1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-2016 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{} 1988-2016 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) 1988-2016 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}
889 (or @code{-q}/@code{--quiet}):
892 @value{GDBP} --silent
896 You can further control how @value{GDBN} starts up by using command-line
897 options. @value{GDBN} itself can remind you of the options available.
907 to display all available options and briefly describe their use
908 (@samp{@value{GDBP} -h} is a shorter equivalent).
910 All options and command line arguments you give are processed
911 in sequential order. The order makes a difference when the
912 @samp{-x} option is used.
916 * File Options:: Choosing files
917 * Mode Options:: Choosing modes
918 * Startup:: What @value{GDBN} does during startup
922 @subsection Choosing Files
924 When @value{GDBN} starts, it reads any arguments other than options as
925 specifying an executable file and core file (or process ID). This is
926 the same as if the arguments were specified by the @samp{-se} and
927 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
928 first argument that does not have an associated option flag as
929 equivalent to the @samp{-se} option followed by that argument; and the
930 second argument that does not have an associated option flag, if any, as
931 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
932 If the second argument begins with a decimal digit, @value{GDBN} will
933 first attempt to attach to it as a process, and if that fails, attempt
934 to open it as a corefile. If you have a corefile whose name begins with
935 a digit, you can prevent @value{GDBN} from treating it as a pid by
936 prefixing it with @file{./}, e.g.@: @file{./12345}.
938 If @value{GDBN} has not been configured to included core file support,
939 such as for most embedded targets, then it will complain about a second
940 argument and ignore it.
942 Many options have both long and short forms; both are shown in the
943 following list. @value{GDBN} also recognizes the long forms if you truncate
944 them, so long as enough of the option is present to be unambiguous.
945 (If you prefer, you can flag option arguments with @samp{--} rather
946 than @samp{-}, though we illustrate the more usual convention.)
948 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
949 @c way, both those who look for -foo and --foo in the index, will find
953 @item -symbols @var{file}
955 @cindex @code{--symbols}
957 Read symbol table from file @var{file}.
959 @item -exec @var{file}
961 @cindex @code{--exec}
963 Use file @var{file} as the executable file to execute when appropriate,
964 and for examining pure data in conjunction with a core dump.
968 Read symbol table from file @var{file} and use it as the executable
971 @item -core @var{file}
973 @cindex @code{--core}
975 Use file @var{file} as a core dump to examine.
977 @item -pid @var{number}
978 @itemx -p @var{number}
981 Connect to process ID @var{number}, as with the @code{attach} command.
983 @item -command @var{file}
985 @cindex @code{--command}
987 Execute commands from file @var{file}. The contents of this file is
988 evaluated exactly as the @code{source} command would.
989 @xref{Command Files,, Command files}.
991 @item -eval-command @var{command}
992 @itemx -ex @var{command}
993 @cindex @code{--eval-command}
995 Execute a single @value{GDBN} command.
997 This option may be used multiple times to call multiple commands. It may
998 also be interleaved with @samp{-command} as required.
1001 @value{GDBP} -ex 'target sim' -ex 'load' \
1002 -x setbreakpoints -ex 'run' a.out
1005 @item -init-command @var{file}
1006 @itemx -ix @var{file}
1007 @cindex @code{--init-command}
1009 Execute commands from file @var{file} before loading the inferior (but
1010 after loading gdbinit files).
1013 @item -init-eval-command @var{command}
1014 @itemx -iex @var{command}
1015 @cindex @code{--init-eval-command}
1017 Execute a single @value{GDBN} command before loading the inferior (but
1018 after loading gdbinit files).
1021 @item -directory @var{directory}
1022 @itemx -d @var{directory}
1023 @cindex @code{--directory}
1025 Add @var{directory} to the path to search for source and script files.
1029 @cindex @code{--readnow}
1031 Read each symbol file's entire symbol table immediately, rather than
1032 the default, which is to read it incrementally as it is needed.
1033 This makes startup slower, but makes future operations faster.
1038 @subsection Choosing Modes
1040 You can run @value{GDBN} in various alternative modes---for example, in
1041 batch mode or quiet mode.
1049 Do not execute commands found in any initialization file.
1050 There are three init files, loaded in the following order:
1053 @item @file{system.gdbinit}
1054 This is the system-wide init file.
1055 Its location is specified with the @code{--with-system-gdbinit}
1056 configure option (@pxref{System-wide configuration}).
1057 It is loaded first when @value{GDBN} starts, before command line options
1058 have been processed.
1059 @item @file{~/.gdbinit}
1060 This is the init file in your home directory.
1061 It is loaded next, after @file{system.gdbinit}, and before
1062 command options have been processed.
1063 @item @file{./.gdbinit}
1064 This is the init file in the current directory.
1065 It is loaded last, after command line options other than @code{-x} and
1066 @code{-ex} have been processed. Command line options @code{-x} and
1067 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1070 For further documentation on startup processing, @xref{Startup}.
1071 For documentation on how to write command files,
1072 @xref{Command Files,,Command Files}.
1077 Do not execute commands found in @file{~/.gdbinit}, the init file
1078 in your home directory.
1084 @cindex @code{--quiet}
1085 @cindex @code{--silent}
1087 ``Quiet''. Do not print the introductory and copyright messages. These
1088 messages are also suppressed in batch mode.
1091 @cindex @code{--batch}
1092 Run in batch mode. Exit with status @code{0} after processing all the
1093 command files specified with @samp{-x} (and all commands from
1094 initialization files, if not inhibited with @samp{-n}). Exit with
1095 nonzero status if an error occurs in executing the @value{GDBN} commands
1096 in the command files. Batch mode also disables pagination, sets unlimited
1097 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1098 off} were in effect (@pxref{Messages/Warnings}).
1100 Batch mode may be useful for running @value{GDBN} as a filter, for
1101 example to download and run a program on another computer; in order to
1102 make this more useful, the message
1105 Program exited normally.
1109 (which is ordinarily issued whenever a program running under
1110 @value{GDBN} control terminates) is not issued when running in batch
1114 @cindex @code{--batch-silent}
1115 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1116 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1117 unaffected). This is much quieter than @samp{-silent} and would be useless
1118 for an interactive session.
1120 This is particularly useful when using targets that give @samp{Loading section}
1121 messages, for example.
1123 Note that targets that give their output via @value{GDBN}, as opposed to
1124 writing directly to @code{stdout}, will also be made silent.
1126 @item -return-child-result
1127 @cindex @code{--return-child-result}
1128 The return code from @value{GDBN} will be the return code from the child
1129 process (the process being debugged), with the following exceptions:
1133 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1134 internal error. In this case the exit code is the same as it would have been
1135 without @samp{-return-child-result}.
1137 The user quits with an explicit value. E.g., @samp{quit 1}.
1139 The child process never runs, or is not allowed to terminate, in which case
1140 the exit code will be -1.
1143 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1144 when @value{GDBN} is being used as a remote program loader or simulator
1149 @cindex @code{--nowindows}
1151 ``No windows''. If @value{GDBN} comes with a graphical user interface
1152 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1153 interface. If no GUI is available, this option has no effect.
1157 @cindex @code{--windows}
1159 If @value{GDBN} includes a GUI, then this option requires it to be
1162 @item -cd @var{directory}
1164 Run @value{GDBN} using @var{directory} as its working directory,
1165 instead of the current directory.
1167 @item -data-directory @var{directory}
1168 @itemx -D @var{directory}
1169 @cindex @code{--data-directory}
1171 Run @value{GDBN} using @var{directory} as its data directory.
1172 The data directory is where @value{GDBN} searches for its
1173 auxiliary files. @xref{Data Files}.
1177 @cindex @code{--fullname}
1179 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1180 subprocess. It tells @value{GDBN} to output the full file name and line
1181 number in a standard, recognizable fashion each time a stack frame is
1182 displayed (which includes each time your program stops). This
1183 recognizable format looks like two @samp{\032} characters, followed by
1184 the file name, line number and character position separated by colons,
1185 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1186 @samp{\032} characters as a signal to display the source code for the
1189 @item -annotate @var{level}
1190 @cindex @code{--annotate}
1191 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1192 effect is identical to using @samp{set annotate @var{level}}
1193 (@pxref{Annotations}). The annotation @var{level} controls how much
1194 information @value{GDBN} prints together with its prompt, values of
1195 expressions, source lines, and other types of output. Level 0 is the
1196 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1197 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1198 that control @value{GDBN}, and level 2 has been deprecated.
1200 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1204 @cindex @code{--args}
1205 Change interpretation of command line so that arguments following the
1206 executable file are passed as command line arguments to the inferior.
1207 This option stops option processing.
1209 @item -baud @var{bps}
1211 @cindex @code{--baud}
1213 Set the line speed (baud rate or bits per second) of any serial
1214 interface used by @value{GDBN} for remote debugging.
1216 @item -l @var{timeout}
1218 Set the timeout (in seconds) of any communication used by @value{GDBN}
1219 for remote debugging.
1221 @item -tty @var{device}
1222 @itemx -t @var{device}
1223 @cindex @code{--tty}
1225 Run using @var{device} for your program's standard input and output.
1226 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1228 @c resolve the situation of these eventually
1230 @cindex @code{--tui}
1231 Activate the @dfn{Text User Interface} when starting. The Text User
1232 Interface manages several text windows on the terminal, showing
1233 source, assembly, registers and @value{GDBN} command outputs
1234 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1235 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1236 Using @value{GDBN} under @sc{gnu} Emacs}).
1238 @item -interpreter @var{interp}
1239 @cindex @code{--interpreter}
1240 Use the interpreter @var{interp} for interface with the controlling
1241 program or device. This option is meant to be set by programs which
1242 communicate with @value{GDBN} using it as a back end.
1243 @xref{Interpreters, , Command Interpreters}.
1245 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1246 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1247 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1248 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1249 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1250 @sc{gdb/mi} interfaces are no longer supported.
1253 @cindex @code{--write}
1254 Open the executable and core files for both reading and writing. This
1255 is equivalent to the @samp{set write on} command inside @value{GDBN}
1259 @cindex @code{--statistics}
1260 This option causes @value{GDBN} to print statistics about time and
1261 memory usage after it completes each command and returns to the prompt.
1264 @cindex @code{--version}
1265 This option causes @value{GDBN} to print its version number and
1266 no-warranty blurb, and exit.
1268 @item -configuration
1269 @cindex @code{--configuration}
1270 This option causes @value{GDBN} to print details about its build-time
1271 configuration parameters, and then exit. These details can be
1272 important when reporting @value{GDBN} bugs (@pxref{GDB Bugs}).
1277 @subsection What @value{GDBN} Does During Startup
1278 @cindex @value{GDBN} startup
1280 Here's the description of what @value{GDBN} does during session startup:
1284 Sets up the command interpreter as specified by the command line
1285 (@pxref{Mode Options, interpreter}).
1289 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1290 used when building @value{GDBN}; @pxref{System-wide configuration,
1291 ,System-wide configuration and settings}) and executes all the commands in
1294 @anchor{Home Directory Init File}
1296 Reads the init file (if any) in your home directory@footnote{On
1297 DOS/Windows systems, the home directory is the one pointed to by the
1298 @code{HOME} environment variable.} and executes all the commands in
1301 @anchor{Option -init-eval-command}
1303 Executes commands and command files specified by the @samp{-iex} and
1304 @samp{-ix} options in their specified order. Usually you should use the
1305 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1306 settings before @value{GDBN} init files get executed and before inferior
1310 Processes command line options and operands.
1312 @anchor{Init File in the Current Directory during Startup}
1314 Reads and executes the commands from init file (if any) in the current
1315 working directory as long as @samp{set auto-load local-gdbinit} is set to
1316 @samp{on} (@pxref{Init File in the Current Directory}).
1317 This is only done if the current directory is
1318 different from your home directory. Thus, you can have more than one
1319 init file, one generic in your home directory, and another, specific
1320 to the program you are debugging, in the directory where you invoke
1324 If the command line specified a program to debug, or a process to
1325 attach to, or a core file, @value{GDBN} loads any auto-loaded
1326 scripts provided for the program or for its loaded shared libraries.
1327 @xref{Auto-loading}.
1329 If you wish to disable the auto-loading during startup,
1330 you must do something like the following:
1333 $ gdb -iex "set auto-load python-scripts off" myprogram
1336 Option @samp{-ex} does not work because the auto-loading is then turned
1340 Executes commands and command files specified by the @samp{-ex} and
1341 @samp{-x} options in their specified order. @xref{Command Files}, for
1342 more details about @value{GDBN} command files.
1345 Reads the command history recorded in the @dfn{history file}.
1346 @xref{Command History}, for more details about the command history and the
1347 files where @value{GDBN} records it.
1350 Init files use the same syntax as @dfn{command files} (@pxref{Command
1351 Files}) and are processed by @value{GDBN} in the same way. The init
1352 file in your home directory can set options (such as @samp{set
1353 complaints}) that affect subsequent processing of command line options
1354 and operands. Init files are not executed if you use the @samp{-nx}
1355 option (@pxref{Mode Options, ,Choosing Modes}).
1357 To display the list of init files loaded by gdb at startup, you
1358 can use @kbd{gdb --help}.
1360 @cindex init file name
1361 @cindex @file{.gdbinit}
1362 @cindex @file{gdb.ini}
1363 The @value{GDBN} init files are normally called @file{.gdbinit}.
1364 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1365 the limitations of file names imposed by DOS filesystems. The Windows
1366 port of @value{GDBN} uses the standard name, but if it finds a
1367 @file{gdb.ini} file in your home directory, it warns you about that
1368 and suggests to rename the file to the standard name.
1372 @section Quitting @value{GDBN}
1373 @cindex exiting @value{GDBN}
1374 @cindex leaving @value{GDBN}
1377 @kindex quit @r{[}@var{expression}@r{]}
1378 @kindex q @r{(@code{quit})}
1379 @item quit @r{[}@var{expression}@r{]}
1381 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1382 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1383 do not supply @var{expression}, @value{GDBN} will terminate normally;
1384 otherwise it will terminate using the result of @var{expression} as the
1389 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1390 terminates the action of any @value{GDBN} command that is in progress and
1391 returns to @value{GDBN} command level. It is safe to type the interrupt
1392 character at any time because @value{GDBN} does not allow it to take effect
1393 until a time when it is safe.
1395 If you have been using @value{GDBN} to control an attached process or
1396 device, you can release it with the @code{detach} command
1397 (@pxref{Attach, ,Debugging an Already-running Process}).
1399 @node Shell Commands
1400 @section Shell Commands
1402 If you need to execute occasional shell commands during your
1403 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1404 just use the @code{shell} command.
1409 @cindex shell escape
1410 @item shell @var{command-string}
1411 @itemx !@var{command-string}
1412 Invoke a standard shell to execute @var{command-string}.
1413 Note that no space is needed between @code{!} and @var{command-string}.
1414 If it exists, the environment variable @code{SHELL} determines which
1415 shell to run. Otherwise @value{GDBN} uses the default shell
1416 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1419 The utility @code{make} is often needed in development environments.
1420 You do not have to use the @code{shell} command for this purpose in
1425 @cindex calling make
1426 @item make @var{make-args}
1427 Execute the @code{make} program with the specified
1428 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1431 @node Logging Output
1432 @section Logging Output
1433 @cindex logging @value{GDBN} output
1434 @cindex save @value{GDBN} output to a file
1436 You may want to save the output of @value{GDBN} commands to a file.
1437 There are several commands to control @value{GDBN}'s logging.
1441 @item set logging on
1443 @item set logging off
1445 @cindex logging file name
1446 @item set logging file @var{file}
1447 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1448 @item set logging overwrite [on|off]
1449 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1450 you want @code{set logging on} to overwrite the logfile instead.
1451 @item set logging redirect [on|off]
1452 By default, @value{GDBN} output will go to both the terminal and the logfile.
1453 Set @code{redirect} if you want output to go only to the log file.
1454 @kindex show logging
1456 Show the current values of the logging settings.
1460 @chapter @value{GDBN} Commands
1462 You can abbreviate a @value{GDBN} command to the first few letters of the command
1463 name, if that abbreviation is unambiguous; and you can repeat certain
1464 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1465 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1466 show you the alternatives available, if there is more than one possibility).
1469 * Command Syntax:: How to give commands to @value{GDBN}
1470 * Completion:: Command completion
1471 * Help:: How to ask @value{GDBN} for help
1474 @node Command Syntax
1475 @section Command Syntax
1477 A @value{GDBN} command is a single line of input. There is no limit on
1478 how long it can be. It starts with a command name, which is followed by
1479 arguments whose meaning depends on the command name. For example, the
1480 command @code{step} accepts an argument which is the number of times to
1481 step, as in @samp{step 5}. You can also use the @code{step} command
1482 with no arguments. Some commands do not allow any arguments.
1484 @cindex abbreviation
1485 @value{GDBN} command names may always be truncated if that abbreviation is
1486 unambiguous. Other possible command abbreviations are listed in the
1487 documentation for individual commands. In some cases, even ambiguous
1488 abbreviations are allowed; for example, @code{s} is specially defined as
1489 equivalent to @code{step} even though there are other commands whose
1490 names start with @code{s}. You can test abbreviations by using them as
1491 arguments to the @code{help} command.
1493 @cindex repeating commands
1494 @kindex RET @r{(repeat last command)}
1495 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1496 repeat the previous command. Certain commands (for example, @code{run})
1497 will not repeat this way; these are commands whose unintentional
1498 repetition might cause trouble and which you are unlikely to want to
1499 repeat. User-defined commands can disable this feature; see
1500 @ref{Define, dont-repeat}.
1502 The @code{list} and @code{x} commands, when you repeat them with
1503 @key{RET}, construct new arguments rather than repeating
1504 exactly as typed. This permits easy scanning of source or memory.
1506 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1507 output, in a way similar to the common utility @code{more}
1508 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1509 @key{RET} too many in this situation, @value{GDBN} disables command
1510 repetition after any command that generates this sort of display.
1512 @kindex # @r{(a comment)}
1514 Any text from a @kbd{#} to the end of the line is a comment; it does
1515 nothing. This is useful mainly in command files (@pxref{Command
1516 Files,,Command Files}).
1518 @cindex repeating command sequences
1519 @kindex Ctrl-o @r{(operate-and-get-next)}
1520 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1521 commands. This command accepts the current line, like @key{RET}, and
1522 then fetches the next line relative to the current line from the history
1526 @section Command Completion
1529 @cindex word completion
1530 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1531 only one possibility; it can also show you what the valid possibilities
1532 are for the next word in a command, at any time. This works for @value{GDBN}
1533 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1535 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1536 of a word. If there is only one possibility, @value{GDBN} fills in the
1537 word, and waits for you to finish the command (or press @key{RET} to
1538 enter it). For example, if you type
1540 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1541 @c complete accuracy in these examples; space introduced for clarity.
1542 @c If texinfo enhancements make it unnecessary, it would be nice to
1543 @c replace " @key" by "@key" in the following...
1545 (@value{GDBP}) info bre @key{TAB}
1549 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1550 the only @code{info} subcommand beginning with @samp{bre}:
1553 (@value{GDBP}) info breakpoints
1557 You can either press @key{RET} at this point, to run the @code{info
1558 breakpoints} command, or backspace and enter something else, if
1559 @samp{breakpoints} does not look like the command you expected. (If you
1560 were sure you wanted @code{info breakpoints} in the first place, you
1561 might as well just type @key{RET} immediately after @samp{info bre},
1562 to exploit command abbreviations rather than command completion).
1564 If there is more than one possibility for the next word when you press
1565 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1566 characters and try again, or just press @key{TAB} a second time;
1567 @value{GDBN} displays all the possible completions for that word. For
1568 example, you might want to set a breakpoint on a subroutine whose name
1569 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1570 just sounds the bell. Typing @key{TAB} again displays all the
1571 function names in your program that begin with those characters, for
1575 (@value{GDBP}) b make_ @key{TAB}
1576 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1577 make_a_section_from_file make_environ
1578 make_abs_section make_function_type
1579 make_blockvector make_pointer_type
1580 make_cleanup make_reference_type
1581 make_command make_symbol_completion_list
1582 (@value{GDBP}) b make_
1586 After displaying the available possibilities, @value{GDBN} copies your
1587 partial input (@samp{b make_} in the example) so you can finish the
1590 If you just want to see the list of alternatives in the first place, you
1591 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1592 means @kbd{@key{META} ?}. You can type this either by holding down a
1593 key designated as the @key{META} shift on your keyboard (if there is
1594 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1596 If the number of possible completions is large, @value{GDBN} will
1597 print as much of the list as it has collected, as well as a message
1598 indicating that the list may be truncated.
1601 (@value{GDBP}) b m@key{TAB}@key{TAB}
1603 <... the rest of the possible completions ...>
1604 *** List may be truncated, max-completions reached. ***
1609 This behavior can be controlled with the following commands:
1612 @kindex set max-completions
1613 @item set max-completions @var{limit}
1614 @itemx set max-completions unlimited
1615 Set the maximum number of completion candidates. @value{GDBN} will
1616 stop looking for more completions once it collects this many candidates.
1617 This is useful when completing on things like function names as collecting
1618 all the possible candidates can be time consuming.
1619 The default value is 200. A value of zero disables tab-completion.
1620 Note that setting either no limit or a very large limit can make
1622 @kindex show max-completions
1623 @item show max-completions
1624 Show the maximum number of candidates that @value{GDBN} will collect and show
1628 @cindex quotes in commands
1629 @cindex completion of quoted strings
1630 Sometimes the string you need, while logically a ``word'', may contain
1631 parentheses or other characters that @value{GDBN} normally excludes from
1632 its notion of a word. To permit word completion to work in this
1633 situation, you may enclose words in @code{'} (single quote marks) in
1634 @value{GDBN} commands.
1636 The most likely situation where you might need this is in typing the
1637 name of a C@t{++} function. This is because C@t{++} allows function
1638 overloading (multiple definitions of the same function, distinguished
1639 by argument type). For example, when you want to set a breakpoint you
1640 may need to distinguish whether you mean the version of @code{name}
1641 that takes an @code{int} parameter, @code{name(int)}, or the version
1642 that takes a @code{float} parameter, @code{name(float)}. To use the
1643 word-completion facilities in this situation, type a single quote
1644 @code{'} at the beginning of the function name. This alerts
1645 @value{GDBN} that it may need to consider more information than usual
1646 when you press @key{TAB} or @kbd{M-?} to request word completion:
1649 (@value{GDBP}) b 'bubble( @kbd{M-?}
1650 bubble(double,double) bubble(int,int)
1651 (@value{GDBP}) b 'bubble(
1654 In some cases, @value{GDBN} can tell that completing a name requires using
1655 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1656 completing as much as it can) if you do not type the quote in the first
1660 (@value{GDBP}) b bub @key{TAB}
1661 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1662 (@value{GDBP}) b 'bubble(
1666 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1667 you have not yet started typing the argument list when you ask for
1668 completion on an overloaded symbol.
1670 For more information about overloaded functions, see @ref{C Plus Plus
1671 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1672 overload-resolution off} to disable overload resolution;
1673 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1675 @cindex completion of structure field names
1676 @cindex structure field name completion
1677 @cindex completion of union field names
1678 @cindex union field name completion
1679 When completing in an expression which looks up a field in a
1680 structure, @value{GDBN} also tries@footnote{The completer can be
1681 confused by certain kinds of invalid expressions. Also, it only
1682 examines the static type of the expression, not the dynamic type.} to
1683 limit completions to the field names available in the type of the
1687 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1688 magic to_fputs to_rewind
1689 to_data to_isatty to_write
1690 to_delete to_put to_write_async_safe
1695 This is because the @code{gdb_stdout} is a variable of the type
1696 @code{struct ui_file} that is defined in @value{GDBN} sources as
1703 ui_file_flush_ftype *to_flush;
1704 ui_file_write_ftype *to_write;
1705 ui_file_write_async_safe_ftype *to_write_async_safe;
1706 ui_file_fputs_ftype *to_fputs;
1707 ui_file_read_ftype *to_read;
1708 ui_file_delete_ftype *to_delete;
1709 ui_file_isatty_ftype *to_isatty;
1710 ui_file_rewind_ftype *to_rewind;
1711 ui_file_put_ftype *to_put;
1718 @section Getting Help
1719 @cindex online documentation
1722 You can always ask @value{GDBN} itself for information on its commands,
1723 using the command @code{help}.
1726 @kindex h @r{(@code{help})}
1729 You can use @code{help} (abbreviated @code{h}) with no arguments to
1730 display a short list of named classes of commands:
1734 List of classes of commands:
1736 aliases -- Aliases of other commands
1737 breakpoints -- Making program stop at certain points
1738 data -- Examining data
1739 files -- Specifying and examining files
1740 internals -- Maintenance commands
1741 obscure -- Obscure features
1742 running -- Running the program
1743 stack -- Examining the stack
1744 status -- Status inquiries
1745 support -- Support facilities
1746 tracepoints -- Tracing of program execution without
1747 stopping the program
1748 user-defined -- User-defined commands
1750 Type "help" followed by a class name for a list of
1751 commands in that class.
1752 Type "help" followed by command name for full
1754 Command name abbreviations are allowed if unambiguous.
1757 @c the above line break eliminates huge line overfull...
1759 @item help @var{class}
1760 Using one of the general help classes as an argument, you can get a
1761 list of the individual commands in that class. For example, here is the
1762 help display for the class @code{status}:
1765 (@value{GDBP}) help status
1770 @c Line break in "show" line falsifies real output, but needed
1771 @c to fit in smallbook page size.
1772 info -- Generic command for showing things
1773 about the program being debugged
1774 show -- Generic command for showing things
1777 Type "help" followed by command name for full
1779 Command name abbreviations are allowed if unambiguous.
1783 @item help @var{command}
1784 With a command name as @code{help} argument, @value{GDBN} displays a
1785 short paragraph on how to use that command.
1788 @item apropos @var{args}
1789 The @code{apropos} command searches through all of the @value{GDBN}
1790 commands, and their documentation, for the regular expression specified in
1791 @var{args}. It prints out all matches found. For example:
1802 alias -- Define a new command that is an alias of an existing command
1803 aliases -- Aliases of other commands
1804 d -- Delete some breakpoints or auto-display expressions
1805 del -- Delete some breakpoints or auto-display expressions
1806 delete -- Delete some breakpoints or auto-display expressions
1811 @item complete @var{args}
1812 The @code{complete @var{args}} command lists all the possible completions
1813 for the beginning of a command. Use @var{args} to specify the beginning of the
1814 command you want completed. For example:
1820 @noindent results in:
1831 @noindent This is intended for use by @sc{gnu} Emacs.
1834 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1835 and @code{show} to inquire about the state of your program, or the state
1836 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1837 manual introduces each of them in the appropriate context. The listings
1838 under @code{info} and under @code{show} in the Command, Variable, and
1839 Function Index point to all the sub-commands. @xref{Command and Variable
1845 @kindex i @r{(@code{info})}
1847 This command (abbreviated @code{i}) is for describing the state of your
1848 program. For example, you can show the arguments passed to a function
1849 with @code{info args}, list the registers currently in use with @code{info
1850 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1851 You can get a complete list of the @code{info} sub-commands with
1852 @w{@code{help info}}.
1856 You can assign the result of an expression to an environment variable with
1857 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1858 @code{set prompt $}.
1862 In contrast to @code{info}, @code{show} is for describing the state of
1863 @value{GDBN} itself.
1864 You can change most of the things you can @code{show}, by using the
1865 related command @code{set}; for example, you can control what number
1866 system is used for displays with @code{set radix}, or simply inquire
1867 which is currently in use with @code{show radix}.
1870 To display all the settable parameters and their current
1871 values, you can use @code{show} with no arguments; you may also use
1872 @code{info set}. Both commands produce the same display.
1873 @c FIXME: "info set" violates the rule that "info" is for state of
1874 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1875 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1879 Here are several miscellaneous @code{show} subcommands, all of which are
1880 exceptional in lacking corresponding @code{set} commands:
1883 @kindex show version
1884 @cindex @value{GDBN} version number
1886 Show what version of @value{GDBN} is running. You should include this
1887 information in @value{GDBN} bug-reports. If multiple versions of
1888 @value{GDBN} are in use at your site, you may need to determine which
1889 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1890 commands are introduced, and old ones may wither away. Also, many
1891 system vendors ship variant versions of @value{GDBN}, and there are
1892 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1893 The version number is the same as the one announced when you start
1896 @kindex show copying
1897 @kindex info copying
1898 @cindex display @value{GDBN} copyright
1901 Display information about permission for copying @value{GDBN}.
1903 @kindex show warranty
1904 @kindex info warranty
1906 @itemx info warranty
1907 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1908 if your version of @value{GDBN} comes with one.
1910 @kindex show configuration
1911 @item show configuration
1912 Display detailed information about the way @value{GDBN} was configured
1913 when it was built. This displays the optional arguments passed to the
1914 @file{configure} script and also configuration parameters detected
1915 automatically by @command{configure}. When reporting a @value{GDBN}
1916 bug (@pxref{GDB Bugs}), it is important to include this information in
1922 @chapter Running Programs Under @value{GDBN}
1924 When you run a program under @value{GDBN}, you must first generate
1925 debugging information when you compile it.
1927 You may start @value{GDBN} with its arguments, if any, in an environment
1928 of your choice. If you are doing native debugging, you may redirect
1929 your program's input and output, debug an already running process, or
1930 kill a child process.
1933 * Compilation:: Compiling for debugging
1934 * Starting:: Starting your program
1935 * Arguments:: Your program's arguments
1936 * Environment:: Your program's environment
1938 * Working Directory:: Your program's working directory
1939 * Input/Output:: Your program's input and output
1940 * Attach:: Debugging an already-running process
1941 * Kill Process:: Killing the child process
1943 * Inferiors and Programs:: Debugging multiple inferiors and programs
1944 * Threads:: Debugging programs with multiple threads
1945 * Forks:: Debugging forks
1946 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1950 @section Compiling for Debugging
1952 In order to debug a program effectively, you need to generate
1953 debugging information when you compile it. This debugging information
1954 is stored in the object file; it describes the data type of each
1955 variable or function and the correspondence between source line numbers
1956 and addresses in the executable code.
1958 To request debugging information, specify the @samp{-g} option when you run
1961 Programs that are to be shipped to your customers are compiled with
1962 optimizations, using the @samp{-O} compiler option. However, some
1963 compilers are unable to handle the @samp{-g} and @samp{-O} options
1964 together. Using those compilers, you cannot generate optimized
1965 executables containing debugging information.
1967 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1968 without @samp{-O}, making it possible to debug optimized code. We
1969 recommend that you @emph{always} use @samp{-g} whenever you compile a
1970 program. You may think your program is correct, but there is no sense
1971 in pushing your luck. For more information, see @ref{Optimized Code}.
1973 Older versions of the @sc{gnu} C compiler permitted a variant option
1974 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1975 format; if your @sc{gnu} C compiler has this option, do not use it.
1977 @value{GDBN} knows about preprocessor macros and can show you their
1978 expansion (@pxref{Macros}). Most compilers do not include information
1979 about preprocessor macros in the debugging information if you specify
1980 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1981 the @sc{gnu} C compiler, provides macro information if you are using
1982 the DWARF debugging format, and specify the option @option{-g3}.
1984 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1985 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1986 information on @value{NGCC} options affecting debug information.
1988 You will have the best debugging experience if you use the latest
1989 version of the DWARF debugging format that your compiler supports.
1990 DWARF is currently the most expressive and best supported debugging
1991 format in @value{GDBN}.
1995 @section Starting your Program
2001 @kindex r @r{(@code{run})}
2004 Use the @code{run} command to start your program under @value{GDBN}.
2005 You must first specify the program name with an argument to
2006 @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
2007 @value{GDBN}}), or by using the @code{file} or @code{exec-file}
2008 command (@pxref{Files, ,Commands to Specify Files}).
2012 If you are running your program in an execution environment that
2013 supports processes, @code{run} creates an inferior process and makes
2014 that process run your program. In some environments without processes,
2015 @code{run} jumps to the start of your program. Other targets,
2016 like @samp{remote}, are always running. If you get an error
2017 message like this one:
2020 The "remote" target does not support "run".
2021 Try "help target" or "continue".
2025 then use @code{continue} to run your program. You may need @code{load}
2026 first (@pxref{load}).
2028 The execution of a program is affected by certain information it
2029 receives from its superior. @value{GDBN} provides ways to specify this
2030 information, which you must do @emph{before} starting your program. (You
2031 can change it after starting your program, but such changes only affect
2032 your program the next time you start it.) This information may be
2033 divided into four categories:
2036 @item The @emph{arguments.}
2037 Specify the arguments to give your program as the arguments of the
2038 @code{run} command. If a shell is available on your target, the shell
2039 is used to pass the arguments, so that you may use normal conventions
2040 (such as wildcard expansion or variable substitution) in describing
2042 In Unix systems, you can control which shell is used with the
2043 @code{SHELL} environment variable. If you do not define @code{SHELL},
2044 @value{GDBN} uses the default shell (@file{/bin/sh}). You can disable
2045 use of any shell with the @code{set startup-with-shell} command (see
2048 @item The @emph{environment.}
2049 Your program normally inherits its environment from @value{GDBN}, but you can
2050 use the @value{GDBN} commands @code{set environment} and @code{unset
2051 environment} to change parts of the environment that affect
2052 your program. @xref{Environment, ,Your Program's Environment}.
2054 @item The @emph{working directory.}
2055 Your program inherits its working directory from @value{GDBN}. You can set
2056 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2057 @xref{Working Directory, ,Your Program's Working Directory}.
2059 @item The @emph{standard input and output.}
2060 Your program normally uses the same device for standard input and
2061 standard output as @value{GDBN} is using. You can redirect input and output
2062 in the @code{run} command line, or you can use the @code{tty} command to
2063 set a different device for your program.
2064 @xref{Input/Output, ,Your Program's Input and Output}.
2067 @emph{Warning:} While input and output redirection work, you cannot use
2068 pipes to pass the output of the program you are debugging to another
2069 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2073 When you issue the @code{run} command, your program begins to execute
2074 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2075 of how to arrange for your program to stop. Once your program has
2076 stopped, you may call functions in your program, using the @code{print}
2077 or @code{call} commands. @xref{Data, ,Examining Data}.
2079 If the modification time of your symbol file has changed since the last
2080 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2081 table, and reads it again. When it does this, @value{GDBN} tries to retain
2082 your current breakpoints.
2087 @cindex run to main procedure
2088 The name of the main procedure can vary from language to language.
2089 With C or C@t{++}, the main procedure name is always @code{main}, but
2090 other languages such as Ada do not require a specific name for their
2091 main procedure. The debugger provides a convenient way to start the
2092 execution of the program and to stop at the beginning of the main
2093 procedure, depending on the language used.
2095 The @samp{start} command does the equivalent of setting a temporary
2096 breakpoint at the beginning of the main procedure and then invoking
2097 the @samp{run} command.
2099 @cindex elaboration phase
2100 Some programs contain an @dfn{elaboration} phase where some startup code is
2101 executed before the main procedure is called. This depends on the
2102 languages used to write your program. In C@t{++}, for instance,
2103 constructors for static and global objects are executed before
2104 @code{main} is called. It is therefore possible that the debugger stops
2105 before reaching the main procedure. However, the temporary breakpoint
2106 will remain to halt execution.
2108 Specify the arguments to give to your program as arguments to the
2109 @samp{start} command. These arguments will be given verbatim to the
2110 underlying @samp{run} command. Note that the same arguments will be
2111 reused if no argument is provided during subsequent calls to
2112 @samp{start} or @samp{run}.
2114 It is sometimes necessary to debug the program during elaboration. In
2115 these cases, using the @code{start} command would stop the execution of
2116 your program too late, as the program would have already completed the
2117 elaboration phase. Under these circumstances, insert breakpoints in your
2118 elaboration code before running your program.
2120 @anchor{set exec-wrapper}
2121 @kindex set exec-wrapper
2122 @item set exec-wrapper @var{wrapper}
2123 @itemx show exec-wrapper
2124 @itemx unset exec-wrapper
2125 When @samp{exec-wrapper} is set, the specified wrapper is used to
2126 launch programs for debugging. @value{GDBN} starts your program
2127 with a shell command of the form @kbd{exec @var{wrapper}
2128 @var{program}}. Quoting is added to @var{program} and its
2129 arguments, but not to @var{wrapper}, so you should add quotes if
2130 appropriate for your shell. The wrapper runs until it executes
2131 your program, and then @value{GDBN} takes control.
2133 You can use any program that eventually calls @code{execve} with
2134 its arguments as a wrapper. Several standard Unix utilities do
2135 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2136 with @code{exec "$@@"} will also work.
2138 For example, you can use @code{env} to pass an environment variable to
2139 the debugged program, without setting the variable in your shell's
2143 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2147 This command is available when debugging locally on most targets, excluding
2148 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2150 @kindex set startup-with-shell
2151 @item set startup-with-shell
2152 @itemx set startup-with-shell on
2153 @itemx set startup-with-shell off
2154 @itemx show set startup-with-shell
2155 On Unix systems, by default, if a shell is available on your target,
2156 @value{GDBN}) uses it to start your program. Arguments of the
2157 @code{run} command are passed to the shell, which does variable
2158 substitution, expands wildcard characters and performs redirection of
2159 I/O. In some circumstances, it may be useful to disable such use of a
2160 shell, for example, when debugging the shell itself or diagnosing
2161 startup failures such as:
2165 Starting program: ./a.out
2166 During startup program terminated with signal SIGSEGV, Segmentation fault.
2170 which indicates the shell or the wrapper specified with
2171 @samp{exec-wrapper} crashed, not your program. Most often, this is
2172 caused by something odd in your shell's non-interactive mode
2173 initialization file---such as @file{.cshrc} for C-shell,
2174 $@file{.zshenv} for the Z shell, or the file specified in the
2175 @samp{BASH_ENV} environment variable for BASH.
2177 @anchor{set auto-connect-native-target}
2178 @kindex set auto-connect-native-target
2179 @item set auto-connect-native-target
2180 @itemx set auto-connect-native-target on
2181 @itemx set auto-connect-native-target off
2182 @itemx show auto-connect-native-target
2184 By default, if not connected to any target yet (e.g., with
2185 @code{target remote}), the @code{run} command starts your program as a
2186 native process under @value{GDBN}, on your local machine. If you're
2187 sure you don't want to debug programs on your local machine, you can
2188 tell @value{GDBN} to not connect to the native target automatically
2189 with the @code{set auto-connect-native-target off} command.
2191 If @code{on}, which is the default, and if @value{GDBN} is not
2192 connected to a target already, the @code{run} command automaticaly
2193 connects to the native target, if one is available.
2195 If @code{off}, and if @value{GDBN} is not connected to a target
2196 already, the @code{run} command fails with an error:
2200 Don't know how to run. Try "help target".
2203 If @value{GDBN} is already connected to a target, @value{GDBN} always
2204 uses it with the @code{run} command.
2206 In any case, you can explicitly connect to the native target with the
2207 @code{target native} command. For example,
2210 (@value{GDBP}) set auto-connect-native-target off
2212 Don't know how to run. Try "help target".
2213 (@value{GDBP}) target native
2215 Starting program: ./a.out
2216 [Inferior 1 (process 10421) exited normally]
2219 In case you connected explicitly to the @code{native} target,
2220 @value{GDBN} remains connected even if all inferiors exit, ready for
2221 the next @code{run} command. Use the @code{disconnect} command to
2224 Examples of other commands that likewise respect the
2225 @code{auto-connect-native-target} setting: @code{attach}, @code{info
2226 proc}, @code{info os}.
2228 @kindex set disable-randomization
2229 @item set disable-randomization
2230 @itemx set disable-randomization on
2231 This option (enabled by default in @value{GDBN}) will turn off the native
2232 randomization of the virtual address space of the started program. This option
2233 is useful for multiple debugging sessions to make the execution better
2234 reproducible and memory addresses reusable across debugging sessions.
2236 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2237 On @sc{gnu}/Linux you can get the same behavior using
2240 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2243 @item set disable-randomization off
2244 Leave the behavior of the started executable unchanged. Some bugs rear their
2245 ugly heads only when the program is loaded at certain addresses. If your bug
2246 disappears when you run the program under @value{GDBN}, that might be because
2247 @value{GDBN} by default disables the address randomization on platforms, such
2248 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2249 disable-randomization off} to try to reproduce such elusive bugs.
2251 On targets where it is available, virtual address space randomization
2252 protects the programs against certain kinds of security attacks. In these
2253 cases the attacker needs to know the exact location of a concrete executable
2254 code. Randomizing its location makes it impossible to inject jumps misusing
2255 a code at its expected addresses.
2257 Prelinking shared libraries provides a startup performance advantage but it
2258 makes addresses in these libraries predictable for privileged processes by
2259 having just unprivileged access at the target system. Reading the shared
2260 library binary gives enough information for assembling the malicious code
2261 misusing it. Still even a prelinked shared library can get loaded at a new
2262 random address just requiring the regular relocation process during the
2263 startup. Shared libraries not already prelinked are always loaded at
2264 a randomly chosen address.
2266 Position independent executables (PIE) contain position independent code
2267 similar to the shared libraries and therefore such executables get loaded at
2268 a randomly chosen address upon startup. PIE executables always load even
2269 already prelinked shared libraries at a random address. You can build such
2270 executable using @command{gcc -fPIE -pie}.
2272 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2273 (as long as the randomization is enabled).
2275 @item show disable-randomization
2276 Show the current setting of the explicit disable of the native randomization of
2277 the virtual address space of the started program.
2282 @section Your Program's Arguments
2284 @cindex arguments (to your program)
2285 The arguments to your program can be specified by the arguments of the
2287 They are passed to a shell, which expands wildcard characters and
2288 performs redirection of I/O, and thence to your program. Your
2289 @code{SHELL} environment variable (if it exists) specifies what shell
2290 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2291 the default shell (@file{/bin/sh} on Unix).
2293 On non-Unix systems, the program is usually invoked directly by
2294 @value{GDBN}, which emulates I/O redirection via the appropriate system
2295 calls, and the wildcard characters are expanded by the startup code of
2296 the program, not by the shell.
2298 @code{run} with no arguments uses the same arguments used by the previous
2299 @code{run}, or those set by the @code{set args} command.
2304 Specify the arguments to be used the next time your program is run. If
2305 @code{set args} has no arguments, @code{run} executes your program
2306 with no arguments. Once you have run your program with arguments,
2307 using @code{set args} before the next @code{run} is the only way to run
2308 it again without arguments.
2312 Show the arguments to give your program when it is started.
2316 @section Your Program's Environment
2318 @cindex environment (of your program)
2319 The @dfn{environment} consists of a set of environment variables and
2320 their values. Environment variables conventionally record such things as
2321 your user name, your home directory, your terminal type, and your search
2322 path for programs to run. Usually you set up environment variables with
2323 the shell and they are inherited by all the other programs you run. When
2324 debugging, it can be useful to try running your program with a modified
2325 environment without having to start @value{GDBN} over again.
2329 @item path @var{directory}
2330 Add @var{directory} to the front of the @code{PATH} environment variable
2331 (the search path for executables) that will be passed to your program.
2332 The value of @code{PATH} used by @value{GDBN} does not change.
2333 You may specify several directory names, separated by whitespace or by a
2334 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2335 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2336 is moved to the front, so it is searched sooner.
2338 You can use the string @samp{$cwd} to refer to whatever is the current
2339 working directory at the time @value{GDBN} searches the path. If you
2340 use @samp{.} instead, it refers to the directory where you executed the
2341 @code{path} command. @value{GDBN} replaces @samp{.} in the
2342 @var{directory} argument (with the current path) before adding
2343 @var{directory} to the search path.
2344 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2345 @c document that, since repeating it would be a no-op.
2349 Display the list of search paths for executables (the @code{PATH}
2350 environment variable).
2352 @kindex show environment
2353 @item show environment @r{[}@var{varname}@r{]}
2354 Print the value of environment variable @var{varname} to be given to
2355 your program when it starts. If you do not supply @var{varname},
2356 print the names and values of all environment variables to be given to
2357 your program. You can abbreviate @code{environment} as @code{env}.
2359 @kindex set environment
2360 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2361 Set environment variable @var{varname} to @var{value}. The value
2362 changes for your program (and the shell @value{GDBN} uses to launch
2363 it), not for @value{GDBN} itself. The @var{value} may be any string; the
2364 values of environment variables are just strings, and any
2365 interpretation is supplied by your program itself. The @var{value}
2366 parameter is optional; if it is eliminated, the variable is set to a
2368 @c "any string" here does not include leading, trailing
2369 @c blanks. Gnu asks: does anyone care?
2371 For example, this command:
2378 tells the debugged program, when subsequently run, that its user is named
2379 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2380 are not actually required.)
2382 Note that on Unix systems, @value{GDBN} runs your program via a shell,
2383 which also inherits the environment set with @code{set environment}.
2384 If necessary, you can avoid that by using the @samp{env} program as a
2385 wrapper instead of using @code{set environment}. @xref{set
2386 exec-wrapper}, for an example doing just that.
2388 @kindex unset environment
2389 @item unset environment @var{varname}
2390 Remove variable @var{varname} from the environment to be passed to your
2391 program. This is different from @samp{set env @var{varname} =};
2392 @code{unset environment} removes the variable from the environment,
2393 rather than assigning it an empty value.
2396 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2397 the shell indicated by your @code{SHELL} environment variable if it
2398 exists (or @code{/bin/sh} if not). If your @code{SHELL} variable
2399 names a shell that runs an initialization file when started
2400 non-interactively---such as @file{.cshrc} for C-shell, $@file{.zshenv}
2401 for the Z shell, or the file specified in the @samp{BASH_ENV}
2402 environment variable for BASH---any variables you set in that file
2403 affect your program. You may wish to move setting of environment
2404 variables to files that are only run when you sign on, such as
2405 @file{.login} or @file{.profile}.
2407 @node Working Directory
2408 @section Your Program's Working Directory
2410 @cindex working directory (of your program)
2411 Each time you start your program with @code{run}, it inherits its
2412 working directory from the current working directory of @value{GDBN}.
2413 The @value{GDBN} working directory is initially whatever it inherited
2414 from its parent process (typically the shell), but you can specify a new
2415 working directory in @value{GDBN} with the @code{cd} command.
2417 The @value{GDBN} working directory also serves as a default for the commands
2418 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2423 @cindex change working directory
2424 @item cd @r{[}@var{directory}@r{]}
2425 Set the @value{GDBN} working directory to @var{directory}. If not
2426 given, @var{directory} uses @file{'~'}.
2430 Print the @value{GDBN} working directory.
2433 It is generally impossible to find the current working directory of
2434 the process being debugged (since a program can change its directory
2435 during its run). If you work on a system where @value{GDBN} is
2436 configured with the @file{/proc} support, you can use the @code{info
2437 proc} command (@pxref{SVR4 Process Information}) to find out the
2438 current working directory of the debuggee.
2441 @section Your Program's Input and Output
2446 By default, the program you run under @value{GDBN} does input and output to
2447 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2448 to its own terminal modes to interact with you, but it records the terminal
2449 modes your program was using and switches back to them when you continue
2450 running your program.
2453 @kindex info terminal
2455 Displays information recorded by @value{GDBN} about the terminal modes your
2459 You can redirect your program's input and/or output using shell
2460 redirection with the @code{run} command. For example,
2467 starts your program, diverting its output to the file @file{outfile}.
2470 @cindex controlling terminal
2471 Another way to specify where your program should do input and output is
2472 with the @code{tty} command. This command accepts a file name as
2473 argument, and causes this file to be the default for future @code{run}
2474 commands. It also resets the controlling terminal for the child
2475 process, for future @code{run} commands. For example,
2482 directs that processes started with subsequent @code{run} commands
2483 default to do input and output on the terminal @file{/dev/ttyb} and have
2484 that as their controlling terminal.
2486 An explicit redirection in @code{run} overrides the @code{tty} command's
2487 effect on the input/output device, but not its effect on the controlling
2490 When you use the @code{tty} command or redirect input in the @code{run}
2491 command, only the input @emph{for your program} is affected. The input
2492 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2493 for @code{set inferior-tty}.
2495 @cindex inferior tty
2496 @cindex set inferior controlling terminal
2497 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2498 display the name of the terminal that will be used for future runs of your
2502 @item set inferior-tty /dev/ttyb
2503 @kindex set inferior-tty
2504 Set the tty for the program being debugged to /dev/ttyb.
2506 @item show inferior-tty
2507 @kindex show inferior-tty
2508 Show the current tty for the program being debugged.
2512 @section Debugging an Already-running Process
2517 @item attach @var{process-id}
2518 This command attaches to a running process---one that was started
2519 outside @value{GDBN}. (@code{info files} shows your active
2520 targets.) The command takes as argument a process ID. The usual way to
2521 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2522 or with the @samp{jobs -l} shell command.
2524 @code{attach} does not repeat if you press @key{RET} a second time after
2525 executing the command.
2528 To use @code{attach}, your program must be running in an environment
2529 which supports processes; for example, @code{attach} does not work for
2530 programs on bare-board targets that lack an operating system. You must
2531 also have permission to send the process a signal.
2533 When you use @code{attach}, the debugger finds the program running in
2534 the process first by looking in the current working directory, then (if
2535 the program is not found) by using the source file search path
2536 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2537 the @code{file} command to load the program. @xref{Files, ,Commands to
2540 The first thing @value{GDBN} does after arranging to debug the specified
2541 process is to stop it. You can examine and modify an attached process
2542 with all the @value{GDBN} commands that are ordinarily available when
2543 you start processes with @code{run}. You can insert breakpoints; you
2544 can step and continue; you can modify storage. If you would rather the
2545 process continue running, you may use the @code{continue} command after
2546 attaching @value{GDBN} to the process.
2551 When you have finished debugging the attached process, you can use the
2552 @code{detach} command to release it from @value{GDBN} control. Detaching
2553 the process continues its execution. After the @code{detach} command,
2554 that process and @value{GDBN} become completely independent once more, and you
2555 are ready to @code{attach} another process or start one with @code{run}.
2556 @code{detach} does not repeat if you press @key{RET} again after
2557 executing the command.
2560 If you exit @value{GDBN} while you have an attached process, you detach
2561 that process. If you use the @code{run} command, you kill that process.
2562 By default, @value{GDBN} asks for confirmation if you try to do either of these
2563 things; you can control whether or not you need to confirm by using the
2564 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2568 @section Killing the Child Process
2573 Kill the child process in which your program is running under @value{GDBN}.
2576 This command is useful if you wish to debug a core dump instead of a
2577 running process. @value{GDBN} ignores any core dump file while your program
2580 On some operating systems, a program cannot be executed outside @value{GDBN}
2581 while you have breakpoints set on it inside @value{GDBN}. You can use the
2582 @code{kill} command in this situation to permit running your program
2583 outside the debugger.
2585 The @code{kill} command is also useful if you wish to recompile and
2586 relink your program, since on many systems it is impossible to modify an
2587 executable file while it is running in a process. In this case, when you
2588 next type @code{run}, @value{GDBN} notices that the file has changed, and
2589 reads the symbol table again (while trying to preserve your current
2590 breakpoint settings).
2592 @node Inferiors and Programs
2593 @section Debugging Multiple Inferiors and Programs
2595 @value{GDBN} lets you run and debug multiple programs in a single
2596 session. In addition, @value{GDBN} on some systems may let you run
2597 several programs simultaneously (otherwise you have to exit from one
2598 before starting another). In the most general case, you can have
2599 multiple threads of execution in each of multiple processes, launched
2600 from multiple executables.
2603 @value{GDBN} represents the state of each program execution with an
2604 object called an @dfn{inferior}. An inferior typically corresponds to
2605 a process, but is more general and applies also to targets that do not
2606 have processes. Inferiors may be created before a process runs, and
2607 may be retained after a process exits. Inferiors have unique
2608 identifiers that are different from process ids. Usually each
2609 inferior will also have its own distinct address space, although some
2610 embedded targets may have several inferiors running in different parts
2611 of a single address space. Each inferior may in turn have multiple
2612 threads running in it.
2614 To find out what inferiors exist at any moment, use @w{@code{info
2618 @kindex info inferiors
2619 @item info inferiors
2620 Print a list of all inferiors currently being managed by @value{GDBN}.
2622 @value{GDBN} displays for each inferior (in this order):
2626 the inferior number assigned by @value{GDBN}
2629 the target system's inferior identifier
2632 the name of the executable the inferior is running.
2637 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2638 indicates the current inferior.
2642 @c end table here to get a little more width for example
2645 (@value{GDBP}) info inferiors
2646 Num Description Executable
2647 2 process 2307 hello
2648 * 1 process 3401 goodbye
2651 To switch focus between inferiors, use the @code{inferior} command:
2654 @kindex inferior @var{infno}
2655 @item inferior @var{infno}
2656 Make inferior number @var{infno} the current inferior. The argument
2657 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2658 in the first field of the @samp{info inferiors} display.
2661 @vindex $_inferior@r{, convenience variable}
2662 The debugger convenience variable @samp{$_inferior} contains the
2663 number of the current inferior. You may find this useful in writing
2664 breakpoint conditional expressions, command scripts, and so forth.
2665 @xref{Convenience Vars,, Convenience Variables}, for general
2666 information on convenience variables.
2668 You can get multiple executables into a debugging session via the
2669 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2670 systems @value{GDBN} can add inferiors to the debug session
2671 automatically by following calls to @code{fork} and @code{exec}. To
2672 remove inferiors from the debugging session use the
2673 @w{@code{remove-inferiors}} command.
2676 @kindex add-inferior
2677 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2678 Adds @var{n} inferiors to be run using @var{executable} as the
2679 executable; @var{n} defaults to 1. If no executable is specified,
2680 the inferiors begins empty, with no program. You can still assign or
2681 change the program assigned to the inferior at any time by using the
2682 @code{file} command with the executable name as its argument.
2684 @kindex clone-inferior
2685 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2686 Adds @var{n} inferiors ready to execute the same program as inferior
2687 @var{infno}; @var{n} defaults to 1, and @var{infno} defaults to the
2688 number of the current inferior. This is a convenient command when you
2689 want to run another instance of the inferior you are debugging.
2692 (@value{GDBP}) info inferiors
2693 Num Description Executable
2694 * 1 process 29964 helloworld
2695 (@value{GDBP}) clone-inferior
2698 (@value{GDBP}) info inferiors
2699 Num Description Executable
2701 * 1 process 29964 helloworld
2704 You can now simply switch focus to inferior 2 and run it.
2706 @kindex remove-inferiors
2707 @item remove-inferiors @var{infno}@dots{}
2708 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2709 possible to remove an inferior that is running with this command. For
2710 those, use the @code{kill} or @code{detach} command first.
2714 To quit debugging one of the running inferiors that is not the current
2715 inferior, you can either detach from it by using the @w{@code{detach
2716 inferior}} command (allowing it to run independently), or kill it
2717 using the @w{@code{kill inferiors}} command:
2720 @kindex detach inferiors @var{infno}@dots{}
2721 @item detach inferior @var{infno}@dots{}
2722 Detach from the inferior or inferiors identified by @value{GDBN}
2723 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2724 still stays on the list of inferiors shown by @code{info inferiors},
2725 but its Description will show @samp{<null>}.
2727 @kindex kill inferiors @var{infno}@dots{}
2728 @item kill inferiors @var{infno}@dots{}
2729 Kill the inferior or inferiors identified by @value{GDBN} inferior
2730 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2731 stays on the list of inferiors shown by @code{info inferiors}, but its
2732 Description will show @samp{<null>}.
2735 After the successful completion of a command such as @code{detach},
2736 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2737 a normal process exit, the inferior is still valid and listed with
2738 @code{info inferiors}, ready to be restarted.
2741 To be notified when inferiors are started or exit under @value{GDBN}'s
2742 control use @w{@code{set print inferior-events}}:
2745 @kindex set print inferior-events
2746 @cindex print messages on inferior start and exit
2747 @item set print inferior-events
2748 @itemx set print inferior-events on
2749 @itemx set print inferior-events off
2750 The @code{set print inferior-events} command allows you to enable or
2751 disable printing of messages when @value{GDBN} notices that new
2752 inferiors have started or that inferiors have exited or have been
2753 detached. By default, these messages will not be printed.
2755 @kindex show print inferior-events
2756 @item show print inferior-events
2757 Show whether messages will be printed when @value{GDBN} detects that
2758 inferiors have started, exited or have been detached.
2761 Many commands will work the same with multiple programs as with a
2762 single program: e.g., @code{print myglobal} will simply display the
2763 value of @code{myglobal} in the current inferior.
2766 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2767 get more info about the relationship of inferiors, programs, address
2768 spaces in a debug session. You can do that with the @w{@code{maint
2769 info program-spaces}} command.
2772 @kindex maint info program-spaces
2773 @item maint info program-spaces
2774 Print a list of all program spaces currently being managed by
2777 @value{GDBN} displays for each program space (in this order):
2781 the program space number assigned by @value{GDBN}
2784 the name of the executable loaded into the program space, with e.g.,
2785 the @code{file} command.
2790 An asterisk @samp{*} preceding the @value{GDBN} program space number
2791 indicates the current program space.
2793 In addition, below each program space line, @value{GDBN} prints extra
2794 information that isn't suitable to display in tabular form. For
2795 example, the list of inferiors bound to the program space.
2798 (@value{GDBP}) maint info program-spaces
2802 Bound inferiors: ID 1 (process 21561)
2805 Here we can see that no inferior is running the program @code{hello},
2806 while @code{process 21561} is running the program @code{goodbye}. On
2807 some targets, it is possible that multiple inferiors are bound to the
2808 same program space. The most common example is that of debugging both
2809 the parent and child processes of a @code{vfork} call. For example,
2812 (@value{GDBP}) maint info program-spaces
2815 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2818 Here, both inferior 2 and inferior 1 are running in the same program
2819 space as a result of inferior 1 having executed a @code{vfork} call.
2823 @section Debugging Programs with Multiple Threads
2825 @cindex threads of execution
2826 @cindex multiple threads
2827 @cindex switching threads
2828 In some operating systems, such as GNU/Linux and Solaris, a single program
2829 may have more than one @dfn{thread} of execution. The precise semantics
2830 of threads differ from one operating system to another, but in general
2831 the threads of a single program are akin to multiple processes---except
2832 that they share one address space (that is, they can all examine and
2833 modify the same variables). On the other hand, each thread has its own
2834 registers and execution stack, and perhaps private memory.
2836 @value{GDBN} provides these facilities for debugging multi-thread
2840 @item automatic notification of new threads
2841 @item @samp{thread @var{thread-id}}, a command to switch among threads
2842 @item @samp{info threads}, a command to inquire about existing threads
2843 @item @samp{thread apply [@var{thread-id-list}] [@var{all}] @var{args}},
2844 a command to apply a command to a list of threads
2845 @item thread-specific breakpoints
2846 @item @samp{set print thread-events}, which controls printing of
2847 messages on thread start and exit.
2848 @item @samp{set libthread-db-search-path @var{path}}, which lets
2849 the user specify which @code{libthread_db} to use if the default choice
2850 isn't compatible with the program.
2853 @cindex focus of debugging
2854 @cindex current thread
2855 The @value{GDBN} thread debugging facility allows you to observe all
2856 threads while your program runs---but whenever @value{GDBN} takes
2857 control, one thread in particular is always the focus of debugging.
2858 This thread is called the @dfn{current thread}. Debugging commands show
2859 program information from the perspective of the current thread.
2861 @cindex @code{New} @var{systag} message
2862 @cindex thread identifier (system)
2863 @c FIXME-implementors!! It would be more helpful if the [New...] message
2864 @c included GDB's numeric thread handle, so you could just go to that
2865 @c thread without first checking `info threads'.
2866 Whenever @value{GDBN} detects a new thread in your program, it displays
2867 the target system's identification for the thread with a message in the
2868 form @samp{[New @var{systag}]}, where @var{systag} is a thread identifier
2869 whose form varies depending on the particular system. For example, on
2870 @sc{gnu}/Linux, you might see
2873 [New Thread 0x41e02940 (LWP 25582)]
2877 when @value{GDBN} notices a new thread. In contrast, on other systems,
2878 the @var{systag} is simply something like @samp{process 368}, with no
2881 @c FIXME!! (1) Does the [New...] message appear even for the very first
2882 @c thread of a program, or does it only appear for the
2883 @c second---i.e.@: when it becomes obvious we have a multithread
2885 @c (2) *Is* there necessarily a first thread always? Or do some
2886 @c multithread systems permit starting a program with multiple
2887 @c threads ab initio?
