not affected.
32540 @subheading The @code{-var-show-format} Command
32541 @findex -var-show-format
32543 @subsubheading Synopsis
32546 -var-show-format @var{name}
32549 Returns the format used to display the value of the object @var{name}.
32552 @var{format} @expansion{}
32557 @subheading The @code{-var-info-num-children} Command
32558 @findex -var-info-num-children
32560 @subsubheading Synopsis
32563 -var-info-num-children @var{name}
32566 Returns the number of children of a variable object @var{name}:
32572 Note that this number is not completely reliable for a dynamic varobj.
32573 It will return the current number of children, but more children may
32577 @subheading The @code{-var-list-children} Command
32578 @findex -var-list-children
32580 @subsubheading Synopsis
32583 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32585 @anchor{-var-list-children}
32587 Return a list of the children of the specified variable object and
32588 create variable objects for them, if they do not already exist. With
32589 a single argument or if @var{print-values} has a value of 0 or
32590 @code{--no-values}, print only the names of the variables; if
32591 @var{print-values} is 1 or @code{--all-values}, also print their
32592 values; and if it is 2 or @code{--simple-values} print the name and
32593 value for simple data types and just the name for arrays, structures
32596 @var{from} and @var{to}, if specified, indicate the range of children
32597 to report. If @var{from} or @var{to} is less than zero, the range is
32598 reset and all children will be reported. Otherwise, children starting
32599 at @var{from} (zero-based) and up to and excluding @var{to} will be
32602 If a child range is requested, it will only affect the current call to
32603 @code{-var-list-children}, but not future calls to @code{-var-update}.
32604 For this, you must instead use @code{-var-set-update-range}. The
32605 intent of this approach is to enable a front end to implement any
32606 update approach it likes; for example, scrolling a view may cause the
32607 front end to request more children with @code{-var-list-children}, and
32608 then the front end could call @code{-var-set-update-range} with a
32609 different range to ensure that future updates are restricted to just
32612 For each child the following results are returned:
32617 Name of the variable object created for this child.
32620 The expression to be shown to the user by the front end to designate this child.
32621 For example this may be the name of a structure member.
32623 For a dynamic varobj, this value cannot be used to form an
32624 expression. There is no way to do this at all with a dynamic varobj.
32626 For C/C@t{++} structures there are several pseudo children returned to
32627 designate access qualifiers. For these pseudo children @var{exp} is
32628 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32629 type and value are not present.
32631 A dynamic varobj will not report the access qualifying
32632 pseudo-children, regardless of the language. This information is not
32633 available at all with a dynamic varobj.
32636 Number of children this child has. For a dynamic varobj, this will be
32640 The type of the child. If @samp{print object}
32641 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32642 @emph{actual} (derived) type of the object is shown rather than the
32643 @emph{declared} one.
32646 If values were requested, this is the value.
32649 If this variable object is associated with a thread, this is the thread id.
32650 Otherwise this result is not present.
32653 If the variable object is frozen, this variable will be present with a value of 1.
32656 A dynamic varobj can supply a display hint to the front end. The
32657 value comes directly from the Python pretty-printer object's
32658 @code{display_hint} method. @xref{Pretty Printing API}.
32661 This attribute will be present and have the value @samp{1} if the
32662 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32663 then this attribute will not be present.
32667 The result may have its own attributes:
32671 A dynamic varobj can supply a display hint to the front end. The
32672 value comes directly from the Python pretty-printer object's
32673 @code{display_hint} method. @xref{Pretty Printing API}.
32676 This is an integer attribute which is nonzero if there are children
32677 remaining after the end of the selected range.
32680 @subsubheading Example
32684 -var-list-children n
32685 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32686 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32688 -var-list-children --all-values n
32689 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32690 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32694 @subheading The @code{-var-info-type} Command
32695 @findex -var-info-type
32697 @subsubheading Synopsis
32700 -var-info-type @var{name}
32703 Returns the type of the specified variable @var{name}. The type is
32704 returned as a string in the same format as it is output by the
32708 type=@var{typename}
32712 @subheading The @code{-var-info-expression} Command
32713 @findex -var-info-expression
32715 @subsubheading Synopsis
32718 -var-info-expression @var{name}
32721 Returns a string that is suitable for presenting this
32722 variable object in user interface. The string is generally
32723 not valid expression in the current language, and cannot be evaluated.
32725 For example, if @code{a} is an array, and variable object
32726 @code{A} was created for @code{a}, then we'll get this output:
32729 (gdb) -var-info-expression A.1
32730 ^done,lang="C",exp="1"
32734 Here, the value of @code{lang} is the language name, which can be
32735 found in @ref{Supported Languages}.
32737 Note that the output of the @code{-var-list-children} command also
32738 includes those expressions, so the @code{-var-info-expression} command
32741 @subheading The @code{-var-info-path-expression} Command
32742 @findex -var-info-path-expression
32744 @subsubheading Synopsis
32747 -var-info-path-expression @var{name}
32750 Returns an expression that can be evaluated in the current
32751 context and will yield the same value that a variable object has.
32752 Compare this with the @code{-var-info-expression} command, which
32753 result can be used only for UI presentation. Typical use of
32754 the @code{-var-info-path-expression} command is creating a
32755 watchpoint from a variable object.
32757 This command is currently not valid for children of a dynamic varobj,
32758 and will give an error when invoked on one.
32760 For example, suppose @code{C} is a C@t{++} class, derived from class
32761 @code{Base}, and that the @code{Base} class has a member called
32762 @code{m_size}. Assume a variable @code{c} is has the type of
32763 @code{C} and a variable object @code{C} was created for variable
32764 @code{c}. Then, we'll get this output:
32766 (gdb) -var-info-path-expression C.Base.public.m_size
32767 ^done,path_expr=((Base)c).m_size)
32770 @subheading The @code{-var-show-attributes} Command
32771 @findex -var-show-attributes
32773 @subsubheading Synopsis
32776 -var-show-attributes @var{name}
32779 List attributes of the specified variable object @var{name}:
32782 status=@var{attr} [ ( ,@var{attr} )* ]
32786 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32788 @subheading The @code{-var-evaluate-expression} Command
32789 @findex -var-evaluate-expression
32791 @subsubheading Synopsis
32794 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32797 Evaluates the expression that is represented by the specified variable
32798 object and returns its value as a string. The format of the string
32799 can be specified with the @samp{-f} option. The possible values of
32800 this option are the same as for @code{-var-set-format}
32801 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32802 the current display format will be used. The current display format
32803 can be changed using the @code{-var-set-format} command.
32809 Note that one must invoke @code{-var-list-children} for a variable
32810 before the value of a child variable can be evaluated.
32812 @subheading The @code{-var-assign} Command
32813 @findex -var-assign
32815 @subsubheading Synopsis
32818 -var-assign @var{name} @var{expression}
32821 Assigns the value of @var{expression} to the variable object specified
32822 by @var{name}. The object must be @samp{editable}. If the variable's
32823 value is altered by the assign, the variable will show up in any
32824 subsequent @code{-var-update} list.
32826 @subsubheading Example
32834 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32838 @subheading The @code{-var-update} Command
32839 @findex -var-update
32841 @subsubheading Synopsis
32844 -var-update [@var{print-values}] @{@var{name} | "*"@}
32847 Reevaluate the expressions corresponding to the variable object
32848 @var{name} and all its direct and indirect children, and return the
32849 list of variable objects whose values have changed; @var{name} must
32850 be a root variable object. Here, ``changed'' means that the result of
32851 @code{-var-evaluate-expression} before and after the
32852 @code{-var-update} is different. If @samp{*} is used as the variable
32853 object names, all existing variable objects are updated, except
32854 for frozen ones (@pxref{-var-set-frozen}). The option
32855 @var{print-values} determines whether both names and values, or just
32856 names are printed. The possible values of this option are the same
32857 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32858 recommended to use the @samp{--all-values} option, to reduce the
32859 number of MI commands needed on each program stop.
32861 With the @samp{*} parameter, if a variable object is bound to a
32862 currently running thread, it will not be updated, without any
32865 If @code{-var-set-update-range} was previously used on a varobj, then
32866 only the selected range of children will be reported.
32868 @code{-var-update} reports all the changed varobjs in a tuple named
32871 Each item in the change list is itself a tuple holding:
32875 The name of the varobj.
32878 If values were requested for this update, then this field will be
32879 present and will hold the value of the varobj.
32882 @anchor{-var-update}
32883 This field is a string which may take one of three values:
32887 The variable object's current value is valid.
32890 The variable object does not currently hold a valid value but it may
32891 hold one in the future if its associated expression comes back into
32895 The variable object no longer holds a valid value.
32896 This can occur when the executable file being debugged has changed,
32897 either through recompilation or by using the @value{GDBN} @code{file}
32898 command. The front end should normally choose to delete these variable
32902 In the future new values may be added to this list so the front should
32903 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32906 This is only present if the varobj is still valid. If the type
32907 changed, then this will be the string @samp{true}; otherwise it will
32910 When a varobj's type changes, its children are also likely to have
32911 become incorrect. Therefore, the varobj's children are automatically
32912 deleted when this attribute is @samp{true}. Also, the varobj's update
32913 range, when set using the @code{-var-set-update-range} command, is
32917 If the varobj's type changed, then this field will be present and will
32920 @item new_num_children
32921 For a dynamic varobj, if the number of children changed, or if the
32922 type changed, this will be the new number of children.
32924 The @samp{numchild} field in other varobj responses is generally not
32925 valid for a dynamic varobj -- it will show the number of children that
32926 @value{GDBN} knows about, but because dynamic varobjs lazily
32927 instantiate their children, this will not reflect the number of
32928 children which may be available.
32930 The @samp{new_num_children} attribute only reports changes to the
32931 number of children known by @value{GDBN}. This is the only way to
32932 detect whether an update has removed children (which necessarily can
32933 only happen at the end of the update range).
32936 The display hint, if any.
32939 This is an integer value, which will be 1 if there are more children
32940 available outside the varobj's update range.
32943 This attribute will be present and have the value @samp{1} if the
32944 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32945 then this attribute will not be present.
32948 If new children were added to a dynamic varobj within the selected
32949 update range (as set by @code{-var-set-update-range}), then they will
32950 be listed in this attribute.
32953 @subsubheading Example
32960 -var-update --all-values var1
32961 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32962 type_changed="false"@}]
32966 @subheading The @code{-var-set-frozen} Command
32967 @findex -var-set-frozen
32968 @anchor{-var-set-frozen}
32970 @subsubheading Synopsis
32973 -var-set-frozen @var{name} @var{flag}
32976 Set the frozenness flag on the variable object @var{name}. The
32977 @var{flag} parameter should be either @samp{1} to make the variable
32978 frozen or @samp{0} to make it unfrozen. If a variable object is
32979 frozen, then neither itself, nor any of its children, are
32980 implicitly updated by @code{-var-update} of
32981 a parent variable or by @code{-var-update *}. Only
32982 @code{-var-update} of the variable itself will update its value and
32983 values of its children. After a variable object is unfrozen, it is
32984 implicitly updated by all subsequent @code{-var-update} operations.
32985 Unfreezing a variable does not update it, only subsequent
32986 @code{-var-update} does.
32988 @subsubheading Example
32992 -var-set-frozen V 1
32997 @subheading The @code{-var-set-update-range} command
32998 @findex -var-set-update-range
32999 @anchor{-var-set-update-range}
33001 @subsubheading Synopsis
33004 -var-set-update-range @var{name} @var{from} @var{to}
33007 Set the range of children to be returned by future invocations of
33008 @code{-var-update}.
33010 @var{from} and @var{to} indicate the range of children to report. If
33011 @var{from} or @var{to} is less than zero, the range is reset and all
33012 children will be reported. Otherwise, children starting at @var{from}
33013 (zero-based) and up to and excluding @var{to} will be reported.
33015 @subsubheading Example
33019 -var-set-update-range V 1 2
33023 @subheading The @code{-var-set-visualizer} command
33024 @findex -var-set-visualizer
33025 @anchor{-var-set-visualizer}
33027 @subsubheading Synopsis
33030 -var-set-visualizer @var{name} @var{visualizer}
33033 Set a visualizer for the variable object @var{name}.
33035 @var{visualizer} is the visualizer to use. The special value
33036 @samp{None} means to disable any visualizer in use.
33038 If not @samp{None}, @var{visualizer} must be a Python expression.
33039 This expression must evaluate to a callable object which accepts a
33040 single argument. @value{GDBN} will call this object with the value of
33041 the varobj @var{name} as an argument (this is done so that the same
33042 Python pretty-printing code can be used for both the CLI and MI).
33043 When called, this object must return an object which conforms to the
33044 pretty-printing interface (@pxref{Pretty Printing API}).
33046 The pre-defined function @code{gdb.default_visualizer} may be used to
33047 select a visualizer by following the built-in process
33048 (@pxref{Selecting Pretty-Printers}). This is done automatically when
33049 a varobj is created, and so ordinarily is not needed.
33051 This feature is only available if Python support is enabled. The MI
33052 command @code{-list-features} (@pxref{GDB/MI Support Commands})
33053 can be used to check this.
33055 @subsubheading Example
33057 Resetting the visualizer:
33061 -var-set-visualizer V None
33065 Reselecting the default (type-based) visualizer:
33069 -var-set-visualizer V gdb.default_visualizer
33073 Suppose @code{SomeClass} is a visualizer class. A lambda expression
33074 can be used to instantiate this class for a varobj:
33078 -var-set-visualizer V "lambda val: SomeClass()"
33082 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33083 @node GDB/MI Data Manipulation
33084 @section @sc{gdb/mi} Data Manipulation
33086 @cindex data manipulation, in @sc{gdb/mi}
33087 @cindex @sc{gdb/mi}, data manipulation
33088 This section describes the @sc{gdb/mi} commands that manipulate data:
33089 examine memory and registers, evaluate expressions, etc.
33091 @c REMOVED FROM THE INTERFACE.
33092 @c @subheading -data-assign
33093 @c Change the value of a program variable. Plenty of side effects.
33094 @c @subsubheading GDB Command
33096 @c @subsubheading Example
33099 @subheading The @code{-data-disassemble} Command
33100 @findex -data-disassemble
33102 @subsubheading Synopsis
33106 [ -s @var{start-addr} -e @var{end-addr} ]
33107 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
33115 @item @var{start-addr}
33116 is the beginning address (or @code{$pc})
33117 @item @var{end-addr}
33119 @item @var{filename}
33120 is the name of the file to disassemble
33121 @item @var{linenum}
33122 is the line number to disassemble around
33124 is the number of disassembly lines to be produced. If it is -1,
33125 the whole function will be disassembled, in case no @var{end-addr} is
33126 specified. If @var{end-addr} is specified as a non-zero value, and
33127 @var{lines} is lower than the number of disassembly lines between
33128 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
33129 displayed; if @var{lines} is higher than the number of lines between
33130 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
33133 is either 0 (meaning only disassembly), 1 (meaning mixed source and
33134 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
33135 mixed source and disassembly with raw opcodes).
33138 @subsubheading Result
33140 The result of the @code{-data-disassemble} command will be a list named
33141 @samp{asm_insns}, the contents of this list depend on the @var{mode}
33142 used with the @code{-data-disassemble} command.
33144 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
33149 The address at which this instruction was disassembled.
33152 The name of the function this instruction is within.
33155 The decimal offset in bytes from the start of @samp{func-name}.
33158 The text disassembly for this @samp{address}.
33161 This field is only present for mode 2. This contains the raw opcode
33162 bytes for the @samp{inst} field.
33166 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
33167 @samp{src_and_asm_line}, each of which has the following fields:
33171 The line number within @samp{file}.
33174 The file name from the compilation unit. This might be an absolute
33175 file name or a relative file name depending on the compile command
33179 Absolute file name of @samp{file}. It is converted to a canonical form
33180 using the source file search path
33181 (@pxref{Source Path, ,Specifying Source Directories})
33182 and after resolving all the symbolic links.
33184 If the source file is not found this field will contain the path as
33185 present in the debug information.
33187 @item line_asm_insn
33188 This is a list of tuples containing the disassembly for @samp{line} in
33189 @samp{file}. The fields of each tuple are the same as for
33190 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
33191 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
33196 Note that whatever included in the @samp{inst} field, is not
33197 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
33200 @subsubheading @value{GDBN} Command
33202 The corresponding @value{GDBN} command is @samp{disassemble}.
33204 @subsubheading Example
33206 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
33210 -data-disassemble -s $pc -e "$pc + 20" -- 0
33213 @{address="0x000107c0",func-name="main",offset="4",
33214 inst="mov 2, %o0"@},
33215 @{address="0x000107c4",func-name="main",offset="8",
33216 inst="sethi %hi(0x11800), %o2"@},
33217 @{address="0x000107c8",func-name="main",offset="12",
33218 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
33219 @{address="0x000107cc",func-name="main",offset="16",
33220 inst="sethi %hi(0x11800), %o2"@},
33221 @{address="0x000107d0",func-name="main",offset="20",
33222 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
33226 Disassemble the whole @code{main} function. Line 32 is part of
33230 -data-disassemble -f basics.c -l 32 -- 0
33232 @{address="0x000107bc",func-name="main",offset="0",
33233 inst="save %sp, -112, %sp"@},
33234 @{address="0x000107c0",func-name="main",offset="4",
33235 inst="mov 2, %o0"@},
33236 @{address="0x000107c4",func-name="main",offset="8",
33237 inst="sethi %hi(0x11800), %o2"@},
33239 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
33240 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
33244 Disassemble 3 instructions from the start of @code{main}:
33248 -data-disassemble -f basics.c -l 32 -n 3 -- 0
33250 @{address="0x000107bc",func-name="main",offset="0",
33251 inst="save %sp, -112, %sp"@},
33252 @{address="0x000107c0",func-name="main",offset="4",
33253 inst="mov 2, %o0"@},
33254 @{address="0x000107c4",func-name="main",offset="8",
33255 inst="sethi %hi(0x11800), %o2"@}]
33259 Disassemble 3 instructions from the start of @code{main} in mixed mode:
33263 -data-disassemble -f basics.c -l 32 -n 3 -- 1
33265 src_and_asm_line=@{line="31",
33266 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33267 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33268 line_asm_insn=[@{address="0x000107bc",
33269 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
33270 src_and_asm_line=@{line="32",
33271 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
33272 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
33273 line_asm_insn=[@{address="0x000107c0",
33274 func-name="main",offset="4",inst="mov 2, %o0"@},
33275 @{address="0x000107c4",func-name="main",offset="8",
33276 inst="sethi %hi(0x11800), %o2"@}]@}]
33281 @subheading The @code{-data-evaluate-expression} Command
33282 @findex -data-evaluate-expression
33284 @subsubheading Synopsis
33287 -data-evaluate-expression @var{expr}
33290 Evaluate @var{expr} as an expression. The expression could contain an
33291 inferior function call. The function call will execute synchronously.
33292 If the expression contains spaces, it must be enclosed in double quotes.
33294 @subsubheading @value{GDBN} Command
33296 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
33297 @samp{call}. In @code{gdbtk} only, there's a corresponding
33298 @samp{gdb_eval} command.
33300 @subsubheading Example
33302 In the following example, the numbers that precede the commands are the
33303 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
33304 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
33308 211-data-evaluate-expression A
33311 311-data-evaluate-expression &A
33312 311^done,value="0xefffeb7c"
33314 411-data-evaluate-expression A+3
33317 511-data-evaluate-expression "A + 3"
33323 @subheading The @code{-data-list-changed-registers} Command
33324 @findex -data-list-changed-registers
33326 @subsubheading Synopsis
33329 -data-list-changed-registers
33332 Display a list of the registers that have changed.
33334 @subsubheading @value{GDBN} Command
33336 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
33337 has the corresponding command @samp{gdb_changed_register_list}.
33339 @subsubheading Example
33341 On a PPC MBX board:
33349 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
33350 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
33353 -data-list-changed-registers
33354 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
33355 "10","11","13","14","15","16","17","18","19","20","21","22","23",
33356 "24","25","26","27","28","30","31","64","65","66","67","69"]
33361 @subheading The @code{-data-list-register-names} Command
33362 @findex -data-list-register-names
33364 @subsubheading Synopsis
33367 -data-list-register-names [ ( @var{regno} )+ ]
33370 Show a list of register names for the current target. If no arguments
33371 are given, it shows a list of the names of all the registers. If
33372 integer numbers are given as arguments, it will print a list of the
33373 names of the registers corresponding to the arguments. To ensure
33374 consistency between a register name and its number, the output list may
33375 include empty register names.
33377 @subsubheading @value{GDBN} Command
33379 @value{GDBN} does not have a command which corresponds to
33380 @samp{-data-list-register-names}. In @code{gdbtk} there is a
33381 corresponding command @samp{gdb_regnames}.
33383 @subsubheading Example
33385 For the PPC MBX board:
33388 -data-list-register-names
33389 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
33390 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
33391 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
33392 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
33393 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
33394 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
33395 "", "pc","ps","cr","lr","ctr","xer"]
33397 -data-list-register-names 1 2 3
33398 ^done,register-names=["r1","r2","r3"]
33402 @subheading The @code{-data-list-register-values} Command
33403 @findex -data-list-register-values
33405 @subsubheading Synopsis
33408 -data-list-register-values
33409 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
33412 Display the registers' contents. @var{fmt} is the format according to
33413 which the registers' contents are to be returned, followed by an optional
33414 list of numbers specifying the registers to display. A missing list of
33415 numbers indicates that the contents of all the registers must be
33416 returned. The @code{--skip-unavailable} option indicates that only
33417 the available registers are to be returned.
33419 Allowed formats for @var{fmt} are:
33436 @subsubheading @value{GDBN} Command
33438 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
33439 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
33441 @subsubheading Example
33443 For a PPC MBX board (note: line breaks are for readability only, they
33444 don't appear in the actual output):
33448 -data-list-register-values r 64 65
33449 ^done,register-values=[@{number="64",value="0xfe00a300"@},
33450 @{number="65",value="0x00029002"@}]
33452 -data-list-register-values x
33453 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
33454 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
33455 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
33456 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
33457 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
33458 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
33459 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
33460 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
33461 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
33462 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
33463 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
33464 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
33465 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
33466 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
33467 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
33468 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
33469 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
33470 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
33471 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
33472 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
33473 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
33474 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
33475 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
33476 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
33477 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
33478 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
33479 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
33480 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
33481 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
33482 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
33483 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
33484 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
33485 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
33486 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
33487 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
33488 @{number="69",value="0x20002b03"@}]
33493 @subheading The @code{-data-read-memory} Command
33494 @findex -data-read-memory
33496 This command is deprecated, use @code{-data-read-memory-bytes} instead.
33498 @subsubheading Synopsis
33501 -data-read-memory [ -o @var{byte-offset} ]
33502 @var{address} @var{word-format} @var{word-size}
33503 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
33510 @item @var{address}
33511 An expression specifying the address of the first memory word to be
33512 read. Complex expressions containing embedded white space should be
33513 quoted using the C convention.
33515 @item @var{word-format}
33516 The format to be used to print the memory words. The notation is the
33517 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
33520 @item @var{word-size}
33521 The size of each memory word in bytes.
33523 @item @var{nr-rows}
33524 The number of rows in the output table.
33526 @item @var{nr-cols}
33527 The number of columns in the output table.
33530 If present, indicates that each row should include an @sc{ascii} dump. The
33531 value of @var{aschar} is used as a padding character when a byte is not a
33532 member of the printable @sc{ascii} character set (printable @sc{ascii}
33533 characters are those whose code is between 32 and 126, inclusively).
33535 @item @var{byte-offset}
33536 An offset to add to the @var{address} before fetching memory.
33539 This command displays memory contents as a table of @var{nr-rows} by
33540 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
33541 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
33542 (returned as @samp{total-bytes}). Should less than the requested number
33543 of bytes be returned by the target, the missing words are identified
33544 using @samp{N/A}. The number of bytes read from the target is returned
33545 in @samp{nr-bytes} and the starting address used to read memory in
33548 The address of the next/previous row or page is available in
33549 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
33552 @subsubheading @value{GDBN} Command
33554 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
33555 @samp{gdb_get_mem} memory read command.
33557 @subsubheading Example
33559 Read six bytes of memory starting at @code{bytes+6} but then offset by
33560 @code{-6} bytes. Format as three rows of two columns. One byte per
33561 word. Display each word in hex.
33565 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
33566 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
33567 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
33568 prev-page="0x0000138a",memory=[
33569 @{addr="0x00001390",data=["0x00","0x01"]@},
33570 @{addr="0x00001392",data=["0x02","0x03"]@},
33571 @{addr="0x00001394",data=["0x04","0x05"]@}]
33575 Read two bytes of memory starting at address @code{shorts + 64} and
33576 display as a single word formatted in decimal.
33580 5-data-read-memory shorts+64 d 2 1 1
33581 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
33582 next-row="0x00001512",prev-row="0x0000150e",
33583 next-page="0x00001512",prev-page="0x0000150e",memory=[
33584 @{addr="0x00001510",data=["128"]@}]
33588 Read thirty two bytes of memory starting at @code{bytes+16} and format
33589 as eight rows of four columns. Include a string encoding with @samp{x}
33590 used as the non-printable character.
33594 4-data-read-memory bytes+16 x 1 8 4 x
33595 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33596 next-row="0x000013c0",prev-row="0x0000139c",
33597 next-page="0x000013c0",prev-page="0x00001380",memory=[
33598 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33599 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33600 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33601 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33602 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33603 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33604 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33605 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33609 @subheading The @code{-data-read-memory-bytes} Command
33610 @findex -data-read-memory-bytes
33612 @subsubheading Synopsis
33615 -data-read-memory-bytes [ -o @var{byte-offset} ]
33616 @var{address} @var{count}
33623 @item @var{address}
33624 An expression specifying the address of the first memory word to be
33625 read. Complex expressions containing embedded white space should be
33626 quoted using the C convention.
33629 The number of bytes to read. This should be an integer literal.
33631 @item @var{byte-offset}
33632 The offsets in bytes relative to @var{address} at which to start
33633 reading. This should be an integer literal. This option is provided
33634 so that a frontend is not required to first evaluate address and then
33635 perform address arithmetics itself.
33639 This command attempts to read all accessible memory regions in the
33640 specified range. First, all regions marked as unreadable in the memory
33641 map (if one is defined) will be skipped. @xref{Memory Region
33642 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33643 regions. For each one, if reading full region results in an errors,
33644 @value{GDBN} will try to read a subset of the region.
33646 In general, every single byte in the region may be readable or not,
33647 and the only way to read every readable byte is to try a read at
33648 every address, which is not practical. Therefore, @value{GDBN} will
33649 attempt to read all accessible bytes at either beginning or the end
33650 of the region, using a binary division scheme. This heuristic works
33651 well for reading accross a memory map boundary. Note that if a region
33652 has a readable range that is neither at the beginning or the end,
33653 @value{GDBN} will not read it.
33655 The result record (@pxref{GDB/MI Result Records}) that is output of
33656 the command includes a field named @samp{memory} whose content is a
33657 list of tuples. Each tuple represent a successfully read memory block
33658 and has the following fields:
33662 The start address of the memory block, as hexadecimal literal.
33665 The end address of the memory block, as hexadecimal literal.
33668 The offset of the memory block, as hexadecimal literal, relative to
33669 the start address passed to @code{-data-read-memory-bytes}.
33672 The contents of the memory block, in hex.
33678 @subsubheading @value{GDBN} Command
33680 The corresponding @value{GDBN} command is @samp{x}.
33682 @subsubheading Example
33686 -data-read-memory-bytes &a 10
33687 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33689 contents="01000000020000000300"@}]
33694 @subheading The @code{-data-write-memory-bytes} Command
33695 @findex -data-write-memory-bytes
33697 @subsubheading Synopsis
33700 -data-write-memory-bytes @var{address} @var{contents}
33701 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33708 @item @var{address}
33709 An expression specifying the address of the first memory word to be
33710 read. Complex expressions containing embedded white space should be
33711 quoted using the C convention.
33713 @item @var{contents}
33714 The hex-encoded bytes to write.
33717 Optional argument indicating the number of bytes to be written. If @var{count}
33718 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33719 write @var{contents} until it fills @var{count} bytes.
33723 @subsubheading @value{GDBN} Command
33725 There's no corresponding @value{GDBN} command.
33727 @subsubheading Example
33731 -data-write-memory-bytes &a "aabbccdd"
33738 -data-write-memory-bytes &a "aabbccdd" 16e
33743 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33744 @node GDB/MI Tracepoint Commands
33745 @section @sc{gdb/mi} Tracepoint Commands
33747 The commands defined in this section implement MI support for
33748 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33750 @subheading The @code{-trace-find} Command
33751 @findex -trace-find
33753 @subsubheading Synopsis
33756 -trace-find @var{mode} [@var{parameters}@dots{}]
33759 Find a trace frame using criteria defined by @var{mode} and
33760 @var{parameters}. The following table lists permissible
33761 modes and their parameters. For details of operation, see @ref{tfind}.
33766 No parameters are required. Stops examining trace frames.
33769 An integer is required as parameter. Selects tracepoint frame with
33772 @item tracepoint-number
33773 An integer is required as parameter. Finds next
33774 trace frame that corresponds to tracepoint with the specified number.
33777 An address is required as parameter. Finds
33778 next trace frame that corresponds to any tracepoint at the specified
33781 @item pc-inside-range
33782 Two addresses are required as parameters. Finds next trace
33783 frame that corresponds to a tracepoint at an address inside the
33784 specified range. Both bounds are considered to be inside the range.
33786 @item pc-outside-range
33787 Two addresses are required as parameters. Finds
33788 next trace frame that corresponds to a tracepoint at an address outside
33789 the specified range. Both bounds are considered to be inside the range.
33792 Line specification is required as parameter. @xref{Specify Location}.
33793 Finds next trace frame that corresponds to a tracepoint at
33794 the specified location.
33798 If @samp{none} was passed as @var{mode}, the response does not
33799 have fields. Otherwise, the response may have the following fields:
33803 This field has either @samp{0} or @samp{1} as the value, depending
33804 on whether a matching tracepoint was found.
33807 The index of the found traceframe. This field is present iff
33808 the @samp{found} field has value of @samp{1}.
33811 The index of the found tracepoint. This field is present iff
33812 the @samp{found} field has value of @samp{1}.
33815 The information about the frame corresponding to the found trace
33816 frame. This field is present only if a trace frame was found.
33817 @xref{GDB/MI Frame Information}, for description of this field.
33821 @subsubheading @value{GDBN} Command
33823 The corresponding @value{GDBN} command is @samp{tfind}.
33825 @subheading -trace-define-variable
33826 @findex -trace-define-variable
33828 @subsubheading Synopsis
33831 -trace-define-variable @var{name} [ @var{value} ]
33834 Create trace variable @var{name} if it does not exist. If
33835 @var{value} is specified, sets the initial value of the specified
33836 trace variable to that value. Note that the @var{name} should start
33837 with the @samp{$} character.
33839 @subsubheading @value{GDBN} Command
33841 The corresponding @value{GDBN} command is @samp{tvariable}.
33843 @subheading The @code{-trace-frame-collected} Command
33844 @findex -trace-frame-collected
33846 @subsubheading Synopsis
33849 -trace-frame-collected
33850 [--var-print-values @var{var_pval}]
33851 [--comp-print-values @var{comp_pval}]
33852 [--registers-format @var{regformat}]
33853 [--memory-contents]
33856 This command returns the set of collected objects, register names,
33857 trace state variable names, memory ranges and computed expressions
33858 that have been collected at a particular trace frame. The optional
33859 parameters to the command affect the output format in different ways.
33860 See the output description table below for more details.
33862 The reported names can be used in the normal manner to create
33863 varobjs and inspect the objects themselves. The items returned by
33864 this command are categorized so that it is clear which is a variable,
33865 which is a register, which is a trace state variable, which is a
33866 memory range and which is a computed expression.
33868 For instance, if the actions were
33870 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33871 collect *(int*)0xaf02bef0@@40
33875 the object collected in its entirety would be @code{myVar}. The
33876 object @code{myArray} would be partially collected, because only the
33877 element at index @code{myIndex} would be collected. The remaining
33878 objects would be computed expressions.
33880 An example output would be:
33884 -trace-frame-collected
33886 explicit-variables=[@{name="myVar",value="1"@}],
33887 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33888 @{name="myObj.field",value="0"@},
33889 @{name="myPtr->field",value="1"@},
33890 @{name="myCount + 2",value="3"@},
33891 @{name="$tvar1 + 1",value="43970027"@}],
33892 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33893 @{number="1",value="0x0"@},
33894 @{number="2",value="0x4"@},
33896 @{number="125",value="0x0"@}],
33897 tvars=[@{name="$tvar1",current="43970026"@}],
33898 memory=[@{address="0x0000000000602264",length="4"@},
33899 @{address="0x0000000000615bc0",length="4"@}]
33906 @item explicit-variables
33907 The set of objects that have been collected in their entirety (as
33908 opposed to collecting just a few elements of an array or a few struct
33909 members). For each object, its name and value are printed.
33910 The @code{--var-print-values} option affects how or whether the value
33911 field is output. If @var{var_pval} is 0, then print only the names;
33912 if it is 1, print also their values; and if it is 2, print the name,
33913 type and value for simple data types, and the name and type for
33914 arrays, structures and unions.
33916 @item computed-expressions
33917 The set of computed expressions that have been collected at the
33918 current trace frame. The @code{--comp-print-values} option affects
33919 this set like the @code{--var-print-values} option affects the
33920 @code{explicit-variables} set. See above.
33923 The registers that have been collected at the current trace frame.
33924 For each register collected, the name and current value are returned.
33925 The value is formatted according to the @code{--registers-format}
33926 option. See the @command{-data-list-register-values} command for a
33927 list of the allowed formats. The default is @samp{x}.
33930 The trace state variables that have been collected at the current
33931 trace frame. For each trace state variable collected, the name and
33932 current value are returned.
33935 The set of memory ranges that have been collected at the current trace
33936 frame. Its content is a list of tuples. Each tuple represents a
33937 collected memory range and has the following fields:
33941 The start address of the memory range, as hexadecimal literal.
33944 The length of the memory range, as decimal literal.
33947 The contents of the memory block, in hex. This field is only present
33948 if the @code{--memory-contents} option is specified.
33954 @subsubheading @value{GDBN} Command
33956 There is no corresponding @value{GDBN} command.
33958 @subsubheading Example
33960 @subheading -trace-list-variables
33961 @findex -trace-list-variables
33963 @subsubheading Synopsis
33966 -trace-list-variables
33969 Return a table of all defined trace variables. Each element of the
33970 table has the following fields:
33974 The name of the trace variable. This field is always present.
33977 The initial value. This is a 64-bit signed integer. This
33978 field is always present.
33981 The value the trace variable has at the moment. This is a 64-bit
33982 signed integer. This field is absent iff current value is
33983 not defined, for example if the trace was never run, or is
33988 @subsubheading @value{GDBN} Command
33990 The corresponding @value{GDBN} command is @samp{tvariables}.
33992 @subsubheading Example
33996 -trace-list-variables
33997 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33998 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33999 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
34000 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
34001 body=[variable=@{name="$trace_timestamp",initial="0"@}
34002 variable=@{name="$foo",initial="10",current="15"@}]@}
34006 @subheading -trace-save
34007 @findex -trace-save
34009 @subsubheading Synopsis
34012 -trace-save [-r ] @var{filename}
34015 Saves the collected trace data to @var{filename}. Without the
34016 @samp{-r} option, the data is downloaded from the target and saved
34017 in a local file. With the @samp{-r} option the target is asked
34018 to perform the save.
34020 @subsubheading @value{GDBN} Command
34022 The corresponding @value{GDBN} command is @samp{tsave}.
34025 @subheading -trace-start
34026 @findex -trace-start
34028 @subsubheading Synopsis
34034 Starts a tracing experiments. The result of this command does not
34037 @subsubheading @value{GDBN} Command
34039 The corresponding @value{GDBN} command is @samp{tstart}.
34041 @subheading -trace-status
34042 @findex -trace-status
34044 @subsubheading Synopsis
34050 Obtains the status of a tracing experiment. The result may include
34051 the following fields:
34056 May have a value of either @samp{0}, when no tracing operations are
34057 supported, @samp{1}, when all tracing operations are supported, or
34058 @samp{file} when examining trace file. In the latter case, examining
34059 of trace frame is possible but new tracing experiement cannot be
34060 started. This field is always present.
34063 May have a value of either @samp{0} or @samp{1} depending on whether
34064 tracing experiement is in progress on target. This field is present
34065 if @samp{supported} field is not @samp{0}.
34068 Report the reason why the tracing was stopped last time. This field
34069 may be absent iff tracing was never stopped on target yet. The
34070 value of @samp{request} means the tracing was stopped as result of
34071 the @code{-trace-stop} command. The value of @samp{overflow} means
34072 the tracing buffer is full. The value of @samp{disconnection} means
34073 tracing was automatically stopped when @value{GDBN} has disconnected.
34074 The value of @samp{passcount} means tracing was stopped when a
34075 tracepoint was passed a maximal number of times for that tracepoint.
34076 This field is present if @samp{supported} field is not @samp{0}.
34078 @item stopping-tracepoint
34079 The number of tracepoint whose passcount as exceeded. This field is
34080 present iff the @samp{stop-reason} field has the value of
34084 @itemx frames-created
34085 The @samp{frames} field is a count of the total number of trace frames
34086 in the trace buffer, while @samp{frames-created} is the total created
34087 during the run, including ones that were discarded, such as when a
34088 circular trace buffer filled up. Both fields are optional.
34092 These fields tell the current size of the tracing buffer and the
34093 remaining space. These fields are optional.
34096 The value of the circular trace buffer flag. @code{1} means that the
34097 trace buffer is circular and old trace frames will be discarded if
34098 necessary to make room, @code{0} means that the trace buffer is linear
34102 The value of the disconnected tracing flag. @code{1} means that
34103 tracing will continue after @value{GDBN} disconnects, @code{0} means
34104 that the trace run will stop.
34107 The filename of the trace file being examined. This field is
34108 optional, and only present when examining a trace file.
34112 @subsubheading @value{GDBN} Command
34114 The corresponding @value{GDBN} command is @samp{tstatus}.
34116 @subheading -trace-stop
34117 @findex -trace-stop
34119 @subsubheading Synopsis
34125 Stops a tracing experiment. The result of this command has the same
34126 fields as @code{-trace-status}, except that the @samp{supported} and
34127 @samp{running} fields are not output.
34129 @subsubheading @value{GDBN} Command
34131 The corresponding @value{GDBN} command is @samp{tstop}.
34134 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34135 @node GDB/MI Symbol Query
34136 @section @sc{gdb/mi} Symbol Query Commands
34140 @subheading The @code{-symbol-info-address} Command
34141 @findex -symbol-info-address
34143 @subsubheading Synopsis
34146 -symbol-info-address @var{symbol}
34149 Describe where @var{symbol} is stored.
34151 @subsubheading @value{GDBN} Command
34153 The corresponding @value{GDBN} command is @samp{info address}.
34155 @subsubheading Example
34159 @subheading The @code{-symbol-info-file} Command
34160 @findex -symbol-info-file
34162 @subsubheading Synopsis
34168 Show the file for the symbol.
34170 @subsubheading @value{GDBN} Command
34172 There's no equivalent @value{GDBN} command. @code{gdbtk} has
34173 @samp{gdb_find_file}.