2889 @anchor{thread numbers}
2890 @cindex thread number, per inferior
2891 @cindex thread identifier (GDB)
2892 For debugging purposes, @value{GDBN} associates its own thread number
2893 ---always a single integer---with each thread of an inferior. This
2894 number is unique between all threads of an inferior, but not unique
2895 between threads of different inferiors.
2897 @cindex qualified thread ID
2898 You can refer to a given thread in an inferior using the qualified
2899 @var{inferior-num}.@var{thread-num} syntax, also known as
2900 @dfn{qualified thread ID}, with @var{inferior-num} being the inferior
2901 number and @var{thread-num} being the thread number of the given
2902 inferior. For example, thread @code{2.3} refers to thread number 3 of
2903 inferior 2. If you omit @var{inferior-num} (e.g., @code{thread 3}),
2904 then @value{GDBN} infers you're referring to a thread of the current
2907 Until you create a second inferior, @value{GDBN} does not show the
2908 @var{inferior-num} part of thread IDs, even though you can always use
2909 the full @var{inferior-num}.@var{thread-num} form to refer to threads
2910 of inferior 1, the initial inferior.
2912 @anchor{thread ID lists}
2913 @cindex thread ID lists
2914 Some commands accept a space-separated @dfn{thread ID list} as
2915 argument. A list element can be a thread ID as shown in the first
2916 field of the @samp{info threads} display, with or without an inferior
2917 qualifier (e.g., @samp{2.1} or @samp{1}); or can be a range of thread
2918 numbers, again with or without an inferior qualifier, as in
2919 @var{inf1}.@var{thr1}-@var{thr2} or @var{thr1}-@var{thr2} (e.g.,
2920 @samp{1.2-4} or @samp{2-4}). For example, if the current inferior is
2921 1, the thread list @samp{1 2-3 4.5 6.7-9} includes threads 1 to 3 of
2922 inferior 1, thread 5 of inferior 4 and threads 7 to 9 of inferior 6.
2923 That is, in expanded qualified form, the same as @samp{1.1 1.2 1.3 4.5
2926 @anchor{global thread numbers}
2927 @cindex global thread number
2928 @cindex global thread identifier (GDB)
2929 In addition to a @emph{per-inferior} number, each thread is also
2930 assigned a unique @emph{global} number, also known as @dfn{global
2931 thread ID}, a single integer. Unlike the thread number component of
2932 the thread ID, no two threads have the same global ID, even when
2933 you're debugging multiple inferiors.
2935 From @value{GDBN}'s perspective, a process always has at least one
2936 thread. In other words, @value{GDBN} assigns a thread number to the
2937 program's ``main thread'' even if the program is not multi-threaded.
2939 @vindex $_thread@r{, convenience variable}
2940 The debugger convenience variable @samp{$_thread} contains the
2941 per-inferior thread number of the current thread. You may find this
2942 useful in writing breakpoint conditional expressions, command scripts,
2943 and so forth. @xref{Convenience Vars,, Convenience Variables}, for
2944 general information on convenience variables.
2947 @kindex info threads
2948 @item info threads @r{[}@var{thread-id-list}@r{]}
2950 Display information about one or more threads. With no arguments
2951 displays information about all threads. You can specify the list of
2952 threads that you want to display using the thread ID list syntax
2953 (@pxref{thread ID lists}).
2955 @value{GDBN} displays for each thread (in this order):
2959 the per-inferior thread number assigned by @value{GDBN}
2962 the target system's thread identifier (@var{systag})
2965 the thread's name, if one is known. A thread can either be named by
2966 the user (see @code{thread name}, below), or, in some cases, by the
2970 the current stack frame summary for that thread
2974 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2975 indicates the current thread.
2979 @c end table here to get a little more width for example
2982 (@value{GDBP}) info threads
2984 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2985 2 process 35 thread 23 0x34e5 in sigpause ()
2986 3 process 35 thread 27 0x34e5 in sigpause ()
2990 If you're debugging multiple inferiors, @value{GDBN} displays thread
2991 IDs using the qualified @var{inferior-num}.@var{thread-num} format.
2992 Otherwise, only @var{thread-num} is shown:
2995 (@value{GDBP}) info threads
2997 1.1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2998 1.2 process 35 thread 23 0x34e5 in sigpause ()
2999 1.3 process 35 thread 27 0x34e5 in sigpause ()
3000 * 2.1 process 65 thread 1 main (argc=1, argv=0x7ffffff8)
3003 On Solaris, you can display more information about user threads with a
3004 Solaris-specific command:
3007 @item maint info sol-threads
3008 @kindex maint info sol-threads
3009 @cindex thread info (Solaris)
3010 Display info on Solaris user threads.
3014 @kindex thread @var{thread-id}
3015 @item thread @var{thread-id}
3016 Make thread ID @var{thread-id} the current thread. The command
3017 argument @var{thread-id} is the @value{GDBN} thread ID, as shown in
3018 the first field of the @samp{info threads} display, with or without an
3019 inferior qualifier (e.g., @samp{2.1} or @samp{1}).
3021 @value{GDBN} responds by displaying the system identifier of the
3022 thread you selected, and its current stack frame summary:
3025 (@value{GDBP}) thread 2
3026 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
3027 #0 some_function (ignore=0x0) at example.c:8
3028 8 printf ("hello\n");
3032 As with the @samp{[New @dots{}]} message, the form of the text after
3033 @samp{Switching to} depends on your system's conventions for identifying
3036 @kindex thread apply
3037 @cindex apply command to several threads
3038 @item thread apply [@var{thread-id-list} | all [-ascending]] @var{command}
3039 The @code{thread apply} command allows you to apply the named
3040 @var{command} to one or more threads. Specify the threads that you
3041 want affected using the thread ID list syntax (@pxref{thread ID
3042 lists}), or specify @code{all} to apply to all threads. To apply a
3043 command to all threads in descending order, type @kbd{thread apply all
3044 @var{command}}. To apply a command to all threads in ascending order,
3045 type @kbd{thread apply all -ascending @var{command}}.
3049 @cindex name a thread
3050 @item thread name [@var{name}]
3051 This command assigns a name to the current thread. If no argument is
3052 given, any existing user-specified name is removed. The thread name
3053 appears in the @samp{info threads} display.
3055 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
3056 determine the name of the thread as given by the OS. On these
3057 systems, a name specified with @samp{thread name} will override the
3058 system-give name, and removing the user-specified name will cause
3059 @value{GDBN} to once again display the system-specified name.
3062 @cindex search for a thread
3063 @item thread find [@var{regexp}]
3064 Search for and display thread ids whose name or @var{systag}
3065 matches the supplied regular expression.
3067 As well as being the complement to the @samp{thread name} command,
3068 this command also allows you to identify a thread by its target
3069 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
3073 (@value{GDBN}) thread find 26688
3074 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
3075 (@value{GDBN}) info thread 4
3077 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
3080 @kindex set print thread-events
3081 @cindex print messages on thread start and exit
3082 @item set print thread-events
3083 @itemx set print thread-events on
3084 @itemx set print thread-events off
3085 The @code{set print thread-events} command allows you to enable or
3086 disable printing of messages when @value{GDBN} notices that new threads have
3087 started or that threads have exited. By default, these messages will
3088 be printed if detection of these events is supported by the target.
3089 Note that these messages cannot be disabled on all targets.
3091 @kindex show print thread-events
3092 @item show print thread-events
3093 Show whether messages will be printed when @value{GDBN} detects that threads
3094 have started and exited.
3097 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
3098 more information about how @value{GDBN} behaves when you stop and start
3099 programs with multiple threads.
3101 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
3102 watchpoints in programs with multiple threads.
3104 @anchor{set libthread-db-search-path}
3106 @kindex set libthread-db-search-path
3107 @cindex search path for @code{libthread_db}
3108 @item set libthread-db-search-path @r{[}@var{path}@r{]}
3109 If this variable is set, @var{path} is a colon-separated list of
3110 directories @value{GDBN} will use to search for @code{libthread_db}.
3111 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
3112 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
3113 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
3116 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
3117 @code{libthread_db} library to obtain information about threads in the
3118 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
3119 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
3120 specific thread debugging library loading is enabled
3121 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
3123 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
3124 refers to the default system directories that are
3125 normally searched for loading shared libraries. The @samp{$sdir} entry
3126 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
3127 (@pxref{libthread_db.so.1 file}).
3129 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
3130 refers to the directory from which @code{libpthread}
3131 was loaded in the inferior process.
3133 For any @code{libthread_db} library @value{GDBN} finds in above directories,
3134 @value{GDBN} attempts to initialize it with the current inferior process.
3135 If this initialization fails (which could happen because of a version
3136 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
3137 will unload @code{libthread_db}, and continue with the next directory.
3138 If none of @code{libthread_db} libraries initialize successfully,
3139 @value{GDBN} will issue a warning and thread debugging will be disabled.
3141 Setting @code{libthread-db-search-path} is currently implemented
3142 only on some platforms.
3144 @kindex show libthread-db-search-path
3145 @item show libthread-db-search-path
3146 Display current libthread_db search path.
3148 @kindex set debug libthread-db
3149 @kindex show debug libthread-db
3150 @cindex debugging @code{libthread_db}
3151 @item set debug libthread-db
3152 @itemx show debug libthread-db
3153 Turns on or off display of @code{libthread_db}-related events.
3154 Use @code{1} to enable, @code{0} to disable.
3158 @section Debugging Forks
3160 @cindex fork, debugging programs which call
3161 @cindex multiple processes
3162 @cindex processes, multiple
3163 On most systems, @value{GDBN} has no special support for debugging
3164 programs which create additional processes using the @code{fork}
3165 function. When a program forks, @value{GDBN} will continue to debug the
3166 parent process and the child process will run unimpeded. If you have
3167 set a breakpoint in any code which the child then executes, the child
3168 will get a @code{SIGTRAP} signal which (unless it catches the signal)
3169 will cause it to terminate.
3171 However, if you want to debug the child process there is a workaround
3172 which isn't too painful. Put a call to @code{sleep} in the code which
3173 the child process executes after the fork. It may be useful to sleep
3174 only if a certain environment variable is set, or a certain file exists,
3175 so that the delay need not occur when you don't want to run @value{GDBN}
3176 on the child. While the child is sleeping, use the @code{ps} program to
3177 get its process ID. Then tell @value{GDBN} (a new invocation of
3178 @value{GDBN} if you are also debugging the parent process) to attach to
3179 the child process (@pxref{Attach}). From that point on you can debug
3180 the child process just like any other process which you attached to.
3182 On some systems, @value{GDBN} provides support for debugging programs
3183 that create additional processes using the @code{fork} or @code{vfork}
3184 functions. On @sc{gnu}/Linux platforms, this feature is supported
3185 with kernel version 2.5.46 and later.
3187 The fork debugging commands are supported in native mode and when
3188 connected to @code{gdbserver} in either @code{target remote} mode or
3189 @code{target extended-remote} mode.
3191 By default, when a program forks, @value{GDBN} will continue to debug
3192 the parent process and the child process will run unimpeded.
3194 If you want to follow the child process instead of the parent process,
3195 use the command @w{@code{set follow-fork-mode}}.
3198 @kindex set follow-fork-mode
3199 @item set follow-fork-mode @var{mode}
3200 Set the debugger response to a program call of @code{fork} or
3201 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3202 process. The @var{mode} argument can be:
3206 The original process is debugged after a fork. The child process runs
3207 unimpeded. This is the default.
3210 The new process is debugged after a fork. The parent process runs
3215 @kindex show follow-fork-mode
3216 @item show follow-fork-mode
3217 Display the current debugger response to a @code{fork} or @code{vfork} call.
3220 @cindex debugging multiple processes
3221 On Linux, if you want to debug both the parent and child processes, use the
3222 command @w{@code{set detach-on-fork}}.
3225 @kindex set detach-on-fork
3226 @item set detach-on-fork @var{mode}
3227 Tells gdb whether to detach one of the processes after a fork, or
3228 retain debugger control over them both.
3232 The child process (or parent process, depending on the value of
3233 @code{follow-fork-mode}) will be detached and allowed to run
3234 independently. This is the default.
3237 Both processes will be held under the control of @value{GDBN}.
3238 One process (child or parent, depending on the value of
3239 @code{follow-fork-mode}) is debugged as usual, while the other
3244 @kindex show detach-on-fork
3245 @item show detach-on-fork
3246 Show whether detach-on-fork mode is on/off.
3249 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3250 will retain control of all forked processes (including nested forks).
3251 You can list the forked processes under the control of @value{GDBN} by
3252 using the @w{@code{info inferiors}} command, and switch from one fork
3253 to another by using the @code{inferior} command (@pxref{Inferiors and
3254 Programs, ,Debugging Multiple Inferiors and Programs}).
3256 To quit debugging one of the forked processes, you can either detach
3257 from it by using the @w{@code{detach inferiors}} command (allowing it
3258 to run independently), or kill it using the @w{@code{kill inferiors}}
3259 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3262 If you ask to debug a child process and a @code{vfork} is followed by an
3263 @code{exec}, @value{GDBN} executes the new target up to the first
3264 breakpoint in the new target. If you have a breakpoint set on
3265 @code{main} in your original program, the breakpoint will also be set on
3266 the child process's @code{main}.
3268 On some systems, when a child process is spawned by @code{vfork}, you
3269 cannot debug the child or parent until an @code{exec} call completes.
3271 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3272 call executes, the new target restarts. To restart the parent
3273 process, use the @code{file} command with the parent executable name
3274 as its argument. By default, after an @code{exec} call executes,
3275 @value{GDBN} discards the symbols of the previous executable image.
3276 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3280 @kindex set follow-exec-mode
3281 @item set follow-exec-mode @var{mode}
3283 Set debugger response to a program call of @code{exec}. An
3284 @code{exec} call replaces the program image of a process.
3286 @code{follow-exec-mode} can be:
3290 @value{GDBN} creates a new inferior and rebinds the process to this
3291 new inferior. The program the process was running before the
3292 @code{exec} call can be restarted afterwards by restarting the
3298 (@value{GDBP}) info inferiors
3300 Id Description Executable
3303 process 12020 is executing new program: prog2
3304 Program exited normally.
3305 (@value{GDBP}) info inferiors
3306 Id Description Executable
3312 @value{GDBN} keeps the process bound to the same inferior. The new
3313 executable image replaces the previous executable loaded in the
3314 inferior. Restarting the inferior after the @code{exec} call, with
3315 e.g., the @code{run} command, restarts the executable the process was
3316 running after the @code{exec} call. This is the default mode.
3321 (@value{GDBP}) info inferiors
3322 Id Description Executable
3325 process 12020 is executing new program: prog2
3326 Program exited normally.
3327 (@value{GDBP}) info inferiors
3328 Id Description Executable
3335 @code{follow-exec-mode} is supported in native mode and
3336 @code{target extended-remote} mode.
3338 You can use the @code{catch} command to make @value{GDBN} stop whenever
3339 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3340 Catchpoints, ,Setting Catchpoints}.
3342 @node Checkpoint/Restart
3343 @section Setting a @emph{Bookmark} to Return to Later
3348 @cindex snapshot of a process
3349 @cindex rewind program state
3351 On certain operating systems@footnote{Currently, only
3352 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3353 program's state, called a @dfn{checkpoint}, and come back to it
3356 Returning to a checkpoint effectively undoes everything that has
3357 happened in the program since the @code{checkpoint} was saved. This
3358 includes changes in memory, registers, and even (within some limits)
3359 system state. Effectively, it is like going back in time to the
3360 moment when the checkpoint was saved.
3362 Thus, if you're stepping thru a program and you think you're
3363 getting close to the point where things go wrong, you can save
3364 a checkpoint. Then, if you accidentally go too far and miss
3365 the critical statement, instead of having to restart your program
3366 from the beginning, you can just go back to the checkpoint and
3367 start again from there.
3369 This can be especially useful if it takes a lot of time or
3370 steps to reach the point where you think the bug occurs.
3372 To use the @code{checkpoint}/@code{restart} method of debugging:
3377 Save a snapshot of the debugged program's current execution state.
3378 The @code{checkpoint} command takes no arguments, but each checkpoint
3379 is assigned a small integer id, similar to a breakpoint id.
3381 @kindex info checkpoints
3382 @item info checkpoints
3383 List the checkpoints that have been saved in the current debugging
3384 session. For each checkpoint, the following information will be
3391 @item Source line, or label
3394 @kindex restart @var{checkpoint-id}
3395 @item restart @var{checkpoint-id}
3396 Restore the program state that was saved as checkpoint number
3397 @var{checkpoint-id}. All program variables, registers, stack frames
3398 etc.@: will be returned to the values that they had when the checkpoint
3399 was saved. In essence, gdb will ``wind back the clock'' to the point
3400 in time when the checkpoint was saved.
3402 Note that breakpoints, @value{GDBN} variables, command history etc.
3403 are not affected by restoring a checkpoint. In general, a checkpoint
3404 only restores things that reside in the program being debugged, not in
3407 @kindex delete checkpoint @var{checkpoint-id}
3408 @item delete checkpoint @var{checkpoint-id}
3409 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3413 Returning to a previously saved checkpoint will restore the user state
3414 of the program being debugged, plus a significant subset of the system
3415 (OS) state, including file pointers. It won't ``un-write'' data from
3416 a file, but it will rewind the file pointer to the previous location,
3417 so that the previously written data can be overwritten. For files
3418 opened in read mode, the pointer will also be restored so that the
3419 previously read data can be read again.
3421 Of course, characters that have been sent to a printer (or other
3422 external device) cannot be ``snatched back'', and characters received
3423 from eg.@: a serial device can be removed from internal program buffers,
3424 but they cannot be ``pushed back'' into the serial pipeline, ready to
3425 be received again. Similarly, the actual contents of files that have
3426 been changed cannot be restored (at this time).
3428 However, within those constraints, you actually can ``rewind'' your
3429 program to a previously saved point in time, and begin debugging it
3430 again --- and you can change the course of events so as to debug a
3431 different execution path this time.
3433 @cindex checkpoints and process id
3434 Finally, there is one bit of internal program state that will be
3435 different when you return to a checkpoint --- the program's process
3436 id. Each checkpoint will have a unique process id (or @var{pid}),
3437 and each will be different from the program's original @var{pid}.
3438 If your program has saved a local copy of its process id, this could
3439 potentially pose a problem.
3441 @subsection A Non-obvious Benefit of Using Checkpoints
3443 On some systems such as @sc{gnu}/Linux, address space randomization
3444 is performed on new processes for security reasons. This makes it
3445 difficult or impossible to set a breakpoint, or watchpoint, on an
3446 absolute address if you have to restart the program, since the
3447 absolute location of a symbol will change from one execution to the
3450 A checkpoint, however, is an @emph{identical} copy of a process.
3451 Therefore if you create a checkpoint at (eg.@:) the start of main,
3452 and simply return to that checkpoint instead of restarting the
3453 process, you can avoid the effects of address randomization and
3454 your symbols will all stay in the same place.
3457 @chapter Stopping and Continuing
3459 The principal purposes of using a debugger are so that you can stop your
3460 program before it terminates; or so that, if your program runs into
3461 trouble, you can investigate and find out why.
3463 Inside @value{GDBN}, your program may stop for any of several reasons,
3464 such as a signal, a breakpoint, or reaching a new line after a
3465 @value{GDBN} command such as @code{step}. You may then examine and
3466 change variables, set new breakpoints or remove old ones, and then
3467 continue execution. Usually, the messages shown by @value{GDBN} provide
3468 ample explanation of the status of your program---but you can also
3469 explicitly request this information at any time.
3472 @kindex info program
3474 Display information about the status of your program: whether it is
3475 running or not, what process it is, and why it stopped.
3479 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3480 * Continuing and Stepping:: Resuming execution
3481 * Skipping Over Functions and Files::
3482 Skipping over functions and files
3484 * Thread Stops:: Stopping and starting multi-thread programs
3488 @section Breakpoints, Watchpoints, and Catchpoints
3491 A @dfn{breakpoint} makes your program stop whenever a certain point in
3492 the program is reached. For each breakpoint, you can add conditions to
3493 control in finer detail whether your program stops. You can set
3494 breakpoints with the @code{break} command and its variants (@pxref{Set
3495 Breaks, ,Setting Breakpoints}), to specify the place where your program
3496 should stop by line number, function name or exact address in the
3499 On some systems, you can set breakpoints in shared libraries before
3500 the executable is run.
3503 @cindex data breakpoints
3504 @cindex memory tracing
3505 @cindex breakpoint on memory address
3506 @cindex breakpoint on variable modification
3507 A @dfn{watchpoint} is a special breakpoint that stops your program
3508 when the value of an expression changes. The expression may be a value
3509 of a variable, or it could involve values of one or more variables
3510 combined by operators, such as @samp{a + b}. This is sometimes called
3511 @dfn{data breakpoints}. You must use a different command to set
3512 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3513 from that, you can manage a watchpoint like any other breakpoint: you
3514 enable, disable, and delete both breakpoints and watchpoints using the
3517 You can arrange to have values from your program displayed automatically
3518 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3522 @cindex breakpoint on events
3523 A @dfn{catchpoint} is another special breakpoint that stops your program
3524 when a certain kind of event occurs, such as the throwing of a C@t{++}
3525 exception or the loading of a library. As with watchpoints, you use a
3526 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3527 Catchpoints}), but aside from that, you can manage a catchpoint like any
3528 other breakpoint. (To stop when your program receives a signal, use the
3529 @code{handle} command; see @ref{Signals, ,Signals}.)
3531 @cindex breakpoint numbers
3532 @cindex numbers for breakpoints
3533 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3534 catchpoint when you create it; these numbers are successive integers
3535 starting with one. In many of the commands for controlling various
3536 features of breakpoints you use the breakpoint number to say which
3537 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3538 @dfn{disabled}; if disabled, it has no effect on your program until you
3541 @cindex breakpoint ranges
3542 @cindex ranges of breakpoints
3543 Some @value{GDBN} commands accept a range of breakpoints on which to
3544 operate. A breakpoint range is either a single breakpoint number, like
3545 @samp{5}, or two such numbers, in increasing order, separated by a
3546 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3547 all breakpoints in that range are operated on.
3550 * Set Breaks:: Setting breakpoints
3551 * Set Watchpoints:: Setting watchpoints
3552 * Set Catchpoints:: Setting catchpoints
3553 * Delete Breaks:: Deleting breakpoints
3554 * Disabling:: Disabling breakpoints
3555 * Conditions:: Break conditions
3556 * Break Commands:: Breakpoint command lists
3557 * Dynamic Printf:: Dynamic printf
3558 * Save Breakpoints:: How to save breakpoints in a file
3559 * Static Probe Points:: Listing static probe points
3560 * Error in Breakpoints:: ``Cannot insert breakpoints''
3561 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3565 @subsection Setting Breakpoints
3567 @c FIXME LMB what does GDB do if no code on line of breakpt?
3568 @c consider in particular declaration with/without initialization.
3570 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3573 @kindex b @r{(@code{break})}
3574 @vindex $bpnum@r{, convenience variable}
3575 @cindex latest breakpoint
3576 Breakpoints are set with the @code{break} command (abbreviated
3577 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3578 number of the breakpoint you've set most recently; see @ref{Convenience
3579 Vars,, Convenience Variables}, for a discussion of what you can do with
3580 convenience variables.
3583 @item break @var{location}
3584 Set a breakpoint at the given @var{location}, which can specify a
3585 function name, a line number, or an address of an instruction.
3586 (@xref{Specify Location}, for a list of all the possible ways to
3587 specify a @var{location}.) The breakpoint will stop your program just
3588 before it executes any of the code in the specified @var{location}.
3590 When using source languages that permit overloading of symbols, such as
3591 C@t{++}, a function name may refer to more than one possible place to break.
3592 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3595 It is also possible to insert a breakpoint that will stop the program
3596 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3597 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3600 When called without any arguments, @code{break} sets a breakpoint at
3601 the next instruction to be executed in the selected stack frame
3602 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3603 innermost, this makes your program stop as soon as control
3604 returns to that frame. This is similar to the effect of a
3605 @code{finish} command in the frame inside the selected frame---except
3606 that @code{finish} does not leave an active breakpoint. If you use
3607 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3608 the next time it reaches the current location; this may be useful
3611 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3612 least one instruction has been executed. If it did not do this, you
3613 would be unable to proceed past a breakpoint without first disabling the
3614 breakpoint. This rule applies whether or not the breakpoint already
3615 existed when your program stopped.
3617 @item break @dots{} if @var{cond}
3618 Set a breakpoint with condition @var{cond}; evaluate the expression
3619 @var{cond} each time the breakpoint is reached, and stop only if the
3620 value is nonzero---that is, if @var{cond} evaluates as true.
3621 @samp{@dots{}} stands for one of the possible arguments described
3622 above (or no argument) specifying where to break. @xref{Conditions,
3623 ,Break Conditions}, for more information on breakpoint conditions.
3626 @item tbreak @var{args}
3627 Set a breakpoint enabled only for one stop. The @var{args} are the
3628 same as for the @code{break} command, and the breakpoint is set in the same
3629 way, but the breakpoint is automatically deleted after the first time your
3630 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3633 @cindex hardware breakpoints
3634 @item hbreak @var{args}
3635 Set a hardware-assisted breakpoint. The @var{args} are the same as for the
3636 @code{break} command and the breakpoint is set in the same way, but the
3637 breakpoint requires hardware support and some target hardware may not
3638 have this support. The main purpose of this is EPROM/ROM code
3639 debugging, so you can set a breakpoint at an instruction without
3640 changing the instruction. This can be used with the new trap-generation
3641 provided by SPARClite DSU and most x86-based targets. These targets
3642 will generate traps when a program accesses some data or instruction
3643 address that is assigned to the debug registers. However the hardware
3644 breakpoint registers can take a limited number of breakpoints. For
3645 example, on the DSU, only two data breakpoints can be set at a time, and
3646 @value{GDBN} will reject this command if more than two are used. Delete
3647 or disable unused hardware breakpoints before setting new ones
3648 (@pxref{Disabling, ,Disabling Breakpoints}).
3649 @xref{Conditions, ,Break Conditions}.
3650 For remote targets, you can restrict the number of hardware
3651 breakpoints @value{GDBN} will use, see @ref{set remote
3652 hardware-breakpoint-limit}.
3655 @item thbreak @var{args}
3656 Set a hardware-assisted breakpoint enabled only for one stop. The @var{args}
3657 are the same as for the @code{hbreak} command and the breakpoint is set in
3658 the same way. However, like the @code{tbreak} command,
3659 the breakpoint is automatically deleted after the
3660 first time your program stops there. Also, like the @code{hbreak}
3661 command, the breakpoint requires hardware support and some target hardware
3662 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3663 See also @ref{Conditions, ,Break Conditions}.
3666 @cindex regular expression
3667 @cindex breakpoints at functions matching a regexp
3668 @cindex set breakpoints in many functions
3669 @item rbreak @var{regex}
3670 Set breakpoints on all functions matching the regular expression
3671 @var{regex}. This command sets an unconditional breakpoint on all
3672 matches, printing a list of all breakpoints it set. Once these
3673 breakpoints are set, they are treated just like the breakpoints set with
3674 the @code{break} command. You can delete them, disable them, or make
3675 them conditional the same way as any other breakpoint.
3677 The syntax of the regular expression is the standard one used with tools
3678 like @file{grep}. Note that this is different from the syntax used by
3679 shells, so for instance @code{foo*} matches all functions that include
3680 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3681 @code{.*} leading and trailing the regular expression you supply, so to
3682 match only functions that begin with @code{foo}, use @code{^foo}.
3684 @cindex non-member C@t{++} functions, set breakpoint in
3685 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3686 breakpoints on overloaded functions that are not members of any special
3689 @cindex set breakpoints on all functions
3690 The @code{rbreak} command can be used to set breakpoints in
3691 @strong{all} the functions in a program, like this:
3694 (@value{GDBP}) rbreak .
3697 @item rbreak @var{file}:@var{regex}
3698 If @code{rbreak} is called with a filename qualification, it limits
3699 the search for functions matching the given regular expression to the
3700 specified @var{file}. This can be used, for example, to set breakpoints on
3701 every function in a given file:
3704 (@value{GDBP}) rbreak file.c:.
3707 The colon separating the filename qualifier from the regex may
3708 optionally be surrounded by spaces.
3710 @kindex info breakpoints
3711 @cindex @code{$_} and @code{info breakpoints}
3712 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3713 @itemx info break @r{[}@var{n}@dots{}@r{]}
3714 Print a table of all breakpoints, watchpoints, and catchpoints set and
3715 not deleted. Optional argument @var{n} means print information only
3716 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3717 For each breakpoint, following columns are printed:
3720 @item Breakpoint Numbers
3722 Breakpoint, watchpoint, or catchpoint.
3724 Whether the breakpoint is marked to be disabled or deleted when hit.
3725 @item Enabled or Disabled
3726 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3727 that are not enabled.
3729 Where the breakpoint is in your program, as a memory address. For a
3730 pending breakpoint whose address is not yet known, this field will
3731 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3732 library that has the symbol or line referred by breakpoint is loaded.
3733 See below for details. A breakpoint with several locations will
3734 have @samp{<MULTIPLE>} in this field---see below for details.
3736 Where the breakpoint is in the source for your program, as a file and
3737 line number. For a pending breakpoint, the original string passed to
3738 the breakpoint command will be listed as it cannot be resolved until
3739 the appropriate shared library is loaded in the future.
3743 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3744 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3745 @value{GDBN} on the host's side. If it is ``target'', then the condition
3746 is evaluated by the target. The @code{info break} command shows
3747 the condition on the line following the affected breakpoint, together with
3748 its condition evaluation mode in between parentheses.
3750 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3751 allowed to have a condition specified for it. The condition is not parsed for
3752 validity until a shared library is loaded that allows the pending
3753 breakpoint to resolve to a valid location.
3756 @code{info break} with a breakpoint
3757 number @var{n} as argument lists only that breakpoint. The
3758 convenience variable @code{$_} and the default examining-address for
3759 the @code{x} command are set to the address of the last breakpoint
3760 listed (@pxref{Memory, ,Examining Memory}).
3763 @code{info break} displays a count of the number of times the breakpoint
3764 has been hit. This is especially useful in conjunction with the
3765 @code{ignore} command. You can ignore a large number of breakpoint
3766 hits, look at the breakpoint info to see how many times the breakpoint
3767 was hit, and then run again, ignoring one less than that number. This
3768 will get you quickly to the last hit of that breakpoint.
3771 For a breakpoints with an enable count (xref) greater than 1,
3772 @code{info break} also displays that count.
3776 @value{GDBN} allows you to set any number of breakpoints at the same place in
3777 your program. There is nothing silly or meaningless about this. When
3778 the breakpoints are conditional, this is even useful
3779 (@pxref{Conditions, ,Break Conditions}).
3781 @cindex multiple locations, breakpoints
3782 @cindex breakpoints, multiple locations
3783 It is possible that a breakpoint corresponds to several locations
3784 in your program. Examples of this situation are:
3788 Multiple functions in the program may have the same name.
3791 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3792 instances of the function body, used in different cases.
3795 For a C@t{++} template function, a given line in the function can
3796 correspond to any number of instantiations.
3799 For an inlined function, a given source line can correspond to
3800 several places where that function is inlined.
3803 In all those cases, @value{GDBN} will insert a breakpoint at all
3804 the relevant locations.
3806 A breakpoint with multiple locations is displayed in the breakpoint
3807 table using several rows---one header row, followed by one row for
3808 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3809 address column. The rows for individual locations contain the actual
3810 addresses for locations, and show the functions to which those
3811 locations belong. The number column for a location is of the form
3812 @var{breakpoint-number}.@var{location-number}.
3817 Num Type Disp Enb Address What
3818 1 breakpoint keep y <MULTIPLE>
3820 breakpoint already hit 1 time
3821 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3822 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3825 Each location can be individually enabled or disabled by passing
3826 @var{breakpoint-number}.@var{location-number} as argument to the
3827 @code{enable} and @code{disable} commands. Note that you cannot
3828 delete the individual locations from the list, you can only delete the
3829 entire list of locations that belong to their parent breakpoint (with
3830 the @kbd{delete @var{num}} command, where @var{num} is the number of
3831 the parent breakpoint, 1 in the above example). Disabling or enabling
3832 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3833 that belong to that breakpoint.
3835 @cindex pending breakpoints
3836 It's quite common to have a breakpoint inside a shared library.
3837 Shared libraries can be loaded and unloaded explicitly,
3838 and possibly repeatedly, as the program is executed. To support
3839 this use case, @value{GDBN} updates breakpoint locations whenever
3840 any shared library is loaded or unloaded. Typically, you would
3841 set a breakpoint in a shared library at the beginning of your
3842 debugging session, when the library is not loaded, and when the
3843 symbols from the library are not available. When you try to set
3844 breakpoint, @value{GDBN} will ask you if you want to set
3845 a so called @dfn{pending breakpoint}---breakpoint whose address
3846 is not yet resolved.
3848 After the program is run, whenever a new shared library is loaded,
3849 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3850 shared library contains the symbol or line referred to by some
3851 pending breakpoint, that breakpoint is resolved and becomes an
3852 ordinary breakpoint. When a library is unloaded, all breakpoints
3853 that refer to its symbols or source lines become pending again.
3855 This logic works for breakpoints with multiple locations, too. For
3856 example, if you have a breakpoint in a C@t{++} template function, and
3857 a newly loaded shared library has an instantiation of that template,
3858 a new location is added to the list of locations for the breakpoint.
3860 Except for having unresolved address, pending breakpoints do not
3861 differ from regular breakpoints. You can set conditions or commands,
3862 enable and disable them and perform other breakpoint operations.
3864 @value{GDBN} provides some additional commands for controlling what
3865 happens when the @samp{break} command cannot resolve breakpoint
3866 address specification to an address:
3868 @kindex set breakpoint pending
3869 @kindex show breakpoint pending
3871 @item set breakpoint pending auto
3872 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3873 location, it queries you whether a pending breakpoint should be created.
3875 @item set breakpoint pending on
3876 This indicates that an unrecognized breakpoint location should automatically
3877 result in a pending breakpoint being created.
3879 @item set breakpoint pending off
3880 This indicates that pending breakpoints are not to be created. Any
3881 unrecognized breakpoint location results in an error. This setting does
3882 not affect any pending breakpoints previously created.
3884 @item show breakpoint pending
3885 Show the current behavior setting for creating pending breakpoints.
3888 The settings above only affect the @code{break} command and its
3889 variants. Once breakpoint is set, it will be automatically updated
3890 as shared libraries are loaded and unloaded.
3892 @cindex automatic hardware breakpoints
3893 For some targets, @value{GDBN} can automatically decide if hardware or
3894 software breakpoints should be used, depending on whether the
3895 breakpoint address is read-only or read-write. This applies to
3896 breakpoints set with the @code{break} command as well as to internal
3897 breakpoints set by commands like @code{next} and @code{finish}. For
3898 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3901 You can control this automatic behaviour with the following commands::
3903 @kindex set breakpoint auto-hw
3904 @kindex show breakpoint auto-hw
3906 @item set breakpoint auto-hw on
3907 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3908 will try to use the target memory map to decide if software or hardware
3909 breakpoint must be used.
3911 @item set breakpoint auto-hw off
3912 This indicates @value{GDBN} should not automatically select breakpoint
3913 type. If the target provides a memory map, @value{GDBN} will warn when
3914 trying to set software breakpoint at a read-only address.
3917 @value{GDBN} normally implements breakpoints by replacing the program code
3918 at the breakpoint address with a special instruction, which, when
3919 executed, given control to the debugger. By default, the program
3920 code is so modified only when the program is resumed. As soon as
3921 the program stops, @value{GDBN} restores the original instructions. This
3922 behaviour guards against leaving breakpoints inserted in the
3923 target should gdb abrubptly disconnect. However, with slow remote
3924 targets, inserting and removing breakpoint can reduce the performance.
3925 This behavior can be controlled with the following commands::
3927 @kindex set breakpoint always-inserted
3928 @kindex show breakpoint always-inserted
3930 @item set breakpoint always-inserted off
3931 All breakpoints, including newly added by the user, are inserted in
3932 the target only when the target is resumed. All breakpoints are
3933 removed from the target when it stops. This is the default mode.
3935 @item set breakpoint always-inserted on
3936 Causes all breakpoints to be inserted in the target at all times. If
3937 the user adds a new breakpoint, or changes an existing breakpoint, the
3938 breakpoints in the target are updated immediately. A breakpoint is
3939 removed from the target only when breakpoint itself is deleted.
3942 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3943 when a breakpoint breaks. If the condition is true, then the process being
3944 debugged stops, otherwise the process is resumed.
3946 If the target supports evaluating conditions on its end, @value{GDBN} may
3947 download the breakpoint, together with its conditions, to it.
3949 This feature can be controlled via the following commands:
3951 @kindex set breakpoint condition-evaluation
3952 @kindex show breakpoint condition-evaluation
3954 @item set breakpoint condition-evaluation host
3955 This option commands @value{GDBN} to evaluate the breakpoint
3956 conditions on the host's side. Unconditional breakpoints are sent to
3957 the target which in turn receives the triggers and reports them back to GDB
3958 for condition evaluation. This is the standard evaluation mode.
3960 @item set breakpoint condition-evaluation target
3961 This option commands @value{GDBN} to download breakpoint conditions
3962 to the target at the moment of their insertion. The target
3963 is responsible for evaluating the conditional expression and reporting
3964 breakpoint stop events back to @value{GDBN} whenever the condition
3965 is true. Due to limitations of target-side evaluation, some conditions
3966 cannot be evaluated there, e.g., conditions that depend on local data
3967 that is only known to the host. Examples include
3968 conditional expressions involving convenience variables, complex types
3969 that cannot be handled by the agent expression parser and expressions
3970 that are too long to be sent over to the target, specially when the
3971 target is a remote system. In these cases, the conditions will be
3972 evaluated by @value{GDBN}.
3974 @item set breakpoint condition-evaluation auto
3975 This is the default mode. If the target supports evaluating breakpoint
3976 conditions on its end, @value{GDBN} will download breakpoint conditions to
3977 the target (limitations mentioned previously apply). If the target does
3978 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3979 to evaluating all these conditions on the host's side.
3983 @cindex negative breakpoint numbers
3984 @cindex internal @value{GDBN} breakpoints
3985 @value{GDBN} itself sometimes sets breakpoints in your program for
3986 special purposes, such as proper handling of @code{longjmp} (in C
3987 programs). These internal breakpoints are assigned negative numbers,
3988 starting with @code{-1}; @samp{info breakpoints} does not display them.
3989 You can see these breakpoints with the @value{GDBN} maintenance command
3990 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3993 @node Set Watchpoints
3994 @subsection Setting Watchpoints
3996 @cindex setting watchpoints
3997 You can use a watchpoint to stop execution whenever the value of an
3998 expression changes, without having to predict a particular place where
3999 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
4000 The expression may be as simple as the value of a single variable, or
4001 as complex as many variables combined by operators. Examples include:
4005 A reference to the value of a single variable.
4008 An address cast to an appropriate data type. For example,
4009 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
4010 address (assuming an @code{int} occupies 4 bytes).
4013 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
4014 expression can use any operators valid in the program's native
4015 language (@pxref{Languages}).
4018 You can set a watchpoint on an expression even if the expression can
4019 not be evaluated yet. For instance, you can set a watchpoint on
4020 @samp{*global_ptr} before @samp{global_ptr} is initialized.
4021 @value{GDBN} will stop when your program sets @samp{global_ptr} and
4022 the expression produces a valid value. If the expression becomes
4023 valid in some other way than changing a variable (e.g.@: if the memory
4024 pointed to by @samp{*global_ptr} becomes readable as the result of a
4025 @code{malloc} call), @value{GDBN} may not stop until the next time
4026 the expression changes.
4028 @cindex software watchpoints
4029 @cindex hardware watchpoints
4030 Depending on your system, watchpoints may be implemented in software or
4031 hardware. @value{GDBN} does software watchpointing by single-stepping your
4032 program and testing the variable's value each time, which is hundreds of
4033 times slower than normal execution. (But this may still be worth it, to
4034 catch errors where you have no clue what part of your program is the
4037 On some systems, such as most PowerPC or x86-based targets,
4038 @value{GDBN} includes support for hardware watchpoints, which do not
4039 slow down the running of your program.
4043 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4044 Set a watchpoint for an expression. @value{GDBN} will break when the
4045 expression @var{expr} is written into by the program and its value
4046 changes. The simplest (and the most popular) use of this command is
4047 to watch the value of a single variable:
4050 (@value{GDBP}) watch foo
4053 If the command includes a @code{@r{[}thread @var{thread-id}@r{]}}
4054 argument, @value{GDBN} breaks only when the thread identified by
4055 @var{thread-id} changes the value of @var{expr}. If any other threads
4056 change the value of @var{expr}, @value{GDBN} will not break. Note
4057 that watchpoints restricted to a single thread in this way only work
4058 with Hardware Watchpoints.
4060 Ordinarily a watchpoint respects the scope of variables in @var{expr}
4061 (see below). The @code{-location} argument tells @value{GDBN} to
4062 instead watch the memory referred to by @var{expr}. In this case,
4063 @value{GDBN} will evaluate @var{expr}, take the address of the result,
4064 and watch the memory at that address. The type of the result is used
4065 to determine the size of the watched memory. If the expression's
4066 result does not have an address, then @value{GDBN} will print an
4069 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
4070 of masked watchpoints, if the current architecture supports this
4071 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
4072 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
4073 to an address to watch. The mask specifies that some bits of an address
4074 (the bits which are reset in the mask) should be ignored when matching
4075 the address accessed by the inferior against the watchpoint address.
4076 Thus, a masked watchpoint watches many addresses simultaneously---those
4077 addresses whose unmasked bits are identical to the unmasked bits in the
4078 watchpoint address. The @code{mask} argument implies @code{-location}.
4082 (@value{GDBP}) watch foo mask 0xffff00ff
4083 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
4087 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4088 Set a watchpoint that will break when the value of @var{expr} is read
4092 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{thread-id}@r{]} @r{[}mask @var{maskvalue}@r{]}
4093 Set a watchpoint that will break when @var{expr} is either read from
4094 or written into by the program.
4096 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
4097 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
4098 This command prints a list of watchpoints, using the same format as
4099 @code{info break} (@pxref{Set Breaks}).
4102 If you watch for a change in a numerically entered address you need to
4103 dereference it, as the address itself is just a constant number which will
4104 never change. @value{GDBN} refuses to create a watchpoint that watches
4105 a never-changing value:
4108 (@value{GDBP}) watch 0x600850
4109 Cannot watch constant value 0x600850.
4110 (@value{GDBP}) watch *(int *) 0x600850
4111 Watchpoint 1: *(int *) 6293584
4114 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
4115 watchpoints execute very quickly, and the debugger reports a change in
4116 value at the exact instruction where the change occurs. If @value{GDBN}
4117 cannot set a hardware watchpoint, it sets a software watchpoint, which
4118 executes more slowly and reports the change in value at the next
4119 @emph{statement}, not the instruction, after the change occurs.
4121 @cindex use only software watchpoints
4122 You can force @value{GDBN} to use only software watchpoints with the
4123 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
4124 zero, @value{GDBN} will never try to use hardware watchpoints, even if
4125 the underlying system supports them. (Note that hardware-assisted
4126 watchpoints that were set @emph{before} setting
4127 @code{can-use-hw-watchpoints} to zero will still use the hardware
4128 mechanism of watching expression values.)
4131 @item set can-use-hw-watchpoints
4132 @kindex set can-use-hw-watchpoints
4133 Set whether or not to use hardware watchpoints.
4135 @item show can-use-hw-watchpoints
4136 @kindex show can-use-hw-watchpoints
4137 Show the current mode of using hardware watchpoints.
4140 For remote targets, you can restrict the number of hardware
4141 watchpoints @value{GDBN} will use, see @ref{set remote
4142 hardware-breakpoint-limit}.
4144 When you issue the @code{watch} command, @value{GDBN} reports
4147 Hardware watchpoint @var{num}: @var{expr}
4151 if it was able to set a hardware watchpoint.
4153 Currently, the @code{awatch} and @code{rwatch} commands can only set
4154 hardware watchpoints, because accesses to data that don't change the
4155 value of the watched expression cannot be detected without examining
4156 every instruction as it is being executed, and @value{GDBN} does not do
4157 that currently. If @value{GDBN} finds that it is unable to set a
4158 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
4159 will print a message like this:
4162 Expression cannot be implemented with read/access watchpoint.
4165 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
4166 data type of the watched expression is wider than what a hardware
4167 watchpoint on the target machine can handle. For example, some systems
4168 can only watch regions that are up to 4 bytes wide; on such systems you
4169 cannot set hardware watchpoints for an expression that yields a
4170 double-precision floating-point number (which is typically 8 bytes
4171 wide). As a work-around, it might be possible to break the large region
4172 into a series of smaller ones and watch them with separate watchpoints.
4174 If you set too many hardware watchpoints, @value{GDBN} might be unable
4175 to insert all of them when you resume the execution of your program.
4176 Since the precise number of active watchpoints is unknown until such
4177 time as the program is about to be resumed, @value{GDBN} might not be
4178 able to warn you about this when you set the watchpoints, and the
4179 warning will be printed only when the program is resumed:
4182 Hardware watchpoint @var{num}: Could not insert watchpoint
4186 If this happens, delete or disable some of the watchpoints.
4188 Watching complex expressions that reference many variables can also
4189 exhaust the resources available for hardware-assisted watchpoints.
4190 That's because @value{GDBN} needs to watch every variable in the
4191 expression with separately allocated resources.
4193 If you call a function interactively using @code{print} or @code{call},
4194 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4195 kind of breakpoint or the call completes.
4197 @value{GDBN} automatically deletes watchpoints that watch local
4198 (automatic) variables, or expressions that involve such variables, when
4199 they go out of scope, that is, when the execution leaves the block in
4200 which these variables were defined. In particular, when the program
4201 being debugged terminates, @emph{all} local variables go out of scope,
4202 and so only watchpoints that watch global variables remain set. If you
4203 rerun the program, you will need to set all such watchpoints again. One
4204 way of doing that would be to set a code breakpoint at the entry to the
4205 @code{main} function and when it breaks, set all the watchpoints.
4207 @cindex watchpoints and threads
4208 @cindex threads and watchpoints
4209 In multi-threaded programs, watchpoints will detect changes to the
4210 watched expression from every thread.
4213 @emph{Warning:} In multi-threaded programs, software watchpoints
4214 have only limited usefulness. If @value{GDBN} creates a software
4215 watchpoint, it can only watch the value of an expression @emph{in a
4216 single thread}. If you are confident that the expression can only
4217 change due to the current thread's activity (and if you are also
4218 confident that no other thread can become current), then you can use
4219 software watchpoints as usual. However, @value{GDBN} may not notice
4220 when a non-current thread's activity changes the expression. (Hardware
4221 watchpoints, in contrast, watch an expression in all threads.)
4224 @xref{set remote hardware-watchpoint-limit}.
4226 @node Set Catchpoints
4227 @subsection Setting Catchpoints
4228 @cindex catchpoints, setting
4229 @cindex exception handlers
4230 @cindex event handling
4232 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4233 kinds of program events, such as C@t{++} exceptions or the loading of a
4234 shared library. Use the @code{catch} command to set a catchpoint.
4238 @item catch @var{event}
4239 Stop when @var{event} occurs. The @var{event} can be any of the following:
4242 @item throw @r{[}@var{regexp}@r{]}
4243 @itemx rethrow @r{[}@var{regexp}@r{]}
4244 @itemx catch @r{[}@var{regexp}@r{]}
4246 @kindex catch rethrow
4248 @cindex stop on C@t{++} exceptions
4249 The throwing, re-throwing, or catching of a C@t{++} exception.
4251 If @var{regexp} is given, then only exceptions whose type matches the
4252 regular expression will be caught.
4254 @vindex $_exception@r{, convenience variable}
4255 The convenience variable @code{$_exception} is available at an
4256 exception-related catchpoint, on some systems. This holds the
4257 exception being thrown.
4259 There are currently some limitations to C@t{++} exception handling in
4264 The support for these commands is system-dependent. Currently, only
4265 systems using the @samp{gnu-v3} C@t{++} ABI (@pxref{ABI}) are
4269 The regular expression feature and the @code{$_exception} convenience
4270 variable rely on the presence of some SDT probes in @code{libstdc++}.
4271 If these probes are not present, then these features cannot be used.
4272 These probes were first available in the GCC 4.8 release, but whether
4273 or not they are available in your GCC also depends on how it was
4277 The @code{$_exception} convenience variable is only valid at the
4278 instruction at which an exception-related catchpoint is set.
4281 When an exception-related catchpoint is hit, @value{GDBN} stops at a
4282 location in the system library which implements runtime exception
4283 support for C@t{++}, usually @code{libstdc++}. You can use @code{up}
4284 (@pxref{Selection}) to get to your code.
4287 If you call a function interactively, @value{GDBN} normally returns
4288 control to you when the function has finished executing. If the call
4289 raises an exception, however, the call may bypass the mechanism that
4290 returns control to you and cause your program either to abort or to
4291 simply continue running until it hits a breakpoint, catches a signal
4292 that @value{GDBN} is listening for, or exits. This is the case even if
4293 you set a catchpoint for the exception; catchpoints on exceptions are
4294 disabled within interactive calls. @xref{Calling}, for information on
4295 controlling this with @code{set unwind-on-terminating-exception}.
4298 You cannot raise an exception interactively.
4301 You cannot install an exception handler interactively.
4305 @kindex catch exception
4306 @cindex Ada exception catching
4307 @cindex catch Ada exceptions
4308 An Ada exception being raised. If an exception name is specified
4309 at the end of the command (eg @code{catch exception Program_Error}),
4310 the debugger will stop only when this specific exception is raised.
4311 Otherwise, the debugger stops execution when any Ada exception is raised.
4313 When inserting an exception catchpoint on a user-defined exception whose
4314 name is identical to one of the exceptions defined by the language, the
4315 fully qualified name must be used as the exception name. Otherwise,
4316 @value{GDBN} will assume that it should stop on the pre-defined exception
4317 rather than the user-defined one. For instance, assuming an exception
4318 called @code{Constraint_Error} is defined in package @code{Pck}, then
4319 the command to use to catch such exceptions is @kbd{catch exception
4320 Pck.Constraint_Error}.
4322 @item exception unhandled
4323 @kindex catch exception unhandled
4324 An exception that was raised but is not handled by the program.
4327 @kindex catch assert
4328 A failed Ada assertion.
4332 @cindex break on fork/exec
4333 A call to @code{exec}.
4336 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4337 @kindex catch syscall
4338 @cindex break on a system call.
4339 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4340 syscall is a mechanism for application programs to request a service
4341 from the operating system (OS) or one of the OS system services.
4342 @value{GDBN} can catch some or all of the syscalls issued by the
4343 debuggee, and show the related information for each syscall. If no
4344 argument is specified, calls to and returns from all system calls
4347 @var{name} can be any system call name that is valid for the
4348 underlying OS. Just what syscalls are valid depends on the OS. On
4349 GNU and Unix systems, you can find the full list of valid syscall
4350 names on @file{/usr/include/asm/unistd.h}.
4352 @c For MS-Windows, the syscall names and the corresponding numbers
4353 @c can be found, e.g., on this URL:
4354 @c http://www.metasploit.com/users/opcode/syscalls.html
4355 @c but we don't support Windows syscalls yet.
4357 Normally, @value{GDBN} knows in advance which syscalls are valid for
4358 each OS, so you can use the @value{GDBN} command-line completion
4359 facilities (@pxref{Completion,, command completion}) to list the
4362 You may also specify the system call numerically. A syscall's
4363 number is the value passed to the OS's syscall dispatcher to
4364 identify the requested service. When you specify the syscall by its
4365 name, @value{GDBN} uses its database of syscalls to convert the name
4366 into the corresponding numeric code, but using the number directly
4367 may be useful if @value{GDBN}'s database does not have the complete
4368 list of syscalls on your system (e.g., because @value{GDBN} lags
4369 behind the OS upgrades).
4371 The example below illustrates how this command works if you don't provide
4375 (@value{GDBP}) catch syscall
4376 Catchpoint 1 (syscall)
4378 Starting program: /tmp/catch-syscall
4380 Catchpoint 1 (call to syscall 'close'), \
4381 0xffffe424 in __kernel_vsyscall ()
4385 Catchpoint 1 (returned from syscall 'close'), \
4386 0xffffe424 in __kernel_vsyscall ()
4390 Here is an example of catching a system call by name:
4393 (@value{GDBP}) catch syscall chroot
4394 Catchpoint 1 (syscall 'chroot' [61])
4396 Starting program: /tmp/catch-syscall
4398 Catchpoint 1 (call to syscall 'chroot'), \
4399 0xffffe424 in __kernel_vsyscall ()
4403 Catchpoint 1 (returned from syscall 'chroot'), \
4404 0xffffe424 in __kernel_vsyscall ()
4408 An example of specifying a system call numerically. In the case
4409 below, the syscall number has a corresponding entry in the XML
4410 file, so @value{GDBN} finds its name and prints it:
4413 (@value{GDBP}) catch syscall 252
4414 Catchpoint 1 (syscall(s) 'exit_group')
4416 Starting program: /tmp/catch-syscall
4418 Catchpoint 1 (call to syscall 'exit_group'), \
4419 0xffffe424 in __kernel_vsyscall ()
4423 Program exited normally.
4427 However, there can be situations when there is no corresponding name
4428 in XML file for that syscall number. In this case, @value{GDBN} prints
4429 a warning message saying that it was not able to find the syscall name,
4430 but the catchpoint will be set anyway. See the example below:
4433 (@value{GDBP}) catch syscall 764
4434 warning: The number '764' does not represent a known syscall.
4435 Catchpoint 2 (syscall 764)
4439 If you configure @value{GDBN} using the @samp{--without-expat} option,
4440 it will not be able to display syscall names. Also, if your
4441 architecture does not have an XML file describing its system calls,
4442 you will not be able to see the syscall names. It is important to
4443 notice that these two features are used for accessing the syscall
4444 name database. In either case, you will see a warning like this:
4447 (@value{GDBP}) catch syscall
4448 warning: Could not open "syscalls/i386-linux.xml"
4449 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4450 GDB will not be able to display syscall names.
4451 Catchpoint 1 (syscall)
4455 Of course, the file name will change depending on your architecture and system.
4457 Still using the example above, you can also try to catch a syscall by its
4458 number. In this case, you would see something like:
4461 (@value{GDBP}) catch syscall 252
4462 Catchpoint 1 (syscall(s) 252)
4465 Again, in this case @value{GDBN} would not be able to display syscall's names.
4469 A call to @code{fork}.
4473 A call to @code{vfork}.
4475 @item load @r{[}regexp@r{]}
4476 @itemx unload @r{[}regexp@r{]}
4478 @kindex catch unload
4479 The loading or unloading of a shared library. If @var{regexp} is
4480 given, then the catchpoint will stop only if the regular expression
4481 matches one of the affected libraries.
4483 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4484 @kindex catch signal
4485 The delivery of a signal.
4487 With no arguments, this catchpoint will catch any signal that is not
4488 used internally by @value{GDBN}, specifically, all signals except
4489 @samp{SIGTRAP} and @samp{SIGINT}.
4491 With the argument @samp{all}, all signals, including those used by
4492 @value{GDBN}, will be caught. This argument cannot be used with other
4495 Otherwise, the arguments are a list of signal names as given to
4496 @code{handle} (@pxref{Signals}). Only signals specified in this list
4499 One reason that @code{catch signal} can be more useful than
4500 @code{handle} is that you can attach commands and conditions to the
4503 When a signal is caught by a catchpoint, the signal's @code{stop} and
4504 @code{print} settings, as specified by @code{handle}, are ignored.
4505 However, whether the signal is still delivered to the inferior depends
4506 on the @code{pass} setting; this can be changed in the catchpoint's
4511 @item tcatch @var{event}
4513 Set a catchpoint that is enabled only for one stop. The catchpoint is
4514 automatically deleted after the first time the event is caught.
4518 Use the @code{info break} command to list the current catchpoints.
4522 @subsection Deleting Breakpoints
4524 @cindex clearing breakpoints, watchpoints, catchpoints
4525 @cindex deleting breakpoints, watchpoints, catchpoints
4526 It is often necessary to eliminate a breakpoint, watchpoint, or
4527 catchpoint once it has done its job and you no longer want your program
4528 to stop there. This is called @dfn{deleting} the breakpoint. A
4529 breakpoint that has been deleted no longer exists; it is forgotten.
4531 With the @code{clear} command you can delete breakpoints according to
4532 where they are in your program. With the @code{delete} command you can
4533 delete individual breakpoints, watchpoints, or catchpoints by specifying
4534 their breakpoint numbers.
4536 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4537 automatically ignores breakpoints on the first instruction to be executed
4538 when you continue execution without changing the execution address.
4543 Delete any breakpoints at the next instruction to be executed in the
4544 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4545 the innermost frame is selected, this is a good way to delete a
4546 breakpoint where your program just stopped.
4548 @item clear @var{location}
4549 Delete any breakpoints set at the specified @var{location}.
4550 @xref{Specify Location}, for the various forms of @var{location}; the
4551 most useful ones are listed below:
4554 @item clear @var{function}
4555 @itemx clear @var{filename}:@var{function}
4556 Delete any breakpoints set at entry to the named @var{function}.
4558 @item clear @var{linenum}
4559 @itemx clear @var{filename}:@var{linenum}
4560 Delete any breakpoints set at or within the code of the specified
4561 @var{linenum} of the specified @var{filename}.
4564 @cindex delete breakpoints
4566 @kindex d @r{(@code{delete})}
4567 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4568 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4569 ranges specified as arguments. If no argument is specified, delete all
4570 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4571 confirm off}). You can abbreviate this command as @code{d}.
4575 @subsection Disabling Breakpoints
4577 @cindex enable/disable a breakpoint
4578 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4579 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4580 it had been deleted, but remembers the information on the breakpoint so
4581 that you can @dfn{enable} it again later.
4583 You disable and enable breakpoints, watchpoints, and catchpoints with
4584 the @code{enable} and @code{disable} commands, optionally specifying
4585 one or more breakpoint numbers as arguments. Use @code{info break} to
4586 print a list of all breakpoints, watchpoints, and catchpoints if you
4587 do not know which numbers to use.
4589 Disabling and enabling a breakpoint that has multiple locations
4590 affects all of its locations.
4592 A breakpoint, watchpoint, or catchpoint can have any of several
4593 different states of enablement:
4597 Enabled. The breakpoint stops your program. A breakpoint set
4598 with the @code{break} command starts out in this state.
4600 Disabled. The breakpoint has no effect on your program.
4602 Enabled once. The breakpoint stops your program, but then becomes
4605 Enabled for a count. The breakpoint stops your program for the next
4606 N times, then becomes disabled.
4608 Enabled for deletion. The breakpoint stops your program, but
4609 immediately after it does so it is deleted permanently. A breakpoint
4610 set with the @code{tbreak} command starts out in this state.
4613 You can use the following commands to enable or disable breakpoints,
4614 watchpoints, and catchpoints:
4618 @kindex dis @r{(@code{disable})}
4619 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4620 Disable the specified breakpoints---or all breakpoints, if none are
4621 listed. A disabled breakpoint has no effect but is not forgotten. All
4622 options such as ignore-counts, conditions and commands are remembered in
4623 case the breakpoint is enabled again later. You may abbreviate
4624 @code{disable} as @code{dis}.
4627 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4628 Enable the specified breakpoints (or all defined breakpoints). They
4629 become effective once again in stopping your program.
4631 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4632 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4633 of these breakpoints immediately after stopping your program.
4635 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4636 Enable the specified breakpoints temporarily. @value{GDBN} records
4637 @var{count} with each of the specified breakpoints, and decrements a
4638 breakpoint's count when it is hit. When any count reaches 0,
4639 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4640 count (@pxref{Conditions, ,Break Conditions}), that will be
4641 decremented to 0 before @var{count} is affected.
4643 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4644 Enable the specified breakpoints to work once, then die. @value{GDBN}
4645 deletes any of these breakpoints as soon as your program stops there.
4646 Breakpoints set by the @code{tbreak} command start out in this state.
4649 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4650 @c confusing: tbreak is also initially enabled.
4651 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4652 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4653 subsequently, they become disabled or enabled only when you use one of
4654 the commands above. (The command @code{until} can set and delete a
4655 breakpoint of its own, but it does not change the state of your other
4656 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4660 @subsection Break Conditions
4661 @cindex conditional breakpoints
4662 @cindex breakpoint conditions
4664 @c FIXME what is scope of break condition expr? Context where wanted?
4665 @c in particular for a watchpoint?
4666 The simplest sort of breakpoint breaks every time your program reaches a
4667 specified place. You can also specify a @dfn{condition} for a
4668 breakpoint. A condition is just a Boolean expression in your
4669 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4670 a condition evaluates the expression each time your program reaches it,
4671 and your program stops only if the condition is @emph{true}.
4673 This is the converse of using assertions for program validation; in that
4674 situation, you want to stop when the assertion is violated---that is,
4675 when the condition is false. In C, if you want to test an assertion expressed
4676 by the condition @var{assert}, you should set the condition
4677 @samp{! @var{assert}} on the appropriate breakpoint.
4679 Conditions are also accepted for watchpoints; you may not need them,
4680 since a watchpoint is inspecting the value of an expression anyhow---but
4681 it might be simpler, say, to just set a watchpoint on a variable name,
4682 and specify a condition that tests whether the new value is an interesting
4685 Break conditions can have side effects, and may even call functions in
4686 your program. This can be useful, for example, to activate functions
4687 that log program progress, or to use your own print functions to
4688 format special data structures. The effects are completely predictable
4689 unless there is another enabled breakpoint at the same address. (In
4690 that case, @value{GDBN} might see the other breakpoint first and stop your
4691 program without checking the condition of this one.) Note that
4692 breakpoint commands are usually more convenient and flexible than break
4694 purpose of performing side effects when a breakpoint is reached
4695 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4697 Breakpoint conditions can also be evaluated on the target's side if
4698 the target supports it. Instead of evaluating the conditions locally,
4699 @value{GDBN} encodes the expression into an agent expression
4700 (@pxref{Agent Expressions}) suitable for execution on the target,
4701 independently of @value{GDBN}. Global variables become raw memory
4702 locations, locals become stack accesses, and so forth.
4704 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4705 when its condition evaluates to true. This mechanism may provide faster
4706 response times depending on the performance characteristics of the target
4707 since it does not need to keep @value{GDBN} informed about
4708 every breakpoint trigger, even those with false conditions.
4710 Break conditions can be specified when a breakpoint is set, by using
4711 @samp{if} in the arguments to the @code{break} command. @xref{Set
4712 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4713 with the @code{condition} command.
4715 You can also use the @code{if} keyword with the @code{watch} command.
4716 The @code{catch} command does not recognize the @code{if} keyword;
4717 @code{condition} is the only way to impose a further condition on a
4722 @item condition @var{bnum} @var{expression}
4723 Specify @var{expression} as the break condition for breakpoint,
4724 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4725 breakpoint @var{bnum} stops your program only if the value of
4726 @var{expression} is true (nonzero, in C). When you use
4727 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4728 syntactic correctness, and to determine whether symbols in it have
4729 referents in the context of your breakpoint. If @var{expression} uses
4730 symbols not referenced in the context of the breakpoint, @value{GDBN}
4731 prints an error message:
4734 No symbol "foo" in current context.
4739 not actually evaluate @var{expression} at the time the @code{condition}
4740 command (or a command that sets a breakpoint with a condition, like
4741 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4743 @item condition @var{bnum}
4744 Remove the condition from breakpoint number @var{bnum}. It becomes
4745 an ordinary unconditional breakpoint.
4748 @cindex ignore count (of breakpoint)
4749 A special case of a breakpoint condition is to stop only when the
4750 breakpoint has been reached a certain number of times. This is so
4751 useful that there is a special way to do it, using the @dfn{ignore
4752 count} of the breakpoint. Every breakpoint has an ignore count, which
4753 is an integer. Most of the time, the ignore count is zero, and
4754 therefore has no effect. But if your program reaches a breakpoint whose
4755 ignore count is positive, then instead of stopping, it just decrements
4756 the ignore count by one and continues. As a result, if the ignore count
4757 value is @var{n}, the breakpoint does not stop the next @var{n} times
4758 your program reaches it.
4762 @item ignore @var{bnum} @var{count}
4763 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4764 The next @var{count} times the breakpoint is reached, your program's
4765 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4768 To make the breakpoint stop the next time it is reached, specify
4771 When you use @code{continue} to resume execution of your program from a
4772 breakpoint, you can specify an ignore count directly as an argument to
4773 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4774 Stepping,,Continuing and Stepping}.
4776 If a breakpoint has a positive ignore count and a condition, the
4777 condition is not checked. Once the ignore count reaches zero,
4778 @value{GDBN} resumes checking the condition.
4780 You could achieve the effect of the ignore count with a condition such
4781 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4782 is decremented each time. @xref{Convenience Vars, ,Convenience
4786 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4789 @node Break Commands
4790 @subsection Breakpoint Command Lists
4792 @cindex breakpoint commands
4793 You can give any breakpoint (or watchpoint or catchpoint) a series of
4794 commands to execute when your program stops due to that breakpoint. For
4795 example, you might want to print the values of certain expressions, or
4796 enable other breakpoints.
4800 @kindex end@r{ (breakpoint commands)}
4801 @item commands @r{[}@var{range}@dots{}@r{]}
4802 @itemx @dots{} @var{command-list} @dots{}
4804 Specify a list of commands for the given breakpoints. The commands
4805 themselves appear on the following lines. Type a line containing just
4806 @code{end} to terminate the commands.
4808 To remove all commands from a breakpoint, type @code{commands} and
4809 follow it immediately with @code{end}; that is, give no commands.
4811 With no argument, @code{commands} refers to the last breakpoint,
4812 watchpoint, or catchpoint set (not to the breakpoint most recently
4813 encountered). If the most recent breakpoints were set with a single
4814 command, then the @code{commands} will apply to all the breakpoints
4815 set by that command. This applies to breakpoints set by
4816 @code{rbreak}, and also applies when a single @code{break} command
4817 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4821 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4822 disabled within a @var{command-list}.
4824 You can use breakpoint commands to start your program up again. Simply
4825 use the @code{continue} command, or @code{step}, or any other command
4826 that resumes execution.
4828 Any other commands in the command list, after a command that resumes
4829 execution, are ignored. This is because any time you resume execution
4830 (even with a simple @code{next} or @code{step}), you may encounter
4831 another breakpoint---which could have its own command list, leading to
4832 ambiguities about which list to execute.
4835 If the first command you specify in a command list is @code{silent}, the
4836 usual message about stopping at a breakpoint is not printed. This may
4837 be desirable for breakpoints that are to print a specific message and
4838 then continue. If none of the remaining commands print anything, you
4839 see no sign that the breakpoint was reached. @code{silent} is
4840 meaningful only at the beginning of a breakpoint command list.
4842 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4843 print precisely controlled output, and are often useful in silent
4844 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4846 For example, here is how you could use breakpoint commands to print the
4847 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4853 printf "x is %d\n",x
4858 One application for breakpoint commands is to compensate for one bug so
4859 you can test for another. Put a breakpoint just after the erroneous line
4860 of code, give it a condition to detect the case in which something
4861 erroneous has been done, and give it commands to assign correct values
4862 to any variables that need them. End with the @code{continue} command
4863 so that your program does not stop, and start with the @code{silent}
4864 command so that no output is produced. Here is an example:
4875 @node Dynamic Printf
4876 @subsection Dynamic Printf
4878 @cindex dynamic printf
4880 The dynamic printf command @code{dprintf} combines a breakpoint with
4881 formatted printing of your program's data to give you the effect of
4882 inserting @code{printf} calls into your program on-the-fly, without
4883 having to recompile it.
4885 In its most basic form, the output goes to the GDB console. However,
4886 you can set the variable @code{dprintf-style} for alternate handling.
4887 For instance, you can ask to format the output by calling your
4888 program's @code{printf} function. This has the advantage that the
4889 characters go to the program's output device, so they can recorded in
4890 redirects to files and so forth.
4892 If you are doing remote debugging with a stub or agent, you can also
4893 ask to have the printf handled by the remote agent. In addition to
4894 ensuring that the output goes to the remote program's device along
4895 with any other output the program might produce, you can also ask that
4896 the dprintf remain active even after disconnecting from the remote
4897 target. Using the stub/agent is also more efficient, as it can do
4898 everything without needing to communicate with @value{GDBN}.
4902 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4903 Whenever execution reaches @var{location}, print the values of one or
4904 more @var{expressions} under the control of the string @var{template}.
4905 To print several values, separate them with commas.
4907 @item set dprintf-style @var{style}
4908 Set the dprintf output to be handled in one of several different
4909 styles enumerated below. A change of style affects all existing
4910 dynamic printfs immediately. (If you need individual control over the
4911 print commands, simply define normal breakpoints with
4912 explicitly-supplied command lists.)
4915 @kindex dprintf-style gdb
4916 Handle the output using the @value{GDBN} @code{printf} command.
4919 @kindex dprintf-style call
4920 Handle the output by calling a function in your program (normally
4924 @kindex dprintf-style agent
4925 Have the remote debugging agent (such as @code{gdbserver}) handle
4926 the output itself. This style is only available for agents that
4927 support running commands on the target.
4929 @item set dprintf-function @var{function}
4930 Set the function to call if the dprintf style is @code{call}. By
4931 default its value is @code{printf}. You may set it to any expression.
4932 that @value{GDBN} can evaluate to a function, as per the @code{call}
4935 @item set dprintf-channel @var{channel}
4936 Set a ``channel'' for dprintf. If set to a non-empty value,
4937 @value{GDBN} will evaluate it as an expression and pass the result as
4938 a first argument to the @code{dprintf-function}, in the manner of
4939 @code{fprintf} and similar functions. Otherwise, the dprintf format
4940 string will be the first argument, in the manner of @code{printf}.
4942 As an example, if you wanted @code{dprintf} output to go to a logfile
4943 that is a standard I/O stream assigned to the variable @code{mylog},
4944 you could do the following:
4947 (gdb) set dprintf-style call
4948 (gdb) set dprintf-function fprintf
4949 (gdb) set dprintf-channel mylog
4950 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4951 Dprintf 1 at 0x123456: file main.c, line 25.
4953 1 dprintf keep y 0x00123456 in main at main.c:25
4954 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4959 Note that the @code{info break} displays the dynamic printf commands
4960 as normal breakpoint commands; you can thus easily see the effect of
4961 the variable settings.
4963 @item set disconnected-dprintf on
4964 @itemx set disconnected-dprintf off
4965 @kindex set disconnected-dprintf
4966 Choose whether @code{dprintf} commands should continue to run if
4967 @value{GDBN} has disconnected from the target. This only applies
4968 if the @code{dprintf-style} is @code{agent}.
4970 @item show disconnected-dprintf off
4971 @kindex show disconnected-dprintf
4972 Show the current choice for disconnected @code{dprintf}.
4976 @value{GDBN} does not check the validity of function and channel,
4977 relying on you to supply values that are meaningful for the contexts
4978 in which they are being used. For instance, the function and channel
4979 may be the values of local variables, but if that is the case, then
4980 all enabled dynamic prints must be at locations within the scope of
4981 those locals. If evaluation fails, @value{GDBN} will report an error.
4983 @node Save Breakpoints
4984 @subsection How to save breakpoints to a file
4986 To save breakpoint definitions to a file use the @w{@code{save
4987 breakpoints}} command.
4990 @kindex save breakpoints
4991 @cindex save breakpoints to a file for future sessions
4992 @item save breakpoints [@var{filename}]
4993 This command saves all current breakpoint definitions together with
4994 their commands and ignore counts, into a file @file{@var{filename}}
4995 suitable for use in a later debugging session. This includes all
4996 types of breakpoints (breakpoints, watchpoints, catchpoints,
4997 tracepoints). To read the saved breakpoint definitions, use the
4998 @code{source} command (@pxref{Command Files}). Note that watchpoints
4999 with expressions involving local variables may fail to be recreated
5000 because it may not be possible to access the context where the
5001 watchpoint is valid anymore. Because the saved breakpoint definitions
5002 are simply a sequence of @value{GDBN} commands that recreate the
5003 breakpoints, you can edit the file in your favorite editing program,
5004 and remove the breakpoint definitions you're not interested in, or
5005 that can no longer be recreated.
5008 @node Static Probe Points
5009 @subsection Static Probe Points
5011 @cindex static probe point, SystemTap
5012 @cindex static probe point, DTrace
5013 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
5014 for Statically Defined Tracing, and the probes are designed to have a tiny
5015 runtime code and data footprint, and no dynamic relocations.
5017 Currently, the following types of probes are supported on
5018 ELF-compatible systems:
5022 @item @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
5023 @acronym{SDT} probes@footnote{See
5024 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
5025 for more information on how to add @code{SystemTap} @acronym{SDT}
5026 probes in your applications.}. @code{SystemTap} probes are usable
5027 from assembly, C and C@t{++} languages@footnote{See
5028 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
5029 for a good reference on how the @acronym{SDT} probes are implemented.}.
5031 @item @code{DTrace} (@uref{http://oss.oracle.com/projects/DTrace})
5032 @acronym{USDT} probes. @code{DTrace} probes are usable from C and
5036 @cindex semaphores on static probe points
5037 Some @code{SystemTap} probes have an associated semaphore variable;
5038 for instance, this happens automatically if you defined your probe
5039 using a DTrace-style @file{.d} file. If your probe has a semaphore,
5040 @value{GDBN} will automatically enable it when you specify a
5041 breakpoint using the @samp{-probe-stap} notation. But, if you put a
5042 breakpoint at a probe's location by some other method (e.g.,
5043 @code{break file:line}), then @value{GDBN} will not automatically set
5044 the semaphore. @code{DTrace} probes do not support semaphores.
5046 You can examine the available static static probes using @code{info
5047 probes}, with optional arguments:
5051 @item info probes @r{[}@var{type}@r{]} @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5052 If given, @var{type} is either @code{stap} for listing
5053 @code{SystemTap} probes or @code{dtrace} for listing @code{DTrace}
5054 probes. If omitted all probes are listed regardless of their types.
5056 If given, @var{provider} is a regular expression used to match against provider
5057 names when selecting which probes to list. If omitted, probes by all
5058 probes from all providers are listed.
5060 If given, @var{name} is a regular expression to match against probe names
5061 when selecting which probes to list. If omitted, probe names are not
5062 considered when deciding whether to display them.
5064 If given, @var{objfile} is a regular expression used to select which
5065 object files (executable or shared libraries) to examine. If not
5066 given, all object files are considered.
5068 @item info probes all
5069 List the available static probes, from all types.
5072 @cindex enabling and disabling probes
5073 Some probe points can be enabled and/or disabled. The effect of
5074 enabling or disabling a probe depends on the type of probe being
5075 handled. Some @code{DTrace} probes can be enabled or
5076 disabled, but @code{SystemTap} probes cannot be disabled.
5078 You can enable (or disable) one or more probes using the following
5079 commands, with optional arguments:
5082 @kindex enable probes
5083 @item enable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5084 If given, @var{provider} is a regular expression used to match against
5085 provider names when selecting which probes to enable. If omitted,
5086 all probes from all providers are enabled.
5088 If given, @var{name} is a regular expression to match against probe
5089 names when selecting which probes to enable. If omitted, probe names
5090 are not considered when deciding whether to enable them.
5092 If given, @var{objfile} is a regular expression used to select which
5093 object files (executable or shared libraries) to examine. If not
5094 given, all object files are considered.
5096 @kindex disable probes
5097 @item disable probes @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
5098 See the @code{enable probes} command above for a description of the
5099 optional arguments accepted by this command.
5102 @vindex $_probe_arg@r{, convenience variable}
5103 A probe may specify up to twelve arguments. These are available at the
5104 point at which the probe is defined---that is, when the current PC is
5105 at the probe's location. The arguments are available using the
5106 convenience variables (@pxref{Convenience Vars})
5107 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. In @code{SystemTap}
5108 probes each probe argument is an integer of the appropriate size;
5109 types are not preserved. In @code{DTrace} probes types are preserved
5110 provided that they are recognized as such by @value{GDBN}; otherwise
5111 the value of the probe argument will be a long integer. The
5112 convenience variable @code{$_probe_argc} holds the number of arguments
5113 at the current probe point.
5115 These variables are always available, but attempts to access them at
5116 any location other than a probe point will cause @value{GDBN} to give
5120 @c @ifclear BARETARGET
5121 @node Error in Breakpoints
5122 @subsection ``Cannot insert breakpoints''
5124 If you request too many active hardware-assisted breakpoints and
5125 watchpoints, you will see this error message:
5127 @c FIXME: the precise wording of this message may change; the relevant
5128 @c source change is not committed yet (Sep 3, 1999).
5130 Stopped; cannot insert breakpoints.
5131 You may have requested too many hardware breakpoints and watchpoints.
5135 This message is printed when you attempt to resume the program, since
5136 only then @value{GDBN} knows exactly how many hardware breakpoints and
5137 watchpoints it needs to insert.
5139 When this message is printed, you need to disable or remove some of the
5140 hardware-assisted breakpoints and watchpoints, and then continue.
5142 @node Breakpoint-related Warnings
5143 @subsection ``Breakpoint address adjusted...''
5144 @cindex breakpoint address adjusted
5146 Some processor architectures place constraints on the addresses at
5147 which breakpoints may be placed. For architectures thus constrained,
5148 @value{GDBN} will attempt to adjust the breakpoint's address to comply
5149 with the constraints dictated by the architecture.
5151 One example of such an architecture is the Fujitsu FR-V. The FR-V is
5152 a VLIW architecture in which a number of RISC-like instructions may be
5153 bundled together for parallel execution. The FR-V architecture
5154 constrains the location of a breakpoint instruction within such a
5155 bundle to the instruction with the lowest address. @value{GDBN}
5156 honors this constraint by adjusting a breakpoint's address to the
5157 first in the bundle.
5159 It is not uncommon for optimized code to have bundles which contain
5160 instructions from different source statements, thus it may happen that
5161 a breakpoint's address will be adjusted from one source statement to
5162 another. Since this adjustment may significantly alter @value{GDBN}'s
5163 breakpoint related behavior from what the user expects, a warning is
5164 printed when the breakpoint is first set and also when the breakpoint
5167 A warning like the one below is printed when setting a breakpoint
5168 that's been subject to address adjustment:
5171 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
5174 Such warnings are printed both for user settable and @value{GDBN}'s
5175 internal breakpoints. If you see one of these warnings, you should
5176 verify that a breakpoint set at the adjusted address will have the
5177 desired affect. If not, the breakpoint in question may be removed and
5178 other breakpoints may be set which will have the desired behavior.
5179 E.g., it may be sufficient to place the breakpoint at a later
5180 instruction. A conditional breakpoint may also be useful in some
5181 cases to prevent the breakpoint from triggering too often.
5183 @value{GDBN} will also issue a warning when stopping at one of these
5184 adjusted breakpoints:
5187 warning: Breakpoint 1 address previously adjusted from 0x00010414
5191 When this warning is encountered, it may be too late to take remedial
5192 action except in cases where the breakpoint is hit earlier or more
5193 frequently than expected.
5195 @node Continuing and Stepping
5196 @section Continuing and Stepping
5200 @cindex resuming execution
5201 @dfn{Continuing} means resuming program execution until your program
5202 completes normally. In contrast, @dfn{stepping} means executing just
5203 one more ``step'' of your program, where ``step'' may mean either one
5204 line of source code, or one machine instruction (depending on what
5205 particular command you use). Either when continuing or when stepping,
5206 your program may stop even sooner, due to a breakpoint or a signal. (If
5207 it stops due to a signal, you may want to use @code{handle}, or use
5208 @samp{signal 0} to resume execution (@pxref{Signals, ,Signals}),
5209 or you may step into the signal's handler (@pxref{stepping and signal
5214 @kindex c @r{(@code{continue})}
5215 @kindex fg @r{(resume foreground execution)}
5216 @item continue @r{[}@var{ignore-count}@r{]}
5217 @itemx c @r{[}@var{ignore-count}@r{]}
5218 @itemx fg @r{[}@var{ignore-count}@r{]}
5219 Resume program execution, at the address where your program last stopped;
5220 any breakpoints set at that address are bypassed. The optional argument
5221 @var{ignore-count} allows you to specify a further number of times to
5222 ignore a breakpoint at this location; its effect is like that of
5223 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
5225 The argument @var{ignore-count} is meaningful only when your program
5226 stopped due to a breakpoint. At other times, the argument to
5227 @code{continue} is ignored.
5229 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
5230 debugged program is deemed to be the foreground program) are provided
5231 purely for convenience, and have exactly the same behavior as
5235 To resume execution at a different place, you can use @code{return}
5236 (@pxref{Returning, ,Returning from a Function}) to go back to the
5237 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
5238 Different Address}) to go to an arbitrary location in your program.
5240 A typical technique for using stepping is to set a breakpoint
5241 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
5242 beginning of the function or the section of your program where a problem
5243 is believed to lie, run your program until it stops at that breakpoint,
5244 and then step through the suspect area, examining the variables that are
5245 interesting, until you see the problem happen.
5249 @kindex s @r{(@code{step})}
5251 Continue running your program until control reaches a different source
5252 line, then stop it and return control to @value{GDBN}. This command is
5253 abbreviated @code{s}.
5256 @c "without debugging information" is imprecise; actually "without line
5257 @c numbers in the debugging information". (gcc -g1 has debugging info but
5258 @c not line numbers). But it seems complex to try to make that
5259 @c distinction here.
5260 @emph{Warning:} If you use the @code{step} command while control is
5261 within a function that was compiled without debugging information,
5262 execution proceeds until control reaches a function that does have
5263 debugging information. Likewise, it will not step into a function which
5264 is compiled without debugging information. To step through functions
5265 without debugging information, use the @code{stepi} command, described
5269 The @code{step} command only stops at the first instruction of a source
5270 line. This prevents the multiple stops that could otherwise occur in
5271 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5272 to stop if a function that has debugging information is called within
5273 the line. In other words, @code{step} @emph{steps inside} any functions
5274 called within the line.
5276 Also, the @code{step} command only enters a function if there is line
5277 number information for the function. Otherwise it acts like the
5278 @code{next} command. This avoids problems when using @code{cc -gl}
5279 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5280 was any debugging information about the routine.
5282 @item step @var{count}
5283 Continue running as in @code{step}, but do so @var{count} times. If a
5284 breakpoint is reached, or a signal not related to stepping occurs before
5285 @var{count} steps, stepping stops right away.
5288 @kindex n @r{(@code{next})}
5289 @item next @r{[}@var{count}@r{]}
5290 Continue to the next source line in the current (innermost) stack frame.
5291 This is similar to @code{step}, but function calls that appear within
5292 the line of code are executed without stopping. Execution stops when
5293 control reaches a different line of code at the original stack level
5294 that was executing when you gave the @code{next} command. This command
5295 is abbreviated @code{n}.
5297 An argument @var{count} is a repeat count, as for @code{step}.
5300 @c FIX ME!! Do we delete this, or is there a way it fits in with
5301 @c the following paragraph? --- Vctoria
5303 @c @code{next} within a function that lacks debugging information acts like
5304 @c @code{step}, but any function calls appearing within the code of the
5305 @c function are executed without stopping.
5307 The @code{next} command only stops at the first instruction of a
5308 source line. This prevents multiple stops that could otherwise occur in
5309 @code{switch} statements, @code{for} loops, etc.
5311 @kindex set step-mode
5313 @cindex functions without line info, and stepping
5314 @cindex stepping into functions with no line info
5315 @itemx set step-mode on
5316 The @code{set step-mode on} command causes the @code{step} command to
5317 stop at the first instruction of a function which contains no debug line
5318 information rather than stepping over it.
5320 This is useful in cases where you may be interested in inspecting the
5321 machine instructions of a function which has no symbolic info and do not
5322 want @value{GDBN} to automatically skip over this function.
5324 @item set step-mode off
5325 Causes the @code{step} command to step over any functions which contains no
5326 debug information. This is the default.
5328 @item show step-mode
5329 Show whether @value{GDBN} will stop in or step over functions without
5330 source line debug information.
5333 @kindex fin @r{(@code{finish})}
5335 Continue running until just after function in the selected stack frame
5336 returns. Print the returned value (if any). This command can be
5337 abbreviated as @code{fin}.
5339 Contrast this with the @code{return} command (@pxref{Returning,
5340 ,Returning from a Function}).
5343 @kindex u @r{(@code{until})}
5344 @cindex run until specified location
5347 Continue running until a source line past the current line, in the
5348 current stack frame, is reached. This command is used to avoid single
5349 stepping through a loop more than once. It is like the @code{next}
5350 command, except that when @code{until} encounters a jump, it
5351 automatically continues execution until the program counter is greater
5352 than the address of the jump.
5354 This means that when you reach the end of a loop after single stepping
5355 though it, @code{until} makes your program continue execution until it
5356 exits the loop. In contrast, a @code{next} command at the end of a loop
5357 simply steps back to the beginning of the loop, which forces you to step
5358 through the next iteration.
5360 @code{until} always stops your program if it attempts to exit the current
5363 @code{until} may produce somewhat counterintuitive results if the order
5364 of machine code does not match the order of the source lines. For
5365 example, in the following excerpt from a debugging session, the @code{f}
5366 (@code{frame}) command shows that execution is stopped at line
5367 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5371 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5373 (@value{GDBP}) until
5374 195 for ( ; argc > 0; NEXTARG) @{
5377 This happened because, for execution efficiency, the compiler had
5378 generated code for the loop closure test at the end, rather than the
5379 start, of the loop---even though the test in a C @code{for}-loop is
5380 written before the body of the loop. The @code{until} command appeared
5381 to step back to the beginning of the loop when it advanced to this
5382 expression; however, it has not really gone to an earlier
5383 statement---not in terms of the actual machine code.
5385 @code{until} with no argument works by means of single
5386 instruction stepping, and hence is slower than @code{until} with an
5389 @item until @var{location}
5390 @itemx u @var{location}
5391 Continue running your program until either the specified @var{location} is
5392 reached, or the current stack frame returns. The location is any of
5393 the forms described in @ref{Specify Location}.
5394 This form of the command uses temporary breakpoints, and
5395 hence is quicker than @code{until} without an argument. The specified
5396 location is actually reached only if it is in the current frame. This
5397 implies that @code{until} can be used to skip over recursive function
5398 invocations. For instance in the code below, if the current location is
5399 line @code{96}, issuing @code{until 99} will execute the program up to
5400 line @code{99} in the same invocation of factorial, i.e., after the inner
5401 invocations have returned.
5404 94 int factorial (int value)
5406 96 if (value > 1) @{
5407 97 value *= factorial (value - 1);
5414 @kindex advance @var{location}
5415 @item advance @var{location}
5416 Continue running the program up to the given @var{location}. An argument is
5417 required, which should be of one of the forms described in
5418 @ref{Specify Location}.
5419 Execution will also stop upon exit from the current stack
5420 frame. This command is similar to @code{until}, but @code{advance} will
5421 not skip over recursive function calls, and the target location doesn't
5422 have to be in the same frame as the current one.
5426 @kindex si @r{(@code{stepi})}
5428 @itemx stepi @var{arg}
5430 Execute one machine instruction, then stop and return to the debugger.
5432 It is often useful to do @samp{display/i $pc} when stepping by machine
5433 instructions. This makes @value{GDBN} automatically display the next
5434 instruction to be executed, each time your program stops. @xref{Auto
5435 Display,, Automatic Display}.
5437 An argument is a repeat count, as in @code{step}.
5441 @kindex ni @r{(@code{nexti})}
5443 @itemx nexti @var{arg}
5445 Execute one machine instruction, but if it is a function call,
5446 proceed until the function returns.
5448 An argument is a repeat count, as in @code{next}.
5452 @anchor{range stepping}
5453 @cindex range stepping
5454 @cindex target-assisted range stepping
5455 By default, and if available, @value{GDBN} makes use of
5456 target-assisted @dfn{range stepping}. In other words, whenever you
5457 use a stepping command (e.g., @code{step}, @code{next}), @value{GDBN}
5458 tells the target to step the corresponding range of instruction
5459 addresses instead of issuing multiple single-steps. This speeds up
5460 line stepping, particularly for remote targets. Ideally, there should
5461 be no reason you would want to turn range stepping off. However, it's
5462 possible that a bug in the debug info, a bug in the remote stub (for
5463 remote targets), or even a bug in @value{GDBN} could make line
5464 stepping behave incorrectly when target-assisted range stepping is
5465 enabled. You can use the following command to turn off range stepping
5469 @kindex set range-stepping
5470 @kindex show range-stepping
5471 @item set range-stepping
5472 @itemx show range-stepping
5473 Control whether range stepping is enabled.
5475 If @code{on}, and the target supports it, @value{GDBN} tells the
5476 target to step a range of addresses itself, instead of issuing
5477 multiple single-steps. If @code{off}, @value{GDBN} always issues
5478 single-steps, even if range stepping is supported by the target. The
5479 default is @code{on}.
5483 @node Skipping Over Functions and Files
5484 @section Skipping Over Functions and Files
5485 @cindex skipping over functions and files
5487 The program you are debugging may contain some functions which are
5488 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5489 skip a function or all functions in a file when stepping.
5491 For example, consider the following C function:
5502 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5503 are not interested in stepping through @code{boring}. If you run @code{step}
5504 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5505 step over both @code{foo} and @code{boring}!
5507 One solution is to @code{step} into @code{boring} and use the @code{finish}
5508 command to immediately exit it. But this can become tedious if @code{boring}
5509 is called from many places.
5511 A more flexible solution is to execute @kbd{skip boring}. This instructs
5512 @value{GDBN} never to step into @code{boring}. Now when you execute
5513 @code{step} at line 103, you'll step over @code{boring} and directly into
5516 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5517 example, @code{skip file boring.c}.
5520 @kindex skip function
5521 @item skip @r{[}@var{linespec}@r{]}
5522 @itemx skip function @r{[}@var{linespec}@r{]}
5523 After running this command, the function named by @var{linespec} or the
5524 function containing the line named by @var{linespec} will be skipped over when
5525 stepping. @xref{Specify Location}.
5527 If you do not specify @var{linespec}, the function you're currently debugging
5530 (If you have a function called @code{file} that you want to skip, use
5531 @kbd{skip function file}.)
5534 @item skip file @r{[}@var{filename}@r{]}
5535 After running this command, any function whose source lives in @var{filename}
5536 will be skipped over when stepping.
5538 If you do not specify @var{filename}, functions whose source lives in the file
5539 you're currently debugging will be skipped.
5542 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5543 These are the commands for managing your list of skips:
5547 @item info skip @r{[}@var{range}@r{]}
5548 Print details about the specified skip(s). If @var{range} is not specified,
5549 print a table with details about all functions and files marked for skipping.
5550 @code{info skip} prints the following information about each skip:
5554 A number identifying this skip.
5556 The type of this skip, either @samp{function} or @samp{file}.
5557 @item Enabled or Disabled
5558 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5560 For function skips, this column indicates the address in memory of the function
5561 being skipped. If you've set a function skip on a function which has not yet
5562 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5563 which has the function is loaded, @code{info skip} will show the function's
5566 For file skips, this field contains the filename being skipped. For functions
5567 skips, this field contains the function name and its line number in the file
5568 where it is defined.
5572 @item skip delete @r{[}@var{range}@r{]}
5573 Delete the specified skip(s). If @var{range} is not specified, delete all
5577 @item skip enable @r{[}@var{range}@r{]}
5578 Enable the specified skip(s). If @var{range} is not specified, enable all
5581 @kindex skip disable
5582 @item skip disable @r{[}@var{range}@r{]}
5583 Disable the specified skip(s). If @var{range} is not specified, disable all
5592 A signal is an asynchronous event that can happen in a program. The
5593 operating system defines the possible kinds of signals, and gives each
5594 kind a name and a number. For example, in Unix @code{SIGINT} is the
5595 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5596 @code{SIGSEGV} is the signal a program gets from referencing a place in
5597 memory far away from all the areas in use; @code{SIGALRM} occurs when
5598 the alarm clock timer goes off (which happens only if your program has
5599 requested an alarm).
5601 @cindex fatal signals
5602 Some signals, including @code{SIGALRM}, are a normal part of the
5603 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5604 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5605 program has not specified in advance some other way to handle the signal.
5606 @code{SIGINT} does not indicate an error in your program, but it is normally
5607 fatal so it can carry out the purpose of the interrupt: to kill the program.
5609 @value{GDBN} has the ability to detect any occurrence of a signal in your
5610 program. You can tell @value{GDBN} in advance what to do for each kind of
5613 @cindex handling signals
5614 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5615 @code{SIGALRM} be silently passed to your program
5616 (so as not to interfere with their role in the program's functioning)
5617 but to stop your program immediately whenever an error signal happens.
5618 You can change these settings with the @code{handle} command.
5621 @kindex info signals
5625 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5626 handle each one. You can use this to see the signal numbers of all
5627 the defined types of signals.
5629 @item info signals @var{sig}
5630 Similar, but print information only about the specified signal number.
5632 @code{info handle} is an alias for @code{info signals}.
5634 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5635 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5636 for details about this command.
5639 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5640 Change the way @value{GDBN} handles signal @var{signal}. The @var{signal}
5641 can be the number of a signal or its name (with or without the
5642 @samp{SIG} at the beginning); a list of signal numbers of the form
5643 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5644 known signals. Optional arguments @var{keywords}, described below,
5645 say what change to make.
5649 The keywords allowed by the @code{handle} command can be abbreviated.
5650 Their full names are:
5654 @value{GDBN} should not stop your program when this signal happens. It may
5655 still print a message telling you that the signal has come in.
5658 @value{GDBN} should stop your program when this signal happens. This implies
5659 the @code{print} keyword as well.
5662 @value{GDBN} should print a message when this signal happens.
5665 @value{GDBN} should not mention the occurrence of the signal at all. This
5666 implies the @code{nostop} keyword as well.
5670 @value{GDBN} should allow your program to see this signal; your program
5671 can handle the signal, or else it may terminate if the signal is fatal
5672 and not handled. @code{pass} and @code{noignore} are synonyms.
5676 @value{GDBN} should not allow your program to see this signal.
5677 @code{nopass} and @code{ignore} are synonyms.
5681 When a signal stops your program, the signal is not visible to the
5683 continue. Your program sees the signal then, if @code{pass} is in
5684 effect for the signal in question @emph{at that time}. In other words,
5685 after @value{GDBN} reports a signal, you can use the @code{handle}
5686 command with @code{pass} or @code{nopass} to control whether your
5687 program sees that signal when you continue.
5689 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5690 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5691 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5694 You can also use the @code{signal} command to prevent your program from
5695 seeing a signal, or cause it to see a signal it normally would not see,
5696 or to give it any signal at any time. For example, if your program stopped
5697 due to some sort of memory reference error, you might store correct
5698 values into the erroneous variables and continue, hoping to see more
5699 execution; but your program would probably terminate immediately as
5700 a result of the fatal signal once it saw the signal. To prevent this,
5701 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5704 @cindex stepping and signal handlers
5705 @anchor{stepping and signal handlers}
5707 @value{GDBN} optimizes for stepping the mainline code. If a signal
5708 that has @code{handle nostop} and @code{handle pass} set arrives while
5709 a stepping command (e.g., @code{stepi}, @code{step}, @code{next}) is
5710 in progress, @value{GDBN} lets the signal handler run and then resumes
5711 stepping the mainline code once the signal handler returns. In other
5712 words, @value{GDBN} steps over the signal handler. This prevents
5713 signals that you've specified as not interesting (with @code{handle
5714 nostop}) from changing the focus of debugging unexpectedly. Note that
5715 the signal handler itself may still hit a breakpoint, stop for another
5716 signal that has @code{handle stop} in effect, or for any other event
5717 that normally results in stopping the stepping command sooner. Also
5718 note that @value{GDBN} still informs you that the program received a
5719 signal if @code{handle print} is set.
5721 @anchor{stepping into signal handlers}
5723 If you set @code{handle pass} for a signal, and your program sets up a
5724 handler for it, then issuing a stepping command, such as @code{step}
5725 or @code{stepi}, when your program is stopped due to the signal will
5726 step @emph{into} the signal handler (if the target supports that).
5728 Likewise, if you use the @code{queue-signal} command to queue a signal
5729 to be delivered to the current thread when execution of the thread
5730 resumes (@pxref{Signaling, ,Giving your Program a Signal}), then a
5731 stepping command will step into the signal handler.
5733 Here's an example, using @code{stepi} to step to the first instruction
5734 of @code{SIGUSR1}'s handler:
5737 (@value{GDBP}) handle SIGUSR1
5738 Signal Stop Print Pass to program Description
5739 SIGUSR1 Yes Yes Yes User defined signal 1
5743 Program received signal SIGUSR1, User defined signal 1.
5744 main () sigusr1.c:28
5747 sigusr1_handler () at sigusr1.c:9
5751 The same, but using @code{queue-signal} instead of waiting for the
5752 program to receive the signal first:
5757 (@value{GDBP}) queue-signal SIGUSR1
5759 sigusr1_handler () at sigusr1.c:9
5764 @cindex extra signal information
5765 @anchor{extra signal information}
5767 On some targets, @value{GDBN} can inspect extra signal information
5768 associated with the intercepted signal, before it is actually
5769 delivered to the program being debugged. This information is exported
5770 by the convenience variable @code{$_siginfo}, and consists of data
5771 that is passed by the kernel to the signal handler at the time of the
5772 receipt of a signal. The data type of the information itself is
5773 target dependent. You can see the data type using the @code{ptype
5774 $_siginfo} command. On Unix systems, it typically corresponds to the
5775 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5778 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5779 referenced address that raised a segmentation fault.
5783 (@value{GDBP}) continue
5784 Program received signal SIGSEGV, Segmentation fault.
5785 0x0000000000400766 in main ()
5787 (@value{GDBP}) ptype $_siginfo
5794 struct @{...@} _kill;
5795 struct @{...@} _timer;
5797 struct @{...@} _sigchld;
5798 struct @{...@} _sigfault;
5799 struct @{...@} _sigpoll;
5802 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5806 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5807 $1 = (void *) 0x7ffff7ff7000
5811 Depending on target support, @code{$_siginfo} may also be writable.
5814 @section Stopping and Starting Multi-thread Programs
5816 @cindex stopped threads
5817 @cindex threads, stopped
5819 @cindex continuing threads
5820 @cindex threads, continuing
5822 @value{GDBN} supports debugging programs with multiple threads
5823 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5824 are two modes of controlling execution of your program within the
5825 debugger. In the default mode, referred to as @dfn{all-stop mode},
5826 when any thread in your program stops (for example, at a breakpoint
5827 or while being stepped), all other threads in the program are also stopped by
5828 @value{GDBN}. On some targets, @value{GDBN} also supports
5829 @dfn{non-stop mode}, in which other threads can continue to run freely while
5830 you examine the stopped thread in the debugger.
5833 * All-Stop Mode:: All threads stop when GDB takes control
5834 * Non-Stop Mode:: Other threads continue to execute
5835 * Background Execution:: Running your program asynchronously
5836 * Thread-Specific Breakpoints:: Controlling breakpoints
5837 * Interrupted System Calls:: GDB may interfere with system calls
5838 * Observer Mode:: GDB does not alter program behavior
5842 @subsection All-Stop Mode
5844 @cindex all-stop mode
5846 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5847 @emph{all} threads of execution stop, not just the current thread. This
5848 allows you to examine the overall state of the program, including
5849 switching between threads, without worrying that things may change
5852 Conversely, whenever you restart the program, @emph{all} threads start
5853 executing. @emph{This is true even when single-stepping} with commands
5854 like @code{step} or @code{next}.
5856 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5857 Since thread scheduling is up to your debugging target's operating
5858 system (not controlled by @value{GDBN}), other threads may
5859 execute more than one statement while the current thread completes a
5860 single step. Moreover, in general other threads stop in the middle of a
5861 statement, rather than at a clean statement boundary, when the program
5864 You might even find your program stopped in another thread after
5865 continuing or even single-stepping. This happens whenever some other
5866 thread runs into a breakpoint, a signal, or an exception before the
5867 first thread completes whatever you requested.
5869 @cindex automatic thread selection
5870 @cindex switching threads automatically
5871 @cindex threads, automatic switching
5872 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5873 signal, it automatically selects the thread where that breakpoint or
5874 signal happened. @value{GDBN} alerts you to the context switch with a
5875 message such as @samp{[Switching to Thread @var{n}]} to identify the
5878 On some OSes, you can modify @value{GDBN}'s default behavior by
5879 locking the OS scheduler to allow only a single thread to run.
5882 @item set scheduler-locking @var{mode}
5883 @cindex scheduler locking mode
5884 @cindex lock scheduler
5885 Set the scheduler locking mode. It applies to normal execution,
5886 record mode, and replay mode. If it is @code{off}, then there is no
5887 locking and any thread may run at any time. If @code{on}, then only
5888 the current thread may run when the inferior is resumed. The
5889 @code{step} mode optimizes for single-stepping; it prevents other
5890 threads from preempting the current thread while you are stepping, so
5891 that the focus of debugging does not change unexpectedly. Other
5892 threads never get a chance to run when you step, and they are
5893 completely free to run when you use commands like @samp{continue},
5894 @samp{until}, or @samp{finish}. However, unless another thread hits a
5895 breakpoint during its timeslice, @value{GDBN} does not change the
5896 current thread away from the thread that you are debugging. The
5897 @code{replay} mode behaves like @code{off} in record mode and like
5898 @code{on} in replay mode.
5900 @item show scheduler-locking
5901 Display the current scheduler locking mode.
5904 @cindex resume threads of multiple processes simultaneously
5905 By default, when you issue one of the execution commands such as
5906 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5907 threads of the current inferior to run. For example, if @value{GDBN}
5908 is attached to two inferiors, each with two threads, the
5909 @code{continue} command resumes only the two threads of the current
5910 inferior. This is useful, for example, when you debug a program that
5911 forks and you want to hold the parent stopped (so that, for instance,
5912 it doesn't run to exit), while you debug the child. In other
5913 situations, you may not be interested in inspecting the current state
5914 of any of the processes @value{GDBN} is attached to, and you may want
5915 to resume them all until some breakpoint is hit. In the latter case,
5916 you can instruct @value{GDBN} to allow all threads of all the
5917 inferiors to run with the @w{@code{set schedule-multiple}} command.
5920 @kindex set schedule-multiple
5921 @item set schedule-multiple
5922 Set the mode for allowing threads of multiple processes to be resumed
5923 when an execution command is issued. When @code{on}, all threads of
5924 all processes are allowed to run. When @code{off}, only the threads
5925 of the current process are resumed. The default is @code{off}. The
5926 @code{scheduler-locking} mode takes precedence when set to @code{on},
5927 or while you are stepping and set to @code{step}.
5929 @item show schedule-multiple
5930 Display the current mode for resuming the execution of threads of
5935 @subsection Non-Stop Mode
5937 @cindex non-stop mode
5939 @c This section is really only a place-holder, and needs to be expanded
5940 @c with more details.
5942 For some multi-threaded targets, @value{GDBN} supports an optional
5943 mode of operation in which you can examine stopped program threads in
5944 the debugger while other threads continue to execute freely. This
5945 minimizes intrusion when debugging live systems, such as programs
5946 where some threads have real-time constraints or must continue to
5947 respond to external events. This is referred to as @dfn{non-stop} mode.
5949 In non-stop mode, when a thread stops to report a debugging event,
5950 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5951 threads as well, in contrast to the all-stop mode behavior. Additionally,
5952 execution commands such as @code{continue} and @code{step} apply by default
5953 only to the current thread in non-stop mode, rather than all threads as
5954 in all-stop mode. This allows you to control threads explicitly in
5955 ways that are not possible in all-stop mode --- for example, stepping
5956 one thread while allowing others to run freely, stepping
5957 one thread while holding all others stopped, or stepping several threads
5958 independently and simultaneously.
5960 To enter non-stop mode, use this sequence of commands before you run
5961 or attach to your program:
5964 # If using the CLI, pagination breaks non-stop.
5967 # Finally, turn it on!
5971 You can use these commands to manipulate the non-stop mode setting:
5974 @kindex set non-stop
5975 @item set non-stop on
5976 Enable selection of non-stop mode.
5977 @item set non-stop off
5978 Disable selection of non-stop mode.
5979 @kindex show non-stop
5981 Show the current non-stop enablement setting.
5984 Note these commands only reflect whether non-stop mode is enabled,
5985 not whether the currently-executing program is being run in non-stop mode.
5986 In particular, the @code{set non-stop} preference is only consulted when
5987 @value{GDBN} starts or connects to the target program, and it is generally
5988 not possible to switch modes once debugging has started. Furthermore,
5989 since not all targets support non-stop mode, even when you have enabled
5990 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5993 In non-stop mode, all execution commands apply only to the current thread
5994 by default. That is, @code{continue} only continues one thread.
5995 To continue all threads, issue @code{continue -a} or @code{c -a}.
5997 You can use @value{GDBN}'s background execution commands
5998 (@pxref{Background Execution}) to run some threads in the background
5999 while you continue to examine or step others from @value{GDBN}.
6000 The MI execution commands (@pxref{GDB/MI Program Execution}) are
6001 always executed asynchronously in non-stop mode.
6003 Suspending execution is done with the @code{interrupt} command when
6004 running in the background, or @kbd{Ctrl-c} during foreground execution.
6005 In all-stop mode, this stops the whole process;
6006 but in non-stop mode the interrupt applies only to the current thread.
6007 To stop the whole program, use @code{interrupt -a}.
6009 Other execution commands do not currently support the @code{-a} option.
6011 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
6012 that thread current, as it does in all-stop mode. This is because the
6013 thread stop notifications are asynchronous with respect to @value{GDBN}'s
6014 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
6015 changed to a different thread just as you entered a command to operate on the
6016 previously current thread.
6018 @node Background Execution
6019 @subsection Background Execution
6021 @cindex foreground execution
6022 @cindex background execution
6023 @cindex asynchronous execution
6024 @cindex execution, foreground, background and asynchronous
6026 @value{GDBN}'s execution commands have two variants: the normal
6027 foreground (synchronous) behavior, and a background
6028 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
6029 the program to report that some thread has stopped before prompting for
6030 another command. In background execution, @value{GDBN} immediately gives
6031 a command prompt so that you can issue other commands while your program runs.
6033 If the target doesn't support async mode, @value{GDBN} issues an error
6034 message if you attempt to use the background execution commands.
6036 To specify background execution, add a @code{&} to the command. For example,
6037 the background form of the @code{continue} command is @code{continue&}, or
6038 just @code{c&}. The execution commands that accept background execution
6044 @xref{Starting, , Starting your Program}.
6048 @xref{Attach, , Debugging an Already-running Process}.
6052 @xref{Continuing and Stepping, step}.
6056 @xref{Continuing and Stepping, stepi}.
6060 @xref{Continuing and Stepping, next}.
6064 @xref{Continuing and Stepping, nexti}.
6068 @xref{Continuing and Stepping, continue}.
6072 @xref{Continuing and Stepping, finish}.
6076 @xref{Continuing and Stepping, until}.
6080 Background execution is especially useful in conjunction with non-stop
6081 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
6082 However, you can also use these commands in the normal all-stop mode with
6083 the restriction that you cannot issue another execution command until the
6084 previous one finishes. Examples of commands that are valid in all-stop
6085 mode while the program is running include @code{help} and @code{info break}.
6087 You can interrupt your program while it is running in the background by
6088 using the @code{interrupt} command.
6095 Suspend execution of the running program. In all-stop mode,
6096 @code{interrupt} stops the whole process, but in non-stop mode, it stops
6097 only the current thread. To stop the whole program in non-stop mode,
6098 use @code{interrupt -a}.
6101 @node Thread-Specific Breakpoints
6102 @subsection Thread-Specific Breakpoints
6104 When your program has multiple threads (@pxref{Threads,, Debugging
6105 Programs with Multiple Threads}), you can choose whether to set
6106 breakpoints on all threads, or on a particular thread.
6109 @cindex breakpoints and threads
6110 @cindex thread breakpoints
6111 @kindex break @dots{} thread @var{thread-id}
6112 @item break @var{location} thread @var{thread-id}
6113 @itemx break @var{location} thread @var{thread-id} if @dots{}
6114 @var{location} specifies source lines; there are several ways of
6115 writing them (@pxref{Specify Location}), but the effect is always to
6116 specify some source line.
6118 Use the qualifier @samp{thread @var{thread-id}} with a breakpoint command
6119 to specify that you only want @value{GDBN} to stop the program when a
6120 particular thread reaches this breakpoint. The @var{thread-id} specifier
6121 is one of the thread identifiers assigned by @value{GDBN}, shown
6122 in the first column of the @samp{info threads} display.
6124 If you do not specify @samp{thread @var{thread-id}} when you set a
6125 breakpoint, the breakpoint applies to @emph{all} threads of your
6128 You can use the @code{thread} qualifier on conditional breakpoints as
6129 well; in this case, place @samp{thread @var{thread-id}} before or
6130 after the breakpoint condition, like this:
6133 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
6138 Thread-specific breakpoints are automatically deleted when
6139 @value{GDBN} detects the corresponding thread is no longer in the
6140 thread list. For example:
6144 Thread-specific breakpoint 3 deleted - thread 28 no longer in the thread list.
6147 There are several ways for a thread to disappear, such as a regular
6148 thread exit, but also when you detach from the process with the
6149 @code{detach} command (@pxref{Attach, ,Debugging an Already-running
6150 Process}), or if @value{GDBN} loses the remote connection
6151 (@pxref{Remote Debugging}), etc. Note that with some targets,
6152 @value{GDBN} is only able to detect a thread has exited when the user
6153 explictly asks for the thread list with the @code{info threads}
6156 @node Interrupted System Calls
6157 @subsection Interrupted System Calls
6159 @cindex thread breakpoints and system calls
6160 @cindex system calls and thread breakpoints
6161 @cindex premature return from system calls
6162 There is an unfortunate side effect when using @value{GDBN} to debug
6163 multi-threaded programs. If one thread stops for a
6164 breakpoint, or for some other reason, and another thread is blocked in a
6165 system call, then the system call may return prematurely. This is a
6166 consequence of the interaction between multiple threads and the signals
6167 that @value{GDBN} uses to implement breakpoints and other events that
6170 To handle this problem, your program should check the return value of
6171 each system call and react appropriately. This is good programming
6174 For example, do not write code like this:
6180 The call to @code{sleep} will return early if a different thread stops
6181 at a breakpoint or for some other reason.
6183 Instead, write this:
6188 unslept = sleep (unslept);
6191 A system call is allowed to return early, so the system is still
6192 conforming to its specification. But @value{GDBN} does cause your
6193 multi-threaded program to behave differently than it would without
6196 Also, @value{GDBN} uses internal breakpoints in the thread library to
6197 monitor certain events such as thread creation and thread destruction.
6198 When such an event happens, a system call in another thread may return
6199 prematurely, even though your program does not appear to stop.
6202 @subsection Observer Mode
6204 If you want to build on non-stop mode and observe program behavior
6205 without any chance of disruption by @value{GDBN}, you can set
6206 variables to disable all of the debugger's attempts to modify state,
6207 whether by writing memory, inserting breakpoints, etc. These operate
6208 at a low level, intercepting operations from all commands.
6210 When all of these are set to @code{off}, then @value{GDBN} is said to
6211 be @dfn{observer mode}. As a convenience, the variable
6212 @code{observer} can be set to disable these, plus enable non-stop
6215 Note that @value{GDBN} will not prevent you from making nonsensical
6216 combinations of these settings. For instance, if you have enabled
6217 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
6218 then breakpoints that work by writing trap instructions into the code
6219 stream will still not be able to be placed.
6224 @item set observer on
6225 @itemx set observer off
6226 When set to @code{on}, this disables all the permission variables
6227 below (except for @code{insert-fast-tracepoints}), plus enables
6228 non-stop debugging. Setting this to @code{off} switches back to
6229 normal debugging, though remaining in non-stop mode.
6232 Show whether observer mode is on or off.
6234 @kindex may-write-registers
6235 @item set may-write-registers on
6236 @itemx set may-write-registers off
6237 This controls whether @value{GDBN} will attempt to alter the values of
6238 registers, such as with assignment expressions in @code{print}, or the
6239 @code{jump} command. It defaults to @code{on}.
6241 @item show may-write-registers
6242 Show the current permission to write registers.
6244 @kindex may-write-memory
6245 @item set may-write-memory on
6246 @itemx set may-write-memory off
6247 This controls whether @value{GDBN} will attempt to alter the contents
6248 of memory, such as with assignment expressions in @code{print}. It
6249 defaults to @code{on}.
6251 @item show may-write-memory
6252 Show the current permission to write memory.
6254 @kindex may-insert-breakpoints
6255 @item set may-insert-breakpoints on
6256 @itemx set may-insert-breakpoints off
6257 This controls whether @value{GDBN} will attempt to insert breakpoints.
6258 This affects all breakpoints, including internal breakpoints defined
6259 by @value{GDBN}. It defaults to @code{on}.
6261 @item show may-insert-breakpoints
6262 Show the current permission to insert breakpoints.
6264 @kindex may-insert-tracepoints
6265 @item set may-insert-tracepoints on
6266 @itemx set may-insert-tracepoints off
6267 This controls whether @value{GDBN} will attempt to insert (regular)
6268 tracepoints at the beginning of a tracing experiment. It affects only
6269 non-fast tracepoints, fast tracepoints being under the control of
6270 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
6272 @item show may-insert-tracepoints
6273 Show the current permission to insert tracepoints.
6275 @kindex may-insert-fast-tracepoints
6276 @item set may-insert-fast-tracepoints on
6277 @itemx set may-insert-fast-tracepoints off
6278 This controls whether @value{GDBN} will attempt to insert fast
6279 tracepoints at the beginning of a tracing experiment. It affects only
6280 fast tracepoints, regular (non-fast) tracepoints being under the
6281 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
6283 @item show may-insert-fast-tracepoints
6284 Show the current permission to insert fast tracepoints.
6286 @kindex may-interrupt
6287 @item set may-interrupt on
6288 @itemx set may-interrupt off
6289 This controls whether @value{GDBN} will attempt to interrupt or stop
6290 program execution. When this variable is @code{off}, the
6291 @code{interrupt} command will have no effect, nor will
6292 @kbd{Ctrl-c}. It defaults to @code{on}.
6294 @item show may-interrupt
6295 Show the current permission to interrupt or stop the program.
6299 @node Reverse Execution
6300 @chapter Running programs backward
6301 @cindex reverse execution
6302 @cindex running programs backward
6304 When you are debugging a program, it is not unusual to realize that
6305 you have gone too far, and some event of interest has already happened.
6306 If the target environment supports it, @value{GDBN} can allow you to
6307 ``rewind'' the program by running it backward.
6309 A target environment that supports reverse execution should be able
6310 to ``undo'' the changes in machine state that have taken place as the
6311 program was executing normally. Variables, registers etc.@: should
6312 revert to their previous values. Obviously this requires a great
6313 deal of sophistication on the part of the target environment; not
6314 all target environments can support reverse execution.
6316 When a program is executed in reverse, the instructions that
6317 have most recently been executed are ``un-executed'', in reverse
6318 order. The program counter runs backward, following the previous
6319 thread of execution in reverse. As each instruction is ``un-executed'',
6320 the values of memory and/or registers that were changed by that
6321 instruction are reverted to their previous states. After executing
6322 a piece of source code in reverse, all side effects of that code
6323 should be ``undone'', and all variables should be returned to their
6324 prior values@footnote{
6325 Note that some side effects are easier to undo than others. For instance,
6326 memory and registers are relatively easy, but device I/O is hard. Some
6327 targets may be able undo things like device I/O, and some may not.
6329 The contract between @value{GDBN} and the reverse executing target
6330 requires only that the target do something reasonable when
6331 @value{GDBN} tells it to execute backwards, and then report the
6332 results back to @value{GDBN}. Whatever the target reports back to
6333 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6334 assumes that the memory and registers that the target reports are in a
6335 consistant state, but @value{GDBN} accepts whatever it is given.
6338 If you are debugging in a target environment that supports
6339 reverse execution, @value{GDBN} provides the following commands.
6342 @kindex reverse-continue
6343 @kindex rc @r{(@code{reverse-continue})}
6344 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6345 @itemx rc @r{[}@var{ignore-count}@r{]}
6346 Beginning at the point where your program last stopped, start executing
6347 in reverse. Reverse execution will stop for breakpoints and synchronous
6348 exceptions (signals), just like normal execution. Behavior of
6349 asynchronous signals depends on the target environment.
6351 @kindex reverse-step
6352 @kindex rs @r{(@code{step})}
6353 @item reverse-step @r{[}@var{count}@r{]}
6354 Run the program backward until control reaches the start of a
6355 different source line; then stop it, and return control to @value{GDBN}.
6357 Like the @code{step} command, @code{reverse-step} will only stop
6358 at the beginning of a source line. It ``un-executes'' the previously
6359 executed source line. If the previous source line included calls to
6360 debuggable functions, @code{reverse-step} will step (backward) into
6361 the called function, stopping at the beginning of the @emph{last}
6362 statement in the called function (typically a return statement).
6364 Also, as with the @code{step} command, if non-debuggable functions are
6365 called, @code{reverse-step} will run thru them backward without stopping.
6367 @kindex reverse-stepi
6368 @kindex rsi @r{(@code{reverse-stepi})}
6369 @item reverse-stepi @r{[}@var{count}@r{]}
6370 Reverse-execute one machine instruction. Note that the instruction
6371 to be reverse-executed is @emph{not} the one pointed to by the program
6372 counter, but the instruction executed prior to that one. For instance,
6373 if the last instruction was a jump, @code{reverse-stepi} will take you
6374 back from the destination of the jump to the jump instruction itself.
6376 @kindex reverse-next
6377 @kindex rn @r{(@code{reverse-next})}
6378 @item reverse-next @r{[}@var{count}@r{]}
6379 Run backward to the beginning of the previous line executed in
6380 the current (innermost) stack frame. If the line contains function
6381 calls, they will be ``un-executed'' without stopping. Starting from
6382 the first line of a function, @code{reverse-next} will take you back
6383 to the caller of that function, @emph{before} the function was called,
6384 just as the normal @code{next} command would take you from the last
6385 line of a function back to its return to its caller
6386 @footnote{Unless the code is too heavily optimized.}.
6388 @kindex reverse-nexti
6389 @kindex rni @r{(@code{reverse-nexti})}
6390 @item reverse-nexti @r{[}@var{count}@r{]}
6391 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6392 in reverse, except that called functions are ``un-executed'' atomically.
6393 That is, if the previously executed instruction was a return from
6394 another function, @code{reverse-nexti} will continue to execute
6395 in reverse until the call to that function (from the current stack
6398 @kindex reverse-finish
6399 @item reverse-finish
6400 Just as the @code{finish} command takes you to the point where the
6401 current function returns, @code{reverse-finish} takes you to the point
6402 where it was called. Instead of ending up at the end of the current
6403 function invocation, you end up at the beginning.
6405 @kindex set exec-direction
6406 @item set exec-direction
6407 Set the direction of target execution.
6408 @item set exec-direction reverse
6409 @cindex execute forward or backward in time
6410 @value{GDBN} will perform all execution commands in reverse, until the
6411 exec-direction mode is changed to ``forward''. Affected commands include
6412 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6413 command cannot be used in reverse mode.
6414 @item set exec-direction forward
6415 @value{GDBN} will perform all execution commands in the normal fashion.