34175 @subsubheading Example
34179 @subheading The @code{-symbol-info-function} Command
34180 @findex -symbol-info-function
34182 @subsubheading Synopsis
34185 -symbol-info-function
34188 Show which function the symbol lives in.
34190 @subsubheading @value{GDBN} Command
34192 @samp{gdb_get_function} in @code{gdbtk}.
34194 @subsubheading Example
34198 @subheading The @code{-symbol-info-line} Command
34199 @findex -symbol-info-line
34201 @subsubheading Synopsis
34207 Show the core addresses of the code for a source line.
34209 @subsubheading @value{GDBN} Command
34211 The corresponding @value{GDBN} command is @samp{info line}.
34212 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
34214 @subsubheading Example
34218 @subheading The @code{-symbol-info-symbol} Command
34219 @findex -symbol-info-symbol
34221 @subsubheading Synopsis
34224 -symbol-info-symbol @var{addr}
34227 Describe what symbol is at location @var{addr}.
34229 @subsubheading @value{GDBN} Command
34231 The corresponding @value{GDBN} command is @samp{info symbol}.
34233 @subsubheading Example
34237 @subheading The @code{-symbol-list-functions} Command
34238 @findex -symbol-list-functions
34240 @subsubheading Synopsis
34243 -symbol-list-functions
34246 List the functions in the executable.
34248 @subsubheading @value{GDBN} Command
34250 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
34251 @samp{gdb_search} in @code{gdbtk}.
34253 @subsubheading Example
34258 @subheading The @code{-symbol-list-lines} Command
34259 @findex -symbol-list-lines
34261 @subsubheading Synopsis
34264 -symbol-list-lines @var{filename}
34267 Print the list of lines that contain code and their associated program
34268 addresses for the given source filename. The entries are sorted in
34269 ascending PC order.
34271 @subsubheading @value{GDBN} Command
34273 There is no corresponding @value{GDBN} command.
34275 @subsubheading Example
34278 -symbol-list-lines basics.c
34279 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
34285 @subheading The @code{-symbol-list-types} Command
34286 @findex -symbol-list-types
34288 @subsubheading Synopsis
34294 List all the type names.
34296 @subsubheading @value{GDBN} Command
34298 The corresponding commands are @samp{info types} in @value{GDBN},
34299 @samp{gdb_search} in @code{gdbtk}.
34301 @subsubheading Example
34305 @subheading The @code{-symbol-list-variables} Command
34306 @findex -symbol-list-variables
34308 @subsubheading Synopsis
34311 -symbol-list-variables
34314 List all the global and static variable names.
34316 @subsubheading @value{GDBN} Command
34318 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
34320 @subsubheading Example
34324 @subheading The @code{-symbol-locate} Command
34325 @findex -symbol-locate
34327 @subsubheading Synopsis
34333 @subsubheading @value{GDBN} Command
34335 @samp{gdb_loc} in @code{gdbtk}.
34337 @subsubheading Example
34341 @subheading The @code{-symbol-type} Command
34342 @findex -symbol-type
34344 @subsubheading Synopsis
34347 -symbol-type @var{variable}
34350 Show type of @var{variable}.
34352 @subsubheading @value{GDBN} Command
34354 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
34355 @samp{gdb_obj_variable}.
34357 @subsubheading Example
34362 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34363 @node GDB/MI File Commands
34364 @section @sc{gdb/mi} File Commands
34366 This section describes the GDB/MI commands to specify executable file names
34367 and to read in and obtain symbol table information.
34369 @subheading The @code{-file-exec-and-symbols} Command
34370 @findex -file-exec-and-symbols
34372 @subsubheading Synopsis
34375 -file-exec-and-symbols @var{file}
34378 Specify the executable file to be debugged. This file is the one from
34379 which the symbol table is also read. If no file is specified, the
34380 command clears the executable and symbol information. If breakpoints
34381 are set when using this command with no arguments, @value{GDBN} will produce
34382 error messages. Otherwise, no output is produced, except a completion
34385 @subsubheading @value{GDBN} Command
34387 The corresponding @value{GDBN} command is @samp{file}.
34389 @subsubheading Example
34393 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34399 @subheading The @code{-file-exec-file} Command
34400 @findex -file-exec-file
34402 @subsubheading Synopsis
34405 -file-exec-file @var{file}
34408 Specify the executable file to be debugged. Unlike
34409 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
34410 from this file. If used without argument, @value{GDBN} clears the information
34411 about the executable file. No output is produced, except a completion
34414 @subsubheading @value{GDBN} Command
34416 The corresponding @value{GDBN} command is @samp{exec-file}.
34418 @subsubheading Example
34422 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34429 @subheading The @code{-file-list-exec-sections} Command
34430 @findex -file-list-exec-sections
34432 @subsubheading Synopsis
34435 -file-list-exec-sections
34438 List the sections of the current executable file.
34440 @subsubheading @value{GDBN} Command
34442 The @value{GDBN} command @samp{info file} shows, among the rest, the same
34443 information as this command. @code{gdbtk} has a corresponding command
34444 @samp{gdb_load_info}.
34446 @subsubheading Example
34451 @subheading The @code{-file-list-exec-source-file} Command
34452 @findex -file-list-exec-source-file
34454 @subsubheading Synopsis
34457 -file-list-exec-source-file
34460 List the line number, the current source file, and the absolute path
34461 to the current source file for the current executable. The macro
34462 information field has a value of @samp{1} or @samp{0} depending on
34463 whether or not the file includes preprocessor macro information.
34465 @subsubheading @value{GDBN} Command
34467 The @value{GDBN} equivalent is @samp{info source}
34469 @subsubheading Example
34473 123-file-list-exec-source-file
34474 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
34479 @subheading The @code{-file-list-exec-source-files} Command
34480 @findex -file-list-exec-source-files
34482 @subsubheading Synopsis
34485 -file-list-exec-source-files
34488 List the source files for the current executable.
34490 It will always output both the filename and fullname (absolute file
34491 name) of a source file.
34493 @subsubheading @value{GDBN} Command
34495 The @value{GDBN} equivalent is @samp{info sources}.
34496 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
34498 @subsubheading Example
34501 -file-list-exec-source-files
34503 @{file=foo.c,fullname=/home/foo.c@},
34504 @{file=/home/bar.c,fullname=/home/bar.c@},
34505 @{file=gdb_could_not_find_fullpath.c@}]
34510 @subheading The @code{-file-list-shared-libraries} Command
34511 @findex -file-list-shared-libraries
34513 @subsubheading Synopsis
34516 -file-list-shared-libraries
34519 List the shared libraries in the program.
34521 @subsubheading @value{GDBN} Command
34523 The corresponding @value{GDBN} command is @samp{info shared}.
34525 @subsubheading Example
34529 @subheading The @code{-file-list-symbol-files} Command
34530 @findex -file-list-symbol-files
34532 @subsubheading Synopsis
34535 -file-list-symbol-files
34540 @subsubheading @value{GDBN} Command
34542 The corresponding @value{GDBN} command is @samp{info file} (part of it).
34544 @subsubheading Example
34549 @subheading The @code{-file-symbol-file} Command
34550 @findex -file-symbol-file
34552 @subsubheading Synopsis
34555 -file-symbol-file @var{file}
34558 Read symbol table info from the specified @var{file} argument. When
34559 used without arguments, clears @value{GDBN}'s symbol table info. No output is
34560 produced, except for a completion notification.
34562 @subsubheading @value{GDBN} Command
34564 The corresponding @value{GDBN} command is @samp{symbol-file}.
34566 @subsubheading Example
34570 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
34576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34577 @node GDB/MI Memory Overlay Commands
34578 @section @sc{gdb/mi} Memory Overlay Commands
34580 The memory overlay commands are not implemented.
34582 @c @subheading -overlay-auto
34584 @c @subheading -overlay-list-mapping-state
34586 @c @subheading -overlay-list-overlays
34588 @c @subheading -overlay-map
34590 @c @subheading -overlay-off
34592 @c @subheading -overlay-on
34594 @c @subheading -overlay-unmap
34596 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34597 @node GDB/MI Signal Handling Commands
34598 @section @sc{gdb/mi} Signal Handling Commands
34600 Signal handling commands are not implemented.
34602 @c @subheading -signal-handle
34604 @c @subheading -signal-list-handle-actions
34606 @c @subheading -signal-list-signal-types
34610 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34611 @node GDB/MI Target Manipulation
34612 @section @sc{gdb/mi} Target Manipulation Commands
34615 @subheading The @code{-target-attach} Command
34616 @findex -target-attach
34618 @subsubheading Synopsis
34621 -target-attach @var{pid} | @var{gid} | @var{file}
34624 Attach to a process @var{pid} or a file @var{file} outside of
34625 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34626 group, the id previously returned by
34627 @samp{-list-thread-groups --available} must be used.
34629 @subsubheading @value{GDBN} Command
34631 The corresponding @value{GDBN} command is @samp{attach}.
34633 @subsubheading Example
34637 =thread-created,id="1"
34638 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34644 @subheading The @code{-target-compare-sections} Command
34645 @findex -target-compare-sections
34647 @subsubheading Synopsis
34650 -target-compare-sections [ @var{section} ]
34653 Compare data of section @var{section} on target to the exec file.
34654 Without the argument, all sections are compared.
34656 @subsubheading @value{GDBN} Command
34658 The @value{GDBN} equivalent is @samp{compare-sections}.
34660 @subsubheading Example
34665 @subheading The @code{-target-detach} Command
34666 @findex -target-detach
34668 @subsubheading Synopsis
34671 -target-detach [ @var{pid} | @var{gid} ]
34674 Detach from the remote target which normally resumes its execution.
34675 If either @var{pid} or @var{gid} is specified, detaches from either
34676 the specified process, or specified thread group. There's no output.
34678 @subsubheading @value{GDBN} Command
34680 The corresponding @value{GDBN} command is @samp{detach}.
34682 @subsubheading Example
34692 @subheading The @code{-target-disconnect} Command
34693 @findex -target-disconnect
34695 @subsubheading Synopsis
34701 Disconnect from the remote target. There's no output and the target is
34702 generally not resumed.
34704 @subsubheading @value{GDBN} Command
34706 The corresponding @value{GDBN} command is @samp{disconnect}.
34708 @subsubheading Example
34718 @subheading The @code{-target-download} Command
34719 @findex -target-download
34721 @subsubheading Synopsis
34727 Loads the executable onto the remote target.
34728 It prints out an update message every half second, which includes the fields:
34732 The name of the section.
34734 The size of what has been sent so far for that section.
34736 The size of the section.
34738 The total size of what was sent so far (the current and the previous sections).
34740 The size of the overall executable to download.
34744 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34745 @sc{gdb/mi} Output Syntax}).
34747 In addition, it prints the name and size of the sections, as they are
34748 downloaded. These messages include the following fields:
34752 The name of the section.
34754 The size of the section.
34756 The size of the overall executable to download.
34760 At the end, a summary is printed.
34762 @subsubheading @value{GDBN} Command
34764 The corresponding @value{GDBN} command is @samp{load}.
34766 @subsubheading Example
34768 Note: each status message appears on a single line. Here the messages
34769 have been broken down so that they can fit onto a page.
34774 +download,@{section=".text",section-size="6668",total-size="9880"@}
34775 +download,@{section=".text",section-sent="512",section-size="6668",
34776 total-sent="512",total-size="9880"@}
34777 +download,@{section=".text",section-sent="1024",section-size="6668",
34778 total-sent="1024",total-size="9880"@}
34779 +download,@{section=".text",section-sent="1536",section-size="6668",
34780 total-sent="1536",total-size="9880"@}
34781 +download,@{section=".text",section-sent="2048",section-size="6668",
34782 total-sent="2048",total-size="9880"@}
34783 +download,@{section=".text",section-sent="2560",section-size="6668",
34784 total-sent="2560",total-size="9880"@}
34785 +download,@{section=".text",section-sent="3072",section-size="6668",
34786 total-sent="3072",total-size="9880"@}
34787 +download,@{section=".text",section-sent="3584",section-size="6668",
34788 total-sent="3584",total-size="9880"@}
34789 +download,@{section=".text",section-sent="4096",section-size="6668",
34790 total-sent="4096",total-size="9880"@}
34791 +download,@{section=".text",section-sent="4608",section-size="6668",
34792 total-sent="4608",total-size="9880"@}
34793 +download,@{section=".text",section-sent="5120",section-size="6668",
34794 total-sent="5120",total-size="9880"@}
34795 +download,@{section=".text",section-sent="5632",section-size="6668",
34796 total-sent="5632",total-size="9880"@}
34797 +download,@{section=".text",section-sent="6144",section-size="6668",
34798 total-sent="6144",total-size="9880"@}
34799 +download,@{section=".text",section-sent="6656",section-size="6668",
34800 total-sent="6656",total-size="9880"@}
34801 +download,@{section=".init",section-size="28",total-size="9880"@}
34802 +download,@{section=".fini",section-size="28",total-size="9880"@}
34803 +download,@{section=".data",section-size="3156",total-size="9880"@}
34804 +download,@{section=".data",section-sent="512",section-size="3156",
34805 total-sent="7236",total-size="9880"@}
34806 +download,@{section=".data",section-sent="1024",section-size="3156",
34807 total-sent="7748",total-size="9880"@}
34808 +download,@{section=".data",section-sent="1536",section-size="3156",
34809 total-sent="8260",total-size="9880"@}
34810 +download,@{section=".data",section-sent="2048",section-size="3156",
34811 total-sent="8772",total-size="9880"@}
34812 +download,@{section=".data",section-sent="2560",section-size="3156",
34813 total-sent="9284",total-size="9880"@}
34814 +download,@{section=".data",section-sent="3072",section-size="3156",
34815 total-sent="9796",total-size="9880"@}
34816 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34823 @subheading The @code{-target-exec-status} Command
34824 @findex -target-exec-status
34826 @subsubheading Synopsis
34829 -target-exec-status
34832 Provide information on the state of the target (whether it is running or
34833 not, for instance).
34835 @subsubheading @value{GDBN} Command
34837 There's no equivalent @value{GDBN} command.
34839 @subsubheading Example
34843 @subheading The @code{-target-list-available-targets} Command
34844 @findex -target-list-available-targets
34846 @subsubheading Synopsis
34849 -target-list-available-targets
34852 List the possible targets to connect to.
34854 @subsubheading @value{GDBN} Command
34856 The corresponding @value{GDBN} command is @samp{help target}.
34858 @subsubheading Example
34862 @subheading The @code{-target-list-current-targets} Command
34863 @findex -target-list-current-targets
34865 @subsubheading Synopsis
34868 -target-list-current-targets
34871 Describe the current target.
34873 @subsubheading @value{GDBN} Command
34875 The corresponding information is printed by @samp{info file} (among
34878 @subsubheading Example
34882 @subheading The @code{-target-list-parameters} Command
34883 @findex -target-list-parameters
34885 @subsubheading Synopsis
34888 -target-list-parameters
34894 @subsubheading @value{GDBN} Command
34898 @subsubheading Example
34902 @subheading The @code{-target-select} Command
34903 @findex -target-select
34905 @subsubheading Synopsis
34908 -target-select @var{type} @var{parameters @dots{}}
34911 Connect @value{GDBN} to the remote target. This command takes two args:
34915 The type of target, for instance @samp{remote}, etc.
34916 @item @var{parameters}
34917 Device names, host names and the like. @xref{Target Commands, ,
34918 Commands for Managing Targets}, for more details.
34921 The output is a connection notification, followed by the address at
34922 which the target program is, in the following form:
34925 ^connected,addr="@var{address}",func="@var{function name}",
34926 args=[@var{arg list}]
34929 @subsubheading @value{GDBN} Command
34931 The corresponding @value{GDBN} command is @samp{target}.
34933 @subsubheading Example
34937 -target-select remote /dev/ttya
34938 ^connected,addr="0xfe00a300",func="??",args=[]
34942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34943 @node GDB/MI File Transfer Commands
34944 @section @sc{gdb/mi} File Transfer Commands
34947 @subheading The @code{-target-file-put} Command
34948 @findex -target-file-put
34950 @subsubheading Synopsis
34953 -target-file-put @var{hostfile} @var{targetfile}
34956 Copy file @var{hostfile} from the host system (the machine running
34957 @value{GDBN}) to @var{targetfile} on the target system.
34959 @subsubheading @value{GDBN} Command
34961 The corresponding @value{GDBN} command is @samp{remote put}.
34963 @subsubheading Example
34967 -target-file-put localfile remotefile
34973 @subheading The @code{-target-file-get} Command
34974 @findex -target-file-get
34976 @subsubheading Synopsis
34979 -target-file-get @var{targetfile} @var{hostfile}
34982 Copy file @var{targetfile} from the target system to @var{hostfile}
34983 on the host system.
34985 @subsubheading @value{GDBN} Command
34987 The corresponding @value{GDBN} command is @samp{remote get}.
34989 @subsubheading Example
34993 -target-file-get remotefile localfile
34999 @subheading The @code{-target-file-delete} Command
35000 @findex -target-file-delete
35002 @subsubheading Synopsis
35005 -target-file-delete @var{targetfile}
35008 Delete @var{targetfile} from the target system.
35010 @subsubheading @value{GDBN} Command
35012 The corresponding @value{GDBN} command is @samp{remote delete}.
35014 @subsubheading Example
35018 -target-file-delete remotefile
35024 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35025 @node GDB/MI Ada Exceptions Commands
35026 @section Ada Exceptions @sc{gdb/mi} Commands
35028 @subheading The @code{-info-ada-exceptions} Command
35029 @findex -info-ada-exceptions
35031 @subsubheading Synopsis
35034 -info-ada-exceptions [ @var{regexp}]
35037 List all Ada exceptions defined within the program being debugged.
35038 With a regular expression @var{regexp}, only those exceptions whose
35039 names match @var{regexp} are listed.
35041 @subsubheading @value{GDBN} Command
35043 The corresponding @value{GDBN} command is @samp{info exceptions}.
35045 @subsubheading Result
35047 The result is a table of Ada exceptions. The following columns are
35048 defined for each exception:
35052 The name of the exception.
35055 The address of the exception.
35059 @subsubheading Example
35062 -info-ada-exceptions aint
35063 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
35064 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
35065 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
35066 body=[@{name="constraint_error",address="0x0000000000613da0"@},
35067 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
35070 @subheading Catching Ada Exceptions
35072 The commands describing how to ask @value{GDBN} to stop when a program
35073 raises an exception are described at @ref{Ada Exception GDB/MI
35074 Catchpoint Commands}.
35077 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35078 @node GDB/MI Support Commands
35079 @section @sc{gdb/mi} Support Commands
35081 Since new commands and features get regularly added to @sc{gdb/mi},
35082 some commands are available to help front-ends query the debugger
35083 about support for these capabilities. Similarly, it is also possible
35084 to query @value{GDBN} about target support of certain features.
35086 @subheading The @code{-info-gdb-mi-command} Command
35087 @cindex @code{-info-gdb-mi-command}
35088 @findex -info-gdb-mi-command
35090 @subsubheading Synopsis
35093 -info-gdb-mi-command @var{cmd_name}
35096 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
35098 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
35099 is technically not part of the command name (@pxref{GDB/MI Input
35100 Syntax}), and thus should be omitted in @var{cmd_name}. However,
35101 for ease of use, this command also accepts the form with the leading
35104 @subsubheading @value{GDBN} Command
35106 There is no corresponding @value{GDBN} command.
35108 @subsubheading Result
35110 The result is a tuple. There is currently only one field:
35114 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
35115 @code{"false"} otherwise.
35119 @subsubheading Example
35121 Here is an example where the @sc{gdb/mi} command does not exist:
35124 -info-gdb-mi-command unsupported-command
35125 ^done,command=@{exists="false"@}
35129 And here is an example where the @sc{gdb/mi} command is known
35133 -info-gdb-mi-command symbol-list-lines
35134 ^done,command=@{exists="true"@}
35137 @subheading The @code{-list-features} Command
35138 @findex -list-features
35139 @cindex supported @sc{gdb/mi} features, list
35141 Returns a list of particular features of the MI protocol that
35142 this version of gdb implements. A feature can be a command,
35143 or a new field in an output of some command, or even an
35144 important bugfix. While a frontend can sometimes detect presence
35145 of a feature at runtime, it is easier to perform detection at debugger
35148 The command returns a list of strings, with each string naming an
35149 available feature. Each returned string is just a name, it does not
35150 have any internal structure. The list of possible feature names
35156 (gdb) -list-features
35157 ^done,result=["feature1","feature2"]
35160 The current list of features is:
35163 @item frozen-varobjs
35164 Indicates support for the @code{-var-set-frozen} command, as well
35165 as possible presense of the @code{frozen} field in the output
35166 of @code{-varobj-create}.
35167 @item pending-breakpoints
35168 Indicates support for the @option{-f} option to the @code{-break-insert}
35171 Indicates Python scripting support, Python-based
35172 pretty-printing commands, and possible presence of the
35173 @samp{display_hint} field in the output of @code{-var-list-children}
35175 Indicates support for the @code{-thread-info} command.
35176 @item data-read-memory-bytes
35177 Indicates support for the @code{-data-read-memory-bytes} and the
35178 @code{-data-write-memory-bytes} commands.
35179 @item breakpoint-notifications
35180 Indicates that changes to breakpoints and breakpoints created via the
35181 CLI will be announced via async records.
35182 @item ada-task-info
35183 Indicates support for the @code{-ada-task-info} command.
35184 @item language-option
35185 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
35186 option (@pxref{Context management}).
35187 @item info-gdb-mi-command
35188 Indicates support for the @code{-info-gdb-mi-command} command.
35189 @item undefined-command-error-code
35190 Indicates support for the "undefined-command" error code in error result
35191 records, produced when trying to execute an undefined @sc{gdb/mi} command
35192 (@pxref{GDB/MI Result Records}).
35193 @item exec-run-start-option
35194 Indicates that the @code{-exec-run} command supports the @option{--start}
35195 option (@pxref{GDB/MI Program Execution}).
35198 @subheading The @code{-list-target-features} Command
35199 @findex -list-target-features
35201 Returns a list of particular features that are supported by the
35202 target. Those features affect the permitted MI commands, but
35203 unlike the features reported by the @code{-list-features} command, the
35204 features depend on which target GDB is using at the moment. Whenever
35205 a target can change, due to commands such as @code{-target-select},
35206 @code{-target-attach} or @code{-exec-run}, the list of target features
35207 may change, and the frontend should obtain it again.
35211 (gdb) -list-target-features
35212 ^done,result=["async"]
35215 The current list of features is:
35219 Indicates that the target is capable of asynchronous command
35220 execution, which means that @value{GDBN} will accept further commands
35221 while the target is running.
35224 Indicates that the target is capable of reverse execution.
35225 @xref{Reverse Execution}, for more information.
35229 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
35230 @node GDB/MI Miscellaneous Commands
35231 @section Miscellaneous @sc{gdb/mi} Commands
35233 @c @subheading -gdb-complete
35235 @subheading The @code{-gdb-exit} Command
35238 @subsubheading Synopsis
35244 Exit @value{GDBN} immediately.
35246 @subsubheading @value{GDBN} Command
35248 Approximately corresponds to @samp{quit}.
35250 @subsubheading Example
35260 @subheading The @code{-exec-abort} Command
35261 @findex -exec-abort
35263 @subsubheading Synopsis
35269 Kill the inferior running program.
35271 @subsubheading @value{GDBN} Command
35273 The corresponding @value{GDBN} command is @samp{kill}.
35275 @subsubheading Example
35280 @subheading The @code{-gdb-set} Command
35283 @subsubheading Synopsis
35289 Set an internal @value{GDBN} variable.
35290 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
35292 @subsubheading @value{GDBN} Command
35294 The corresponding @value{GDBN} command is @samp{set}.
35296 @subsubheading Example
35306 @subheading The @code{-gdb-show} Command
35309 @subsubheading Synopsis
35315 Show the current value of a @value{GDBN} variable.
35317 @subsubheading @value{GDBN} Command
35319 The corresponding @value{GDBN} command is @samp{show}.
35321 @subsubheading Example
35330 @c @subheading -gdb-source
35333 @subheading The @code{-gdb-version} Command
35334 @findex -gdb-version
35336 @subsubheading Synopsis
35342 Show version information for @value{GDBN}. Used mostly in testing.
35344 @subsubheading @value{GDBN} Command
35346 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
35347 default shows this information when you start an interactive session.
35349 @subsubheading Example
35351 @c This example modifies the actual output from GDB to avoid overfull
35357 ~Copyright 2000 Free Software Foundation, Inc.
35358 ~GDB is free software, covered by the GNU General Public License, and
35359 ~you are welcome to change it and/or distribute copies of it under
35360 ~ certain conditions.
35361 ~Type "show copying" to see the conditions.
35362 ~There is absolutely no warranty for GDB. Type "show warranty" for
35364 ~This GDB was configured as
35365 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
35370 @subheading The @code{-list-thread-groups} Command
35371 @findex -list-thread-groups
35373 @subheading Synopsis
35376 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
35379 Lists thread groups (@pxref{Thread groups}). When a single thread
35380 group is passed as the argument, lists the children of that group.
35381 When several thread group are passed, lists information about those
35382 thread groups. Without any parameters, lists information about all
35383 top-level thread groups.
35385 Normally, thread groups that are being debugged are reported.
35386 With the @samp{--available} option, @value{GDBN} reports thread groups
35387 available on the target.
35389 The output of this command may have either a @samp{threads} result or
35390 a @samp{groups} result. The @samp{thread} result has a list of tuples
35391 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
35392 Information}). The @samp{groups} result has a list of tuples as value,
35393 each tuple describing a thread group. If top-level groups are
35394 requested (that is, no parameter is passed), or when several groups
35395 are passed, the output always has a @samp{groups} result. The format
35396 of the @samp{group} result is described below.
35398 To reduce the number of roundtrips it's possible to list thread groups
35399 together with their children, by passing the @samp{--recurse} option
35400 and the recursion depth. Presently, only recursion depth of 1 is
35401 permitted. If this option is present, then every reported thread group
35402 will also include its children, either as @samp{group} or
35403 @samp{threads} field.
35405 In general, any combination of option and parameters is permitted, with
35406 the following caveats:
35410 When a single thread group is passed, the output will typically
35411 be the @samp{threads} result. Because threads may not contain
35412 anything, the @samp{recurse} option will be ignored.
35415 When the @samp{--available} option is passed, limited information may
35416 be available. In particular, the list of threads of a process might
35417 be inaccessible. Further, specifying specific thread groups might
35418 not give any performance advantage over listing all thread groups.
35419 The frontend should assume that @samp{-list-thread-groups --available}
35420 is always an expensive operation and cache the results.
35424 The @samp{groups} result is a list of tuples, where each tuple may
35425 have the following fields:
35429 Identifier of the thread group. This field is always present.
35430 The identifier is an opaque string; frontends should not try to
35431 convert it to an integer, even though it might look like one.
35434 The type of the thread group. At present, only @samp{process} is a
35438 The target-specific process identifier. This field is only present
35439 for thread groups of type @samp{process} and only if the process exists.
35442 The number of children this thread group has. This field may be
35443 absent for an available thread group.
35446 This field has a list of tuples as value, each tuple describing a
35447 thread. It may be present if the @samp{--recurse} option is
35448 specified, and it's actually possible to obtain the threads.
35451 This field is a list of integers, each identifying a core that one
35452 thread of the group is running on. This field may be absent if
35453 such information is not available.
35456 The name of the executable file that corresponds to this thread group.
35457 The field is only present for thread groups of type @samp{process},
35458 and only if there is a corresponding executable file.
35462 @subheading Example
35466 -list-thread-groups
35467 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
35468 -list-thread-groups 17
35469 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
35470 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
35471 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
35472 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
35473 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
35474 -list-thread-groups --available
35475 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
35476 -list-thread-groups --available --recurse 1
35477 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35478 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35479 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
35480 -list-thread-groups --available --recurse 1 17 18
35481 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
35482 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
35483 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
35486 @subheading The @code{-info-os} Command
35489 @subsubheading Synopsis
35492 -info-os [ @var{type} ]
35495 If no argument is supplied, the command returns a table of available
35496 operating-system-specific information types. If one of these types is
35497 supplied as an argument @var{type}, then the command returns a table
35498 of data of that type.
35500 The types of information available depend on the target operating
35503 @subsubheading @value{GDBN} Command
35505 The corresponding @value{GDBN} command is @samp{info os}.
35507 @subsubheading Example
35509 When run on a @sc{gnu}/Linux system, the output will look something
35515 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
35516 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
35517 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
35518 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
35519 body=[item=@{col0="processes",col1="Listing of all processes",
35520 col2="Processes"@},
35521 item=@{col0="procgroups",col1="Listing of all process groups",
35522 col2="Process groups"@},
35523 item=@{col0="threads",col1="Listing of all threads",
35525 item=@{col0="files",col1="Listing of all file descriptors",
35526 col2="File descriptors"@},
35527 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
35529 item=@{col0="shm",col1="Listing of all shared-memory regions",
35530 col2="Shared-memory regions"@},
35531 item=@{col0="semaphores",col1="Listing of all semaphores",
35532 col2="Semaphores"@},
35533 item=@{col0="msg",col1="Listing of all message queues",
35534 col2="Message queues"@},
35535 item=@{col0="modules",col1="Listing of all loaded kernel modules",
35536 col2="Kernel modules"@}]@}
35539 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
35540 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
35541 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
35542 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
35543 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
35544 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
35545 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
35546 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
35548 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
35549 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
35553 (Note that the MI output here includes a @code{"Title"} column that
35554 does not appear in command-line @code{info os}; this column is useful
35555 for MI clients that want to enumerate the types of data, such as in a
35556 popup menu, but is needless clutter on the command line, and
35557 @code{info os} omits it.)
35559 @subheading The @code{-add-inferior} Command
35560 @findex -add-inferior
35562 @subheading Synopsis
35568 Creates a new inferior (@pxref{Inferiors and Programs}). The created
35569 inferior is not associated with any executable. Such association may
35570 be established with the @samp{-file-exec-and-symbols} command
35571 (@pxref{GDB/MI File Commands}). The command response has a single
35572 field, @samp{inferior}, whose value is the identifier of the
35573 thread group corresponding to the new inferior.
35575 @subheading Example
35580 ^done,inferior="i3"
35583 @subheading The @code{-interpreter-exec} Command
35584 @findex -interpreter-exec
35586 @subheading Synopsis
35589 -interpreter-exec @var{interpreter} @var{command}
35591 @anchor{-interpreter-exec}
35593 Execute the specified @var{command} in the given @var{interpreter}.
35595 @subheading @value{GDBN} Command
35597 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
35599 @subheading Example
35603 -interpreter-exec console "break main"
35604 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
35605 &"During symbol reading, bad structure-type format.\n"
35606 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
35611 @subheading The @code{-inferior-tty-set} Command
35612 @findex -inferior-tty-set
35614 @subheading Synopsis
35617 -inferior-tty-set /dev/pts/1
35620 Set terminal for future runs of the program being debugged.
35622 @subheading @value{GDBN} Command
35624 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
35626 @subheading Example
35630 -inferior-tty-set /dev/pts/1
35635 @subheading The @code{-inferior-tty-show} Command
35636 @findex -inferior-tty-show
35638 @subheading Synopsis
35644 Show terminal for future runs of program being debugged.
35646 @subheading @value{GDBN} Command
35648 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
35650 @subheading Example
35654 -inferior-tty-set /dev/pts/1
35658 ^done,inferior_tty_terminal="/dev/pts/1"
35662 @subheading The @code{-enable-timings} Command
35663 @findex -enable-timings
35665 @subheading Synopsis
35668 -enable-timings [yes | no]
35671 Toggle the printing of the wallclock, user and system times for an MI
35672 command as a field in its output. This command is to help frontend
35673 developers optimize the performance of their code. No argument is
35674 equivalent to @samp{yes}.
35676 @subheading @value{GDBN} Command
35680 @subheading Example
35688 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
35689 addr="0x080484ed",func="main",file="myprog.c",
35690 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
35692 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
35700 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
35701 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
35702 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
35703 fullname="/home/nickrob/myprog.c",line="73"@}
35708 @chapter @value{GDBN} Annotations
35710 This chapter describes annotations in @value{GDBN}. Annotations were
35711 designed to interface @value{GDBN} to graphical user interfaces or other
35712 similar programs which want to interact with @value{GDBN} at a
35713 relatively high level.
35715 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35719 This is Edition @value{EDITION}, @value{DATE}.
35723 * Annotations Overview:: What annotations are; the general syntax.
35724 * Server Prefix:: Issuing a command without affecting user state.
35725 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35726 * Errors:: Annotations for error messages.
35727 * Invalidation:: Some annotations describe things now invalid.
35728 * Annotations for Running::
35729 Whether the program is running, how it stopped, etc.
35730 * Source Annotations:: Annotations describing source code.
35733 @node Annotations Overview
35734 @section What is an Annotation?
35735 @cindex annotations
35737 Annotations start with a newline character, two @samp{control-z}
35738 characters, and the name of the annotation. If there is no additional
35739 information associated with this annotation, the name of the annotation
35740 is followed immediately by a newline. If there is additional
35741 information, the name of the annotation is followed by a space, the
35742 additional information, and a newline. The additional information
35743 cannot contain newline characters.
35745 Any output not beginning with a newline and two @samp{control-z}
35746 characters denotes literal output from @value{GDBN}. Currently there is
35747 no need for @value{GDBN} to output a newline followed by two
35748 @samp{control-z} characters, but if there was such a need, the
35749 annotations could be extended with an @samp{escape} annotation which
35750 means those three characters as output.
35752 The annotation @var{level}, which is specified using the
35753 @option{--annotate} command line option (@pxref{Mode Options}), controls
35754 how much information @value{GDBN} prints together with its prompt,
35755 values of expressions, source lines, and other types of output. Level 0
35756 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35757 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35758 for programs that control @value{GDBN}, and level 2 annotations have
35759 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35760 Interface, annotate, GDB's Obsolete Annotations}).
35763 @kindex set annotate
35764 @item set annotate @var{level}
35765 The @value{GDBN} command @code{set annotate} sets the level of
35766 annotations to the specified @var{level}.
35768 @item show annotate
35769 @kindex show annotate
35770 Show the current annotation level.
35773 This chapter describes level 3 annotations.
35775 A simple example of starting up @value{GDBN} with annotations is:
35778 $ @kbd{gdb --annotate=3}
35780 Copyright 2003 Free Software Foundation, Inc.
35781 GDB is free software, covered by the GNU General Public License,
35782 and you are welcome to change it and/or distribute copies of it
35783 under certain conditions.
35784 Type "show copying" to see the conditions.
35785 There is absolutely no warranty for GDB. Type "show warranty"
35787 This GDB was configured as "i386-pc-linux-gnu"
35798 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35799 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35800 denotes a @samp{control-z} character) are annotations; the rest is
35801 output from @value{GDBN}.
35803 @node Server Prefix
35804 @section The Server Prefix
35805 @cindex server prefix
35807 If you prefix a command with @samp{server } then it will not affect
35808 the command history, nor will it affect @value{GDBN}'s notion of which
35809 command to repeat if @key{RET} is pressed on a line by itself. This
35810 means that commands can be run behind a user's back by a front-end in
35811 a transparent manner.
35813 The @code{server } prefix does not affect the recording of values into
35814 the value history; to print a value without recording it into the
35815 value history, use the @code{output} command instead of the
35816 @code{print} command.
35818 Using this prefix also disables confirmation requests
35819 (@pxref{confirmation requests}).
35822 @section Annotation for @value{GDBN} Input
35824 @cindex annotations for prompts
35825 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35826 to know when to send output, when the output from a given command is
35829 Different kinds of input each have a different @dfn{input type}. Each
35830 input type has three annotations: a @code{pre-} annotation, which
35831 denotes the beginning of any prompt which is being output, a plain
35832 annotation, which denotes the end of the prompt, and then a @code{post-}
35833 annotation which denotes the end of any echo which may (or may not) be
35834 associated with the input. For example, the @code{prompt} input type
35835 features the following annotations:
35843 The input types are
35846 @findex pre-prompt annotation
35847 @findex prompt annotation
35848 @findex post-prompt annotation
35850 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35852 @findex pre-commands annotation
35853 @findex commands annotation
35854 @findex post-commands annotation
35856 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35857 command. The annotations are repeated for each command which is input.
35859 @findex pre-overload-choice annotation
35860 @findex overload-choice annotation
35861 @findex post-overload-choice annotation
35862 @item overload-choice
35863 When @value{GDBN} wants the user to select between various overloaded functions.
35865 @findex pre-query annotation
35866 @findex query annotation
35867 @findex post-query annotation
35869 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35871 @findex pre-prompt-for-continue annotation
35872 @findex prompt-for-continue annotation
35873 @findex post-prompt-for-continue annotation
35874 @item prompt-for-continue
35875 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35876 expect this to work well; instead use @code{set height 0} to disable
35877 prompting. This is because the counting of lines is buggy in the
35878 presence of annotations.
35883 @cindex annotations for errors, warnings and interrupts
35885 @findex quit annotation
35890 This annotation occurs right before @value{GDBN} responds to an interrupt.
35892 @findex error annotation
35897 This annotation occurs right before @value{GDBN} responds to an error.
35899 Quit and error annotations indicate that any annotations which @value{GDBN} was
35900 in the middle of may end abruptly. For example, if a
35901 @code{value-history-begin} annotation is followed by a @code{error}, one
35902 cannot expect to receive the matching @code{value-history-end}. One
35903 cannot expect not to receive it either, however; an error annotation
35904 does not necessarily mean that @value{GDBN} is immediately returning all the way
35907 @findex error-begin annotation
35908 A quit or error annotation may be preceded by
35914 Any output between that and the quit or error annotation is the error
35917 Warning messages are not yet annotated.
35918 @c If we want to change that, need to fix warning(), type_error(),
35919 @c range_error(), and possibly other places.
35922 @section Invalidation Notices
35924 @cindex annotations for invalidation messages
35925 The following annotations say that certain pieces of state may have
35929 @findex frames-invalid annotation
35930 @item ^Z^Zframes-invalid
35932 The frames (for example, output from the @code{backtrace} command) may
35935 @findex breakpoints-invalid annotation
35936 @item ^Z^Zbreakpoints-invalid
35938 The breakpoints may have changed. For example, the user just added or
35939 deleted a breakpoint.
35942 @node Annotations for Running
35943 @section Running the Program
35944 @cindex annotations for running programs
35946 @findex starting annotation
35947 @findex stopping annotation
35948 When the program starts executing due to a @value{GDBN} command such as
35949 @code{step} or @code{continue},
35955 is output. When the program stops,
35961 is output. Before the @code{stopped} annotation, a variety of
35962 annotations describe how the program stopped.
35965 @findex exited annotation
35966 @item ^Z^Zexited @var{exit-status}
35967 The program exited, and @var{exit-status} is the exit status (zero for
35968 successful exit, otherwise nonzero).
35970 @findex signalled annotation
35971 @findex signal-name annotation
35972 @findex signal-name-end annotation
35973 @findex signal-string annotation
35974 @findex signal-string-end annotation
35975 @item ^Z^Zsignalled
35976 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35977 annotation continues:
35983 ^Z^Zsignal-name-end
35987 ^Z^Zsignal-string-end
35992 where @var{name} is the name of the signal, such as @code{SIGILL} or
35993 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35994 as @code{Illegal Instruction} or @code{Segmentation fault}.
35995 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35996 user's benefit and have no particular format.