6416 This is the default.
6420 @node Process Record and Replay
6421 @chapter Recording Inferior's Execution and Replaying It
6422 @cindex process record and replay
6423 @cindex recording inferior's execution and replaying it
6425 On some platforms, @value{GDBN} provides a special @dfn{process record
6426 and replay} target that can record a log of the process execution, and
6427 replay it later with both forward and reverse execution commands.
6430 When this target is in use, if the execution log includes the record
6431 for the next instruction, @value{GDBN} will debug in @dfn{replay
6432 mode}. In the replay mode, the inferior does not really execute code
6433 instructions. Instead, all the events that normally happen during
6434 code execution are taken from the execution log. While code is not
6435 really executed in replay mode, the values of registers (including the
6436 program counter register) and the memory of the inferior are still
6437 changed as they normally would. Their contents are taken from the
6441 If the record for the next instruction is not in the execution log,
6442 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6443 inferior executes normally, and @value{GDBN} records the execution log
6446 The process record and replay target supports reverse execution
6447 (@pxref{Reverse Execution}), even if the platform on which the
6448 inferior runs does not. However, the reverse execution is limited in
6449 this case by the range of the instructions recorded in the execution
6450 log. In other words, reverse execution on platforms that don't
6451 support it directly can only be done in the replay mode.
6453 When debugging in the reverse direction, @value{GDBN} will work in
6454 replay mode as long as the execution log includes the record for the
6455 previous instruction; otherwise, it will work in record mode, if the
6456 platform supports reverse execution, or stop if not.
6458 For architecture environments that support process record and replay,
6459 @value{GDBN} provides the following commands:
6462 @kindex target record
6463 @kindex target record-full
6464 @kindex target record-btrace
6467 @kindex record btrace
6468 @kindex record btrace bts
6469 @kindex record btrace pt
6475 @kindex rec btrace bts
6476 @kindex rec btrace pt
6479 @item record @var{method}
6480 This command starts the process record and replay target. The
6481 recording method can be specified as parameter. Without a parameter
6482 the command uses the @code{full} recording method. The following
6483 recording methods are available:
6487 Full record/replay recording using @value{GDBN}'s software record and
6488 replay implementation. This method allows replaying and reverse
6491 @item btrace @var{format}
6492 Hardware-supported instruction recording. This method does not record
6493 data. Further, the data is collected in a ring buffer so old data will
6494 be overwritten when the buffer is full. It allows limited reverse
6495 execution. Variables and registers are not available during reverse
6498 The recording format can be specified as parameter. Without a parameter
6499 the command chooses the recording format. The following recording
6500 formats are available:
6504 @cindex branch trace store
6505 Use the @dfn{Branch Trace Store} (@acronym{BTS}) recording format. In
6506 this format, the processor stores a from/to record for each executed
6507 branch in the btrace ring buffer.
6510 @cindex Intel Processor Trace
6511 Use the @dfn{Intel Processor Trace} recording format. In this
6512 format, the processor stores the execution trace in a compressed form
6513 that is afterwards decoded by @value{GDBN}.
6515 The trace can be recorded with very low overhead. The compressed
6516 trace format also allows small trace buffers to already contain a big
6517 number of instructions compared to @acronym{BTS}.
6519 Decoding the recorded execution trace, on the other hand, is more
6520 expensive than decoding @acronym{BTS} trace. This is mostly due to the
6521 increased number of instructions to process. You should increase the
6522 buffer-size with care.
6525 Not all recording formats may be available on all processors.
6528 The process record and replay target can only debug a process that is
6529 already running. Therefore, you need first to start the process with
6530 the @kbd{run} or @kbd{start} commands, and then start the recording
6531 with the @kbd{record @var{method}} command.
6533 @cindex displaced stepping, and process record and replay
6534 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6535 will be automatically disabled when process record and replay target
6536 is started. That's because the process record and replay target
6537 doesn't support displaced stepping.
6539 @cindex non-stop mode, and process record and replay
6540 @cindex asynchronous execution, and process record and replay
6541 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6542 the asynchronous execution mode (@pxref{Background Execution}), not
6543 all recording methods are available. The @code{full} recording method
6544 does not support these two modes.
6549 Stop the process record and replay target. When process record and
6550 replay target stops, the entire execution log will be deleted and the
6551 inferior will either be terminated, or will remain in its final state.
6553 When you stop the process record and replay target in record mode (at
6554 the end of the execution log), the inferior will be stopped at the
6555 next instruction that would have been recorded. In other words, if
6556 you record for a while and then stop recording, the inferior process
6557 will be left in the same state as if the recording never happened.
6559 On the other hand, if the process record and replay target is stopped
6560 while in replay mode (that is, not at the end of the execution log,
6561 but at some earlier point), the inferior process will become ``live''
6562 at that earlier state, and it will then be possible to continue the
6563 usual ``live'' debugging of the process from that state.
6565 When the inferior process exits, or @value{GDBN} detaches from it,
6566 process record and replay target will automatically stop itself.
6570 Go to a specific location in the execution log. There are several
6571 ways to specify the location to go to:
6574 @item record goto begin
6575 @itemx record goto start
6576 Go to the beginning of the execution log.
6578 @item record goto end
6579 Go to the end of the execution log.
6581 @item record goto @var{n}
6582 Go to instruction number @var{n} in the execution log.
6586 @item record save @var{filename}
6587 Save the execution log to a file @file{@var{filename}}.
6588 Default filename is @file{gdb_record.@var{process_id}}, where
6589 @var{process_id} is the process ID of the inferior.
6591 This command may not be available for all recording methods.
6593 @kindex record restore
6594 @item record restore @var{filename}
6595 Restore the execution log from a file @file{@var{filename}}.
6596 File must have been created with @code{record save}.
6598 @kindex set record full
6599 @item set record full insn-number-max @var{limit}
6600 @itemx set record full insn-number-max unlimited
6601 Set the limit of instructions to be recorded for the @code{full}
6602 recording method. Default value is 200000.
6604 If @var{limit} is a positive number, then @value{GDBN} will start
6605 deleting instructions from the log once the number of the record
6606 instructions becomes greater than @var{limit}. For every new recorded
6607 instruction, @value{GDBN} will delete the earliest recorded
6608 instruction to keep the number of recorded instructions at the limit.
6609 (Since deleting recorded instructions loses information, @value{GDBN}
6610 lets you control what happens when the limit is reached, by means of
6611 the @code{stop-at-limit} option, described below.)
6613 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6614 delete recorded instructions from the execution log. The number of
6615 recorded instructions is limited only by the available memory.
6617 @kindex show record full
6618 @item show record full insn-number-max
6619 Show the limit of instructions to be recorded with the @code{full}
6622 @item set record full stop-at-limit
6623 Control the behavior of the @code{full} recording method when the
6624 number of recorded instructions reaches the limit. If ON (the
6625 default), @value{GDBN} will stop when the limit is reached for the
6626 first time and ask you whether you want to stop the inferior or
6627 continue running it and recording the execution log. If you decide
6628 to continue recording, each new recorded instruction will cause the
6629 oldest one to be deleted.
6631 If this option is OFF, @value{GDBN} will automatically delete the
6632 oldest record to make room for each new one, without asking.
6634 @item show record full stop-at-limit
6635 Show the current setting of @code{stop-at-limit}.
6637 @item set record full memory-query
6638 Control the behavior when @value{GDBN} is unable to record memory
6639 changes caused by an instruction for the @code{full} recording method.
6640 If ON, @value{GDBN} will query whether to stop the inferior in that
6643 If this option is OFF (the default), @value{GDBN} will automatically
6644 ignore the effect of such instructions on memory. Later, when
6645 @value{GDBN} replays this execution log, it will mark the log of this
6646 instruction as not accessible, and it will not affect the replay
6649 @item show record full memory-query
6650 Show the current setting of @code{memory-query}.
6652 @kindex set record btrace
6653 The @code{btrace} record target does not trace data. As a
6654 convenience, when replaying, @value{GDBN} reads read-only memory off
6655 the live program directly, assuming that the addresses of the
6656 read-only areas don't change. This for example makes it possible to
6657 disassemble code while replaying, but not to print variables.
6658 In some cases, being able to inspect variables might be useful.
6659 You can use the following command for that:
6661 @item set record btrace replay-memory-access
6662 Control the behavior of the @code{btrace} recording method when
6663 accessing memory during replay. If @code{read-only} (the default),
6664 @value{GDBN} will only allow accesses to read-only memory.
6665 If @code{read-write}, @value{GDBN} will allow accesses to read-only
6666 and to read-write memory. Beware that the accessed memory corresponds
6667 to the live target and not necessarily to the current replay
6670 @kindex show record btrace
6671 @item show record btrace replay-memory-access
6672 Show the current setting of @code{replay-memory-access}.
6674 @kindex set record btrace bts
6675 @item set record btrace bts buffer-size @var{size}
6676 @itemx set record btrace bts buffer-size unlimited
6677 Set the requested ring buffer size for branch tracing in @acronym{BTS}
6678 format. Default is 64KB.
6680 If @var{size} is a positive number, then @value{GDBN} will try to
6681 allocate a buffer of at least @var{size} bytes for each new thread
6682 that uses the btrace recording method and the @acronym{BTS} format.
6683 The actually obtained buffer size may differ from the requested
6684 @var{size}. Use the @code{info record} command to see the actual
6685 buffer size for each thread that uses the btrace recording method and
6686 the @acronym{BTS} format.
6688 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6689 allocate a buffer of 4MB.
6691 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6692 also need longer to process the branch trace data before it can be used.
6694 @item show record btrace bts buffer-size @var{size}
6695 Show the current setting of the requested ring buffer size for branch
6696 tracing in @acronym{BTS} format.
6698 @kindex set record btrace pt
6699 @item set record btrace pt buffer-size @var{size}
6700 @itemx set record btrace pt buffer-size unlimited
6701 Set the requested ring buffer size for branch tracing in Intel
6702 Processor Trace format. Default is 16KB.
6704 If @var{size} is a positive number, then @value{GDBN} will try to
6705 allocate a buffer of at least @var{size} bytes for each new thread
6706 that uses the btrace recording method and the Intel Processor Trace
6707 format. The actually obtained buffer size may differ from the
6708 requested @var{size}. Use the @code{info record} command to see the
6709 actual buffer size for each thread.
6711 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will try to
6712 allocate a buffer of 4MB.
6714 Bigger buffers mean longer traces. On the other hand, @value{GDBN} will
6715 also need longer to process the branch trace data before it can be used.
6717 @item show record btrace pt buffer-size @var{size}
6718 Show the current setting of the requested ring buffer size for branch
6719 tracing in Intel Processor Trace format.
6723 Show various statistics about the recording depending on the recording
6728 For the @code{full} recording method, it shows the state of process
6729 record and its in-memory execution log buffer, including:
6733 Whether in record mode or replay mode.
6735 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6737 Highest recorded instruction number.
6739 Current instruction about to be replayed (if in replay mode).
6741 Number of instructions contained in the execution log.
6743 Maximum number of instructions that may be contained in the execution log.
6747 For the @code{btrace} recording method, it shows:
6753 Number of instructions that have been recorded.
6755 Number of blocks of sequential control-flow formed by the recorded
6758 Whether in record mode or replay mode.
6761 For the @code{bts} recording format, it also shows:
6764 Size of the perf ring buffer.
6767 For the @code{pt} recording format, it also shows:
6770 Size of the perf ring buffer.
6774 @kindex record delete
6777 When record target runs in replay mode (``in the past''), delete the
6778 subsequent execution log and begin to record a new execution log starting
6779 from the current address. This means you will abandon the previously
6780 recorded ``future'' and begin recording a new ``future''.
6782 @kindex record instruction-history
6783 @kindex rec instruction-history
6784 @item record instruction-history
6785 Disassembles instructions from the recorded execution log. By
6786 default, ten instructions are disassembled. This can be changed using
6787 the @code{set record instruction-history-size} command. Instructions
6788 are printed in execution order.
6790 It can also print mixed source+disassembly if you specify the the
6791 @code{/m} or @code{/s} modifier, and print the raw instructions in hex
6792 as well as in symbolic form by specifying the @code{/r} modifier.
6794 The current position marker is printed for the instruction at the
6795 current program counter value. This instruction can appear multiple
6796 times in the trace and the current position marker will be printed
6797 every time. To omit the current position marker, specify the
6800 To better align the printed instructions when the trace contains
6801 instructions from more than one function, the function name may be
6802 omitted by specifying the @code{/f} modifier.
6804 Speculatively executed instructions are prefixed with @samp{?}. This
6805 feature is not available for all recording formats.
6807 There are several ways to specify what part of the execution log to
6811 @item record instruction-history @var{insn}
6812 Disassembles ten instructions starting from instruction number
6815 @item record instruction-history @var{insn}, +/-@var{n}
6816 Disassembles @var{n} instructions around instruction number
6817 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6818 @var{n} instructions after instruction number @var{insn}. If
6819 @var{n} is preceded with @code{-}, disassembles @var{n}
6820 instructions before instruction number @var{insn}.
6822 @item record instruction-history
6823 Disassembles ten more instructions after the last disassembly.
6825 @item record instruction-history -
6826 Disassembles ten more instructions before the last disassembly.
6828 @item record instruction-history @var{begin}, @var{end}
6829 Disassembles instructions beginning with instruction number
6830 @var{begin} until instruction number @var{end}. The instruction
6831 number @var{end} is included.
6834 This command may not be available for all recording methods.
6837 @item set record instruction-history-size @var{size}
6838 @itemx set record instruction-history-size unlimited
6839 Define how many instructions to disassemble in the @code{record
6840 instruction-history} command. The default value is 10.
6841 A @var{size} of @code{unlimited} means unlimited instructions.
6844 @item show record instruction-history-size
6845 Show how many instructions to disassemble in the @code{record
6846 instruction-history} command.
6848 @kindex record function-call-history
6849 @kindex rec function-call-history
6850 @item record function-call-history
6851 Prints the execution history at function granularity. It prints one
6852 line for each sequence of instructions that belong to the same
6853 function giving the name of that function, the source lines
6854 for this instruction sequence (if the @code{/l} modifier is
6855 specified), and the instructions numbers that form the sequence (if
6856 the @code{/i} modifier is specified). The function names are indented
6857 to reflect the call stack depth if the @code{/c} modifier is
6858 specified. The @code{/l}, @code{/i}, and @code{/c} modifiers can be
6862 (@value{GDBP}) @b{list 1, 10}
6873 (@value{GDBP}) @b{record function-call-history /ilc}
6874 1 bar inst 1,4 at foo.c:6,8
6875 2 foo inst 5,10 at foo.c:2,3
6876 3 bar inst 11,13 at foo.c:9,10
6879 By default, ten lines are printed. This can be changed using the
6880 @code{set record function-call-history-size} command. Functions are
6881 printed in execution order. There are several ways to specify what
6885 @item record function-call-history @var{func}
6886 Prints ten functions starting from function number @var{func}.
6888 @item record function-call-history @var{func}, +/-@var{n}
6889 Prints @var{n} functions around function number @var{func}. If
6890 @var{n} is preceded with @code{+}, prints @var{n} functions after
6891 function number @var{func}. If @var{n} is preceded with @code{-},
6892 prints @var{n} functions before function number @var{func}.
6894 @item record function-call-history
6895 Prints ten more functions after the last ten-line print.
6897 @item record function-call-history -
6898 Prints ten more functions before the last ten-line print.
6900 @item record function-call-history @var{begin}, @var{end}
6901 Prints functions beginning with function number @var{begin} until
6902 function number @var{end}. The function number @var{end} is included.
6905 This command may not be available for all recording methods.
6907 @item set record function-call-history-size @var{size}
6908 @itemx set record function-call-history-size unlimited
6909 Define how many lines to print in the
6910 @code{record function-call-history} command. The default value is 10.
6911 A size of @code{unlimited} means unlimited lines.
6913 @item show record function-call-history-size
6914 Show how many lines to print in the
6915 @code{record function-call-history} command.
6920 @chapter Examining the Stack
6922 When your program has stopped, the first thing you need to know is where it
6923 stopped and how it got there.
6926 Each time your program performs a function call, information about the call
6928 That information includes the location of the call in your program,
6929 the arguments of the call,
6930 and the local variables of the function being called.
6931 The information is saved in a block of data called a @dfn{stack frame}.
6932 The stack frames are allocated in a region of memory called the @dfn{call
6935 When your program stops, the @value{GDBN} commands for examining the
6936 stack allow you to see all of this information.
6938 @cindex selected frame
6939 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6940 @value{GDBN} commands refer implicitly to the selected frame. In
6941 particular, whenever you ask @value{GDBN} for the value of a variable in
6942 your program, the value is found in the selected frame. There are
6943 special @value{GDBN} commands to select whichever frame you are
6944 interested in. @xref{Selection, ,Selecting a Frame}.
6946 When your program stops, @value{GDBN} automatically selects the
6947 currently executing frame and describes it briefly, similar to the
6948 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6951 * Frames:: Stack frames
6952 * Backtrace:: Backtraces
6953 * Selection:: Selecting a frame
6954 * Frame Info:: Information on a frame
6955 * Frame Filter Management:: Managing frame filters
6960 @section Stack Frames
6962 @cindex frame, definition
6964 The call stack is divided up into contiguous pieces called @dfn{stack
6965 frames}, or @dfn{frames} for short; each frame is the data associated
6966 with one call to one function. The frame contains the arguments given
6967 to the function, the function's local variables, and the address at
6968 which the function is executing.
6970 @cindex initial frame
6971 @cindex outermost frame
6972 @cindex innermost frame
6973 When your program is started, the stack has only one frame, that of the
6974 function @code{main}. This is called the @dfn{initial} frame or the
6975 @dfn{outermost} frame. Each time a function is called, a new frame is
6976 made. Each time a function returns, the frame for that function invocation
6977 is eliminated. If a function is recursive, there can be many frames for
6978 the same function. The frame for the function in which execution is
6979 actually occurring is called the @dfn{innermost} frame. This is the most
6980 recently created of all the stack frames that still exist.
6982 @cindex frame pointer
6983 Inside your program, stack frames are identified by their addresses. A
6984 stack frame consists of many bytes, each of which has its own address; each
6985 kind of computer has a convention for choosing one byte whose
6986 address serves as the address of the frame. Usually this address is kept
6987 in a register called the @dfn{frame pointer register}
6988 (@pxref{Registers, $fp}) while execution is going on in that frame.
6990 @cindex frame number
6991 @value{GDBN} assigns numbers to all existing stack frames, starting with
6992 zero for the innermost frame, one for the frame that called it,
6993 and so on upward. These numbers do not really exist in your program;
6994 they are assigned by @value{GDBN} to give you a way of designating stack
6995 frames in @value{GDBN} commands.
6997 @c The -fomit-frame-pointer below perennially causes hbox overflow
6998 @c underflow problems.
6999 @cindex frameless execution
7000 Some compilers provide a way to compile functions so that they operate
7001 without stack frames. (For example, the @value{NGCC} option
7003 @samp{-fomit-frame-pointer}
7005 generates functions without a frame.)
7006 This is occasionally done with heavily used library functions to save
7007 the frame setup time. @value{GDBN} has limited facilities for dealing
7008 with these function invocations. If the innermost function invocation
7009 has no stack frame, @value{GDBN} nevertheless regards it as though
7010 it had a separate frame, which is numbered zero as usual, allowing
7011 correct tracing of the function call chain. However, @value{GDBN} has
7012 no provision for frameless functions elsewhere in the stack.
7018 @cindex call stack traces
7019 A backtrace is a summary of how your program got where it is. It shows one
7020 line per frame, for many frames, starting with the currently executing
7021 frame (frame zero), followed by its caller (frame one), and on up the
7024 @anchor{backtrace-command}
7027 @kindex bt @r{(@code{backtrace})}
7030 Print a backtrace of the entire stack: one line per frame for all
7031 frames in the stack.
7033 You can stop the backtrace at any time by typing the system interrupt
7034 character, normally @kbd{Ctrl-c}.
7036 @item backtrace @var{n}
7038 Similar, but print only the innermost @var{n} frames.
7040 @item backtrace -@var{n}
7042 Similar, but print only the outermost @var{n} frames.
7044 @item backtrace full
7046 @itemx bt full @var{n}
7047 @itemx bt full -@var{n}
7048 Print the values of the local variables also. As described above,
7049 @var{n} specifies the number of frames to print.
7051 @item backtrace no-filters
7052 @itemx bt no-filters
7053 @itemx bt no-filters @var{n}
7054 @itemx bt no-filters -@var{n}
7055 @itemx bt no-filters full
7056 @itemx bt no-filters full @var{n}
7057 @itemx bt no-filters full -@var{n}
7058 Do not run Python frame filters on this backtrace. @xref{Frame
7059 Filter API}, for more information. Additionally use @ref{disable
7060 frame-filter all} to turn off all frame filters. This is only
7061 relevant when @value{GDBN} has been configured with @code{Python}
7067 The names @code{where} and @code{info stack} (abbreviated @code{info s})
7068 are additional aliases for @code{backtrace}.
7070 @cindex multiple threads, backtrace
7071 In a multi-threaded program, @value{GDBN} by default shows the
7072 backtrace only for the current thread. To display the backtrace for
7073 several or all of the threads, use the command @code{thread apply}
7074 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
7075 apply all backtrace}, @value{GDBN} will display the backtrace for all
7076 the threads; this is handy when you debug a core dump of a
7077 multi-threaded program.
7079 Each line in the backtrace shows the frame number and the function name.
7080 The program counter value is also shown---unless you use @code{set
7081 print address off}. The backtrace also shows the source file name and
7082 line number, as well as the arguments to the function. The program
7083 counter value is omitted if it is at the beginning of the code for that
7086 Here is an example of a backtrace. It was made with the command
7087 @samp{bt 3}, so it shows the innermost three frames.
7091 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7093 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
7094 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
7096 (More stack frames follow...)
7101 The display for frame zero does not begin with a program counter
7102 value, indicating that your program has stopped at the beginning of the
7103 code for line @code{993} of @code{builtin.c}.
7106 The value of parameter @code{data} in frame 1 has been replaced by
7107 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
7108 only if it is a scalar (integer, pointer, enumeration, etc). See command
7109 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
7110 on how to configure the way function parameter values are printed.
7112 @cindex optimized out, in backtrace
7113 @cindex function call arguments, optimized out
7114 If your program was compiled with optimizations, some compilers will
7115 optimize away arguments passed to functions if those arguments are
7116 never used after the call. Such optimizations generate code that
7117 passes arguments through registers, but doesn't store those arguments
7118 in the stack frame. @value{GDBN} has no way of displaying such
7119 arguments in stack frames other than the innermost one. Here's what
7120 such a backtrace might look like:
7124 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
7126 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
7127 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
7129 (More stack frames follow...)
7134 The values of arguments that were not saved in their stack frames are
7135 shown as @samp{<optimized out>}.
7137 If you need to display the values of such optimized-out arguments,
7138 either deduce that from other variables whose values depend on the one
7139 you are interested in, or recompile without optimizations.
7141 @cindex backtrace beyond @code{main} function
7142 @cindex program entry point
7143 @cindex startup code, and backtrace
7144 Most programs have a standard user entry point---a place where system
7145 libraries and startup code transition into user code. For C this is
7146 @code{main}@footnote{
7147 Note that embedded programs (the so-called ``free-standing''
7148 environment) are not required to have a @code{main} function as the
7149 entry point. They could even have multiple entry points.}.
7150 When @value{GDBN} finds the entry function in a backtrace
7151 it will terminate the backtrace, to avoid tracing into highly
7152 system-specific (and generally uninteresting) code.
7154 If you need to examine the startup code, or limit the number of levels
7155 in a backtrace, you can change this behavior:
7158 @item set backtrace past-main
7159 @itemx set backtrace past-main on
7160 @kindex set backtrace
7161 Backtraces will continue past the user entry point.
7163 @item set backtrace past-main off
7164 Backtraces will stop when they encounter the user entry point. This is the
7167 @item show backtrace past-main
7168 @kindex show backtrace
7169 Display the current user entry point backtrace policy.
7171 @item set backtrace past-entry
7172 @itemx set backtrace past-entry on
7173 Backtraces will continue past the internal entry point of an application.
7174 This entry point is encoded by the linker when the application is built,
7175 and is likely before the user entry point @code{main} (or equivalent) is called.
7177 @item set backtrace past-entry off
7178 Backtraces will stop when they encounter the internal entry point of an
7179 application. This is the default.
7181 @item show backtrace past-entry
7182 Display the current internal entry point backtrace policy.
7184 @item set backtrace limit @var{n}
7185 @itemx set backtrace limit 0
7186 @itemx set backtrace limit unlimited
7187 @cindex backtrace limit
7188 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
7189 or zero means unlimited levels.
7191 @item show backtrace limit
7192 Display the current limit on backtrace levels.
7195 You can control how file names are displayed.
7198 @item set filename-display
7199 @itemx set filename-display relative
7200 @cindex filename-display
7201 Display file names relative to the compilation directory. This is the default.
7203 @item set filename-display basename
7204 Display only basename of a filename.
7206 @item set filename-display absolute
7207 Display an absolute filename.
7209 @item show filename-display
7210 Show the current way to display filenames.
7214 @section Selecting a Frame
7216 Most commands for examining the stack and other data in your program work on
7217 whichever stack frame is selected at the moment. Here are the commands for
7218 selecting a stack frame; all of them finish by printing a brief description
7219 of the stack frame just selected.
7222 @kindex frame@r{, selecting}
7223 @kindex f @r{(@code{frame})}
7226 Select frame number @var{n}. Recall that frame zero is the innermost
7227 (currently executing) frame, frame one is the frame that called the
7228 innermost one, and so on. The highest-numbered frame is the one for
7231 @item frame @var{stack-addr} [ @var{pc-addr} ]
7232 @itemx f @var{stack-addr} [ @var{pc-addr} ]
7233 Select the frame at address @var{stack-addr}. This is useful mainly if the
7234 chaining of stack frames has been damaged by a bug, making it
7235 impossible for @value{GDBN} to assign numbers properly to all frames. In
7236 addition, this can be useful when your program has multiple stacks and
7237 switches between them. The optional @var{pc-addr} can also be given to
7238 specify the value of PC for the stack frame.
7242 Move @var{n} frames up the stack; @var{n} defaults to 1. For positive
7243 numbers @var{n}, this advances toward the outermost frame, to higher
7244 frame numbers, to frames that have existed longer.
7247 @kindex do @r{(@code{down})}
7249 Move @var{n} frames down the stack; @var{n} defaults to 1. For
7250 positive numbers @var{n}, this advances toward the innermost frame, to
7251 lower frame numbers, to frames that were created more recently.
7252 You may abbreviate @code{down} as @code{do}.
7255 All of these commands end by printing two lines of output describing the
7256 frame. The first line shows the frame number, the function name, the
7257 arguments, and the source file and line number of execution in that
7258 frame. The second line shows the text of that source line.
7266 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7268 10 read_input_file (argv[i]);
7272 After such a printout, the @code{list} command with no arguments
7273 prints ten lines centered on the point of execution in the frame.
7274 You can also edit the program at the point of execution with your favorite
7275 editing program by typing @code{edit}.
7276 @xref{List, ,Printing Source Lines},
7280 @kindex select-frame
7282 The @code{select-frame} command is a variant of @code{frame} that does
7283 not display the new frame after selecting it. This command is
7284 intended primarily for use in @value{GDBN} command scripts, where the
7285 output might be unnecessary and distracting.
7287 @kindex down-silently
7289 @item up-silently @var{n}
7290 @itemx down-silently @var{n}
7291 These two commands are variants of @code{up} and @code{down},
7292 respectively; they differ in that they do their work silently, without
7293 causing display of the new frame. They are intended primarily for use
7294 in @value{GDBN} command scripts, where the output might be unnecessary and
7299 @section Information About a Frame
7301 There are several other commands to print information about the selected
7307 When used without any argument, this command does not change which
7308 frame is selected, but prints a brief description of the currently
7309 selected stack frame. It can be abbreviated @code{f}. With an
7310 argument, this command is used to select a stack frame.
7311 @xref{Selection, ,Selecting a Frame}.
7314 @kindex info f @r{(@code{info frame})}
7317 This command prints a verbose description of the selected stack frame,
7322 the address of the frame
7324 the address of the next frame down (called by this frame)
7326 the address of the next frame up (caller of this frame)
7328 the language in which the source code corresponding to this frame is written
7330 the address of the frame's arguments
7332 the address of the frame's local variables
7334 the program counter saved in it (the address of execution in the caller frame)
7336 which registers were saved in the frame
7339 @noindent The verbose description is useful when
7340 something has gone wrong that has made the stack format fail to fit
7341 the usual conventions.
7343 @item info frame @var{addr}
7344 @itemx info f @var{addr}
7345 Print a verbose description of the frame at address @var{addr}, without
7346 selecting that frame. The selected frame remains unchanged by this
7347 command. This requires the same kind of address (more than one for some
7348 architectures) that you specify in the @code{frame} command.
7349 @xref{Selection, ,Selecting a Frame}.
7353 Print the arguments of the selected frame, each on a separate line.
7357 Print the local variables of the selected frame, each on a separate
7358 line. These are all variables (declared either static or automatic)
7359 accessible at the point of execution of the selected frame.
7363 @node Frame Filter Management
7364 @section Management of Frame Filters.
7365 @cindex managing frame filters
7367 Frame filters are Python based utilities to manage and decorate the
7368 output of frames. @xref{Frame Filter API}, for further information.
7370 Managing frame filters is performed by several commands available
7371 within @value{GDBN}, detailed here.
7374 @kindex info frame-filter
7375 @item info frame-filter
7376 Print a list of installed frame filters from all dictionaries, showing
7377 their name, priority and enabled status.
7379 @kindex disable frame-filter
7380 @anchor{disable frame-filter all}
7381 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
7382 Disable a frame filter in the dictionary matching
7383 @var{filter-dictionary} and @var{filter-name}. The
7384 @var{filter-dictionary} may be @code{all}, @code{global},
7385 @code{progspace}, or the name of the object file where the frame filter
7386 dictionary resides. When @code{all} is specified, all frame filters
7387 across all dictionaries are disabled. The @var{filter-name} is the name
7388 of the frame filter and is used when @code{all} is not the option for
7389 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
7390 may be enabled again later.
7392 @kindex enable frame-filter
7393 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
7394 Enable a frame filter in the dictionary matching
7395 @var{filter-dictionary} and @var{filter-name}. The
7396 @var{filter-dictionary} may be @code{all}, @code{global},
7397 @code{progspace} or the name of the object file where the frame filter
7398 dictionary resides. When @code{all} is specified, all frame filters across
7399 all dictionaries are enabled. The @var{filter-name} is the name of the frame
7400 filter and is used when @code{all} is not the option for
7401 @var{filter-dictionary}.
7406 (gdb) info frame-filter
7408 global frame-filters:
7409 Priority Enabled Name
7410 1000 No PrimaryFunctionFilter
7413 progspace /build/test frame-filters:
7414 Priority Enabled Name
7415 100 Yes ProgspaceFilter
7417 objfile /build/test frame-filters:
7418 Priority Enabled Name
7419 999 Yes BuildProgra Filter
7421 (gdb) disable frame-filter /build/test BuildProgramFilter
7422 (gdb) info frame-filter
7424 global frame-filters:
7425 Priority Enabled Name
7426 1000 No PrimaryFunctionFilter
7429 progspace /build/test frame-filters:
7430 Priority Enabled Name
7431 100 Yes ProgspaceFilter
7433 objfile /build/test frame-filters:
7434 Priority Enabled Name
7435 999 No BuildProgramFilter
7437 (gdb) enable frame-filter global PrimaryFunctionFilter
7438 (gdb) info frame-filter
7440 global frame-filters:
7441 Priority Enabled Name
7442 1000 Yes PrimaryFunctionFilter
7445 progspace /build/test frame-filters:
7446 Priority Enabled Name
7447 100 Yes ProgspaceFilter
7449 objfile /build/test frame-filters:
7450 Priority Enabled Name
7451 999 No BuildProgramFilter
7454 @kindex set frame-filter priority
7455 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
7456 Set the @var{priority} of a frame filter in the dictionary matching
7457 @var{filter-dictionary}, and the frame filter name matching
7458 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7459 @code{progspace} or the name of the object file where the frame filter
7460 dictionary resides. The @var{priority} is an integer.
7462 @kindex show frame-filter priority
7463 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
7464 Show the @var{priority} of a frame filter in the dictionary matching
7465 @var{filter-dictionary}, and the frame filter name matching
7466 @var{filter-name}. The @var{filter-dictionary} may be @code{global},
7467 @code{progspace} or the name of the object file where the frame filter
7473 (gdb) info frame-filter
7475 global frame-filters:
7476 Priority Enabled Name
7477 1000 Yes PrimaryFunctionFilter
7480 progspace /build/test frame-filters:
7481 Priority Enabled Name
7482 100 Yes ProgspaceFilter
7484 objfile /build/test frame-filters:
7485 Priority Enabled Name
7486 999 No BuildProgramFilter
7488 (gdb) set frame-filter priority global Reverse 50
7489 (gdb) info frame-filter
7491 global frame-filters:
7492 Priority Enabled Name
7493 1000 Yes PrimaryFunctionFilter
7496 progspace /build/test frame-filters:
7497 Priority Enabled Name
7498 100 Yes ProgspaceFilter
7500 objfile /build/test frame-filters:
7501 Priority Enabled Name
7502 999 No BuildProgramFilter
7507 @chapter Examining Source Files
7509 @value{GDBN} can print parts of your program's source, since the debugging
7510 information recorded in the program tells @value{GDBN} what source files were
7511 used to build it. When your program stops, @value{GDBN} spontaneously prints
7512 the line where it stopped. Likewise, when you select a stack frame
7513 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7514 execution in that frame has stopped. You can print other portions of
7515 source files by explicit command.
7517 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7518 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7519 @value{GDBN} under @sc{gnu} Emacs}.
7522 * List:: Printing source lines
7523 * Specify Location:: How to specify code locations
7524 * Edit:: Editing source files
7525 * Search:: Searching source files
7526 * Source Path:: Specifying source directories
7527 * Machine Code:: Source and machine code
7531 @section Printing Source Lines
7534 @kindex l @r{(@code{list})}
7535 To print lines from a source file, use the @code{list} command
7536 (abbreviated @code{l}). By default, ten lines are printed.
7537 There are several ways to specify what part of the file you want to
7538 print; see @ref{Specify Location}, for the full list.
7540 Here are the forms of the @code{list} command most commonly used:
7543 @item list @var{linenum}
7544 Print lines centered around line number @var{linenum} in the
7545 current source file.
7547 @item list @var{function}
7548 Print lines centered around the beginning of function
7552 Print more lines. If the last lines printed were printed with a
7553 @code{list} command, this prints lines following the last lines
7554 printed; however, if the last line printed was a solitary line printed
7555 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7556 Stack}), this prints lines centered around that line.
7559 Print lines just before the lines last printed.
7562 @cindex @code{list}, how many lines to display
7563 By default, @value{GDBN} prints ten source lines with any of these forms of
7564 the @code{list} command. You can change this using @code{set listsize}:
7567 @kindex set listsize
7568 @item set listsize @var{count}
7569 @itemx set listsize unlimited
7570 Make the @code{list} command display @var{count} source lines (unless
7571 the @code{list} argument explicitly specifies some other number).
7572 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7574 @kindex show listsize
7576 Display the number of lines that @code{list} prints.
7579 Repeating a @code{list} command with @key{RET} discards the argument,
7580 so it is equivalent to typing just @code{list}. This is more useful
7581 than listing the same lines again. An exception is made for an
7582 argument of @samp{-}; that argument is preserved in repetition so that
7583 each repetition moves up in the source file.
7585 In general, the @code{list} command expects you to supply zero, one or two
7586 @dfn{locations}. Locations specify source lines; there are several ways
7587 of writing them (@pxref{Specify Location}), but the effect is always
7588 to specify some source line.
7590 Here is a complete description of the possible arguments for @code{list}:
7593 @item list @var{location}
7594 Print lines centered around the line specified by @var{location}.
7596 @item list @var{first},@var{last}
7597 Print lines from @var{first} to @var{last}. Both arguments are
7598 locations. When a @code{list} command has two locations, and the
7599 source file of the second location is omitted, this refers to
7600 the same source file as the first location.
7602 @item list ,@var{last}
7603 Print lines ending with @var{last}.
7605 @item list @var{first},
7606 Print lines starting with @var{first}.
7609 Print lines just after the lines last printed.
7612 Print lines just before the lines last printed.
7615 As described in the preceding table.
7618 @node Specify Location
7619 @section Specifying a Location
7620 @cindex specifying location
7622 @cindex source location
7625 * Linespec Locations:: Linespec locations
7626 * Explicit Locations:: Explicit locations
7627 * Address Locations:: Address locations
7630 Several @value{GDBN} commands accept arguments that specify a location
7631 of your program's code. Since @value{GDBN} is a source-level
7632 debugger, a location usually specifies some line in the source code.
7633 Locations may be specified using three different formats:
7634 linespec locations, explicit locations, or address locations.
7636 @node Linespec Locations
7637 @subsection Linespec Locations
7638 @cindex linespec locations
7640 A @dfn{linespec} is a colon-separated list of source location parameters such
7641 as file name, function name, etc. Here are all the different ways of
7642 specifying a linespec:
7646 Specifies the line number @var{linenum} of the current source file.
7649 @itemx +@var{offset}
7650 Specifies the line @var{offset} lines before or after the @dfn{current
7651 line}. For the @code{list} command, the current line is the last one
7652 printed; for the breakpoint commands, this is the line at which
7653 execution stopped in the currently selected @dfn{stack frame}
7654 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7655 used as the second of the two linespecs in a @code{list} command,
7656 this specifies the line @var{offset} lines up or down from the first
7659 @item @var{filename}:@var{linenum}
7660 Specifies the line @var{linenum} in the source file @var{filename}.
7661 If @var{filename} is a relative file name, then it will match any
7662 source file name with the same trailing components. For example, if
7663 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7664 name of @file{/build/trunk/gcc/expr.c}, but not
7665 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7667 @item @var{function}
7668 Specifies the line that begins the body of the function @var{function}.
7669 For example, in C, this is the line with the open brace.
7671 @item @var{function}:@var{label}
7672 Specifies the line where @var{label} appears in @var{function}.
7674 @item @var{filename}:@var{function}
7675 Specifies the line that begins the body of the function @var{function}
7676 in the file @var{filename}. You only need the file name with a
7677 function name to avoid ambiguity when there are identically named
7678 functions in different source files.
7681 Specifies the line at which the label named @var{label} appears
7682 in the function corresponding to the currently selected stack frame.
7683 If there is no current selected stack frame (for instance, if the inferior
7684 is not running), then @value{GDBN} will not search for a label.
7686 @cindex breakpoint at static probe point
7687 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7688 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7689 applications to embed static probes. @xref{Static Probe Points}, for more
7690 information on finding and using static probes. This form of linespec
7691 specifies the location of such a static probe.
7693 If @var{objfile} is given, only probes coming from that shared library
7694 or executable matching @var{objfile} as a regular expression are considered.
7695 If @var{provider} is given, then only probes from that provider are considered.
7696 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7697 each one of those probes.
7700 @node Explicit Locations
7701 @subsection Explicit Locations
7702 @cindex explicit locations
7704 @dfn{Explicit locations} allow the user to directly specify the source
7705 location's parameters using option-value pairs.
7707 Explicit locations are useful when several functions, labels, or
7708 file names have the same name (base name for files) in the program's
7709 sources. In these cases, explicit locations point to the source
7710 line you meant more accurately and unambiguously. Also, using
7711 explicit locations might be faster in large programs.
7713 For example, the linespec @samp{foo:bar} may refer to a function @code{bar}
7714 defined in the file named @file{foo} or the label @code{bar} in a function
7715 named @code{foo}. @value{GDBN} must search either the file system or
7716 the symbol table to know.
7718 The list of valid explicit location options is summarized in the
7722 @item -source @var{filename}
7723 The value specifies the source file name. To differentiate between
7724 files with the same base name, prepend as many directories as is necessary
7725 to uniquely identify the desired file, e.g., @file{foo/bar/baz.c}. Otherwise
7726 @value{GDBN} will use the first file it finds with the given base
7727 name. This option requires the use of either @code{-function} or @code{-line}.
7729 @item -function @var{function}
7730 The value specifies the name of a function. Operations
7731 on function locations unmodified by other options (such as @code{-label}
7732 or @code{-line}) refer to the line that begins the body of the function.
7733 In C, for example, this is the line with the open brace.
7735 @item -label @var{label}
7736 The value specifies the name of a label. When the function
7737 name is not specified, the label is searched in the function of the currently
7738 selected stack frame.
7740 @item -line @var{number}
7741 The value specifies a line offset for the location. The offset may either
7742 be absolute (@code{-line 3}) or relative (@code{-line +3}), depending on
7743 the command. When specified without any other options, the line offset is
7744 relative to the current line.
7747 Explicit location options may be abbreviated by omitting any non-unique
7748 trailing characters from the option name, e.g., @code{break -s main.c -li 3}.
7750 @node Address Locations
7751 @subsection Address Locations
7752 @cindex address locations
7754 @dfn{Address locations} indicate a specific program address. They have
7755 the generalized form *@var{address}.
7757 For line-oriented commands, such as @code{list} and @code{edit}, this
7758 specifies a source line that contains @var{address}. For @code{break} and
7759 other breakpoint-oriented commands, this can be used to set breakpoints in
7760 parts of your program which do not have debugging information or
7763 Here @var{address} may be any expression valid in the current working
7764 language (@pxref{Languages, working language}) that specifies a code
7765 address. In addition, as a convenience, @value{GDBN} extends the
7766 semantics of expressions used in locations to cover several situations
7767 that frequently occur during debugging. Here are the various forms
7771 @item @var{expression}
7772 Any expression valid in the current working language.
7774 @item @var{funcaddr}
7775 An address of a function or procedure derived from its name. In C,
7776 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7777 simply the function's name @var{function} (and actually a special case
7778 of a valid expression). In Pascal and Modula-2, this is
7779 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7780 (although the Pascal form also works).
7782 This form specifies the address of the function's first instruction,
7783 before the stack frame and arguments have been set up.
7785 @item '@var{filename}':@var{funcaddr}
7786 Like @var{funcaddr} above, but also specifies the name of the source
7787 file explicitly. This is useful if the name of the function does not
7788 specify the function unambiguously, e.g., if there are several
7789 functions with identical names in different source files.
7793 @section Editing Source Files
7794 @cindex editing source files
7797 @kindex e @r{(@code{edit})}
7798 To edit the lines in a source file, use the @code{edit} command.
7799 The editing program of your choice
7800 is invoked with the current line set to
7801 the active line in the program.
7802 Alternatively, there are several ways to specify what part of the file you
7803 want to print if you want to see other parts of the program:
7806 @item edit @var{location}
7807 Edit the source file specified by @code{location}. Editing starts at
7808 that @var{location}, e.g., at the specified source line of the
7809 specified file. @xref{Specify Location}, for all the possible forms
7810 of the @var{location} argument; here are the forms of the @code{edit}
7811 command most commonly used:
7814 @item edit @var{number}
7815 Edit the current source file with @var{number} as the active line number.
7817 @item edit @var{function}
7818 Edit the file containing @var{function} at the beginning of its definition.
7823 @subsection Choosing your Editor
7824 You can customize @value{GDBN} to use any editor you want
7826 The only restriction is that your editor (say @code{ex}), recognizes the
7827 following command-line syntax:
7829 ex +@var{number} file
7831 The optional numeric value +@var{number} specifies the number of the line in
7832 the file where to start editing.}.
7833 By default, it is @file{@value{EDITOR}}, but you can change this
7834 by setting the environment variable @code{EDITOR} before using
7835 @value{GDBN}. For example, to configure @value{GDBN} to use the
7836 @code{vi} editor, you could use these commands with the @code{sh} shell:
7842 or in the @code{csh} shell,
7844 setenv EDITOR /usr/bin/vi
7849 @section Searching Source Files
7850 @cindex searching source files
7852 There are two commands for searching through the current source file for a
7857 @kindex forward-search
7858 @kindex fo @r{(@code{forward-search})}
7859 @item forward-search @var{regexp}
7860 @itemx search @var{regexp}
7861 The command @samp{forward-search @var{regexp}} checks each line,
7862 starting with the one following the last line listed, for a match for
7863 @var{regexp}. It lists the line that is found. You can use the
7864 synonym @samp{search @var{regexp}} or abbreviate the command name as
7867 @kindex reverse-search
7868 @item reverse-search @var{regexp}
7869 The command @samp{reverse-search @var{regexp}} checks each line, starting
7870 with the one before the last line listed and going backward, for a match
7871 for @var{regexp}. It lists the line that is found. You can abbreviate
7872 this command as @code{rev}.
7876 @section Specifying Source Directories
7879 @cindex directories for source files
7880 Executable programs sometimes do not record the directories of the source
7881 files from which they were compiled, just the names. Even when they do,
7882 the directories could be moved between the compilation and your debugging
7883 session. @value{GDBN} has a list of directories to search for source files;
7884 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7885 it tries all the directories in the list, in the order they are present
7886 in the list, until it finds a file with the desired name.
7888 For example, suppose an executable references the file
7889 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7890 @file{/mnt/cross}. The file is first looked up literally; if this
7891 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7892 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7893 message is printed. @value{GDBN} does not look up the parts of the
7894 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7895 Likewise, the subdirectories of the source path are not searched: if
7896 the source path is @file{/mnt/cross}, and the binary refers to
7897 @file{foo.c}, @value{GDBN} would not find it under
7898 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7900 Plain file names, relative file names with leading directories, file
7901 names containing dots, etc.@: are all treated as described above; for
7902 instance, if the source path is @file{/mnt/cross}, and the source file
7903 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7904 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7905 that---@file{/mnt/cross/foo.c}.
7907 Note that the executable search path is @emph{not} used to locate the
7910 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7911 any information it has cached about where source files are found and where
7912 each line is in the file.
7916 When you start @value{GDBN}, its source path includes only @samp{cdir}
7917 and @samp{cwd}, in that order.
7918 To add other directories, use the @code{directory} command.
7920 The search path is used to find both program source files and @value{GDBN}
7921 script files (read using the @samp{-command} option and @samp{source} command).
7923 In addition to the source path, @value{GDBN} provides a set of commands
7924 that manage a list of source path substitution rules. A @dfn{substitution
7925 rule} specifies how to rewrite source directories stored in the program's
7926 debug information in case the sources were moved to a different
7927 directory between compilation and debugging. A rule is made of
7928 two strings, the first specifying what needs to be rewritten in
7929 the path, and the second specifying how it should be rewritten.
7930 In @ref{set substitute-path}, we name these two parts @var{from} and
7931 @var{to} respectively. @value{GDBN} does a simple string replacement
7932 of @var{from} with @var{to} at the start of the directory part of the
7933 source file name, and uses that result instead of the original file
7934 name to look up the sources.
7936 Using the previous example, suppose the @file{foo-1.0} tree has been
7937 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7938 @value{GDBN} to replace @file{/usr/src} in all source path names with
7939 @file{/mnt/cross}. The first lookup will then be
7940 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7941 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7942 substitution rule, use the @code{set substitute-path} command
7943 (@pxref{set substitute-path}).
7945 To avoid unexpected substitution results, a rule is applied only if the
7946 @var{from} part of the directory name ends at a directory separator.
7947 For instance, a rule substituting @file{/usr/source} into
7948 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7949 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7950 is applied only at the beginning of the directory name, this rule will
7951 not be applied to @file{/root/usr/source/baz.c} either.
7953 In many cases, you can achieve the same result using the @code{directory}
7954 command. However, @code{set substitute-path} can be more efficient in
7955 the case where the sources are organized in a complex tree with multiple
7956 subdirectories. With the @code{directory} command, you need to add each
7957 subdirectory of your project. If you moved the entire tree while
7958 preserving its internal organization, then @code{set substitute-path}
7959 allows you to direct the debugger to all the sources with one single
7962 @code{set substitute-path} is also more than just a shortcut command.
7963 The source path is only used if the file at the original location no
7964 longer exists. On the other hand, @code{set substitute-path} modifies
7965 the debugger behavior to look at the rewritten location instead. So, if
7966 for any reason a source file that is not relevant to your executable is
7967 located at the original location, a substitution rule is the only
7968 method available to point @value{GDBN} at the new location.
7970 @cindex @samp{--with-relocated-sources}
7971 @cindex default source path substitution
7972 You can configure a default source path substitution rule by
7973 configuring @value{GDBN} with the
7974 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7975 should be the name of a directory under @value{GDBN}'s configured
7976 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7977 directory names in debug information under @var{dir} will be adjusted
7978 automatically if the installed @value{GDBN} is moved to a new
7979 location. This is useful if @value{GDBN}, libraries or executables
7980 with debug information and corresponding source code are being moved
7984 @item directory @var{dirname} @dots{}
7985 @item dir @var{dirname} @dots{}
7986 Add directory @var{dirname} to the front of the source path. Several
7987 directory names may be given to this command, separated by @samp{:}
7988 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7989 part of absolute file names) or
7990 whitespace. You may specify a directory that is already in the source
7991 path; this moves it forward, so @value{GDBN} searches it sooner.
7995 @vindex $cdir@r{, convenience variable}
7996 @vindex $cwd@r{, convenience variable}
7997 @cindex compilation directory
7998 @cindex current directory
7999 @cindex working directory
8000 @cindex directory, current
8001 @cindex directory, compilation
8002 You can use the string @samp{$cdir} to refer to the compilation
8003 directory (if one is recorded), and @samp{$cwd} to refer to the current
8004 working directory. @samp{$cwd} is not the same as @samp{.}---the former
8005 tracks the current working directory as it changes during your @value{GDBN}
8006 session, while the latter is immediately expanded to the current
8007 directory at the time you add an entry to the source path.
8010 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
8012 @c RET-repeat for @code{directory} is explicitly disabled, but since
8013 @c repeating it would be a no-op we do not say that. (thanks to RMS)
8015 @item set directories @var{path-list}
8016 @kindex set directories
8017 Set the source path to @var{path-list}.
8018 @samp{$cdir:$cwd} are added if missing.
8020 @item show directories
8021 @kindex show directories
8022 Print the source path: show which directories it contains.
8024 @anchor{set substitute-path}
8025 @item set substitute-path @var{from} @var{to}
8026 @kindex set substitute-path
8027 Define a source path substitution rule, and add it at the end of the
8028 current list of existing substitution rules. If a rule with the same
8029 @var{from} was already defined, then the old rule is also deleted.
8031 For example, if the file @file{/foo/bar/baz.c} was moved to
8032 @file{/mnt/cross/baz.c}, then the command
8035 (@value{GDBP}) set substitute-path /foo/bar /mnt/cross
8039 will tell @value{GDBN} to replace @samp{/foo/bar} with
8040 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
8041 @file{baz.c} even though it was moved.
8043 In the case when more than one substitution rule have been defined,
8044 the rules are evaluated one by one in the order where they have been
8045 defined. The first one matching, if any, is selected to perform
8048 For instance, if we had entered the following commands:
8051 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
8052 (@value{GDBP}) set substitute-path /usr/src /mnt/src
8056 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
8057 @file{/mnt/include/defs.h} by using the first rule. However, it would
8058 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
8059 @file{/mnt/src/lib/foo.c}.
8062 @item unset substitute-path [path]
8063 @kindex unset substitute-path
8064 If a path is specified, search the current list of substitution rules
8065 for a rule that would rewrite that path. Delete that rule if found.
8066 A warning is emitted by the debugger if no rule could be found.
8068 If no path is specified, then all substitution rules are deleted.
8070 @item show substitute-path [path]
8071 @kindex show substitute-path
8072 If a path is specified, then print the source path substitution rule
8073 which would rewrite that path, if any.
8075 If no path is specified, then print all existing source path substitution
8080 If your source path is cluttered with directories that are no longer of
8081 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
8082 versions of source. You can correct the situation as follows:
8086 Use @code{directory} with no argument to reset the source path to its default value.
8089 Use @code{directory} with suitable arguments to reinstall the
8090 directories you want in the source path. You can add all the
8091 directories in one command.
8095 @section Source and Machine Code
8096 @cindex source line and its code address
8098 You can use the command @code{info line} to map source lines to program
8099 addresses (and vice versa), and the command @code{disassemble} to display
8100 a range of addresses as machine instructions. You can use the command
8101 @code{set disassemble-next-line} to set whether to disassemble next
8102 source line when execution stops. When run under @sc{gnu} Emacs
8103 mode, the @code{info line} command causes the arrow to point to the
8104 line specified. Also, @code{info line} prints addresses in symbolic form as
8109 @item info line @var{location}
8110 Print the starting and ending addresses of the compiled code for
8111 source line @var{location}. You can specify source lines in any of
8112 the ways documented in @ref{Specify Location}.
8115 For example, we can use @code{info line} to discover the location of
8116 the object code for the first line of function
8117 @code{m4_changequote}:
8119 @c FIXME: I think this example should also show the addresses in
8120 @c symbolic form, as they usually would be displayed.
8122 (@value{GDBP}) info line m4_changequote
8123 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
8127 @cindex code address and its source line
8128 We can also inquire (using @code{*@var{addr}} as the form for
8129 @var{location}) what source line covers a particular address:
8131 (@value{GDBP}) info line *0x63ff
8132 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
8135 @cindex @code{$_} and @code{info line}
8136 @cindex @code{x} command, default address
8137 @kindex x@r{(examine), and} info line
8138 After @code{info line}, the default address for the @code{x} command
8139 is changed to the starting address of the line, so that @samp{x/i} is
8140 sufficient to begin examining the machine code (@pxref{Memory,
8141 ,Examining Memory}). Also, this address is saved as the value of the
8142 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
8147 @cindex assembly instructions
8148 @cindex instructions, assembly
8149 @cindex machine instructions
8150 @cindex listing machine instructions
8152 @itemx disassemble /m
8153 @itemx disassemble /s
8154 @itemx disassemble /r
8155 This specialized command dumps a range of memory as machine
8156 instructions. It can also print mixed source+disassembly by specifying
8157 the @code{/m} or @code{/s} modifier and print the raw instructions in hex
8158 as well as in symbolic form by specifying the @code{/r} modifier.
8159 The default memory range is the function surrounding the
8160 program counter of the selected frame. A single argument to this
8161 command is a program counter value; @value{GDBN} dumps the function
8162 surrounding this value. When two arguments are given, they should
8163 be separated by a comma, possibly surrounded by whitespace. The
8164 arguments specify a range of addresses to dump, in one of two forms:
8167 @item @var{start},@var{end}
8168 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
8169 @item @var{start},+@var{length}
8170 the addresses from @var{start} (inclusive) to
8171 @code{@var{start}+@var{length}} (exclusive).
8175 When 2 arguments are specified, the name of the function is also
8176 printed (since there could be several functions in the given range).
8178 The argument(s) can be any expression yielding a numeric value, such as
8179 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
8181 If the range of memory being disassembled contains current program counter,
8182 the instruction at that location is shown with a @code{=>} marker.
8185 The following example shows the disassembly of a range of addresses of
8186 HP PA-RISC 2.0 code:
8189 (@value{GDBP}) disas 0x32c4, 0x32e4
8190 Dump of assembler code from 0x32c4 to 0x32e4:
8191 0x32c4 <main+204>: addil 0,dp
8192 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
8193 0x32cc <main+212>: ldil 0x3000,r31
8194 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
8195 0x32d4 <main+220>: ldo 0(r31),rp
8196 0x32d8 <main+224>: addil -0x800,dp
8197 0x32dc <main+228>: ldo 0x588(r1),r26
8198 0x32e0 <main+232>: ldil 0x3000,r31
8199 End of assembler dump.
8202 Here is an example showing mixed source+assembly for Intel x86
8203 with @code{/m} or @code{/s}, when the program is stopped just after
8204 function prologue in a non-optimized function with no inline code.
8207 (@value{GDBP}) disas /m main
8208 Dump of assembler code for function main:
8210 0x08048330 <+0>: push %ebp
8211 0x08048331 <+1>: mov %esp,%ebp
8212 0x08048333 <+3>: sub $0x8,%esp
8213 0x08048336 <+6>: and $0xfffffff0,%esp
8214 0x08048339 <+9>: sub $0x10,%esp
8216 6 printf ("Hello.\n");
8217 => 0x0804833c <+12>: movl $0x8048440,(%esp)
8218 0x08048343 <+19>: call 0x8048284 <puts@@plt>
8222 0x08048348 <+24>: mov $0x0,%eax
8223 0x0804834d <+29>: leave
8224 0x0804834e <+30>: ret
8226 End of assembler dump.
8229 The @code{/m} option is deprecated as its output is not useful when
8230 there is either inlined code or re-ordered code.
8231 The @code{/s} option is the preferred choice.
8232 Here is an example for AMD x86-64 showing the difference between
8233 @code{/m} output and @code{/s} output.
8234 This example has one inline function defined in a header file,
8235 and the code is compiled with @samp{-O2} optimization.
8236 Note how the @code{/m} output is missing the disassembly of
8237 several instructions that are present in the @code{/s} output.
8267 (@value{GDBP}) disas /m main
8268 Dump of assembler code for function main:
8272 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8273 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8277 0x000000000040041d <+29>: xor %eax,%eax
8278 0x000000000040041f <+31>: retq
8279 0x0000000000400420 <+32>: add %eax,%eax
8280 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8282 End of assembler dump.
8283 (@value{GDBP}) disas /s main
8284 Dump of assembler code for function main:
8288 0x0000000000400400 <+0>: mov 0x200c2e(%rip),%eax # 0x601034 <y>
8292 0x0000000000400406 <+6>: test %eax,%eax
8293 0x0000000000400408 <+8>: js 0x400420 <main+32>
8298 0x000000000040040a <+10>: lea 0xa(%rax),%edx
8299 0x000000000040040d <+13>: test %eax,%eax
8300 0x000000000040040f <+15>: mov $0x1,%eax
8301 0x0000000000400414 <+20>: cmovne %edx,%eax
8305 0x0000000000400417 <+23>: mov %eax,0x200c13(%rip) # 0x601030 <x>
8309 0x000000000040041d <+29>: xor %eax,%eax
8310 0x000000000040041f <+31>: retq
8314 0x0000000000400420 <+32>: add %eax,%eax
8315 0x0000000000400422 <+34>: jmp 0x400417 <main+23>
8316 End of assembler dump.
8319 Here is another example showing raw instructions in hex for AMD x86-64,
8322 (gdb) disas /r 0x400281,+10
8323 Dump of assembler code from 0x400281 to 0x40028b:
8324 0x0000000000400281: 38 36 cmp %dh,(%rsi)
8325 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
8326 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
8327 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
8328 End of assembler dump.
8331 Addresses cannot be specified as a location (@pxref{Specify Location}).
8332 So, for example, if you want to disassemble function @code{bar}
8333 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
8334 and not @samp{disassemble foo.c:bar}.
8336 Some architectures have more than one commonly-used set of instruction
8337 mnemonics or other syntax.
8339 For programs that were dynamically linked and use shared libraries,
8340 instructions that call functions or branch to locations in the shared
8341 libraries might show a seemingly bogus location---it's actually a
8342 location of the relocation table. On some architectures, @value{GDBN}
8343 might be able to resolve these to actual function names.
8346 @kindex set disassembly-flavor
8347 @cindex Intel disassembly flavor
8348 @cindex AT&T disassembly flavor
8349 @item set disassembly-flavor @var{instruction-set}
8350 Select the instruction set to use when disassembling the
8351 program via the @code{disassemble} or @code{x/i} commands.
8353 Currently this command is only defined for the Intel x86 family. You
8354 can set @var{instruction-set} to either @code{intel} or @code{att}.
8355 The default is @code{att}, the AT&T flavor used by default by Unix
8356 assemblers for x86-based targets.