35998 @findex signal annotation
36000 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
36001 just saying that the program received the signal, not that it was
36002 terminated with it.
36004 @findex breakpoint annotation
36005 @item ^Z^Zbreakpoint @var{number}
36006 The program hit breakpoint number @var{number}.
36008 @findex watchpoint annotation
36009 @item ^Z^Zwatchpoint @var{number}
36010 The program hit watchpoint number @var{number}.
36013 @node Source Annotations
36014 @section Displaying Source
36015 @cindex annotations for source display
36017 @findex source annotation
36018 The following annotation is used instead of displaying source code:
36021 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
36024 where @var{filename} is an absolute file name indicating which source
36025 file, @var{line} is the line number within that file (where 1 is the
36026 first line in the file), @var{character} is the character position
36027 within the file (where 0 is the first character in the file) (for most
36028 debug formats this will necessarily point to the beginning of a line),
36029 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
36030 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
36031 @var{addr} is the address in the target program associated with the
36032 source which is being displayed. @var{addr} is in the form @samp{0x}
36033 followed by one or more lowercase hex digits (note that this does not
36034 depend on the language).
36036 @node JIT Interface
36037 @chapter JIT Compilation Interface
36038 @cindex just-in-time compilation
36039 @cindex JIT compilation interface
36041 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
36042 interface. A JIT compiler is a program or library that generates native
36043 executable code at runtime and executes it, usually in order to achieve good
36044 performance while maintaining platform independence.
36046 Programs that use JIT compilation are normally difficult to debug because
36047 portions of their code are generated at runtime, instead of being loaded from
36048 object files, which is where @value{GDBN} normally finds the program's symbols
36049 and debug information. In order to debug programs that use JIT compilation,
36050 @value{GDBN} has an interface that allows the program to register in-memory
36051 symbol files with @value{GDBN} at runtime.
36053 If you are using @value{GDBN} to debug a program that uses this interface, then
36054 it should work transparently so long as you have not stripped the binary. If
36055 you are developing a JIT compiler, then the interface is documented in the rest
36056 of this chapter. At this time, the only known client of this interface is the
36059 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
36060 JIT compiler communicates with @value{GDBN} by writing data into a global
36061 variable and calling a fuction at a well-known symbol. When @value{GDBN}
36062 attaches, it reads a linked list of symbol files from the global variable to
36063 find existing code, and puts a breakpoint in the function so that it can find
36064 out about additional code.
36067 * Declarations:: Relevant C struct declarations
36068 * Registering Code:: Steps to register code
36069 * Unregistering Code:: Steps to unregister code
36070 * Custom Debug Info:: Emit debug information in a custom format
36074 @section JIT Declarations
36076 These are the relevant struct declarations that a C program should include to
36077 implement the interface:
36087 struct jit_code_entry
36089 struct jit_code_entry *next_entry;
36090 struct jit_code_entry *prev_entry;
36091 const char *symfile_addr;
36092 uint64_t symfile_size;
36095 struct jit_descriptor
36098 /* This type should be jit_actions_t, but we use uint32_t
36099 to be explicit about the bitwidth. */
36100 uint32_t action_flag;
36101 struct jit_code_entry *relevant_entry;
36102 struct jit_code_entry *first_entry;
36105 /* GDB puts a breakpoint in this function. */
36106 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
36108 /* Make sure to specify the version statically, because the
36109 debugger may check the version before we can set it. */
36110 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
36113 If the JIT is multi-threaded, then it is important that the JIT synchronize any
36114 modifications to this global data properly, which can easily be done by putting
36115 a global mutex around modifications to these structures.
36117 @node Registering Code
36118 @section Registering Code
36120 To register code with @value{GDBN}, the JIT should follow this protocol:
36124 Generate an object file in memory with symbols and other desired debug
36125 information. The file must include the virtual addresses of the sections.
36128 Create a code entry for the file, which gives the start and size of the symbol
36132 Add it to the linked list in the JIT descriptor.
36135 Point the relevant_entry field of the descriptor at the entry.
36138 Set @code{action_flag} to @code{JIT_REGISTER} and call
36139 @code{__jit_debug_register_code}.
36142 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
36143 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
36144 new code. However, the linked list must still be maintained in order to allow
36145 @value{GDBN} to attach to a running process and still find the symbol files.
36147 @node Unregistering Code
36148 @section Unregistering Code
36150 If code is freed, then the JIT should use the following protocol:
36154 Remove the code entry corresponding to the code from the linked list.
36157 Point the @code{relevant_entry} field of the descriptor at the code entry.
36160 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
36161 @code{__jit_debug_register_code}.
36164 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
36165 and the JIT will leak the memory used for the associated symbol files.
36167 @node Custom Debug Info
36168 @section Custom Debug Info
36169 @cindex custom JIT debug info
36170 @cindex JIT debug info reader
36172 Generating debug information in platform-native file formats (like ELF
36173 or COFF) may be an overkill for JIT compilers; especially if all the
36174 debug info is used for is displaying a meaningful backtrace. The
36175 issue can be resolved by having the JIT writers decide on a debug info
36176 format and also provide a reader that parses the debug info generated
36177 by the JIT compiler. This section gives a brief overview on writing
36178 such a parser. More specific details can be found in the source file
36179 @file{gdb/jit-reader.in}, which is also installed as a header at
36180 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
36182 The reader is implemented as a shared object (so this functionality is
36183 not available on platforms which don't allow loading shared objects at
36184 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
36185 @code{jit-reader-unload} are provided, to be used to load and unload
36186 the readers from a preconfigured directory. Once loaded, the shared
36187 object is used the parse the debug information emitted by the JIT
36191 * Using JIT Debug Info Readers:: How to use supplied readers correctly
36192 * Writing JIT Debug Info Readers:: Creating a debug-info reader
36195 @node Using JIT Debug Info Readers
36196 @subsection Using JIT Debug Info Readers
36197 @kindex jit-reader-load
36198 @kindex jit-reader-unload
36200 Readers can be loaded and unloaded using the @code{jit-reader-load}
36201 and @code{jit-reader-unload} commands.
36204 @item jit-reader-load @var{reader}
36205 Load the JIT reader named @var{reader}. @var{reader} is a shared
36206 object specified as either an absolute or a relative file name. In
36207 the latter case, @value{GDBN} will try to load the reader from a
36208 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
36209 system (here @var{libdir} is the system library directory, often
36210 @file{/usr/local/lib}).
36212 Only one reader can be active at a time; trying to load a second
36213 reader when one is already loaded will result in @value{GDBN}
36214 reporting an error. A new JIT reader can be loaded by first unloading
36215 the current one using @code{jit-reader-unload} and then invoking
36216 @code{jit-reader-load}.
36218 @item jit-reader-unload
36219 Unload the currently loaded JIT reader.
36223 @node Writing JIT Debug Info Readers
36224 @subsection Writing JIT Debug Info Readers
36225 @cindex writing JIT debug info readers
36227 As mentioned, a reader is essentially a shared object conforming to a
36228 certain ABI. This ABI is described in @file{jit-reader.h}.
36230 @file{jit-reader.h} defines the structures, macros and functions
36231 required to write a reader. It is installed (along with
36232 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
36233 the system include directory.
36235 Readers need to be released under a GPL compatible license. A reader
36236 can be declared as released under such a license by placing the macro
36237 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
36239 The entry point for readers is the symbol @code{gdb_init_reader},
36240 which is expected to be a function with the prototype
36242 @findex gdb_init_reader
36244 extern struct gdb_reader_funcs *gdb_init_reader (void);
36247 @cindex @code{struct gdb_reader_funcs}
36249 @code{struct gdb_reader_funcs} contains a set of pointers to callback
36250 functions. These functions are executed to read the debug info
36251 generated by the JIT compiler (@code{read}), to unwind stack frames
36252 (@code{unwind}) and to create canonical frame IDs
36253 (@code{get_Frame_id}). It also has a callback that is called when the
36254 reader is being unloaded (@code{destroy}). The struct looks like this
36257 struct gdb_reader_funcs
36259 /* Must be set to GDB_READER_INTERFACE_VERSION. */
36260 int reader_version;
36262 /* For use by the reader. */
36265 gdb_read_debug_info *read;
36266 gdb_unwind_frame *unwind;
36267 gdb_get_frame_id *get_frame_id;
36268 gdb_destroy_reader *destroy;
36272 @cindex @code{struct gdb_symbol_callbacks}
36273 @cindex @code{struct gdb_unwind_callbacks}
36275 The callbacks are provided with another set of callbacks by
36276 @value{GDBN} to do their job. For @code{read}, these callbacks are
36277 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
36278 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
36279 @code{struct gdb_symbol_callbacks} has callbacks to create new object
36280 files and new symbol tables inside those object files. @code{struct
36281 gdb_unwind_callbacks} has callbacks to read registers off the current
36282 frame and to write out the values of the registers in the previous
36283 frame. Both have a callback (@code{target_read}) to read bytes off the
36284 target's address space.
36286 @node In-Process Agent
36287 @chapter In-Process Agent
36288 @cindex debugging agent
36289 The traditional debugging model is conceptually low-speed, but works fine,
36290 because most bugs can be reproduced in debugging-mode execution. However,
36291 as multi-core or many-core processors are becoming mainstream, and
36292 multi-threaded programs become more and more popular, there should be more
36293 and more bugs that only manifest themselves at normal-mode execution, for
36294 example, thread races, because debugger's interference with the program's
36295 timing may conceal the bugs. On the other hand, in some applications,
36296 it is not feasible for the debugger to interrupt the program's execution
36297 long enough for the developer to learn anything helpful about its behavior.
36298 If the program's correctness depends on its real-time behavior, delays
36299 introduced by a debugger might cause the program to fail, even when the
36300 code itself is correct. It is useful to be able to observe the program's
36301 behavior without interrupting it.
36303 Therefore, traditional debugging model is too intrusive to reproduce
36304 some bugs. In order to reduce the interference with the program, we can
36305 reduce the number of operations performed by debugger. The
36306 @dfn{In-Process Agent}, a shared library, is running within the same
36307 process with inferior, and is able to perform some debugging operations
36308 itself. As a result, debugger is only involved when necessary, and
36309 performance of debugging can be improved accordingly. Note that
36310 interference with program can be reduced but can't be removed completely,
36311 because the in-process agent will still stop or slow down the program.
36313 The in-process agent can interpret and execute Agent Expressions
36314 (@pxref{Agent Expressions}) during performing debugging operations. The
36315 agent expressions can be used for different purposes, such as collecting
36316 data in tracepoints, and condition evaluation in breakpoints.
36318 @anchor{Control Agent}
36319 You can control whether the in-process agent is used as an aid for
36320 debugging with the following commands:
36323 @kindex set agent on
36325 Causes the in-process agent to perform some operations on behalf of the
36326 debugger. Just which operations requested by the user will be done
36327 by the in-process agent depends on the its capabilities. For example,
36328 if you request to evaluate breakpoint conditions in the in-process agent,
36329 and the in-process agent has such capability as well, then breakpoint
36330 conditions will be evaluated in the in-process agent.
36332 @kindex set agent off
36333 @item set agent off
36334 Disables execution of debugging operations by the in-process agent. All
36335 of the operations will be performed by @value{GDBN}.
36339 Display the current setting of execution of debugging operations by
36340 the in-process agent.
36344 * In-Process Agent Protocol::
36347 @node In-Process Agent Protocol
36348 @section In-Process Agent Protocol
36349 @cindex in-process agent protocol
36351 The in-process agent is able to communicate with both @value{GDBN} and
36352 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
36353 used for communications between @value{GDBN} or GDBserver and the IPA.
36354 In general, @value{GDBN} or GDBserver sends commands
36355 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
36356 in-process agent replies back with the return result of the command, or
36357 some other information. The data sent to in-process agent is composed
36358 of primitive data types, such as 4-byte or 8-byte type, and composite
36359 types, which are called objects (@pxref{IPA Protocol Objects}).
36362 * IPA Protocol Objects::
36363 * IPA Protocol Commands::
36366 @node IPA Protocol Objects
36367 @subsection IPA Protocol Objects
36368 @cindex ipa protocol objects
36370 The commands sent to and results received from agent may contain some
36371 complex data types called @dfn{objects}.
36373 The in-process agent is running on the same machine with @value{GDBN}
36374 or GDBserver, so it doesn't have to handle as much differences between
36375 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
36376 However, there are still some differences of two ends in two processes:
36380 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
36381 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
36383 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
36384 GDBserver is compiled with one, and in-process agent is compiled with
36388 Here are the IPA Protocol Objects:
36392 agent expression object. It represents an agent expression
36393 (@pxref{Agent Expressions}).
36394 @anchor{agent expression object}
36396 tracepoint action object. It represents a tracepoint action
36397 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
36398 memory, static trace data and to evaluate expression.
36399 @anchor{tracepoint action object}
36401 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
36402 @anchor{tracepoint object}
36406 The following table describes important attributes of each IPA protocol
36409 @multitable @columnfractions .30 .20 .50
36410 @headitem Name @tab Size @tab Description
36411 @item @emph{agent expression object} @tab @tab
36412 @item length @tab 4 @tab length of bytes code
36413 @item byte code @tab @var{length} @tab contents of byte code
36414 @item @emph{tracepoint action for collecting memory} @tab @tab
36415 @item 'M' @tab 1 @tab type of tracepoint action
36416 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
36417 address of the lowest byte to collect, otherwise @var{addr} is the offset
36418 of @var{basereg} for memory collecting.
36419 @item len @tab 8 @tab length of memory for collecting
36420 @item basereg @tab 4 @tab the register number containing the starting
36421 memory address for collecting.
36422 @item @emph{tracepoint action for collecting registers} @tab @tab
36423 @item 'R' @tab 1 @tab type of tracepoint action
36424 @item @emph{tracepoint action for collecting static trace data} @tab @tab
36425 @item 'L' @tab 1 @tab type of tracepoint action
36426 @item @emph{tracepoint action for expression evaluation} @tab @tab
36427 @item 'X' @tab 1 @tab type of tracepoint action
36428 @item agent expression @tab length of @tab @ref{agent expression object}
36429 @item @emph{tracepoint object} @tab @tab
36430 @item number @tab 4 @tab number of tracepoint
36431 @item address @tab 8 @tab address of tracepoint inserted on
36432 @item type @tab 4 @tab type of tracepoint
36433 @item enabled @tab 1 @tab enable or disable of tracepoint
36434 @item step_count @tab 8 @tab step
36435 @item pass_count @tab 8 @tab pass
36436 @item numactions @tab 4 @tab number of tracepoint actions
36437 @item hit count @tab 8 @tab hit count
36438 @item trace frame usage @tab 8 @tab trace frame usage
36439 @item compiled_cond @tab 8 @tab compiled condition
36440 @item orig_size @tab 8 @tab orig size
36441 @item condition @tab 4 if condition is NULL otherwise length of
36442 @ref{agent expression object}
36443 @tab zero if condition is NULL, otherwise is
36444 @ref{agent expression object}
36445 @item actions @tab variable
36446 @tab numactions number of @ref{tracepoint action object}
36449 @node IPA Protocol Commands
36450 @subsection IPA Protocol Commands
36451 @cindex ipa protocol commands
36453 The spaces in each command are delimiters to ease reading this commands
36454 specification. They don't exist in real commands.
36458 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
36459 Installs a new fast tracepoint described by @var{tracepoint_object}
36460 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
36461 head of @dfn{jumppad}, which is used to jump to data collection routine
36466 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
36467 @var{target_address} is address of tracepoint in the inferior.
36468 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
36469 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
36470 @var{fjump} contains a sequence of instructions jump to jumppad entry.
36471 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
36478 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
36479 is about to kill inferiors.
36487 @item probe_marker_at:@var{address}
36488 Asks in-process agent to probe the marker at @var{address}.
36495 @item unprobe_marker_at:@var{address}
36496 Asks in-process agent to unprobe the marker at @var{address}.
36500 @chapter Reporting Bugs in @value{GDBN}
36501 @cindex bugs in @value{GDBN}
36502 @cindex reporting bugs in @value{GDBN}
36504 Your bug reports play an essential role in making @value{GDBN} reliable.
36506 Reporting a bug may help you by bringing a solution to your problem, or it
36507 may not. But in any case the principal function of a bug report is to help
36508 the entire community by making the next version of @value{GDBN} work better. Bug
36509 reports are your contribution to the maintenance of @value{GDBN}.
36511 In order for a bug report to serve its purpose, you must include the
36512 information that enables us to fix the bug.
36515 * Bug Criteria:: Have you found a bug?
36516 * Bug Reporting:: How to report bugs
36520 @section Have You Found a Bug?
36521 @cindex bug criteria
36523 If you are not sure whether you have found a bug, here are some guidelines:
36526 @cindex fatal signal
36527 @cindex debugger crash
36528 @cindex crash of debugger
36530 If the debugger gets a fatal signal, for any input whatever, that is a
36531 @value{GDBN} bug. Reliable debuggers never crash.
36533 @cindex error on valid input
36535 If @value{GDBN} produces an error message for valid input, that is a
36536 bug. (Note that if you're cross debugging, the problem may also be
36537 somewhere in the connection to the target.)
36539 @cindex invalid input
36541 If @value{GDBN} does not produce an error message for invalid input,
36542 that is a bug. However, you should note that your idea of
36543 ``invalid input'' might be our idea of ``an extension'' or ``support
36544 for traditional practice''.
36547 If you are an experienced user of debugging tools, your suggestions
36548 for improvement of @value{GDBN} are welcome in any case.
36551 @node Bug Reporting
36552 @section How to Report Bugs
36553 @cindex bug reports
36554 @cindex @value{GDBN} bugs, reporting
36556 A number of companies and individuals offer support for @sc{gnu} products.
36557 If you obtained @value{GDBN} from a support organization, we recommend you
36558 contact that organization first.
36560 You can find contact information for many support companies and
36561 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
36563 @c should add a web page ref...
36566 @ifset BUGURL_DEFAULT
36567 In any event, we also recommend that you submit bug reports for
36568 @value{GDBN}. The preferred method is to submit them directly using
36569 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
36570 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
36573 @strong{Do not send bug reports to @samp{info-gdb}, or to
36574 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
36575 not want to receive bug reports. Those that do have arranged to receive
36578 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
36579 serves as a repeater. The mailing list and the newsgroup carry exactly
36580 the same messages. Often people think of posting bug reports to the
36581 newsgroup instead of mailing them. This appears to work, but it has one
36582 problem which can be crucial: a newsgroup posting often lacks a mail
36583 path back to the sender. Thus, if we need to ask for more information,
36584 we may be unable to reach you. For this reason, it is better to send
36585 bug reports to the mailing list.
36587 @ifclear BUGURL_DEFAULT
36588 In any event, we also recommend that you submit bug reports for
36589 @value{GDBN} to @value{BUGURL}.
36593 The fundamental principle of reporting bugs usefully is this:
36594 @strong{report all the facts}. If you are not sure whether to state a
36595 fact or leave it out, state it!
36597 Often people omit facts because they think they know what causes the
36598 problem and assume that some details do not matter. Thus, you might
36599 assume that the name of the variable you use in an example does not matter.
36600 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
36601 stray memory reference which happens to fetch from the location where that
36602 name is stored in memory; perhaps, if the name were different, the contents
36603 of that location would fool the debugger into doing the right thing despite
36604 the bug. Play it safe and give a specific, complete example. That is the
36605 easiest thing for you to do, and the most helpful.
36607 Keep in mind that the purpose of a bug report is to enable us to fix the
36608 bug. It may be that the bug has been reported previously, but neither
36609 you nor we can know that unless your bug report is complete and
36612 Sometimes people give a few sketchy facts and ask, ``Does this ring a
36613 bell?'' Those bug reports are useless, and we urge everyone to
36614 @emph{refuse to respond to them} except to chide the sender to report
36617 To enable us to fix the bug, you should include all these things:
36621 The version of @value{GDBN}. @value{GDBN} announces it if you start
36622 with no arguments; you can also print it at any time using @code{show
36625 Without this, we will not know whether there is any point in looking for
36626 the bug in the current version of @value{GDBN}.
36629 The type of machine you are using, and the operating system name and
36633 The details of the @value{GDBN} build-time configuration.
36634 @value{GDBN} shows these details if you invoke it with the
36635 @option{--configuration} command-line option, or if you type
36636 @code{show configuration} at @value{GDBN}'s prompt.
36639 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
36640 ``@value{GCC}--2.8.1''.
36643 What compiler (and its version) was used to compile the program you are
36644 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
36645 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
36646 to get this information; for other compilers, see the documentation for
36650 The command arguments you gave the compiler to compile your example and
36651 observe the bug. For example, did you use @samp{-O}? To guarantee
36652 you will not omit something important, list them all. A copy of the
36653 Makefile (or the output from make) is sufficient.
36655 If we were to try to guess the arguments, we would probably guess wrong
36656 and then we might not encounter the bug.
36659 A complete input script, and all necessary source files, that will
36663 A description of what behavior you observe that you believe is
36664 incorrect. For example, ``It gets a fatal signal.''
36666 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
36667 will certainly notice it. But if the bug is incorrect output, we might
36668 not notice unless it is glaringly wrong. You might as well not give us
36669 a chance to make a mistake.
36671 Even if the problem you experience is a fatal signal, you should still
36672 say so explicitly. Suppose something strange is going on, such as, your
36673 copy of @value{GDBN} is out of synch, or you have encountered a bug in
36674 the C library on your system. (This has happened!) Your copy might
36675 crash and ours would not. If you told us to expect a crash, then when
36676 ours fails to crash, we would know that the bug was not happening for
36677 us. If you had not told us to expect a crash, then we would not be able
36678 to draw any conclusion from our observations.
36681 @cindex recording a session script
36682 To collect all this information, you can use a session recording program
36683 such as @command{script}, which is available on many Unix systems.
36684 Just run your @value{GDBN} session inside @command{script} and then
36685 include the @file{typescript} file with your bug report.
36687 Another way to record a @value{GDBN} session is to run @value{GDBN}
36688 inside Emacs and then save the entire buffer to a file.
36691 If you wish to suggest changes to the @value{GDBN} source, send us context
36692 diffs. If you even discuss something in the @value{GDBN} source, refer to
36693 it by context, not by line number.
36695 The line numbers in our development sources will not match those in your
36696 sources. Your line numbers would convey no useful information to us.
36700 Here are some things that are not necessary:
36704 A description of the envelope of the bug.
36706 Often people who encounter a bug spend a lot of time investigating
36707 which changes to the input file will make the bug go away and which
36708 changes will not affect it.
36710 This is often time consuming and not very useful, because the way we
36711 will find the bug is by running a single example under the debugger
36712 with breakpoints, not by pure deduction from a series of examples.
36713 We recommend that you save your time for something else.
36715 Of course, if you can find a simpler example to report @emph{instead}
36716 of the original one, that is a convenience for us. Errors in the
36717 output will be easier to spot, running under the debugger will take
36718 less time, and so on.
36720 However, simplification is not vital; if you do not want to do this,
36721 report the bug anyway and send us the entire test case you used.
36724 A patch for the bug.
36726 A patch for the bug does help us if it is a good one. But do not omit
36727 the necessary information, such as the test case, on the assumption that
36728 a patch is all we need. We might see problems with your patch and decide
36729 to fix the problem another way, or we might not understand it at all.
36731 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36732 construct an example that will make the program follow a certain path
36733 through the code. If you do not send us the example, we will not be able
36734 to construct one, so we will not be able to verify that the bug is fixed.
36736 And if we cannot understand what bug you are trying to fix, or why your
36737 patch should be an improvement, we will not install it. A test case will
36738 help us to understand.
36741 A guess about what the bug is or what it depends on.
36743 Such guesses are usually wrong. Even we cannot guess right about such
36744 things without first using the debugger to find the facts.
36747 @c The readline documentation is distributed with the readline code
36748 @c and consists of the two following files:
36751 @c Use -I with makeinfo to point to the appropriate directory,
36752 @c environment var TEXINPUTS with TeX.
36753 @ifclear SYSTEM_READLINE
36754 @include rluser.texi
36755 @include hsuser.texi
36759 @appendix In Memoriam
36761 The @value{GDBN} project mourns the loss of the following long-time
36766 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36767 to Free Software in general. Outside of @value{GDBN}, he was known in
36768 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36770 @item Michael Snyder
36771 Michael was one of the Global Maintainers of the @value{GDBN} project,
36772 with contributions recorded as early as 1996, until 2011. In addition
36773 to his day to day participation, he was a large driving force behind
36774 adding Reverse Debugging to @value{GDBN}.
36777 Beyond their technical contributions to the project, they were also
36778 enjoyable members of the Free Software Community. We will miss them.
36780 @node Formatting Documentation
36781 @appendix Formatting Documentation
36783 @cindex @value{GDBN} reference card
36784 @cindex reference card
36785 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36786 for printing with PostScript or Ghostscript, in the @file{gdb}
36787 subdirectory of the main source directory@footnote{In
36788 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36789 release.}. If you can use PostScript or Ghostscript with your printer,
36790 you can print the reference card immediately with @file{refcard.ps}.
36792 The release also includes the source for the reference card. You
36793 can format it, using @TeX{}, by typing:
36799 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36800 mode on US ``letter'' size paper;
36801 that is, on a sheet 11 inches wide by 8.5 inches
36802 high. You will need to specify this form of printing as an option to
36803 your @sc{dvi} output program.
36805 @cindex documentation
36807 All the documentation for @value{GDBN} comes as part of the machine-readable
36808 distribution. The documentation is written in Texinfo format, which is
36809 a documentation system that uses a single source file to produce both
36810 on-line information and a printed manual. You can use one of the Info
36811 formatting commands to create the on-line version of the documentation
36812 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36814 @value{GDBN} includes an already formatted copy of the on-line Info
36815 version of this manual in the @file{gdb} subdirectory. The main Info
36816 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36817 subordinate files matching @samp{gdb.info*} in the same directory. If
36818 necessary, you can print out these files, or read them with any editor;
36819 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36820 Emacs or the standalone @code{info} program, available as part of the
36821 @sc{gnu} Texinfo distribution.
36823 If you want to format these Info files yourself, you need one of the
36824 Info formatting programs, such as @code{texinfo-format-buffer} or
36827 If you have @code{makeinfo} installed, and are in the top level
36828 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36829 version @value{GDBVN}), you can make the Info file by typing:
36836 If you want to typeset and print copies of this manual, you need @TeX{},
36837 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36838 Texinfo definitions file.
36840 @TeX{} is a typesetting program; it does not print files directly, but
36841 produces output files called @sc{dvi} files. To print a typeset
36842 document, you need a program to print @sc{dvi} files. If your system
36843 has @TeX{} installed, chances are it has such a program. The precise
36844 command to use depends on your system; @kbd{lpr -d} is common; another
36845 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36846 require a file name without any extension or a @samp{.dvi} extension.
36848 @TeX{} also requires a macro definitions file called
36849 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36850 written in Texinfo format. On its own, @TeX{} cannot either read or
36851 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36852 and is located in the @file{gdb-@var{version-number}/texinfo}
36855 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36856 typeset and print this manual. First switch to the @file{gdb}
36857 subdirectory of the main source directory (for example, to
36858 @file{gdb-@value{GDBVN}/gdb}) and type:
36864 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36866 @node Installing GDB
36867 @appendix Installing @value{GDBN}
36868 @cindex installation
36871 * Requirements:: Requirements for building @value{GDBN}
36872 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36873 * Separate Objdir:: Compiling @value{GDBN} in another directory
36874 * Config Names:: Specifying names for hosts and targets
36875 * Configure Options:: Summary of options for configure
36876 * System-wide configuration:: Having a system-wide init file
36880 @section Requirements for Building @value{GDBN}
36881 @cindex building @value{GDBN}, requirements for
36883 Building @value{GDBN} requires various tools and packages to be available.
36884 Other packages will be used only if they are found.
36886 @heading Tools/Packages Necessary for Building @value{GDBN}
36888 @item ISO C90 compiler
36889 @value{GDBN} is written in ISO C90. It should be buildable with any
36890 working C90 compiler, e.g.@: GCC.
36894 @heading Tools/Packages Optional for Building @value{GDBN}
36898 @value{GDBN} can use the Expat XML parsing library. This library may be
36899 included with your operating system distribution; if it is not, you
36900 can get the latest version from @url{http://expat.sourceforge.net}.
36901 The @file{configure} script will search for this library in several
36902 standard locations; if it is installed in an unusual path, you can
36903 use the @option{--with-libexpat-prefix} option to specify its location.
36909 Remote protocol memory maps (@pxref{Memory Map Format})
36911 Target descriptions (@pxref{Target Descriptions})
36913 Remote shared library lists (@xref{Library List Format},
36914 or alternatively @pxref{Library List Format for SVR4 Targets})
36916 MS-Windows shared libraries (@pxref{Shared Libraries})
36918 Traceframe info (@pxref{Traceframe Info Format})
36920 Branch trace (@pxref{Branch Trace Format})
36924 @cindex compressed debug sections
36925 @value{GDBN} will use the @samp{zlib} library, if available, to read
36926 compressed debug sections. Some linkers, such as GNU gold, are capable
36927 of producing binaries with compressed debug sections. If @value{GDBN}
36928 is compiled with @samp{zlib}, it will be able to read the debug
36929 information in such binaries.
36931 The @samp{zlib} library is likely included with your operating system
36932 distribution; if it is not, you can get the latest version from
36933 @url{http://zlib.net}.
36936 @value{GDBN}'s features related to character sets (@pxref{Character
36937 Sets}) require a functioning @code{iconv} implementation. If you are
36938 on a GNU system, then this is provided by the GNU C Library. Some
36939 other systems also provide a working @code{iconv}.
36941 If @value{GDBN} is using the @code{iconv} program which is installed
36942 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36943 This is done with @option{--with-iconv-bin} which specifies the
36944 directory that contains the @code{iconv} program.
36946 On systems without @code{iconv}, you can install GNU Libiconv. If you
36947 have previously installed Libiconv, you can use the
36948 @option{--with-libiconv-prefix} option to configure.
36950 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36951 arrange to build Libiconv if a directory named @file{libiconv} appears
36952 in the top-most source directory. If Libiconv is built this way, and
36953 if the operating system does not provide a suitable @code{iconv}
36954 implementation, then the just-built library will automatically be used
36955 by @value{GDBN}. One easy way to set this up is to download GNU
36956 Libiconv, unpack it, and then rename the directory holding the
36957 Libiconv source code to @samp{libiconv}.
36960 @node Running Configure
36961 @section Invoking the @value{GDBN} @file{configure} Script
36962 @cindex configuring @value{GDBN}
36963 @value{GDBN} comes with a @file{configure} script that automates the process
36964 of preparing @value{GDBN} for installation; you can then use @code{make} to
36965 build the @code{gdb} program.
36967 @c irrelevant in info file; it's as current as the code it lives with.
36968 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36969 look at the @file{README} file in the sources; we may have improved the
36970 installation procedures since publishing this manual.}
36973 The @value{GDBN} distribution includes all the source code you need for
36974 @value{GDBN} in a single directory, whose name is usually composed by
36975 appending the version number to @samp{gdb}.
36977 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36978 @file{gdb-@value{GDBVN}} directory. That directory contains:
36981 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36982 script for configuring @value{GDBN} and all its supporting libraries
36984 @item gdb-@value{GDBVN}/gdb
36985 the source specific to @value{GDBN} itself
36987 @item gdb-@value{GDBVN}/bfd
36988 source for the Binary File Descriptor library
36990 @item gdb-@value{GDBVN}/include
36991 @sc{gnu} include files
36993 @item gdb-@value{GDBVN}/libiberty
36994 source for the @samp{-liberty} free software library
36996 @item gdb-@value{GDBVN}/opcodes
36997 source for the library of opcode tables and disassemblers
36999 @item gdb-@value{GDBVN}/readline
37000 source for the @sc{gnu} command-line interface
37002 @item gdb-@value{GDBVN}/glob
37003 source for the @sc{gnu} filename pattern-matching subroutine
37005 @item gdb-@value{GDBVN}/mmalloc
37006 source for the @sc{gnu} memory-mapped malloc package
37009 The simplest way to configure and build @value{GDBN} is to run @file{configure}
37010 from the @file{gdb-@var{version-number}} source directory, which in
37011 this example is the @file{gdb-@value{GDBVN}} directory.
37013 First switch to the @file{gdb-@var{version-number}} source directory
37014 if you are not already in it; then run @file{configure}. Pass the
37015 identifier for the platform on which @value{GDBN} will run as an
37021 cd gdb-@value{GDBVN}
37022 ./configure @var{host}
37027 where @var{host} is an identifier such as @samp{sun4} or
37028 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
37029 (You can often leave off @var{host}; @file{configure} tries to guess the
37030 correct value by examining your system.)
37032 Running @samp{configure @var{host}} and then running @code{make} builds the
37033 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
37034 libraries, then @code{gdb} itself. The configured source files, and the
37035 binaries, are left in the corresponding source directories.
37038 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
37039 system does not recognize this automatically when you run a different
37040 shell, you may need to run @code{sh} on it explicitly:
37043 sh configure @var{host}
37046 If you run @file{configure} from a directory that contains source
37047 directories for multiple libraries or programs, such as the
37048 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
37050 creates configuration files for every directory level underneath (unless
37051 you tell it not to, with the @samp{--norecursion} option).
37053 You should run the @file{configure} script from the top directory in the
37054 source tree, the @file{gdb-@var{version-number}} directory. If you run
37055 @file{configure} from one of the subdirectories, you will configure only
37056 that subdirectory. That is usually not what you want. In particular,
37057 if you run the first @file{configure} from the @file{gdb} subdirectory
37058 of the @file{gdb-@var{version-number}} directory, you will omit the
37059 configuration of @file{bfd}, @file{readline}, and other sibling
37060 directories of the @file{gdb} subdirectory. This leads to build errors
37061 about missing include files such as @file{bfd/bfd.h}.
37063 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
37064 However, you should make sure that the shell on your path (named by
37065 the @samp{SHELL} environment variable) is publicly readable. Remember
37066 that @value{GDBN} uses the shell to start your program---some systems refuse to
37067 let @value{GDBN} debug child processes whose programs are not readable.
37069 @node Separate Objdir
37070 @section Compiling @value{GDBN} in Another Directory
37072 If you want to run @value{GDBN} versions for several host or target machines,
37073 you need a different @code{gdb} compiled for each combination of
37074 host and target. @file{configure} is designed to make this easy by
37075 allowing you to generate each configuration in a separate subdirectory,
37076 rather than in the source directory. If your @code{make} program
37077 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
37078 @code{make} in each of these directories builds the @code{gdb}
37079 program specified there.
37081 To build @code{gdb} in a separate directory, run @file{configure}
37082 with the @samp{--srcdir} option to specify where to find the source.
37083 (You also need to specify a path to find @file{configure}
37084 itself from your working directory. If the path to @file{configure}
37085 would be the same as the argument to @samp{--srcdir}, you can leave out
37086 the @samp{--srcdir} option; it is assumed.)
37088 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
37089 separate directory for a Sun 4 like this:
37093 cd gdb-@value{GDBVN}
37096 ../gdb-@value{GDBVN}/configure sun4
37101 When @file{configure} builds a configuration using a remote source
37102 directory, it creates a tree for the binaries with the same structure
37103 (and using the same names) as the tree under the source directory. In
37104 the example, you'd find the Sun 4 library @file{libiberty.a} in the
37105 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
37106 @file{gdb-sun4/gdb}.
37108 Make sure that your path to the @file{configure} script has just one
37109 instance of @file{gdb} in it. If your path to @file{configure} looks
37110 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
37111 one subdirectory of @value{GDBN}, not the whole package. This leads to
37112 build errors about missing include files such as @file{bfd/bfd.h}.
37114 One popular reason to build several @value{GDBN} configurations in separate
37115 directories is to configure @value{GDBN} for cross-compiling (where
37116 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
37117 programs that run on another machine---the @dfn{target}).
37118 You specify a cross-debugging target by
37119 giving the @samp{--target=@var{target}} option to @file{configure}.
37121 When you run @code{make} to build a program or library, you must run
37122 it in a configured directory---whatever directory you were in when you
37123 called @file{configure} (or one of its subdirectories).
37125 The @code{Makefile} that @file{configure} generates in each source
37126 directory also runs recursively. If you type @code{make} in a source
37127 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
37128 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
37129 will build all the required libraries, and then build GDB.
37131 When you have multiple hosts or targets configured in separate
37132 directories, you can run @code{make} on them in parallel (for example,
37133 if they are NFS-mounted on each of the hosts); they will not interfere
37137 @section Specifying Names for Hosts and Targets
37139 The specifications used for hosts and targets in the @file{configure}
37140 script are based on a three-part naming scheme, but some short predefined
37141 aliases are also supported. The full naming scheme encodes three pieces
37142 of information in the following pattern:
37145 @var{architecture}-@var{vendor}-@var{os}
37148 For example, you can use the alias @code{sun4} as a @var{host} argument,
37149 or as the value for @var{target} in a @code{--target=@var{target}}
37150 option. The equivalent full name is @samp{sparc-sun-sunos4}.
37152 The @file{configure} script accompanying @value{GDBN} does not provide
37153 any query facility to list all supported host and target names or
37154 aliases. @file{configure} calls the Bourne shell script
37155 @code{config.sub} to map abbreviations to full names; you can read the
37156 script, if you wish, or you can use it to test your guesses on
37157 abbreviations---for example:
37160 % sh config.sub i386-linux
37162 % sh config.sub alpha-linux
37163 alpha-unknown-linux-gnu
37164 % sh config.sub hp9k700
37166 % sh config.sub sun4
37167 sparc-sun-sunos4.1.1
37168 % sh config.sub sun3
37169 m68k-sun-sunos4.1.1
37170 % sh config.sub i986v
37171 Invalid configuration `i986v': machine `i986v' not recognized
37175 @code{config.sub} is also distributed in the @value{GDBN} source
37176 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
37178 @node Configure Options
37179 @section @file{configure} Options
37181 Here is a summary of the @file{configure} options and arguments that
37182 are most often useful for building @value{GDBN}. @file{configure} also has
37183 several other options not listed here. @inforef{What Configure
37184 Does,,configure.info}, for a full explanation of @file{configure}.
37187 configure @r{[}--help@r{]}
37188 @r{[}--prefix=@var{dir}@r{]}
37189 @r{[}--exec-prefix=@var{dir}@r{]}
37190 @r{[}--srcdir=@var{dirname}@r{]}
37191 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
37192 @r{[}--target=@var{target}@r{]}
37197 You may introduce options with a single @samp{-} rather than
37198 @samp{--} if you prefer; but you may abbreviate option names if you use
37203 Display a quick summary of how to invoke @file{configure}.
37205 @item --prefix=@var{dir}
37206 Configure the source to install programs and files under directory
37209 @item --exec-prefix=@var{dir}
37210 Configure the source to install programs under directory
37213 @c avoid splitting the warning from the explanation:
37215 @item --srcdir=@var{dirname}
37216 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
37217 @code{make} that implements the @code{VPATH} feature.}@*
37218 Use this option to make configurations in directories separate from the
37219 @value{GDBN} source directories. Among other things, you can use this to
37220 build (or maintain) several configurations simultaneously, in separate
37221 directories. @file{configure} writes configuration-specific files in
37222 the current directory, but arranges for them to use the source in the
37223 directory @var{dirname}. @file{configure} creates directories under
37224 the working directory in parallel to the source directories below
37227 @item --norecursion
37228 Configure only the directory level where @file{configure} is executed; do not
37229 propagate configuration to subdirectories.