8358 @kindex show disassembly-flavor
8359 @item show disassembly-flavor
8360 Show the current setting of the disassembly flavor.
8364 @kindex set disassemble-next-line
8365 @kindex show disassemble-next-line
8366 @item set disassemble-next-line
8367 @itemx show disassemble-next-line
8368 Control whether or not @value{GDBN} will disassemble the next source
8369 line or instruction when execution stops. If ON, @value{GDBN} will
8370 display disassembly of the next source line when execution of the
8371 program being debugged stops. This is @emph{in addition} to
8372 displaying the source line itself, which @value{GDBN} always does if
8373 possible. If the next source line cannot be displayed for some reason
8374 (e.g., if @value{GDBN} cannot find the source file, or there's no line
8375 info in the debug info), @value{GDBN} will display disassembly of the
8376 next @emph{instruction} instead of showing the next source line. If
8377 AUTO, @value{GDBN} will display disassembly of next instruction only
8378 if the source line cannot be displayed. This setting causes
8379 @value{GDBN} to display some feedback when you step through a function
8380 with no line info or whose source file is unavailable. The default is
8381 OFF, which means never display the disassembly of the next line or
8387 @chapter Examining Data
8389 @cindex printing data
8390 @cindex examining data
8393 The usual way to examine data in your program is with the @code{print}
8394 command (abbreviated @code{p}), or its synonym @code{inspect}. It
8395 evaluates and prints the value of an expression of the language your
8396 program is written in (@pxref{Languages, ,Using @value{GDBN} with
8397 Different Languages}). It may also print the expression using a
8398 Python-based pretty-printer (@pxref{Pretty Printing}).
8401 @item print @var{expr}
8402 @itemx print /@var{f} @var{expr}
8403 @var{expr} is an expression (in the source language). By default the
8404 value of @var{expr} is printed in a format appropriate to its data type;
8405 you can choose a different format by specifying @samp{/@var{f}}, where
8406 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
8410 @itemx print /@var{f}
8411 @cindex reprint the last value
8412 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
8413 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
8414 conveniently inspect the same value in an alternative format.
8417 A more low-level way of examining data is with the @code{x} command.
8418 It examines data in memory at a specified address and prints it in a
8419 specified format. @xref{Memory, ,Examining Memory}.
8421 If you are interested in information about types, or about how the
8422 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
8423 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
8426 @cindex exploring hierarchical data structures
8428 Another way of examining values of expressions and type information is
8429 through the Python extension command @code{explore} (available only if
8430 the @value{GDBN} build is configured with @code{--with-python}). It
8431 offers an interactive way to start at the highest level (or, the most
8432 abstract level) of the data type of an expression (or, the data type
8433 itself) and explore all the way down to leaf scalar values/fields
8434 embedded in the higher level data types.
8437 @item explore @var{arg}
8438 @var{arg} is either an expression (in the source language), or a type
8439 visible in the current context of the program being debugged.
8442 The working of the @code{explore} command can be illustrated with an
8443 example. If a data type @code{struct ComplexStruct} is defined in your
8453 struct ComplexStruct
8455 struct SimpleStruct *ss_p;
8461 followed by variable declarations as
8464 struct SimpleStruct ss = @{ 10, 1.11 @};
8465 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
8469 then, the value of the variable @code{cs} can be explored using the
8470 @code{explore} command as follows.
8474 The value of `cs' is a struct/class of type `struct ComplexStruct' with
8475 the following fields:
8477 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
8478 arr = <Enter 1 to explore this field of type `int [10]'>
8480 Enter the field number of choice:
8484 Since the fields of @code{cs} are not scalar values, you are being
8485 prompted to chose the field you want to explore. Let's say you choose
8486 the field @code{ss_p} by entering @code{0}. Then, since this field is a
8487 pointer, you will be asked if it is pointing to a single value. From
8488 the declaration of @code{cs} above, it is indeed pointing to a single
8489 value, hence you enter @code{y}. If you enter @code{n}, then you will
8490 be asked if it were pointing to an array of values, in which case this
8491 field will be explored as if it were an array.
8494 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
8495 Continue exploring it as a pointer to a single value [y/n]: y
8496 The value of `*(cs.ss_p)' is a struct/class of type `struct
8497 SimpleStruct' with the following fields:
8499 i = 10 .. (Value of type `int')
8500 d = 1.1100000000000001 .. (Value of type `double')
8502 Press enter to return to parent value:
8506 If the field @code{arr} of @code{cs} was chosen for exploration by
8507 entering @code{1} earlier, then since it is as array, you will be
8508 prompted to enter the index of the element in the array that you want
8512 `cs.arr' is an array of `int'.
8513 Enter the index of the element you want to explore in `cs.arr': 5
8515 `(cs.arr)[5]' is a scalar value of type `int'.
8519 Press enter to return to parent value:
8522 In general, at any stage of exploration, you can go deeper towards the
8523 leaf values by responding to the prompts appropriately, or hit the
8524 return key to return to the enclosing data structure (the @i{higher}
8525 level data structure).
8527 Similar to exploring values, you can use the @code{explore} command to
8528 explore types. Instead of specifying a value (which is typically a
8529 variable name or an expression valid in the current context of the
8530 program being debugged), you specify a type name. If you consider the
8531 same example as above, your can explore the type
8532 @code{struct ComplexStruct} by passing the argument
8533 @code{struct ComplexStruct} to the @code{explore} command.
8536 (gdb) explore struct ComplexStruct
8540 By responding to the prompts appropriately in the subsequent interactive
8541 session, you can explore the type @code{struct ComplexStruct} in a
8542 manner similar to how the value @code{cs} was explored in the above
8545 The @code{explore} command also has two sub-commands,
8546 @code{explore value} and @code{explore type}. The former sub-command is
8547 a way to explicitly specify that value exploration of the argument is
8548 being invoked, while the latter is a way to explicitly specify that type
8549 exploration of the argument is being invoked.
8552 @item explore value @var{expr}
8553 @cindex explore value
8554 This sub-command of @code{explore} explores the value of the
8555 expression @var{expr} (if @var{expr} is an expression valid in the
8556 current context of the program being debugged). The behavior of this
8557 command is identical to that of the behavior of the @code{explore}
8558 command being passed the argument @var{expr}.
8560 @item explore type @var{arg}
8561 @cindex explore type
8562 This sub-command of @code{explore} explores the type of @var{arg} (if
8563 @var{arg} is a type visible in the current context of program being
8564 debugged), or the type of the value/expression @var{arg} (if @var{arg}
8565 is an expression valid in the current context of the program being
8566 debugged). If @var{arg} is a type, then the behavior of this command is
8567 identical to that of the @code{explore} command being passed the
8568 argument @var{arg}. If @var{arg} is an expression, then the behavior of
8569 this command will be identical to that of the @code{explore} command
8570 being passed the type of @var{arg} as the argument.
8574 * Expressions:: Expressions
8575 * Ambiguous Expressions:: Ambiguous Expressions
8576 * Variables:: Program variables
8577 * Arrays:: Artificial arrays
8578 * Output Formats:: Output formats
8579 * Memory:: Examining memory
8580 * Auto Display:: Automatic display
8581 * Print Settings:: Print settings
8582 * Pretty Printing:: Python pretty printing
8583 * Value History:: Value history
8584 * Convenience Vars:: Convenience variables
8585 * Convenience Funs:: Convenience functions
8586 * Registers:: Registers
8587 * Floating Point Hardware:: Floating point hardware
8588 * Vector Unit:: Vector Unit
8589 * OS Information:: Auxiliary data provided by operating system
8590 * Memory Region Attributes:: Memory region attributes
8591 * Dump/Restore Files:: Copy between memory and a file
8592 * Core File Generation:: Cause a program dump its core
8593 * Character Sets:: Debugging programs that use a different
8594 character set than GDB does
8595 * Caching Target Data:: Data caching for targets
8596 * Searching Memory:: Searching memory for a sequence of bytes
8600 @section Expressions
8603 @code{print} and many other @value{GDBN} commands accept an expression and
8604 compute its value. Any kind of constant, variable or operator defined
8605 by the programming language you are using is valid in an expression in
8606 @value{GDBN}. This includes conditional expressions, function calls,
8607 casts, and string constants. It also includes preprocessor macros, if
8608 you compiled your program to include this information; see
8611 @cindex arrays in expressions
8612 @value{GDBN} supports array constants in expressions input by
8613 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8614 you can use the command @code{print @{1, 2, 3@}} to create an array
8615 of three integers. If you pass an array to a function or assign it
8616 to a program variable, @value{GDBN} copies the array to memory that
8617 is @code{malloc}ed in the target program.
8619 Because C is so widespread, most of the expressions shown in examples in
8620 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8621 Languages}, for information on how to use expressions in other
8624 In this section, we discuss operators that you can use in @value{GDBN}
8625 expressions regardless of your programming language.
8627 @cindex casts, in expressions
8628 Casts are supported in all languages, not just in C, because it is so
8629 useful to cast a number into a pointer in order to examine a structure
8630 at that address in memory.
8631 @c FIXME: casts supported---Mod2 true?
8633 @value{GDBN} supports these operators, in addition to those common
8634 to programming languages:
8638 @samp{@@} is a binary operator for treating parts of memory as arrays.
8639 @xref{Arrays, ,Artificial Arrays}, for more information.
8642 @samp{::} allows you to specify a variable in terms of the file or
8643 function where it is defined. @xref{Variables, ,Program Variables}.
8645 @cindex @{@var{type}@}
8646 @cindex type casting memory
8647 @cindex memory, viewing as typed object
8648 @cindex casts, to view memory
8649 @item @{@var{type}@} @var{addr}
8650 Refers to an object of type @var{type} stored at address @var{addr} in
8651 memory. The address @var{addr} may be any expression whose value is
8652 an integer or pointer (but parentheses are required around binary
8653 operators, just as in a cast). This construct is allowed regardless
8654 of what kind of data is normally supposed to reside at @var{addr}.
8657 @node Ambiguous Expressions
8658 @section Ambiguous Expressions
8659 @cindex ambiguous expressions
8661 Expressions can sometimes contain some ambiguous elements. For instance,
8662 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8663 a single function name to be defined several times, for application in
8664 different contexts. This is called @dfn{overloading}. Another example
8665 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8666 templates and is typically instantiated several times, resulting in
8667 the same function name being defined in different contexts.
8669 In some cases and depending on the language, it is possible to adjust
8670 the expression to remove the ambiguity. For instance in C@t{++}, you
8671 can specify the signature of the function you want to break on, as in
8672 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8673 qualified name of your function often makes the expression unambiguous
8676 When an ambiguity that needs to be resolved is detected, the debugger
8677 has the capability to display a menu of numbered choices for each
8678 possibility, and then waits for the selection with the prompt @samp{>}.
8679 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8680 aborts the current command. If the command in which the expression was
8681 used allows more than one choice to be selected, the next option in the
8682 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8685 For example, the following session excerpt shows an attempt to set a
8686 breakpoint at the overloaded symbol @code{String::after}.
8687 We choose three particular definitions of that function name:
8689 @c FIXME! This is likely to change to show arg type lists, at least
8692 (@value{GDBP}) b String::after
8695 [2] file:String.cc; line number:867
8696 [3] file:String.cc; line number:860
8697 [4] file:String.cc; line number:875
8698 [5] file:String.cc; line number:853
8699 [6] file:String.cc; line number:846
8700 [7] file:String.cc; line number:735
8702 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8703 Breakpoint 2 at 0xb344: file String.cc, line 875.
8704 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8705 Multiple breakpoints were set.
8706 Use the "delete" command to delete unwanted
8713 @kindex set multiple-symbols
8714 @item set multiple-symbols @var{mode}
8715 @cindex multiple-symbols menu
8717 This option allows you to adjust the debugger behavior when an expression
8720 By default, @var{mode} is set to @code{all}. If the command with which
8721 the expression is used allows more than one choice, then @value{GDBN}
8722 automatically selects all possible choices. For instance, inserting
8723 a breakpoint on a function using an ambiguous name results in a breakpoint
8724 inserted on each possible match. However, if a unique choice must be made,
8725 then @value{GDBN} uses the menu to help you disambiguate the expression.
8726 For instance, printing the address of an overloaded function will result
8727 in the use of the menu.
8729 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8730 when an ambiguity is detected.
8732 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8733 an error due to the ambiguity and the command is aborted.
8735 @kindex show multiple-symbols
8736 @item show multiple-symbols
8737 Show the current value of the @code{multiple-symbols} setting.
8741 @section Program Variables
8743 The most common kind of expression to use is the name of a variable
8746 Variables in expressions are understood in the selected stack frame
8747 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8751 global (or file-static)
8758 visible according to the scope rules of the
8759 programming language from the point of execution in that frame
8762 @noindent This means that in the function
8777 you can examine and use the variable @code{a} whenever your program is
8778 executing within the function @code{foo}, but you can only use or
8779 examine the variable @code{b} while your program is executing inside
8780 the block where @code{b} is declared.
8782 @cindex variable name conflict
8783 There is an exception: you can refer to a variable or function whose
8784 scope is a single source file even if the current execution point is not
8785 in this file. But it is possible to have more than one such variable or
8786 function with the same name (in different source files). If that
8787 happens, referring to that name has unpredictable effects. If you wish,
8788 you can specify a static variable in a particular function or file by
8789 using the colon-colon (@code{::}) notation:
8791 @cindex colon-colon, context for variables/functions
8793 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8794 @cindex @code{::}, context for variables/functions
8797 @var{file}::@var{variable}
8798 @var{function}::@var{variable}
8802 Here @var{file} or @var{function} is the name of the context for the
8803 static @var{variable}. In the case of file names, you can use quotes to
8804 make sure @value{GDBN} parses the file name as a single word---for example,
8805 to print a global value of @code{x} defined in @file{f2.c}:
8808 (@value{GDBP}) p 'f2.c'::x
8811 The @code{::} notation is normally used for referring to
8812 static variables, since you typically disambiguate uses of local variables
8813 in functions by selecting the appropriate frame and using the
8814 simple name of the variable. However, you may also use this notation
8815 to refer to local variables in frames enclosing the selected frame:
8824 process (a); /* Stop here */
8835 For example, if there is a breakpoint at the commented line,
8836 here is what you might see
8837 when the program stops after executing the call @code{bar(0)}:
8842 (@value{GDBP}) p bar::a
8845 #2 0x080483d0 in foo (a=5) at foobar.c:12
8848 (@value{GDBP}) p bar::a
8852 @cindex C@t{++} scope resolution
8853 These uses of @samp{::} are very rarely in conflict with the very
8854 similar use of the same notation in C@t{++}. When they are in
8855 conflict, the C@t{++} meaning takes precedence; however, this can be
8856 overridden by quoting the file or function name with single quotes.
8858 For example, suppose the program is stopped in a method of a class
8859 that has a field named @code{includefile}, and there is also an
8860 include file named @file{includefile} that defines a variable,
8864 (@value{GDBP}) p includefile
8866 (@value{GDBP}) p includefile::some_global
8867 A syntax error in expression, near `'.
8868 (@value{GDBP}) p 'includefile'::some_global
8872 @cindex wrong values
8873 @cindex variable values, wrong
8874 @cindex function entry/exit, wrong values of variables
8875 @cindex optimized code, wrong values of variables
8877 @emph{Warning:} Occasionally, a local variable may appear to have the
8878 wrong value at certain points in a function---just after entry to a new
8879 scope, and just before exit.
8881 You may see this problem when you are stepping by machine instructions.
8882 This is because, on most machines, it takes more than one instruction to
8883 set up a stack frame (including local variable definitions); if you are
8884 stepping by machine instructions, variables may appear to have the wrong
8885 values until the stack frame is completely built. On exit, it usually
8886 also takes more than one machine instruction to destroy a stack frame;
8887 after you begin stepping through that group of instructions, local
8888 variable definitions may be gone.
8890 This may also happen when the compiler does significant optimizations.
8891 To be sure of always seeing accurate values, turn off all optimization
8894 @cindex ``No symbol "foo" in current context''
8895 Another possible effect of compiler optimizations is to optimize
8896 unused variables out of existence, or assign variables to registers (as
8897 opposed to memory addresses). Depending on the support for such cases
8898 offered by the debug info format used by the compiler, @value{GDBN}
8899 might not be able to display values for such local variables. If that
8900 happens, @value{GDBN} will print a message like this:
8903 No symbol "foo" in current context.
8906 To solve such problems, either recompile without optimizations, or use a
8907 different debug info format, if the compiler supports several such
8908 formats. @xref{Compilation}, for more information on choosing compiler
8909 options. @xref{C, ,C and C@t{++}}, for more information about debug
8910 info formats that are best suited to C@t{++} programs.
8912 If you ask to print an object whose contents are unknown to
8913 @value{GDBN}, e.g., because its data type is not completely specified
8914 by the debug information, @value{GDBN} will say @samp{<incomplete
8915 type>}. @xref{Symbols, incomplete type}, for more about this.
8917 If you append @kbd{@@entry} string to a function parameter name you get its
8918 value at the time the function got called. If the value is not available an
8919 error message is printed. Entry values are available only with some compilers.
8920 Entry values are normally also printed at the function parameter list according
8921 to @ref{set print entry-values}.
8924 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8930 (gdb) print i@@entry
8934 Strings are identified as arrays of @code{char} values without specified
8935 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8936 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8937 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8938 defines literal string type @code{"char"} as @code{char} without a sign.
8943 signed char var1[] = "A";
8946 You get during debugging
8951 $2 = @{65 'A', 0 '\0'@}
8955 @section Artificial Arrays
8957 @cindex artificial array
8959 @kindex @@@r{, referencing memory as an array}
8960 It is often useful to print out several successive objects of the
8961 same type in memory; a section of an array, or an array of
8962 dynamically determined size for which only a pointer exists in the
8965 You can do this by referring to a contiguous span of memory as an
8966 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8967 operand of @samp{@@} should be the first element of the desired array
8968 and be an individual object. The right operand should be the desired length
8969 of the array. The result is an array value whose elements are all of
8970 the type of the left argument. The first element is actually the left
8971 argument; the second element comes from bytes of memory immediately
8972 following those that hold the first element, and so on. Here is an
8973 example. If a program says
8976 int *array = (int *) malloc (len * sizeof (int));
8980 you can print the contents of @code{array} with
8986 The left operand of @samp{@@} must reside in memory. Array values made
8987 with @samp{@@} in this way behave just like other arrays in terms of
8988 subscripting, and are coerced to pointers when used in expressions.
8989 Artificial arrays most often appear in expressions via the value history
8990 (@pxref{Value History, ,Value History}), after printing one out.
8992 Another way to create an artificial array is to use a cast.
8993 This re-interprets a value as if it were an array.
8994 The value need not be in memory:
8996 (@value{GDBP}) p/x (short[2])0x12345678
8997 $1 = @{0x1234, 0x5678@}
9000 As a convenience, if you leave the array length out (as in
9001 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
9002 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
9004 (@value{GDBP}) p/x (short[])0x12345678
9005 $2 = @{0x1234, 0x5678@}
9008 Sometimes the artificial array mechanism is not quite enough; in
9009 moderately complex data structures, the elements of interest may not
9010 actually be adjacent---for example, if you are interested in the values
9011 of pointers in an array. One useful work-around in this situation is
9012 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
9013 Variables}) as a counter in an expression that prints the first
9014 interesting value, and then repeat that expression via @key{RET}. For
9015 instance, suppose you have an array @code{dtab} of pointers to
9016 structures, and you are interested in the values of a field @code{fv}
9017 in each structure. Here is an example of what you might type:
9027 @node Output Formats
9028 @section Output Formats
9030 @cindex formatted output
9031 @cindex output formats
9032 By default, @value{GDBN} prints a value according to its data type. Sometimes
9033 this is not what you want. For example, you might want to print a number
9034 in hex, or a pointer in decimal. Or you might want to view data in memory
9035 at a certain address as a character string or as an instruction. To do
9036 these things, specify an @dfn{output format} when you print a value.
9038 The simplest use of output formats is to say how to print a value
9039 already computed. This is done by starting the arguments of the
9040 @code{print} command with a slash and a format letter. The format
9041 letters supported are:
9045 Regard the bits of the value as an integer, and print the integer in
9049 Print as integer in signed decimal.
9052 Print as integer in unsigned decimal.
9055 Print as integer in octal.
9058 Print as integer in binary. The letter @samp{t} stands for ``two''.
9059 @footnote{@samp{b} cannot be used because these format letters are also
9060 used with the @code{x} command, where @samp{b} stands for ``byte'';
9061 see @ref{Memory,,Examining Memory}.}
9064 @cindex unknown address, locating
9065 @cindex locate address
9066 Print as an address, both absolute in hexadecimal and as an offset from
9067 the nearest preceding symbol. You can use this format used to discover
9068 where (in what function) an unknown address is located:
9071 (@value{GDBP}) p/a 0x54320
9072 $3 = 0x54320 <_initialize_vx+396>
9076 The command @code{info symbol 0x54320} yields similar results.
9077 @xref{Symbols, info symbol}.
9080 Regard as an integer and print it as a character constant. This
9081 prints both the numerical value and its character representation. The
9082 character representation is replaced with the octal escape @samp{\nnn}
9083 for characters outside the 7-bit @sc{ascii} range.
9085 Without this format, @value{GDBN} displays @code{char},
9086 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
9087 constants. Single-byte members of vectors are displayed as integer
9091 Regard the bits of the value as a floating point number and print
9092 using typical floating point syntax.
9095 @cindex printing strings
9096 @cindex printing byte arrays
9097 Regard as a string, if possible. With this format, pointers to single-byte
9098 data are displayed as null-terminated strings and arrays of single-byte data
9099 are displayed as fixed-length strings. Other values are displayed in their
9102 Without this format, @value{GDBN} displays pointers to and arrays of
9103 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
9104 strings. Single-byte members of a vector are displayed as an integer
9108 Like @samp{x} formatting, the value is treated as an integer and
9109 printed as hexadecimal, but leading zeros are printed to pad the value
9110 to the size of the integer type.
9113 @cindex raw printing
9114 Print using the @samp{raw} formatting. By default, @value{GDBN} will
9115 use a Python-based pretty-printer, if one is available (@pxref{Pretty
9116 Printing}). This typically results in a higher-level display of the
9117 value's contents. The @samp{r} format bypasses any Python
9118 pretty-printer which might exist.
9121 For example, to print the program counter in hex (@pxref{Registers}), type
9128 Note that no space is required before the slash; this is because command
9129 names in @value{GDBN} cannot contain a slash.
9131 To reprint the last value in the value history with a different format,
9132 you can use the @code{print} command with just a format and no
9133 expression. For example, @samp{p/x} reprints the last value in hex.
9136 @section Examining Memory
9138 You can use the command @code{x} (for ``examine'') to examine memory in
9139 any of several formats, independently of your program's data types.
9141 @cindex examining memory
9143 @kindex x @r{(examine memory)}
9144 @item x/@var{nfu} @var{addr}
9147 Use the @code{x} command to examine memory.
9150 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
9151 much memory to display and how to format it; @var{addr} is an
9152 expression giving the address where you want to start displaying memory.
9153 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
9154 Several commands set convenient defaults for @var{addr}.
9157 @item @var{n}, the repeat count
9158 The repeat count is a decimal integer; the default is 1. It specifies
9159 how much memory (counting by units @var{u}) to display.
9160 @c This really is **decimal**; unaffected by 'set radix' as of GDB
9163 @item @var{f}, the display format
9164 The display format is one of the formats used by @code{print}
9165 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
9166 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
9167 The default is @samp{x} (hexadecimal) initially. The default changes
9168 each time you use either @code{x} or @code{print}.
9170 @item @var{u}, the unit size
9171 The unit size is any of
9177 Halfwords (two bytes).
9179 Words (four bytes). This is the initial default.
9181 Giant words (eight bytes).
9184 Each time you specify a unit size with @code{x}, that size becomes the
9185 default unit the next time you use @code{x}. For the @samp{i} format,
9186 the unit size is ignored and is normally not written. For the @samp{s} format,
9187 the unit size defaults to @samp{b}, unless it is explicitly given.
9188 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
9189 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
9190 Note that the results depend on the programming language of the
9191 current compilation unit. If the language is C, the @samp{s}
9192 modifier will use the UTF-16 encoding while @samp{w} will use
9193 UTF-32. The encoding is set by the programming language and cannot
9196 @item @var{addr}, starting display address
9197 @var{addr} is the address where you want @value{GDBN} to begin displaying
9198 memory. The expression need not have a pointer value (though it may);
9199 it is always interpreted as an integer address of a byte of memory.
9200 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
9201 @var{addr} is usually just after the last address examined---but several
9202 other commands also set the default address: @code{info breakpoints} (to
9203 the address of the last breakpoint listed), @code{info line} (to the
9204 starting address of a line), and @code{print} (if you use it to display
9205 a value from memory).
9208 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
9209 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
9210 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
9211 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
9212 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
9214 Since the letters indicating unit sizes are all distinct from the
9215 letters specifying output formats, you do not have to remember whether
9216 unit size or format comes first; either order works. The output
9217 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
9218 (However, the count @var{n} must come first; @samp{wx4} does not work.)
9220 Even though the unit size @var{u} is ignored for the formats @samp{s}
9221 and @samp{i}, you might still want to use a count @var{n}; for example,
9222 @samp{3i} specifies that you want to see three machine instructions,
9223 including any operands. For convenience, especially when used with
9224 the @code{display} command, the @samp{i} format also prints branch delay
9225 slot instructions, if any, beyond the count specified, which immediately
9226 follow the last instruction that is within the count. The command
9227 @code{disassemble} gives an alternative way of inspecting machine
9228 instructions; see @ref{Machine Code,,Source and Machine Code}.
9230 All the defaults for the arguments to @code{x} are designed to make it
9231 easy to continue scanning memory with minimal specifications each time
9232 you use @code{x}. For example, after you have inspected three machine
9233 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
9234 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
9235 the repeat count @var{n} is used again; the other arguments default as
9236 for successive uses of @code{x}.
9238 When examining machine instructions, the instruction at current program
9239 counter is shown with a @code{=>} marker. For example:
9242 (@value{GDBP}) x/5i $pc-6
9243 0x804837f <main+11>: mov %esp,%ebp
9244 0x8048381 <main+13>: push %ecx
9245 0x8048382 <main+14>: sub $0x4,%esp
9246 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
9247 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
9250 @cindex @code{$_}, @code{$__}, and value history
9251 The addresses and contents printed by the @code{x} command are not saved
9252 in the value history because there is often too much of them and they
9253 would get in the way. Instead, @value{GDBN} makes these values available for
9254 subsequent use in expressions as values of the convenience variables
9255 @code{$_} and @code{$__}. After an @code{x} command, the last address
9256 examined is available for use in expressions in the convenience variable
9257 @code{$_}. The contents of that address, as examined, are available in
9258 the convenience variable @code{$__}.
9260 If the @code{x} command has a repeat count, the address and contents saved
9261 are from the last memory unit printed; this is not the same as the last
9262 address printed if several units were printed on the last line of output.
9264 @anchor{addressable memory unit}
9265 @cindex addressable memory unit
9266 Most targets have an addressable memory unit size of 8 bits. This means
9267 that to each memory address are associated 8 bits of data. Some
9268 targets, however, have other addressable memory unit sizes.
9269 Within @value{GDBN} and this document, the term
9270 @dfn{addressable memory unit} (or @dfn{memory unit} for short) is used
9271 when explicitly referring to a chunk of data of that size. The word
9272 @dfn{byte} is used to refer to a chunk of data of 8 bits, regardless of
9273 the addressable memory unit size of the target. For most systems,
9274 addressable memory unit is a synonym of byte.
9276 @cindex remote memory comparison
9277 @cindex target memory comparison
9278 @cindex verify remote memory image
9279 @cindex verify target memory image
9280 When you are debugging a program running on a remote target machine
9281 (@pxref{Remote Debugging}), you may wish to verify the program's image
9282 in the remote machine's memory against the executable file you
9283 downloaded to the target. Or, on any target, you may want to check
9284 whether the program has corrupted its own read-only sections. The
9285 @code{compare-sections} command is provided for such situations.
9288 @kindex compare-sections
9289 @item compare-sections @r{[}@var{section-name}@r{|}@code{-r}@r{]}
9290 Compare the data of a loadable section @var{section-name} in the
9291 executable file of the program being debugged with the same section in
9292 the target machine's memory, and report any mismatches. With no
9293 arguments, compares all loadable sections. With an argument of
9294 @code{-r}, compares all loadable read-only sections.
9296 Note: for remote targets, this command can be accelerated if the
9297 target supports computing the CRC checksum of a block of memory
9298 (@pxref{qCRC packet}).
9302 @section Automatic Display
9303 @cindex automatic display
9304 @cindex display of expressions
9306 If you find that you want to print the value of an expression frequently
9307 (to see how it changes), you might want to add it to the @dfn{automatic
9308 display list} so that @value{GDBN} prints its value each time your program stops.
9309 Each expression added to the list is given a number to identify it;
9310 to remove an expression from the list, you specify that number.
9311 The automatic display looks like this:
9315 3: bar[5] = (struct hack *) 0x3804
9319 This display shows item numbers, expressions and their current values. As with
9320 displays you request manually using @code{x} or @code{print}, you can
9321 specify the output format you prefer; in fact, @code{display} decides
9322 whether to use @code{print} or @code{x} depending your format
9323 specification---it uses @code{x} if you specify either the @samp{i}
9324 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
9328 @item display @var{expr}
9329 Add the expression @var{expr} to the list of expressions to display
9330 each time your program stops. @xref{Expressions, ,Expressions}.
9332 @code{display} does not repeat if you press @key{RET} again after using it.
9334 @item display/@var{fmt} @var{expr}
9335 For @var{fmt} specifying only a display format and not a size or
9336 count, add the expression @var{expr} to the auto-display list but
9337 arrange to display it each time in the specified format @var{fmt}.
9338 @xref{Output Formats,,Output Formats}.
9340 @item display/@var{fmt} @var{addr}
9341 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
9342 number of units, add the expression @var{addr} as a memory address to
9343 be examined each time your program stops. Examining means in effect
9344 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
9347 For example, @samp{display/i $pc} can be helpful, to see the machine
9348 instruction about to be executed each time execution stops (@samp{$pc}
9349 is a common name for the program counter; @pxref{Registers, ,Registers}).
9352 @kindex delete display
9354 @item undisplay @var{dnums}@dots{}
9355 @itemx delete display @var{dnums}@dots{}
9356 Remove items from the list of expressions to display. Specify the
9357 numbers of the displays that you want affected with the command
9358 argument @var{dnums}. It can be a single display number, one of the
9359 numbers shown in the first field of the @samp{info display} display;
9360 or it could be a range of display numbers, as in @code{2-4}.
9362 @code{undisplay} does not repeat if you press @key{RET} after using it.
9363 (Otherwise you would just get the error @samp{No display number @dots{}}.)
9365 @kindex disable display
9366 @item disable display @var{dnums}@dots{}
9367 Disable the display of item numbers @var{dnums}. A disabled display
9368 item is not printed automatically, but is not forgotten. It may be
9369 enabled again later. Specify the numbers of the displays that you
9370 want affected with the command argument @var{dnums}. It can be a
9371 single display number, one of the numbers shown in the first field of
9372 the @samp{info display} display; or it could be a range of display
9373 numbers, as in @code{2-4}.
9375 @kindex enable display
9376 @item enable display @var{dnums}@dots{}
9377 Enable display of item numbers @var{dnums}. It becomes effective once
9378 again in auto display of its expression, until you specify otherwise.
9379 Specify the numbers of the displays that you want affected with the
9380 command argument @var{dnums}. It can be a single display number, one
9381 of the numbers shown in the first field of the @samp{info display}
9382 display; or it could be a range of display numbers, as in @code{2-4}.
9385 Display the current values of the expressions on the list, just as is
9386 done when your program stops.
9388 @kindex info display
9390 Print the list of expressions previously set up to display
9391 automatically, each one with its item number, but without showing the
9392 values. This includes disabled expressions, which are marked as such.
9393 It also includes expressions which would not be displayed right now
9394 because they refer to automatic variables not currently available.
9397 @cindex display disabled out of scope
9398 If a display expression refers to local variables, then it does not make
9399 sense outside the lexical context for which it was set up. Such an
9400 expression is disabled when execution enters a context where one of its
9401 variables is not defined. For example, if you give the command
9402 @code{display last_char} while inside a function with an argument
9403 @code{last_char}, @value{GDBN} displays this argument while your program
9404 continues to stop inside that function. When it stops elsewhere---where
9405 there is no variable @code{last_char}---the display is disabled
9406 automatically. The next time your program stops where @code{last_char}
9407 is meaningful, you can enable the display expression once again.
9409 @node Print Settings
9410 @section Print Settings
9412 @cindex format options
9413 @cindex print settings
9414 @value{GDBN} provides the following ways to control how arrays, structures,
9415 and symbols are printed.
9418 These settings are useful for debugging programs in any language:
9422 @item set print address
9423 @itemx set print address on
9424 @cindex print/don't print memory addresses
9425 @value{GDBN} prints memory addresses showing the location of stack
9426 traces, structure values, pointer values, breakpoints, and so forth,
9427 even when it also displays the contents of those addresses. The default
9428 is @code{on}. For example, this is what a stack frame display looks like with
9429 @code{set print address on}:
9434 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
9436 530 if (lquote != def_lquote)
9440 @item set print address off
9441 Do not print addresses when displaying their contents. For example,
9442 this is the same stack frame displayed with @code{set print address off}:
9446 (@value{GDBP}) set print addr off
9448 #0 set_quotes (lq="<<", rq=">>") at input.c:530
9449 530 if (lquote != def_lquote)
9453 You can use @samp{set print address off} to eliminate all machine
9454 dependent displays from the @value{GDBN} interface. For example, with
9455 @code{print address off}, you should get the same text for backtraces on
9456 all machines---whether or not they involve pointer arguments.
9459 @item show print address
9460 Show whether or not addresses are to be printed.
9463 When @value{GDBN} prints a symbolic address, it normally prints the
9464 closest earlier symbol plus an offset. If that symbol does not uniquely
9465 identify the address (for example, it is a name whose scope is a single
9466 source file), you may need to clarify. One way to do this is with
9467 @code{info line}, for example @samp{info line *0x4537}. Alternately,
9468 you can set @value{GDBN} to print the source file and line number when
9469 it prints a symbolic address:
9472 @item set print symbol-filename on
9473 @cindex source file and line of a symbol
9474 @cindex symbol, source file and line
9475 Tell @value{GDBN} to print the source file name and line number of a
9476 symbol in the symbolic form of an address.
9478 @item set print symbol-filename off
9479 Do not print source file name and line number of a symbol. This is the
9482 @item show print symbol-filename
9483 Show whether or not @value{GDBN} will print the source file name and
9484 line number of a symbol in the symbolic form of an address.
9487 Another situation where it is helpful to show symbol filenames and line
9488 numbers is when disassembling code; @value{GDBN} shows you the line
9489 number and source file that corresponds to each instruction.
9491 Also, you may wish to see the symbolic form only if the address being
9492 printed is reasonably close to the closest earlier symbol:
9495 @item set print max-symbolic-offset @var{max-offset}
9496 @itemx set print max-symbolic-offset unlimited
9497 @cindex maximum value for offset of closest symbol
9498 Tell @value{GDBN} to only display the symbolic form of an address if the
9499 offset between the closest earlier symbol and the address is less than
9500 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
9501 to always print the symbolic form of an address if any symbol precedes
9502 it. Zero is equivalent to @code{unlimited}.
9504 @item show print max-symbolic-offset
9505 Ask how large the maximum offset is that @value{GDBN} prints in a
9509 @cindex wild pointer, interpreting
9510 @cindex pointer, finding referent
9511 If you have a pointer and you are not sure where it points, try
9512 @samp{set print symbol-filename on}. Then you can determine the name
9513 and source file location of the variable where it points, using
9514 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
9515 For example, here @value{GDBN} shows that a variable @code{ptt} points
9516 at another variable @code{t}, defined in @file{hi2.c}:
9519 (@value{GDBP}) set print symbol-filename on
9520 (@value{GDBP}) p/a ptt
9521 $4 = 0xe008 <t in hi2.c>
9525 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
9526 does not show the symbol name and filename of the referent, even with
9527 the appropriate @code{set print} options turned on.
9530 You can also enable @samp{/a}-like formatting all the time using
9531 @samp{set print symbol on}:
9534 @item set print symbol on
9535 Tell @value{GDBN} to print the symbol corresponding to an address, if
9538 @item set print symbol off
9539 Tell @value{GDBN} not to print the symbol corresponding to an
9540 address. In this mode, @value{GDBN} will still print the symbol
9541 corresponding to pointers to functions. This is the default.
9543 @item show print symbol
9544 Show whether @value{GDBN} will display the symbol corresponding to an
9548 Other settings control how different kinds of objects are printed:
9551 @item set print array
9552 @itemx set print array on
9553 @cindex pretty print arrays
9554 Pretty print arrays. This format is more convenient to read,
9555 but uses more space. The default is off.
9557 @item set print array off
9558 Return to compressed format for arrays.
9560 @item show print array
9561 Show whether compressed or pretty format is selected for displaying
9564 @cindex print array indexes
9565 @item set print array-indexes
9566 @itemx set print array-indexes on
9567 Print the index of each element when displaying arrays. May be more
9568 convenient to locate a given element in the array or quickly find the
9569 index of a given element in that printed array. The default is off.
9571 @item set print array-indexes off
9572 Stop printing element indexes when displaying arrays.
9574 @item show print array-indexes
9575 Show whether the index of each element is printed when displaying
9578 @item set print elements @var{number-of-elements}
9579 @itemx set print elements unlimited
9580 @cindex number of array elements to print
9581 @cindex limit on number of printed array elements
9582 Set a limit on how many elements of an array @value{GDBN} will print.
9583 If @value{GDBN} is printing a large array, it stops printing after it has
9584 printed the number of elements set by the @code{set print elements} command.
9585 This limit also applies to the display of strings.
9586 When @value{GDBN} starts, this limit is set to 200.
9587 Setting @var{number-of-elements} to @code{unlimited} or zero means
9588 that the number of elements to print is unlimited.
9590 @item show print elements
9591 Display the number of elements of a large array that @value{GDBN} will print.
9592 If the number is 0, then the printing is unlimited.
9594 @item set print frame-arguments @var{value}
9595 @kindex set print frame-arguments
9596 @cindex printing frame argument values
9597 @cindex print all frame argument values
9598 @cindex print frame argument values for scalars only
9599 @cindex do not print frame argument values
9600 This command allows to control how the values of arguments are printed
9601 when the debugger prints a frame (@pxref{Frames}). The possible
9606 The values of all arguments are printed.
9609 Print the value of an argument only if it is a scalar. The value of more
9610 complex arguments such as arrays, structures, unions, etc, is replaced
9611 by @code{@dots{}}. This is the default. Here is an example where
9612 only scalar arguments are shown:
9615 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9620 None of the argument values are printed. Instead, the value of each argument
9621 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9624 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9629 By default, only scalar arguments are printed. This command can be used
9630 to configure the debugger to print the value of all arguments, regardless
9631 of their type. However, it is often advantageous to not print the value
9632 of more complex parameters. For instance, it reduces the amount of
9633 information printed in each frame, making the backtrace more readable.
9634 Also, it improves performance when displaying Ada frames, because
9635 the computation of large arguments can sometimes be CPU-intensive,
9636 especially in large applications. Setting @code{print frame-arguments}
9637 to @code{scalars} (the default) or @code{none} avoids this computation,
9638 thus speeding up the display of each Ada frame.
9640 @item show print frame-arguments
9641 Show how the value of arguments should be displayed when printing a frame.
9643 @item set print raw frame-arguments on
9644 Print frame arguments in raw, non pretty-printed, form.
9646 @item set print raw frame-arguments off
9647 Print frame arguments in pretty-printed form, if there is a pretty-printer
9648 for the value (@pxref{Pretty Printing}),
9649 otherwise print the value in raw form.
9650 This is the default.
9652 @item show print raw frame-arguments
9653 Show whether to print frame arguments in raw form.
9655 @anchor{set print entry-values}
9656 @item set print entry-values @var{value}
9657 @kindex set print entry-values
9658 Set printing of frame argument values at function entry. In some cases
9659 @value{GDBN} can determine the value of function argument which was passed by
9660 the function caller, even if the value was modified inside the called function
9661 and therefore is different. With optimized code, the current value could be
9662 unavailable, but the entry value may still be known.
9664 The default value is @code{default} (see below for its description). Older
9665 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9666 this feature will behave in the @code{default} setting the same way as with the
9669 This functionality is currently supported only by DWARF 2 debugging format and
9670 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9671 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9674 The @var{value} parameter can be one of the following:
9678 Print only actual parameter values, never print values from function entry
9682 #0 different (val=6)
9683 #0 lost (val=<optimized out>)
9685 #0 invalid (val=<optimized out>)
9689 Print only parameter values from function entry point. The actual parameter
9690 values are never printed.
9692 #0 equal (val@@entry=5)
9693 #0 different (val@@entry=5)
9694 #0 lost (val@@entry=5)
9695 #0 born (val@@entry=<optimized out>)
9696 #0 invalid (val@@entry=<optimized out>)
9700 Print only parameter values from function entry point. If value from function
9701 entry point is not known while the actual value is known, print the actual
9702 value for such parameter.
9704 #0 equal (val@@entry=5)
9705 #0 different (val@@entry=5)
9706 #0 lost (val@@entry=5)
9708 #0 invalid (val@@entry=<optimized out>)
9712 Print actual parameter values. If actual parameter value is not known while
9713 value from function entry point is known, print the entry point value for such
9717 #0 different (val=6)
9718 #0 lost (val@@entry=5)
9720 #0 invalid (val=<optimized out>)
9724 Always print both the actual parameter value and its value from function entry
9725 point, even if values of one or both are not available due to compiler
9728 #0 equal (val=5, val@@entry=5)
9729 #0 different (val=6, val@@entry=5)
9730 #0 lost (val=<optimized out>, val@@entry=5)
9731 #0 born (val=10, val@@entry=<optimized out>)
9732 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9736 Print the actual parameter value if it is known and also its value from
9737 function entry point if it is known. If neither is known, print for the actual
9738 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9739 values are known and identical, print the shortened
9740 @code{param=param@@entry=VALUE} notation.
9742 #0 equal (val=val@@entry=5)
9743 #0 different (val=6, val@@entry=5)
9744 #0 lost (val@@entry=5)
9746 #0 invalid (val=<optimized out>)
9750 Always print the actual parameter value. Print also its value from function
9751 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9752 if both values are known and identical, print the shortened
9753 @code{param=param@@entry=VALUE} notation.
9755 #0 equal (val=val@@entry=5)
9756 #0 different (val=6, val@@entry=5)
9757 #0 lost (val=<optimized out>, val@@entry=5)
9759 #0 invalid (val=<optimized out>)
9763 For analysis messages on possible failures of frame argument values at function
9764 entry resolution see @ref{set debug entry-values}.
9766 @item show print entry-values
9767 Show the method being used for printing of frame argument values at function
9770 @item set print repeats @var{number-of-repeats}
9771 @itemx set print repeats unlimited
9772 @cindex repeated array elements
9773 Set the threshold for suppressing display of repeated array
9774 elements. When the number of consecutive identical elements of an
9775 array exceeds the threshold, @value{GDBN} prints the string
9776 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9777 identical repetitions, instead of displaying the identical elements
9778 themselves. Setting the threshold to @code{unlimited} or zero will
9779 cause all elements to be individually printed. The default threshold
9782 @item show print repeats
9783 Display the current threshold for printing repeated identical
9786 @item set print null-stop
9787 @cindex @sc{null} elements in arrays
9788 Cause @value{GDBN} to stop printing the characters of an array when the first
9789 @sc{null} is encountered. This is useful when large arrays actually
9790 contain only short strings.
9793 @item show print null-stop
9794 Show whether @value{GDBN} stops printing an array on the first
9795 @sc{null} character.
9797 @item set print pretty on
9798 @cindex print structures in indented form
9799 @cindex indentation in structure display
9800 Cause @value{GDBN} to print structures in an indented format with one member
9801 per line, like this:
9816 @item set print pretty off
9817 Cause @value{GDBN} to print structures in a compact format, like this:
9821 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9822 meat = 0x54 "Pork"@}
9827 This is the default format.
9829 @item show print pretty
9830 Show which format @value{GDBN} is using to print structures.
9832 @item set print sevenbit-strings on
9833 @cindex eight-bit characters in strings
9834 @cindex octal escapes in strings
9835 Print using only seven-bit characters; if this option is set,
9836 @value{GDBN} displays any eight-bit characters (in strings or
9837 character values) using the notation @code{\}@var{nnn}. This setting is
9838 best if you are working in English (@sc{ascii}) and you use the
9839 high-order bit of characters as a marker or ``meta'' bit.
9841 @item set print sevenbit-strings off
9842 Print full eight-bit characters. This allows the use of more
9843 international character sets, and is the default.
9845 @item show print sevenbit-strings
9846 Show whether or not @value{GDBN} is printing only seven-bit characters.
9848 @item set print union on
9849 @cindex unions in structures, printing
9850 Tell @value{GDBN} to print unions which are contained in structures
9851 and other unions. This is the default setting.
9853 @item set print union off
9854 Tell @value{GDBN} not to print unions which are contained in
9855 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9858 @item show print union
9859 Ask @value{GDBN} whether or not it will print unions which are contained in
9860 structures and other unions.
9862 For example, given the declarations
9865 typedef enum @{Tree, Bug@} Species;
9866 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9867 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9878 struct thing foo = @{Tree, @{Acorn@}@};
9882 with @code{set print union on} in effect @samp{p foo} would print
9885 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9889 and with @code{set print union off} in effect it would print
9892 $1 = @{it = Tree, form = @{...@}@}
9896 @code{set print union} affects programs written in C-like languages
9902 These settings are of interest when debugging C@t{++} programs:
9905 @cindex demangling C@t{++} names
9906 @item set print demangle
9907 @itemx set print demangle on
9908 Print C@t{++} names in their source form rather than in the encoded
9909 (``mangled'') form passed to the assembler and linker for type-safe
9910 linkage. The default is on.
9912 @item show print demangle
9913 Show whether C@t{++} names are printed in mangled or demangled form.
9915 @item set print asm-demangle
9916 @itemx set print asm-demangle on
9917 Print C@t{++} names in their source form rather than their mangled form, even
9918 in assembler code printouts such as instruction disassemblies.
9921 @item show print asm-demangle
9922 Show whether C@t{++} names in assembly listings are printed in mangled
9925 @cindex C@t{++} symbol decoding style
9926 @cindex symbol decoding style, C@t{++}
9927 @kindex set demangle-style
9928 @item set demangle-style @var{style}
9929 Choose among several encoding schemes used by different compilers to
9930 represent C@t{++} names. The choices for @var{style} are currently:
9934 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9935 This is the default.
9938 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9941 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9944 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9947 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9948 @strong{Warning:} this setting alone is not sufficient to allow
9949 debugging @code{cfront}-generated executables. @value{GDBN} would
9950 require further enhancement to permit that.
9953 If you omit @var{style}, you will see a list of possible formats.
9955 @item show demangle-style
9956 Display the encoding style currently in use for decoding C@t{++} symbols.
9958 @item set print object
9959 @itemx set print object on
9960 @cindex derived type of an object, printing
9961 @cindex display derived types
9962 When displaying a pointer to an object, identify the @emph{actual}
9963 (derived) type of the object rather than the @emph{declared} type, using
9964 the virtual function table. Note that the virtual function table is
9965 required---this feature can only work for objects that have run-time
9966 type identification; a single virtual method in the object's declared
9967 type is sufficient. Note that this setting is also taken into account when
9968 working with variable objects via MI (@pxref{GDB/MI}).
9970 @item set print object off
9971 Display only the declared type of objects, without reference to the
9972 virtual function table. This is the default setting.
9974 @item show print object
9975 Show whether actual, or declared, object types are displayed.
9977 @item set print static-members
9978 @itemx set print static-members on
9979 @cindex static members of C@t{++} objects
9980 Print static members when displaying a C@t{++} object. The default is on.
9982 @item set print static-members off
9983 Do not print static members when displaying a C@t{++} object.
9985 @item show print static-members
9986 Show whether C@t{++} static members are printed or not.
9988 @item set print pascal_static-members
9989 @itemx set print pascal_static-members on
9990 @cindex static members of Pascal objects
9991 @cindex Pascal objects, static members display
9992 Print static members when displaying a Pascal object. The default is on.
9994 @item set print pascal_static-members off
9995 Do not print static members when displaying a Pascal object.
9997 @item show print pascal_static-members
9998 Show whether Pascal static members are printed or not.
10000 @c These don't work with HP ANSI C++ yet.
10001 @item set print vtbl
10002 @itemx set print vtbl on
10003 @cindex pretty print C@t{++} virtual function tables
10004 @cindex virtual functions (C@t{++}) display
10005 @cindex VTBL display
10006 Pretty print C@t{++} virtual function tables. The default is off.
10007 (The @code{vtbl} commands do not work on programs compiled with the HP
10008 ANSI C@t{++} compiler (@code{aCC}).)
10010 @item set print vtbl off
10011 Do not pretty print C@t{++} virtual function tables.
10013 @item show print vtbl
10014 Show whether C@t{++} virtual function tables are pretty printed, or not.
10017 @node Pretty Printing
10018 @section Pretty Printing
10020 @value{GDBN} provides a mechanism to allow pretty-printing of values using
10021 Python code. It greatly simplifies the display of complex objects. This
10022 mechanism works for both MI and the CLI.
10025 * Pretty-Printer Introduction:: Introduction to pretty-printers
10026 * Pretty-Printer Example:: An example pretty-printer
10027 * Pretty-Printer Commands:: Pretty-printer commands
10030 @node Pretty-Printer Introduction
10031 @subsection Pretty-Printer Introduction
10033 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
10034 registered for the value. If there is then @value{GDBN} invokes the
10035 pretty-printer to print the value. Otherwise the value is printed normally.
10037 Pretty-printers are normally named. This makes them easy to manage.
10038 The @samp{info pretty-printer} command will list all the installed
10039 pretty-printers with their names.
10040 If a pretty-printer can handle multiple data types, then its
10041 @dfn{subprinters} are the printers for the individual data types.
10042 Each such subprinter has its own name.
10043 The format of the name is @var{printer-name};@var{subprinter-name}.
10045 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
10046 Typically they are automatically loaded and registered when the corresponding
10047 debug information is loaded, thus making them available without having to
10048 do anything special.
10050 There are three places where a pretty-printer can be registered.
10054 Pretty-printers registered globally are available when debugging
10058 Pretty-printers registered with a program space are available only
10059 when debugging that program.
10060 @xref{Progspaces In Python}, for more details on program spaces in Python.
10063 Pretty-printers registered with an objfile are loaded and unloaded
10064 with the corresponding objfile (e.g., shared library).
10065 @xref{Objfiles In Python}, for more details on objfiles in Python.
10068 @xref{Selecting Pretty-Printers}, for further information on how
10069 pretty-printers are selected,
10071 @xref{Writing a Pretty-Printer}, for implementing pretty printers
10074 @node Pretty-Printer Example
10075 @subsection Pretty-Printer Example
10077 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
10080 (@value{GDBP}) print s
10082 static npos = 4294967295,
10084 <std::allocator<char>> = @{
10085 <__gnu_cxx::new_allocator<char>> = @{
10086 <No data fields>@}, <No data fields>
10088 members of std::basic_string<char, std::char_traits<char>,
10089 std::allocator<char> >::_Alloc_hider:
10090 _M_p = 0x804a014 "abcd"
10095 With a pretty-printer for @code{std::string} only the contents are printed:
10098 (@value{GDBP}) print s
10102 @node Pretty-Printer Commands
10103 @subsection Pretty-Printer Commands
10104 @cindex pretty-printer commands
10107 @kindex info pretty-printer
10108 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10109 Print the list of installed pretty-printers.
10110 This includes disabled pretty-printers, which are marked as such.
10112 @var{object-regexp} is a regular expression matching the objects
10113 whose pretty-printers to list.
10114 Objects can be @code{global}, the program space's file
10115 (@pxref{Progspaces In Python}),
10116 and the object files within that program space (@pxref{Objfiles In Python}).
10117 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
10118 looks up a printer from these three objects.
10120 @var{name-regexp} is a regular expression matching the name of the printers
10123 @kindex disable pretty-printer
10124 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10125 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10126 A disabled pretty-printer is not forgotten, it may be enabled again later.
10128 @kindex enable pretty-printer
10129 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
10130 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
10135 Suppose we have three pretty-printers installed: one from library1.so
10136 named @code{foo} that prints objects of type @code{foo}, and
10137 another from library2.so named @code{bar} that prints two types of objects,
10138 @code{bar1} and @code{bar2}.
10141 (gdb) info pretty-printer
10148 (gdb) info pretty-printer library2
10153 (gdb) disable pretty-printer library1
10155 2 of 3 printers enabled
10156 (gdb) info pretty-printer
10163 (gdb) disable pretty-printer library2 bar:bar1
10165 1 of 3 printers enabled
10166 (gdb) info pretty-printer library2
10173 (gdb) disable pretty-printer library2 bar
10175 0 of 3 printers enabled
10176 (gdb) info pretty-printer library2
10185 Note that for @code{bar} the entire printer can be disabled,
10186 as can each individual subprinter.
10188 @node Value History
10189 @section Value History
10191 @cindex value history
10192 @cindex history of values printed by @value{GDBN}
10193 Values printed by the @code{print} command are saved in the @value{GDBN}
10194 @dfn{value history}. This allows you to refer to them in other expressions.
10195 Values are kept until the symbol table is re-read or discarded
10196 (for example with the @code{file} or @code{symbol-file} commands).
10197 When the symbol table changes, the value history is discarded,
10198 since the values may contain pointers back to the types defined in the
10203 @cindex history number
10204 The values printed are given @dfn{history numbers} by which you can
10205 refer to them. These are successive integers starting with one.
10206 @code{print} shows you the history number assigned to a value by
10207 printing @samp{$@var{num} = } before the value; here @var{num} is the
10210 To refer to any previous value, use @samp{$} followed by the value's
10211 history number. The way @code{print} labels its output is designed to
10212 remind you of this. Just @code{$} refers to the most recent value in
10213 the history, and @code{$$} refers to the value before that.
10214 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
10215 is the value just prior to @code{$$}, @code{$$1} is equivalent to
10216 @code{$$}, and @code{$$0} is equivalent to @code{$}.
10218 For example, suppose you have just printed a pointer to a structure and
10219 want to see the contents of the structure. It suffices to type
10225 If you have a chain of structures where the component @code{next} points
10226 to the next one, you can print the contents of the next one with this:
10233 You can print successive links in the chain by repeating this
10234 command---which you can do by just typing @key{RET}.
10236 Note that the history records values, not expressions. If the value of
10237 @code{x} is 4 and you type these commands:
10245 then the value recorded in the value history by the @code{print} command
10246 remains 4 even though the value of @code{x} has changed.
10249 @kindex show values
10251 Print the last ten values in the value history, with their item numbers.
10252 This is like @samp{p@ $$9} repeated ten times, except that @code{show
10253 values} does not change the history.
10255 @item show values @var{n}
10256 Print ten history values centered on history item number @var{n}.
10258 @item show values +
10259 Print ten history values just after the values last printed. If no more
10260 values are available, @code{show values +} produces no display.
10263 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
10264 same effect as @samp{show values +}.
10266 @node Convenience Vars
10267 @section Convenience Variables
10269 @cindex convenience variables
10270 @cindex user-defined variables
10271 @value{GDBN} provides @dfn{convenience variables} that you can use within
10272 @value{GDBN} to hold on to a value and refer to it later. These variables
10273 exist entirely within @value{GDBN}; they are not part of your program, and
10274 setting a convenience variable has no direct effect on further execution
10275 of your program. That is why you can use them freely.
10277 Convenience variables are prefixed with @samp{$}. Any name preceded by
10278 @samp{$} can be used for a convenience variable, unless it is one of
10279 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
10280 (Value history references, in contrast, are @emph{numbers} preceded
10281 by @samp{$}. @xref{Value History, ,Value History}.)
10283 You can save a value in a convenience variable with an assignment
10284 expression, just as you would set a variable in your program.
10288 set $foo = *object_ptr
10292 would save in @code{$foo} the value contained in the object pointed to by
10295 Using a convenience variable for the first time creates it, but its
10296 value is @code{void} until you assign a new value. You can alter the
10297 value with another assignment at any time.
10299 Convenience variables have no fixed types. You can assign a convenience
10300 variable any type of value, including structures and arrays, even if
10301 that variable already has a value of a different type. The convenience
10302 variable, when used as an expression, has the type of its current value.
10305 @kindex show convenience
10306 @cindex show all user variables and functions
10307 @item show convenience
10308 Print a list of convenience variables used so far, and their values,
10309 as well as a list of the convenience functions.
10310 Abbreviated @code{show conv}.
10312 @kindex init-if-undefined
10313 @cindex convenience variables, initializing
10314 @item init-if-undefined $@var{variable} = @var{expression}
10315 Set a convenience variable if it has not already been set. This is useful
10316 for user-defined commands that keep some state. It is similar, in concept,
10317 to using local static variables with initializers in C (except that
10318 convenience variables are global). It can also be used to allow users to
10319 override default values used in a command script.
10321 If the variable is already defined then the expression is not evaluated so
10322 any side-effects do not occur.
10325 One of the ways to use a convenience variable is as a counter to be
10326 incremented or a pointer to be advanced. For example, to print
10327 a field from successive elements of an array of structures:
10331 print bar[$i++]->contents
10335 Repeat that command by typing @key{RET}.
10337 Some convenience variables are created automatically by @value{GDBN} and given
10338 values likely to be useful.
10341 @vindex $_@r{, convenience variable}
10343 The variable @code{$_} is automatically set by the @code{x} command to
10344 the last address examined (@pxref{Memory, ,Examining Memory}). Other
10345 commands which provide a default address for @code{x} to examine also
10346 set @code{$_} to that address; these commands include @code{info line}
10347 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
10348 except when set by the @code{x} command, in which case it is a pointer
10349 to the type of @code{$__}.
10351 @vindex $__@r{, convenience variable}
10353 The variable @code{$__} is automatically set by the @code{x} command
10354 to the value found in the last address examined. Its type is chosen
10355 to match the format in which the data was printed.
10358 @vindex $_exitcode@r{, convenience variable}
10359 When the program being debugged terminates normally, @value{GDBN}
10360 automatically sets this variable to the exit code of the program, and
10361 resets @code{$_exitsignal} to @code{void}.
10364 @vindex $_exitsignal@r{, convenience variable}
10365 When the program being debugged dies due to an uncaught signal,
10366 @value{GDBN} automatically sets this variable to that signal's number,
10367 and resets @code{$_exitcode} to @code{void}.
10369 To distinguish between whether the program being debugged has exited
10370 (i.e., @code{$_exitcode} is not @code{void}) or signalled (i.e.,
10371 @code{$_exitsignal} is not @code{void}), the convenience function
10372 @code{$_isvoid} can be used (@pxref{Convenience Funs,, Convenience
10373 Functions}). For example, considering the following source code:
10376 #include <signal.h>
10379 main (int argc, char *argv[])
10386 A valid way of telling whether the program being debugged has exited
10387 or signalled would be:
10390 (@value{GDBP}) define has_exited_or_signalled
10391 Type commands for definition of ``has_exited_or_signalled''.
10392 End with a line saying just ``end''.
10393 >if $_isvoid ($_exitsignal)
10394 >echo The program has exited\n
10396 >echo The program has signalled\n
10402 Program terminated with signal SIGALRM, Alarm clock.
10403 The program no longer exists.
10404 (@value{GDBP}) has_exited_or_signalled
10405 The program has signalled
10408 As can be seen, @value{GDBN} correctly informs that the program being
10409 debugged has signalled, since it calls @code{raise} and raises a
10410 @code{SIGALRM} signal. If the program being debugged had not called
10411 @code{raise}, then @value{GDBN} would report a normal exit:
10414 (@value{GDBP}) has_exited_or_signalled
10415 The program has exited
10419 The variable @code{$_exception} is set to the exception object being
10420 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
10423 @itemx $_probe_arg0@dots{}$_probe_arg11
10424 Arguments to a static probe. @xref{Static Probe Points}.
10427 @vindex $_sdata@r{, inspect, convenience variable}
10428 The variable @code{$_sdata} contains extra collected static tracepoint
10429 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
10430 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
10431 if extra static tracepoint data has not been collected.