37231 @item --target=@var{target}
37232 Configure @value{GDBN} for cross-debugging programs running on the specified
37233 @var{target}. Without this option, @value{GDBN} is configured to debug
37234 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
37236 There is no convenient way to generate a list of all available targets.
37238 @item @var{host} @dots{}
37239 Configure @value{GDBN} to run on the specified @var{host}.
37241 There is no convenient way to generate a list of all available hosts.
37244 There are many other options available as well, but they are generally
37245 needed for special purposes only.
37247 @node System-wide configuration
37248 @section System-wide configuration and settings
37249 @cindex system-wide init file
37251 @value{GDBN} can be configured to have a system-wide init file;
37252 this file will be read and executed at startup (@pxref{Startup, , What
37253 @value{GDBN} does during startup}).
37255 Here is the corresponding configure option:
37258 @item --with-system-gdbinit=@var{file}
37259 Specify that the default location of the system-wide init file is
37263 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
37264 it may be subject to relocation. Two possible cases:
37268 If the default location of this init file contains @file{$prefix},
37269 it will be subject to relocation. Suppose that the configure options
37270 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
37271 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
37272 init file is looked for as @file{$install/etc/gdbinit} instead of
37273 @file{$prefix/etc/gdbinit}.
37276 By contrast, if the default location does not contain the prefix,
37277 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
37278 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
37279 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
37280 wherever @value{GDBN} is installed.
37283 If the configured location of the system-wide init file (as given by the
37284 @option{--with-system-gdbinit} option at configure time) is in the
37285 data-directory (as specified by @option{--with-gdb-datadir} at configure
37286 time) or in one of its subdirectories, then @value{GDBN} will look for the
37287 system-wide init file in the directory specified by the
37288 @option{--data-directory} command-line option.
37289 Note that the system-wide init file is only read once, during @value{GDBN}
37290 initialization. If the data-directory is changed after @value{GDBN} has
37291 started with the @code{set data-directory} command, the file will not be
37295 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
37298 @node System-wide Configuration Scripts
37299 @subsection Installed System-wide Configuration Scripts
37300 @cindex system-wide configuration scripts
37302 The @file{system-gdbinit} directory, located inside the data-directory
37303 (as specified by @option{--with-gdb-datadir} at configure time) contains
37304 a number of scripts which can be used as system-wide init files. To
37305 automatically source those scripts at startup, @value{GDBN} should be
37306 configured with @option{--with-system-gdbinit}. Otherwise, any user
37307 should be able to source them by hand as needed.
37309 The following scripts are currently available:
37312 @item @file{elinos.py}
37314 @cindex ELinOS system-wide configuration script
37315 This script is useful when debugging a program on an ELinOS target.
37316 It takes advantage of the environment variables defined in a standard
37317 ELinOS environment in order to determine the location of the system
37318 shared libraries, and then sets the @samp{solib-absolute-prefix}
37319 and @samp{solib-search-path} variables appropriately.
37321 @item @file{wrs-linux.py}
37322 @pindex wrs-linux.py
37323 @cindex Wind River Linux system-wide configuration script
37324 This script is useful when debugging a program on a target running
37325 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
37326 the host-side sysroot used by the target system.
37330 @node Maintenance Commands
37331 @appendix Maintenance Commands
37332 @cindex maintenance commands
37333 @cindex internal commands
37335 In addition to commands intended for @value{GDBN} users, @value{GDBN}
37336 includes a number of commands intended for @value{GDBN} developers,
37337 that are not documented elsewhere in this manual. These commands are
37338 provided here for reference. (For commands that turn on debugging
37339 messages, see @ref{Debugging Output}.)
37342 @kindex maint agent
37343 @kindex maint agent-eval
37344 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37345 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
37346 Translate the given @var{expression} into remote agent bytecodes.
37347 This command is useful for debugging the Agent Expression mechanism
37348 (@pxref{Agent Expressions}). The @samp{agent} version produces an
37349 expression useful for data collection, such as by tracepoints, while
37350 @samp{maint agent-eval} produces an expression that evaluates directly
37351 to a result. For instance, a collection expression for @code{globa +
37352 globb} will include bytecodes to record four bytes of memory at each
37353 of the addresses of @code{globa} and @code{globb}, while discarding
37354 the result of the addition, while an evaluation expression will do the
37355 addition and return the sum.
37356 If @code{-at} is given, generate remote agent bytecode for @var{location}.
37357 If not, generate remote agent bytecode for current frame PC address.
37359 @kindex maint agent-printf
37360 @item maint agent-printf @var{format},@var{expr},...
37361 Translate the given format string and list of argument expressions
37362 into remote agent bytecodes and display them as a disassembled list.
37363 This command is useful for debugging the agent version of dynamic
37364 printf (@pxref{Dynamic Printf}).
37366 @kindex maint info breakpoints
37367 @item @anchor{maint info breakpoints}maint info breakpoints
37368 Using the same format as @samp{info breakpoints}, display both the
37369 breakpoints you've set explicitly, and those @value{GDBN} is using for
37370 internal purposes. Internal breakpoints are shown with negative
37371 breakpoint numbers. The type column identifies what kind of breakpoint
37376 Normal, explicitly set breakpoint.
37379 Normal, explicitly set watchpoint.
37382 Internal breakpoint, used to handle correctly stepping through
37383 @code{longjmp} calls.
37385 @item longjmp resume
37386 Internal breakpoint at the target of a @code{longjmp}.
37389 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
37392 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
37395 Shared library events.
37399 @kindex maint info bfds
37400 @item maint info bfds
37401 This prints information about each @code{bfd} object that is known to
37402 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
37404 @kindex set displaced-stepping
37405 @kindex show displaced-stepping
37406 @cindex displaced stepping support
37407 @cindex out-of-line single-stepping
37408 @item set displaced-stepping
37409 @itemx show displaced-stepping
37410 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
37411 if the target supports it. Displaced stepping is a way to single-step
37412 over breakpoints without removing them from the inferior, by executing
37413 an out-of-line copy of the instruction that was originally at the
37414 breakpoint location. It is also known as out-of-line single-stepping.
37417 @item set displaced-stepping on
37418 If the target architecture supports it, @value{GDBN} will use
37419 displaced stepping to step over breakpoints.
37421 @item set displaced-stepping off
37422 @value{GDBN} will not use displaced stepping to step over breakpoints,
37423 even if such is supported by the target architecture.
37425 @cindex non-stop mode, and @samp{set displaced-stepping}
37426 @item set displaced-stepping auto
37427 This is the default mode. @value{GDBN} will use displaced stepping
37428 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
37429 architecture supports displaced stepping.
37432 @kindex maint check-psymtabs
37433 @item maint check-psymtabs
37434 Check the consistency of currently expanded psymtabs versus symtabs.
37435 Use this to check, for example, whether a symbol is in one but not the other.
37437 @kindex maint check-symtabs
37438 @item maint check-symtabs
37439 Check the consistency of currently expanded symtabs.
37441 @kindex maint expand-symtabs
37442 @item maint expand-symtabs [@var{regexp}]
37443 Expand symbol tables.
37444 If @var{regexp} is specified, only expand symbol tables for file
37445 names matching @var{regexp}.
37447 @kindex maint cplus first_component
37448 @item maint cplus first_component @var{name}
37449 Print the first C@t{++} class/namespace component of @var{name}.
37451 @kindex maint cplus namespace
37452 @item maint cplus namespace
37453 Print the list of possible C@t{++} namespaces.
37455 @kindex maint demangle
37456 @item maint demangle @var{name}
37457 Demangle a C@t{++} or Objective-C mangled @var{name}.
37459 @kindex maint deprecate
37460 @kindex maint undeprecate
37461 @cindex deprecated commands
37462 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
37463 @itemx maint undeprecate @var{command}
37464 Deprecate or undeprecate the named @var{command}. Deprecated commands
37465 cause @value{GDBN} to issue a warning when you use them. The optional
37466 argument @var{replacement} says which newer command should be used in
37467 favor of the deprecated one; if it is given, @value{GDBN} will mention
37468 the replacement as part of the warning.
37470 @kindex maint dump-me
37471 @item maint dump-me
37472 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
37473 Cause a fatal signal in the debugger and force it to dump its core.
37474 This is supported only on systems which support aborting a program
37475 with the @code{SIGQUIT} signal.
37477 @kindex maint internal-error
37478 @kindex maint internal-warning
37479 @item maint internal-error @r{[}@var{message-text}@r{]}
37480 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
37481 Cause @value{GDBN} to call the internal function @code{internal_error}
37482 or @code{internal_warning} and hence behave as though an internal error
37483 or internal warning has been detected. In addition to reporting the
37484 internal problem, these functions give the user the opportunity to
37485 either quit @value{GDBN} or create a core file of the current
37486 @value{GDBN} session.
37488 These commands take an optional parameter @var{message-text} that is
37489 used as the text of the error or warning message.
37491 Here's an example of using @code{internal-error}:
37494 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
37495 @dots{}/maint.c:121: internal-error: testing, 1, 2
37496 A problem internal to GDB has been detected. Further
37497 debugging may prove unreliable.
37498 Quit this debugging session? (y or n) @kbd{n}
37499 Create a core file? (y or n) @kbd{n}
37503 @cindex @value{GDBN} internal error
37504 @cindex internal errors, control of @value{GDBN} behavior
37506 @kindex maint set internal-error
37507 @kindex maint show internal-error
37508 @kindex maint set internal-warning
37509 @kindex maint show internal-warning
37510 @item maint set internal-error @var{action} [ask|yes|no]
37511 @itemx maint show internal-error @var{action}
37512 @itemx maint set internal-warning @var{action} [ask|yes|no]
37513 @itemx maint show internal-warning @var{action}
37514 When @value{GDBN} reports an internal problem (error or warning) it
37515 gives the user the opportunity to both quit @value{GDBN} and create a
37516 core file of the current @value{GDBN} session. These commands let you
37517 override the default behaviour for each particular @var{action},
37518 described in the table below.
37522 You can specify that @value{GDBN} should always (yes) or never (no)
37523 quit. The default is to ask the user what to do.
37526 You can specify that @value{GDBN} should always (yes) or never (no)
37527 create a core file. The default is to ask the user what to do.
37530 @kindex maint packet
37531 @item maint packet @var{text}
37532 If @value{GDBN} is talking to an inferior via the serial protocol,
37533 then this command sends the string @var{text} to the inferior, and
37534 displays the response packet. @value{GDBN} supplies the initial
37535 @samp{$} character, the terminating @samp{#} character, and the
37538 @kindex maint print architecture
37539 @item maint print architecture @r{[}@var{file}@r{]}
37540 Print the entire architecture configuration. The optional argument
37541 @var{file} names the file where the output goes.
37543 @kindex maint print c-tdesc
37544 @item maint print c-tdesc
37545 Print the current target description (@pxref{Target Descriptions}) as
37546 a C source file. The created source file can be used in @value{GDBN}
37547 when an XML parser is not available to parse the description.
37549 @kindex maint print dummy-frames
37550 @item maint print dummy-frames
37551 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
37554 (@value{GDBP}) @kbd{b add}
37556 (@value{GDBP}) @kbd{print add(2,3)}
37557 Breakpoint 2, add (a=2, b=3) at @dots{}
37559 The program being debugged stopped while in a function called from GDB.
37561 (@value{GDBP}) @kbd{maint print dummy-frames}
37562 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
37563 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
37564 call_lo=0x01014000 call_hi=0x01014001
37568 Takes an optional file parameter.
37570 @kindex maint print registers
37571 @kindex maint print raw-registers
37572 @kindex maint print cooked-registers
37573 @kindex maint print register-groups
37574 @kindex maint print remote-registers
37575 @item maint print registers @r{[}@var{file}@r{]}
37576 @itemx maint print raw-registers @r{[}@var{file}@r{]}
37577 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
37578 @itemx maint print register-groups @r{[}@var{file}@r{]}
37579 @itemx maint print remote-registers @r{[}@var{file}@r{]}
37580 Print @value{GDBN}'s internal register data structures.
37582 The command @code{maint print raw-registers} includes the contents of
37583 the raw register cache; the command @code{maint print
37584 cooked-registers} includes the (cooked) value of all registers,
37585 including registers which aren't available on the target nor visible
37586 to user; the command @code{maint print register-groups} includes the
37587 groups that each register is a member of; and the command @code{maint
37588 print remote-registers} includes the remote target's register numbers
37589 and offsets in the `G' packets.
37591 These commands take an optional parameter, a file name to which to
37592 write the information.
37594 @kindex maint print reggroups
37595 @item maint print reggroups @r{[}@var{file}@r{]}
37596 Print @value{GDBN}'s internal register group data structures. The
37597 optional argument @var{file} tells to what file to write the
37600 The register groups info looks like this:
37603 (@value{GDBP}) @kbd{maint print reggroups}
37616 This command forces @value{GDBN} to flush its internal register cache.
37618 @kindex maint print objfiles
37619 @cindex info for known object files
37620 @item maint print objfiles @r{[}@var{regexp}@r{]}
37621 Print a dump of all known object files.
37622 If @var{regexp} is specified, only print object files whose names
37623 match @var{regexp}. For each object file, this command prints its name,
37624 address in memory, and all of its psymtabs and symtabs.
37626 @kindex maint print section-scripts
37627 @cindex info for known .debug_gdb_scripts-loaded scripts
37628 @item maint print section-scripts [@var{regexp}]
37629 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
37630 If @var{regexp} is specified, only print scripts loaded by object files
37631 matching @var{regexp}.
37632 For each script, this command prints its name as specified in the objfile,
37633 and the full path if known.
37634 @xref{dotdebug_gdb_scripts section}.
37636 @kindex maint print statistics
37637 @cindex bcache statistics
37638 @item maint print statistics
37639 This command prints, for each object file in the program, various data
37640 about that object file followed by the byte cache (@dfn{bcache})
37641 statistics for the object file. The objfile data includes the number
37642 of minimal, partial, full, and stabs symbols, the number of types
37643 defined by the objfile, the number of as yet unexpanded psym tables,
37644 the number of line tables and string tables, and the amount of memory
37645 used by the various tables. The bcache statistics include the counts,
37646 sizes, and counts of duplicates of all and unique objects, max,
37647 average, and median entry size, total memory used and its overhead and
37648 savings, and various measures of the hash table size and chain
37651 @kindex maint print target-stack
37652 @cindex target stack description
37653 @item maint print target-stack
37654 A @dfn{target} is an interface between the debugger and a particular
37655 kind of file or process. Targets can be stacked in @dfn{strata},
37656 so that more than one target can potentially respond to a request.
37657 In particular, memory accesses will walk down the stack of targets
37658 until they find a target that is interested in handling that particular
37661 This command prints a short description of each layer that was pushed on
37662 the @dfn{target stack}, starting from the top layer down to the bottom one.
37664 @kindex maint print type
37665 @cindex type chain of a data type
37666 @item maint print type @var{expr}
37667 Print the type chain for a type specified by @var{expr}. The argument
37668 can be either a type name or a symbol. If it is a symbol, the type of
37669 that symbol is described. The type chain produced by this command is
37670 a recursive definition of the data type as stored in @value{GDBN}'s
37671 data structures, including its flags and contained types.
37673 @kindex maint set dwarf2 always-disassemble
37674 @kindex maint show dwarf2 always-disassemble
37675 @item maint set dwarf2 always-disassemble
37676 @item maint show dwarf2 always-disassemble
37677 Control the behavior of @code{info address} when using DWARF debugging
37680 The default is @code{off}, which means that @value{GDBN} should try to
37681 describe a variable's location in an easily readable format. When
37682 @code{on}, @value{GDBN} will instead display the DWARF location
37683 expression in an assembly-like format. Note that some locations are
37684 too complex for @value{GDBN} to describe simply; in this case you will
37685 always see the disassembly form.
37687 Here is an example of the resulting disassembly:
37690 (gdb) info addr argc
37691 Symbol "argc" is a complex DWARF expression:
37695 For more information on these expressions, see
37696 @uref{http://www.dwarfstd.org/, the DWARF standard}.
37698 @kindex maint set dwarf2 max-cache-age
37699 @kindex maint show dwarf2 max-cache-age
37700 @item maint set dwarf2 max-cache-age
37701 @itemx maint show dwarf2 max-cache-age
37702 Control the DWARF 2 compilation unit cache.
37704 @cindex DWARF 2 compilation units cache
37705 In object files with inter-compilation-unit references, such as those
37706 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
37707 reader needs to frequently refer to previously read compilation units.
37708 This setting controls how long a compilation unit will remain in the
37709 cache if it is not referenced. A higher limit means that cached
37710 compilation units will be stored in memory longer, and more total
37711 memory will be used. Setting it to zero disables caching, which will
37712 slow down @value{GDBN} startup, but reduce memory consumption.
37714 @kindex maint set profile
37715 @kindex maint show profile
37716 @cindex profiling GDB
37717 @item maint set profile
37718 @itemx maint show profile
37719 Control profiling of @value{GDBN}.
37721 Profiling will be disabled until you use the @samp{maint set profile}
37722 command to enable it. When you enable profiling, the system will begin
37723 collecting timing and execution count data; when you disable profiling or
37724 exit @value{GDBN}, the results will be written to a log file. Remember that
37725 if you use profiling, @value{GDBN} will overwrite the profiling log file
37726 (often called @file{gmon.out}). If you have a record of important profiling
37727 data in a @file{gmon.out} file, be sure to move it to a safe location.
37729 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37730 compiled with the @samp{-pg} compiler option.
37732 @kindex maint set show-debug-regs
37733 @kindex maint show show-debug-regs
37734 @cindex hardware debug registers
37735 @item maint set show-debug-regs
37736 @itemx maint show show-debug-regs
37737 Control whether to show variables that mirror the hardware debug
37738 registers. Use @code{on} to enable, @code{off} to disable. If
37739 enabled, the debug registers values are shown when @value{GDBN} inserts or
37740 removes a hardware breakpoint or watchpoint, and when the inferior
37741 triggers a hardware-assisted breakpoint or watchpoint.
37743 @kindex maint set show-all-tib
37744 @kindex maint show show-all-tib
37745 @item maint set show-all-tib
37746 @itemx maint show show-all-tib
37747 Control whether to show all non zero areas within a 1k block starting
37748 at thread local base, when using the @samp{info w32 thread-information-block}
37751 @kindex maint set per-command
37752 @kindex maint show per-command
37753 @item maint set per-command
37754 @itemx maint show per-command
37755 @cindex resources used by commands
37757 @value{GDBN} can display the resources used by each command.
37758 This is useful in debugging performance problems.
37761 @item maint set per-command space [on|off]
37762 @itemx maint show per-command space
37763 Enable or disable the printing of the memory used by GDB for each command.
37764 If enabled, @value{GDBN} will display how much memory each command
37765 took, following the command's own output.
37766 This can also be requested by invoking @value{GDBN} with the
37767 @option{--statistics} command-line switch (@pxref{Mode Options}).
37769 @item maint set per-command time [on|off]
37770 @itemx maint show per-command time
37771 Enable or disable the printing of the execution time of @value{GDBN}
37773 If enabled, @value{GDBN} will display how much time it
37774 took to execute each command, following the command's own output.
37775 Both CPU time and wallclock time are printed.
37776 Printing both is useful when trying to determine whether the cost is
37777 CPU or, e.g., disk/network latency.
37778 Note that the CPU time printed is for @value{GDBN} only, it does not include
37779 the execution time of the inferior because there's no mechanism currently
37780 to compute how much time was spent by @value{GDBN} and how much time was
37781 spent by the program been debugged.
37782 This can also be requested by invoking @value{GDBN} with the
37783 @option{--statistics} command-line switch (@pxref{Mode Options}).
37785 @item maint set per-command symtab [on|off]
37786 @itemx maint show per-command symtab
37787 Enable or disable the printing of basic symbol table statistics
37789 If enabled, @value{GDBN} will display the following information:
37793 number of symbol tables
37795 number of primary symbol tables
37797 number of blocks in the blockvector
37801 @kindex maint space
37802 @cindex memory used by commands
37803 @item maint space @var{value}
37804 An alias for @code{maint set per-command space}.
37805 A non-zero value enables it, zero disables it.
37808 @cindex time of command execution
37809 @item maint time @var{value}
37810 An alias for @code{maint set per-command time}.
37811 A non-zero value enables it, zero disables it.
37813 @kindex maint translate-address
37814 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37815 Find the symbol stored at the location specified by the address
37816 @var{addr} and an optional section name @var{section}. If found,
37817 @value{GDBN} prints the name of the closest symbol and an offset from
37818 the symbol's location to the specified address. This is similar to
37819 the @code{info address} command (@pxref{Symbols}), except that this
37820 command also allows to find symbols in other sections.
37822 If section was not specified, the section in which the symbol was found
37823 is also printed. For dynamically linked executables, the name of
37824 executable or shared library containing the symbol is printed as well.
37828 The following command is useful for non-interactive invocations of
37829 @value{GDBN}, such as in the test suite.
37832 @item set watchdog @var{nsec}
37833 @kindex set watchdog
37834 @cindex watchdog timer
37835 @cindex timeout for commands
37836 Set the maximum number of seconds @value{GDBN} will wait for the
37837 target operation to finish. If this time expires, @value{GDBN}
37838 reports and error and the command is aborted.
37840 @item show watchdog
37841 Show the current setting of the target wait timeout.
37844 @node Remote Protocol
37845 @appendix @value{GDBN} Remote Serial Protocol
37850 * Stop Reply Packets::
37851 * General Query Packets::
37852 * Architecture-Specific Protocol Details::
37853 * Tracepoint Packets::
37854 * Host I/O Packets::
37856 * Notification Packets::
37857 * Remote Non-Stop::
37858 * Packet Acknowledgment::
37860 * File-I/O Remote Protocol Extension::
37861 * Library List Format::
37862 * Library List Format for SVR4 Targets::
37863 * Memory Map Format::
37864 * Thread List Format::
37865 * Traceframe Info Format::
37866 * Branch Trace Format::
37872 There may be occasions when you need to know something about the
37873 protocol---for example, if there is only one serial port to your target
37874 machine, you might want your program to do something special if it
37875 recognizes a packet meant for @value{GDBN}.
37877 In the examples below, @samp{->} and @samp{<-} are used to indicate
37878 transmitted and received data, respectively.
37880 @cindex protocol, @value{GDBN} remote serial
37881 @cindex serial protocol, @value{GDBN} remote
37882 @cindex remote serial protocol
37883 All @value{GDBN} commands and responses (other than acknowledgments
37884 and notifications, see @ref{Notification Packets}) are sent as a
37885 @var{packet}. A @var{packet} is introduced with the character
37886 @samp{$}, the actual @var{packet-data}, and the terminating character
37887 @samp{#} followed by a two-digit @var{checksum}:
37890 @code{$}@var{packet-data}@code{#}@var{checksum}
37894 @cindex checksum, for @value{GDBN} remote
37896 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37897 characters between the leading @samp{$} and the trailing @samp{#} (an
37898 eight bit unsigned checksum).
37900 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37901 specification also included an optional two-digit @var{sequence-id}:
37904 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37907 @cindex sequence-id, for @value{GDBN} remote
37909 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37910 has never output @var{sequence-id}s. Stubs that handle packets added
37911 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37913 When either the host or the target machine receives a packet, the first
37914 response expected is an acknowledgment: either @samp{+} (to indicate
37915 the package was received correctly) or @samp{-} (to request
37919 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37924 The @samp{+}/@samp{-} acknowledgments can be disabled
37925 once a connection is established.
37926 @xref{Packet Acknowledgment}, for details.
37928 The host (@value{GDBN}) sends @var{command}s, and the target (the
37929 debugging stub incorporated in your program) sends a @var{response}. In
37930 the case of step and continue @var{command}s, the response is only sent
37931 when the operation has completed, and the target has again stopped all
37932 threads in all attached processes. This is the default all-stop mode
37933 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37934 execution mode; see @ref{Remote Non-Stop}, for details.
37936 @var{packet-data} consists of a sequence of characters with the
37937 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37940 @cindex remote protocol, field separator
37941 Fields within the packet should be separated using @samp{,} @samp{;} or
37942 @samp{:}. Except where otherwise noted all numbers are represented in
37943 @sc{hex} with leading zeros suppressed.
37945 Implementors should note that prior to @value{GDBN} 5.0, the character
37946 @samp{:} could not appear as the third character in a packet (as it
37947 would potentially conflict with the @var{sequence-id}).
37949 @cindex remote protocol, binary data
37950 @anchor{Binary Data}
37951 Binary data in most packets is encoded either as two hexadecimal
37952 digits per byte of binary data. This allowed the traditional remote
37953 protocol to work over connections which were only seven-bit clean.
37954 Some packets designed more recently assume an eight-bit clean
37955 connection, and use a more efficient encoding to send and receive
37958 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37959 as an escape character. Any escaped byte is transmitted as the escape
37960 character followed by the original character XORed with @code{0x20}.
37961 For example, the byte @code{0x7d} would be transmitted as the two
37962 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37963 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37964 @samp{@}}) must always be escaped. Responses sent by the stub
37965 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37966 is not interpreted as the start of a run-length encoded sequence
37969 Response @var{data} can be run-length encoded to save space.
37970 Run-length encoding replaces runs of identical characters with one
37971 instance of the repeated character, followed by a @samp{*} and a
37972 repeat count. The repeat count is itself sent encoded, to avoid
37973 binary characters in @var{data}: a value of @var{n} is sent as
37974 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37975 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37976 code 32) for a repeat count of 3. (This is because run-length
37977 encoding starts to win for counts 3 or more.) Thus, for example,
37978 @samp{0* } is a run-length encoding of ``0000'': the space character
37979 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37982 The printable characters @samp{#} and @samp{$} or with a numeric value
37983 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37984 seven repeats (@samp{$}) can be expanded using a repeat count of only
37985 five (@samp{"}). For example, @samp{00000000} can be encoded as
37988 The error response returned for some packets includes a two character
37989 error number. That number is not well defined.
37991 @cindex empty response, for unsupported packets
37992 For any @var{command} not supported by the stub, an empty response
37993 (@samp{$#00}) should be returned. That way it is possible to extend the
37994 protocol. A newer @value{GDBN} can tell if a packet is supported based
37997 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37998 commands for register access, and the @samp{m} and @samp{M} commands
37999 for memory access. Stubs that only control single-threaded targets
38000 can implement run control with the @samp{c} (continue), and @samp{s}
38001 (step) commands. Stubs that support multi-threading targets should
38002 support the @samp{vCont} command. All other commands are optional.
38007 The following table provides a complete list of all currently defined
38008 @var{command}s and their corresponding response @var{data}.
38009 @xref{File-I/O Remote Protocol Extension}, for details about the File
38010 I/O extension of the remote protocol.
38012 Each packet's description has a template showing the packet's overall
38013 syntax, followed by an explanation of the packet's meaning. We
38014 include spaces in some of the templates for clarity; these are not
38015 part of the packet's syntax. No @value{GDBN} packet uses spaces to
38016 separate its components. For example, a template like @samp{foo
38017 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
38018 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
38019 @var{baz}. @value{GDBN} does not transmit a space character between the
38020 @samp{foo} and the @var{bar}, or between the @var{bar} and the
38023 @cindex @var{thread-id}, in remote protocol
38024 @anchor{thread-id syntax}
38025 Several packets and replies include a @var{thread-id} field to identify
38026 a thread. Normally these are positive numbers with a target-specific
38027 interpretation, formatted as big-endian hex strings. A @var{thread-id}
38028 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
38031 In addition, the remote protocol supports a multiprocess feature in
38032 which the @var{thread-id} syntax is extended to optionally include both
38033 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
38034 The @var{pid} (process) and @var{tid} (thread) components each have the
38035 format described above: a positive number with target-specific
38036 interpretation formatted as a big-endian hex string, literal @samp{-1}
38037 to indicate all processes or threads (respectively), or @samp{0} to
38038 indicate an arbitrary process or thread. Specifying just a process, as
38039 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
38040 error to specify all processes but a specific thread, such as
38041 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
38042 for those packets and replies explicitly documented to include a process
38043 ID, rather than a @var{thread-id}.
38045 The multiprocess @var{thread-id} syntax extensions are only used if both
38046 @value{GDBN} and the stub report support for the @samp{multiprocess}
38047 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
38050 Note that all packet forms beginning with an upper- or lower-case
38051 letter, other than those described here, are reserved for future use.
38053 Here are the packet descriptions.
38058 @cindex @samp{!} packet
38059 @anchor{extended mode}
38060 Enable extended mode. In extended mode, the remote server is made
38061 persistent. The @samp{R} packet is used to restart the program being
38067 The remote target both supports and has enabled extended mode.
38071 @cindex @samp{?} packet
38072 Indicate the reason the target halted. The reply is the same as for
38073 step and continue. This packet has a special interpretation when the
38074 target is in non-stop mode; see @ref{Remote Non-Stop}.
38077 @xref{Stop Reply Packets}, for the reply specifications.
38079 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
38080 @cindex @samp{A} packet
38081 Initialized @code{argv[]} array passed into program. @var{arglen}
38082 specifies the number of bytes in the hex encoded byte stream
38083 @var{arg}. See @code{gdbserver} for more details.
38088 The arguments were set.
38094 @cindex @samp{b} packet
38095 (Don't use this packet; its behavior is not well-defined.)
38096 Change the serial line speed to @var{baud}.
38098 JTC: @emph{When does the transport layer state change? When it's
38099 received, or after the ACK is transmitted. In either case, there are
38100 problems if the command or the acknowledgment packet is dropped.}
38102 Stan: @emph{If people really wanted to add something like this, and get
38103 it working for the first time, they ought to modify ser-unix.c to send
38104 some kind of out-of-band message to a specially-setup stub and have the
38105 switch happen "in between" packets, so that from remote protocol's point
38106 of view, nothing actually happened.}
38108 @item B @var{addr},@var{mode}
38109 @cindex @samp{B} packet
38110 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
38111 breakpoint at @var{addr}.
38113 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
38114 (@pxref{insert breakpoint or watchpoint packet}).
38116 @cindex @samp{bc} packet
38119 Backward continue. Execute the target system in reverse. No parameter.
38120 @xref{Reverse Execution}, for more information.
38123 @xref{Stop Reply Packets}, for the reply specifications.
38125 @cindex @samp{bs} packet
38128 Backward single step. Execute one instruction in reverse. No parameter.
38129 @xref{Reverse Execution}, for more information.
38132 @xref{Stop Reply Packets}, for the reply specifications.
38134 @item c @r{[}@var{addr}@r{]}
38135 @cindex @samp{c} packet
38136 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
38137 resume at current address.
38139 This packet is deprecated for multi-threading support. @xref{vCont
38143 @xref{Stop Reply Packets}, for the reply specifications.
38145 @item C @var{sig}@r{[};@var{addr}@r{]}
38146 @cindex @samp{C} packet
38147 Continue with signal @var{sig} (hex signal number). If
38148 @samp{;@var{addr}} is omitted, resume at same address.
38150 This packet is deprecated for multi-threading support. @xref{vCont
38154 @xref{Stop Reply Packets}, for the reply specifications.
38157 @cindex @samp{d} packet
38160 Don't use this packet; instead, define a general set packet
38161 (@pxref{General Query Packets}).
38165 @cindex @samp{D} packet
38166 The first form of the packet is used to detach @value{GDBN} from the
38167 remote system. It is sent to the remote target
38168 before @value{GDBN} disconnects via the @code{detach} command.
38170 The second form, including a process ID, is used when multiprocess
38171 protocol extensions are enabled (@pxref{multiprocess extensions}), to
38172 detach only a specific process. The @var{pid} is specified as a
38173 big-endian hex string.
38183 @item F @var{RC},@var{EE},@var{CF};@var{XX}
38184 @cindex @samp{F} packet
38185 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
38186 This is part of the File-I/O protocol extension. @xref{File-I/O
38187 Remote Protocol Extension}, for the specification.
38190 @anchor{read registers packet}
38191 @cindex @samp{g} packet
38192 Read general registers.
38196 @item @var{XX@dots{}}
38197 Each byte of register data is described by two hex digits. The bytes
38198 with the register are transmitted in target byte order. The size of
38199 each register and their position within the @samp{g} packet are
38200 determined by the @value{GDBN} internal gdbarch functions
38201 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
38202 specification of several standard @samp{g} packets is specified below.
38204 When reading registers from a trace frame (@pxref{Analyze Collected
38205 Data,,Using the Collected Data}), the stub may also return a string of
38206 literal @samp{x}'s in place of the register data digits, to indicate
38207 that the corresponding register has not been collected, thus its value
38208 is unavailable. For example, for an architecture with 4 registers of
38209 4 bytes each, the following reply indicates to @value{GDBN} that
38210 registers 0 and 2 have not been collected, while registers 1 and 3
38211 have been collected, and both have zero value:
38215 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
38222 @item G @var{XX@dots{}}
38223 @cindex @samp{G} packet
38224 Write general registers. @xref{read registers packet}, for a
38225 description of the @var{XX@dots{}} data.
38235 @item H @var{op} @var{thread-id}
38236 @cindex @samp{H} packet
38237 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
38238 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
38239 it should be @samp{c} for step and continue operations (note that this
38240 is deprecated, supporting the @samp{vCont} command is a better
38241 option), @samp{g} for other operations. The thread designator
38242 @var{thread-id} has the format and interpretation described in
38243 @ref{thread-id syntax}.
38254 @c 'H': How restrictive (or permissive) is the thread model. If a
38255 @c thread is selected and stopped, are other threads allowed
38256 @c to continue to execute? As I mentioned above, I think the
38257 @c semantics of each command when a thread is selected must be
38258 @c described. For example:
38260 @c 'g': If the stub supports threads and a specific thread is
38261 @c selected, returns the register block from that thread;
38262 @c otherwise returns current registers.
38264 @c 'G' If the stub supports threads and a specific thread is
38265 @c selected, sets the registers of the register block of
38266 @c that thread; otherwise sets current registers.
38268 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
38269 @anchor{cycle step packet}
38270 @cindex @samp{i} packet
38271 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
38272 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
38273 step starting at that address.
38276 @cindex @samp{I} packet
38277 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
38281 @cindex @samp{k} packet
38284 FIXME: @emph{There is no description of how to operate when a specific
38285 thread context has been selected (i.e.@: does 'k' kill only that
38288 @item m @var{addr},@var{length}
38289 @cindex @samp{m} packet
38290 Read @var{length} bytes of memory starting at address @var{addr}.
38291 Note that @var{addr} may not be aligned to any particular boundary.
38293 The stub need not use any particular size or alignment when gathering
38294 data from memory for the response; even if @var{addr} is word-aligned
38295 and @var{length} is a multiple of the word size, the stub is free to
38296 use byte accesses, or not. For this reason, this packet may not be
38297 suitable for accessing memory-mapped I/O devices.
38298 @cindex alignment of remote memory accesses
38299 @cindex size of remote memory accesses
38300 @cindex memory, alignment and size of remote accesses
38304 @item @var{XX@dots{}}
38305 Memory contents; each byte is transmitted as a two-digit hexadecimal
38306 number. The reply may contain fewer bytes than requested if the
38307 server was able to read only part of the region of memory.
38312 @item M @var{addr},@var{length}:@var{XX@dots{}}
38313 @cindex @samp{M} packet
38314 Write @var{length} bytes of memory starting at address @var{addr}.
38315 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
38316 hexadecimal number.
38323 for an error (this includes the case where only part of the data was
38328 @cindex @samp{p} packet
38329 Read the value of register @var{n}; @var{n} is in hex.
38330 @xref{read registers packet}, for a description of how the returned
38331 register value is encoded.
38335 @item @var{XX@dots{}}
38336 the register's value
38340 Indicating an unrecognized @var{query}.
38343 @item P @var{n@dots{}}=@var{r@dots{}}
38344 @anchor{write register packet}
38345 @cindex @samp{P} packet
38346 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
38347 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
38348 digits for each byte in the register (target byte order).
38358 @item q @var{name} @var{params}@dots{}
38359 @itemx Q @var{name} @var{params}@dots{}
38360 @cindex @samp{q} packet
38361 @cindex @samp{Q} packet
38362 General query (@samp{q}) and set (@samp{Q}). These packets are
38363 described fully in @ref{General Query Packets}.
38366 @cindex @samp{r} packet
38367 Reset the entire system.
38369 Don't use this packet; use the @samp{R} packet instead.
38372 @cindex @samp{R} packet
38373 Restart the program being debugged. @var{XX}, while needed, is ignored.
38374 This packet is only available in extended mode (@pxref{extended mode}).
38376 The @samp{R} packet has no reply.
38378 @item s @r{[}@var{addr}@r{]}
38379 @cindex @samp{s} packet
38380 Single step. @var{addr} is the address at which to resume. If
38381 @var{addr} is omitted, resume at same address.
38383 This packet is deprecated for multi-threading support. @xref{vCont
38387 @xref{Stop Reply Packets}, for the reply specifications.
38389 @item S @var{sig}@r{[};@var{addr}@r{]}
38390 @anchor{step with signal packet}
38391 @cindex @samp{S} packet
38392 Step with signal. This is analogous to the @samp{C} packet, but
38393 requests a single-step, rather than a normal resumption of execution.
38395 This packet is deprecated for multi-threading support. @xref{vCont
38399 @xref{Stop Reply Packets}, for the reply specifications.
38401 @item t @var{addr}:@var{PP},@var{MM}
38402 @cindex @samp{t} packet
38403 Search backwards starting at address @var{addr} for a match with pattern
38404 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
38405 @var{addr} must be at least 3 digits.
38407 @item T @var{thread-id}
38408 @cindex @samp{T} packet
38409 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
38414 thread is still alive
38420 Packets starting with @samp{v} are identified by a multi-letter name,
38421 up to the first @samp{;} or @samp{?} (or the end of the packet).
38423 @item vAttach;@var{pid}
38424 @cindex @samp{vAttach} packet
38425 Attach to a new process with the specified process ID @var{pid}.
38426 The process ID is a
38427 hexadecimal integer identifying the process. In all-stop mode, all
38428 threads in the attached process are stopped; in non-stop mode, it may be
38429 attached without being stopped if that is supported by the target.
38431 @c In non-stop mode, on a successful vAttach, the stub should set the
38432 @c current thread to a thread of the newly-attached process. After
38433 @c attaching, GDB queries for the attached process's thread ID with qC.
38434 @c Also note that, from a user perspective, whether or not the
38435 @c target is stopped on attach in non-stop mode depends on whether you
38436 @c use the foreground or background version of the attach command, not
38437 @c on what vAttach does; GDB does the right thing with respect to either
38438 @c stopping or restarting threads.
38440 This packet is only available in extended mode (@pxref{extended mode}).
38446 @item @r{Any stop packet}
38447 for success in all-stop mode (@pxref{Stop Reply Packets})
38449 for success in non-stop mode (@pxref{Remote Non-Stop})
38452 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
38453 @cindex @samp{vCont} packet
38454 @anchor{vCont packet}
38455 Resume the inferior, specifying different actions for each thread.
38456 If an action is specified with no @var{thread-id}, then it is applied to any
38457 threads that don't have a specific action specified; if no default action is
38458 specified then other threads should remain stopped in all-stop mode and
38459 in their current state in non-stop mode.
38460 Specifying multiple
38461 default actions is an error; specifying no actions is also an error.
38462 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
38464 Currently supported actions are:
38470 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
38474 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
38477 @item r @var{start},@var{end}
38478 Step once, and then keep stepping as long as the thread stops at
38479 addresses between @var{start} (inclusive) and @var{end} (exclusive).
38480 The remote stub reports a stop reply when either the thread goes out
38481 of the range or is stopped due to an unrelated reason, such as hitting
38482 a breakpoint. @xref{range stepping}.
38484 If the range is empty (@var{start} == @var{end}), then the action
38485 becomes equivalent to the @samp{s} action. In other words,
38486 single-step once, and report the stop (even if the stepped instruction
38487 jumps to @var{start}).
38489 (A stop reply may be sent at any point even if the PC is still within
38490 the stepping range; for example, it is valid to implement this packet
38491 in a degenerate way as a single instruction step operation.)
38495 The optional argument @var{addr} normally associated with the
38496 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
38497 not supported in @samp{vCont}.
38499 The @samp{t} action is only relevant in non-stop mode
38500 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
38501 A stop reply should be generated for any affected thread not already stopped.
38502 When a thread is stopped by means of a @samp{t} action,
38503 the corresponding stop reply should indicate that the thread has stopped with
38504 signal @samp{0}, regardless of whether the target uses some other signal
38505 as an implementation detail.
38507 The stub must support @samp{vCont} if it reports support for
38508 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
38509 this case @samp{vCont} actions can be specified to apply to all threads
38510 in a process by using the @samp{p@var{pid}.-1} form of the
38514 @xref{Stop Reply Packets}, for the reply specifications.
38517 @cindex @samp{vCont?} packet
38518 Request a list of actions supported by the @samp{vCont} packet.
38522 @item vCont@r{[};@var{action}@dots{}@r{]}
38523 The @samp{vCont} packet is supported. Each @var{action} is a supported
38524 command in the @samp{vCont} packet.
38526 The @samp{vCont} packet is not supported.
38529 @item vFile:@var{operation}:@var{parameter}@dots{}
38530 @cindex @samp{vFile} packet
38531 Perform a file operation on the target system. For details,
38532 see @ref{Host I/O Packets}.
38534 @item vFlashErase:@var{addr},@var{length}
38535 @cindex @samp{vFlashErase} packet
38536 Direct the stub to erase @var{length} bytes of flash starting at
38537 @var{addr}. The region may enclose any number of flash blocks, but
38538 its start and end must fall on block boundaries, as indicated by the
38539 flash block size appearing in the memory map (@pxref{Memory Map
38540 Format}). @value{GDBN} groups flash memory programming operations
38541 together, and sends a @samp{vFlashDone} request after each group; the
38542 stub is allowed to delay erase operation until the @samp{vFlashDone}
38543 packet is received.
38553 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
38554 @cindex @samp{vFlashWrite} packet
38555 Direct the stub to write data to flash address @var{addr}. The data
38556 is passed in binary form using the same encoding as for the @samp{X}
38557 packet (@pxref{Binary Data}). The memory ranges specified by
38558 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
38559 not overlap, and must appear in order of increasing addresses
38560 (although @samp{vFlashErase} packets for higher addresses may already
38561 have been received; the ordering is guaranteed only between
38562 @samp{vFlashWrite} packets). If a packet writes to an address that was
38563 neither erased by a preceding @samp{vFlashErase} packet nor by some other
38564 target-specific method, the results are unpredictable.
38572 for vFlashWrite addressing non-flash memory
38578 @cindex @samp{vFlashDone} packet
38579 Indicate to the stub that flash programming operation is finished.
38580 The stub is permitted to delay or batch the effects of a group of
38581 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
38582 @samp{vFlashDone} packet is received. The contents of the affected
38583 regions of flash memory are unpredictable until the @samp{vFlashDone}
38584 request is completed.
38586 @item vKill;@var{pid}
38587 @cindex @samp{vKill} packet
38588 Kill the process with the specified process ID. @var{pid} is a
38589 hexadecimal integer identifying the process. This packet is used in
38590 preference to @samp{k} when multiprocess protocol extensions are
38591 supported; see @ref{multiprocess extensions}.
38601 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
38602 @cindex @samp{vRun} packet
38603 Run the program @var{filename}, passing it each @var{argument} on its
38604 command line. The file and arguments are hex-encoded strings. If
38605 @var{filename} is an empty string, the stub may use a default program
38606 (e.g.@: the last program run). The program is created in the stopped
38609 @c FIXME: What about non-stop mode?
38611 This packet is only available in extended mode (@pxref{extended mode}).
38617 @item @r{Any stop packet}
38618 for success (@pxref{Stop Reply Packets})
38622 @cindex @samp{vStopped} packet
38623 @xref{Notification Packets}.
38625 @item X @var{addr},@var{length}:@var{XX@dots{}}
38627 @cindex @samp{X} packet
38628 Write data to memory, where the data is transmitted in binary.
38629 @var{addr} is address, @var{length} is number of bytes,
38630 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
38640 @item z @var{type},@var{addr},@var{kind}
38641 @itemx Z @var{type},@var{addr},@var{kind}
38642 @anchor{insert breakpoint or watchpoint packet}
38643 @cindex @samp{z} packet
38644 @cindex @samp{Z} packets
38645 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
38646 watchpoint starting at address @var{address} of kind @var{kind}.
38648 Each breakpoint and watchpoint packet @var{type} is documented
38651 @emph{Implementation notes: A remote target shall return an empty string
38652 for an unrecognized breakpoint or watchpoint packet @var{type}. A
38653 remote target shall support either both or neither of a given
38654 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
38655 avoid potential problems with duplicate packets, the operations should
38656 be implemented in an idempotent way.}
38658 @item z0,@var{addr},@var{kind}
38659 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
38660 @cindex @samp{z0} packet
38661 @cindex @samp{Z0} packet
38662 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
38663 @var{addr} of type @var{kind}.
38665 A memory breakpoint is implemented by replacing the instruction at
38666 @var{addr} with a software breakpoint or trap instruction. The
38667 @var{kind} is target-specific and typically indicates the size of
38668 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
38669 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
38670 architectures have additional meanings for @var{kind};
38671 @var{cond_list} is an optional list of conditional expressions in bytecode
38672 form that should be evaluated on the target's side. These are the
38673 conditions that should be taken into consideration when deciding if
38674 the breakpoint trigger should be reported back to @var{GDBN}.
38676 The @var{cond_list} parameter is comprised of a series of expressions,
38677 concatenated without separators. Each expression has the following form:
38681 @item X @var{len},@var{expr}
38682 @var{len} is the length of the bytecode expression and @var{expr} is the
38683 actual conditional expression in bytecode form.
38687 The optional @var{cmd_list} parameter introduces commands that may be
38688 run on the target, rather than being reported back to @value{GDBN}.
38689 The parameter starts with a numeric flag @var{persist}; if the flag is
38690 nonzero, then the breakpoint may remain active and the commands
38691 continue to be run even when @value{GDBN} disconnects from the target.
38692 Following this flag is a series of expressions concatenated with no
38693 separators. Each expression has the following form:
38697 @item X @var{len},@var{expr}
38698 @var{len} is the length of the bytecode expression and @var{expr} is the
38699 actual conditional expression in bytecode form.
38703 see @ref{Architecture-Specific Protocol Details}.
38705 @emph{Implementation note: It is possible for a target to copy or move
38706 code that contains memory breakpoints (e.g., when implementing
38707 overlays). The behavior of this packet, in the presence of such a
38708 target, is not defined.}
38720 @item z1,@var{addr},@var{kind}
38721 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38722 @cindex @samp{z1} packet
38723 @cindex @samp{Z1} packet
38724 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38725 address @var{addr}.
38727 A hardware breakpoint is implemented using a mechanism that is not
38728 dependant on being able to modify the target's memory. @var{kind}
38729 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38731 @emph{Implementation note: A hardware breakpoint is not affected by code
38744 @item z2,@var{addr},@var{kind}
38745 @itemx Z2,@var{addr},@var{kind}
38746 @cindex @samp{z2} packet
38747 @cindex @samp{Z2} packet
38748 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38749 @var{kind} is interpreted as the number of bytes to watch.
38761 @item z3,@var{addr},@var{kind}
38762 @itemx Z3,@var{addr},@var{kind}
38763 @cindex @samp{z3} packet
38764 @cindex @samp{Z3} packet
38765 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38766 @var{kind} is interpreted as the number of bytes to watch.
38778 @item z4,@var{addr},@var{kind}
38779 @itemx Z4,@var{addr},@var{kind}
38780 @cindex @samp{z4} packet
38781 @cindex @samp{Z4} packet
38782 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38783 @var{kind} is interpreted as the number of bytes to watch.
38797 @node Stop Reply Packets
38798 @section Stop Reply Packets
38799 @cindex stop reply packets
38801 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38802 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38803 receive any of the below as a reply. Except for @samp{?}
38804 and @samp{vStopped}, that reply is only returned
38805 when the target halts. In the below the exact meaning of @dfn{signal
38806 number} is defined by the header @file{include/gdb/signals.h} in the
38807 @value{GDBN} source code.
38809 As in the description of request packets, we include spaces in the
38810 reply templates for clarity; these are not part of the reply packet's
38811 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38817 The program received signal number @var{AA} (a two-digit hexadecimal
38818 number). This is equivalent to a @samp{T} response with no
38819 @var{n}:@var{r} pairs.
38821 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38822 @cindex @samp{T} packet reply
38823 The program received signal number @var{AA} (a two-digit hexadecimal
38824 number). This is equivalent to an @samp{S} response, except that the
38825 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38826 and other information directly in the stop reply packet, reducing
38827 round-trip latency. Single-step and breakpoint traps are reported
38828 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38832 If @var{n} is a hexadecimal number, it is a register number, and the
38833 corresponding @var{r} gives that register's value. @var{r} is a
38834 series of bytes in target byte order, with each byte given by a
38835 two-digit hex number.
38838 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38839 the stopped thread, as specified in @ref{thread-id syntax}.
38842 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38843 the core on which the stop event was detected.
38846 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38847 specific event that stopped the target. The currently defined stop
38848 reasons are listed below. @var{aa} should be @samp{05}, the trap
38849 signal. At most one stop reason should be present.
38852 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38853 and go on to the next; this allows us to extend the protocol in the
38857 The currently defined stop reasons are:
38863 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38866 @cindex shared library events, remote reply
38868 The packet indicates that the loaded libraries have changed.
38869 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38870 list of loaded libraries. @var{r} is ignored.
38872 @cindex replay log events, remote reply
38874 The packet indicates that the target cannot continue replaying
38875 logged execution events, because it has reached the end (or the
38876 beginning when executing backward) of the log. The value of @var{r}
38877 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38878 for more information.
38882 @itemx W @var{AA} ; process:@var{pid}
38883 The process exited, and @var{AA} is the exit status. This is only
38884 applicable to certain targets.
38886 The second form of the response, including the process ID of the exited
38887 process, can be used only when @value{GDBN} has reported support for
38888 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38889 The @var{pid} is formatted as a big-endian hex string.
38892 @itemx X @var{AA} ; process:@var{pid}
38893 The process terminated with signal @var{AA}.
38895 The second form of the response, including the process ID of the
38896 terminated process, can be used only when @value{GDBN} has reported
38897 support for multiprocess protocol extensions; see @ref{multiprocess
38898 extensions}. The @var{pid} is formatted as a big-endian hex string.
38900 @item O @var{XX}@dots{}
38901 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38902 written as the program's console output. This can happen at any time
38903 while the program is running and the debugger should continue to wait
38904 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38906 @item F @var{call-id},@var{parameter}@dots{}
38907 @var{call-id} is the identifier which says which host system call should
38908 be called. This is just the name of the function. Translation into the
38909 correct system call is only applicable as it's defined in @value{GDBN}.
38910 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38913 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38914 this very system call.
38916 The target replies with this packet when it expects @value{GDBN} to
38917 call a host system call on behalf of the target. @value{GDBN} replies
38918 with an appropriate @samp{F} packet and keeps up waiting for the next
38919 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38920 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38921 Protocol Extension}, for more details.
38925 @node General Query Packets
38926 @section General Query Packets
38927 @cindex remote query requests
38929 Packets starting with @samp{q} are @dfn{general query packets};
38930 packets starting with @samp{Q} are @dfn{general set packets}. General
38931 query and set packets are a semi-unified form for retrieving and
38932 sending information to and from the stub.
38934 The initial letter of a query or set packet is followed by a name
38935 indicating what sort of thing the packet applies to. For example,
38936 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38937 definitions with the stub. These packet names follow some
38942 The name must not contain commas, colons or semicolons.
38944 Most @value{GDBN} query and set packets have a leading upper case
38947 The names of custom vendor packets should use a company prefix, in
38948 lower case, followed by a period. For example, packets designed at
38949 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38950 foos) or @samp{Qacme.bar} (for setting bars).
38953 The name of a query or set packet should be separated from any
38954 parameters by a @samp{:}; the parameters themselves should be
38955 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38956 full packet name, and check for a separator or the end of the packet,
38957 in case two packet names share a common prefix. New packets should not begin
38958 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38959 packets predate these conventions, and have arguments without any terminator
38960 for the packet name; we suspect they are in widespread use in places that
38961 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38962 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38965 Like the descriptions of the other packets, each description here
38966 has a template showing the packet's overall syntax, followed by an
38967 explanation of the packet's meaning. We include spaces in some of the
38968 templates for clarity; these are not part of the packet's syntax. No
38969 @value{GDBN} packet uses spaces to separate its components.
38971 Here are the currently defined query and set packets:
38977 Turn on or off the agent as a helper to perform some debugging operations
38978 delegated from @value{GDBN} (@pxref{Control Agent}).
38980 @item QAllow:@var{op}:@var{val}@dots{}
38981 @cindex @samp{QAllow} packet
38982 Specify which operations @value{GDBN} expects to request of the
38983 target, as a semicolon-separated list of operation name and value
38984 pairs. Possible values for @var{op} include @samp{WriteReg},
38985 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38986 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38987 indicating that @value{GDBN} will not request the operation, or 1,
38988 indicating that it may. (The target can then use this to set up its
38989 own internals optimally, for instance if the debugger never expects to
38990 insert breakpoints, it may not need to install its own trap handler.)
38993 @cindex current thread, remote request
38994 @cindex @samp{qC} packet
38995 Return the current thread ID.
38999 @item QC @var{thread-id}
39000 Where @var{thread-id} is a thread ID as documented in
39001 @ref{thread-id syntax}.
39002 @item @r{(anything else)}
39003 Any other reply implies the old thread ID.
39006 @item qCRC:@var{addr},@var{length}
39007 @cindex CRC of memory block, remote request
39008 @cindex @samp{qCRC} packet
39009 Compute the CRC checksum of a block of memory using CRC-32 defined in
39010 IEEE 802.3. The CRC is computed byte at a time, taking the most
39011 significant bit of each byte first. The initial pattern code
39012 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
39014 @emph{Note:} This is the same CRC used in validating separate debug
39015 files (@pxref{Separate Debug Files, , Debugging Information in Separate
39016 Files}). However the algorithm is slightly different. When validating
39017 separate debug files, the CRC is computed taking the @emph{least}
39018 significant bit of each byte first, and the final result is inverted to
39019 detect trailing zeros.
39024 An error (such as memory fault)
39025 @item C @var{crc32}
39026 The specified memory region's checksum is @var{crc32}.
39029 @item QDisableRandomization:@var{value}
39030 @cindex disable address space randomization, remote request
39031 @cindex @samp{QDisableRandomization} packet
39032 Some target operating systems will randomize the virtual address space
39033 of the inferior process as a security feature, but provide a feature
39034 to disable such randomization, e.g.@: to allow for a more deterministic
39035 debugging experience. On such systems, this packet with a @var{value}
39036 of 1 directs the target to disable address space randomization for
39037 processes subsequently started via @samp{vRun} packets, while a packet
39038 with a @var{value} of 0 tells the target to enable address space
39041 This packet is only available in extended mode (@pxref{extended mode}).
39046 The request succeeded.
39049 An error occurred. @var{nn} are hex digits.
39052 An empty reply indicates that @samp{QDisableRandomization} is not supported
39056 This packet is not probed by default; the remote stub must request it,
39057 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39058 This should only be done on targets that actually support disabling
39059 address space randomization.
39062 @itemx qsThreadInfo
39063 @cindex list active threads, remote request
39064 @cindex @samp{qfThreadInfo} packet
39065 @cindex @samp{qsThreadInfo} packet
39066 Obtain a list of all active thread IDs from the target (OS). Since there
39067 may be too many active threads to fit into one reply packet, this query
39068 works iteratively: it may require more than one query/reply sequence to
39069 obtain the entire list of threads. The first query of the sequence will
39070 be the @samp{qfThreadInfo} query; subsequent queries in the
39071 sequence will be the @samp{qsThreadInfo} query.
39073 NOTE: This packet replaces the @samp{qL} query (see below).
39077 @item m @var{thread-id}
39079 @item m @var{thread-id},@var{thread-id}@dots{}
39080 a comma-separated list of thread IDs
39082 (lower case letter @samp{L}) denotes end of list.
39085 In response to each query, the target will reply with a list of one or
39086 more thread IDs, separated by commas.
39087 @value{GDBN} will respond to each reply with a request for more thread
39088 ids (using the @samp{qs} form of the query), until the target responds
39089 with @samp{l} (lower-case ell, for @dfn{last}).
39090 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
39093 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
39094 @cindex get thread-local storage address, remote request
39095 @cindex @samp{qGetTLSAddr} packet
39096 Fetch the address associated with thread local storage specified
39097 by @var{thread-id}, @var{offset}, and @var{lm}.
39099 @var{thread-id} is the thread ID associated with the
39100 thread for which to fetch the TLS address. @xref{thread-id syntax}.
39102 @var{offset} is the (big endian, hex encoded) offset associated with the
39103 thread local variable. (This offset is obtained from the debug
39104 information associated with the variable.)
39106 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
39107 load module associated with the thread local storage. For example,
39108 a @sc{gnu}/Linux system will pass the link map address of the shared
39109 object associated with the thread local storage under consideration.
39110 Other operating environments may choose to represent the load module
39111 differently, so the precise meaning of this parameter will vary.
39115 @item @var{XX}@dots{}
39116 Hex encoded (big endian) bytes representing the address of the thread
39117 local storage requested.
39120 An error occurred. @var{nn} are hex digits.
39123 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
39126 @item qGetTIBAddr:@var{thread-id}
39127 @cindex get thread information block address
39128 @cindex @samp{qGetTIBAddr} packet
39129 Fetch address of the Windows OS specific Thread Information Block.
39131 @var{thread-id} is the thread ID associated with the thread.
39135 @item @var{XX}@dots{}
39136 Hex encoded (big endian) bytes representing the linear address of the
39137 thread information block.
39140 An error occured. This means that either the thread was not found, or the
39141 address could not be retrieved.
39144 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
39147 @item qL @var{startflag} @var{threadcount} @var{nextthread}
39148 Obtain thread information from RTOS. Where: @var{startflag} (one hex
39149 digit) is one to indicate the first query and zero to indicate a
39150 subsequent query; @var{threadcount} (two hex digits) is the maximum
39151 number of threads the response packet can contain; and @var{nextthread}
39152 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
39153 returned in the response as @var{argthread}.
39155 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
39159 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
39160 Where: @var{count} (two hex digits) is the number of threads being
39161 returned; @var{done} (one hex digit) is zero to indicate more threads
39162 and one indicates no further threads; @var{argthreadid} (eight hex
39163 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
39164 is a sequence of thread IDs from the target. @var{threadid} (eight hex
39165 digits). See @code{remote.c:parse_threadlist_response()}.
39169 @cindex section offsets, remote request
39170 @cindex @samp{qOffsets} packet
39171 Get section offsets that the target used when relocating the downloaded
39176 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
39177 Relocate the @code{Text} section by @var{xxx} from its original address.
39178 Relocate the @code{Data} section by @var{yyy} from its original address.
39179 If the object file format provides segment information (e.g.@: @sc{elf}
39180 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
39181 segments by the supplied offsets.
39183 @emph{Note: while a @code{Bss} offset may be included in the response,
39184 @value{GDBN} ignores this and instead applies the @code{Data} offset
39185 to the @code{Bss} section.}
39187 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
39188 Relocate the first segment of the object file, which conventionally
39189 contains program code, to a starting address of @var{xxx}. If
39190 @samp{DataSeg} is specified, relocate the second segment, which
39191 conventionally contains modifiable data, to a starting address of
39192 @var{yyy}. @value{GDBN} will report an error if the object file
39193 does not contain segment information, or does not contain at least
39194 as many segments as mentioned in the reply. Extra segments are
39195 kept at fixed offsets relative to the last relocated segment.
39198 @item qP @var{mode} @var{thread-id}
39199 @cindex thread information, remote request
39200 @cindex @samp{qP} packet
39201 Returns information on @var{thread-id}. Where: @var{mode} is a hex
39202 encoded 32 bit mode; @var{thread-id} is a thread ID
39203 (@pxref{thread-id syntax}).
39205 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
39208 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
39212 @cindex non-stop mode, remote request
39213 @cindex @samp{QNonStop} packet
39215 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
39216 @xref{Remote Non-Stop}, for more information.
39221 The request succeeded.
39224 An error occurred. @var{nn} are hex digits.
39227 An empty reply indicates that @samp{QNonStop} is not supported by
39231 This packet is not probed by default; the remote stub must request it,
39232 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39233 Use of this packet is controlled by the @code{set non-stop} command;
39234 @pxref{Non-Stop Mode}.
39236 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39237 @cindex pass signals to inferior, remote request
39238 @cindex @samp{QPassSignals} packet
39239 @anchor{QPassSignals}
39240 Each listed @var{signal} should be passed directly to the inferior process.
39241 Signals are numbered identically to continue packets and stop replies
39242 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39243 strictly greater than the previous item. These signals do not need to stop
39244 the inferior, or be reported to @value{GDBN}. All other signals should be
39245 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
39246 combine; any earlier @samp{QPassSignals} list is completely replaced by the
39247 new list. This packet improves performance when using @samp{handle
39248 @var{signal} nostop noprint pass}.
39253 The request succeeded.
39256 An error occurred. @var{nn} are hex digits.
39259 An empty reply indicates that @samp{QPassSignals} is not supported by
39263 Use of this packet is controlled by the @code{set remote pass-signals}
39264 command (@pxref{Remote Configuration, set remote pass-signals}).
39265 This packet is not probed by default; the remote stub must request it,
39266 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39268 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
39269 @cindex signals the inferior may see, remote request
39270 @cindex @samp{QProgramSignals} packet
39271 @anchor{QProgramSignals}
39272 Each listed @var{signal} may be delivered to the inferior process.
39273 Others should be silently discarded.
39275 In some cases, the remote stub may need to decide whether to deliver a
39276 signal to the program or not without @value{GDBN} involvement. One
39277 example of that is while detaching --- the program's threads may have
39278 stopped for signals that haven't yet had a chance of being reported to
39279 @value{GDBN}, and so the remote stub can use the signal list specified
39280 by this packet to know whether to deliver or ignore those pending
39283 This does not influence whether to deliver a signal as requested by a
39284 resumption packet (@pxref{vCont packet}).
39286 Signals are numbered identically to continue packets and stop replies
39287 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
39288 strictly greater than the previous item. Multiple
39289 @samp{QProgramSignals} packets do not combine; any earlier
39290 @samp{QProgramSignals} list is completely replaced by the new list.
39295 The request succeeded.
39298 An error occurred. @var{nn} are hex digits.
39301 An empty reply indicates that @samp{QProgramSignals} is not supported
39305 Use of this packet is controlled by the @code{set remote program-signals}
39306 command (@pxref{Remote Configuration, set remote program-signals}).
39307 This packet is not probed by default; the remote stub must request it,
39308 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39310 @item qRcmd,@var{command}
39311 @cindex execute remote command, remote request
39312 @cindex @samp{qRcmd} packet
39313 @var{command} (hex encoded) is passed to the local interpreter for
39314 execution. Invalid commands should be reported using the output
39315 string. Before the final result packet, the target may also respond
39316 with a number of intermediate @samp{O@var{output}} console output
39317 packets. @emph{Implementors should note that providing access to a
39318 stubs's interpreter may have security implications}.
39323 A command response with no output.
39325 A command response with the hex encoded output string @var{OUTPUT}.
39327 Indicate a badly formed request.
39329 An empty reply indicates that @samp{qRcmd} is not recognized.
39332 (Note that the @code{qRcmd} packet's name is separated from the
39333 command by a @samp{,}, not a @samp{:}, contrary to the naming
39334 conventions above. Please don't use this packet as a model for new
39337 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
39338 @cindex searching memory, in remote debugging
39340 @cindex @samp{qSearch:memory} packet
39342 @cindex @samp{qSearch memory} packet
39343 @anchor{qSearch memory}
39344 Search @var{length} bytes at @var{address} for @var{search-pattern}.
39345 @var{address} and @var{length} are encoded in hex.
39346 @var{search-pattern} is a sequence of bytes, hex encoded.
39351 The pattern was not found.
39353 The pattern was found at @var{address}.
39355 A badly formed request or an error was encountered while searching memory.
39357 An empty reply indicates that @samp{qSearch:memory} is not recognized.
39360 @item QStartNoAckMode
39361 @cindex @samp{QStartNoAckMode} packet
39362 @anchor{QStartNoAckMode}
39363 Request that the remote stub disable the normal @samp{+}/@samp{-}
39364 protocol acknowledgments (@pxref{Packet Acknowledgment}).
39369 The stub has switched to no-acknowledgment mode.
39370 @value{GDBN} acknowledges this reponse,
39371 but neither the stub nor @value{GDBN} shall send or expect further
39372 @samp{+}/@samp{-} acknowledgments in the current connection.
39374 An empty reply indicates that the stub does not support no-acknowledgment mode.
39377 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
39378 @cindex supported packets, remote query
39379 @cindex features of the remote protocol
39380 @cindex @samp{qSupported} packet
39381 @anchor{qSupported}
39382 Tell the remote stub about features supported by @value{GDBN}, and
39383 query the stub for features it supports. This packet allows
39384 @value{GDBN} and the remote stub to take advantage of each others'
39385 features. @samp{qSupported} also consolidates multiple feature probes
39386 at startup, to improve @value{GDBN} performance---a single larger
39387 packet performs better than multiple smaller probe packets on
39388 high-latency links. Some features may enable behavior which must not
39389 be on by default, e.g.@: because it would confuse older clients or
39390 stubs. Other features may describe packets which could be
39391 automatically probed for, but are not. These features must be
39392 reported before @value{GDBN} will use them. This ``default
39393 unsupported'' behavior is not appropriate for all packets, but it
39394 helps to keep the initial connection time under control with new
39395 versions of @value{GDBN} which support increasing numbers of packets.
39399 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
39400 The stub supports or does not support each returned @var{stubfeature},
39401 depending on the form of each @var{stubfeature} (see below for the
39404 An empty reply indicates that @samp{qSupported} is not recognized,
39405 or that no features needed to be reported to @value{GDBN}.
39408 The allowed forms for each feature (either a @var{gdbfeature} in the
39409 @samp{qSupported} packet, or a @var{stubfeature} in the response)
39413 @item @var{name}=@var{value}
39414 The remote protocol feature @var{name} is supported, and associated
39415 with the specified @var{value}. The format of @var{value} depends
39416 on the feature, but it must not include a semicolon.
39418 The remote protocol feature @var{name} is supported, and does not
39419 need an associated value.
39421 The remote protocol feature @var{name} is not supported.
39423 The remote protocol feature @var{name} may be supported, and
39424 @value{GDBN} should auto-detect support in some other way when it is
39425 needed. This form will not be used for @var{gdbfeature} notifications,
39426 but may be used for @var{stubfeature} responses.
39429 Whenever the stub receives a @samp{qSupported} request, the
39430 supplied set of @value{GDBN} features should override any previous
39431 request. This allows @value{GDBN} to put the stub in a known
39432 state, even if the stub had previously been communicating with
39433 a different version of @value{GDBN}.
39435 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
39440 This feature indicates whether @value{GDBN} supports multiprocess
39441 extensions to the remote protocol. @value{GDBN} does not use such
39442 extensions unless the stub also reports that it supports them by
39443 including @samp{multiprocess+} in its @samp{qSupported} reply.
39444 @xref{multiprocess extensions}, for details.
39447 This feature indicates that @value{GDBN} supports the XML target
39448 description. If the stub sees @samp{xmlRegisters=} with target
39449 specific strings separated by a comma, it will report register
39453 This feature indicates whether @value{GDBN} supports the
39454 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
39455 instruction reply packet}).
39458 Stubs should ignore any unknown values for
39459 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
39460 packet supports receiving packets of unlimited length (earlier
39461 versions of @value{GDBN} may reject overly long responses). Additional values
39462 for @var{gdbfeature} may be defined in the future to let the stub take
39463 advantage of new features in @value{GDBN}, e.g.@: incompatible
39464 improvements in the remote protocol---the @samp{multiprocess} feature is
39465 an example of such a feature. The stub's reply should be independent
39466 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
39467 describes all the features it supports, and then the stub replies with
39468 all the features it supports.
39470 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
39471 responses, as long as each response uses one of the standard forms.
39473 Some features are flags. A stub which supports a flag feature
39474 should respond with a @samp{+} form response. Other features
39475 require values, and the stub should respond with an @samp{=}
39478 Each feature has a default value, which @value{GDBN} will use if
39479 @samp{qSupported} is not available or if the feature is not mentioned
39480 in the @samp{qSupported} response. The default values are fixed; a
39481 stub is free to omit any feature responses that match the defaults.
39483 Not all features can be probed, but for those which can, the probing
39484 mechanism is useful: in some cases, a stub's internal
39485 architecture may not allow the protocol layer to know some information
39486 about the underlying target in advance. This is especially common in
39487 stubs which may be configured for multiple targets.
39489 These are the currently defined stub features and their properties:
39491 @multitable @columnfractions 0.35 0.2 0.12 0.2
39492 @c NOTE: The first row should be @headitem, but we do not yet require
39493 @c a new enough version of Texinfo (4.7) to use @headitem.
39495 @tab Value Required
39499 @item @samp{PacketSize}
39504 @item @samp{qXfer:auxv:read}
39509 @item @samp{qXfer:btrace:read}
39514 @item @samp{qXfer:features:read}
39519 @item @samp{qXfer:libraries:read}
39524 @item @samp{qXfer:libraries-svr4:read}
39529 @item @samp{augmented-libraries-svr4-read}
39534 @item @samp{qXfer:memory-map:read}
39539 @item @samp{qXfer:sdata:read}
39544 @item @samp{qXfer:spu:read}
39549 @item @samp{qXfer:spu:write}
39554 @item @samp{qXfer:siginfo:read}
39559 @item @samp{qXfer:siginfo:write}
39564 @item @samp{qXfer:threads:read}
39569 @item @samp{qXfer:traceframe-info:read}
39574 @item @samp{qXfer:uib:read}
39579 @item @samp{qXfer:fdpic:read}
39584 @item @samp{Qbtrace:off}
39589 @item @samp{Qbtrace:bts}
39594 @item @samp{QNonStop}
39599 @item @samp{QPassSignals}
39604 @item @samp{QStartNoAckMode}
39609 @item @samp{multiprocess}
39614 @item @samp{ConditionalBreakpoints}
39619 @item @samp{ConditionalTracepoints}
39624 @item @samp{ReverseContinue}
39629 @item @samp{ReverseStep}
39634 @item @samp{TracepointSource}
39639 @item @samp{QAgent}
39644 @item @samp{QAllow}
39649 @item @samp{QDisableRandomization}
39654 @item @samp{EnableDisableTracepoints}
39659 @item @samp{QTBuffer:size}
39664 @item @samp{tracenz}
39669 @item @samp{BreakpointCommands}
39676 These are the currently defined stub features, in more detail:
39679 @cindex packet size, remote protocol
39680 @item PacketSize=@var{bytes}
39681 The remote stub can accept packets up to at least @var{bytes} in
39682 length. @value{GDBN} will send packets up to this size for bulk
39683 transfers, and will never send larger packets. This is a limit on the
39684 data characters in the packet, including the frame and checksum.
39685 There is no trailing NUL byte in a remote protocol packet; if the stub
39686 stores packets in a NUL-terminated format, it should allow an extra
39687 byte in its buffer for the NUL. If this stub feature is not supported,
39688 @value{GDBN} guesses based on the size of the @samp{g} packet response.
39690 @item qXfer:auxv:read
39691 The remote stub understands the @samp{qXfer:auxv:read} packet
39692 (@pxref{qXfer auxiliary vector read}).
39694 @item qXfer:btrace:read
39695 The remote stub understands the @samp{qXfer:btrace:read}
39696 packet (@pxref{qXfer btrace read}).
39698 @item qXfer:features:read
39699 The remote stub understands the @samp{qXfer:features:read} packet
39700 (@pxref{qXfer target description read}).
39702 @item qXfer:libraries:read
39703 The remote stub understands the @samp{qXfer:libraries:read} packet
39704 (@pxref{qXfer library list read}).
39706 @item qXfer:libraries-svr4:read
39707 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
39708 (@pxref{qXfer svr4 library list read}).
39710 @item augmented-libraries-svr4-read
39711 The remote stub understands the augmented form of the
39712 @samp{qXfer:libraries-svr4:read} packet
39713 (@pxref{qXfer svr4 library list read}).
39715 @item qXfer:memory-map:read
39716 The remote stub understands the @samp{qXfer:memory-map:read} packet
39717 (@pxref{qXfer memory map read}).
39719 @item qXfer:sdata:read
39720 The remote stub understands the @samp{qXfer:sdata:read} packet
39721 (@pxref{qXfer sdata read}).
39723 @item qXfer:spu:read
39724 The remote stub understands the @samp{qXfer:spu:read} packet
39725 (@pxref{qXfer spu read}).
39727 @item qXfer:spu:write
39728 The remote stub understands the @samp{qXfer:spu:write} packet
39729 (@pxref{qXfer spu write}).
39731 @item qXfer:siginfo:read
39732 The remote stub understands the @samp{qXfer:siginfo:read} packet
39733 (@pxref{qXfer siginfo read}).
39735 @item qXfer:siginfo:write
39736 The remote stub understands the @samp{qXfer:siginfo:write} packet
39737 (@pxref{qXfer siginfo write}).
39739 @item qXfer:threads:read
39740 The remote stub understands the @samp{qXfer:threads:read} packet
39741 (@pxref{qXfer threads read}).
39743 @item qXfer:traceframe-info:read
39744 The remote stub understands the @samp{qXfer:traceframe-info:read}
39745 packet (@pxref{qXfer traceframe info read}).
39747 @item qXfer:uib:read
39748 The remote stub understands the @samp{qXfer:uib:read}
39749 packet (@pxref{qXfer unwind info block}).
39751 @item qXfer:fdpic:read
39752 The remote stub understands the @samp{qXfer:fdpic:read}
39753 packet (@pxref{qXfer fdpic loadmap read}).
39756 The remote stub understands the @samp{QNonStop} packet
39757 (@pxref{QNonStop}).
39760 The remote stub understands the @samp{QPassSignals} packet
39761 (@pxref{QPassSignals}).
39763 @item QStartNoAckMode
39764 The remote stub understands the @samp{QStartNoAckMode} packet and
39765 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39768 @anchor{multiprocess extensions}
39769 @cindex multiprocess extensions, in remote protocol
39770 The remote stub understands the multiprocess extensions to the remote
39771 protocol syntax. The multiprocess extensions affect the syntax of
39772 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39773 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39774 replies. Note that reporting this feature indicates support for the
39775 syntactic extensions only, not that the stub necessarily supports
39776 debugging of more than one process at a time. The stub must not use
39777 multiprocess extensions in packet replies unless @value{GDBN} has also
39778 indicated it supports them in its @samp{qSupported} request.
39780 @item qXfer:osdata:read
39781 The remote stub understands the @samp{qXfer:osdata:read} packet
39782 ((@pxref{qXfer osdata read}).
39784 @item ConditionalBreakpoints
39785 The target accepts and implements evaluation of conditional expressions
39786 defined for breakpoints. The target will only report breakpoint triggers
39787 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39789 @item ConditionalTracepoints
39790 The remote stub accepts and implements conditional expressions defined
39791 for tracepoints (@pxref{Tracepoint Conditions}).
39793 @item ReverseContinue
39794 The remote stub accepts and implements the reverse continue packet
39798 The remote stub accepts and implements the reverse step packet
39801 @item TracepointSource
39802 The remote stub understands the @samp{QTDPsrc} packet that supplies
39803 the source form of tracepoint definitions.
39806 The remote stub understands the @samp{QAgent} packet.
39809 The remote stub understands the @samp{QAllow} packet.
39811 @item QDisableRandomization
39812 The remote stub understands the @samp{QDisableRandomization} packet.
39814 @item StaticTracepoint
39815 @cindex static tracepoints, in remote protocol
39816 The remote stub supports static tracepoints.
39818 @item InstallInTrace
39819 @anchor{install tracepoint in tracing}
39820 The remote stub supports installing tracepoint in tracing.
39822 @item EnableDisableTracepoints
39823 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39824 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39825 to be enabled and disabled while a trace experiment is running.
39827 @item QTBuffer:size
39828 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39829 packet that allows to change the size of the trace buffer.
39832 @cindex string tracing, in remote protocol
39833 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39834 See @ref{Bytecode Descriptions} for details about the bytecode.
39836 @item BreakpointCommands
39837 @cindex breakpoint commands, in remote protocol
39838 The remote stub supports running a breakpoint's command list itself,
39839 rather than reporting the hit to @value{GDBN}.
39842 The remote stub understands the @samp{Qbtrace:off} packet.
39845 The remote stub understands the @samp{Qbtrace:bts} packet.
39850 @cindex symbol lookup, remote request
39851 @cindex @samp{qSymbol} packet
39852 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39853 requests. Accept requests from the target for the values of symbols.
39858 The target does not need to look up any (more) symbols.
39859 @item qSymbol:@var{sym_name}
39860 The target requests the value of symbol @var{sym_name} (hex encoded).
39861 @value{GDBN} may provide the value by using the
39862 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39866 @item qSymbol:@var{sym_value}:@var{sym_name}
39867 Set the value of @var{sym_name} to @var{sym_value}.
39869 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39870 target has previously requested.
39872 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39873 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39879 The target does not need to look up any (more) symbols.
39880 @item qSymbol:@var{sym_name}
39881 The target requests the value of a new symbol @var{sym_name} (hex
39882 encoded). @value{GDBN} will continue to supply the values of symbols
39883 (if available), until the target ceases to request them.
39888 @itemx QTDisconnected
39895 @itemx qTMinFTPILen
39897 @xref{Tracepoint Packets}.
39899 @item qThreadExtraInfo,@var{thread-id}
39900 @cindex thread attributes info, remote request
39901 @cindex @samp{qThreadExtraInfo} packet
39902 Obtain a printable string description of a thread's attributes from
39903 the target OS. @var{thread-id} is a thread ID;
39904 see @ref{thread-id syntax}. This
39905 string may contain anything that the target OS thinks is interesting
39906 for @value{GDBN} to tell the user about the thread. The string is
39907 displayed in @value{GDBN}'s @code{info threads} display. Some
39908 examples of possible thread extra info strings are @samp{Runnable}, or
39909 @samp{Blocked on Mutex}.
39913 @item @var{XX}@dots{}
39914 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39915 comprising the printable string containing the extra information about
39916 the thread's attributes.
39919 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39920 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39921 conventions above. Please don't use this packet as a model for new
39940 @xref{Tracepoint Packets}.