10434 @vindex $_siginfo@r{, convenience variable}
10435 The variable @code{$_siginfo} contains extra signal information
10436 (@pxref{extra signal information}). Note that @code{$_siginfo}
10437 could be empty, if the application has not yet received any signals.
10438 For example, it will be empty before you execute the @code{run} command.
10441 @vindex $_tlb@r{, convenience variable}
10442 The variable @code{$_tlb} is automatically set when debugging
10443 applications running on MS-Windows in native mode or connected to
10444 gdbserver that supports the @code{qGetTIBAddr} request.
10445 @xref{General Query Packets}.
10446 This variable contains the address of the thread information block.
10449 The number of the current inferior. @xref{Inferiors and
10450 Programs, ,Debugging Multiple Inferiors and Programs}.
10453 The thread number of the current thread. @xref{thread numbers}.
10457 @node Convenience Funs
10458 @section Convenience Functions
10460 @cindex convenience functions
10461 @value{GDBN} also supplies some @dfn{convenience functions}. These
10462 have a syntax similar to convenience variables. A convenience
10463 function can be used in an expression just like an ordinary function;
10464 however, a convenience function is implemented internally to
10467 These functions do not require @value{GDBN} to be configured with
10468 @code{Python} support, which means that they are always available.
10472 @item $_isvoid (@var{expr})
10473 @findex $_isvoid@r{, convenience function}
10474 Return one if the expression @var{expr} is @code{void}. Otherwise it
10477 A @code{void} expression is an expression where the type of the result
10478 is @code{void}. For example, you can examine a convenience variable
10479 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
10483 (@value{GDBP}) print $_exitcode
10485 (@value{GDBP}) print $_isvoid ($_exitcode)
10488 Starting program: ./a.out
10489 [Inferior 1 (process 29572) exited normally]
10490 (@value{GDBP}) print $_exitcode
10492 (@value{GDBP}) print $_isvoid ($_exitcode)
10496 In the example above, we used @code{$_isvoid} to check whether
10497 @code{$_exitcode} is @code{void} before and after the execution of the
10498 program being debugged. Before the execution there is no exit code to
10499 be examined, therefore @code{$_exitcode} is @code{void}. After the
10500 execution the program being debugged returned zero, therefore
10501 @code{$_exitcode} is zero, which means that it is not @code{void}
10504 The @code{void} expression can also be a call of a function from the
10505 program being debugged. For example, given the following function:
10514 The result of calling it inside @value{GDBN} is @code{void}:
10517 (@value{GDBP}) print foo ()
10519 (@value{GDBP}) print $_isvoid (foo ())
10521 (@value{GDBP}) set $v = foo ()
10522 (@value{GDBP}) print $v
10524 (@value{GDBP}) print $_isvoid ($v)
10530 These functions require @value{GDBN} to be configured with
10531 @code{Python} support.
10535 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
10536 @findex $_memeq@r{, convenience function}
10537 Returns one if the @var{length} bytes at the addresses given by
10538 @var{buf1} and @var{buf2} are equal.
10539 Otherwise it returns zero.
10541 @item $_regex(@var{str}, @var{regex})
10542 @findex $_regex@r{, convenience function}
10543 Returns one if the string @var{str} matches the regular expression
10544 @var{regex}. Otherwise it returns zero.
10545 The syntax of the regular expression is that specified by @code{Python}'s
10546 regular expression support.
10548 @item $_streq(@var{str1}, @var{str2})
10549 @findex $_streq@r{, convenience function}
10550 Returns one if the strings @var{str1} and @var{str2} are equal.
10551 Otherwise it returns zero.
10553 @item $_strlen(@var{str})
10554 @findex $_strlen@r{, convenience function}
10555 Returns the length of string @var{str}.
10557 @item $_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10558 @findex $_caller_is@r{, convenience function}
10559 Returns one if the calling function's name is equal to @var{name}.
10560 Otherwise it returns zero.
10562 If the optional argument @var{number_of_frames} is provided,
10563 it is the number of frames up in the stack to look.
10571 at testsuite/gdb.python/py-caller-is.c:21
10572 #1 0x00000000004005a0 in middle_func ()
10573 at testsuite/gdb.python/py-caller-is.c:27
10574 #2 0x00000000004005ab in top_func ()
10575 at testsuite/gdb.python/py-caller-is.c:33
10576 #3 0x00000000004005b6 in main ()
10577 at testsuite/gdb.python/py-caller-is.c:39
10578 (gdb) print $_caller_is ("middle_func")
10580 (gdb) print $_caller_is ("top_func", 2)
10584 @item $_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10585 @findex $_caller_matches@r{, convenience function}
10586 Returns one if the calling function's name matches the regular expression
10587 @var{regexp}. Otherwise it returns zero.
10589 If the optional argument @var{number_of_frames} is provided,
10590 it is the number of frames up in the stack to look.
10593 @item $_any_caller_is(@var{name}@r{[}, @var{number_of_frames}@r{]})
10594 @findex $_any_caller_is@r{, convenience function}
10595 Returns one if any calling function's name is equal to @var{name}.
10596 Otherwise it returns zero.
10598 If the optional argument @var{number_of_frames} is provided,
10599 it is the number of frames up in the stack to look.
10602 This function differs from @code{$_caller_is} in that this function
10603 checks all stack frames from the immediate caller to the frame specified
10604 by @var{number_of_frames}, whereas @code{$_caller_is} only checks the
10605 frame specified by @var{number_of_frames}.
10607 @item $_any_caller_matches(@var{regexp}@r{[}, @var{number_of_frames}@r{]})
10608 @findex $_any_caller_matches@r{, convenience function}
10609 Returns one if any calling function's name matches the regular expression
10610 @var{regexp}. Otherwise it returns zero.
10612 If the optional argument @var{number_of_frames} is provided,
10613 it is the number of frames up in the stack to look.
10616 This function differs from @code{$_caller_matches} in that this function
10617 checks all stack frames from the immediate caller to the frame specified
10618 by @var{number_of_frames}, whereas @code{$_caller_matches} only checks the
10619 frame specified by @var{number_of_frames}.
10623 @value{GDBN} provides the ability to list and get help on
10624 convenience functions.
10627 @item help function
10628 @kindex help function
10629 @cindex show all convenience functions
10630 Print a list of all convenience functions.
10637 You can refer to machine register contents, in expressions, as variables
10638 with names starting with @samp{$}. The names of registers are different
10639 for each machine; use @code{info registers} to see the names used on
10643 @kindex info registers
10644 @item info registers
10645 Print the names and values of all registers except floating-point
10646 and vector registers (in the selected stack frame).
10648 @kindex info all-registers
10649 @cindex floating point registers
10650 @item info all-registers
10651 Print the names and values of all registers, including floating-point
10652 and vector registers (in the selected stack frame).
10654 @item info registers @var{regname} @dots{}
10655 Print the @dfn{relativized} value of each specified register @var{regname}.
10656 As discussed in detail below, register values are normally relative to
10657 the selected stack frame. The @var{regname} may be any register name valid on
10658 the machine you are using, with or without the initial @samp{$}.
10661 @anchor{standard registers}
10662 @cindex stack pointer register
10663 @cindex program counter register
10664 @cindex process status register
10665 @cindex frame pointer register
10666 @cindex standard registers
10667 @value{GDBN} has four ``standard'' register names that are available (in
10668 expressions) on most machines---whenever they do not conflict with an
10669 architecture's canonical mnemonics for registers. The register names
10670 @code{$pc} and @code{$sp} are used for the program counter register and
10671 the stack pointer. @code{$fp} is used for a register that contains a
10672 pointer to the current stack frame, and @code{$ps} is used for a
10673 register that contains the processor status. For example,
10674 you could print the program counter in hex with
10681 or print the instruction to be executed next with
10688 or add four to the stack pointer@footnote{This is a way of removing
10689 one word from the stack, on machines where stacks grow downward in
10690 memory (most machines, nowadays). This assumes that the innermost
10691 stack frame is selected; setting @code{$sp} is not allowed when other
10692 stack frames are selected. To pop entire frames off the stack,
10693 regardless of machine architecture, use @code{return};
10694 see @ref{Returning, ,Returning from a Function}.} with
10700 Whenever possible, these four standard register names are available on
10701 your machine even though the machine has different canonical mnemonics,
10702 so long as there is no conflict. The @code{info registers} command
10703 shows the canonical names. For example, on the SPARC, @code{info
10704 registers} displays the processor status register as @code{$psr} but you
10705 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
10706 is an alias for the @sc{eflags} register.
10708 @value{GDBN} always considers the contents of an ordinary register as an
10709 integer when the register is examined in this way. Some machines have
10710 special registers which can hold nothing but floating point; these
10711 registers are considered to have floating point values. There is no way
10712 to refer to the contents of an ordinary register as floating point value
10713 (although you can @emph{print} it as a floating point value with
10714 @samp{print/f $@var{regname}}).
10716 Some registers have distinct ``raw'' and ``virtual'' data formats. This
10717 means that the data format in which the register contents are saved by
10718 the operating system is not the same one that your program normally
10719 sees. For example, the registers of the 68881 floating point
10720 coprocessor are always saved in ``extended'' (raw) format, but all C
10721 programs expect to work with ``double'' (virtual) format. In such
10722 cases, @value{GDBN} normally works with the virtual format only (the format
10723 that makes sense for your program), but the @code{info registers} command
10724 prints the data in both formats.
10726 @cindex SSE registers (x86)
10727 @cindex MMX registers (x86)
10728 Some machines have special registers whose contents can be interpreted
10729 in several different ways. For example, modern x86-based machines
10730 have SSE and MMX registers that can hold several values packed
10731 together in several different formats. @value{GDBN} refers to such
10732 registers in @code{struct} notation:
10735 (@value{GDBP}) print $xmm1
10737 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10738 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10739 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10740 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10741 v4_int32 = @{0, 20657912, 11, 13@},
10742 v2_int64 = @{88725056443645952, 55834574859@},
10743 uint128 = 0x0000000d0000000b013b36f800000000
10748 To set values of such registers, you need to tell @value{GDBN} which
10749 view of the register you wish to change, as if you were assigning
10750 value to a @code{struct} member:
10753 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10756 Normally, register values are relative to the selected stack frame
10757 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10758 value that the register would contain if all stack frames farther in
10759 were exited and their saved registers restored. In order to see the
10760 true contents of hardware registers, you must select the innermost
10761 frame (with @samp{frame 0}).
10763 @cindex caller-saved registers
10764 @cindex call-clobbered registers
10765 @cindex volatile registers
10766 @cindex <not saved> values
10767 Usually ABIs reserve some registers as not needed to be saved by the
10768 callee (a.k.a.: ``caller-saved'', ``call-clobbered'' or ``volatile''
10769 registers). It may therefore not be possible for @value{GDBN} to know
10770 the value a register had before the call (in other words, in the outer
10771 frame), if the register value has since been changed by the callee.
10772 @value{GDBN} tries to deduce where the inner frame saved
10773 (``callee-saved'') registers, from the debug info, unwind info, or the
10774 machine code generated by your compiler. If some register is not
10775 saved, and @value{GDBN} knows the register is ``caller-saved'' (via
10776 its own knowledge of the ABI, or because the debug/unwind info
10777 explicitly says the register's value is undefined), @value{GDBN}
10778 displays @w{@samp{<not saved>}} as the register's value. With targets
10779 that @value{GDBN} has no knowledge of the register saving convention,
10780 if a register was not saved by the callee, then its value and location
10781 in the outer frame are assumed to be the same of the inner frame.
10782 This is usually harmless, because if the register is call-clobbered,
10783 the caller either does not care what is in the register after the
10784 call, or has code to restore the value that it does care about. Note,
10785 however, that if you change such a register in the outer frame, you
10786 may also be affecting the inner frame. Also, the more ``outer'' the
10787 frame is you're looking at, the more likely a call-clobbered
10788 register's value is to be wrong, in the sense that it doesn't actually
10789 represent the value the register had just before the call.
10791 @node Floating Point Hardware
10792 @section Floating Point Hardware
10793 @cindex floating point
10795 Depending on the configuration, @value{GDBN} may be able to give
10796 you more information about the status of the floating point hardware.
10801 Display hardware-dependent information about the floating
10802 point unit. The exact contents and layout vary depending on the
10803 floating point chip. Currently, @samp{info float} is supported on
10804 the ARM and x86 machines.
10808 @section Vector Unit
10809 @cindex vector unit
10811 Depending on the configuration, @value{GDBN} may be able to give you
10812 more information about the status of the vector unit.
10815 @kindex info vector
10817 Display information about the vector unit. The exact contents and
10818 layout vary depending on the hardware.
10821 @node OS Information
10822 @section Operating System Auxiliary Information
10823 @cindex OS information
10825 @value{GDBN} provides interfaces to useful OS facilities that can help
10826 you debug your program.
10828 @cindex auxiliary vector
10829 @cindex vector, auxiliary
10830 Some operating systems supply an @dfn{auxiliary vector} to programs at
10831 startup. This is akin to the arguments and environment that you
10832 specify for a program, but contains a system-dependent variety of
10833 binary values that tell system libraries important details about the
10834 hardware, operating system, and process. Each value's purpose is
10835 identified by an integer tag; the meanings are well-known but system-specific.
10836 Depending on the configuration and operating system facilities,
10837 @value{GDBN} may be able to show you this information. For remote
10838 targets, this functionality may further depend on the remote stub's
10839 support of the @samp{qXfer:auxv:read} packet, see
10840 @ref{qXfer auxiliary vector read}.
10845 Display the auxiliary vector of the inferior, which can be either a
10846 live process or a core dump file. @value{GDBN} prints each tag value
10847 numerically, and also shows names and text descriptions for recognized
10848 tags. Some values in the vector are numbers, some bit masks, and some
10849 pointers to strings or other data. @value{GDBN} displays each value in the
10850 most appropriate form for a recognized tag, and in hexadecimal for
10851 an unrecognized tag.
10854 On some targets, @value{GDBN} can access operating system-specific
10855 information and show it to you. The types of information available
10856 will differ depending on the type of operating system running on the
10857 target. The mechanism used to fetch the data is described in
10858 @ref{Operating System Information}. For remote targets, this
10859 functionality depends on the remote stub's support of the
10860 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10864 @item info os @var{infotype}
10866 Display OS information of the requested type.
10868 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10870 @anchor{linux info os infotypes}
10872 @kindex info os cpus
10874 Display the list of all CPUs/cores. For each CPU/core, @value{GDBN} prints
10875 the available fields from /proc/cpuinfo. For each supported architecture
10876 different fields are available. Two common entries are processor which gives
10877 CPU number and bogomips; a system constant that is calculated during
10878 kernel initialization.
10880 @kindex info os files
10882 Display the list of open file descriptors on the target. For each
10883 file descriptor, @value{GDBN} prints the identifier of the process
10884 owning the descriptor, the command of the owning process, the value
10885 of the descriptor, and the target of the descriptor.
10887 @kindex info os modules
10889 Display the list of all loaded kernel modules on the target. For each
10890 module, @value{GDBN} prints the module name, the size of the module in
10891 bytes, the number of times the module is used, the dependencies of the
10892 module, the status of the module, and the address of the loaded module
10895 @kindex info os msg
10897 Display the list of all System V message queues on the target. For each
10898 message queue, @value{GDBN} prints the message queue key, the message
10899 queue identifier, the access permissions, the current number of bytes
10900 on the queue, the current number of messages on the queue, the processes
10901 that last sent and received a message on the queue, the user and group
10902 of the owner and creator of the message queue, the times at which a
10903 message was last sent and received on the queue, and the time at which
10904 the message queue was last changed.
10906 @kindex info os processes
10908 Display the list of processes on the target. For each process,
10909 @value{GDBN} prints the process identifier, the name of the user, the
10910 command corresponding to the process, and the list of processor cores
10911 that the process is currently running on. (To understand what these
10912 properties mean, for this and the following info types, please consult
10913 the general @sc{gnu}/Linux documentation.)
10915 @kindex info os procgroups
10917 Display the list of process groups on the target. For each process,
10918 @value{GDBN} prints the identifier of the process group that it belongs
10919 to, the command corresponding to the process group leader, the process
10920 identifier, and the command line of the process. The list is sorted
10921 first by the process group identifier, then by the process identifier,
10922 so that processes belonging to the same process group are grouped together
10923 and the process group leader is listed first.
10925 @kindex info os semaphores
10927 Display the list of all System V semaphore sets on the target. For each
10928 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10929 set identifier, the access permissions, the number of semaphores in the
10930 set, the user and group of the owner and creator of the semaphore set,
10931 and the times at which the semaphore set was operated upon and changed.
10933 @kindex info os shm
10935 Display the list of all System V shared-memory regions on the target.
10936 For each shared-memory region, @value{GDBN} prints the region key,
10937 the shared-memory identifier, the access permissions, the size of the
10938 region, the process that created the region, the process that last
10939 attached to or detached from the region, the current number of live
10940 attaches to the region, and the times at which the region was last
10941 attached to, detach from, and changed.
10943 @kindex info os sockets
10945 Display the list of Internet-domain sockets on the target. For each
10946 socket, @value{GDBN} prints the address and port of the local and
10947 remote endpoints, the current state of the connection, the creator of
10948 the socket, the IP address family of the socket, and the type of the
10951 @kindex info os threads
10953 Display the list of threads running on the target. For each thread,
10954 @value{GDBN} prints the identifier of the process that the thread
10955 belongs to, the command of the process, the thread identifier, and the
10956 processor core that it is currently running on. The main thread of a
10957 process is not listed.
10961 If @var{infotype} is omitted, then list the possible values for
10962 @var{infotype} and the kind of OS information available for each
10963 @var{infotype}. If the target does not return a list of possible
10964 types, this command will report an error.
10967 @node Memory Region Attributes
10968 @section Memory Region Attributes
10969 @cindex memory region attributes
10971 @dfn{Memory region attributes} allow you to describe special handling
10972 required by regions of your target's memory. @value{GDBN} uses
10973 attributes to determine whether to allow certain types of memory
10974 accesses; whether to use specific width accesses; and whether to cache
10975 target memory. By default the description of memory regions is
10976 fetched from the target (if the current target supports this), but the
10977 user can override the fetched regions.
10979 Defined memory regions can be individually enabled and disabled. When a
10980 memory region is disabled, @value{GDBN} uses the default attributes when
10981 accessing memory in that region. Similarly, if no memory regions have
10982 been defined, @value{GDBN} uses the default attributes when accessing
10985 When a memory region is defined, it is given a number to identify it;
10986 to enable, disable, or remove a memory region, you specify that number.
10990 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10991 Define a memory region bounded by @var{lower} and @var{upper} with
10992 attributes @var{attributes}@dots{}, and add it to the list of regions
10993 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10994 case: it is treated as the target's maximum memory address.
10995 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10998 Discard any user changes to the memory regions and use target-supplied
10999 regions, if available, or no regions if the target does not support.
11002 @item delete mem @var{nums}@dots{}
11003 Remove memory regions @var{nums}@dots{} from the list of regions
11004 monitored by @value{GDBN}.
11006 @kindex disable mem
11007 @item disable mem @var{nums}@dots{}
11008 Disable monitoring of memory regions @var{nums}@dots{}.
11009 A disabled memory region is not forgotten.
11010 It may be enabled again later.
11013 @item enable mem @var{nums}@dots{}
11014 Enable monitoring of memory regions @var{nums}@dots{}.
11018 Print a table of all defined memory regions, with the following columns
11022 @item Memory Region Number
11023 @item Enabled or Disabled.
11024 Enabled memory regions are marked with @samp{y}.
11025 Disabled memory regions are marked with @samp{n}.
11028 The address defining the inclusive lower bound of the memory region.
11031 The address defining the exclusive upper bound of the memory region.
11034 The list of attributes set for this memory region.
11039 @subsection Attributes
11041 @subsubsection Memory Access Mode
11042 The access mode attributes set whether @value{GDBN} may make read or
11043 write accesses to a memory region.
11045 While these attributes prevent @value{GDBN} from performing invalid
11046 memory accesses, they do nothing to prevent the target system, I/O DMA,
11047 etc.@: from accessing memory.
11051 Memory is read only.
11053 Memory is write only.
11055 Memory is read/write. This is the default.
11058 @subsubsection Memory Access Size
11059 The access size attribute tells @value{GDBN} to use specific sized
11060 accesses in the memory region. Often memory mapped device registers
11061 require specific sized accesses. If no access size attribute is
11062 specified, @value{GDBN} may use accesses of any size.
11066 Use 8 bit memory accesses.
11068 Use 16 bit memory accesses.
11070 Use 32 bit memory accesses.
11072 Use 64 bit memory accesses.
11075 @c @subsubsection Hardware/Software Breakpoints
11076 @c The hardware/software breakpoint attributes set whether @value{GDBN}
11077 @c will use hardware or software breakpoints for the internal breakpoints
11078 @c used by the step, next, finish, until, etc. commands.
11082 @c Always use hardware breakpoints
11083 @c @item swbreak (default)
11086 @subsubsection Data Cache
11087 The data cache attributes set whether @value{GDBN} will cache target
11088 memory. While this generally improves performance by reducing debug
11089 protocol overhead, it can lead to incorrect results because @value{GDBN}
11090 does not know about volatile variables or memory mapped device
11095 Enable @value{GDBN} to cache target memory.
11097 Disable @value{GDBN} from caching target memory. This is the default.
11100 @subsection Memory Access Checking
11101 @value{GDBN} can be instructed to refuse accesses to memory that is
11102 not explicitly described. This can be useful if accessing such
11103 regions has undesired effects for a specific target, or to provide
11104 better error checking. The following commands control this behaviour.
11107 @kindex set mem inaccessible-by-default
11108 @item set mem inaccessible-by-default [on|off]
11109 If @code{on} is specified, make @value{GDBN} treat memory not
11110 explicitly described by the memory ranges as non-existent and refuse accesses
11111 to such memory. The checks are only performed if there's at least one
11112 memory range defined. If @code{off} is specified, make @value{GDBN}
11113 treat the memory not explicitly described by the memory ranges as RAM.
11114 The default value is @code{on}.
11115 @kindex show mem inaccessible-by-default
11116 @item show mem inaccessible-by-default
11117 Show the current handling of accesses to unknown memory.
11121 @c @subsubsection Memory Write Verification
11122 @c The memory write verification attributes set whether @value{GDBN}
11123 @c will re-reads data after each write to verify the write was successful.
11127 @c @item noverify (default)
11130 @node Dump/Restore Files
11131 @section Copy Between Memory and a File
11132 @cindex dump/restore files
11133 @cindex append data to a file
11134 @cindex dump data to a file
11135 @cindex restore data from a file
11137 You can use the commands @code{dump}, @code{append}, and
11138 @code{restore} to copy data between target memory and a file. The
11139 @code{dump} and @code{append} commands write data to a file, and the
11140 @code{restore} command reads data from a file back into the inferior's
11141 memory. Files may be in binary, Motorola S-record, Intel hex,
11142 Tektronix Hex, or Verilog Hex format; however, @value{GDBN} can only
11143 append to binary files, and cannot read from Verilog Hex files.
11148 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11149 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
11150 Dump the contents of memory from @var{start_addr} to @var{end_addr},
11151 or the value of @var{expr}, to @var{filename} in the given format.
11153 The @var{format} parameter may be any one of:
11160 Motorola S-record format.
11162 Tektronix Hex format.
11164 Verilog Hex format.
11167 @value{GDBN} uses the same definitions of these formats as the
11168 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
11169 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
11173 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
11174 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
11175 Append the contents of memory from @var{start_addr} to @var{end_addr},
11176 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
11177 (@value{GDBN} can only append data to files in raw binary form.)
11180 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
11181 Restore the contents of file @var{filename} into memory. The
11182 @code{restore} command can automatically recognize any known @sc{bfd}
11183 file format, except for raw binary. To restore a raw binary file you
11184 must specify the optional keyword @code{binary} after the filename.
11186 If @var{bias} is non-zero, its value will be added to the addresses
11187 contained in the file. Binary files always start at address zero, so
11188 they will be restored at address @var{bias}. Other bfd files have
11189 a built-in location; they will be restored at offset @var{bias}
11190 from that location.
11192 If @var{start} and/or @var{end} are non-zero, then only data between
11193 file offset @var{start} and file offset @var{end} will be restored.
11194 These offsets are relative to the addresses in the file, before
11195 the @var{bias} argument is applied.
11199 @node Core File Generation
11200 @section How to Produce a Core File from Your Program
11201 @cindex dump core from inferior
11203 A @dfn{core file} or @dfn{core dump} is a file that records the memory
11204 image of a running process and its process status (register values
11205 etc.). Its primary use is post-mortem debugging of a program that
11206 crashed while it ran outside a debugger. A program that crashes
11207 automatically produces a core file, unless this feature is disabled by
11208 the user. @xref{Files}, for information on invoking @value{GDBN} in
11209 the post-mortem debugging mode.
11211 Occasionally, you may wish to produce a core file of the program you
11212 are debugging in order to preserve a snapshot of its state.
11213 @value{GDBN} has a special command for that.
11217 @kindex generate-core-file
11218 @item generate-core-file [@var{file}]
11219 @itemx gcore [@var{file}]
11220 Produce a core dump of the inferior process. The optional argument
11221 @var{file} specifies the file name where to put the core dump. If not
11222 specified, the file name defaults to @file{core.@var{pid}}, where
11223 @var{pid} is the inferior process ID.
11225 Note that this command is implemented only for some systems (as of
11226 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
11228 On @sc{gnu}/Linux, this command can take into account the value of the
11229 file @file{/proc/@var{pid}/coredump_filter} when generating the core
11230 dump (@pxref{set use-coredump-filter}).
11232 @kindex set use-coredump-filter
11233 @anchor{set use-coredump-filter}
11234 @item set use-coredump-filter on
11235 @itemx set use-coredump-filter off
11236 Enable or disable the use of the file
11237 @file{/proc/@var{pid}/coredump_filter} when generating core dump
11238 files. This file is used by the Linux kernel to decide what types of
11239 memory mappings will be dumped or ignored when generating a core dump
11240 file. @var{pid} is the process ID of a currently running process.
11242 To make use of this feature, you have to write in the
11243 @file{/proc/@var{pid}/coredump_filter} file a value, in hexadecimal,
11244 which is a bit mask representing the memory mapping types. If a bit
11245 is set in the bit mask, then the memory mappings of the corresponding
11246 types will be dumped; otherwise, they will be ignored. This
11247 configuration is inherited by child processes. For more information
11248 about the bits that can be set in the
11249 @file{/proc/@var{pid}/coredump_filter} file, please refer to the
11250 manpage of @code{core(5)}.
11252 By default, this option is @code{on}. If this option is turned
11253 @code{off}, @value{GDBN} does not read the @file{coredump_filter} file
11254 and instead uses the same default value as the Linux kernel in order
11255 to decide which pages will be dumped in the core dump file. This
11256 value is currently @code{0x33}, which means that bits @code{0}
11257 (anonymous private mappings), @code{1} (anonymous shared mappings),
11258 @code{4} (ELF headers) and @code{5} (private huge pages) are active.
11259 This will cause these memory mappings to be dumped automatically.
11262 @node Character Sets
11263 @section Character Sets
11264 @cindex character sets
11266 @cindex translating between character sets
11267 @cindex host character set
11268 @cindex target character set
11270 If the program you are debugging uses a different character set to
11271 represent characters and strings than the one @value{GDBN} uses itself,
11272 @value{GDBN} can automatically translate between the character sets for
11273 you. The character set @value{GDBN} uses we call the @dfn{host
11274 character set}; the one the inferior program uses we call the
11275 @dfn{target character set}.
11277 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
11278 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
11279 remote protocol (@pxref{Remote Debugging}) to debug a program
11280 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
11281 then the host character set is Latin-1, and the target character set is
11282 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
11283 target-charset EBCDIC-US}, then @value{GDBN} translates between
11284 @sc{ebcdic} and Latin 1 as you print character or string values, or use
11285 character and string literals in expressions.
11287 @value{GDBN} has no way to automatically recognize which character set
11288 the inferior program uses; you must tell it, using the @code{set
11289 target-charset} command, described below.
11291 Here are the commands for controlling @value{GDBN}'s character set
11295 @item set target-charset @var{charset}
11296 @kindex set target-charset
11297 Set the current target character set to @var{charset}. To display the
11298 list of supported target character sets, type
11299 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
11301 @item set host-charset @var{charset}
11302 @kindex set host-charset
11303 Set the current host character set to @var{charset}.
11305 By default, @value{GDBN} uses a host character set appropriate to the
11306 system it is running on; you can override that default using the
11307 @code{set host-charset} command. On some systems, @value{GDBN} cannot
11308 automatically determine the appropriate host character set. In this
11309 case, @value{GDBN} uses @samp{UTF-8}.
11311 @value{GDBN} can only use certain character sets as its host character
11312 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
11313 @value{GDBN} will list the host character sets it supports.
11315 @item set charset @var{charset}
11316 @kindex set charset
11317 Set the current host and target character sets to @var{charset}. As
11318 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
11319 @value{GDBN} will list the names of the character sets that can be used
11320 for both host and target.
11323 @kindex show charset
11324 Show the names of the current host and target character sets.
11326 @item show host-charset
11327 @kindex show host-charset
11328 Show the name of the current host character set.
11330 @item show target-charset
11331 @kindex show target-charset
11332 Show the name of the current target character set.
11334 @item set target-wide-charset @var{charset}
11335 @kindex set target-wide-charset
11336 Set the current target's wide character set to @var{charset}. This is
11337 the character set used by the target's @code{wchar_t} type. To
11338 display the list of supported wide character sets, type
11339 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
11341 @item show target-wide-charset
11342 @kindex show target-wide-charset
11343 Show the name of the current target's wide character set.
11346 Here is an example of @value{GDBN}'s character set support in action.
11347 Assume that the following source code has been placed in the file
11348 @file{charset-test.c}:
11354 = @{72, 101, 108, 108, 111, 44, 32, 119,
11355 111, 114, 108, 100, 33, 10, 0@};
11356 char ibm1047_hello[]
11357 = @{200, 133, 147, 147, 150, 107, 64, 166,
11358 150, 153, 147, 132, 90, 37, 0@};
11362 printf ("Hello, world!\n");
11366 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
11367 containing the string @samp{Hello, world!} followed by a newline,
11368 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
11370 We compile the program, and invoke the debugger on it:
11373 $ gcc -g charset-test.c -o charset-test
11374 $ gdb -nw charset-test
11375 GNU gdb 2001-12-19-cvs
11376 Copyright 2001 Free Software Foundation, Inc.
11381 We can use the @code{show charset} command to see what character sets
11382 @value{GDBN} is currently using to interpret and display characters and
11386 (@value{GDBP}) show charset
11387 The current host and target character set is `ISO-8859-1'.
11391 For the sake of printing this manual, let's use @sc{ascii} as our
11392 initial character set:
11394 (@value{GDBP}) set charset ASCII
11395 (@value{GDBP}) show charset
11396 The current host and target character set is `ASCII'.
11400 Let's assume that @sc{ascii} is indeed the correct character set for our
11401 host system --- in other words, let's assume that if @value{GDBN} prints
11402 characters using the @sc{ascii} character set, our terminal will display
11403 them properly. Since our current target character set is also
11404 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
11407 (@value{GDBP}) print ascii_hello
11408 $1 = 0x401698 "Hello, world!\n"
11409 (@value{GDBP}) print ascii_hello[0]
11414 @value{GDBN} uses the target character set for character and string
11415 literals you use in expressions:
11418 (@value{GDBP}) print '+'
11423 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
11426 @value{GDBN} relies on the user to tell it which character set the
11427 target program uses. If we print @code{ibm1047_hello} while our target
11428 character set is still @sc{ascii}, we get jibberish:
11431 (@value{GDBP}) print ibm1047_hello
11432 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
11433 (@value{GDBP}) print ibm1047_hello[0]
11438 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
11439 @value{GDBN} tells us the character sets it supports:
11442 (@value{GDBP}) set target-charset
11443 ASCII EBCDIC-US IBM1047 ISO-8859-1
11444 (@value{GDBP}) set target-charset
11447 We can select @sc{ibm1047} as our target character set, and examine the
11448 program's strings again. Now the @sc{ascii} string is wrong, but
11449 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
11450 target character set, @sc{ibm1047}, to the host character set,
11451 @sc{ascii}, and they display correctly:
11454 (@value{GDBP}) set target-charset IBM1047
11455 (@value{GDBP}) show charset
11456 The current host character set is `ASCII'.
11457 The current target character set is `IBM1047'.
11458 (@value{GDBP}) print ascii_hello
11459 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
11460 (@value{GDBP}) print ascii_hello[0]
11462 (@value{GDBP}) print ibm1047_hello
11463 $8 = 0x4016a8 "Hello, world!\n"
11464 (@value{GDBP}) print ibm1047_hello[0]
11469 As above, @value{GDBN} uses the target character set for character and
11470 string literals you use in expressions:
11473 (@value{GDBP}) print '+'
11478 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
11481 @node Caching Target Data
11482 @section Caching Data of Targets
11483 @cindex caching data of targets
11485 @value{GDBN} caches data exchanged between the debugger and a target.
11486 Each cache is associated with the address space of the inferior.
11487 @xref{Inferiors and Programs}, about inferior and address space.
11488 Such caching generally improves performance in remote debugging
11489 (@pxref{Remote Debugging}), because it reduces the overhead of the
11490 remote protocol by bundling memory reads and writes into large chunks.
11491 Unfortunately, simply caching everything would lead to incorrect results,
11492 since @value{GDBN} does not necessarily know anything about volatile
11493 values, memory-mapped I/O addresses, etc. Furthermore, in non-stop mode
11494 (@pxref{Non-Stop Mode}) memory can be changed @emph{while} a gdb command
11496 Therefore, by default, @value{GDBN} only caches data
11497 known to be on the stack@footnote{In non-stop mode, it is moderately
11498 rare for a running thread to modify the stack of a stopped thread
11499 in a way that would interfere with a backtrace, and caching of
11500 stack reads provides a significant speed up of remote backtraces.} or
11501 in the code segment.
11502 Other regions of memory can be explicitly marked as
11503 cacheable; @pxref{Memory Region Attributes}.
11506 @kindex set remotecache
11507 @item set remotecache on
11508 @itemx set remotecache off
11509 This option no longer does anything; it exists for compatibility
11512 @kindex show remotecache
11513 @item show remotecache
11514 Show the current state of the obsolete remotecache flag.
11516 @kindex set stack-cache
11517 @item set stack-cache on
11518 @itemx set stack-cache off
11519 Enable or disable caching of stack accesses. When @code{on}, use
11520 caching. By default, this option is @code{on}.
11522 @kindex show stack-cache
11523 @item show stack-cache
11524 Show the current state of data caching for memory accesses.
11526 @kindex set code-cache
11527 @item set code-cache on
11528 @itemx set code-cache off
11529 Enable or disable caching of code segment accesses. When @code{on},
11530 use caching. By default, this option is @code{on}. This improves
11531 performance of disassembly in remote debugging.
11533 @kindex show code-cache
11534 @item show code-cache
11535 Show the current state of target memory cache for code segment
11538 @kindex info dcache
11539 @item info dcache @r{[}line@r{]}
11540 Print the information about the performance of data cache of the
11541 current inferior's address space. The information displayed
11542 includes the dcache width and depth, and for each cache line, its
11543 number, address, and how many times it was referenced. This
11544 command is useful for debugging the data cache operation.
11546 If a line number is specified, the contents of that line will be
11549 @item set dcache size @var{size}
11550 @cindex dcache size
11551 @kindex set dcache size
11552 Set maximum number of entries in dcache (dcache depth above).
11554 @item set dcache line-size @var{line-size}
11555 @cindex dcache line-size
11556 @kindex set dcache line-size
11557 Set number of bytes each dcache entry caches (dcache width above).
11558 Must be a power of 2.
11560 @item show dcache size
11561 @kindex show dcache size
11562 Show maximum number of dcache entries. @xref{Caching Target Data, info dcache}.
11564 @item show dcache line-size
11565 @kindex show dcache line-size
11566 Show default size of dcache lines.
11570 @node Searching Memory
11571 @section Search Memory
11572 @cindex searching memory
11574 Memory can be searched for a particular sequence of bytes with the
11575 @code{find} command.
11579 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11580 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
11581 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
11582 etc. The search begins at address @var{start_addr} and continues for either
11583 @var{len} bytes or through to @var{end_addr} inclusive.
11586 @var{s} and @var{n} are optional parameters.
11587 They may be specified in either order, apart or together.
11590 @item @var{s}, search query size
11591 The size of each search query value.
11597 halfwords (two bytes)
11601 giant words (eight bytes)
11604 All values are interpreted in the current language.
11605 This means, for example, that if the current source language is C/C@t{++}
11606 then searching for the string ``hello'' includes the trailing '\0'.
11608 If the value size is not specified, it is taken from the
11609 value's type in the current language.
11610 This is useful when one wants to specify the search
11611 pattern as a mixture of types.
11612 Note that this means, for example, that in the case of C-like languages
11613 a search for an untyped 0x42 will search for @samp{(int) 0x42}
11614 which is typically four bytes.
11616 @item @var{n}, maximum number of finds
11617 The maximum number of matches to print. The default is to print all finds.
11620 You can use strings as search values. Quote them with double-quotes
11622 The string value is copied into the search pattern byte by byte,
11623 regardless of the endianness of the target and the size specification.
11625 The address of each match found is printed as well as a count of the
11626 number of matches found.
11628 The address of the last value found is stored in convenience variable
11630 A count of the number of matches is stored in @samp{$numfound}.
11632 For example, if stopped at the @code{printf} in this function:
11638 static char hello[] = "hello-hello";
11639 static struct @{ char c; short s; int i; @}
11640 __attribute__ ((packed)) mixed
11641 = @{ 'c', 0x1234, 0x87654321 @};
11642 printf ("%s\n", hello);
11647 you get during debugging:
11650 (gdb) find &hello[0], +sizeof(hello), "hello"
11651 0x804956d <hello.1620+6>
11653 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
11654 0x8049567 <hello.1620>
11655 0x804956d <hello.1620+6>
11657 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
11658 0x8049567 <hello.1620>
11660 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
11661 0x8049560 <mixed.1625>
11663 (gdb) print $numfound
11666 $2 = (void *) 0x8049560
11669 @node Optimized Code
11670 @chapter Debugging Optimized Code
11671 @cindex optimized code, debugging
11672 @cindex debugging optimized code
11674 Almost all compilers support optimization. With optimization
11675 disabled, the compiler generates assembly code that corresponds
11676 directly to your source code, in a simplistic way. As the compiler
11677 applies more powerful optimizations, the generated assembly code
11678 diverges from your original source code. With help from debugging
11679 information generated by the compiler, @value{GDBN} can map from
11680 the running program back to constructs from your original source.
11682 @value{GDBN} is more accurate with optimization disabled. If you
11683 can recompile without optimization, it is easier to follow the
11684 progress of your program during debugging. But, there are many cases
11685 where you may need to debug an optimized version.
11687 When you debug a program compiled with @samp{-g -O}, remember that the
11688 optimizer has rearranged your code; the debugger shows you what is
11689 really there. Do not be too surprised when the execution path does not
11690 exactly match your source file! An extreme example: if you define a
11691 variable, but never use it, @value{GDBN} never sees that
11692 variable---because the compiler optimizes it out of existence.
11694 Some things do not work as well with @samp{-g -O} as with just
11695 @samp{-g}, particularly on machines with instruction scheduling. If in
11696 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
11697 please report it to us as a bug (including a test case!).
11698 @xref{Variables}, for more information about debugging optimized code.
11701 * Inline Functions:: How @value{GDBN} presents inlining
11702 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
11705 @node Inline Functions
11706 @section Inline Functions
11707 @cindex inline functions, debugging
11709 @dfn{Inlining} is an optimization that inserts a copy of the function
11710 body directly at each call site, instead of jumping to a shared
11711 routine. @value{GDBN} displays inlined functions just like
11712 non-inlined functions. They appear in backtraces. You can view their
11713 arguments and local variables, step into them with @code{step}, skip
11714 them with @code{next}, and escape from them with @code{finish}.
11715 You can check whether a function was inlined by using the
11716 @code{info frame} command.
11718 For @value{GDBN} to support inlined functions, the compiler must
11719 record information about inlining in the debug information ---
11720 @value{NGCC} using the @sc{dwarf 2} format does this, and several
11721 other compilers do also. @value{GDBN} only supports inlined functions
11722 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
11723 do not emit two required attributes (@samp{DW_AT_call_file} and
11724 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
11725 function calls with earlier versions of @value{NGCC}. It instead
11726 displays the arguments and local variables of inlined functions as
11727 local variables in the caller.
11729 The body of an inlined function is directly included at its call site;
11730 unlike a non-inlined function, there are no instructions devoted to
11731 the call. @value{GDBN} still pretends that the call site and the
11732 start of the inlined function are different instructions. Stepping to
11733 the call site shows the call site, and then stepping again shows
11734 the first line of the inlined function, even though no additional
11735 instructions are executed.
11737 This makes source-level debugging much clearer; you can see both the
11738 context of the call and then the effect of the call. Only stepping by
11739 a single instruction using @code{stepi} or @code{nexti} does not do
11740 this; single instruction steps always show the inlined body.
11742 There are some ways that @value{GDBN} does not pretend that inlined
11743 function calls are the same as normal calls:
11747 Setting breakpoints at the call site of an inlined function may not
11748 work, because the call site does not contain any code. @value{GDBN}
11749 may incorrectly move the breakpoint to the next line of the enclosing
11750 function, after the call. This limitation will be removed in a future
11751 version of @value{GDBN}; until then, set a breakpoint on an earlier line
11752 or inside the inlined function instead.
11755 @value{GDBN} cannot locate the return value of inlined calls after
11756 using the @code{finish} command. This is a limitation of compiler-generated
11757 debugging information; after @code{finish}, you can step to the next line
11758 and print a variable where your program stored the return value.
11762 @node Tail Call Frames
11763 @section Tail Call Frames
11764 @cindex tail call frames, debugging
11766 Function @code{B} can call function @code{C} in its very last statement. In
11767 unoptimized compilation the call of @code{C} is immediately followed by return
11768 instruction at the end of @code{B} code. Optimizing compiler may replace the
11769 call and return in function @code{B} into one jump to function @code{C}
11770 instead. Such use of a jump instruction is called @dfn{tail call}.
11772 During execution of function @code{C}, there will be no indication in the
11773 function call stack frames that it was tail-called from @code{B}. If function
11774 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
11775 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
11776 some cases @value{GDBN} can determine that @code{C} was tail-called from
11777 @code{B}, and it will then create fictitious call frame for that, with the
11778 return address set up as if @code{B} called @code{C} normally.
11780 This functionality is currently supported only by DWARF 2 debugging format and
11781 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
11782 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
11785 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
11786 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
11790 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
11792 Stack level 1, frame at 0x7fffffffda30:
11793 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
11794 tail call frame, caller of frame at 0x7fffffffda30
11795 source language c++.
11796 Arglist at unknown address.
11797 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
11800 The detection of all the possible code path executions can find them ambiguous.
11801 There is no execution history stored (possible @ref{Reverse Execution} is never
11802 used for this purpose) and the last known caller could have reached the known
11803 callee by multiple different jump sequences. In such case @value{GDBN} still
11804 tries to show at least all the unambiguous top tail callers and all the
11805 unambiguous bottom tail calees, if any.
11808 @anchor{set debug entry-values}
11809 @item set debug entry-values
11810 @kindex set debug entry-values
11811 When set to on, enables printing of analysis messages for both frame argument
11812 values at function entry and tail calls. It will show all the possible valid
11813 tail calls code paths it has considered. It will also print the intersection
11814 of them with the final unambiguous (possibly partial or even empty) code path
11817 @item show debug entry-values
11818 @kindex show debug entry-values
11819 Show the current state of analysis messages printing for both frame argument
11820 values at function entry and tail calls.
11823 The analysis messages for tail calls can for example show why the virtual tail
11824 call frame for function @code{c} has not been recognized (due to the indirect
11825 reference by variable @code{x}):
11828 static void __attribute__((noinline, noclone)) c (void);
11829 void (*x) (void) = c;
11830 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11831 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11832 int main (void) @{ x (); return 0; @}
11834 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11835 DW_TAG_GNU_call_site 0x40039a in main
11837 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11840 #1 0x000000000040039a in main () at t.c:5
11843 Another possibility is an ambiguous virtual tail call frames resolution:
11847 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11848 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11849 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11850 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11851 static void __attribute__((noinline, noclone)) b (void)
11852 @{ if (i) c (); else e (); @}
11853 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11854 int main (void) @{ a (); return 0; @}
11856 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11857 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11858 tailcall: reduced: 0x4004d2(a) |
11861 #1 0x00000000004004d2 in a () at t.c:8
11862 #2 0x0000000000400395 in main () at t.c:9
11865 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11866 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11868 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11869 @ifset HAVE_MAKEINFO_CLICK
11870 @set ARROW @click{}
11871 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11872 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11874 @ifclear HAVE_MAKEINFO_CLICK
11876 @set CALLSEQ1B @value{CALLSEQ1A}
11877 @set CALLSEQ2B @value{CALLSEQ2A}
11880 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11881 The code can have possible execution paths @value{CALLSEQ1B} or
11882 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11884 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11885 has found. It then finds another possible calling sequcen - that one is
11886 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11887 printed as the @code{reduced:} calling sequence. That one could have many
11888 futher @code{compare:} and @code{reduced:} statements as long as there remain
11889 any non-ambiguous sequence entries.
11891 For the frame of function @code{b} in both cases there are different possible
11892 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11893 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11894 therefore this one is displayed to the user while the ambiguous frames are
11897 There can be also reasons why printing of frame argument values at function
11902 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11903 static void __attribute__((noinline, noclone)) a (int i);
11904 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11905 static void __attribute__((noinline, noclone)) a (int i)
11906 @{ if (i) b (i - 1); else c (0); @}
11907 int main (void) @{ a (5); return 0; @}
11910 #0 c (i=i@@entry=0) at t.c:2
11911 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11912 function "a" at 0x400420 can call itself via tail calls
11913 i=<optimized out>) at t.c:6
11914 #2 0x000000000040036e in main () at t.c:7
11917 @value{GDBN} cannot find out from the inferior state if and how many times did
11918 function @code{a} call itself (via function @code{b}) as these calls would be
11919 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11920 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11921 prints @code{<optimized out>} instead.
11924 @chapter C Preprocessor Macros
11926 Some languages, such as C and C@t{++}, provide a way to define and invoke
11927 ``preprocessor macros'' which expand into strings of tokens.
11928 @value{GDBN} can evaluate expressions containing macro invocations, show
11929 the result of macro expansion, and show a macro's definition, including
11930 where it was defined.
11932 You may need to compile your program specially to provide @value{GDBN}
11933 with information about preprocessor macros. Most compilers do not
11934 include macros in their debugging information, even when you compile
11935 with the @option{-g} flag. @xref{Compilation}.
11937 A program may define a macro at one point, remove that definition later,
11938 and then provide a different definition after that. Thus, at different
11939 points in the program, a macro may have different definitions, or have
11940 no definition at all. If there is a current stack frame, @value{GDBN}
11941 uses the macros in scope at that frame's source code line. Otherwise,
11942 @value{GDBN} uses the macros in scope at the current listing location;
11945 Whenever @value{GDBN} evaluates an expression, it always expands any
11946 macro invocations present in the expression. @value{GDBN} also provides
11947 the following commands for working with macros explicitly.
11951 @kindex macro expand
11952 @cindex macro expansion, showing the results of preprocessor
11953 @cindex preprocessor macro expansion, showing the results of
11954 @cindex expanding preprocessor macros
11955 @item macro expand @var{expression}
11956 @itemx macro exp @var{expression}
11957 Show the results of expanding all preprocessor macro invocations in
11958 @var{expression}. Since @value{GDBN} simply expands macros, but does
11959 not parse the result, @var{expression} need not be a valid expression;
11960 it can be any string of tokens.
11963 @item macro expand-once @var{expression}
11964 @itemx macro exp1 @var{expression}
11965 @cindex expand macro once
11966 @i{(This command is not yet implemented.)} Show the results of
11967 expanding those preprocessor macro invocations that appear explicitly in
11968 @var{expression}. Macro invocations appearing in that expansion are
11969 left unchanged. This command allows you to see the effect of a
11970 particular macro more clearly, without being confused by further
11971 expansions. Since @value{GDBN} simply expands macros, but does not
11972 parse the result, @var{expression} need not be a valid expression; it
11973 can be any string of tokens.
11976 @cindex macro definition, showing
11977 @cindex definition of a macro, showing
11978 @cindex macros, from debug info
11979 @item info macro [-a|-all] [--] @var{macro}
11980 Show the current definition or all definitions of the named @var{macro},
11981 and describe the source location or compiler command-line where that
11982 definition was established. The optional double dash is to signify the end of
11983 argument processing and the beginning of @var{macro} for non C-like macros where
11984 the macro may begin with a hyphen.
11986 @kindex info macros
11987 @item info macros @var{location}
11988 Show all macro definitions that are in effect at the location specified
11989 by @var{location}, and describe the source location or compiler
11990 command-line where those definitions were established.
11992 @kindex macro define
11993 @cindex user-defined macros
11994 @cindex defining macros interactively
11995 @cindex macros, user-defined
11996 @item macro define @var{macro} @var{replacement-list}
11997 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11998 Introduce a definition for a preprocessor macro named @var{macro},
11999 invocations of which are replaced by the tokens given in
12000 @var{replacement-list}. The first form of this command defines an
12001 ``object-like'' macro, which takes no arguments; the second form
12002 defines a ``function-like'' macro, which takes the arguments given in
12005 A definition introduced by this command is in scope in every
12006 expression evaluated in @value{GDBN}, until it is removed with the
12007 @code{macro undef} command, described below. The definition overrides
12008 all definitions for @var{macro} present in the program being debugged,
12009 as well as any previous user-supplied definition.
12011 @kindex macro undef
12012 @item macro undef @var{macro}
12013 Remove any user-supplied definition for the macro named @var{macro}.
12014 This command only affects definitions provided with the @code{macro
12015 define} command, described above; it cannot remove definitions present
12016 in the program being debugged.
12020 List all the macros defined using the @code{macro define} command.
12023 @cindex macros, example of debugging with
12024 Here is a transcript showing the above commands in action. First, we
12025 show our source files:
12030 #include "sample.h"
12033 #define ADD(x) (M + x)
12038 printf ("Hello, world!\n");
12040 printf ("We're so creative.\n");
12042 printf ("Goodbye, world!\n");
12049 Now, we compile the program using the @sc{gnu} C compiler,
12050 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
12051 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
12052 and @option{-gdwarf-4}; we recommend always choosing the most recent
12053 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
12054 includes information about preprocessor macros in the debugging
12058 $ gcc -gdwarf-2 -g3 sample.c -o sample
12062 Now, we start @value{GDBN} on our sample program:
12066 GNU gdb 2002-05-06-cvs
12067 Copyright 2002 Free Software Foundation, Inc.
12068 GDB is free software, @dots{}
12072 We can expand macros and examine their definitions, even when the
12073 program is not running. @value{GDBN} uses the current listing position
12074 to decide which macro definitions are in scope:
12077 (@value{GDBP}) list main
12080 5 #define ADD(x) (M + x)
12085 10 printf ("Hello, world!\n");
12087 12 printf ("We're so creative.\n");
12088 (@value{GDBP}) info macro ADD
12089 Defined at /home/jimb/gdb/macros/play/sample.c:5
12090 #define ADD(x) (M + x)
12091 (@value{GDBP}) info macro Q
12092 Defined at /home/jimb/gdb/macros/play/sample.h:1
12093 included at /home/jimb/gdb/macros/play/sample.c:2
12095 (@value{GDBP}) macro expand ADD(1)
12096 expands to: (42 + 1)
12097 (@value{GDBP}) macro expand-once ADD(1)
12098 expands to: once (M + 1)
12102 In the example above, note that @code{macro expand-once} expands only
12103 the macro invocation explicit in the original text --- the invocation of
12104 @code{ADD} --- but does not expand the invocation of the macro @code{M},
12105 which was introduced by @code{ADD}.
12107 Once the program is running, @value{GDBN} uses the macro definitions in
12108 force at the source line of the current stack frame:
12111 (@value{GDBP}) break main
12112 Breakpoint 1 at 0x8048370: file sample.c, line 10.
12114 Starting program: /home/jimb/gdb/macros/play/sample
12116 Breakpoint 1, main () at sample.c:10
12117 10 printf ("Hello, world!\n");
12121 At line 10, the definition of the macro @code{N} at line 9 is in force:
12124 (@value{GDBP}) info macro N
12125 Defined at /home/jimb/gdb/macros/play/sample.c:9
12127 (@value{GDBP}) macro expand N Q M
12128 expands to: 28 < 42
12129 (@value{GDBP}) print N Q M
12134 As we step over directives that remove @code{N}'s definition, and then
12135 give it a new definition, @value{GDBN} finds the definition (or lack
12136 thereof) in force at each point:
12139 (@value{GDBP}) next
12141 12 printf ("We're so creative.\n");
12142 (@value{GDBP}) info macro N
12143 The symbol `N' has no definition as a C/C++ preprocessor macro
12144 at /home/jimb/gdb/macros/play/sample.c:12
12145 (@value{GDBP}) next
12147 14 printf ("Goodbye, world!\n");
12148 (@value{GDBP}) info macro N
12149 Defined at /home/jimb/gdb/macros/play/sample.c:13
12151 (@value{GDBP}) macro expand N Q M
12152 expands to: 1729 < 42
12153 (@value{GDBP}) print N Q M
12158 In addition to source files, macros can be defined on the compilation command
12159 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
12160 such a way, @value{GDBN} displays the location of their definition as line zero
12161 of the source file submitted to the compiler.
12164 (@value{GDBP}) info macro __STDC__
12165 Defined at /home/jimb/gdb/macros/play/sample.c:0
12172 @chapter Tracepoints
12173 @c This chapter is based on the documentation written by Michael
12174 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
12176 @cindex tracepoints
12177 In some applications, it is not feasible for the debugger to interrupt
12178 the program's execution long enough for the developer to learn
12179 anything helpful about its behavior. If the program's correctness
12180 depends on its real-time behavior, delays introduced by a debugger
12181 might cause the program to change its behavior drastically, or perhaps
12182 fail, even when the code itself is correct. It is useful to be able
12183 to observe the program's behavior without interrupting it.
12185 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
12186 specify locations in the program, called @dfn{tracepoints}, and
12187 arbitrary expressions to evaluate when those tracepoints are reached.
12188 Later, using the @code{tfind} command, you can examine the values
12189 those expressions had when the program hit the tracepoints. The
12190 expressions may also denote objects in memory---structures or arrays,
12191 for example---whose values @value{GDBN} should record; while visiting
12192 a particular tracepoint, you may inspect those objects as if they were
12193 in memory at that moment. However, because @value{GDBN} records these
12194 values without interacting with you, it can do so quickly and
12195 unobtrusively, hopefully not disturbing the program's behavior.
12197 The tracepoint facility is currently available only for remote
12198 targets. @xref{Targets}. In addition, your remote target must know
12199 how to collect trace data. This functionality is implemented in the
12200 remote stub; however, none of the stubs distributed with @value{GDBN}
12201 support tracepoints as of this writing. The format of the remote
12202 packets used to implement tracepoints are described in @ref{Tracepoint
12205 It is also possible to get trace data from a file, in a manner reminiscent
12206 of corefiles; you specify the filename, and use @code{tfind} to search
12207 through the file. @xref{Trace Files}, for more details.
12209 This chapter describes the tracepoint commands and features.
12212 * Set Tracepoints::
12213 * Analyze Collected Data::
12214 * Tracepoint Variables::
12218 @node Set Tracepoints
12219 @section Commands to Set Tracepoints
12221 Before running such a @dfn{trace experiment}, an arbitrary number of
12222 tracepoints can be set. A tracepoint is actually a special type of
12223 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
12224 standard breakpoint commands. For instance, as with breakpoints,
12225 tracepoint numbers are successive integers starting from one, and many
12226 of the commands associated with tracepoints take the tracepoint number
12227 as their argument, to identify which tracepoint to work on.
12229 For each tracepoint, you can specify, in advance, some arbitrary set
12230 of data that you want the target to collect in the trace buffer when
12231 it hits that tracepoint. The collected data can include registers,
12232 local variables, or global data. Later, you can use @value{GDBN}
12233 commands to examine the values these data had at the time the
12234 tracepoint was hit.
12236 Tracepoints do not support every breakpoint feature. Ignore counts on
12237 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
12238 commands when they are hit. Tracepoints may not be thread-specific
12241 @cindex fast tracepoints
12242 Some targets may support @dfn{fast tracepoints}, which are inserted in
12243 a different way (such as with a jump instead of a trap), that is
12244 faster but possibly restricted in where they may be installed.
12246 @cindex static tracepoints
12247 @cindex markers, static tracepoints
12248 @cindex probing markers, static tracepoints
12249 Regular and fast tracepoints are dynamic tracing facilities, meaning
12250 that they can be used to insert tracepoints at (almost) any location
12251 in the target. Some targets may also support controlling @dfn{static
12252 tracepoints} from @value{GDBN}. With static tracing, a set of
12253 instrumentation points, also known as @dfn{markers}, are embedded in
12254 the target program, and can be activated or deactivated by name or
12255 address. These are usually placed at locations which facilitate
12256 investigating what the target is actually doing. @value{GDBN}'s
12257 support for static tracing includes being able to list instrumentation
12258 points, and attach them with @value{GDBN} defined high level
12259 tracepoints that expose the whole range of convenience of
12260 @value{GDBN}'s tracepoints support. Namely, support for collecting
12261 registers values and values of global or local (to the instrumentation
12262 point) variables; tracepoint conditions and trace state variables.
12263 The act of installing a @value{GDBN} static tracepoint on an
12264 instrumentation point, or marker, is referred to as @dfn{probing} a
12265 static tracepoint marker.
12267 @code{gdbserver} supports tracepoints on some target systems.
12268 @xref{Server,,Tracepoints support in @code{gdbserver}}.
12270 This section describes commands to set tracepoints and associated
12271 conditions and actions.
12274 * Create and Delete Tracepoints::
12275 * Enable and Disable Tracepoints::
12276 * Tracepoint Passcounts::
12277 * Tracepoint Conditions::
12278 * Trace State Variables::
12279 * Tracepoint Actions::
12280 * Listing Tracepoints::
12281 * Listing Static Tracepoint Markers::
12282 * Starting and Stopping Trace Experiments::
12283 * Tracepoint Restrictions::
12286 @node Create and Delete Tracepoints
12287 @subsection Create and Delete Tracepoints
12290 @cindex set tracepoint
12292 @item trace @var{location}
12293 The @code{trace} command is very similar to the @code{break} command.
12294 Its argument @var{location} can be any valid location.
12295 @xref{Specify Location}. The @code{trace} command defines a tracepoint,
12296 which is a point in the target program where the debugger will briefly stop,
12297 collect some data, and then allow the program to continue. Setting a tracepoint
12298 or changing its actions takes effect immediately if the remote stub
12299 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
12301 If remote stub doesn't support the @samp{InstallInTrace} feature, all
12302 these changes don't take effect until the next @code{tstart}
12303 command, and once a trace experiment is running, further changes will
12304 not have any effect until the next trace experiment starts. In addition,
12305 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
12306 address is not yet resolved. (This is similar to pending breakpoints.)
12307 Pending tracepoints are not downloaded to the target and not installed
12308 until they are resolved. The resolution of pending tracepoints requires
12309 @value{GDBN} support---when debugging with the remote target, and
12310 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
12311 tracing}), pending tracepoints can not be resolved (and downloaded to
12312 the remote stub) while @value{GDBN} is disconnected.