39942 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39943 @cindex read special object, remote request
39944 @cindex @samp{qXfer} packet
39945 @anchor{qXfer read}
39946 Read uninterpreted bytes from the target's special data area
39947 identified by the keyword @var{object}. Request @var{length} bytes
39948 starting at @var{offset} bytes into the data. The content and
39949 encoding of @var{annex} is specific to @var{object}; it can supply
39950 additional details about what data to access.
39952 Here are the specific requests of this form defined so far. All
39953 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39954 formats, listed below.
39957 @item qXfer:auxv:read::@var{offset},@var{length}
39958 @anchor{qXfer auxiliary vector read}
39959 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39960 auxiliary vector}. Note @var{annex} must be empty.
39962 This packet is not probed by default; the remote stub must request it,
39963 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39965 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39966 @anchor{qXfer btrace read}
39968 Return a description of the current branch trace.
39969 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39970 packet may have one of the following values:
39974 Returns all available branch trace.
39977 Returns all available branch trace if the branch trace changed since
39978 the last read request.
39981 This packet is not probed by default; the remote stub must request it
39982 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39984 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39985 @anchor{qXfer target description read}
39986 Access the @dfn{target description}. @xref{Target Descriptions}. The
39987 annex specifies which XML document to access. The main description is
39988 always loaded from the @samp{target.xml} annex.
39990 This packet is not probed by default; the remote stub must request it,
39991 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39993 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39994 @anchor{qXfer library list read}
39995 Access the target's list of loaded libraries. @xref{Library List Format}.
39996 The annex part of the generic @samp{qXfer} packet must be empty
39997 (@pxref{qXfer read}).
39999 Targets which maintain a list of libraries in the program's memory do
40000 not need to implement this packet; it is designed for platforms where
40001 the operating system manages the list of loaded libraries.
40003 This packet is not probed by default; the remote stub must request it,
40004 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40006 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
40007 @anchor{qXfer svr4 library list read}
40008 Access the target's list of loaded libraries when the target is an SVR4
40009 platform. @xref{Library List Format for SVR4 Targets}. The annex part
40010 of the generic @samp{qXfer} packet must be empty unless the remote
40011 stub indicated it supports the augmented form of this packet
40012 by supplying an appropriate @samp{qSupported} response
40013 (@pxref{qXfer read}, @ref{qSupported}).
40015 This packet is optional for better performance on SVR4 targets.
40016 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
40018 This packet is not probed by default; the remote stub must request it,
40019 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40021 If the remote stub indicates it supports the augmented form of this
40022 packet then the annex part of the generic @samp{qXfer} packet may
40023 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
40024 arguments. The currently supported arguments are:
40027 @item start=@var{address}
40028 A hexadecimal number specifying the address of the @samp{struct
40029 link_map} to start reading the library list from. If unset or zero
40030 then the first @samp{struct link_map} in the library list will be
40031 chosen as the starting point.
40033 @item prev=@var{address}
40034 A hexadecimal number specifying the address of the @samp{struct
40035 link_map} immediately preceding the @samp{struct link_map}
40036 specified by the @samp{start} argument. If unset or zero then
40037 the remote stub will expect that no @samp{struct link_map}
40038 exists prior to the starting point.
40042 Arguments that are not understood by the remote stub will be silently
40045 @item qXfer:memory-map:read::@var{offset},@var{length}
40046 @anchor{qXfer memory map read}
40047 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
40048 annex part of the generic @samp{qXfer} packet must be empty
40049 (@pxref{qXfer read}).
40051 This packet is not probed by default; the remote stub must request it,
40052 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40054 @item qXfer:sdata:read::@var{offset},@var{length}
40055 @anchor{qXfer sdata read}
40057 Read contents of the extra collected static tracepoint marker
40058 information. The annex part of the generic @samp{qXfer} packet must
40059 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
40062 This packet is not probed by default; the remote stub must request it,
40063 by supplying an appropriate @samp{qSupported} response
40064 (@pxref{qSupported}).
40066 @item qXfer:siginfo:read::@var{offset},@var{length}
40067 @anchor{qXfer siginfo read}
40068 Read contents of the extra signal information on the target
40069 system. The annex part of the generic @samp{qXfer} packet must be
40070 empty (@pxref{qXfer read}).
40072 This packet is not probed by default; the remote stub must request it,
40073 by supplying an appropriate @samp{qSupported} response
40074 (@pxref{qSupported}).
40076 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
40077 @anchor{qXfer spu read}
40078 Read contents of an @code{spufs} file on the target system. The
40079 annex specifies which file to read; it must be of the form
40080 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40081 in the target process, and @var{name} identifes the @code{spufs} file
40082 in that context to be accessed.
40084 This packet is not probed by default; the remote stub must request it,
40085 by supplying an appropriate @samp{qSupported} response
40086 (@pxref{qSupported}).
40088 @item qXfer:threads:read::@var{offset},@var{length}
40089 @anchor{qXfer threads read}
40090 Access the list of threads on target. @xref{Thread List Format}. The
40091 annex part of the generic @samp{qXfer} packet must be empty
40092 (@pxref{qXfer read}).
40094 This packet is not probed by default; the remote stub must request it,
40095 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40097 @item qXfer:traceframe-info:read::@var{offset},@var{length}
40098 @anchor{qXfer traceframe info read}
40100 Return a description of the current traceframe's contents.
40101 @xref{Traceframe Info Format}. The annex part of the generic
40102 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
40104 This packet is not probed by default; the remote stub must request it,
40105 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40107 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
40108 @anchor{qXfer unwind info block}
40110 Return the unwind information block for @var{pc}. This packet is used
40111 on OpenVMS/ia64 to ask the kernel unwind information.
40113 This packet is not probed by default.
40115 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
40116 @anchor{qXfer fdpic loadmap read}
40117 Read contents of @code{loadmap}s on the target system. The
40118 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
40119 executable @code{loadmap} or interpreter @code{loadmap} to read.
40121 This packet is not probed by default; the remote stub must request it,
40122 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40124 @item qXfer:osdata:read::@var{offset},@var{length}
40125 @anchor{qXfer osdata read}
40126 Access the target's @dfn{operating system information}.
40127 @xref{Operating System Information}.
40134 Data @var{data} (@pxref{Binary Data}) has been read from the
40135 target. There may be more data at a higher address (although
40136 it is permitted to return @samp{m} even for the last valid
40137 block of data, as long as at least one byte of data was read).
40138 @var{data} may have fewer bytes than the @var{length} in the
40142 Data @var{data} (@pxref{Binary Data}) has been read from the target.
40143 There is no more data to be read. @var{data} may have fewer bytes
40144 than the @var{length} in the request.
40147 The @var{offset} in the request is at the end of the data.
40148 There is no more data to be read.
40151 The request was malformed, or @var{annex} was invalid.
40154 The offset was invalid, or there was an error encountered reading the data.
40155 @var{nn} is a hex-encoded @code{errno} value.
40158 An empty reply indicates the @var{object} string was not recognized by
40159 the stub, or that the object does not support reading.
40162 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
40163 @cindex write data into object, remote request
40164 @anchor{qXfer write}
40165 Write uninterpreted bytes into the target's special data area
40166 identified by the keyword @var{object}, starting at @var{offset} bytes
40167 into the data. @var{data}@dots{} is the binary-encoded data
40168 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
40169 is specific to @var{object}; it can supply additional details about what data
40172 Here are the specific requests of this form defined so far. All
40173 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
40174 formats, listed below.
40177 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
40178 @anchor{qXfer siginfo write}
40179 Write @var{data} to the extra signal information on the target system.
40180 The annex part of the generic @samp{qXfer} packet must be
40181 empty (@pxref{qXfer write}).
40183 This packet is not probed by default; the remote stub must request it,
40184 by supplying an appropriate @samp{qSupported} response
40185 (@pxref{qSupported}).
40187 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
40188 @anchor{qXfer spu write}
40189 Write @var{data} to an @code{spufs} file on the target system. The
40190 annex specifies which file to write; it must be of the form
40191 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
40192 in the target process, and @var{name} identifes the @code{spufs} file
40193 in that context to be accessed.
40195 This packet is not probed by default; the remote stub must request it,
40196 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
40202 @var{nn} (hex encoded) is the number of bytes written.
40203 This may be fewer bytes than supplied in the request.
40206 The request was malformed, or @var{annex} was invalid.
40209 The offset was invalid, or there was an error encountered writing the data.
40210 @var{nn} is a hex-encoded @code{errno} value.
40213 An empty reply indicates the @var{object} string was not
40214 recognized by the stub, or that the object does not support writing.
40217 @item qXfer:@var{object}:@var{operation}:@dots{}
40218 Requests of this form may be added in the future. When a stub does
40219 not recognize the @var{object} keyword, or its support for
40220 @var{object} does not recognize the @var{operation} keyword, the stub
40221 must respond with an empty packet.
40223 @item qAttached:@var{pid}
40224 @cindex query attached, remote request
40225 @cindex @samp{qAttached} packet
40226 Return an indication of whether the remote server attached to an
40227 existing process or created a new process. When the multiprocess
40228 protocol extensions are supported (@pxref{multiprocess extensions}),
40229 @var{pid} is an integer in hexadecimal format identifying the target
40230 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
40231 the query packet will be simplified as @samp{qAttached}.
40233 This query is used, for example, to know whether the remote process
40234 should be detached or killed when a @value{GDBN} session is ended with
40235 the @code{quit} command.
40240 The remote server attached to an existing process.
40242 The remote server created a new process.
40244 A badly formed request or an error was encountered.
40248 Enable branch tracing for the current thread using bts tracing.
40253 Branch tracing has been enabled.
40255 A badly formed request or an error was encountered.
40259 Disable branch tracing for the current thread.
40264 Branch tracing has been disabled.
40266 A badly formed request or an error was encountered.
40271 @node Architecture-Specific Protocol Details
40272 @section Architecture-Specific Protocol Details
40274 This section describes how the remote protocol is applied to specific
40275 target architectures. Also see @ref{Standard Target Features}, for
40276 details of XML target descriptions for each architecture.
40279 * ARM-Specific Protocol Details::
40280 * MIPS-Specific Protocol Details::
40283 @node ARM-Specific Protocol Details
40284 @subsection @acronym{ARM}-specific Protocol Details
40287 * ARM Breakpoint Kinds::
40290 @node ARM Breakpoint Kinds
40291 @subsubsection @acronym{ARM} Breakpoint Kinds
40292 @cindex breakpoint kinds, @acronym{ARM}
40294 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40299 16-bit Thumb mode breakpoint.
40302 32-bit Thumb mode (Thumb-2) breakpoint.
40305 32-bit @acronym{ARM} mode breakpoint.
40309 @node MIPS-Specific Protocol Details
40310 @subsection @acronym{MIPS}-specific Protocol Details
40313 * MIPS Register packet Format::
40314 * MIPS Breakpoint Kinds::
40317 @node MIPS Register packet Format
40318 @subsubsection @acronym{MIPS} Register Packet Format
40319 @cindex register packet format, @acronym{MIPS}
40321 The following @code{g}/@code{G} packets have previously been defined.
40322 In the below, some thirty-two bit registers are transferred as
40323 sixty-four bits. Those registers should be zero/sign extended (which?)
40324 to fill the space allocated. Register bytes are transferred in target
40325 byte order. The two nibbles within a register byte are transferred
40326 most-significant -- least-significant.
40331 All registers are transferred as thirty-two bit quantities in the order:
40332 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
40333 registers; fsr; fir; fp.
40336 All registers are transferred as sixty-four bit quantities (including
40337 thirty-two bit registers such as @code{sr}). The ordering is the same
40342 @node MIPS Breakpoint Kinds
40343 @subsubsection @acronym{MIPS} Breakpoint Kinds
40344 @cindex breakpoint kinds, @acronym{MIPS}
40346 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
40351 16-bit @acronym{MIPS16} mode breakpoint.
40354 16-bit @acronym{microMIPS} mode breakpoint.
40357 32-bit standard @acronym{MIPS} mode breakpoint.
40360 32-bit @acronym{microMIPS} mode breakpoint.
40364 @node Tracepoint Packets
40365 @section Tracepoint Packets
40366 @cindex tracepoint packets
40367 @cindex packets, tracepoint
40369 Here we describe the packets @value{GDBN} uses to implement
40370 tracepoints (@pxref{Tracepoints}).
40374 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
40375 @cindex @samp{QTDP} packet
40376 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
40377 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
40378 the tracepoint is disabled. @var{step} is the tracepoint's step
40379 count, and @var{pass} is its pass count. If an @samp{F} is present,
40380 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
40381 the number of bytes that the target should copy elsewhere to make room
40382 for the tracepoint. If an @samp{X} is present, it introduces a
40383 tracepoint condition, which consists of a hexadecimal length, followed
40384 by a comma and hex-encoded bytes, in a manner similar to action
40385 encodings as described below. If the trailing @samp{-} is present,
40386 further @samp{QTDP} packets will follow to specify this tracepoint's
40392 The packet was understood and carried out.
40394 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40396 The packet was not recognized.
40399 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
40400 Define actions to be taken when a tracepoint is hit. @var{n} and
40401 @var{addr} must be the same as in the initial @samp{QTDP} packet for
40402 this tracepoint. This packet may only be sent immediately after
40403 another @samp{QTDP} packet that ended with a @samp{-}. If the
40404 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
40405 specifying more actions for this tracepoint.
40407 In the series of action packets for a given tracepoint, at most one
40408 can have an @samp{S} before its first @var{action}. If such a packet
40409 is sent, it and the following packets define ``while-stepping''
40410 actions. Any prior packets define ordinary actions --- that is, those
40411 taken when the tracepoint is first hit. If no action packet has an
40412 @samp{S}, then all the packets in the series specify ordinary
40413 tracepoint actions.
40415 The @samp{@var{action}@dots{}} portion of the packet is a series of
40416 actions, concatenated without separators. Each action has one of the
40422 Collect the registers whose bits are set in @var{mask}. @var{mask} is
40423 a hexadecimal number whose @var{i}'th bit is set if register number
40424 @var{i} should be collected. (The least significant bit is numbered
40425 zero.) Note that @var{mask} may be any number of digits long; it may
40426 not fit in a 32-bit word.
40428 @item M @var{basereg},@var{offset},@var{len}
40429 Collect @var{len} bytes of memory starting at the address in register
40430 number @var{basereg}, plus @var{offset}. If @var{basereg} is
40431 @samp{-1}, then the range has a fixed address: @var{offset} is the
40432 address of the lowest byte to collect. The @var{basereg},
40433 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
40434 values (the @samp{-1} value for @var{basereg} is a special case).
40436 @item X @var{len},@var{expr}
40437 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
40438 it directs. @var{expr} is an agent expression, as described in
40439 @ref{Agent Expressions}. Each byte of the expression is encoded as a
40440 two-digit hex number in the packet; @var{len} is the number of bytes
40441 in the expression (and thus one-half the number of hex digits in the
40446 Any number of actions may be packed together in a single @samp{QTDP}
40447 packet, as long as the packet does not exceed the maximum packet
40448 length (400 bytes, for many stubs). There may be only one @samp{R}
40449 action per tracepoint, and it must precede any @samp{M} or @samp{X}
40450 actions. Any registers referred to by @samp{M} and @samp{X} actions
40451 must be collected by a preceding @samp{R} action. (The
40452 ``while-stepping'' actions are treated as if they were attached to a
40453 separate tracepoint, as far as these restrictions are concerned.)
40458 The packet was understood and carried out.
40460 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
40462 The packet was not recognized.
40465 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
40466 @cindex @samp{QTDPsrc} packet
40467 Specify a source string of tracepoint @var{n} at address @var{addr}.
40468 This is useful to get accurate reproduction of the tracepoints
40469 originally downloaded at the beginning of the trace run. @var{type}
40470 is the name of the tracepoint part, such as @samp{cond} for the
40471 tracepoint's conditional expression (see below for a list of types), while
40472 @var{bytes} is the string, encoded in hexadecimal.
40474 @var{start} is the offset of the @var{bytes} within the overall source
40475 string, while @var{slen} is the total length of the source string.
40476 This is intended for handling source strings that are longer than will
40477 fit in a single packet.
40478 @c Add detailed example when this info is moved into a dedicated
40479 @c tracepoint descriptions section.
40481 The available string types are @samp{at} for the location,
40482 @samp{cond} for the conditional, and @samp{cmd} for an action command.
40483 @value{GDBN} sends a separate packet for each command in the action
40484 list, in the same order in which the commands are stored in the list.
40486 The target does not need to do anything with source strings except
40487 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
40490 Although this packet is optional, and @value{GDBN} will only send it
40491 if the target replies with @samp{TracepointSource} @xref{General
40492 Query Packets}, it makes both disconnected tracing and trace files
40493 much easier to use. Otherwise the user must be careful that the
40494 tracepoints in effect while looking at trace frames are identical to
40495 the ones in effect during the trace run; even a small discrepancy
40496 could cause @samp{tdump} not to work, or a particular trace frame not
40499 @item QTDV:@var{n}:@var{value}
40500 @cindex define trace state variable, remote request
40501 @cindex @samp{QTDV} packet
40502 Create a new trace state variable, number @var{n}, with an initial
40503 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
40504 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
40505 the option of not using this packet for initial values of zero; the
40506 target should simply create the trace state variables as they are
40507 mentioned in expressions.
40509 @item QTFrame:@var{n}
40510 @cindex @samp{QTFrame} packet
40511 Select the @var{n}'th tracepoint frame from the buffer, and use the
40512 register and memory contents recorded there to answer subsequent
40513 request packets from @value{GDBN}.
40515 A successful reply from the stub indicates that the stub has found the
40516 requested frame. The response is a series of parts, concatenated
40517 without separators, describing the frame we selected. Each part has
40518 one of the following forms:
40522 The selected frame is number @var{n} in the trace frame buffer;
40523 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
40524 was no frame matching the criteria in the request packet.
40527 The selected trace frame records a hit of tracepoint number @var{t};
40528 @var{t} is a hexadecimal number.
40532 @item QTFrame:pc:@var{addr}
40533 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40534 currently selected frame whose PC is @var{addr};
40535 @var{addr} is a hexadecimal number.
40537 @item QTFrame:tdp:@var{t}
40538 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40539 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
40540 is a hexadecimal number.
40542 @item QTFrame:range:@var{start}:@var{end}
40543 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
40544 currently selected frame whose PC is between @var{start} (inclusive)
40545 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
40548 @item QTFrame:outside:@var{start}:@var{end}
40549 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
40550 frame @emph{outside} the given range of addresses (exclusive).
40553 @cindex @samp{qTMinFTPILen} packet
40554 This packet requests the minimum length of instruction at which a fast
40555 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
40556 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
40557 it depends on the target system being able to create trampolines in
40558 the first 64K of memory, which might or might not be possible for that
40559 system. So the reply to this packet will be 4 if it is able to
40566 The minimum instruction length is currently unknown.
40568 The minimum instruction length is @var{length}, where @var{length} is greater
40569 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
40570 that a fast tracepoint may be placed on any instruction regardless of size.
40572 An error has occurred.
40574 An empty reply indicates that the request is not supported by the stub.
40578 @cindex @samp{QTStart} packet
40579 Begin the tracepoint experiment. Begin collecting data from
40580 tracepoint hits in the trace frame buffer. This packet supports the
40581 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
40582 instruction reply packet}).
40585 @cindex @samp{QTStop} packet
40586 End the tracepoint experiment. Stop collecting trace frames.
40588 @item QTEnable:@var{n}:@var{addr}
40590 @cindex @samp{QTEnable} packet
40591 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
40592 experiment. If the tracepoint was previously disabled, then collection
40593 of data from it will resume.
40595 @item QTDisable:@var{n}:@var{addr}
40597 @cindex @samp{QTDisable} packet
40598 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
40599 experiment. No more data will be collected from the tracepoint unless
40600 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
40603 @cindex @samp{QTinit} packet
40604 Clear the table of tracepoints, and empty the trace frame buffer.
40606 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
40607 @cindex @samp{QTro} packet
40608 Establish the given ranges of memory as ``transparent''. The stub
40609 will answer requests for these ranges from memory's current contents,
40610 if they were not collected as part of the tracepoint hit.
40612 @value{GDBN} uses this to mark read-only regions of memory, like those
40613 containing program code. Since these areas never change, they should
40614 still have the same contents they did when the tracepoint was hit, so
40615 there's no reason for the stub to refuse to provide their contents.
40617 @item QTDisconnected:@var{value}
40618 @cindex @samp{QTDisconnected} packet
40619 Set the choice to what to do with the tracing run when @value{GDBN}
40620 disconnects from the target. A @var{value} of 1 directs the target to
40621 continue the tracing run, while 0 tells the target to stop tracing if
40622 @value{GDBN} is no longer in the picture.
40625 @cindex @samp{qTStatus} packet
40626 Ask the stub if there is a trace experiment running right now.
40628 The reply has the form:
40632 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
40633 @var{running} is a single digit @code{1} if the trace is presently
40634 running, or @code{0} if not. It is followed by semicolon-separated
40635 optional fields that an agent may use to report additional status.
40639 If the trace is not running, the agent may report any of several
40640 explanations as one of the optional fields:
40645 No trace has been run yet.
40647 @item tstop[:@var{text}]:0
40648 The trace was stopped by a user-originated stop command. The optional
40649 @var{text} field is a user-supplied string supplied as part of the
40650 stop command (for instance, an explanation of why the trace was
40651 stopped manually). It is hex-encoded.
40654 The trace stopped because the trace buffer filled up.
40656 @item tdisconnected:0
40657 The trace stopped because @value{GDBN} disconnected from the target.
40659 @item tpasscount:@var{tpnum}
40660 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
40662 @item terror:@var{text}:@var{tpnum}
40663 The trace stopped because tracepoint @var{tpnum} had an error. The
40664 string @var{text} is available to describe the nature of the error
40665 (for instance, a divide by zero in the condition expression).
40666 @var{text} is hex encoded.
40669 The trace stopped for some other reason.
40673 Additional optional fields supply statistical and other information.
40674 Although not required, they are extremely useful for users monitoring
40675 the progress of a trace run. If a trace has stopped, and these
40676 numbers are reported, they must reflect the state of the just-stopped
40681 @item tframes:@var{n}
40682 The number of trace frames in the buffer.
40684 @item tcreated:@var{n}
40685 The total number of trace frames created during the run. This may
40686 be larger than the trace frame count, if the buffer is circular.
40688 @item tsize:@var{n}
40689 The total size of the trace buffer, in bytes.
40691 @item tfree:@var{n}
40692 The number of bytes still unused in the buffer.
40694 @item circular:@var{n}
40695 The value of the circular trace buffer flag. @code{1} means that the
40696 trace buffer is circular and old trace frames will be discarded if
40697 necessary to make room, @code{0} means that the trace buffer is linear
40700 @item disconn:@var{n}
40701 The value of the disconnected tracing flag. @code{1} means that
40702 tracing will continue after @value{GDBN} disconnects, @code{0} means
40703 that the trace run will stop.
40707 @item qTP:@var{tp}:@var{addr}
40708 @cindex tracepoint status, remote request
40709 @cindex @samp{qTP} packet
40710 Ask the stub for the current state of tracepoint number @var{tp} at
40711 address @var{addr}.
40715 @item V@var{hits}:@var{usage}
40716 The tracepoint has been hit @var{hits} times so far during the trace
40717 run, and accounts for @var{usage} in the trace buffer. Note that
40718 @code{while-stepping} steps are not counted as separate hits, but the
40719 steps' space consumption is added into the usage number.
40723 @item qTV:@var{var}
40724 @cindex trace state variable value, remote request
40725 @cindex @samp{qTV} packet
40726 Ask the stub for the value of the trace state variable number @var{var}.
40731 The value of the variable is @var{value}. This will be the current
40732 value of the variable if the user is examining a running target, or a
40733 saved value if the variable was collected in the trace frame that the
40734 user is looking at. Note that multiple requests may result in
40735 different reply values, such as when requesting values while the
40736 program is running.
40739 The value of the variable is unknown. This would occur, for example,
40740 if the user is examining a trace frame in which the requested variable
40745 @cindex @samp{qTfP} packet
40747 @cindex @samp{qTsP} packet
40748 These packets request data about tracepoints that are being used by
40749 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40750 of data, and multiple @code{qTsP} to get additional pieces. Replies
40751 to these packets generally take the form of the @code{QTDP} packets
40752 that define tracepoints. (FIXME add detailed syntax)
40755 @cindex @samp{qTfV} packet
40757 @cindex @samp{qTsV} packet
40758 These packets request data about trace state variables that are on the
40759 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40760 and multiple @code{qTsV} to get additional variables. Replies to
40761 these packets follow the syntax of the @code{QTDV} packets that define
40762 trace state variables.
40768 @cindex @samp{qTfSTM} packet
40769 @cindex @samp{qTsSTM} packet
40770 These packets request data about static tracepoint markers that exist
40771 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40772 first piece of data, and multiple @code{qTsSTM} to get additional
40773 pieces. Replies to these packets take the following form:
40777 @item m @var{address}:@var{id}:@var{extra}
40779 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40780 a comma-separated list of markers
40782 (lower case letter @samp{L}) denotes end of list.
40784 An error occurred. @var{nn} are hex digits.
40786 An empty reply indicates that the request is not supported by the
40790 @var{address} is encoded in hex.
40791 @var{id} and @var{extra} are strings encoded in hex.
40793 In response to each query, the target will reply with a list of one or
40794 more markers, separated by commas. @value{GDBN} will respond to each
40795 reply with a request for more markers (using the @samp{qs} form of the
40796 query), until the target responds with @samp{l} (lower-case ell, for
40799 @item qTSTMat:@var{address}
40801 @cindex @samp{qTSTMat} packet
40802 This packets requests data about static tracepoint markers in the
40803 target program at @var{address}. Replies to this packet follow the
40804 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40805 tracepoint markers.
40807 @item QTSave:@var{filename}
40808 @cindex @samp{QTSave} packet
40809 This packet directs the target to save trace data to the file name
40810 @var{filename} in the target's filesystem. @var{filename} is encoded
40811 as a hex string; the interpretation of the file name (relative vs
40812 absolute, wild cards, etc) is up to the target.
40814 @item qTBuffer:@var{offset},@var{len}
40815 @cindex @samp{qTBuffer} packet
40816 Return up to @var{len} bytes of the current contents of trace buffer,
40817 starting at @var{offset}. The trace buffer is treated as if it were
40818 a contiguous collection of traceframes, as per the trace file format.
40819 The reply consists as many hex-encoded bytes as the target can deliver
40820 in a packet; it is not an error to return fewer than were asked for.
40821 A reply consisting of just @code{l} indicates that no bytes are
40824 @item QTBuffer:circular:@var{value}
40825 This packet directs the target to use a circular trace buffer if
40826 @var{value} is 1, or a linear buffer if the value is 0.
40828 @item QTBuffer:size:@var{size}
40829 @anchor{QTBuffer-size}
40830 @cindex @samp{QTBuffer size} packet
40831 This packet directs the target to make the trace buffer be of size
40832 @var{size} if possible. A value of @code{-1} tells the target to
40833 use whatever size it prefers.
40835 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40836 @cindex @samp{QTNotes} packet
40837 This packet adds optional textual notes to the trace run. Allowable
40838 types include @code{user}, @code{notes}, and @code{tstop}, the
40839 @var{text} fields are arbitrary strings, hex-encoded.
40843 @subsection Relocate instruction reply packet
40844 When installing fast tracepoints in memory, the target may need to
40845 relocate the instruction currently at the tracepoint address to a
40846 different address in memory. For most instructions, a simple copy is
40847 enough, but, for example, call instructions that implicitly push the
40848 return address on the stack, and relative branches or other
40849 PC-relative instructions require offset adjustment, so that the effect
40850 of executing the instruction at a different address is the same as if
40851 it had executed in the original location.
40853 In response to several of the tracepoint packets, the target may also
40854 respond with a number of intermediate @samp{qRelocInsn} request
40855 packets before the final result packet, to have @value{GDBN} handle
40856 this relocation operation. If a packet supports this mechanism, its
40857 documentation will explicitly say so. See for example the above
40858 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40859 format of the request is:
40862 @item qRelocInsn:@var{from};@var{to}
40864 This requests @value{GDBN} to copy instruction at address @var{from}
40865 to address @var{to}, possibly adjusted so that executing the
40866 instruction at @var{to} has the same effect as executing it at
40867 @var{from}. @value{GDBN} writes the adjusted instruction to target
40868 memory starting at @var{to}.
40873 @item qRelocInsn:@var{adjusted_size}
40874 Informs the stub the relocation is complete. @var{adjusted_size} is
40875 the length in bytes of resulting relocated instruction sequence.
40877 A badly formed request was detected, or an error was encountered while
40878 relocating the instruction.
40881 @node Host I/O Packets
40882 @section Host I/O Packets
40883 @cindex Host I/O, remote protocol
40884 @cindex file transfer, remote protocol
40886 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40887 operations on the far side of a remote link. For example, Host I/O is
40888 used to upload and download files to a remote target with its own
40889 filesystem. Host I/O uses the same constant values and data structure
40890 layout as the target-initiated File-I/O protocol. However, the
40891 Host I/O packets are structured differently. The target-initiated
40892 protocol relies on target memory to store parameters and buffers.
40893 Host I/O requests are initiated by @value{GDBN}, and the
40894 target's memory is not involved. @xref{File-I/O Remote Protocol
40895 Extension}, for more details on the target-initiated protocol.
40897 The Host I/O request packets all encode a single operation along with
40898 its arguments. They have this format:
40902 @item vFile:@var{operation}: @var{parameter}@dots{}
40903 @var{operation} is the name of the particular request; the target
40904 should compare the entire packet name up to the second colon when checking
40905 for a supported operation. The format of @var{parameter} depends on
40906 the operation. Numbers are always passed in hexadecimal. Negative
40907 numbers have an explicit minus sign (i.e.@: two's complement is not
40908 used). Strings (e.g.@: filenames) are encoded as a series of
40909 hexadecimal bytes. The last argument to a system call may be a
40910 buffer of escaped binary data (@pxref{Binary Data}).
40914 The valid responses to Host I/O packets are:
40918 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40919 @var{result} is the integer value returned by this operation, usually
40920 non-negative for success and -1 for errors. If an error has occured,
40921 @var{errno} will be included in the result. @var{errno} will have a
40922 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40923 operations which return data, @var{attachment} supplies the data as a
40924 binary buffer. Binary buffers in response packets are escaped in the
40925 normal way (@pxref{Binary Data}). See the individual packet
40926 documentation for the interpretation of @var{result} and
40930 An empty response indicates that this operation is not recognized.
40934 These are the supported Host I/O operations:
40937 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40938 Open a file at @var{pathname} and return a file descriptor for it, or
40939 return -1 if an error occurs. @var{pathname} is a string,
40940 @var{flags} is an integer indicating a mask of open flags
40941 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40942 of mode bits to use if the file is created (@pxref{mode_t Values}).
40943 @xref{open}, for details of the open flags and mode values.
40945 @item vFile:close: @var{fd}
40946 Close the open file corresponding to @var{fd} and return 0, or
40947 -1 if an error occurs.
40949 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40950 Read data from the open file corresponding to @var{fd}. Up to
40951 @var{count} bytes will be read from the file, starting at @var{offset}
40952 relative to the start of the file. The target may read fewer bytes;
40953 common reasons include packet size limits and an end-of-file
40954 condition. The number of bytes read is returned. Zero should only be
40955 returned for a successful read at the end of the file, or if
40956 @var{count} was zero.
40958 The data read should be returned as a binary attachment on success.
40959 If zero bytes were read, the response should include an empty binary
40960 attachment (i.e.@: a trailing semicolon). The return value is the
40961 number of target bytes read; the binary attachment may be longer if
40962 some characters were escaped.
40964 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40965 Write @var{data} (a binary buffer) to the open file corresponding
40966 to @var{fd}. Start the write at @var{offset} from the start of the
40967 file. Unlike many @code{write} system calls, there is no
40968 separate @var{count} argument; the length of @var{data} in the
40969 packet is used. @samp{vFile:write} returns the number of bytes written,
40970 which may be shorter than the length of @var{data}, or -1 if an
40973 @item vFile:unlink: @var{pathname}
40974 Delete the file at @var{pathname} on the target. Return 0,
40975 or -1 if an error occurs. @var{pathname} is a string.
40977 @item vFile:readlink: @var{filename}
40978 Read value of symbolic link @var{filename} on the target. Return
40979 the number of bytes read, or -1 if an error occurs.
40981 The data read should be returned as a binary attachment on success.
40982 If zero bytes were read, the response should include an empty binary
40983 attachment (i.e.@: a trailing semicolon). The return value is the
40984 number of target bytes read; the binary attachment may be longer if
40985 some characters were escaped.
40990 @section Interrupts
40991 @cindex interrupts (remote protocol)
40993 When a program on the remote target is running, @value{GDBN} may
40994 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40995 a @code{BREAK} followed by @code{g},
40996 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40998 The precise meaning of @code{BREAK} is defined by the transport
40999 mechanism and may, in fact, be undefined. @value{GDBN} does not
41000 currently define a @code{BREAK} mechanism for any of the network
41001 interfaces except for TCP, in which case @value{GDBN} sends the
41002 @code{telnet} BREAK sequence.
41004 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
41005 transport mechanisms. It is represented by sending the single byte
41006 @code{0x03} without any of the usual packet overhead described in
41007 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
41008 transmitted as part of a packet, it is considered to be packet data
41009 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
41010 (@pxref{X packet}), used for binary downloads, may include an unescaped
41011 @code{0x03} as part of its packet.
41013 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
41014 When Linux kernel receives this sequence from serial port,
41015 it stops execution and connects to gdb.
41017 Stubs are not required to recognize these interrupt mechanisms and the
41018 precise meaning associated with receipt of the interrupt is
41019 implementation defined. If the target supports debugging of multiple
41020 threads and/or processes, it should attempt to interrupt all
41021 currently-executing threads and processes.
41022 If the stub is successful at interrupting the
41023 running program, it should send one of the stop
41024 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
41025 of successfully stopping the program in all-stop mode, and a stop reply
41026 for each stopped thread in non-stop mode.
41027 Interrupts received while the
41028 program is stopped are discarded.
41030 @node Notification Packets
41031 @section Notification Packets
41032 @cindex notification packets
41033 @cindex packets, notification
41035 The @value{GDBN} remote serial protocol includes @dfn{notifications},
41036 packets that require no acknowledgment. Both the GDB and the stub
41037 may send notifications (although the only notifications defined at
41038 present are sent by the stub). Notifications carry information
41039 without incurring the round-trip latency of an acknowledgment, and so
41040 are useful for low-impact communications where occasional packet loss
41043 A notification packet has the form @samp{% @var{data} #
41044 @var{checksum}}, where @var{data} is the content of the notification,
41045 and @var{checksum} is a checksum of @var{data}, computed and formatted
41046 as for ordinary @value{GDBN} packets. A notification's @var{data}
41047 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
41048 receiving a notification, the recipient sends no @samp{+} or @samp{-}
41049 to acknowledge the notification's receipt or to report its corruption.
41051 Every notification's @var{data} begins with a name, which contains no
41052 colon characters, followed by a colon character.
41054 Recipients should silently ignore corrupted notifications and
41055 notifications they do not understand. Recipients should restart
41056 timeout periods on receipt of a well-formed notification, whether or
41057 not they understand it.
41059 Senders should only send the notifications described here when this
41060 protocol description specifies that they are permitted. In the
41061 future, we may extend the protocol to permit existing notifications in
41062 new contexts; this rule helps older senders avoid confusing newer
41065 (Older versions of @value{GDBN} ignore bytes received until they see
41066 the @samp{$} byte that begins an ordinary packet, so new stubs may
41067 transmit notifications without fear of confusing older clients. There
41068 are no notifications defined for @value{GDBN} to send at the moment, but we
41069 assume that most older stubs would ignore them, as well.)
41071 Each notification is comprised of three parts:
41073 @item @var{name}:@var{event}
41074 The notification packet is sent by the side that initiates the
41075 exchange (currently, only the stub does that), with @var{event}
41076 carrying the specific information about the notification.
41077 @var{name} is the name of the notification.
41079 The acknowledge sent by the other side, usually @value{GDBN}, to
41080 acknowledge the exchange and request the event.
41083 The purpose of an asynchronous notification mechanism is to report to
41084 @value{GDBN} that something interesting happened in the remote stub.
41086 The remote stub may send notification @var{name}:@var{event}
41087 at any time, but @value{GDBN} acknowledges the notification when
41088 appropriate. The notification event is pending before @value{GDBN}
41089 acknowledges. Only one notification at a time may be pending; if
41090 additional events occur before @value{GDBN} has acknowledged the
41091 previous notification, they must be queued by the stub for later
41092 synchronous transmission in response to @var{ack} packets from
41093 @value{GDBN}. Because the notification mechanism is unreliable,
41094 the stub is permitted to resend a notification if it believes
41095 @value{GDBN} may not have received it.
41097 Specifically, notifications may appear when @value{GDBN} is not
41098 otherwise reading input from the stub, or when @value{GDBN} is
41099 expecting to read a normal synchronous response or a
41100 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
41101 Notification packets are distinct from any other communication from
41102 the stub so there is no ambiguity.
41104 After receiving a notification, @value{GDBN} shall acknowledge it by
41105 sending a @var{ack} packet as a regular, synchronous request to the
41106 stub. Such acknowledgment is not required to happen immediately, as
41107 @value{GDBN} is permitted to send other, unrelated packets to the
41108 stub first, which the stub should process normally.
41110 Upon receiving a @var{ack} packet, if the stub has other queued
41111 events to report to @value{GDBN}, it shall respond by sending a
41112 normal @var{event}. @value{GDBN} shall then send another @var{ack}
41113 packet to solicit further responses; again, it is permitted to send
41114 other, unrelated packets as well which the stub should process
41117 If the stub receives a @var{ack} packet and there are no additional
41118 @var{event} to report, the stub shall return an @samp{OK} response.
41119 At this point, @value{GDBN} has finished processing a notification
41120 and the stub has completed sending any queued events. @value{GDBN}
41121 won't accept any new notifications until the final @samp{OK} is
41122 received . If further notification events occur, the stub shall send
41123 a new notification, @value{GDBN} shall accept the notification, and
41124 the process shall be repeated.
41126 The process of asynchronous notification can be illustrated by the
41129 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
41132 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
41134 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
41139 The following notifications are defined:
41140 @multitable @columnfractions 0.12 0.12 0.38 0.38
41149 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
41150 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
41151 for information on how these notifications are acknowledged by
41153 @tab Report an asynchronous stop event in non-stop mode.
41157 @node Remote Non-Stop
41158 @section Remote Protocol Support for Non-Stop Mode
41160 @value{GDBN}'s remote protocol supports non-stop debugging of
41161 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
41162 supports non-stop mode, it should report that to @value{GDBN} by including
41163 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
41165 @value{GDBN} typically sends a @samp{QNonStop} packet only when
41166 establishing a new connection with the stub. Entering non-stop mode
41167 does not alter the state of any currently-running threads, but targets
41168 must stop all threads in any already-attached processes when entering
41169 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
41170 probe the target state after a mode change.
41172 In non-stop mode, when an attached process encounters an event that
41173 would otherwise be reported with a stop reply, it uses the
41174 asynchronous notification mechanism (@pxref{Notification Packets}) to
41175 inform @value{GDBN}. In contrast to all-stop mode, where all threads
41176 in all processes are stopped when a stop reply is sent, in non-stop
41177 mode only the thread reporting the stop event is stopped. That is,
41178 when reporting a @samp{S} or @samp{T} response to indicate completion
41179 of a step operation, hitting a breakpoint, or a fault, only the
41180 affected thread is stopped; any other still-running threads continue
41181 to run. When reporting a @samp{W} or @samp{X} response, all running
41182 threads belonging to other attached processes continue to run.
41184 In non-stop mode, the target shall respond to the @samp{?} packet as
41185 follows. First, any incomplete stop reply notification/@samp{vStopped}
41186 sequence in progress is abandoned. The target must begin a new
41187 sequence reporting stop events for all stopped threads, whether or not
41188 it has previously reported those events to @value{GDBN}. The first
41189 stop reply is sent as a synchronous reply to the @samp{?} packet, and
41190 subsequent stop replies are sent as responses to @samp{vStopped} packets
41191 using the mechanism described above. The target must not send
41192 asynchronous stop reply notifications until the sequence is complete.
41193 If all threads are running when the target receives the @samp{?} packet,
41194 or if the target is not attached to any process, it shall respond
41197 @node Packet Acknowledgment
41198 @section Packet Acknowledgment
41200 @cindex acknowledgment, for @value{GDBN} remote
41201 @cindex packet acknowledgment, for @value{GDBN} remote
41202 By default, when either the host or the target machine receives a packet,
41203 the first response expected is an acknowledgment: either @samp{+} (to indicate
41204 the package was received correctly) or @samp{-} (to request retransmission).
41205 This mechanism allows the @value{GDBN} remote protocol to operate over
41206 unreliable transport mechanisms, such as a serial line.
41208 In cases where the transport mechanism is itself reliable (such as a pipe or
41209 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
41210 It may be desirable to disable them in that case to reduce communication
41211 overhead, or for other reasons. This can be accomplished by means of the
41212 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
41214 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
41215 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
41216 and response format still includes the normal checksum, as described in
41217 @ref{Overview}, but the checksum may be ignored by the receiver.
41219 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
41220 no-acknowledgment mode, it should report that to @value{GDBN}
41221 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
41222 @pxref{qSupported}.
41223 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
41224 disabled via the @code{set remote noack-packet off} command
41225 (@pxref{Remote Configuration}),
41226 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
41227 Only then may the stub actually turn off packet acknowledgments.
41228 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
41229 response, which can be safely ignored by the stub.
41231 Note that @code{set remote noack-packet} command only affects negotiation
41232 between @value{GDBN} and the stub when subsequent connections are made;
41233 it does not affect the protocol acknowledgment state for any current
41235 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
41236 new connection is established,
41237 there is also no protocol request to re-enable the acknowledgments
41238 for the current connection, once disabled.
41243 Example sequence of a target being re-started. Notice how the restart
41244 does not get any direct output:
41249 @emph{target restarts}
41252 <- @code{T001:1234123412341234}
41256 Example sequence of a target being stepped by a single instruction:
41259 -> @code{G1445@dots{}}
41264 <- @code{T001:1234123412341234}
41268 <- @code{1455@dots{}}
41272 @node File-I/O Remote Protocol Extension
41273 @section File-I/O Remote Protocol Extension
41274 @cindex File-I/O remote protocol extension
41277 * File-I/O Overview::
41278 * Protocol Basics::
41279 * The F Request Packet::
41280 * The F Reply Packet::
41281 * The Ctrl-C Message::
41283 * List of Supported Calls::
41284 * Protocol-specific Representation of Datatypes::
41286 * File-I/O Examples::
41289 @node File-I/O Overview
41290 @subsection File-I/O Overview
41291 @cindex file-i/o overview
41293 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
41294 target to use the host's file system and console I/O to perform various
41295 system calls. System calls on the target system are translated into a
41296 remote protocol packet to the host system, which then performs the needed
41297 actions and returns a response packet to the target system.
41298 This simulates file system operations even on targets that lack file systems.
41300 The protocol is defined to be independent of both the host and target systems.
41301 It uses its own internal representation of datatypes and values. Both
41302 @value{GDBN} and the target's @value{GDBN} stub are responsible for
41303 translating the system-dependent value representations into the internal
41304 protocol representations when data is transmitted.
41306 The communication is synchronous. A system call is possible only when
41307 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
41308 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
41309 the target is stopped to allow deterministic access to the target's
41310 memory. Therefore File-I/O is not interruptible by target signals. On
41311 the other hand, it is possible to interrupt File-I/O by a user interrupt
41312 (@samp{Ctrl-C}) within @value{GDBN}.
41314 The target's request to perform a host system call does not finish
41315 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
41316 after finishing the system call, the target returns to continuing the
41317 previous activity (continue, step). No additional continue or step
41318 request from @value{GDBN} is required.
41321 (@value{GDBP}) continue
41322 <- target requests 'system call X'
41323 target is stopped, @value{GDBN} executes system call
41324 -> @value{GDBN} returns result
41325 ... target continues, @value{GDBN} returns to wait for the target
41326 <- target hits breakpoint and sends a Txx packet
41329 The protocol only supports I/O on the console and to regular files on
41330 the host file system. Character or block special devices, pipes,
41331 named pipes, sockets or any other communication method on the host
41332 system are not supported by this protocol.
41334 File I/O is not supported in non-stop mode.
41336 @node Protocol Basics
41337 @subsection Protocol Basics
41338 @cindex protocol basics, file-i/o
41340 The File-I/O protocol uses the @code{F} packet as the request as well
41341 as reply packet. Since a File-I/O system call can only occur when
41342 @value{GDBN} is waiting for a response from the continuing or stepping target,
41343 the File-I/O request is a reply that @value{GDBN} has to expect as a result
41344 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
41345 This @code{F} packet contains all information needed to allow @value{GDBN}
41346 to call the appropriate host system call:
41350 A unique identifier for the requested system call.
41353 All parameters to the system call. Pointers are given as addresses
41354 in the target memory address space. Pointers to strings are given as
41355 pointer/length pair. Numerical values are given as they are.
41356 Numerical control flags are given in a protocol-specific representation.
41360 At this point, @value{GDBN} has to perform the following actions.
41364 If the parameters include pointer values to data needed as input to a
41365 system call, @value{GDBN} requests this data from the target with a
41366 standard @code{m} packet request. This additional communication has to be
41367 expected by the target implementation and is handled as any other @code{m}
41371 @value{GDBN} translates all value from protocol representation to host
41372 representation as needed. Datatypes are coerced into the host types.
41375 @value{GDBN} calls the system call.
41378 It then coerces datatypes back to protocol representation.
41381 If the system call is expected to return data in buffer space specified
41382 by pointer parameters to the call, the data is transmitted to the
41383 target using a @code{M} or @code{X} packet. This packet has to be expected
41384 by the target implementation and is handled as any other @code{M} or @code{X}
41389 Eventually @value{GDBN} replies with another @code{F} packet which contains all
41390 necessary information for the target to continue. This at least contains
41397 @code{errno}, if has been changed by the system call.
41404 After having done the needed type and value coercion, the target continues
41405 the latest continue or step action.
41407 @node The F Request Packet
41408 @subsection The @code{F} Request Packet
41409 @cindex file-i/o request packet
41410 @cindex @code{F} request packet
41412 The @code{F} request packet has the following format:
41415 @item F@var{call-id},@var{parameter@dots{}}
41417 @var{call-id} is the identifier to indicate the host system call to be called.
41418 This is just the name of the function.
41420 @var{parameter@dots{}} are the parameters to the system call.
41421 Parameters are hexadecimal integer values, either the actual values in case
41422 of scalar datatypes, pointers to target buffer space in case of compound
41423 datatypes and unspecified memory areas, or pointer/length pairs in case
41424 of string parameters. These are appended to the @var{call-id} as a
41425 comma-delimited list. All values are transmitted in ASCII
41426 string representation, pointer/length pairs separated by a slash.
41432 @node The F Reply Packet
41433 @subsection The @code{F} Reply Packet
41434 @cindex file-i/o reply packet
41435 @cindex @code{F} reply packet
41437 The @code{F} reply packet has the following format:
41441 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
41443 @var{retcode} is the return code of the system call as hexadecimal value.
41445 @var{errno} is the @code{errno} set by the call, in protocol-specific
41447 This parameter can be omitted if the call was successful.
41449 @var{Ctrl-C flag} is only sent if the user requested a break. In this
41450 case, @var{errno} must be sent as well, even if the call was successful.
41451 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
41458 or, if the call was interrupted before the host call has been performed:
41465 assuming 4 is the protocol-specific representation of @code{EINTR}.
41470 @node The Ctrl-C Message
41471 @subsection The @samp{Ctrl-C} Message
41472 @cindex ctrl-c message, in file-i/o protocol
41474 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
41475 reply packet (@pxref{The F Reply Packet}),
41476 the target should behave as if it had
41477 gotten a break message. The meaning for the target is ``system call
41478 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
41479 (as with a break message) and return to @value{GDBN} with a @code{T02}
41482 It's important for the target to know in which
41483 state the system call was interrupted. There are two possible cases:
41487 The system call hasn't been performed on the host yet.
41490 The system call on the host has been finished.
41494 These two states can be distinguished by the target by the value of the
41495 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
41496 call hasn't been performed. This is equivalent to the @code{EINTR} handling
41497 on POSIX systems. In any other case, the target may presume that the
41498 system call has been finished --- successfully or not --- and should behave
41499 as if the break message arrived right after the system call.
41501 @value{GDBN} must behave reliably. If the system call has not been called
41502 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
41503 @code{errno} in the packet. If the system call on the host has been finished
41504 before the user requests a break, the full action must be finished by
41505 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
41506 The @code{F} packet may only be sent when either nothing has happened
41507 or the full action has been completed.
41510 @subsection Console I/O
41511 @cindex console i/o as part of file-i/o
41513 By default and if not explicitly closed by the target system, the file
41514 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
41515 on the @value{GDBN} console is handled as any other file output operation
41516 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
41517 by @value{GDBN} so that after the target read request from file descriptor
41518 0 all following typing is buffered until either one of the following
41523 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
41525 system call is treated as finished.
41528 The user presses @key{RET}. This is treated as end of input with a trailing
41532 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
41533 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
41537 If the user has typed more characters than fit in the buffer given to
41538 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
41539 either another @code{read(0, @dots{})} is requested by the target, or debugging
41540 is stopped at the user's request.
41543 @node List of Supported Calls
41544 @subsection List of Supported Calls
41545 @cindex list of supported file-i/o calls
41562 @unnumberedsubsubsec open
41563 @cindex open, file-i/o system call
41568 int open(const char *pathname, int flags);
41569 int open(const char *pathname, int flags, mode_t mode);
41573 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
41576 @var{flags} is the bitwise @code{OR} of the following values:
41580 If the file does not exist it will be created. The host
41581 rules apply as far as file ownership and time stamps
41585 When used with @code{O_CREAT}, if the file already exists it is
41586 an error and open() fails.
41589 If the file already exists and the open mode allows
41590 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
41591 truncated to zero length.
41594 The file is opened in append mode.
41597 The file is opened for reading only.
41600 The file is opened for writing only.
41603 The file is opened for reading and writing.
41607 Other bits are silently ignored.
41611 @var{mode} is the bitwise @code{OR} of the following values:
41615 User has read permission.
41618 User has write permission.
41621 Group has read permission.
41624 Group has write permission.
41627 Others have read permission.
41630 Others have write permission.
41634 Other bits are silently ignored.
41637 @item Return value:
41638 @code{open} returns the new file descriptor or -1 if an error
41645 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
41648 @var{pathname} refers to a directory.
41651 The requested access is not allowed.
41654 @var{pathname} was too long.
41657 A directory component in @var{pathname} does not exist.
41660 @var{pathname} refers to a device, pipe, named pipe or socket.
41663 @var{pathname} refers to a file on a read-only filesystem and
41664 write access was requested.
41667 @var{pathname} is an invalid pointer value.
41670 No space on device to create the file.
41673 The process already has the maximum number of files open.
41676 The limit on the total number of files open on the system
41680 The call was interrupted by the user.
41686 @unnumberedsubsubsec close
41687 @cindex close, file-i/o system call
41696 @samp{Fclose,@var{fd}}
41698 @item Return value:
41699 @code{close} returns zero on success, or -1 if an error occurred.
41705 @var{fd} isn't a valid open file descriptor.
41708 The call was interrupted by the user.
41714 @unnumberedsubsubsec read
41715 @cindex read, file-i/o system call
41720 int read(int fd, void *buf, unsigned int count);
41724 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41726 @item Return value:
41727 On success, the number of bytes read is returned.
41728 Zero indicates end of file. If count is zero, read
41729 returns zero as well. On error, -1 is returned.
41735 @var{fd} is not a valid file descriptor or is not open for
41739 @var{bufptr} is an invalid pointer value.
41742 The call was interrupted by the user.
41748 @unnumberedsubsubsec write
41749 @cindex write, file-i/o system call
41754 int write(int fd, const void *buf, unsigned int count);
41758 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41760 @item Return value:
41761 On success, the number of bytes written are returned.
41762 Zero indicates nothing was written. On error, -1
41769 @var{fd} is not a valid file descriptor or is not open for
41773 @var{bufptr} is an invalid pointer value.
41776 An attempt was made to write a file that exceeds the
41777 host-specific maximum file size allowed.
41780 No space on device to write the data.
41783 The call was interrupted by the user.
41789 @unnumberedsubsubsec lseek
41790 @cindex lseek, file-i/o system call
41795 long lseek (int fd, long offset, int flag);
41799 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41801 @var{flag} is one of:
41805 The offset is set to @var{offset} bytes.
41808 The offset is set to its current location plus @var{offset}
41812 The offset is set to the size of the file plus @var{offset}
41816 @item Return value:
41817 On success, the resulting unsigned offset in bytes from
41818 the beginning of the file is returned. Otherwise, a
41819 value of -1 is returned.
41825 @var{fd} is not a valid open file descriptor.
41828 @var{fd} is associated with the @value{GDBN} console.
41831 @var{flag} is not a proper value.
41834 The call was interrupted by the user.
41840 @unnumberedsubsubsec rename
41841 @cindex rename, file-i/o system call
41846 int rename(const char *oldpath, const char *newpath);
41850 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41852 @item Return value:
41853 On success, zero is returned. On error, -1 is returned.
41859 @var{newpath} is an existing directory, but @var{oldpath} is not a
41863 @var{newpath} is a non-empty directory.
41866 @var{oldpath} or @var{newpath} is a directory that is in use by some
41870 An attempt was made to make a directory a subdirectory
41874 A component used as a directory in @var{oldpath} or new
41875 path is not a directory. Or @var{oldpath} is a directory
41876 and @var{newpath} exists but is not a directory.
41879 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41882 No access to the file or the path of the file.
41886 @var{oldpath} or @var{newpath} was too long.
41889 A directory component in @var{oldpath} or @var{newpath} does not exist.
41892 The file is on a read-only filesystem.
41895 The device containing the file has no room for the new
41899 The call was interrupted by the user.
41905 @unnumberedsubsubsec unlink
41906 @cindex unlink, file-i/o system call
41911 int unlink(const char *pathname);
41915 @samp{Funlink,@var{pathnameptr}/@var{len}}
41917 @item Return value:
41918 On success, zero is returned. On error, -1 is returned.
41924 No access to the file or the path of the file.
41927 The system does not allow unlinking of directories.
41930 The file @var{pathname} cannot be unlinked because it's
41931 being used by another process.
41934 @var{pathnameptr} is an invalid pointer value.
41937 @var{pathname} was too long.
41940 A directory component in @var{pathname} does not exist.
41943 A component of the path is not a directory.
41946 The file is on a read-only filesystem.
41949 The call was interrupted by the user.
41955 @unnumberedsubsubsec stat/fstat
41956 @cindex fstat, file-i/o system call
41957 @cindex stat, file-i/o system call
41962 int stat(const char *pathname, struct stat *buf);
41963 int fstat(int fd, struct stat *buf);
41967 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41968 @samp{Ffstat,@var{fd},@var{bufptr}}
41970 @item Return value:
41971 On success, zero is returned. On error, -1 is returned.
41977 @var{fd} is not a valid open file.
41980 A directory component in @var{pathname} does not exist or the
41981 path is an empty string.
41984 A component of the path is not a directory.
41987 @var{pathnameptr} is an invalid pointer value.
41990 No access to the file or the path of the file.
41993 @var{pathname} was too long.
41996 The call was interrupted by the user.
42002 @unnumberedsubsubsec gettimeofday
42003 @cindex gettimeofday, file-i/o system call
42008 int gettimeofday(struct timeval *tv, void *tz);
42012 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
42014 @item Return value:
42015 On success, 0 is returned, -1 otherwise.
42021 @var{tz} is a non-NULL pointer.
42024 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
42030 @unnumberedsubsubsec isatty
42031 @cindex isatty, file-i/o system call
42036 int isatty(int fd);
42040 @samp{Fisatty,@var{fd}}
42042 @item Return value:
42043 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
42049 The call was interrupted by the user.
42054 Note that the @code{isatty} call is treated as a special case: it returns
42055 1 to the target if the file descriptor is attached
42056 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
42057 would require implementing @code{ioctl} and would be more complex than
42062 @unnumberedsubsubsec system
42063 @cindex system, file-i/o system call
42068 int system(const char *command);
42072 @samp{Fsystem,@var{commandptr}/@var{len}}
42074 @item Return value:
42075 If @var{len} is zero, the return value indicates whether a shell is
42076 available. A zero return value indicates a shell is not available.
42077 For non-zero @var{len}, the value returned is -1 on error and the
42078 return status of the command otherwise. Only the exit status of the
42079 command is returned, which is extracted from the host's @code{system}
42080 return value by calling @code{WEXITSTATUS(retval)}. In case
42081 @file{/bin/sh} could not be executed, 127 is returned.
42087 The call was interrupted by the user.
42092 @value{GDBN} takes over the full task of calling the necessary host calls
42093 to perform the @code{system} call. The return value of @code{system} on
42094 the host is simplified before it's returned
42095 to the target. Any termination signal information from the child process
42096 is discarded, and the return value consists
42097 entirely of the exit status of the called command.
42099 Due to security concerns, the @code{system} call is by default refused
42100 by @value{GDBN}. The user has to allow this call explicitly with the
42101 @code{set remote system-call-allowed 1} command.
42104 @item set remote system-call-allowed
42105 @kindex set remote system-call-allowed
42106 Control whether to allow the @code{system} calls in the File I/O
42107 protocol for the remote target. The default is zero (disabled).
42109 @item show remote system-call-allowed
42110 @kindex show remote system-call-allowed
42111 Show whether the @code{system} calls are allowed in the File I/O
42115 @node Protocol-specific Representation of Datatypes
42116 @subsection Protocol-specific Representation of Datatypes
42117 @cindex protocol-specific representation of datatypes, in file-i/o protocol
42120 * Integral Datatypes::
42122 * Memory Transfer::
42127 @node Integral Datatypes
42128 @unnumberedsubsubsec Integral Datatypes
42129 @cindex integral datatypes, in file-i/o protocol
42131 The integral datatypes used in the system calls are @code{int},
42132 @code{unsigned int}, @code{long}, @code{unsigned long},
42133 @code{mode_t}, and @code{time_t}.
42135 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
42136 implemented as 32 bit values in this protocol.
42138 @code{long} and @code{unsigned long} are implemented as 64 bit types.
42140 @xref{Limits}, for corresponding MIN and MAX values (similar to those
42141 in @file{limits.h}) to allow range checking on host and target.
42143 @code{time_t} datatypes are defined as seconds since the Epoch.
42145 All integral datatypes transferred as part of a memory read or write of a
42146 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
42149 @node Pointer Values
42150 @unnumberedsubsubsec Pointer Values
42151 @cindex pointer values, in file-i/o protocol
42153 Pointers to target data are transmitted as they are. An exception
42154 is made for pointers to buffers for which the length isn't
42155 transmitted as part of the function call, namely strings. Strings
42156 are transmitted as a pointer/length pair, both as hex values, e.g.@:
42163 which is a pointer to data of length 18 bytes at position 0x1aaf.
42164 The length is defined as the full string length in bytes, including
42165 the trailing null byte. For example, the string @code{"hello world"}
42166 at address 0x123456 is transmitted as
42172 @node Memory Transfer
42173 @unnumberedsubsubsec Memory Transfer
42174 @cindex memory transfer, in file-i/o protocol
42176 Structured data which is transferred using a memory read or write (for
42177 example, a @code{struct stat}) is expected to be in a protocol-specific format
42178 with all scalar multibyte datatypes being big endian. Translation to
42179 this representation needs to be done both by the target before the @code{F}
42180 packet is sent, and by @value{GDBN} before
42181 it transfers memory to the target. Transferred pointers to structured
42182 data should point to the already-coerced data at any time.
42186 @unnumberedsubsubsec struct stat
42187 @cindex struct stat, in file-i/o protocol
42189 The buffer of type @code{struct stat} used by the target and @value{GDBN}
42190 is defined as follows:
42194 unsigned int st_dev; /* device */
42195 unsigned int st_ino; /* inode */
42196 mode_t st_mode; /* protection */
42197 unsigned int st_nlink; /* number of hard links */
42198 unsigned int st_uid; /* user ID of owner */
42199 unsigned int st_gid; /* group ID of owner */
42200 unsigned int st_rdev; /* device type (if inode device) */
42201 unsigned long st_size; /* total size, in bytes */
42202 unsigned long st_blksize; /* blocksize for filesystem I/O */
42203 unsigned long st_blocks; /* number of blocks allocated */
42204 time_t st_atime; /* time of last access */
42205 time_t st_mtime; /* time of last modification */
42206 time_t st_ctime; /* time of last change */
42210 The integral datatypes conform to the definitions given in the
42211 appropriate section (see @ref{Integral Datatypes}, for details) so this
42212 structure is of size 64 bytes.
42214 The values of several fields have a restricted meaning and/or
42220 A value of 0 represents a file, 1 the console.
42223 No valid meaning for the target. Transmitted unchanged.
42226 Valid mode bits are described in @ref{Constants}. Any other
42227 bits have currently no meaning for the target.
42232 No valid meaning for the target. Transmitted unchanged.
42237 These values have a host and file system dependent
42238 accuracy. Especially on Windows hosts, the file system may not
42239 support exact timing values.
42242 The target gets a @code{struct stat} of the above representation and is
42243 responsible for coercing it to the target representation before
42246 Note that due to size differences between the host, target, and protocol
42247 representations of @code{struct stat} members, these members could eventually
42248 get truncated on the target.
42250 @node struct timeval
42251 @unnumberedsubsubsec struct timeval
42252 @cindex struct timeval, in file-i/o protocol
42254 The buffer of type @code{struct timeval} used by the File-I/O protocol
42255 is defined as follows:
42259 time_t tv_sec; /* second */
42260 long tv_usec; /* microsecond */
42264 The integral datatypes conform to the definitions given in the
42265 appropriate section (see @ref{Integral Datatypes}, for details) so this
42266 structure is of size 8 bytes.
42269 @subsection Constants
42270 @cindex constants, in file-i/o protocol
42272 The following values are used for the constants inside of the
42273 protocol. @value{GDBN} and target are responsible for translating these
42274 values before and after the call as needed.
42285 @unnumberedsubsubsec Open Flags
42286 @cindex open flags, in file-i/o protocol
42288 All values are given in hexadecimal representation.
42300 @node mode_t Values
42301 @unnumberedsubsubsec mode_t Values
42302 @cindex mode_t values, in file-i/o protocol
42304 All values are given in octal representation.
42321 @unnumberedsubsubsec Errno Values
42322 @cindex errno values, in file-i/o protocol
42324 All values are given in decimal representation.
42349 @code{EUNKNOWN} is used as a fallback error value if a host system returns
42350 any error value not in the list of supported error numbers.
42353 @unnumberedsubsubsec Lseek Flags
42354 @cindex lseek flags, in file-i/o protocol
42363 @unnumberedsubsubsec Limits
42364 @cindex limits, in file-i/o protocol
42366 All values are given in decimal representation.
42369 INT_MIN -2147483648
42371 UINT_MAX 4294967295
42372 LONG_MIN -9223372036854775808
42373 LONG_MAX 9223372036854775807
42374 ULONG_MAX 18446744073709551615
42377 @node File-I/O Examples
42378 @subsection File-I/O Examples
42379 @cindex file-i/o examples
42381 Example sequence of a write call, file descriptor 3, buffer is at target
42382 address 0x1234, 6 bytes should be written:
42385 <- @code{Fwrite,3,1234,6}
42386 @emph{request memory read from target}
42389 @emph{return "6 bytes written"}
42393 Example sequence of a read call, file descriptor 3, buffer is at target
42394 address 0x1234, 6 bytes should be read:
42397 <- @code{Fread,3,1234,6}
42398 @emph{request memory write to target}
42399 -> @code{X1234,6:XXXXXX}
42400 @emph{return "6 bytes read"}
42404 Example sequence of a read call, call fails on the host due to invalid
42405 file descriptor (@code{EBADF}):
42408 <- @code{Fread,3,1234,6}
42412 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
42416 <- @code{Fread,3,1234,6}
42421 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
42425 <- @code{Fread,3,1234,6}
42426 -> @code{X1234,6:XXXXXX}
42430 @node Library List Format
42431 @section Library List Format
42432 @cindex library list format, remote protocol
42434 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
42435 same process as your application to manage libraries. In this case,
42436 @value{GDBN} can use the loader's symbol table and normal memory
42437 operations to maintain a list of shared libraries. On other
42438 platforms, the operating system manages loaded libraries.
42439 @value{GDBN} can not retrieve the list of currently loaded libraries
42440 through memory operations, so it uses the @samp{qXfer:libraries:read}
42441 packet (@pxref{qXfer library list read}) instead. The remote stub
42442 queries the target's operating system and reports which libraries
42445 The @samp{qXfer:libraries:read} packet returns an XML document which
42446 lists loaded libraries and their offsets. Each library has an
42447 associated name and one or more segment or section base addresses,
42448 which report where the library was loaded in memory.
42450 For the common case of libraries that are fully linked binaries, the
42451 library should have a list of segments. If the target supports
42452 dynamic linking of a relocatable object file, its library XML element
42453 should instead include a list of allocated sections. The segment or
42454 section bases are start addresses, not relocation offsets; they do not
42455 depend on the library's link-time base addresses.
42457 @value{GDBN} must be linked with the Expat library to support XML
42458 library lists. @xref{Expat}.
42460 A simple memory map, with one loaded library relocated by a single
42461 offset, looks like this:
42465 <library name="/lib/libc.so.6">
42466 <segment address="0x10000000"/>
42471 Another simple memory map, with one loaded library with three
42472 allocated sections (.text, .data, .bss), looks like this:
42476 <library name="sharedlib.o">
42477 <section address="0x10000000"/>
42478 <section address="0x20000000"/>
42479 <section address="0x30000000"/>
42484 The format of a library list is described by this DTD:
42487 <!-- library-list: Root element with versioning -->
42488 <!ELEMENT library-list (library)*>
42489 <!ATTLIST library-list version CDATA #FIXED "1.0">
42490 <!ELEMENT library (segment*, section*)>
42491 <!ATTLIST library name CDATA #REQUIRED>
42492 <!ELEMENT segment EMPTY>
42493 <!ATTLIST segment address CDATA #REQUIRED>
42494 <!ELEMENT section EMPTY>
42495 <!ATTLIST section address CDATA #REQUIRED>
42498 In addition, segments and section descriptors cannot be mixed within a
42499 single library element, and you must supply at least one segment or
42500 section for each library.
42502 @node Library List Format for SVR4 Targets
42503 @section Library List Format for SVR4 Targets
42504 @cindex library list format, remote protocol
42506 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
42507 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
42508 shared libraries. Still a special library list provided by this packet is
42509 more efficient for the @value{GDBN} remote protocol.
42511 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
42512 loaded libraries and their SVR4 linker parameters. For each library on SVR4
42513 target, the following parameters are reported:
42517 @code{name}, the absolute file name from the @code{l_name} field of
42518 @code{struct link_map}.
42520 @code{lm} with address of @code{struct link_map} used for TLS
42521 (Thread Local Storage) access.
42523 @code{l_addr}, the displacement as read from the field @code{l_addr} of
42524 @code{struct link_map}. For prelinked libraries this is not an absolute
42525 memory address. It is a displacement of absolute memory address against
42526 address the file was prelinked to during the library load.
42528 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
42531 Additionally the single @code{main-lm} attribute specifies address of
42532 @code{struct link_map} used for the main executable. This parameter is used
42533 for TLS access and its presence is optional.
42535 @value{GDBN} must be linked with the Expat library to support XML
42536 SVR4 library lists. @xref{Expat}.
42538 A simple memory map, with two loaded libraries (which do not use prelink),
42542 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
42543 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
42545 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
42547 </library-list-svr>
42550 The format of an SVR4 library list is described by this DTD:
42553 <!-- library-list-svr4: Root element with versioning -->
42554 <!ELEMENT library-list-svr4 (library)*>
42555 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
42556 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
42557 <!ELEMENT library EMPTY>
42558 <!ATTLIST library name CDATA #REQUIRED>
42559 <!ATTLIST library lm CDATA #REQUIRED>
42560 <!ATTLIST library l_addr CDATA #REQUIRED>
42561 <!ATTLIST library l_ld CDATA #REQUIRED>
42564 @node Memory Map Format
42565 @section Memory Map Format
42566 @cindex memory map format
42568 To be able to write into flash memory, @value{GDBN} needs to obtain a
42569 memory map from the target. This section describes the format of the
42572 The memory map is obtained using the @samp{qXfer:memory-map:read}
42573 (@pxref{qXfer memory map read}) packet and is an XML document that
42574 lists memory regions.
42576 @value{GDBN} must be linked with the Expat library to support XML
42577 memory maps. @xref{Expat}.
42579 The top-level structure of the document is shown below:
42582 <?xml version="1.0"?>
42583 <!DOCTYPE memory-map
42584 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42585 "http://sourceware.org/gdb/gdb-memory-map.dtd">
42591 Each region can be either:
42596 A region of RAM starting at @var{addr} and extending for @var{length}
42600 <memory type="ram" start="@var{addr}" length="@var{length}"/>
42605 A region of read-only memory:
42608 <memory type="rom" start="@var{addr}" length="@var{length}"/>
42613 A region of flash memory, with erasure blocks @var{blocksize}
42617 <memory type="flash" start="@var{addr}" length="@var{length}">
42618 <property name="blocksize">@var{blocksize}</property>
42624 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
42625 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
42626 packets to write to addresses in such ranges.
42628 The formal DTD for memory map format is given below:
42631 <!-- ................................................... -->
42632 <!-- Memory Map XML DTD ................................ -->
42633 <!-- File: memory-map.dtd .............................. -->
42634 <!-- .................................... .............. -->
42635 <!-- memory-map.dtd -->
42636 <!-- memory-map: Root element with versioning -->
42637 <!ELEMENT memory-map (memory | property)>
42638 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
42639 <!ELEMENT memory (property)>
42640 <!-- memory: Specifies a memory region,
42641 and its type, or device. -->
42642 <!ATTLIST memory type CDATA #REQUIRED
42643 start CDATA #REQUIRED
42644 length CDATA #REQUIRED
42645 device CDATA #IMPLIED>
42646 <!-- property: Generic attribute tag -->
42647 <!ELEMENT property (#PCDATA | property)*>
42648 <!ATTLIST property name CDATA #REQUIRED>
42651 @node Thread List Format
42652 @section Thread List Format
42653 @cindex thread list format
42655 To efficiently update the list of threads and their attributes,
42656 @value{GDBN} issues the @samp{qXfer:threads:read} packet
42657 (@pxref{qXfer threads read}) and obtains the XML document with
42658 the following structure:
42661 <?xml version="1.0"?>
42663 <thread id="id" core="0">
42664 ... description ...
42669 Each @samp{thread} element must have the @samp{id} attribute that
42670 identifies the thread (@pxref{thread-id syntax}). The
42671 @samp{core} attribute, if present, specifies which processor core
42672 the thread was last executing on. The content of the of @samp{thread}
42673 element is interpreted as human-readable auxilliary information.
42675 @node Traceframe Info Format
42676 @section Traceframe Info Format
42677 @cindex traceframe info format
42679 To be able to know which objects in the inferior can be examined when
42680 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
42681 memory ranges, registers and trace state variables that have been
42682 collected in a traceframe.
42684 This list is obtained using the @samp{qXfer:traceframe-info:read}
42685 (@pxref{qXfer traceframe info read}) packet and is an XML document.
42687 @value{GDBN} must be linked with the Expat library to support XML
42688 traceframe info discovery. @xref{Expat}.
42690 The top-level structure of the document is shown below:
42693 <?xml version="1.0"?>
42694 <!DOCTYPE traceframe-info
42695 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
42696 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
42702 Each traceframe block can be either:
42707 A region of collected memory starting at @var{addr} and extending for
42708 @var{length} bytes from there:
42711 <memory start="@var{addr}" length="@var{length}"/>
42715 A block indicating trace state variable numbered @var{number} has been
42719 <tvar id="@var{number}"/>
42724 The formal DTD for the traceframe info format is given below:
42727 <!ELEMENT traceframe-info (memory | tvar)* >
42728 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42730 <!ELEMENT memory EMPTY>
42731 <!ATTLIST memory start CDATA #REQUIRED
42732 length CDATA #REQUIRED>
42734 <!ATTLIST tvar id CDATA #REQUIRED>
42737 @node Branch Trace Format
42738 @section Branch Trace Format
42739 @cindex branch trace format
42741 In order to display the branch trace of an inferior thread,
42742 @value{GDBN} needs to obtain the list of branches. This list is
42743 represented as list of sequential code blocks that are connected via
42744 branches. The code in each block has been executed sequentially.
42746 This list is obtained using the @samp{qXfer:btrace:read}
42747 (@pxref{qXfer btrace read}) packet and is an XML document.
42749 @value{GDBN} must be linked with the Expat library to support XML
42750 traceframe info discovery. @xref{Expat}.
42752 The top-level structure of the document is shown below:
42755 <?xml version="1.0"?>
42757 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42758 "http://sourceware.org/gdb/gdb-btrace.dtd">
42767 A block of sequentially executed instructions starting at @var{begin}
42768 and ending at @var{end}:
42771 <block begin="@var{begin}" end="@var{end}"/>
42776 The formal DTD for the branch trace format is given below:
42779 <!ELEMENT btrace (block)* >
42780 <!ATTLIST btrace version CDATA #FIXED "1.0">
42782 <!ELEMENT block EMPTY>
42783 <!ATTLIST block begin CDATA #REQUIRED
42784 end CDATA #REQUIRED>
42787 @include agentexpr.texi
42789 @node Target Descriptions
42790 @appendix Target Descriptions
42791 @cindex target descriptions
42793 One of the challenges of using @value{GDBN} to debug embedded systems
42794 is that there are so many minor variants of each processor
42795 architecture in use. It is common practice for vendors to start with
42796 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42797 and then make changes to adapt it to a particular market niche. Some
42798 architectures have hundreds of variants, available from dozens of
42799 vendors. This leads to a number of problems:
42803 With so many different customized processors, it is difficult for
42804 the @value{GDBN} maintainers to keep up with the changes.
42806 Since individual variants may have short lifetimes or limited
42807 audiences, it may not be worthwhile to carry information about every
42808 variant in the @value{GDBN} source tree.
42810 When @value{GDBN} does support the architecture of the embedded system
42811 at hand, the task of finding the correct architecture name to give the
42812 @command{set architecture} command can be error-prone.
42815 To address these problems, the @value{GDBN} remote protocol allows a
42816 target system to not only identify itself to @value{GDBN}, but to
42817 actually describe its own features. This lets @value{GDBN} support
42818 processor variants it has never seen before --- to the extent that the
42819 descriptions are accurate, and that @value{GDBN} understands them.
42821 @value{GDBN} must be linked with the Expat library to support XML
42822 target descriptions. @xref{Expat}.
42825 * Retrieving Descriptions:: How descriptions are fetched from a target.
42826 * Target Description Format:: The contents of a target description.
42827 * Predefined Target Types:: Standard types available for target
42829 * Standard Target Features:: Features @value{GDBN} knows about.
42832 @node Retrieving Descriptions
42833 @section Retrieving Descriptions
42835 Target descriptions can be read from the target automatically, or
42836 specified by the user manually. The default behavior is to read the
42837 description from the target. @value{GDBN} retrieves it via the remote
42838 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42839 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42840 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42841 XML document, of the form described in @ref{Target Description
42844 Alternatively, you can specify a file to read for the target description.
42845 If a file is set, the target will not be queried. The commands to
42846 specify a file are:
42849 @cindex set tdesc filename
42850 @item set tdesc filename @var{path}
42851 Read the target description from @var{path}.
42853 @cindex unset tdesc filename
42854 @item unset tdesc filename
42855 Do not read the XML target description from a file. @value{GDBN}
42856 will use the description supplied by the current target.
42858 @cindex show tdesc filename
42859 @item show tdesc filename
42860 Show the filename to read for a target description, if any.
42864 @node Target Description Format
42865 @section Target Description Format
42866 @cindex target descriptions, XML format
42868 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42869 document which complies with the Document Type Definition provided in
42870 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42871 means you can use generally available tools like @command{xmllint} to
42872 check that your feature descriptions are well-formed and valid.
42873 However, to help people unfamiliar with XML write descriptions for
42874 their targets, we also describe the grammar here.
42876 Target descriptions can identify the architecture of the remote target
42877 and (for some architectures) provide information about custom register
42878 sets. They can also identify the OS ABI of the remote target.
42879 @value{GDBN} can use this information to autoconfigure for your
42880 target, or to warn you if you connect to an unsupported target.
42882 Here is a simple target description:
42885 <target version="1.0">
42886 <architecture>i386:x86-64</architecture>
42891 This minimal description only says that the target uses
42892 the x86-64 architecture.
42894 A target description has the following overall form, with [ ] marking
42895 optional elements and @dots{} marking repeatable elements. The elements
42896 are explained further below.
42899 <?xml version="1.0"?>
42900 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42901 <target version="1.0">
42902 @r{[}@var{architecture}@r{]}
42903 @r{[}@var{osabi}@r{]}
42904 @r{[}@var{compatible}@r{]}
42905 @r{[}@var{feature}@dots{}@r{]}
42910 The description is generally insensitive to whitespace and line
42911 breaks, under the usual common-sense rules. The XML version
42912 declaration and document type declaration can generally be omitted
42913 (@value{GDBN} does not require them), but specifying them may be
42914 useful for XML validation tools. The @samp{version} attribute for
42915 @samp{<target>} may also be omitted, but we recommend
42916 including it; if future versions of @value{GDBN} use an incompatible
42917 revision of @file{gdb-target.dtd}, they will detect and report
42918 the version mismatch.
42920 @subsection Inclusion
42921 @cindex target descriptions, inclusion
42924 @cindex <xi:include>
42927 It can sometimes be valuable to split a target description up into
42928 several different annexes, either for organizational purposes, or to
42929 share files between different possible target descriptions. You can
42930 divide a description into multiple files by replacing any element of
42931 the target description with an inclusion directive of the form:
42934 <xi:include href="@var{document}"/>
42938 When @value{GDBN} encounters an element of this form, it will retrieve
42939 the named XML @var{document}, and replace the inclusion directive with
42940 the contents of that document. If the current description was read
42941 using @samp{qXfer}, then so will be the included document;
42942 @var{document} will be interpreted as the name of an annex. If the
42943 current description was read from a file, @value{GDBN} will look for
42944 @var{document} as a file in the same directory where it found the
42945 original description.