12314 Here are some examples of using the @code{trace} command:
12317 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
12319 (@value{GDBP}) @b{trace +2} // 2 lines forward
12321 (@value{GDBP}) @b{trace my_function} // first source line of function
12323 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
12325 (@value{GDBP}) @b{trace *0x2117c4} // an address
12329 You can abbreviate @code{trace} as @code{tr}.
12331 @item trace @var{location} if @var{cond}
12332 Set a tracepoint with condition @var{cond}; evaluate the expression
12333 @var{cond} each time the tracepoint is reached, and collect data only
12334 if the value is nonzero---that is, if @var{cond} evaluates as true.
12335 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
12336 information on tracepoint conditions.
12338 @item ftrace @var{location} [ if @var{cond} ]
12339 @cindex set fast tracepoint
12340 @cindex fast tracepoints, setting
12342 The @code{ftrace} command sets a fast tracepoint. For targets that
12343 support them, fast tracepoints will use a more efficient but possibly
12344 less general technique to trigger data collection, such as a jump
12345 instruction instead of a trap, or some sort of hardware support. It
12346 may not be possible to create a fast tracepoint at the desired
12347 location, in which case the command will exit with an explanatory
12350 @value{GDBN} handles arguments to @code{ftrace} exactly as for
12353 On 32-bit x86-architecture systems, fast tracepoints normally need to
12354 be placed at an instruction that is 5 bytes or longer, but can be
12355 placed at 4-byte instructions if the low 64K of memory of the target
12356 program is available to install trampolines. Some Unix-type systems,
12357 such as @sc{gnu}/Linux, exclude low addresses from the program's
12358 address space; but for instance with the Linux kernel it is possible
12359 to let @value{GDBN} use this area by doing a @command{sysctl} command
12360 to set the @code{mmap_min_addr} kernel parameter, as in
12363 sudo sysctl -w vm.mmap_min_addr=32768
12367 which sets the low address to 32K, which leaves plenty of room for
12368 trampolines. The minimum address should be set to a page boundary.
12370 @item strace @var{location} [ if @var{cond} ]
12371 @cindex set static tracepoint
12372 @cindex static tracepoints, setting
12373 @cindex probe static tracepoint marker
12375 The @code{strace} command sets a static tracepoint. For targets that
12376 support it, setting a static tracepoint probes a static
12377 instrumentation point, or marker, found at @var{location}. It may not
12378 be possible to set a static tracepoint at the desired location, in
12379 which case the command will exit with an explanatory message.
12381 @value{GDBN} handles arguments to @code{strace} exactly as for
12382 @code{trace}, with the addition that the user can also specify
12383 @code{-m @var{marker}} as @var{location}. This probes the marker
12384 identified by the @var{marker} string identifier. This identifier
12385 depends on the static tracepoint backend library your program is
12386 using. You can find all the marker identifiers in the @samp{ID} field
12387 of the @code{info static-tracepoint-markers} command output.
12388 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
12389 Markers}. For example, in the following small program using the UST
12395 trace_mark(ust, bar33, "str %s", "FOOBAZ");
12400 the marker id is composed of joining the first two arguments to the
12401 @code{trace_mark} call with a slash, which translates to:
12404 (@value{GDBP}) info static-tracepoint-markers
12405 Cnt Enb ID Address What
12406 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
12412 so you may probe the marker above with:
12415 (@value{GDBP}) strace -m ust/bar33
12418 Static tracepoints accept an extra collect action --- @code{collect
12419 $_sdata}. This collects arbitrary user data passed in the probe point
12420 call to the tracing library. In the UST example above, you'll see
12421 that the third argument to @code{trace_mark} is a printf-like format
12422 string. The user data is then the result of running that formating
12423 string against the following arguments. Note that @code{info
12424 static-tracepoint-markers} command output lists that format string in
12425 the @samp{Data:} field.
12427 You can inspect this data when analyzing the trace buffer, by printing
12428 the $_sdata variable like any other variable available to
12429 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
12432 @cindex last tracepoint number
12433 @cindex recent tracepoint number
12434 @cindex tracepoint number
12435 The convenience variable @code{$tpnum} records the tracepoint number
12436 of the most recently set tracepoint.
12438 @kindex delete tracepoint
12439 @cindex tracepoint deletion
12440 @item delete tracepoint @r{[}@var{num}@r{]}
12441 Permanently delete one or more tracepoints. With no argument, the
12442 default is to delete all tracepoints. Note that the regular
12443 @code{delete} command can remove tracepoints also.
12448 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
12450 (@value{GDBP}) @b{delete trace} // remove all tracepoints
12454 You can abbreviate this command as @code{del tr}.
12457 @node Enable and Disable Tracepoints
12458 @subsection Enable and Disable Tracepoints
12460 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
12463 @kindex disable tracepoint
12464 @item disable tracepoint @r{[}@var{num}@r{]}
12465 Disable tracepoint @var{num}, or all tracepoints if no argument
12466 @var{num} is given. A disabled tracepoint will have no effect during
12467 a trace experiment, but it is not forgotten. You can re-enable
12468 a disabled tracepoint using the @code{enable tracepoint} command.
12469 If the command is issued during a trace experiment and the debug target
12470 has support for disabling tracepoints during a trace experiment, then the
12471 change will be effective immediately. Otherwise, it will be applied to the
12472 next trace experiment.
12474 @kindex enable tracepoint
12475 @item enable tracepoint @r{[}@var{num}@r{]}
12476 Enable tracepoint @var{num}, or all tracepoints. If this command is
12477 issued during a trace experiment and the debug target supports enabling
12478 tracepoints during a trace experiment, then the enabled tracepoints will
12479 become effective immediately. Otherwise, they will become effective the
12480 next time a trace experiment is run.
12483 @node Tracepoint Passcounts
12484 @subsection Tracepoint Passcounts
12488 @cindex tracepoint pass count
12489 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
12490 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
12491 automatically stop a trace experiment. If a tracepoint's passcount is
12492 @var{n}, then the trace experiment will be automatically stopped on
12493 the @var{n}'th time that tracepoint is hit. If the tracepoint number
12494 @var{num} is not specified, the @code{passcount} command sets the
12495 passcount of the most recently defined tracepoint. If no passcount is
12496 given, the trace experiment will run until stopped explicitly by the
12502 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
12503 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
12505 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
12506 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
12507 (@value{GDBP}) @b{trace foo}
12508 (@value{GDBP}) @b{pass 3}
12509 (@value{GDBP}) @b{trace bar}
12510 (@value{GDBP}) @b{pass 2}
12511 (@value{GDBP}) @b{trace baz}
12512 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
12513 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
12514 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
12515 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
12519 @node Tracepoint Conditions
12520 @subsection Tracepoint Conditions
12521 @cindex conditional tracepoints
12522 @cindex tracepoint conditions
12524 The simplest sort of tracepoint collects data every time your program
12525 reaches a specified place. You can also specify a @dfn{condition} for
12526 a tracepoint. A condition is just a Boolean expression in your
12527 programming language (@pxref{Expressions, ,Expressions}). A
12528 tracepoint with a condition evaluates the expression each time your
12529 program reaches it, and data collection happens only if the condition
12532 Tracepoint conditions can be specified when a tracepoint is set, by
12533 using @samp{if} in the arguments to the @code{trace} command.
12534 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
12535 also be set or changed at any time with the @code{condition} command,
12536 just as with breakpoints.
12538 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
12539 the conditional expression itself. Instead, @value{GDBN} encodes the
12540 expression into an agent expression (@pxref{Agent Expressions})
12541 suitable for execution on the target, independently of @value{GDBN}.
12542 Global variables become raw memory locations, locals become stack
12543 accesses, and so forth.
12545 For instance, suppose you have a function that is usually called
12546 frequently, but should not be called after an error has occurred. You
12547 could use the following tracepoint command to collect data about calls
12548 of that function that happen while the error code is propagating
12549 through the program; an unconditional tracepoint could end up
12550 collecting thousands of useless trace frames that you would have to
12554 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
12557 @node Trace State Variables
12558 @subsection Trace State Variables
12559 @cindex trace state variables
12561 A @dfn{trace state variable} is a special type of variable that is
12562 created and managed by target-side code. The syntax is the same as
12563 that for GDB's convenience variables (a string prefixed with ``$''),
12564 but they are stored on the target. They must be created explicitly,
12565 using a @code{tvariable} command. They are always 64-bit signed
12568 Trace state variables are remembered by @value{GDBN}, and downloaded
12569 to the target along with tracepoint information when the trace
12570 experiment starts. There are no intrinsic limits on the number of
12571 trace state variables, beyond memory limitations of the target.
12573 @cindex convenience variables, and trace state variables
12574 Although trace state variables are managed by the target, you can use
12575 them in print commands and expressions as if they were convenience
12576 variables; @value{GDBN} will get the current value from the target
12577 while the trace experiment is running. Trace state variables share
12578 the same namespace as other ``$'' variables, which means that you
12579 cannot have trace state variables with names like @code{$23} or
12580 @code{$pc}, nor can you have a trace state variable and a convenience
12581 variable with the same name.
12585 @item tvariable $@var{name} [ = @var{expression} ]
12587 The @code{tvariable} command creates a new trace state variable named
12588 @code{$@var{name}}, and optionally gives it an initial value of
12589 @var{expression}. The @var{expression} is evaluated when this command is
12590 entered; the result will be converted to an integer if possible,
12591 otherwise @value{GDBN} will report an error. A subsequent
12592 @code{tvariable} command specifying the same name does not create a
12593 variable, but instead assigns the supplied initial value to the
12594 existing variable of that name, overwriting any previous initial
12595 value. The default initial value is 0.
12597 @item info tvariables
12598 @kindex info tvariables
12599 List all the trace state variables along with their initial values.
12600 Their current values may also be displayed, if the trace experiment is
12603 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
12604 @kindex delete tvariable
12605 Delete the given trace state variables, or all of them if no arguments
12610 @node Tracepoint Actions
12611 @subsection Tracepoint Action Lists
12615 @cindex tracepoint actions
12616 @item actions @r{[}@var{num}@r{]}
12617 This command will prompt for a list of actions to be taken when the
12618 tracepoint is hit. If the tracepoint number @var{num} is not
12619 specified, this command sets the actions for the one that was most
12620 recently defined (so that you can define a tracepoint and then say
12621 @code{actions} without bothering about its number). You specify the
12622 actions themselves on the following lines, one action at a time, and
12623 terminate the actions list with a line containing just @code{end}. So
12624 far, the only defined actions are @code{collect}, @code{teval}, and
12625 @code{while-stepping}.
12627 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
12628 Commands, ,Breakpoint Command Lists}), except that only the defined
12629 actions are allowed; any other @value{GDBN} command is rejected.
12631 @cindex remove actions from a tracepoint
12632 To remove all actions from a tracepoint, type @samp{actions @var{num}}
12633 and follow it immediately with @samp{end}.
12636 (@value{GDBP}) @b{collect @var{data}} // collect some data
12638 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
12640 (@value{GDBP}) @b{end} // signals the end of actions.
12643 In the following example, the action list begins with @code{collect}
12644 commands indicating the things to be collected when the tracepoint is
12645 hit. Then, in order to single-step and collect additional data
12646 following the tracepoint, a @code{while-stepping} command is used,
12647 followed by the list of things to be collected after each step in a
12648 sequence of single steps. The @code{while-stepping} command is
12649 terminated by its own separate @code{end} command. Lastly, the action
12650 list is terminated by an @code{end} command.
12653 (@value{GDBP}) @b{trace foo}
12654 (@value{GDBP}) @b{actions}
12655 Enter actions for tracepoint 1, one per line:
12658 > while-stepping 12
12659 > collect $pc, arr[i]
12664 @kindex collect @r{(tracepoints)}
12665 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
12666 Collect values of the given expressions when the tracepoint is hit.
12667 This command accepts a comma-separated list of any valid expressions.
12668 In addition to global, static, or local variables, the following
12669 special arguments are supported:
12673 Collect all registers.
12676 Collect all function arguments.
12679 Collect all local variables.
12682 Collect the return address. This is helpful if you want to see more
12686 Collects the number of arguments from the static probe at which the
12687 tracepoint is located.
12688 @xref{Static Probe Points}.
12690 @item $_probe_arg@var{n}
12691 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
12692 from the static probe at which the tracepoint is located.
12693 @xref{Static Probe Points}.
12696 @vindex $_sdata@r{, collect}
12697 Collect static tracepoint marker specific data. Only available for
12698 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
12699 Lists}. On the UST static tracepoints library backend, an
12700 instrumentation point resembles a @code{printf} function call. The
12701 tracing library is able to collect user specified data formatted to a
12702 character string using the format provided by the programmer that
12703 instrumented the program. Other backends have similar mechanisms.
12704 Here's an example of a UST marker call:
12707 const char master_name[] = "$your_name";
12708 trace_mark(channel1, marker1, "hello %s", master_name)
12711 In this case, collecting @code{$_sdata} collects the string
12712 @samp{hello $yourname}. When analyzing the trace buffer, you can
12713 inspect @samp{$_sdata} like any other variable available to
12717 You can give several consecutive @code{collect} commands, each one
12718 with a single argument, or one @code{collect} command with several
12719 arguments separated by commas; the effect is the same.
12721 The optional @var{mods} changes the usual handling of the arguments.
12722 @code{s} requests that pointers to chars be handled as strings, in
12723 particular collecting the contents of the memory being pointed at, up
12724 to the first zero. The upper bound is by default the value of the
12725 @code{print elements} variable; if @code{s} is followed by a decimal
12726 number, that is the upper bound instead. So for instance
12727 @samp{collect/s25 mystr} collects as many as 25 characters at
12730 The command @code{info scope} (@pxref{Symbols, info scope}) is
12731 particularly useful for figuring out what data to collect.
12733 @kindex teval @r{(tracepoints)}
12734 @item teval @var{expr1}, @var{expr2}, @dots{}
12735 Evaluate the given expressions when the tracepoint is hit. This
12736 command accepts a comma-separated list of expressions. The results
12737 are discarded, so this is mainly useful for assigning values to trace
12738 state variables (@pxref{Trace State Variables}) without adding those
12739 values to the trace buffer, as would be the case if the @code{collect}
12742 @kindex while-stepping @r{(tracepoints)}
12743 @item while-stepping @var{n}
12744 Perform @var{n} single-step instruction traces after the tracepoint,
12745 collecting new data after each step. The @code{while-stepping}
12746 command is followed by the list of what to collect while stepping
12747 (followed by its own @code{end} command):
12750 > while-stepping 12
12751 > collect $regs, myglobal
12757 Note that @code{$pc} is not automatically collected by
12758 @code{while-stepping}; you need to explicitly collect that register if
12759 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
12762 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
12763 @kindex set default-collect
12764 @cindex default collection action
12765 This variable is a list of expressions to collect at each tracepoint
12766 hit. It is effectively an additional @code{collect} action prepended
12767 to every tracepoint action list. The expressions are parsed
12768 individually for each tracepoint, so for instance a variable named
12769 @code{xyz} may be interpreted as a global for one tracepoint, and a
12770 local for another, as appropriate to the tracepoint's location.
12772 @item show default-collect
12773 @kindex show default-collect
12774 Show the list of expressions that are collected by default at each
12779 @node Listing Tracepoints
12780 @subsection Listing Tracepoints
12783 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
12784 @kindex info tp @r{[}@var{n}@dots{}@r{]}
12785 @cindex information about tracepoints
12786 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
12787 Display information about the tracepoint @var{num}. If you don't
12788 specify a tracepoint number, displays information about all the
12789 tracepoints defined so far. The format is similar to that used for
12790 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
12791 command, simply restricting itself to tracepoints.
12793 A tracepoint's listing may include additional information specific to
12798 its passcount as given by the @code{passcount @var{n}} command
12801 the state about installed on target of each location
12805 (@value{GDBP}) @b{info trace}
12806 Num Type Disp Enb Address What
12807 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
12809 collect globfoo, $regs
12814 2 tracepoint keep y <MULTIPLE>
12816 2.1 y 0x0804859c in func4 at change-loc.h:35
12817 installed on target
12818 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12819 installed on target
12820 2.3 y <PENDING> set_tracepoint
12821 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12822 not installed on target
12827 This command can be abbreviated @code{info tp}.
12830 @node Listing Static Tracepoint Markers
12831 @subsection Listing Static Tracepoint Markers
12834 @kindex info static-tracepoint-markers
12835 @cindex information about static tracepoint markers
12836 @item info static-tracepoint-markers
12837 Display information about all static tracepoint markers defined in the
12840 For each marker, the following columns are printed:
12844 An incrementing counter, output to help readability. This is not a
12847 The marker ID, as reported by the target.
12848 @item Enabled or Disabled
12849 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12850 that are not enabled.
12852 Where the marker is in your program, as a memory address.
12854 Where the marker is in the source for your program, as a file and line
12855 number. If the debug information included in the program does not
12856 allow @value{GDBN} to locate the source of the marker, this column
12857 will be left blank.
12861 In addition, the following information may be printed for each marker:
12865 User data passed to the tracing library by the marker call. In the
12866 UST backend, this is the format string passed as argument to the
12868 @item Static tracepoints probing the marker
12869 The list of static tracepoints attached to the marker.
12873 (@value{GDBP}) info static-tracepoint-markers
12874 Cnt ID Enb Address What
12875 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12876 Data: number1 %d number2 %d
12877 Probed by static tracepoints: #2
12878 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12884 @node Starting and Stopping Trace Experiments
12885 @subsection Starting and Stopping Trace Experiments
12888 @kindex tstart [ @var{notes} ]
12889 @cindex start a new trace experiment
12890 @cindex collected data discarded
12892 This command starts the trace experiment, and begins collecting data.
12893 It has the side effect of discarding all the data collected in the
12894 trace buffer during the previous trace experiment. If any arguments
12895 are supplied, they are taken as a note and stored with the trace
12896 experiment's state. The notes may be arbitrary text, and are
12897 especially useful with disconnected tracing in a multi-user context;
12898 the notes can explain what the trace is doing, supply user contact
12899 information, and so forth.
12901 @kindex tstop [ @var{notes} ]
12902 @cindex stop a running trace experiment
12904 This command stops the trace experiment. If any arguments are
12905 supplied, they are recorded with the experiment as a note. This is
12906 useful if you are stopping a trace started by someone else, for
12907 instance if the trace is interfering with the system's behavior and
12908 needs to be stopped quickly.
12910 @strong{Note}: a trace experiment and data collection may stop
12911 automatically if any tracepoint's passcount is reached
12912 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12915 @cindex status of trace data collection
12916 @cindex trace experiment, status of
12918 This command displays the status of the current trace data
12922 Here is an example of the commands we described so far:
12925 (@value{GDBP}) @b{trace gdb_c_test}
12926 (@value{GDBP}) @b{actions}
12927 Enter actions for tracepoint #1, one per line.
12928 > collect $regs,$locals,$args
12929 > while-stepping 11
12933 (@value{GDBP}) @b{tstart}
12934 [time passes @dots{}]
12935 (@value{GDBP}) @b{tstop}
12938 @anchor{disconnected tracing}
12939 @cindex disconnected tracing
12940 You can choose to continue running the trace experiment even if
12941 @value{GDBN} disconnects from the target, voluntarily or
12942 involuntarily. For commands such as @code{detach}, the debugger will
12943 ask what you want to do with the trace. But for unexpected
12944 terminations (@value{GDBN} crash, network outage), it would be
12945 unfortunate to lose hard-won trace data, so the variable
12946 @code{disconnected-tracing} lets you decide whether the trace should
12947 continue running without @value{GDBN}.
12950 @item set disconnected-tracing on
12951 @itemx set disconnected-tracing off
12952 @kindex set disconnected-tracing
12953 Choose whether a tracing run should continue to run if @value{GDBN}
12954 has disconnected from the target. Note that @code{detach} or
12955 @code{quit} will ask you directly what to do about a running trace no
12956 matter what this variable's setting, so the variable is mainly useful
12957 for handling unexpected situations, such as loss of the network.
12959 @item show disconnected-tracing
12960 @kindex show disconnected-tracing
12961 Show the current choice for disconnected tracing.
12965 When you reconnect to the target, the trace experiment may or may not
12966 still be running; it might have filled the trace buffer in the
12967 meantime, or stopped for one of the other reasons. If it is running,
12968 it will continue after reconnection.
12970 Upon reconnection, the target will upload information about the
12971 tracepoints in effect. @value{GDBN} will then compare that
12972 information to the set of tracepoints currently defined, and attempt
12973 to match them up, allowing for the possibility that the numbers may
12974 have changed due to creation and deletion in the meantime. If one of
12975 the target's tracepoints does not match any in @value{GDBN}, the
12976 debugger will create a new tracepoint, so that you have a number with
12977 which to specify that tracepoint. This matching-up process is
12978 necessarily heuristic, and it may result in useless tracepoints being
12979 created; you may simply delete them if they are of no use.
12981 @cindex circular trace buffer
12982 If your target agent supports a @dfn{circular trace buffer}, then you
12983 can run a trace experiment indefinitely without filling the trace
12984 buffer; when space runs out, the agent deletes already-collected trace
12985 frames, oldest first, until there is enough room to continue
12986 collecting. This is especially useful if your tracepoints are being
12987 hit too often, and your trace gets terminated prematurely because the
12988 buffer is full. To ask for a circular trace buffer, simply set
12989 @samp{circular-trace-buffer} to on. You can set this at any time,
12990 including during tracing; if the agent can do it, it will change
12991 buffer handling on the fly, otherwise it will not take effect until
12995 @item set circular-trace-buffer on
12996 @itemx set circular-trace-buffer off
12997 @kindex set circular-trace-buffer
12998 Choose whether a tracing run should use a linear or circular buffer
12999 for trace data. A linear buffer will not lose any trace data, but may
13000 fill up prematurely, while a circular buffer will discard old trace
13001 data, but it will have always room for the latest tracepoint hits.
13003 @item show circular-trace-buffer
13004 @kindex show circular-trace-buffer
13005 Show the current choice for the trace buffer. Note that this may not
13006 match the agent's current buffer handling, nor is it guaranteed to
13007 match the setting that might have been in effect during a past run,
13008 for instance if you are looking at frames from a trace file.
13013 @item set trace-buffer-size @var{n}
13014 @itemx set trace-buffer-size unlimited
13015 @kindex set trace-buffer-size
13016 Request that the target use a trace buffer of @var{n} bytes. Not all
13017 targets will honor the request; they may have a compiled-in size for
13018 the trace buffer, or some other limitation. Set to a value of
13019 @code{unlimited} or @code{-1} to let the target use whatever size it
13020 likes. This is also the default.
13022 @item show trace-buffer-size
13023 @kindex show trace-buffer-size
13024 Show the current requested size for the trace buffer. Note that this
13025 will only match the actual size if the target supports size-setting,
13026 and was able to handle the requested size. For instance, if the
13027 target can only change buffer size between runs, this variable will
13028 not reflect the change until the next run starts. Use @code{tstatus}
13029 to get a report of the actual buffer size.
13033 @item set trace-user @var{text}
13034 @kindex set trace-user
13036 @item show trace-user
13037 @kindex show trace-user
13039 @item set trace-notes @var{text}
13040 @kindex set trace-notes
13041 Set the trace run's notes.
13043 @item show trace-notes
13044 @kindex show trace-notes
13045 Show the trace run's notes.
13047 @item set trace-stop-notes @var{text}
13048 @kindex set trace-stop-notes
13049 Set the trace run's stop notes. The handling of the note is as for
13050 @code{tstop} arguments; the set command is convenient way to fix a
13051 stop note that is mistaken or incomplete.
13053 @item show trace-stop-notes
13054 @kindex show trace-stop-notes
13055 Show the trace run's stop notes.
13059 @node Tracepoint Restrictions
13060 @subsection Tracepoint Restrictions
13062 @cindex tracepoint restrictions
13063 There are a number of restrictions on the use of tracepoints. As
13064 described above, tracepoint data gathering occurs on the target
13065 without interaction from @value{GDBN}. Thus the full capabilities of
13066 the debugger are not available during data gathering, and then at data
13067 examination time, you will be limited by only having what was
13068 collected. The following items describe some common problems, but it
13069 is not exhaustive, and you may run into additional difficulties not
13075 Tracepoint expressions are intended to gather objects (lvalues). Thus
13076 the full flexibility of GDB's expression evaluator is not available.
13077 You cannot call functions, cast objects to aggregate types, access
13078 convenience variables or modify values (except by assignment to trace
13079 state variables). Some language features may implicitly call
13080 functions (for instance Objective-C fields with accessors), and therefore
13081 cannot be collected either.
13084 Collection of local variables, either individually or in bulk with
13085 @code{$locals} or @code{$args}, during @code{while-stepping} may
13086 behave erratically. The stepping action may enter a new scope (for
13087 instance by stepping into a function), or the location of the variable
13088 may change (for instance it is loaded into a register). The
13089 tracepoint data recorded uses the location information for the
13090 variables that is correct for the tracepoint location. When the
13091 tracepoint is created, it is not possible, in general, to determine
13092 where the steps of a @code{while-stepping} sequence will advance the
13093 program---particularly if a conditional branch is stepped.
13096 Collection of an incompletely-initialized or partially-destroyed object
13097 may result in something that @value{GDBN} cannot display, or displays
13098 in a misleading way.
13101 When @value{GDBN} displays a pointer to character it automatically
13102 dereferences the pointer to also display characters of the string
13103 being pointed to. However, collecting the pointer during tracing does
13104 not automatically collect the string. You need to explicitly
13105 dereference the pointer and provide size information if you want to
13106 collect not only the pointer, but the memory pointed to. For example,
13107 @code{*ptr@@50} can be used to collect the 50 element array pointed to
13111 It is not possible to collect a complete stack backtrace at a
13112 tracepoint. Instead, you may collect the registers and a few hundred
13113 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
13114 (adjust to use the name of the actual stack pointer register on your
13115 target architecture, and the amount of stack you wish to capture).
13116 Then the @code{backtrace} command will show a partial backtrace when
13117 using a trace frame. The number of stack frames that can be examined
13118 depends on the sizes of the frames in the collected stack. Note that
13119 if you ask for a block so large that it goes past the bottom of the
13120 stack, the target agent may report an error trying to read from an
13124 If you do not collect registers at a tracepoint, @value{GDBN} can
13125 infer that the value of @code{$pc} must be the same as the address of
13126 the tracepoint and use that when you are looking at a trace frame
13127 for that tracepoint. However, this cannot work if the tracepoint has
13128 multiple locations (for instance if it was set in a function that was
13129 inlined), or if it has a @code{while-stepping} loop. In those cases
13130 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
13135 @node Analyze Collected Data
13136 @section Using the Collected Data
13138 After the tracepoint experiment ends, you use @value{GDBN} commands
13139 for examining the trace data. The basic idea is that each tracepoint
13140 collects a trace @dfn{snapshot} every time it is hit and another
13141 snapshot every time it single-steps. All these snapshots are
13142 consecutively numbered from zero and go into a buffer, and you can
13143 examine them later. The way you examine them is to @dfn{focus} on a
13144 specific trace snapshot. When the remote stub is focused on a trace
13145 snapshot, it will respond to all @value{GDBN} requests for memory and
13146 registers by reading from the buffer which belongs to that snapshot,
13147 rather than from @emph{real} memory or registers of the program being
13148 debugged. This means that @strong{all} @value{GDBN} commands
13149 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
13150 behave as if we were currently debugging the program state as it was
13151 when the tracepoint occurred. Any requests for data that are not in
13152 the buffer will fail.
13155 * tfind:: How to select a trace snapshot
13156 * tdump:: How to display all data for a snapshot
13157 * save tracepoints:: How to save tracepoints for a future run
13161 @subsection @code{tfind @var{n}}
13164 @cindex select trace snapshot
13165 @cindex find trace snapshot
13166 The basic command for selecting a trace snapshot from the buffer is
13167 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
13168 counting from zero. If no argument @var{n} is given, the next
13169 snapshot is selected.
13171 Here are the various forms of using the @code{tfind} command.
13175 Find the first snapshot in the buffer. This is a synonym for
13176 @code{tfind 0} (since 0 is the number of the first snapshot).
13179 Stop debugging trace snapshots, resume @emph{live} debugging.
13182 Same as @samp{tfind none}.
13185 No argument means find the next trace snapshot.
13188 Find the previous trace snapshot before the current one. This permits
13189 retracing earlier steps.
13191 @item tfind tracepoint @var{num}
13192 Find the next snapshot associated with tracepoint @var{num}. Search
13193 proceeds forward from the last examined trace snapshot. If no
13194 argument @var{num} is given, it means find the next snapshot collected
13195 for the same tracepoint as the current snapshot.
13197 @item tfind pc @var{addr}
13198 Find the next snapshot associated with the value @var{addr} of the
13199 program counter. Search proceeds forward from the last examined trace
13200 snapshot. If no argument @var{addr} is given, it means find the next
13201 snapshot with the same value of PC as the current snapshot.
13203 @item tfind outside @var{addr1}, @var{addr2}
13204 Find the next snapshot whose PC is outside the given range of
13205 addresses (exclusive).
13207 @item tfind range @var{addr1}, @var{addr2}
13208 Find the next snapshot whose PC is between @var{addr1} and
13209 @var{addr2} (inclusive).
13211 @item tfind line @r{[}@var{file}:@r{]}@var{n}
13212 Find the next snapshot associated with the source line @var{n}. If
13213 the optional argument @var{file} is given, refer to line @var{n} in
13214 that source file. Search proceeds forward from the last examined
13215 trace snapshot. If no argument @var{n} is given, it means find the
13216 next line other than the one currently being examined; thus saying
13217 @code{tfind line} repeatedly can appear to have the same effect as
13218 stepping from line to line in a @emph{live} debugging session.
13221 The default arguments for the @code{tfind} commands are specifically
13222 designed to make it easy to scan through the trace buffer. For
13223 instance, @code{tfind} with no argument selects the next trace
13224 snapshot, and @code{tfind -} with no argument selects the previous
13225 trace snapshot. So, by giving one @code{tfind} command, and then
13226 simply hitting @key{RET} repeatedly you can examine all the trace
13227 snapshots in order. Or, by saying @code{tfind -} and then hitting
13228 @key{RET} repeatedly you can examine the snapshots in reverse order.
13229 The @code{tfind line} command with no argument selects the snapshot
13230 for the next source line executed. The @code{tfind pc} command with
13231 no argument selects the next snapshot with the same program counter
13232 (PC) as the current frame. The @code{tfind tracepoint} command with
13233 no argument selects the next trace snapshot collected by the same
13234 tracepoint as the current one.
13236 In addition to letting you scan through the trace buffer manually,
13237 these commands make it easy to construct @value{GDBN} scripts that
13238 scan through the trace buffer and print out whatever collected data
13239 you are interested in. Thus, if we want to examine the PC, FP, and SP
13240 registers from each trace frame in the buffer, we can say this:
13243 (@value{GDBP}) @b{tfind start}
13244 (@value{GDBP}) @b{while ($trace_frame != -1)}
13245 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
13246 $trace_frame, $pc, $sp, $fp
13250 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
13251 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
13252 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
13253 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
13254 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
13255 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
13256 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
13257 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
13258 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
13259 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
13260 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
13263 Or, if we want to examine the variable @code{X} at each source line in
13267 (@value{GDBP}) @b{tfind start}
13268 (@value{GDBP}) @b{while ($trace_frame != -1)}
13269 > printf "Frame %d, X == %d\n", $trace_frame, X
13279 @subsection @code{tdump}
13281 @cindex dump all data collected at tracepoint
13282 @cindex tracepoint data, display
13284 This command takes no arguments. It prints all the data collected at
13285 the current trace snapshot.
13288 (@value{GDBP}) @b{trace 444}
13289 (@value{GDBP}) @b{actions}
13290 Enter actions for tracepoint #2, one per line:
13291 > collect $regs, $locals, $args, gdb_long_test
13294 (@value{GDBP}) @b{tstart}
13296 (@value{GDBP}) @b{tfind line 444}
13297 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
13299 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
13301 (@value{GDBP}) @b{tdump}
13302 Data collected at tracepoint 2, trace frame 1:
13303 d0 0xc4aa0085 -995491707
13307 d4 0x71aea3d 119204413
13310 d7 0x380035 3670069
13311 a0 0x19e24a 1696330
13312 a1 0x3000668 50333288
13314 a3 0x322000 3284992
13315 a4 0x3000698 50333336
13316 a5 0x1ad3cc 1758156
13317 fp 0x30bf3c 0x30bf3c
13318 sp 0x30bf34 0x30bf34
13320 pc 0x20b2c8 0x20b2c8
13324 p = 0x20e5b4 "gdb-test"
13331 gdb_long_test = 17 '\021'
13336 @code{tdump} works by scanning the tracepoint's current collection
13337 actions and printing the value of each expression listed. So
13338 @code{tdump} can fail, if after a run, you change the tracepoint's
13339 actions to mention variables that were not collected during the run.
13341 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
13342 uses the collected value of @code{$pc} to distinguish between trace
13343 frames that were collected at the tracepoint hit, and frames that were
13344 collected while stepping. This allows it to correctly choose whether
13345 to display the basic list of collections, or the collections from the
13346 body of the while-stepping loop. However, if @code{$pc} was not collected,
13347 then @code{tdump} will always attempt to dump using the basic collection
13348 list, and may fail if a while-stepping frame does not include all the
13349 same data that is collected at the tracepoint hit.
13350 @c This is getting pretty arcane, example would be good.
13352 @node save tracepoints
13353 @subsection @code{save tracepoints @var{filename}}
13354 @kindex save tracepoints
13355 @kindex save-tracepoints
13356 @cindex save tracepoints for future sessions
13358 This command saves all current tracepoint definitions together with
13359 their actions and passcounts, into a file @file{@var{filename}}
13360 suitable for use in a later debugging session. To read the saved
13361 tracepoint definitions, use the @code{source} command (@pxref{Command
13362 Files}). The @w{@code{save-tracepoints}} command is a deprecated
13363 alias for @w{@code{save tracepoints}}
13365 @node Tracepoint Variables
13366 @section Convenience Variables for Tracepoints
13367 @cindex tracepoint variables
13368 @cindex convenience variables for tracepoints
13371 @vindex $trace_frame
13372 @item (int) $trace_frame
13373 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
13374 snapshot is selected.
13376 @vindex $tracepoint
13377 @item (int) $tracepoint
13378 The tracepoint for the current trace snapshot.
13380 @vindex $trace_line
13381 @item (int) $trace_line
13382 The line number for the current trace snapshot.
13384 @vindex $trace_file
13385 @item (char []) $trace_file
13386 The source file for the current trace snapshot.
13388 @vindex $trace_func
13389 @item (char []) $trace_func
13390 The name of the function containing @code{$tracepoint}.
13393 Note: @code{$trace_file} is not suitable for use in @code{printf},
13394 use @code{output} instead.
13396 Here's a simple example of using these convenience variables for
13397 stepping through all the trace snapshots and printing some of their
13398 data. Note that these are not the same as trace state variables,
13399 which are managed by the target.
13402 (@value{GDBP}) @b{tfind start}
13404 (@value{GDBP}) @b{while $trace_frame != -1}
13405 > output $trace_file
13406 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
13412 @section Using Trace Files
13413 @cindex trace files
13415 In some situations, the target running a trace experiment may no
13416 longer be available; perhaps it crashed, or the hardware was needed
13417 for a different activity. To handle these cases, you can arrange to
13418 dump the trace data into a file, and later use that file as a source
13419 of trace data, via the @code{target tfile} command.
13424 @item tsave [ -r ] @var{filename}
13425 @itemx tsave [-ctf] @var{dirname}
13426 Save the trace data to @var{filename}. By default, this command
13427 assumes that @var{filename} refers to the host filesystem, so if
13428 necessary @value{GDBN} will copy raw trace data up from the target and
13429 then save it. If the target supports it, you can also supply the
13430 optional argument @code{-r} (``remote'') to direct the target to save
13431 the data directly into @var{filename} in its own filesystem, which may be
13432 more efficient if the trace buffer is very large. (Note, however, that
13433 @code{target tfile} can only read from files accessible to the host.)
13434 By default, this command will save trace frame in tfile format.
13435 You can supply the optional argument @code{-ctf} to save date in CTF
13436 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
13437 that can be shared by multiple debugging and tracing tools. Please go to
13438 @indicateurl{http://www.efficios.com/ctf} to get more information.
13440 @kindex target tfile
13444 @item target tfile @var{filename}
13445 @itemx target ctf @var{dirname}
13446 Use the file named @var{filename} or directory named @var{dirname} as
13447 a source of trace data. Commands that examine data work as they do with
13448 a live target, but it is not possible to run any new trace experiments.
13449 @code{tstatus} will report the state of the trace run at the moment
13450 the data was saved, as well as the current trace frame you are examining.
13451 Both @var{filename} and @var{dirname} must be on a filesystem accessible to
13455 (@value{GDBP}) target ctf ctf.ctf
13456 (@value{GDBP}) tfind
13457 Found trace frame 0, tracepoint 2
13458 39 ++a; /* set tracepoint 1 here */
13459 (@value{GDBP}) tdump
13460 Data collected at tracepoint 2, trace frame 0:
13464 c = @{"123", "456", "789", "123", "456", "789"@}
13465 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
13473 @chapter Debugging Programs That Use Overlays
13476 If your program is too large to fit completely in your target system's
13477 memory, you can sometimes use @dfn{overlays} to work around this
13478 problem. @value{GDBN} provides some support for debugging programs that
13482 * How Overlays Work:: A general explanation of overlays.
13483 * Overlay Commands:: Managing overlays in @value{GDBN}.
13484 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
13485 mapped by asking the inferior.
13486 * Overlay Sample Program:: A sample program using overlays.
13489 @node How Overlays Work
13490 @section How Overlays Work
13491 @cindex mapped overlays
13492 @cindex unmapped overlays
13493 @cindex load address, overlay's
13494 @cindex mapped address
13495 @cindex overlay area
13497 Suppose you have a computer whose instruction address space is only 64
13498 kilobytes long, but which has much more memory which can be accessed by
13499 other means: special instructions, segment registers, or memory
13500 management hardware, for example. Suppose further that you want to
13501 adapt a program which is larger than 64 kilobytes to run on this system.
13503 One solution is to identify modules of your program which are relatively
13504 independent, and need not call each other directly; call these modules
13505 @dfn{overlays}. Separate the overlays from the main program, and place
13506 their machine code in the larger memory. Place your main program in
13507 instruction memory, but leave at least enough space there to hold the
13508 largest overlay as well.
13510 Now, to call a function located in an overlay, you must first copy that
13511 overlay's machine code from the large memory into the space set aside
13512 for it in the instruction memory, and then jump to its entry point
13515 @c NB: In the below the mapped area's size is greater or equal to the
13516 @c size of all overlays. This is intentional to remind the developer
13517 @c that overlays don't necessarily need to be the same size.
13521 Data Instruction Larger
13522 Address Space Address Space Address Space
13523 +-----------+ +-----------+ +-----------+
13525 +-----------+ +-----------+ +-----------+<-- overlay 1
13526 | program | | main | .----| overlay 1 | load address
13527 | variables | | program | | +-----------+
13528 | and heap | | | | | |
13529 +-----------+ | | | +-----------+<-- overlay 2
13530 | | +-----------+ | | | load address
13531 +-----------+ | | | .-| overlay 2 |
13533 mapped --->+-----------+ | | +-----------+
13534 address | | | | | |
13535 | overlay | <-' | | |
13536 | area | <---' +-----------+<-- overlay 3
13537 | | <---. | | load address
13538 +-----------+ `--| overlay 3 |
13545 @anchor{A code overlay}A code overlay
13549 The diagram (@pxref{A code overlay}) shows a system with separate data
13550 and instruction address spaces. To map an overlay, the program copies
13551 its code from the larger address space to the instruction address space.
13552 Since the overlays shown here all use the same mapped address, only one
13553 may be mapped at a time. For a system with a single address space for
13554 data and instructions, the diagram would be similar, except that the
13555 program variables and heap would share an address space with the main
13556 program and the overlay area.
13558 An overlay loaded into instruction memory and ready for use is called a
13559 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
13560 instruction memory. An overlay not present (or only partially present)
13561 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
13562 is its address in the larger memory. The mapped address is also called
13563 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
13564 called the @dfn{load memory address}, or @dfn{LMA}.
13566 Unfortunately, overlays are not a completely transparent way to adapt a
13567 program to limited instruction memory. They introduce a new set of
13568 global constraints you must keep in mind as you design your program:
13573 Before calling or returning to a function in an overlay, your program
13574 must make sure that overlay is actually mapped. Otherwise, the call or
13575 return will transfer control to the right address, but in the wrong
13576 overlay, and your program will probably crash.
13579 If the process of mapping an overlay is expensive on your system, you
13580 will need to choose your overlays carefully to minimize their effect on
13581 your program's performance.
13584 The executable file you load onto your system must contain each
13585 overlay's instructions, appearing at the overlay's load address, not its
13586 mapped address. However, each overlay's instructions must be relocated
13587 and its symbols defined as if the overlay were at its mapped address.
13588 You can use GNU linker scripts to specify different load and relocation
13589 addresses for pieces of your program; see @ref{Overlay Description,,,
13590 ld.info, Using ld: the GNU linker}.
13593 The procedure for loading executable files onto your system must be able
13594 to load their contents into the larger address space as well as the
13595 instruction and data spaces.
13599 The overlay system described above is rather simple, and could be
13600 improved in many ways:
13605 If your system has suitable bank switch registers or memory management
13606 hardware, you could use those facilities to make an overlay's load area
13607 contents simply appear at their mapped address in instruction space.
13608 This would probably be faster than copying the overlay to its mapped
13609 area in the usual way.
13612 If your overlays are small enough, you could set aside more than one
13613 overlay area, and have more than one overlay mapped at a time.
13616 You can use overlays to manage data, as well as instructions. In
13617 general, data overlays are even less transparent to your design than
13618 code overlays: whereas code overlays only require care when you call or
13619 return to functions, data overlays require care every time you access
13620 the data. Also, if you change the contents of a data overlay, you
13621 must copy its contents back out to its load address before you can copy a
13622 different data overlay into the same mapped area.
13627 @node Overlay Commands
13628 @section Overlay Commands
13630 To use @value{GDBN}'s overlay support, each overlay in your program must
13631 correspond to a separate section of the executable file. The section's
13632 virtual memory address and load memory address must be the overlay's
13633 mapped and load addresses. Identifying overlays with sections allows
13634 @value{GDBN} to determine the appropriate address of a function or
13635 variable, depending on whether the overlay is mapped or not.
13637 @value{GDBN}'s overlay commands all start with the word @code{overlay};
13638 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
13643 Disable @value{GDBN}'s overlay support. When overlay support is
13644 disabled, @value{GDBN} assumes that all functions and variables are
13645 always present at their mapped addresses. By default, @value{GDBN}'s
13646 overlay support is disabled.
13648 @item overlay manual
13649 @cindex manual overlay debugging
13650 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
13651 relies on you to tell it which overlays are mapped, and which are not,
13652 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
13653 commands described below.
13655 @item overlay map-overlay @var{overlay}
13656 @itemx overlay map @var{overlay}
13657 @cindex map an overlay
13658 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
13659 be the name of the object file section containing the overlay. When an
13660 overlay is mapped, @value{GDBN} assumes it can find the overlay's
13661 functions and variables at their mapped addresses. @value{GDBN} assumes
13662 that any other overlays whose mapped ranges overlap that of
13663 @var{overlay} are now unmapped.
13665 @item overlay unmap-overlay @var{overlay}
13666 @itemx overlay unmap @var{overlay}
13667 @cindex unmap an overlay
13668 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
13669 must be the name of the object file section containing the overlay.
13670 When an overlay is unmapped, @value{GDBN} assumes it can find the
13671 overlay's functions and variables at their load addresses.
13674 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
13675 consults a data structure the overlay manager maintains in the inferior
13676 to see which overlays are mapped. For details, see @ref{Automatic
13677 Overlay Debugging}.
13679 @item overlay load-target
13680 @itemx overlay load
13681 @cindex reloading the overlay table
13682 Re-read the overlay table from the inferior. Normally, @value{GDBN}
13683 re-reads the table @value{GDBN} automatically each time the inferior
13684 stops, so this command should only be necessary if you have changed the
13685 overlay mapping yourself using @value{GDBN}. This command is only
13686 useful when using automatic overlay debugging.
13688 @item overlay list-overlays
13689 @itemx overlay list
13690 @cindex listing mapped overlays
13691 Display a list of the overlays currently mapped, along with their mapped
13692 addresses, load addresses, and sizes.
13696 Normally, when @value{GDBN} prints a code address, it includes the name
13697 of the function the address falls in:
13700 (@value{GDBP}) print main
13701 $3 = @{int ()@} 0x11a0 <main>
13704 When overlay debugging is enabled, @value{GDBN} recognizes code in
13705 unmapped overlays, and prints the names of unmapped functions with
13706 asterisks around them. For example, if @code{foo} is a function in an
13707 unmapped overlay, @value{GDBN} prints it this way:
13710 (@value{GDBP}) overlay list
13711 No sections are mapped.
13712 (@value{GDBP}) print foo
13713 $5 = @{int (int)@} 0x100000 <*foo*>
13716 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
13720 (@value{GDBP}) overlay list
13721 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
13722 mapped at 0x1016 - 0x104a
13723 (@value{GDBP}) print foo
13724 $6 = @{int (int)@} 0x1016 <foo>
13727 When overlay debugging is enabled, @value{GDBN} can find the correct
13728 address for functions and variables in an overlay, whether or not the
13729 overlay is mapped. This allows most @value{GDBN} commands, like
13730 @code{break} and @code{disassemble}, to work normally, even on unmapped
13731 code. However, @value{GDBN}'s breakpoint support has some limitations:
13735 @cindex breakpoints in overlays
13736 @cindex overlays, setting breakpoints in
13737 You can set breakpoints in functions in unmapped overlays, as long as
13738 @value{GDBN} can write to the overlay at its load address.
13740 @value{GDBN} can not set hardware or simulator-based breakpoints in
13741 unmapped overlays. However, if you set a breakpoint at the end of your
13742 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
13743 you are using manual overlay management), @value{GDBN} will re-set its
13744 breakpoints properly.
13748 @node Automatic Overlay Debugging
13749 @section Automatic Overlay Debugging
13750 @cindex automatic overlay debugging
13752 @value{GDBN} can automatically track which overlays are mapped and which
13753 are not, given some simple co-operation from the overlay manager in the
13754 inferior. If you enable automatic overlay debugging with the
13755 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
13756 looks in the inferior's memory for certain variables describing the
13757 current state of the overlays.
13759 Here are the variables your overlay manager must define to support
13760 @value{GDBN}'s automatic overlay debugging:
13764 @item @code{_ovly_table}:
13765 This variable must be an array of the following structures:
13770 /* The overlay's mapped address. */
13773 /* The size of the overlay, in bytes. */
13774 unsigned long size;
13776 /* The overlay's load address. */
13779 /* Non-zero if the overlay is currently mapped;
13781 unsigned long mapped;
13785 @item @code{_novlys}:
13786 This variable must be a four-byte signed integer, holding the total
13787 number of elements in @code{_ovly_table}.
13791 To decide whether a particular overlay is mapped or not, @value{GDBN}
13792 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
13793 @code{lma} members equal the VMA and LMA of the overlay's section in the
13794 executable file. When @value{GDBN} finds a matching entry, it consults
13795 the entry's @code{mapped} member to determine whether the overlay is
13798 In addition, your overlay manager may define a function called
13799 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
13800 will silently set a breakpoint there. If the overlay manager then
13801 calls this function whenever it has changed the overlay table, this
13802 will enable @value{GDBN} to accurately keep track of which overlays
13803 are in program memory, and update any breakpoints that may be set
13804 in overlays. This will allow breakpoints to work even if the
13805 overlays are kept in ROM or other non-writable memory while they
13806 are not being executed.
13808 @node Overlay Sample Program
13809 @section Overlay Sample Program
13810 @cindex overlay example program
13812 When linking a program which uses overlays, you must place the overlays
13813 at their load addresses, while relocating them to run at their mapped
13814 addresses. To do this, you must write a linker script (@pxref{Overlay
13815 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13816 since linker scripts are specific to a particular host system, target
13817 architecture, and target memory layout, this manual cannot provide
13818 portable sample code demonstrating @value{GDBN}'s overlay support.
13820 However, the @value{GDBN} source distribution does contain an overlaid
13821 program, with linker scripts for a few systems, as part of its test
13822 suite. The program consists of the following files from
13823 @file{gdb/testsuite/gdb.base}:
13827 The main program file.
13829 A simple overlay manager, used by @file{overlays.c}.
13834 Overlay modules, loaded and used by @file{overlays.c}.
13837 Linker scripts for linking the test program on the @code{d10v-elf}
13838 and @code{m32r-elf} targets.
13841 You can build the test program using the @code{d10v-elf} GCC
13842 cross-compiler like this:
13845 $ d10v-elf-gcc -g -c overlays.c
13846 $ d10v-elf-gcc -g -c ovlymgr.c
13847 $ d10v-elf-gcc -g -c foo.c
13848 $ d10v-elf-gcc -g -c bar.c
13849 $ d10v-elf-gcc -g -c baz.c
13850 $ d10v-elf-gcc -g -c grbx.c
13851 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13852 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13855 The build process is identical for any other architecture, except that
13856 you must substitute the appropriate compiler and linker script for the
13857 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13861 @chapter Using @value{GDBN} with Different Languages
13864 Although programming languages generally have common aspects, they are
13865 rarely expressed in the same manner. For instance, in ANSI C,
13866 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13867 Modula-2, it is accomplished by @code{p^}. Values can also be
13868 represented (and displayed) differently. Hex numbers in C appear as
13869 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13871 @cindex working language
13872 Language-specific information is built into @value{GDBN} for some languages,
13873 allowing you to express operations like the above in your program's
13874 native language, and allowing @value{GDBN} to output values in a manner
13875 consistent with the syntax of your program's native language. The
13876 language you use to build expressions is called the @dfn{working
13880 * Setting:: Switching between source languages
13881 * Show:: Displaying the language
13882 * Checks:: Type and range checks
13883 * Supported Languages:: Supported languages
13884 * Unsupported Languages:: Unsupported languages
13888 @section Switching Between Source Languages
13890 There are two ways to control the working language---either have @value{GDBN}
13891 set it automatically, or select it manually yourself. You can use the
13892 @code{set language} command for either purpose. On startup, @value{GDBN}
13893 defaults to setting the language automatically. The working language is
13894 used to determine how expressions you type are interpreted, how values
13897 In addition to the working language, every source file that
13898 @value{GDBN} knows about has its own working language. For some object
13899 file formats, the compiler might indicate which language a particular
13900 source file is in. However, most of the time @value{GDBN} infers the
13901 language from the name of the file. The language of a source file
13902 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13903 show each frame appropriately for its own language. There is no way to
13904 set the language of a source file from within @value{GDBN}, but you can
13905 set the language associated with a filename extension. @xref{Show, ,
13906 Displaying the Language}.
13908 This is most commonly a problem when you use a program, such
13909 as @code{cfront} or @code{f2c}, that generates C but is written in
13910 another language. In that case, make the
13911 program use @code{#line} directives in its C output; that way
13912 @value{GDBN} will know the correct language of the source code of the original
13913 program, and will display that source code, not the generated C code.
13916 * Filenames:: Filename extensions and languages.
13917 * Manually:: Setting the working language manually
13918 * Automatically:: Having @value{GDBN} infer the source language
13922 @subsection List of Filename Extensions and Languages
13924 If a source file name ends in one of the following extensions, then
13925 @value{GDBN} infers that its language is the one indicated.
13943 C@t{++} source file
13949 Objective-C source file
13953 Fortran source file
13956 Modula-2 source file
13960 Assembler source file. This actually behaves almost like C, but
13961 @value{GDBN} does not skip over function prologues when stepping.
13964 In addition, you may set the language associated with a filename
13965 extension. @xref{Show, , Displaying the Language}.
13968 @subsection Setting the Working Language
13970 If you allow @value{GDBN} to set the language automatically,
13971 expressions are interpreted the same way in your debugging session and
13974 @kindex set language
13975 If you wish, you may set the language manually. To do this, issue the
13976 command @samp{set language @var{lang}}, where @var{lang} is the name of
13977 a language, such as
13978 @code{c} or @code{modula-2}.
13979 For a list of the supported languages, type @samp{set language}.
13981 Setting the language manually prevents @value{GDBN} from updating the working
13982 language automatically. This can lead to confusion if you try
13983 to debug a program when the working language is not the same as the
13984 source language, when an expression is acceptable to both
13985 languages---but means different things. For instance, if the current
13986 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13994 might not have the effect you intended. In C, this means to add
13995 @code{b} and @code{c} and place the result in @code{a}. The result
13996 printed would be the value of @code{a}. In Modula-2, this means to compare
13997 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13999 @node Automatically
14000 @subsection Having @value{GDBN} Infer the Source Language
14002 To have @value{GDBN} set the working language automatically, use
14003 @samp{set language local} or @samp{set language auto}. @value{GDBN}
14004 then infers the working language. That is, when your program stops in a
14005 frame (usually by encountering a breakpoint), @value{GDBN} sets the
14006 working language to the language recorded for the function in that
14007 frame. If the language for a frame is unknown (that is, if the function
14008 or block corresponding to the frame was defined in a source file that
14009 does not have a recognized extension), the current working language is
14010 not changed, and @value{GDBN} issues a warning.
14012 This may not seem necessary for most programs, which are written
14013 entirely in one source language. However, program modules and libraries
14014 written in one source language can be used by a main program written in
14015 a different source language. Using @samp{set language auto} in this
14016 case frees you from having to set the working language manually.
14019 @section Displaying the Language
14021 The following commands help you find out which language is the
14022 working language, and also what language source files were written in.
14025 @item show language
14026 @anchor{show language}
14027 @kindex show language
14028 Display the current working language. This is the
14029 language you can use with commands such as @code{print} to
14030 build and compute expressions that may involve variables in your program.
14033 @kindex info frame@r{, show the source language}
14034 Display the source language for this frame. This language becomes the
14035 working language if you use an identifier from this frame.
14036 @xref{Frame Info, ,Information about a Frame}, to identify the other
14037 information listed here.
14040 @kindex info source@r{, show the source language}
14041 Display the source language of this source file.
14042 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
14043 information listed here.
14046 In unusual circumstances, you may have source files with extensions
14047 not in the standard list. You can then set the extension associated
14048 with a language explicitly:
14051 @item set extension-language @var{ext} @var{language}
14052 @kindex set extension-language
14053 Tell @value{GDBN} that source files with extension @var{ext} are to be
14054 assumed as written in the source language @var{language}.
14056 @item info extensions
14057 @kindex info extensions
14058 List all the filename extensions and the associated languages.
14062 @section Type and Range Checking
14064 Some languages are designed to guard you against making seemingly common
14065 errors through a series of compile- and run-time checks. These include
14066 checking the type of arguments to functions and operators and making
14067 sure mathematical overflows are caught at run time. Checks such as
14068 these help to ensure a program's correctness once it has been compiled
14069 by eliminating type mismatches and providing active checks for range
14070 errors when your program is running.
14072 By default @value{GDBN} checks for these errors according to the
14073 rules of the current source language. Although @value{GDBN} does not check
14074 the statements in your program, it can check expressions entered directly
14075 into @value{GDBN} for evaluation via the @code{print} command, for example.
14078 * Type Checking:: An overview of type checking
14079 * Range Checking:: An overview of range checking
14082 @cindex type checking
14083 @cindex checks, type
14084 @node Type Checking
14085 @subsection An Overview of Type Checking
14087 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
14088 arguments to operators and functions have to be of the correct type,
14089 otherwise an error occurs. These checks prevent type mismatch
14090 errors from ever causing any run-time problems. For example,
14093 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
14095 (@value{GDBP}) print obj.my_method (0)
14098 (@value{GDBP}) print obj.my_method (0x1234)
14099 Cannot resolve method klass::my_method to any overloaded instance
14102 The second example fails because in C@t{++} the integer constant
14103 @samp{0x1234} is not type-compatible with the pointer parameter type.
14105 For the expressions you use in @value{GDBN} commands, you can tell
14106 @value{GDBN} to not enforce strict type checking or
14107 to treat any mismatches as errors and abandon the expression;
14108 When type checking is disabled, @value{GDBN} successfully evaluates
14109 expressions like the second example above.
14111 Even if type checking is off, there may be other reasons
14112 related to type that prevent @value{GDBN} from evaluating an expression.
14113 For instance, @value{GDBN} does not know how to add an @code{int} and
14114 a @code{struct foo}. These particular type errors have nothing to do
14115 with the language in use and usually arise from expressions which make
14116 little sense to evaluate anyway.
14118 @value{GDBN} provides some additional commands for controlling type checking:
14120 @kindex set check type
14121 @kindex show check type
14123 @item set check type on
14124 @itemx set check type off
14125 Set strict type checking on or off. If any type mismatches occur in
14126 evaluating an expression while type checking is on, @value{GDBN} prints a
14127 message and aborts evaluation of the expression.
14129 @item show check type
14130 Show the current setting of type checking and whether @value{GDBN}
14131 is enforcing strict type checking rules.
14134 @cindex range checking
14135 @cindex checks, range
14136 @node Range Checking
14137 @subsection An Overview of Range Checking
14139 In some languages (such as Modula-2), it is an error to exceed the
14140 bounds of a type; this is enforced with run-time checks. Such range
14141 checking is meant to ensure program correctness by making sure
14142 computations do not overflow, or indices on an array element access do
14143 not exceed the bounds of the array.
14145 For expressions you use in @value{GDBN} commands, you can tell
14146 @value{GDBN} to treat range errors in one of three ways: ignore them,
14147 always treat them as errors and abandon the expression, or issue
14148 warnings but evaluate the expression anyway.
14150 A range error can result from numerical overflow, from exceeding an
14151 array index bound, or when you type a constant that is not a member
14152 of any type. Some languages, however, do not treat overflows as an
14153 error. In many implementations of C, mathematical overflow causes the
14154 result to ``wrap around'' to lower values---for example, if @var{m} is
14155 the largest integer value, and @var{s} is the smallest, then
14158 @var{m} + 1 @result{} @var{s}
14161 This, too, is specific to individual languages, and in some cases
14162 specific to individual compilers or machines. @xref{Supported Languages, ,
14163 Supported Languages}, for further details on specific languages.
14165 @value{GDBN} provides some additional commands for controlling the range checker:
14167 @kindex set check range
14168 @kindex show check range
14170 @item set check range auto
14171 Set range checking on or off based on the current working language.
14172 @xref{Supported Languages, ,Supported Languages}, for the default settings for
14175 @item set check range on
14176 @itemx set check range off
14177 Set range checking on or off, overriding the default setting for the
14178 current working language. A warning is issued if the setting does not
14179 match the language default. If a range error occurs and range checking is on,
14180 then a message is printed and evaluation of the expression is aborted.
14182 @item set check range warn
14183 Output messages when the @value{GDBN} range checker detects a range error,
14184 but attempt to evaluate the expression anyway. Evaluating the
14185 expression may still be impossible for other reasons, such as accessing
14186 memory that the process does not own (a typical example from many Unix
14190 Show the current setting of the range checker, and whether or not it is
14191 being set automatically by @value{GDBN}.
14194 @node Supported Languages
14195 @section Supported Languages
14197 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
14198 OpenCL C, Pascal, assembly, Modula-2, and Ada.
14199 @c This is false ...
14200 Some @value{GDBN} features may be used in expressions regardless of the
14201 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
14202 and the @samp{@{type@}addr} construct (@pxref{Expressions,
14203 ,Expressions}) can be used with the constructs of any supported
14206 The following sections detail to what degree each source language is
14207 supported by @value{GDBN}. These sections are not meant to be language
14208 tutorials or references, but serve only as a reference guide to what the
14209 @value{GDBN} expression parser accepts, and what input and output
14210 formats should look like for different languages. There are many good
14211 books written on each of these languages; please look to these for a
14212 language reference or tutorial.