42947 @subsection Architecture
42948 @cindex <architecture>
42950 An @samp{<architecture>} element has this form:
42953 <architecture>@var{arch}</architecture>
42956 @var{arch} is one of the architectures from the set accepted by
42957 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42960 @cindex @code{<osabi>}
42962 This optional field was introduced in @value{GDBN} version 7.0.
42963 Previous versions of @value{GDBN} ignore it.
42965 An @samp{<osabi>} element has this form:
42968 <osabi>@var{abi-name}</osabi>
42971 @var{abi-name} is an OS ABI name from the same selection accepted by
42972 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42974 @subsection Compatible Architecture
42975 @cindex @code{<compatible>}
42977 This optional field was introduced in @value{GDBN} version 7.0.
42978 Previous versions of @value{GDBN} ignore it.
42980 A @samp{<compatible>} element has this form:
42983 <compatible>@var{arch}</compatible>
42986 @var{arch} is one of the architectures from the set accepted by
42987 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42989 A @samp{<compatible>} element is used to specify that the target
42990 is able to run binaries in some other than the main target architecture
42991 given by the @samp{<architecture>} element. For example, on the
42992 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42993 or @code{powerpc:common64}, but the system is able to run binaries
42994 in the @code{spu} architecture as well. The way to describe this
42995 capability with @samp{<compatible>} is as follows:
42998 <architecture>powerpc:common</architecture>
42999 <compatible>spu</compatible>
43002 @subsection Features
43005 Each @samp{<feature>} describes some logical portion of the target
43006 system. Features are currently used to describe available CPU
43007 registers and the types of their contents. A @samp{<feature>} element
43011 <feature name="@var{name}">
43012 @r{[}@var{type}@dots{}@r{]}
43018 Each feature's name should be unique within the description. The name
43019 of a feature does not matter unless @value{GDBN} has some special
43020 knowledge of the contents of that feature; if it does, the feature
43021 should have its standard name. @xref{Standard Target Features}.
43025 Any register's value is a collection of bits which @value{GDBN} must
43026 interpret. The default interpretation is a two's complement integer,
43027 but other types can be requested by name in the register description.
43028 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
43029 Target Types}), and the description can define additional composite types.
43031 Each type element must have an @samp{id} attribute, which gives
43032 a unique (within the containing @samp{<feature>}) name to the type.
43033 Types must be defined before they are used.
43036 Some targets offer vector registers, which can be treated as arrays
43037 of scalar elements. These types are written as @samp{<vector>} elements,
43038 specifying the array element type, @var{type}, and the number of elements,
43042 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
43046 If a register's value is usefully viewed in multiple ways, define it
43047 with a union type containing the useful representations. The
43048 @samp{<union>} element contains one or more @samp{<field>} elements,
43049 each of which has a @var{name} and a @var{type}:
43052 <union id="@var{id}">
43053 <field name="@var{name}" type="@var{type}"/>
43059 If a register's value is composed from several separate values, define
43060 it with a structure type. There are two forms of the @samp{<struct>}
43061 element; a @samp{<struct>} element must either contain only bitfields
43062 or contain no bitfields. If the structure contains only bitfields,
43063 its total size in bytes must be specified, each bitfield must have an
43064 explicit start and end, and bitfields are automatically assigned an
43065 integer type. The field's @var{start} should be less than or
43066 equal to its @var{end}, and zero represents the least significant bit.
43069 <struct id="@var{id}" size="@var{size}">
43070 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43075 If the structure contains no bitfields, then each field has an
43076 explicit type, and no implicit padding is added.
43079 <struct id="@var{id}">
43080 <field name="@var{name}" type="@var{type}"/>
43086 If a register's value is a series of single-bit flags, define it with
43087 a flags type. The @samp{<flags>} element has an explicit @var{size}
43088 and contains one or more @samp{<field>} elements. Each field has a
43089 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
43093 <flags id="@var{id}" size="@var{size}">
43094 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
43099 @subsection Registers
43102 Each register is represented as an element with this form:
43105 <reg name="@var{name}"
43106 bitsize="@var{size}"
43107 @r{[}regnum="@var{num}"@r{]}
43108 @r{[}save-restore="@var{save-restore}"@r{]}
43109 @r{[}type="@var{type}"@r{]}
43110 @r{[}group="@var{group}"@r{]}/>
43114 The components are as follows:
43119 The register's name; it must be unique within the target description.
43122 The register's size, in bits.
43125 The register's number. If omitted, a register's number is one greater
43126 than that of the previous register (either in the current feature or in
43127 a preceding feature); the first register in the target description
43128 defaults to zero. This register number is used to read or write
43129 the register; e.g.@: it is used in the remote @code{p} and @code{P}
43130 packets, and registers appear in the @code{g} and @code{G} packets
43131 in order of increasing register number.
43134 Whether the register should be preserved across inferior function
43135 calls; this must be either @code{yes} or @code{no}. The default is
43136 @code{yes}, which is appropriate for most registers except for
43137 some system control registers; this is not related to the target's
43141 The type of the register. @var{type} may be a predefined type, a type
43142 defined in the current feature, or one of the special types @code{int}
43143 and @code{float}. @code{int} is an integer type of the correct size
43144 for @var{bitsize}, and @code{float} is a floating point type (in the
43145 architecture's normal floating point format) of the correct size for
43146 @var{bitsize}. The default is @code{int}.
43149 The register group to which this register belongs. @var{group} must
43150 be either @code{general}, @code{float}, or @code{vector}. If no
43151 @var{group} is specified, @value{GDBN} will not display the register
43152 in @code{info registers}.
43156 @node Predefined Target Types
43157 @section Predefined Target Types
43158 @cindex target descriptions, predefined types
43160 Type definitions in the self-description can build up composite types
43161 from basic building blocks, but can not define fundamental types. Instead,
43162 standard identifiers are provided by @value{GDBN} for the fundamental
43163 types. The currently supported types are:
43172 Signed integer types holding the specified number of bits.
43179 Unsigned integer types holding the specified number of bits.
43183 Pointers to unspecified code and data. The program counter and
43184 any dedicated return address register may be marked as code
43185 pointers; printing a code pointer converts it into a symbolic
43186 address. The stack pointer and any dedicated address registers
43187 may be marked as data pointers.
43190 Single precision IEEE floating point.
43193 Double precision IEEE floating point.
43196 The 12-byte extended precision format used by ARM FPA registers.
43199 The 10-byte extended precision format used by x87 registers.
43202 32bit @sc{eflags} register used by x86.
43205 32bit @sc{mxcsr} register used by x86.
43209 @node Standard Target Features
43210 @section Standard Target Features
43211 @cindex target descriptions, standard features
43213 A target description must contain either no registers or all the
43214 target's registers. If the description contains no registers, then
43215 @value{GDBN} will assume a default register layout, selected based on
43216 the architecture. If the description contains any registers, the
43217 default layout will not be used; the standard registers must be
43218 described in the target description, in such a way that @value{GDBN}
43219 can recognize them.
43221 This is accomplished by giving specific names to feature elements
43222 which contain standard registers. @value{GDBN} will look for features
43223 with those names and verify that they contain the expected registers;
43224 if any known feature is missing required registers, or if any required
43225 feature is missing, @value{GDBN} will reject the target
43226 description. You can add additional registers to any of the
43227 standard features --- @value{GDBN} will display them just as if
43228 they were added to an unrecognized feature.
43230 This section lists the known features and their expected contents.
43231 Sample XML documents for these features are included in the
43232 @value{GDBN} source tree, in the directory @file{gdb/features}.
43234 Names recognized by @value{GDBN} should include the name of the
43235 company or organization which selected the name, and the overall
43236 architecture to which the feature applies; so e.g.@: the feature
43237 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
43239 The names of registers are not case sensitive for the purpose
43240 of recognizing standard features, but @value{GDBN} will only display
43241 registers using the capitalization used in the description.
43244 * AArch64 Features::
43249 * Nios II Features::
43250 * PowerPC Features::
43251 * S/390 and System z Features::
43256 @node AArch64 Features
43257 @subsection AArch64 Features
43258 @cindex target descriptions, AArch64 features
43260 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
43261 targets. It should contain registers @samp{x0} through @samp{x30},
43262 @samp{sp}, @samp{pc}, and @samp{cpsr}.
43264 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
43265 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
43269 @subsection ARM Features
43270 @cindex target descriptions, ARM features
43272 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
43274 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
43275 @samp{lr}, @samp{pc}, and @samp{cpsr}.
43277 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
43278 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
43279 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
43282 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
43283 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
43285 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
43286 it should contain at least registers @samp{wR0} through @samp{wR15} and
43287 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
43288 @samp{wCSSF}, and @samp{wCASF} registers are optional.
43290 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
43291 should contain at least registers @samp{d0} through @samp{d15}. If
43292 they are present, @samp{d16} through @samp{d31} should also be included.
43293 @value{GDBN} will synthesize the single-precision registers from
43294 halves of the double-precision registers.
43296 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
43297 need to contain registers; it instructs @value{GDBN} to display the
43298 VFP double-precision registers as vectors and to synthesize the
43299 quad-precision registers from pairs of double-precision registers.
43300 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
43301 be present and include 32 double-precision registers.
43303 @node i386 Features
43304 @subsection i386 Features
43305 @cindex target descriptions, i386 features
43307 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
43308 targets. It should describe the following registers:
43312 @samp{eax} through @samp{edi} plus @samp{eip} for i386
43314 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
43316 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
43317 @samp{fs}, @samp{gs}
43319 @samp{st0} through @samp{st7}
43321 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
43322 @samp{foseg}, @samp{fooff} and @samp{fop}
43325 The register sets may be different, depending on the target.
43327 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
43328 describe registers:
43332 @samp{xmm0} through @samp{xmm7} for i386
43334 @samp{xmm0} through @samp{xmm15} for amd64
43339 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
43340 @samp{org.gnu.gdb.i386.sse} feature. It should
43341 describe the upper 128 bits of @sc{ymm} registers:
43345 @samp{ymm0h} through @samp{ymm7h} for i386
43347 @samp{ymm0h} through @samp{ymm15h} for amd64
43350 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel(R)
43351 Memory Protection Extension (MPX). It should describe the following registers:
43355 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
43357 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
43360 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
43361 describe a single register, @samp{orig_eax}.
43363 @node MIPS Features
43364 @subsection @acronym{MIPS} Features
43365 @cindex target descriptions, @acronym{MIPS} features
43367 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
43368 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
43369 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
43372 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
43373 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
43374 registers. They may be 32-bit or 64-bit depending on the target.
43376 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
43377 it may be optional in a future version of @value{GDBN}. It should
43378 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
43379 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
43381 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
43382 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
43383 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
43384 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
43386 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
43387 contain a single register, @samp{restart}, which is used by the
43388 Linux kernel to control restartable syscalls.
43390 @node M68K Features
43391 @subsection M68K Features
43392 @cindex target descriptions, M68K features
43395 @item @samp{org.gnu.gdb.m68k.core}
43396 @itemx @samp{org.gnu.gdb.coldfire.core}
43397 @itemx @samp{org.gnu.gdb.fido.core}
43398 One of those features must be always present.
43399 The feature that is present determines which flavor of m68k is
43400 used. The feature that is present should contain registers
43401 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
43402 @samp{sp}, @samp{ps} and @samp{pc}.
43404 @item @samp{org.gnu.gdb.coldfire.fp}
43405 This feature is optional. If present, it should contain registers
43406 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
43410 @node Nios II Features
43411 @subsection Nios II Features
43412 @cindex target descriptions, Nios II features
43414 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
43415 targets. It should contain the 32 core registers (@samp{zero},
43416 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
43417 @samp{pc}, and the 16 control registers (@samp{status} through
43420 @node PowerPC Features
43421 @subsection PowerPC Features
43422 @cindex target descriptions, PowerPC features
43424 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
43425 targets. It should contain registers @samp{r0} through @samp{r31},
43426 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
43427 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
43429 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
43430 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
43432 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
43433 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
43436 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
43437 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
43438 will combine these registers with the floating point registers
43439 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
43440 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
43441 through @samp{vs63}, the set of vector registers for POWER7.
43443 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
43444 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
43445 @samp{spefscr}. SPE targets should provide 32-bit registers in
43446 @samp{org.gnu.gdb.power.core} and provide the upper halves in
43447 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
43448 these to present registers @samp{ev0} through @samp{ev31} to the
43451 @node S/390 and System z Features
43452 @subsection S/390 and System z Features
43453 @cindex target descriptions, S/390 features
43454 @cindex target descriptions, System z features
43456 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
43457 System z targets. It should contain the PSW and the 16 general
43458 registers. In particular, System z targets should provide the 64-bit
43459 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
43460 S/390 targets should provide the 32-bit versions of these registers.
43461 A System z target that runs in 31-bit addressing mode should provide
43462 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
43463 register's upper halves @samp{r0h} through @samp{r15h}, and their
43464 lower halves @samp{r0l} through @samp{r15l}.
43466 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
43467 contain the 64-bit registers @samp{f0} through @samp{f15}, and
43470 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
43471 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
43473 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
43474 contain the register @samp{orig_r2}, which is 64-bit wide on System z
43475 targets and 32-bit otherwise. In addition, the feature may contain
43476 the @samp{last_break} register, whose width depends on the addressing
43477 mode, as well as the @samp{system_call} register, which is always
43480 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
43481 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
43482 @samp{atia}, and @samp{tr0} through @samp{tr15}.
43484 @node TIC6x Features
43485 @subsection TMS320C6x Features
43486 @cindex target descriptions, TIC6x features
43487 @cindex target descriptions, TMS320C6x features
43488 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
43489 targets. It should contain registers @samp{A0} through @samp{A15},
43490 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
43492 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
43493 contain registers @samp{A16} through @samp{A31} and @samp{B16}
43494 through @samp{B31}.
43496 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
43497 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
43499 @node Operating System Information
43500 @appendix Operating System Information
43501 @cindex operating system information
43507 Users of @value{GDBN} often wish to obtain information about the state of
43508 the operating system running on the target---for example the list of
43509 processes, or the list of open files. This section describes the
43510 mechanism that makes it possible. This mechanism is similar to the
43511 target features mechanism (@pxref{Target Descriptions}), but focuses
43512 on a different aspect of target.
43514 Operating system information is retrived from the target via the
43515 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
43516 read}). The object name in the request should be @samp{osdata}, and
43517 the @var{annex} identifies the data to be fetched.
43520 @appendixsection Process list
43521 @cindex operating system information, process list
43523 When requesting the process list, the @var{annex} field in the
43524 @samp{qXfer} request should be @samp{processes}. The returned data is
43525 an XML document. The formal syntax of this document is defined in
43526 @file{gdb/features/osdata.dtd}.
43528 An example document is:
43531 <?xml version="1.0"?>
43532 <!DOCTYPE target SYSTEM "osdata.dtd">
43533 <osdata type="processes">
43535 <column name="pid">1</column>
43536 <column name="user">root</column>
43537 <column name="command">/sbin/init</column>
43538 <column name="cores">1,2,3</column>
43543 Each item should include a column whose name is @samp{pid}. The value
43544 of that column should identify the process on the target. The
43545 @samp{user} and @samp{command} columns are optional, and will be
43546 displayed by @value{GDBN}. The @samp{cores} column, if present,
43547 should contain a comma-separated list of cores that this process
43548 is running on. Target may provide additional columns,
43549 which @value{GDBN} currently ignores.
43551 @node Trace File Format
43552 @appendix Trace File Format
43553 @cindex trace file format
43555 The trace file comes in three parts: a header, a textual description
43556 section, and a trace frame section with binary data.
43558 The header has the form @code{\x7fTRACE0\n}. The first byte is
43559 @code{0x7f} so as to indicate that the file contains binary data,
43560 while the @code{0} is a version number that may have different values
43563 The description section consists of multiple lines of @sc{ascii} text
43564 separated by newline characters (@code{0xa}). The lines may include a
43565 variety of optional descriptive or context-setting information, such
43566 as tracepoint definitions or register set size. @value{GDBN} will
43567 ignore any line that it does not recognize. An empty line marks the end
43570 @c FIXME add some specific types of data
43572 The trace frame section consists of a number of consecutive frames.
43573 Each frame begins with a two-byte tracepoint number, followed by a
43574 four-byte size giving the amount of data in the frame. The data in
43575 the frame consists of a number of blocks, each introduced by a
43576 character indicating its type (at least register, memory, and trace
43577 state variable). The data in this section is raw binary, not a
43578 hexadecimal or other encoding; its endianness matches the target's
43581 @c FIXME bi-arch may require endianness/arch info in description section
43584 @item R @var{bytes}
43585 Register block. The number and ordering of bytes matches that of a
43586 @code{g} packet in the remote protocol. Note that these are the
43587 actual bytes, in target order and @value{GDBN} register order, not a
43588 hexadecimal encoding.
43590 @item M @var{address} @var{length} @var{bytes}...
43591 Memory block. This is a contiguous block of memory, at the 8-byte
43592 address @var{address}, with a 2-byte length @var{length}, followed by
43593 @var{length} bytes.
43595 @item V @var{number} @var{value}
43596 Trace state variable block. This records the 8-byte signed value
43597 @var{value} of trace state variable numbered @var{number}.
43601 Future enhancements of the trace file format may include additional types
43604 @node Index Section Format
43605 @appendix @code{.gdb_index} section format
43606 @cindex .gdb_index section format
43607 @cindex index section format
43609 This section documents the index section that is created by @code{save
43610 gdb-index} (@pxref{Index Files}). The index section is
43611 DWARF-specific; some knowledge of DWARF is assumed in this
43614 The mapped index file format is designed to be directly
43615 @code{mmap}able on any architecture. In most cases, a datum is
43616 represented using a little-endian 32-bit integer value, called an
43617 @code{offset_type}. Big endian machines must byte-swap the values
43618 before using them. Exceptions to this rule are noted. The data is
43619 laid out such that alignment is always respected.
43621 A mapped index consists of several areas, laid out in order.
43625 The file header. This is a sequence of values, of @code{offset_type}
43626 unless otherwise noted:
43630 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
43631 Version 4 uses a different hashing function from versions 5 and 6.
43632 Version 6 includes symbols for inlined functions, whereas versions 4
43633 and 5 do not. Version 7 adds attributes to the CU indices in the
43634 symbol table. Version 8 specifies that symbols from DWARF type units
43635 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
43636 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
43638 @value{GDBN} will only read version 4, 5, or 6 indices
43639 by specifying @code{set use-deprecated-index-sections on}.
43640 GDB has a workaround for potentially broken version 7 indices so it is
43641 currently not flagged as deprecated.
43644 The offset, from the start of the file, of the CU list.
43647 The offset, from the start of the file, of the types CU list. Note
43648 that this area can be empty, in which case this offset will be equal
43649 to the next offset.
43652 The offset, from the start of the file, of the address area.
43655 The offset, from the start of the file, of the symbol table.
43658 The offset, from the start of the file, of the constant pool.
43662 The CU list. This is a sequence of pairs of 64-bit little-endian
43663 values, sorted by the CU offset. The first element in each pair is
43664 the offset of a CU in the @code{.debug_info} section. The second
43665 element in each pair is the length of that CU. References to a CU
43666 elsewhere in the map are done using a CU index, which is just the
43667 0-based index into this table. Note that if there are type CUs, then
43668 conceptually CUs and type CUs form a single list for the purposes of
43672 The types CU list. This is a sequence of triplets of 64-bit
43673 little-endian values. In a triplet, the first value is the CU offset,
43674 the second value is the type offset in the CU, and the third value is
43675 the type signature. The types CU list is not sorted.
43678 The address area. The address area consists of a sequence of address
43679 entries. Each address entry has three elements:
43683 The low address. This is a 64-bit little-endian value.
43686 The high address. This is a 64-bit little-endian value. Like
43687 @code{DW_AT_high_pc}, the value is one byte beyond the end.
43690 The CU index. This is an @code{offset_type} value.
43694 The symbol table. This is an open-addressed hash table. The size of
43695 the hash table is always a power of 2.
43697 Each slot in the hash table consists of a pair of @code{offset_type}
43698 values. The first value is the offset of the symbol's name in the
43699 constant pool. The second value is the offset of the CU vector in the
43702 If both values are 0, then this slot in the hash table is empty. This
43703 is ok because while 0 is a valid constant pool index, it cannot be a
43704 valid index for both a string and a CU vector.
43706 The hash value for a table entry is computed by applying an
43707 iterative hash function to the symbol's name. Starting with an
43708 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
43709 the string is incorporated into the hash using the formula depending on the
43714 The formula is @code{r = r * 67 + c - 113}.
43716 @item Versions 5 to 7
43717 The formula is @code{r = r * 67 + tolower (c) - 113}.
43720 The terminating @samp{\0} is not incorporated into the hash.
43722 The step size used in the hash table is computed via
43723 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43724 value, and @samp{size} is the size of the hash table. The step size
43725 is used to find the next candidate slot when handling a hash
43728 The names of C@t{++} symbols in the hash table are canonicalized. We
43729 don't currently have a simple description of the canonicalization
43730 algorithm; if you intend to create new index sections, you must read
43734 The constant pool. This is simply a bunch of bytes. It is organized
43735 so that alignment is correct: CU vectors are stored first, followed by
43738 A CU vector in the constant pool is a sequence of @code{offset_type}
43739 values. The first value is the number of CU indices in the vector.
43740 Each subsequent value is the index and symbol attributes of a CU in
43741 the CU list. This element in the hash table is used to indicate which
43742 CUs define the symbol and how the symbol is used.
43743 See below for the format of each CU index+attributes entry.
43745 A string in the constant pool is zero-terminated.
43748 Attributes were added to CU index values in @code{.gdb_index} version 7.
43749 If a symbol has multiple uses within a CU then there is one
43750 CU index+attributes value for each use.
43752 The format of each CU index+attributes entry is as follows
43758 This is the index of the CU in the CU list.
43760 These bits are reserved for future purposes and must be zero.
43762 The kind of the symbol in the CU.
43766 This value is reserved and should not be used.
43767 By reserving zero the full @code{offset_type} value is backwards compatible
43768 with previous versions of the index.
43770 The symbol is a type.
43772 The symbol is a variable or an enum value.
43774 The symbol is a function.
43776 Any other kind of symbol.
43778 These values are reserved.
43782 This bit is zero if the value is global and one if it is static.
43784 The determination of whether a symbol is global or static is complicated.
43785 The authorative reference is the file @file{dwarf2read.c} in
43786 @value{GDBN} sources.
43790 This pseudo-code describes the computation of a symbol's kind and
43791 global/static attributes in the index.
43794 is_external = get_attribute (die, DW_AT_external);
43795 language = get_attribute (cu_die, DW_AT_language);
43798 case DW_TAG_typedef:
43799 case DW_TAG_base_type:
43800 case DW_TAG_subrange_type:
43804 case DW_TAG_enumerator:
43806 is_static = (language != CPLUS && language != JAVA);
43808 case DW_TAG_subprogram:
43810 is_static = ! (is_external || language == ADA);
43812 case DW_TAG_constant:
43814 is_static = ! is_external;
43816 case DW_TAG_variable:
43818 is_static = ! is_external;
43820 case DW_TAG_namespace:
43824 case DW_TAG_class_type:
43825 case DW_TAG_interface_type:
43826 case DW_TAG_structure_type:
43827 case DW_TAG_union_type:
43828 case DW_TAG_enumeration_type:
43830 is_static = (language != CPLUS && language != JAVA);
43838 @appendix Manual pages
43842 * gdb man:: The GNU Debugger man page
43843 * gdbserver man:: Remote Server for the GNU Debugger man page
43844 * gcore man:: Generate a core file of a running program
43845 * gdbinit man:: gdbinit scripts
43851 @c man title gdb The GNU Debugger
43853 @c man begin SYNOPSIS gdb
43854 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43855 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43856 [@option{-b}@w{ }@var{bps}]
43857 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43858 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43859 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43860 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43861 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43864 @c man begin DESCRIPTION gdb
43865 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43866 going on ``inside'' another program while it executes -- or what another
43867 program was doing at the moment it crashed.
43869 @value{GDBN} can do four main kinds of things (plus other things in support of
43870 these) to help you catch bugs in the act:
43874 Start your program, specifying anything that might affect its behavior.
43877 Make your program stop on specified conditions.
43880 Examine what has happened, when your program has stopped.
43883 Change things in your program, so you can experiment with correcting the
43884 effects of one bug and go on to learn about another.
43887 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43890 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43891 commands from the terminal until you tell it to exit with the @value{GDBN}
43892 command @code{quit}. You can get online help from @value{GDBN} itself
43893 by using the command @code{help}.
43895 You can run @code{gdb} with no arguments or options; but the most
43896 usual way to start @value{GDBN} is with one argument or two, specifying an
43897 executable program as the argument:
43903 You can also start with both an executable program and a core file specified:
43909 You can, instead, specify a process ID as a second argument, if you want
43910 to debug a running process:
43918 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43919 named @file{1234}; @value{GDBN} does check for a core file first).
43920 With option @option{-p} you can omit the @var{program} filename.
43922 Here are some of the most frequently needed @value{GDBN} commands:
43924 @c pod2man highlights the right hand side of the @item lines.
43926 @item break [@var{file}:]@var{functiop}
43927 Set a breakpoint at @var{function} (in @var{file}).
43929 @item run [@var{arglist}]
43930 Start your program (with @var{arglist}, if specified).
43933 Backtrace: display the program stack.
43935 @item print @var{expr}
43936 Display the value of an expression.
43939 Continue running your program (after stopping, e.g. at a breakpoint).
43942 Execute next program line (after stopping); step @emph{over} any
43943 function calls in the line.
43945 @item edit [@var{file}:]@var{function}
43946 look at the program line where it is presently stopped.
43948 @item list [@var{file}:]@var{function}
43949 type the text of the program in the vicinity of where it is presently stopped.
43952 Execute next program line (after stopping); step @emph{into} any
43953 function calls in the line.
43955 @item help [@var{name}]
43956 Show information about @value{GDBN} command @var{name}, or general information
43957 about using @value{GDBN}.
43960 Exit from @value{GDBN}.
43964 For full details on @value{GDBN},
43965 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43966 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43967 as the @code{gdb} entry in the @code{info} program.
43971 @c man begin OPTIONS gdb
43972 Any arguments other than options specify an executable
43973 file and core file (or process ID); that is, the first argument
43974 encountered with no
43975 associated option flag is equivalent to a @option{-se} option, and the second,
43976 if any, is equivalent to a @option{-c} option if it's the name of a file.
43978 both long and short forms; both are shown here. The long forms are also
43979 recognized if you truncate them, so long as enough of the option is
43980 present to be unambiguous. (If you prefer, you can flag option
43981 arguments with @option{+} rather than @option{-}, though we illustrate the
43982 more usual convention.)
43984 All the options and command line arguments you give are processed
43985 in sequential order. The order makes a difference when the @option{-x}
43991 List all options, with brief explanations.
43993 @item -symbols=@var{file}
43994 @itemx -s @var{file}
43995 Read symbol table from file @var{file}.
43998 Enable writing into executable and core files.
44000 @item -exec=@var{file}
44001 @itemx -e @var{file}
44002 Use file @var{file} as the executable file to execute when
44003 appropriate, and for examining pure data in conjunction with a core
44006 @item -se=@var{file}
44007 Read symbol table from file @var{file} and use it as the executable
44010 @item -core=@var{file}
44011 @itemx -c @var{file}
44012 Use file @var{file} as a core dump to examine.
44014 @item -command=@var{file}
44015 @itemx -x @var{file}
44016 Execute @value{GDBN} commands from file @var{file}.
44018 @item -ex @var{command}
44019 Execute given @value{GDBN} @var{command}.
44021 @item -directory=@var{directory}
44022 @itemx -d @var{directory}
44023 Add @var{directory} to the path to search for source files.
44026 Do not execute commands from @file{~/.gdbinit}.
44030 Do not execute commands from any @file{.gdbinit} initialization files.
44034 ``Quiet''. Do not print the introductory and copyright messages. These
44035 messages are also suppressed in batch mode.
44038 Run in batch mode. Exit with status @code{0} after processing all the command
44039 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
44040 Exit with nonzero status if an error occurs in executing the @value{GDBN}
44041 commands in the command files.
44043 Batch mode may be useful for running @value{GDBN} as a filter, for example to
44044 download and run a program on another computer; in order to make this
44045 more useful, the message
44048 Program exited normally.
44052 (which is ordinarily issued whenever a program running under @value{GDBN} control
44053 terminates) is not issued when running in batch mode.
44055 @item -cd=@var{directory}
44056 Run @value{GDBN} using @var{directory} as its working directory,
44057 instead of the current directory.
44061 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
44062 @value{GDBN} to output the full file name and line number in a standard,
44063 recognizable fashion each time a stack frame is displayed (which
44064 includes each time the program stops). This recognizable format looks
44065 like two @samp{\032} characters, followed by the file name, line number
44066 and character position separated by colons, and a newline. The
44067 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
44068 characters as a signal to display the source code for the frame.
44071 Set the line speed (baud rate or bits per second) of any serial
44072 interface used by @value{GDBN} for remote debugging.
44074 @item -tty=@var{device}
44075 Run using @var{device} for your program's standard input and output.
44079 @c man begin SEEALSO gdb
44081 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44082 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44083 documentation are properly installed at your site, the command
44090 should give you access to the complete manual.
44092 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44093 Richard M. Stallman and Roland H. Pesch, July 1991.
44097 @node gdbserver man
44098 @heading gdbserver man
44100 @c man title gdbserver Remote Server for the GNU Debugger
44102 @c man begin SYNOPSIS gdbserver
44103 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44105 gdbserver --attach @var{comm} @var{pid}
44107 gdbserver --multi @var{comm}
44111 @c man begin DESCRIPTION gdbserver
44112 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
44113 than the one which is running the program being debugged.
44116 @subheading Usage (server (target) side)
44119 Usage (server (target) side):
44122 First, you need to have a copy of the program you want to debug put onto
44123 the target system. The program can be stripped to save space if needed, as
44124 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
44125 the @value{GDBN} running on the host system.
44127 To use the server, you log on to the target system, and run the @command{gdbserver}
44128 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
44129 your program, and (c) its arguments. The general syntax is:
44132 target> gdbserver @var{comm} @var{program} [@var{args} ...]
44135 For example, using a serial port, you might say:
44139 @c @file would wrap it as F</dev/com1>.
44140 target> gdbserver /dev/com1 emacs foo.txt
44143 target> gdbserver @file{/dev/com1} emacs foo.txt
44147 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
44148 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
44149 waits patiently for the host @value{GDBN} to communicate with it.
44151 To use a TCP connection, you could say:
44154 target> gdbserver host:2345 emacs foo.txt
44157 This says pretty much the same thing as the last example, except that we are
44158 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
44159 that we are expecting to see a TCP connection from @code{host} to local TCP port
44160 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
44161 want for the port number as long as it does not conflict with any existing TCP
44162 ports on the target system. This same port number must be used in the host
44163 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
44164 you chose a port number that conflicts with another service, @command{gdbserver} will
44165 print an error message and exit.
44167 @command{gdbserver} can also attach to running programs.
44168 This is accomplished via the @option{--attach} argument. The syntax is:
44171 target> gdbserver --attach @var{comm} @var{pid}
44174 @var{pid} is the process ID of a currently running process. It isn't
44175 necessary to point @command{gdbserver} at a binary for the running process.
44177 To start @code{gdbserver} without supplying an initial command to run
44178 or process ID to attach, use the @option{--multi} command line option.
44179 In such case you should connect using @kbd{target extended-remote} to start
44180 the program you want to debug.
44183 target> gdbserver --multi @var{comm}
44187 @subheading Usage (host side)
44193 You need an unstripped copy of the target program on your host system, since
44194 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
44195 would, with the target program as the first argument. (You may need to use the
44196 @option{--baud} option if the serial line is running at anything except 9600 baud.)
44197 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
44198 new command you need to know about is @code{target remote}
44199 (or @code{target extended-remote}). Its argument is either
44200 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
44201 descriptor. For example:
44205 @c @file would wrap it as F</dev/ttyb>.
44206 (gdb) target remote /dev/ttyb
44209 (gdb) target remote @file{/dev/ttyb}
44214 communicates with the server via serial line @file{/dev/ttyb}, and:
44217 (gdb) target remote the-target:2345
44221 communicates via a TCP connection to port 2345 on host `the-target', where
44222 you previously started up @command{gdbserver} with the same port number. Note that for
44223 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
44224 command, otherwise you may get an error that looks something like
44225 `Connection refused'.
44227 @command{gdbserver} can also debug multiple inferiors at once,
44230 the @value{GDBN} manual in node @code{Inferiors and Programs}
44231 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
44234 @ref{Inferiors and Programs}.
44236 In such case use the @code{extended-remote} @value{GDBN} command variant:
44239 (gdb) target extended-remote the-target:2345
44242 The @command{gdbserver} option @option{--multi} may or may not be used in such
44246 @c man begin OPTIONS gdbserver
44247 There are three different modes for invoking @command{gdbserver}:
44252 Debug a specific program specified by its program name:
44255 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
44258 The @var{comm} parameter specifies how should the server communicate
44259 with @value{GDBN}; it is either a device name (to use a serial line),
44260 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
44261 stdin/stdout of @code{gdbserver}. Specify the name of the program to
44262 debug in @var{prog}. Any remaining arguments will be passed to the
44263 program verbatim. When the program exits, @value{GDBN} will close the
44264 connection, and @code{gdbserver} will exit.
44267 Debug a specific program by specifying the process ID of a running
44271 gdbserver --attach @var{comm} @var{pid}
44274 The @var{comm} parameter is as described above. Supply the process ID
44275 of a running program in @var{pid}; @value{GDBN} will do everything
44276 else. Like with the previous mode, when the process @var{pid} exits,
44277 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
44280 Multi-process mode -- debug more than one program/process:
44283 gdbserver --multi @var{comm}
44286 In this mode, @value{GDBN} can instruct @command{gdbserver} which
44287 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
44288 close the connection when a process being debugged exits, so you can
44289 debug several processes in the same session.
44292 In each of the modes you may specify these options:
44297 List all options, with brief explanations.
44300 This option causes @command{gdbserver} to print its version number and exit.
44303 @command{gdbserver} will attach to a running program. The syntax is:
44306 target> gdbserver --attach @var{comm} @var{pid}
44309 @var{pid} is the process ID of a currently running process. It isn't
44310 necessary to point @command{gdbserver} at a binary for the running process.
44313 To start @code{gdbserver} without supplying an initial command to run
44314 or process ID to attach, use this command line option.
44315 Then you can connect using @kbd{target extended-remote} and start
44316 the program you want to debug. The syntax is:
44319 target> gdbserver --multi @var{comm}
44323 Instruct @code{gdbserver} to display extra status information about the debugging
44325 This option is intended for @code{gdbserver} development and for bug reports to
44328 @item --remote-debug
44329 Instruct @code{gdbserver} to display remote protocol debug output.
44330 This option is intended for @code{gdbserver} development and for bug reports to
44334 Specify a wrapper to launch programs
44335 for debugging. The option should be followed by the name of the
44336 wrapper, then any command-line arguments to pass to the wrapper, then
44337 @kbd{--} indicating the end of the wrapper arguments.
44340 By default, @command{gdbserver} keeps the listening TCP port open, so that
44341 additional connections are possible. However, if you start @code{gdbserver}
44342 with the @option{--once} option, it will stop listening for any further
44343 connection attempts after connecting to the first @value{GDBN} session.
44345 @c --disable-packet is not documented for users.
44347 @c --disable-randomization and --no-disable-randomization are superseded by
44348 @c QDisableRandomization.
44353 @c man begin SEEALSO gdbserver
44355 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44356 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44357 documentation are properly installed at your site, the command
44363 should give you access to the complete manual.
44365 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44366 Richard M. Stallman and Roland H. Pesch, July 1991.
44373 @c man title gcore Generate a core file of a running program
44376 @c man begin SYNOPSIS gcore
44377 gcore [-o @var{filename}] @var{pid}
44381 @c man begin DESCRIPTION gcore
44382 Generate a core dump of a running program with process ID @var{pid}.
44383 Produced file is equivalent to a kernel produced core file as if the process
44384 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
44385 limit). Unlike after a crash, after @command{gcore} the program remains
44386 running without any change.
44389 @c man begin OPTIONS gcore
44391 @item -o @var{filename}
44392 The optional argument
44393 @var{filename} specifies the file name where to put the core dump.
44394 If not specified, the file name defaults to @file{core.@var{pid}},
44395 where @var{pid} is the running program process ID.
44399 @c man begin SEEALSO gcore
44401 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44402 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44403 documentation are properly installed at your site, the command
44410 should give you access to the complete manual.
44412 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44413 Richard M. Stallman and Roland H. Pesch, July 1991.
44420 @c man title gdbinit GDB initialization scripts
44423 @c man begin SYNOPSIS gdbinit
44424 @ifset SYSTEM_GDBINIT
44425 @value{SYSTEM_GDBINIT}
44434 @c man begin DESCRIPTION gdbinit
44435 These files contain @value{GDBN} commands to automatically execute during
44436 @value{GDBN} startup. The lines of contents are canned sequences of commands,
44439 the @value{GDBN} manual in node @code{Sequences}
44440 -- shell command @code{info -f gdb -n Sequences}.
44446 Please read more in
44448 the @value{GDBN} manual in node @code{Startup}
44449 -- shell command @code{info -f gdb -n Startup}.
44456 @ifset SYSTEM_GDBINIT
44457 @item @value{SYSTEM_GDBINIT}
44459 @ifclear SYSTEM_GDBINIT
44460 @item (not enabled with @code{--with-system-gdbinit} during compilation)
44462 System-wide initialization file. It is executed unless user specified
44463 @value{GDBN} option @code{-nx} or @code{-n}.
44466 the @value{GDBN} manual in node @code{System-wide configuration}
44467 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
44470 @ref{System-wide configuration}.
44474 User initialization file. It is executed unless user specified
44475 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
44478 Initialization file for current directory. It may need to be enabled with
44479 @value{GDBN} security command @code{set auto-load local-gdbinit}.
44482 the @value{GDBN} manual in node @code{Init File in the Current Directory}
44483 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
44486 @ref{Init File in the Current Directory}.
44491 @c man begin SEEALSO gdbinit
44493 gdb(1), @code{info -f gdb -n Startup}
44495 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
44496 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
44497 documentation are properly installed at your site, the command
44503 should give you access to the complete manual.
44505 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
44506 Richard M. Stallman and Roland H. Pesch, July 1991.
44512 @node GNU Free Documentation License
44513 @appendix GNU Free Documentation License
44516 @node Concept Index
44517 @unnumbered Concept Index
44521 @node Command and Variable Index
44522 @unnumbered Command, Variable, and Function Index
44527 % I think something like @@colophon should be in texinfo. In the
44529 \long\def\colophon{\hbox to0pt{}\vfill
44530 \centerline{The body of this manual is set in}
44531 \centerline{\fontname\tenrm,}
44532 \centerline{with headings in {\bf\fontname\tenbf}}
44533 \centerline{and examples in {\tt\fontname\tentt}.}
44534 \centerline{{\it\fontname\tenit\/},}
44535 \centerline{{\bf\fontname\tenbf}, and}
44536 \centerline{{\sl\fontname\tensl\/}}
44537 \centerline{are used for emphasis.}\vfill}
44539 % Blame: doc@@cygnus.com, 1991.