14215 * C:: C and C@t{++}
14218 * Objective-C:: Objective-C
14219 * OpenCL C:: OpenCL C
14220 * Fortran:: Fortran
14222 * Modula-2:: Modula-2
14227 @subsection C and C@t{++}
14229 @cindex C and C@t{++}
14230 @cindex expressions in C or C@t{++}
14232 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
14233 to both languages. Whenever this is the case, we discuss those languages
14237 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
14238 @cindex @sc{gnu} C@t{++}
14239 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
14240 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
14241 effectively, you must compile your C@t{++} programs with a supported
14242 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
14243 compiler (@code{aCC}).
14246 * C Operators:: C and C@t{++} operators
14247 * C Constants:: C and C@t{++} constants
14248 * C Plus Plus Expressions:: C@t{++} expressions
14249 * C Defaults:: Default settings for C and C@t{++}
14250 * C Checks:: C and C@t{++} type and range checks
14251 * Debugging C:: @value{GDBN} and C
14252 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
14253 * Decimal Floating Point:: Numbers in Decimal Floating Point format
14257 @subsubsection C and C@t{++} Operators
14259 @cindex C and C@t{++} operators
14261 Operators must be defined on values of specific types. For instance,
14262 @code{+} is defined on numbers, but not on structures. Operators are
14263 often defined on groups of types.
14265 For the purposes of C and C@t{++}, the following definitions hold:
14270 @emph{Integral types} include @code{int} with any of its storage-class
14271 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
14274 @emph{Floating-point types} include @code{float}, @code{double}, and
14275 @code{long double} (if supported by the target platform).
14278 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
14281 @emph{Scalar types} include all of the above.
14286 The following operators are supported. They are listed here
14287 in order of increasing precedence:
14291 The comma or sequencing operator. Expressions in a comma-separated list
14292 are evaluated from left to right, with the result of the entire
14293 expression being the last expression evaluated.
14296 Assignment. The value of an assignment expression is the value
14297 assigned. Defined on scalar types.
14300 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
14301 and translated to @w{@code{@var{a} = @var{a op b}}}.
14302 @w{@code{@var{op}=}} and @code{=} have the same precedence. The operator
14303 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
14304 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
14307 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
14308 of as: if @var{a} then @var{b} else @var{c}. The argument @var{a}
14309 should be of an integral type.
14312 Logical @sc{or}. Defined on integral types.
14315 Logical @sc{and}. Defined on integral types.
14318 Bitwise @sc{or}. Defined on integral types.
14321 Bitwise exclusive-@sc{or}. Defined on integral types.
14324 Bitwise @sc{and}. Defined on integral types.
14327 Equality and inequality. Defined on scalar types. The value of these
14328 expressions is 0 for false and non-zero for true.
14330 @item <@r{, }>@r{, }<=@r{, }>=
14331 Less than, greater than, less than or equal, greater than or equal.
14332 Defined on scalar types. The value of these expressions is 0 for false
14333 and non-zero for true.
14336 left shift, and right shift. Defined on integral types.
14339 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14342 Addition and subtraction. Defined on integral types, floating-point types and
14345 @item *@r{, }/@r{, }%
14346 Multiplication, division, and modulus. Multiplication and division are
14347 defined on integral and floating-point types. Modulus is defined on
14351 Increment and decrement. When appearing before a variable, the
14352 operation is performed before the variable is used in an expression;
14353 when appearing after it, the variable's value is used before the
14354 operation takes place.
14357 Pointer dereferencing. Defined on pointer types. Same precedence as
14361 Address operator. Defined on variables. Same precedence as @code{++}.
14363 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
14364 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
14365 to examine the address
14366 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
14370 Negative. Defined on integral and floating-point types. Same
14371 precedence as @code{++}.
14374 Logical negation. Defined on integral types. Same precedence as
14378 Bitwise complement operator. Defined on integral types. Same precedence as
14383 Structure member, and pointer-to-structure member. For convenience,
14384 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
14385 pointer based on the stored type information.
14386 Defined on @code{struct} and @code{union} data.
14389 Dereferences of pointers to members.
14392 Array indexing. @code{@var{a}[@var{i}]} is defined as
14393 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
14396 Function parameter list. Same precedence as @code{->}.
14399 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
14400 and @code{class} types.
14403 Doubled colons also represent the @value{GDBN} scope operator
14404 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
14408 If an operator is redefined in the user code, @value{GDBN} usually
14409 attempts to invoke the redefined version instead of using the operator's
14410 predefined meaning.
14413 @subsubsection C and C@t{++} Constants
14415 @cindex C and C@t{++} constants
14417 @value{GDBN} allows you to express the constants of C and C@t{++} in the
14422 Integer constants are a sequence of digits. Octal constants are
14423 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
14424 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
14425 @samp{l}, specifying that the constant should be treated as a
14429 Floating point constants are a sequence of digits, followed by a decimal
14430 point, followed by a sequence of digits, and optionally followed by an
14431 exponent. An exponent is of the form:
14432 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
14433 sequence of digits. The @samp{+} is optional for positive exponents.
14434 A floating-point constant may also end with a letter @samp{f} or
14435 @samp{F}, specifying that the constant should be treated as being of
14436 the @code{float} (as opposed to the default @code{double}) type; or with
14437 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
14441 Enumerated constants consist of enumerated identifiers, or their
14442 integral equivalents.
14445 Character constants are a single character surrounded by single quotes
14446 (@code{'}), or a number---the ordinal value of the corresponding character
14447 (usually its @sc{ascii} value). Within quotes, the single character may
14448 be represented by a letter or by @dfn{escape sequences}, which are of
14449 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
14450 of the character's ordinal value; or of the form @samp{\@var{x}}, where
14451 @samp{@var{x}} is a predefined special character---for example,
14452 @samp{\n} for newline.
14454 Wide character constants can be written by prefixing a character
14455 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
14456 form of @samp{x}. The target wide character set is used when
14457 computing the value of this constant (@pxref{Character Sets}).
14460 String constants are a sequence of character constants surrounded by
14461 double quotes (@code{"}). Any valid character constant (as described
14462 above) may appear. Double quotes within the string must be preceded by
14463 a backslash, so for instance @samp{"a\"b'c"} is a string of five
14466 Wide string constants can be written by prefixing a string constant
14467 with @samp{L}, as in C. The target wide character set is used when
14468 computing the value of this constant (@pxref{Character Sets}).
14471 Pointer constants are an integral value. You can also write pointers
14472 to constants using the C operator @samp{&}.
14475 Array constants are comma-separated lists surrounded by braces @samp{@{}
14476 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
14477 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
14478 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
14481 @node C Plus Plus Expressions
14482 @subsubsection C@t{++} Expressions
14484 @cindex expressions in C@t{++}
14485 @value{GDBN} expression handling can interpret most C@t{++} expressions.
14487 @cindex debugging C@t{++} programs
14488 @cindex C@t{++} compilers
14489 @cindex debug formats and C@t{++}
14490 @cindex @value{NGCC} and C@t{++}
14492 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
14493 the proper compiler and the proper debug format. Currently,
14494 @value{GDBN} works best when debugging C@t{++} code that is compiled
14495 with the most recent version of @value{NGCC} possible. The DWARF
14496 debugging format is preferred; @value{NGCC} defaults to this on most
14497 popular platforms. Other compilers and/or debug formats are likely to
14498 work badly or not at all when using @value{GDBN} to debug C@t{++}
14499 code. @xref{Compilation}.
14504 @cindex member functions
14506 Member function calls are allowed; you can use expressions like
14509 count = aml->GetOriginal(x, y)
14512 @vindex this@r{, inside C@t{++} member functions}
14513 @cindex namespace in C@t{++}
14515 While a member function is active (in the selected stack frame), your
14516 expressions have the same namespace available as the member function;
14517 that is, @value{GDBN} allows implicit references to the class instance
14518 pointer @code{this} following the same rules as C@t{++}. @code{using}
14519 declarations in the current scope are also respected by @value{GDBN}.
14521 @cindex call overloaded functions
14522 @cindex overloaded functions, calling
14523 @cindex type conversions in C@t{++}
14525 You can call overloaded functions; @value{GDBN} resolves the function
14526 call to the right definition, with some restrictions. @value{GDBN} does not
14527 perform overload resolution involving user-defined type conversions,
14528 calls to constructors, or instantiations of templates that do not exist
14529 in the program. It also cannot handle ellipsis argument lists or
14532 It does perform integral conversions and promotions, floating-point
14533 promotions, arithmetic conversions, pointer conversions, conversions of
14534 class objects to base classes, and standard conversions such as those of
14535 functions or arrays to pointers; it requires an exact match on the
14536 number of function arguments.
14538 Overload resolution is always performed, unless you have specified
14539 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
14540 ,@value{GDBN} Features for C@t{++}}.
14542 You must specify @code{set overload-resolution off} in order to use an
14543 explicit function signature to call an overloaded function, as in
14545 p 'foo(char,int)'('x', 13)
14548 The @value{GDBN} command-completion facility can simplify this;
14549 see @ref{Completion, ,Command Completion}.
14551 @cindex reference declarations
14553 @value{GDBN} understands variables declared as C@t{++} references; you can use
14554 them in expressions just as you do in C@t{++} source---they are automatically
14557 In the parameter list shown when @value{GDBN} displays a frame, the values of
14558 reference variables are not displayed (unlike other variables); this
14559 avoids clutter, since references are often used for large structures.
14560 The @emph{address} of a reference variable is always shown, unless
14561 you have specified @samp{set print address off}.
14564 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
14565 expressions can use it just as expressions in your program do. Since
14566 one scope may be defined in another, you can use @code{::} repeatedly if
14567 necessary, for example in an expression like
14568 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
14569 resolving name scope by reference to source files, in both C and C@t{++}
14570 debugging (@pxref{Variables, ,Program Variables}).
14573 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
14578 @subsubsection C and C@t{++} Defaults
14580 @cindex C and C@t{++} defaults
14582 If you allow @value{GDBN} to set range checking automatically, it
14583 defaults to @code{off} whenever the working language changes to
14584 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
14585 selects the working language.
14587 If you allow @value{GDBN} to set the language automatically, it
14588 recognizes source files whose names end with @file{.c}, @file{.C}, or
14589 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
14590 these files, it sets the working language to C or C@t{++}.
14591 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
14592 for further details.
14595 @subsubsection C and C@t{++} Type and Range Checks
14597 @cindex C and C@t{++} checks
14599 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
14600 checking is used. However, if you turn type checking off, @value{GDBN}
14601 will allow certain non-standard conversions, such as promoting integer
14602 constants to pointers.
14604 Range checking, if turned on, is done on mathematical operations. Array
14605 indices are not checked, since they are often used to index a pointer
14606 that is not itself an array.
14609 @subsubsection @value{GDBN} and C
14611 The @code{set print union} and @code{show print union} commands apply to
14612 the @code{union} type. When set to @samp{on}, any @code{union} that is
14613 inside a @code{struct} or @code{class} is also printed. Otherwise, it
14614 appears as @samp{@{...@}}.
14616 The @code{@@} operator aids in the debugging of dynamic arrays, formed
14617 with pointers and a memory allocation function. @xref{Expressions,
14620 @node Debugging C Plus Plus
14621 @subsubsection @value{GDBN} Features for C@t{++}
14623 @cindex commands for C@t{++}
14625 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
14626 designed specifically for use with C@t{++}. Here is a summary:
14629 @cindex break in overloaded functions
14630 @item @r{breakpoint menus}
14631 When you want a breakpoint in a function whose name is overloaded,
14632 @value{GDBN} has the capability to display a menu of possible breakpoint
14633 locations to help you specify which function definition you want.
14634 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
14636 @cindex overloading in C@t{++}
14637 @item rbreak @var{regex}
14638 Setting breakpoints using regular expressions is helpful for setting
14639 breakpoints on overloaded functions that are not members of any special
14641 @xref{Set Breaks, ,Setting Breakpoints}.
14643 @cindex C@t{++} exception handling
14645 @itemx catch rethrow
14647 Debug C@t{++} exception handling using these commands. @xref{Set
14648 Catchpoints, , Setting Catchpoints}.
14650 @cindex inheritance
14651 @item ptype @var{typename}
14652 Print inheritance relationships as well as other information for type
14654 @xref{Symbols, ,Examining the Symbol Table}.
14656 @item info vtbl @var{expression}.
14657 The @code{info vtbl} command can be used to display the virtual
14658 method tables of the object computed by @var{expression}. This shows
14659 one entry per virtual table; there may be multiple virtual tables when
14660 multiple inheritance is in use.
14662 @cindex C@t{++} demangling
14663 @item demangle @var{name}
14664 Demangle @var{name}.
14665 @xref{Symbols}, for a more complete description of the @code{demangle} command.
14667 @cindex C@t{++} symbol display
14668 @item set print demangle
14669 @itemx show print demangle
14670 @itemx set print asm-demangle
14671 @itemx show print asm-demangle
14672 Control whether C@t{++} symbols display in their source form, both when
14673 displaying code as C@t{++} source and when displaying disassemblies.
14674 @xref{Print Settings, ,Print Settings}.
14676 @item set print object
14677 @itemx show print object
14678 Choose whether to print derived (actual) or declared types of objects.
14679 @xref{Print Settings, ,Print Settings}.
14681 @item set print vtbl
14682 @itemx show print vtbl
14683 Control the format for printing virtual function tables.
14684 @xref{Print Settings, ,Print Settings}.
14685 (The @code{vtbl} commands do not work on programs compiled with the HP
14686 ANSI C@t{++} compiler (@code{aCC}).)
14688 @kindex set overload-resolution
14689 @cindex overloaded functions, overload resolution
14690 @item set overload-resolution on
14691 Enable overload resolution for C@t{++} expression evaluation. The default
14692 is on. For overloaded functions, @value{GDBN} evaluates the arguments
14693 and searches for a function whose signature matches the argument types,
14694 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
14695 Expressions, ,C@t{++} Expressions}, for details).
14696 If it cannot find a match, it emits a message.
14698 @item set overload-resolution off
14699 Disable overload resolution for C@t{++} expression evaluation. For
14700 overloaded functions that are not class member functions, @value{GDBN}
14701 chooses the first function of the specified name that it finds in the
14702 symbol table, whether or not its arguments are of the correct type. For
14703 overloaded functions that are class member functions, @value{GDBN}
14704 searches for a function whose signature @emph{exactly} matches the
14707 @kindex show overload-resolution
14708 @item show overload-resolution
14709 Show the current setting of overload resolution.
14711 @item @r{Overloaded symbol names}
14712 You can specify a particular definition of an overloaded symbol, using
14713 the same notation that is used to declare such symbols in C@t{++}: type
14714 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
14715 also use the @value{GDBN} command-line word completion facilities to list the
14716 available choices, or to finish the type list for you.
14717 @xref{Completion,, Command Completion}, for details on how to do this.
14720 @node Decimal Floating Point
14721 @subsubsection Decimal Floating Point format
14722 @cindex decimal floating point format
14724 @value{GDBN} can examine, set and perform computations with numbers in
14725 decimal floating point format, which in the C language correspond to the
14726 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
14727 specified by the extension to support decimal floating-point arithmetic.
14729 There are two encodings in use, depending on the architecture: BID (Binary
14730 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
14731 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
14734 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
14735 to manipulate decimal floating point numbers, it is not possible to convert
14736 (using a cast, for example) integers wider than 32-bit to decimal float.
14738 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
14739 point computations, error checking in decimal float operations ignores
14740 underflow, overflow and divide by zero exceptions.
14742 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
14743 to inspect @code{_Decimal128} values stored in floating point registers.
14744 See @ref{PowerPC,,PowerPC} for more details.
14750 @value{GDBN} can be used to debug programs written in D and compiled with
14751 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
14752 specific feature --- dynamic arrays.
14757 @cindex Go (programming language)
14758 @value{GDBN} can be used to debug programs written in Go and compiled with
14759 @file{gccgo} or @file{6g} compilers.
14761 Here is a summary of the Go-specific features and restrictions:
14764 @cindex current Go package
14765 @item The current Go package
14766 The name of the current package does not need to be specified when
14767 specifying global variables and functions.
14769 For example, given the program:
14773 var myglob = "Shall we?"
14779 When stopped inside @code{main} either of these work:
14783 (gdb) p main.myglob
14786 @cindex builtin Go types
14787 @item Builtin Go types
14788 The @code{string} type is recognized by @value{GDBN} and is printed
14791 @cindex builtin Go functions
14792 @item Builtin Go functions
14793 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
14794 function and handles it internally.
14796 @cindex restrictions on Go expressions
14797 @item Restrictions on Go expressions
14798 All Go operators are supported except @code{&^}.
14799 The Go @code{_} ``blank identifier'' is not supported.
14800 Automatic dereferencing of pointers is not supported.
14804 @subsection Objective-C
14806 @cindex Objective-C
14807 This section provides information about some commands and command
14808 options that are useful for debugging Objective-C code. See also
14809 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
14810 few more commands specific to Objective-C support.
14813 * Method Names in Commands::
14814 * The Print Command with Objective-C::
14817 @node Method Names in Commands
14818 @subsubsection Method Names in Commands
14820 The following commands have been extended to accept Objective-C method
14821 names as line specifications:
14823 @kindex clear@r{, and Objective-C}
14824 @kindex break@r{, and Objective-C}
14825 @kindex info line@r{, and Objective-C}
14826 @kindex jump@r{, and Objective-C}
14827 @kindex list@r{, and Objective-C}
14831 @item @code{info line}
14836 A fully qualified Objective-C method name is specified as
14839 -[@var{Class} @var{methodName}]
14842 where the minus sign is used to indicate an instance method and a
14843 plus sign (not shown) is used to indicate a class method. The class
14844 name @var{Class} and method name @var{methodName} are enclosed in
14845 brackets, similar to the way messages are specified in Objective-C
14846 source code. For example, to set a breakpoint at the @code{create}
14847 instance method of class @code{Fruit} in the program currently being
14851 break -[Fruit create]
14854 To list ten program lines around the @code{initialize} class method,
14858 list +[NSText initialize]
14861 In the current version of @value{GDBN}, the plus or minus sign is
14862 required. In future versions of @value{GDBN}, the plus or minus
14863 sign will be optional, but you can use it to narrow the search. It
14864 is also possible to specify just a method name:
14870 You must specify the complete method name, including any colons. If
14871 your program's source files contain more than one @code{create} method,
14872 you'll be presented with a numbered list of classes that implement that
14873 method. Indicate your choice by number, or type @samp{0} to exit if
14876 As another example, to clear a breakpoint established at the
14877 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14880 clear -[NSWindow makeKeyAndOrderFront:]
14883 @node The Print Command with Objective-C
14884 @subsubsection The Print Command With Objective-C
14885 @cindex Objective-C, print objects
14886 @kindex print-object
14887 @kindex po @r{(@code{print-object})}
14889 The print command has also been extended to accept methods. For example:
14892 print -[@var{object} hash]
14895 @cindex print an Objective-C object description
14896 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14898 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14899 and print the result. Also, an additional command has been added,
14900 @code{print-object} or @code{po} for short, which is meant to print
14901 the description of an object. However, this command may only work
14902 with certain Objective-C libraries that have a particular hook
14903 function, @code{_NSPrintForDebugger}, defined.
14906 @subsection OpenCL C
14909 This section provides information about @value{GDBN}s OpenCL C support.
14912 * OpenCL C Datatypes::
14913 * OpenCL C Expressions::
14914 * OpenCL C Operators::
14917 @node OpenCL C Datatypes
14918 @subsubsection OpenCL C Datatypes
14920 @cindex OpenCL C Datatypes
14921 @value{GDBN} supports the builtin scalar and vector datatypes specified
14922 by OpenCL 1.1. In addition the half- and double-precision floating point
14923 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14924 extensions are also known to @value{GDBN}.
14926 @node OpenCL C Expressions
14927 @subsubsection OpenCL C Expressions
14929 @cindex OpenCL C Expressions
14930 @value{GDBN} supports accesses to vector components including the access as
14931 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14932 supported by @value{GDBN} can be used as well.
14934 @node OpenCL C Operators
14935 @subsubsection OpenCL C Operators
14937 @cindex OpenCL C Operators
14938 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14942 @subsection Fortran
14943 @cindex Fortran-specific support in @value{GDBN}
14945 @value{GDBN} can be used to debug programs written in Fortran, but it
14946 currently supports only the features of Fortran 77 language.
14948 @cindex trailing underscore, in Fortran symbols
14949 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14950 among them) append an underscore to the names of variables and
14951 functions. When you debug programs compiled by those compilers, you
14952 will need to refer to variables and functions with a trailing
14956 * Fortran Operators:: Fortran operators and expressions
14957 * Fortran Defaults:: Default settings for Fortran
14958 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14961 @node Fortran Operators
14962 @subsubsection Fortran Operators and Expressions
14964 @cindex Fortran operators and expressions
14966 Operators must be defined on values of specific types. For instance,
14967 @code{+} is defined on numbers, but not on characters or other non-
14968 arithmetic types. Operators are often defined on groups of types.
14972 The exponentiation operator. It raises the first operand to the power
14976 The range operator. Normally used in the form of array(low:high) to
14977 represent a section of array.
14980 The access component operator. Normally used to access elements in derived
14981 types. Also suitable for unions. As unions aren't part of regular Fortran,
14982 this can only happen when accessing a register that uses a gdbarch-defined
14986 @node Fortran Defaults
14987 @subsubsection Fortran Defaults
14989 @cindex Fortran Defaults
14991 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14992 default uses case-insensitive matches for Fortran symbols. You can
14993 change that with the @samp{set case-insensitive} command, see
14994 @ref{Symbols}, for the details.
14996 @node Special Fortran Commands
14997 @subsubsection Special Fortran Commands
14999 @cindex Special Fortran commands
15001 @value{GDBN} has some commands to support Fortran-specific features,
15002 such as displaying common blocks.
15005 @cindex @code{COMMON} blocks, Fortran
15006 @kindex info common
15007 @item info common @r{[}@var{common-name}@r{]}
15008 This command prints the values contained in the Fortran @code{COMMON}
15009 block whose name is @var{common-name}. With no argument, the names of
15010 all @code{COMMON} blocks visible at the current program location are
15017 @cindex Pascal support in @value{GDBN}, limitations
15018 Debugging Pascal programs which use sets, subranges, file variables, or
15019 nested functions does not currently work. @value{GDBN} does not support
15020 entering expressions, printing values, or similar features using Pascal
15023 The Pascal-specific command @code{set print pascal_static-members}
15024 controls whether static members of Pascal objects are displayed.
15025 @xref{Print Settings, pascal_static-members}.
15028 @subsection Modula-2
15030 @cindex Modula-2, @value{GDBN} support
15032 The extensions made to @value{GDBN} to support Modula-2 only support
15033 output from the @sc{gnu} Modula-2 compiler (which is currently being
15034 developed). Other Modula-2 compilers are not currently supported, and
15035 attempting to debug executables produced by them is most likely
15036 to give an error as @value{GDBN} reads in the executable's symbol
15039 @cindex expressions in Modula-2
15041 * M2 Operators:: Built-in operators
15042 * Built-In Func/Proc:: Built-in functions and procedures
15043 * M2 Constants:: Modula-2 constants
15044 * M2 Types:: Modula-2 types
15045 * M2 Defaults:: Default settings for Modula-2
15046 * Deviations:: Deviations from standard Modula-2
15047 * M2 Checks:: Modula-2 type and range checks
15048 * M2 Scope:: The scope operators @code{::} and @code{.}
15049 * GDB/M2:: @value{GDBN} and Modula-2
15053 @subsubsection Operators
15054 @cindex Modula-2 operators
15056 Operators must be defined on values of specific types. For instance,
15057 @code{+} is defined on numbers, but not on structures. Operators are
15058 often defined on groups of types. For the purposes of Modula-2, the
15059 following definitions hold:
15064 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
15068 @emph{Character types} consist of @code{CHAR} and its subranges.
15071 @emph{Floating-point types} consist of @code{REAL}.
15074 @emph{Pointer types} consist of anything declared as @code{POINTER TO
15078 @emph{Scalar types} consist of all of the above.
15081 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
15084 @emph{Boolean types} consist of @code{BOOLEAN}.
15088 The following operators are supported, and appear in order of
15089 increasing precedence:
15093 Function argument or array index separator.
15096 Assignment. The value of @var{var} @code{:=} @var{value} is
15100 Less than, greater than on integral, floating-point, or enumerated
15104 Less than or equal to, greater than or equal to
15105 on integral, floating-point and enumerated types, or set inclusion on
15106 set types. Same precedence as @code{<}.
15108 @item =@r{, }<>@r{, }#
15109 Equality and two ways of expressing inequality, valid on scalar types.
15110 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
15111 available for inequality, since @code{#} conflicts with the script
15115 Set membership. Defined on set types and the types of their members.
15116 Same precedence as @code{<}.
15119 Boolean disjunction. Defined on boolean types.
15122 Boolean conjunction. Defined on boolean types.
15125 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
15128 Addition and subtraction on integral and floating-point types, or union
15129 and difference on set types.
15132 Multiplication on integral and floating-point types, or set intersection
15136 Division on floating-point types, or symmetric set difference on set
15137 types. Same precedence as @code{*}.
15140 Integer division and remainder. Defined on integral types. Same
15141 precedence as @code{*}.
15144 Negative. Defined on @code{INTEGER} and @code{REAL} data.
15147 Pointer dereferencing. Defined on pointer types.
15150 Boolean negation. Defined on boolean types. Same precedence as
15154 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
15155 precedence as @code{^}.
15158 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
15161 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
15165 @value{GDBN} and Modula-2 scope operators.
15169 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
15170 treats the use of the operator @code{IN}, or the use of operators
15171 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
15172 @code{<=}, and @code{>=} on sets as an error.
15176 @node Built-In Func/Proc
15177 @subsubsection Built-in Functions and Procedures
15178 @cindex Modula-2 built-ins
15180 Modula-2 also makes available several built-in procedures and functions.
15181 In describing these, the following metavariables are used:
15186 represents an @code{ARRAY} variable.
15189 represents a @code{CHAR} constant or variable.
15192 represents a variable or constant of integral type.
15195 represents an identifier that belongs to a set. Generally used in the
15196 same function with the metavariable @var{s}. The type of @var{s} should
15197 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
15200 represents a variable or constant of integral or floating-point type.
15203 represents a variable or constant of floating-point type.
15209 represents a variable.
15212 represents a variable or constant of one of many types. See the
15213 explanation of the function for details.
15216 All Modula-2 built-in procedures also return a result, described below.
15220 Returns the absolute value of @var{n}.
15223 If @var{c} is a lower case letter, it returns its upper case
15224 equivalent, otherwise it returns its argument.
15227 Returns the character whose ordinal value is @var{i}.
15230 Decrements the value in the variable @var{v} by one. Returns the new value.
15232 @item DEC(@var{v},@var{i})
15233 Decrements the value in the variable @var{v} by @var{i}. Returns the
15236 @item EXCL(@var{m},@var{s})
15237 Removes the element @var{m} from the set @var{s}. Returns the new
15240 @item FLOAT(@var{i})
15241 Returns the floating point equivalent of the integer @var{i}.
15243 @item HIGH(@var{a})
15244 Returns the index of the last member of @var{a}.
15247 Increments the value in the variable @var{v} by one. Returns the new value.
15249 @item INC(@var{v},@var{i})
15250 Increments the value in the variable @var{v} by @var{i}. Returns the
15253 @item INCL(@var{m},@var{s})
15254 Adds the element @var{m} to the set @var{s} if it is not already
15255 there. Returns the new set.
15258 Returns the maximum value of the type @var{t}.
15261 Returns the minimum value of the type @var{t}.
15264 Returns boolean TRUE if @var{i} is an odd number.
15267 Returns the ordinal value of its argument. For example, the ordinal
15268 value of a character is its @sc{ascii} value (on machines supporting
15269 the @sc{ascii} character set). The argument @var{x} must be of an
15270 ordered type, which include integral, character and enumerated types.
15272 @item SIZE(@var{x})
15273 Returns the size of its argument. The argument @var{x} can be a
15274 variable or a type.
15276 @item TRUNC(@var{r})
15277 Returns the integral part of @var{r}.
15279 @item TSIZE(@var{x})
15280 Returns the size of its argument. The argument @var{x} can be a
15281 variable or a type.
15283 @item VAL(@var{t},@var{i})
15284 Returns the member of the type @var{t} whose ordinal value is @var{i}.
15288 @emph{Warning:} Sets and their operations are not yet supported, so
15289 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
15293 @cindex Modula-2 constants
15295 @subsubsection Constants
15297 @value{GDBN} allows you to express the constants of Modula-2 in the following
15303 Integer constants are simply a sequence of digits. When used in an
15304 expression, a constant is interpreted to be type-compatible with the
15305 rest of the expression. Hexadecimal integers are specified by a
15306 trailing @samp{H}, and octal integers by a trailing @samp{B}.
15309 Floating point constants appear as a sequence of digits, followed by a
15310 decimal point and another sequence of digits. An optional exponent can
15311 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
15312 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
15313 digits of the floating point constant must be valid decimal (base 10)
15317 Character constants consist of a single character enclosed by a pair of
15318 like quotes, either single (@code{'}) or double (@code{"}). They may
15319 also be expressed by their ordinal value (their @sc{ascii} value, usually)
15320 followed by a @samp{C}.
15323 String constants consist of a sequence of characters enclosed by a
15324 pair of like quotes, either single (@code{'}) or double (@code{"}).
15325 Escape sequences in the style of C are also allowed. @xref{C
15326 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
15330 Enumerated constants consist of an enumerated identifier.
15333 Boolean constants consist of the identifiers @code{TRUE} and
15337 Pointer constants consist of integral values only.
15340 Set constants are not yet supported.
15344 @subsubsection Modula-2 Types
15345 @cindex Modula-2 types
15347 Currently @value{GDBN} can print the following data types in Modula-2
15348 syntax: array types, record types, set types, pointer types, procedure
15349 types, enumerated types, subrange types and base types. You can also
15350 print the contents of variables declared using these type.
15351 This section gives a number of simple source code examples together with
15352 sample @value{GDBN} sessions.
15354 The first example contains the following section of code:
15363 and you can request @value{GDBN} to interrogate the type and value of
15364 @code{r} and @code{s}.
15367 (@value{GDBP}) print s
15369 (@value{GDBP}) ptype s
15371 (@value{GDBP}) print r
15373 (@value{GDBP}) ptype r
15378 Likewise if your source code declares @code{s} as:
15382 s: SET ['A'..'Z'] ;
15386 then you may query the type of @code{s} by:
15389 (@value{GDBP}) ptype s
15390 type = SET ['A'..'Z']
15394 Note that at present you cannot interactively manipulate set
15395 expressions using the debugger.
15397 The following example shows how you might declare an array in Modula-2
15398 and how you can interact with @value{GDBN} to print its type and contents:
15402 s: ARRAY [-10..10] OF CHAR ;
15406 (@value{GDBP}) ptype s
15407 ARRAY [-10..10] OF CHAR
15410 Note that the array handling is not yet complete and although the type
15411 is printed correctly, expression handling still assumes that all
15412 arrays have a lower bound of zero and not @code{-10} as in the example
15415 Here are some more type related Modula-2 examples:
15419 colour = (blue, red, yellow, green) ;
15420 t = [blue..yellow] ;
15428 The @value{GDBN} interaction shows how you can query the data type
15429 and value of a variable.
15432 (@value{GDBP}) print s
15434 (@value{GDBP}) ptype t
15435 type = [blue..yellow]
15439 In this example a Modula-2 array is declared and its contents
15440 displayed. Observe that the contents are written in the same way as
15441 their @code{C} counterparts.
15445 s: ARRAY [1..5] OF CARDINAL ;
15451 (@value{GDBP}) print s
15452 $1 = @{1, 0, 0, 0, 0@}
15453 (@value{GDBP}) ptype s
15454 type = ARRAY [1..5] OF CARDINAL
15457 The Modula-2 language interface to @value{GDBN} also understands
15458 pointer types as shown in this example:
15462 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
15469 and you can request that @value{GDBN} describes the type of @code{s}.
15472 (@value{GDBP}) ptype s
15473 type = POINTER TO ARRAY [1..5] OF CARDINAL
15476 @value{GDBN} handles compound types as we can see in this example.
15477 Here we combine array types, record types, pointer types and subrange
15488 myarray = ARRAY myrange OF CARDINAL ;
15489 myrange = [-2..2] ;
15491 s: POINTER TO ARRAY myrange OF foo ;
15495 and you can ask @value{GDBN} to describe the type of @code{s} as shown
15499 (@value{GDBP}) ptype s
15500 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
15503 f3 : ARRAY [-2..2] OF CARDINAL;
15508 @subsubsection Modula-2 Defaults
15509 @cindex Modula-2 defaults
15511 If type and range checking are set automatically by @value{GDBN}, they
15512 both default to @code{on} whenever the working language changes to
15513 Modula-2. This happens regardless of whether you or @value{GDBN}
15514 selected the working language.
15516 If you allow @value{GDBN} to set the language automatically, then entering
15517 code compiled from a file whose name ends with @file{.mod} sets the
15518 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
15519 Infer the Source Language}, for further details.
15522 @subsubsection Deviations from Standard Modula-2
15523 @cindex Modula-2, deviations from
15525 A few changes have been made to make Modula-2 programs easier to debug.
15526 This is done primarily via loosening its type strictness:
15530 Unlike in standard Modula-2, pointer constants can be formed by
15531 integers. This allows you to modify pointer variables during
15532 debugging. (In standard Modula-2, the actual address contained in a
15533 pointer variable is hidden from you; it can only be modified
15534 through direct assignment to another pointer variable or expression that
15535 returned a pointer.)
15538 C escape sequences can be used in strings and characters to represent
15539 non-printable characters. @value{GDBN} prints out strings with these
15540 escape sequences embedded. Single non-printable characters are
15541 printed using the @samp{CHR(@var{nnn})} format.
15544 The assignment operator (@code{:=}) returns the value of its right-hand
15548 All built-in procedures both modify @emph{and} return their argument.
15552 @subsubsection Modula-2 Type and Range Checks
15553 @cindex Modula-2 checks
15556 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
15559 @c FIXME remove warning when type/range checks added
15561 @value{GDBN} considers two Modula-2 variables type equivalent if:
15565 They are of types that have been declared equivalent via a @code{TYPE
15566 @var{t1} = @var{t2}} statement
15569 They have been declared on the same line. (Note: This is true of the
15570 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
15573 As long as type checking is enabled, any attempt to combine variables
15574 whose types are not equivalent is an error.
15576 Range checking is done on all mathematical operations, assignment, array
15577 index bounds, and all built-in functions and procedures.
15580 @subsubsection The Scope Operators @code{::} and @code{.}
15582 @cindex @code{.}, Modula-2 scope operator
15583 @cindex colon, doubled as scope operator
15585 @vindex colon-colon@r{, in Modula-2}
15586 @c Info cannot handle :: but TeX can.
15589 @vindex ::@r{, in Modula-2}
15592 There are a few subtle differences between the Modula-2 scope operator
15593 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
15598 @var{module} . @var{id}
15599 @var{scope} :: @var{id}
15603 where @var{scope} is the name of a module or a procedure,
15604 @var{module} the name of a module, and @var{id} is any declared
15605 identifier within your program, except another module.
15607 Using the @code{::} operator makes @value{GDBN} search the scope
15608 specified by @var{scope} for the identifier @var{id}. If it is not
15609 found in the specified scope, then @value{GDBN} searches all scopes
15610 enclosing the one specified by @var{scope}.
15612 Using the @code{.} operator makes @value{GDBN} search the current scope for
15613 the identifier specified by @var{id} that was imported from the
15614 definition module specified by @var{module}. With this operator, it is
15615 an error if the identifier @var{id} was not imported from definition
15616 module @var{module}, or if @var{id} is not an identifier in
15620 @subsubsection @value{GDBN} and Modula-2
15622 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
15623 Five subcommands of @code{set print} and @code{show print} apply
15624 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
15625 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
15626 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
15627 analogue in Modula-2.
15629 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
15630 with any language, is not useful with Modula-2. Its
15631 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
15632 created in Modula-2 as they can in C or C@t{++}. However, because an
15633 address can be specified by an integral constant, the construct
15634 @samp{@{@var{type}@}@var{adrexp}} is still useful.
15636 @cindex @code{#} in Modula-2
15637 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
15638 interpreted as the beginning of a comment. Use @code{<>} instead.
15644 The extensions made to @value{GDBN} for Ada only support
15645 output from the @sc{gnu} Ada (GNAT) compiler.
15646 Other Ada compilers are not currently supported, and
15647 attempting to debug executables produced by them is most likely
15651 @cindex expressions in Ada
15653 * Ada Mode Intro:: General remarks on the Ada syntax
15654 and semantics supported by Ada mode
15656 * Omissions from Ada:: Restrictions on the Ada expression syntax.
15657 * Additions to Ada:: Extensions of the Ada expression syntax.
15658 * Overloading support for Ada:: Support for expressions involving overloaded
15660 * Stopping Before Main Program:: Debugging the program during elaboration.
15661 * Ada Exceptions:: Ada Exceptions
15662 * Ada Tasks:: Listing and setting breakpoints in tasks.
15663 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
15664 * Ravenscar Profile:: Tasking Support when using the Ravenscar
15666 * Ada Glitches:: Known peculiarities of Ada mode.
15669 @node Ada Mode Intro
15670 @subsubsection Introduction
15671 @cindex Ada mode, general
15673 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
15674 syntax, with some extensions.
15675 The philosophy behind the design of this subset is
15679 That @value{GDBN} should provide basic literals and access to operations for
15680 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
15681 leaving more sophisticated computations to subprograms written into the
15682 program (which therefore may be called from @value{GDBN}).
15685 That type safety and strict adherence to Ada language restrictions
15686 are not particularly important to the @value{GDBN} user.
15689 That brevity is important to the @value{GDBN} user.
15692 Thus, for brevity, the debugger acts as if all names declared in
15693 user-written packages are directly visible, even if they are not visible
15694 according to Ada rules, thus making it unnecessary to fully qualify most
15695 names with their packages, regardless of context. Where this causes
15696 ambiguity, @value{GDBN} asks the user's intent.
15698 The debugger will start in Ada mode if it detects an Ada main program.
15699 As for other languages, it will enter Ada mode when stopped in a program that
15700 was translated from an Ada source file.
15702 While in Ada mode, you may use `@t{--}' for comments. This is useful
15703 mostly for documenting command files. The standard @value{GDBN} comment
15704 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
15705 middle (to allow based literals).
15707 @node Omissions from Ada
15708 @subsubsection Omissions from Ada
15709 @cindex Ada, omissions from
15711 Here are the notable omissions from the subset:
15715 Only a subset of the attributes are supported:
15719 @t{'First}, @t{'Last}, and @t{'Length}
15720 on array objects (not on types and subtypes).
15723 @t{'Min} and @t{'Max}.
15726 @t{'Pos} and @t{'Val}.
15732 @t{'Range} on array objects (not subtypes), but only as the right
15733 operand of the membership (@code{in}) operator.
15736 @t{'Access}, @t{'Unchecked_Access}, and
15737 @t{'Unrestricted_Access} (a GNAT extension).
15745 @code{Characters.Latin_1} are not available and
15746 concatenation is not implemented. Thus, escape characters in strings are
15747 not currently available.
15750 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
15751 equality of representations. They will generally work correctly
15752 for strings and arrays whose elements have integer or enumeration types.
15753 They may not work correctly for arrays whose element
15754 types have user-defined equality, for arrays of real values
15755 (in particular, IEEE-conformant floating point, because of negative
15756 zeroes and NaNs), and for arrays whose elements contain unused bits with
15757 indeterminate values.
15760 The other component-by-component array operations (@code{and}, @code{or},
15761 @code{xor}, @code{not}, and relational tests other than equality)
15762 are not implemented.
15765 @cindex array aggregates (Ada)
15766 @cindex record aggregates (Ada)
15767 @cindex aggregates (Ada)
15768 There is limited support for array and record aggregates. They are
15769 permitted only on the right sides of assignments, as in these examples:
15772 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
15773 (@value{GDBP}) set An_Array := (1, others => 0)
15774 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
15775 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
15776 (@value{GDBP}) set A_Record := (1, "Peter", True);
15777 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
15781 discriminant's value by assigning an aggregate has an
15782 undefined effect if that discriminant is used within the record.
15783 However, you can first modify discriminants by directly assigning to
15784 them (which normally would not be allowed in Ada), and then performing an
15785 aggregate assignment. For example, given a variable @code{A_Rec}
15786 declared to have a type such as:
15789 type Rec (Len : Small_Integer := 0) is record
15791 Vals : IntArray (1 .. Len);
15795 you can assign a value with a different size of @code{Vals} with two
15799 (@value{GDBP}) set A_Rec.Len := 4
15800 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
15803 As this example also illustrates, @value{GDBN} is very loose about the usual
15804 rules concerning aggregates. You may leave out some of the
15805 components of an array or record aggregate (such as the @code{Len}
15806 component in the assignment to @code{A_Rec} above); they will retain their
15807 original values upon assignment. You may freely use dynamic values as
15808 indices in component associations. You may even use overlapping or
15809 redundant component associations, although which component values are
15810 assigned in such cases is not defined.
15813 Calls to dispatching subprograms are not implemented.
15816 The overloading algorithm is much more limited (i.e., less selective)
15817 than that of real Ada. It makes only limited use of the context in
15818 which a subexpression appears to resolve its meaning, and it is much
15819 looser in its rules for allowing type matches. As a result, some
15820 function calls will be ambiguous, and the user will be asked to choose
15821 the proper resolution.
15824 The @code{new} operator is not implemented.
15827 Entry calls are not implemented.
15830 Aside from printing, arithmetic operations on the native VAX floating-point
15831 formats are not supported.
15834 It is not possible to slice a packed array.
15837 The names @code{True} and @code{False}, when not part of a qualified name,
15838 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15840 Should your program
15841 redefine these names in a package or procedure (at best a dubious practice),
15842 you will have to use fully qualified names to access their new definitions.
15845 @node Additions to Ada
15846 @subsubsection Additions to Ada
15847 @cindex Ada, deviations from
15849 As it does for other languages, @value{GDBN} makes certain generic
15850 extensions to Ada (@pxref{Expressions}):
15854 If the expression @var{E} is a variable residing in memory (typically
15855 a local variable or array element) and @var{N} is a positive integer,
15856 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15857 @var{N}-1 adjacent variables following it in memory as an array. In
15858 Ada, this operator is generally not necessary, since its prime use is
15859 in displaying parts of an array, and slicing will usually do this in
15860 Ada. However, there are occasional uses when debugging programs in
15861 which certain debugging information has been optimized away.
15864 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15865 appears in function or file @var{B}.'' When @var{B} is a file name,
15866 you must typically surround it in single quotes.
15869 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15870 @var{type} that appears at address @var{addr}.''
15873 A name starting with @samp{$} is a convenience variable
15874 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15877 In addition, @value{GDBN} provides a few other shortcuts and outright
15878 additions specific to Ada:
15882 The assignment statement is allowed as an expression, returning
15883 its right-hand operand as its value. Thus, you may enter
15886 (@value{GDBP}) set x := y + 3
15887 (@value{GDBP}) print A(tmp := y + 1)
15891 The semicolon is allowed as an ``operator,'' returning as its value
15892 the value of its right-hand operand.
15893 This allows, for example,
15894 complex conditional breaks:
15897 (@value{GDBP}) break f
15898 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15902 Rather than use catenation and symbolic character names to introduce special
15903 characters into strings, one may instead use a special bracket notation,
15904 which is also used to print strings. A sequence of characters of the form
15905 @samp{["@var{XX}"]} within a string or character literal denotes the
15906 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15907 sequence of characters @samp{["""]} also denotes a single quotation mark
15908 in strings. For example,
15910 "One line.["0a"]Next line.["0a"]"
15913 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15917 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15918 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15922 (@value{GDBP}) print 'max(x, y)
15926 When printing arrays, @value{GDBN} uses positional notation when the
15927 array has a lower bound of 1, and uses a modified named notation otherwise.
15928 For example, a one-dimensional array of three integers with a lower bound
15929 of 3 might print as
15936 That is, in contrast to valid Ada, only the first component has a @code{=>}
15940 You may abbreviate attributes in expressions with any unique,
15941 multi-character subsequence of
15942 their names (an exact match gets preference).
15943 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15944 in place of @t{a'length}.
15947 @cindex quoting Ada internal identifiers
15948 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15949 to lower case. The GNAT compiler uses upper-case characters for
15950 some of its internal identifiers, which are normally of no interest to users.
15951 For the rare occasions when you actually have to look at them,
15952 enclose them in angle brackets to avoid the lower-case mapping.
15955 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15959 Printing an object of class-wide type or dereferencing an
15960 access-to-class-wide value will display all the components of the object's
15961 specific type (as indicated by its run-time tag). Likewise, component
15962 selection on such a value will operate on the specific type of the
15967 @node Overloading support for Ada
15968 @subsubsection Overloading support for Ada
15969 @cindex overloading, Ada
15971 The debugger supports limited overloading. Given a subprogram call in which
15972 the function symbol has multiple definitions, it will use the number of
15973 actual parameters and some information about their types to attempt to narrow
15974 the set of definitions. It also makes very limited use of context, preferring
15975 procedures to functions in the context of the @code{call} command, and
15976 functions to procedures elsewhere.
15978 If, after narrowing, the set of matching definitions still contains more than
15979 one definition, @value{GDBN} will display a menu to query which one it should
15983 (@value{GDBP}) print f(1)
15984 Multiple matches for f
15986 [1] foo.f (integer) return boolean at foo.adb:23
15987 [2] foo.f (foo.new_integer) return boolean at foo.adb:28
15991 In this case, just select one menu entry either to cancel expression evaluation
15992 (type @kbd{0} and press @key{RET}) or to continue evaluation with a specific
15993 instance (type the corresponding number and press @key{RET}).
15995 Here are a couple of commands to customize @value{GDBN}'s behavior in this
16000 @kindex set ada print-signatures
16001 @item set ada print-signatures
16002 Control whether parameter types and return types are displayed in overloads
16003 selection menus. It is @code{on} by default.
16004 @xref{Overloading support for Ada}.
16006 @kindex show ada print-signatures
16007 @item show ada print-signatures
16008 Show the current setting for displaying parameter types and return types in
16009 overloads selection menu.
16010 @xref{Overloading support for Ada}.
16014 @node Stopping Before Main Program
16015 @subsubsection Stopping at the Very Beginning
16017 @cindex breakpointing Ada elaboration code
16018 It is sometimes necessary to debug the program during elaboration, and
16019 before reaching the main procedure.
16020 As defined in the Ada Reference
16021 Manual, the elaboration code is invoked from a procedure called
16022 @code{adainit}. To run your program up to the beginning of
16023 elaboration, simply use the following two commands:
16024 @code{tbreak adainit} and @code{run}.
16026 @node Ada Exceptions
16027 @subsubsection Ada Exceptions
16029 A command is provided to list all Ada exceptions:
16032 @kindex info exceptions
16033 @item info exceptions
16034 @itemx info exceptions @var{regexp}
16035 The @code{info exceptions} command allows you to list all Ada exceptions
16036 defined within the program being debugged, as well as their addresses.
16037 With a regular expression, @var{regexp}, as argument, only those exceptions
16038 whose names match @var{regexp} are listed.
16041 Below is a small example, showing how the command can be used, first
16042 without argument, and next with a regular expression passed as an
16046 (@value{GDBP}) info exceptions
16047 All defined Ada exceptions:
16048 constraint_error: 0x613da0
16049 program_error: 0x613d20
16050 storage_error: 0x613ce0
16051 tasking_error: 0x613ca0
16052 const.aint_global_e: 0x613b00
16053 (@value{GDBP}) info exceptions const.aint
16054 All Ada exceptions matching regular expression "const.aint":
16055 constraint_error: 0x613da0
16056 const.aint_global_e: 0x613b00
16059 It is also possible to ask @value{GDBN} to stop your program's execution
16060 when an exception is raised. For more details, see @ref{Set Catchpoints}.
16063 @subsubsection Extensions for Ada Tasks
16064 @cindex Ada, tasking
16066 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
16067 @value{GDBN} provides the following task-related commands:
16072 This command shows a list of current Ada tasks, as in the following example:
16079 (@value{GDBP}) info tasks
16080 ID TID P-ID Pri State Name
16081 1 8088000 0 15 Child Activation Wait main_task
16082 2 80a4000 1 15 Accept Statement b
16083 3 809a800 1 15 Child Activation Wait a
16084 * 4 80ae800 3 15 Runnable c
16089 In this listing, the asterisk before the last task indicates it to be the
16090 task currently being inspected.
16094 Represents @value{GDBN}'s internal task number.
16100 The parent's task ID (@value{GDBN}'s internal task number).
16103 The base priority of the task.
16106 Current state of the task.
16110 The task has been created but has not been activated. It cannot be
16114 The task is not blocked for any reason known to Ada. (It may be waiting
16115 for a mutex, though.) It is conceptually "executing" in normal mode.
16118 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
16119 that were waiting on terminate alternatives have been awakened and have
16120 terminated themselves.
16122 @item Child Activation Wait
16123 The task is waiting for created tasks to complete activation.
16125 @item Accept Statement
16126 The task is waiting on an accept or selective wait statement.
16128 @item Waiting on entry call
16129 The task is waiting on an entry call.
16131 @item Async Select Wait
16132 The task is waiting to start the abortable part of an asynchronous
16136 The task is waiting on a select statement with only a delay
16139 @item Child Termination Wait
16140 The task is sleeping having completed a master within itself, and is
16141 waiting for the tasks dependent on that master to become terminated or
16142 waiting on a terminate Phase.
16144 @item Wait Child in Term Alt
16145 The task is sleeping waiting for tasks on terminate alternatives to
16146 finish terminating.
16148 @item Accepting RV with @var{taskno}
16149 The task is accepting a rendez-vous with the task @var{taskno}.
16153 Name of the task in the program.
16157 @kindex info task @var{taskno}
16158 @item info task @var{taskno}
16159 This command shows detailled informations on the specified task, as in
16160 the following example:
16165 (@value{GDBP}) info tasks
16166 ID TID P-ID Pri State Name
16167 1 8077880 0 15 Child Activation Wait main_task
16168 * 2 807c468 1 15 Runnable task_1
16169 (@value{GDBP}) info task 2
16170 Ada Task: 0x807c468
16173 Parent: 1 (main_task)
16179 @kindex task@r{ (Ada)}
16180 @cindex current Ada task ID
16181 This command prints the ID of the current task.
16187 (@value{GDBP}) info tasks
16188 ID TID P-ID Pri State Name
16189 1 8077870 0 15 Child Activation Wait main_task
16190 * 2 807c458 1 15 Runnable t
16191 (@value{GDBP}) task
16192 [Current task is 2]
16195 @item task @var{taskno}
16196 @cindex Ada task switching
16197 This command is like the @code{thread @var{thread-id}}
16198 command (@pxref{Threads}). It switches the context of debugging
16199 from the current task to the given task.
16205 (@value{GDBP}) info tasks
16206 ID TID P-ID Pri State Name
16207 1 8077870 0 15 Child Activation Wait main_task
16208 * 2 807c458 1 15 Runnable t
16209 (@value{GDBP}) task 1
16210 [Switching to task 1]
16211 #0 0x8067726 in pthread_cond_wait ()
16213 #0 0x8067726 in pthread_cond_wait ()
16214 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
16215 #2 0x805cb63 in system.task_primitives.operations.sleep ()
16216 #3 0x806153e in system.tasking.stages.activate_tasks ()
16217 #4 0x804aacc in un () at un.adb:5
16220 @item break @var{location} task @var{taskno}
16221 @itemx break @var{location} task @var{taskno} if @dots{}
16222 @cindex breakpoints and tasks, in Ada
16223 @cindex task breakpoints, in Ada
16224 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
16225 These commands are like the @code{break @dots{} thread @dots{}}
16226 command (@pxref{Thread Stops}). The
16227 @var{location} argument specifies source lines, as described
16228 in @ref{Specify Location}.
16230 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
16231 to specify that you only want @value{GDBN} to stop the program when a
16232 particular Ada task reaches this breakpoint. The @var{taskno} is one of the
16233 numeric task identifiers assigned by @value{GDBN}, shown in the first
16234 column of the @samp{info tasks} display.
16236 If you do not specify @samp{task @var{taskno}} when you set a
16237 breakpoint, the breakpoint applies to @emph{all} tasks of your
16240 You can use the @code{task} qualifier on conditional breakpoints as
16241 well; in this case, place @samp{task @var{taskno}} before the
16242 breakpoint condition (before the @code{if}).
16250 (@value{GDBP}) info tasks
16251 ID TID P-ID Pri State Name
16252 1 140022020 0 15 Child Activation Wait main_task
16253 2 140045060 1 15 Accept/Select Wait t2
16254 3 140044840 1 15 Runnable t1
16255 * 4 140056040 1 15 Runnable t3
16256 (@value{GDBP}) b 15 task 2
16257 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
16258 (@value{GDBP}) cont
16263 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
16265 (@value{GDBP}) info tasks
16266 ID TID P-ID Pri State Name
16267 1 140022020 0 15 Child Activation Wait main_task
16268 * 2 140045060 1 15 Runnable t2
16269 3 140044840 1 15 Runnable t1
16270 4 140056040 1 15 Delay Sleep t3
16274 @node Ada Tasks and Core Files
16275 @subsubsection Tasking Support when Debugging Core Files
16276 @cindex Ada tasking and core file debugging
16278 When inspecting a core file, as opposed to debugging a live program,
16279 tasking support may be limited or even unavailable, depending on
16280 the platform being used.
16281 For instance, on x86-linux, the list of tasks is available, but task
16282 switching is not supported.
16284 On certain platforms, the debugger needs to perform some
16285 memory writes in order to provide Ada tasking support. When inspecting
16286 a core file, this means that the core file must be opened with read-write
16287 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
16288 Under these circumstances, you should make a backup copy of the core
16289 file before inspecting it with @value{GDBN}.
16291 @node Ravenscar Profile
16292 @subsubsection Tasking Support when using the Ravenscar Profile
16293 @cindex Ravenscar Profile
16295 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
16296 specifically designed for systems with safety-critical real-time
16300 @kindex set ravenscar task-switching on
16301 @cindex task switching with program using Ravenscar Profile
16302 @item set ravenscar task-switching on
16303 Allows task switching when debugging a program that uses the Ravenscar
16304 Profile. This is the default.
16306 @kindex set ravenscar task-switching off
16307 @item set ravenscar task-switching off
16308 Turn off task switching when debugging a program that uses the Ravenscar
16309 Profile. This is mostly intended to disable the code that adds support
16310 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
16311 the Ravenscar runtime is preventing @value{GDBN} from working properly.
16312 To be effective, this command should be run before the program is started.
16314 @kindex show ravenscar task-switching
16315 @item show ravenscar task-switching
16316 Show whether it is possible to switch from task to task in a program
16317 using the Ravenscar Profile.
16322 @subsubsection Known Peculiarities of Ada Mode
16323 @cindex Ada, problems
16325 Besides the omissions listed previously (@pxref{Omissions from Ada}),
16326 we know of several problems with and limitations of Ada mode in
16328 some of which will be fixed with planned future releases of the debugger
16329 and the GNU Ada compiler.
16333 Static constants that the compiler chooses not to materialize as objects in
16334 storage are invisible to the debugger.
16337 Named parameter associations in function argument lists are ignored (the
16338 argument lists are treated as positional).
16341 Many useful library packages are currently invisible to the debugger.
16344 Fixed-point arithmetic, conversions, input, and output is carried out using
16345 floating-point arithmetic, and may give results that only approximate those on
16349 The GNAT compiler never generates the prefix @code{Standard} for any of
16350 the standard symbols defined by the Ada language. @value{GDBN} knows about
16351 this: it will strip the prefix from names when you use it, and will never
16352 look for a name you have so qualified among local symbols, nor match against
16353 symbols in other packages or subprograms. If you have
16354 defined entities anywhere in your program other than parameters and
16355 local variables whose simple names match names in @code{Standard},
16356 GNAT's lack of qualification here can cause confusion. When this happens,
16357 you can usually resolve the confusion
16358 by qualifying the problematic names with package
16359 @code{Standard} explicitly.
16362 Older versions of the compiler sometimes generate erroneous debugging
16363 information, resulting in the debugger incorrectly printing the value
16364 of affected entities. In some cases, the debugger is able to work
16365 around an issue automatically. In other cases, the debugger is able
16366 to work around the issue, but the work-around has to be specifically
16369 @kindex set ada trust-PAD-over-XVS
16370 @kindex show ada trust-PAD-over-XVS
16373 @item set ada trust-PAD-over-XVS on
16374 Configure GDB to strictly follow the GNAT encoding when computing the
16375 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
16376 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
16377 a complete description of the encoding used by the GNAT compiler).
16378 This is the default.
16380 @item set ada trust-PAD-over-XVS off
16381 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
16382 sometimes prints the wrong value for certain entities, changing @code{ada
16383 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
16384 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
16385 @code{off}, but this incurs a slight performance penalty, so it is
16386 recommended to leave this setting to @code{on} unless necessary.
16390 @cindex GNAT descriptive types
16391 @cindex GNAT encoding
16392 Internally, the debugger also relies on the compiler following a number
16393 of conventions known as the @samp{GNAT Encoding}, all documented in
16394 @file{gcc/ada/exp_dbug.ads} in the GCC sources. This encoding describes
16395 how the debugging information should be generated for certain types.
16396 In particular, this convention makes use of @dfn{descriptive types},
16397 which are artificial types generated purely to help the debugger.
16399 These encodings were defined at a time when the debugging information
16400 format used was not powerful enough to describe some of the more complex
16401 types available in Ada. Since DWARF allows us to express nearly all
16402 Ada features, the long-term goal is to slowly replace these descriptive
16403 types by their pure DWARF equivalent. To facilitate that transition,
16404 a new maintenance option is available to force the debugger to ignore
16405 those descriptive types. It allows the user to quickly evaluate how
16406 well @value{GDBN} works without them.
16410 @kindex maint ada set ignore-descriptive-types
16411 @item maintenance ada set ignore-descriptive-types [on|off]
16412 Control whether the debugger should ignore descriptive types.
16413 The default is not to ignore descriptives types (@code{off}).
16415 @kindex maint ada show ignore-descriptive-types
16416 @item maintenance ada show ignore-descriptive-types
16417 Show if descriptive types are ignored by @value{GDBN}.
16421 @node Unsupported Languages
16422 @section Unsupported Languages
16424 @cindex unsupported languages
16425 @cindex minimal language
16426 In addition to the other fully-supported programming languages,
16427 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
16428 It does not represent a real programming language, but provides a set
16429 of capabilities close to what the C or assembly languages provide.
16430 This should allow most simple operations to be performed while debugging
16431 an application that uses a language currently not supported by @value{GDBN}.
16433 If the language is set to @code{auto}, @value{GDBN} will automatically
16434 select this language if the current frame corresponds to an unsupported
16438 @chapter Examining the Symbol Table
16440 The commands described in this chapter allow you to inquire about the
16441 symbols (names of variables, functions and types) defined in your
16442 program. This information is inherent in the text of your program and
16443 does not change as your program executes. @value{GDBN} finds it in your
16444 program's symbol table, in the file indicated when you started @value{GDBN}
16445 (@pxref{File Options, ,Choosing Files}), or by one of the
16446 file-management commands (@pxref{Files, ,Commands to Specify Files}).
16448 @cindex symbol names
16449 @cindex names of symbols
16450 @cindex quoting names
16451 Occasionally, you may need to refer to symbols that contain unusual
16452 characters, which @value{GDBN} ordinarily treats as word delimiters. The
16453 most frequent case is in referring to static variables in other
16454 source files (@pxref{Variables,,Program Variables}). File names
16455 are recorded in object files as debugging symbols, but @value{GDBN} would
16456 ordinarily parse a typical file name, like @file{foo.c}, as the three words
16457 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
16458 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
16465 looks up the value of @code{x} in the scope of the file @file{foo.c}.
16468 @cindex case-insensitive symbol names
16469 @cindex case sensitivity in symbol names
16470 @kindex set case-sensitive
16471 @item set case-sensitive on
16472 @itemx set case-sensitive off
16473 @itemx set case-sensitive auto
16474 Normally, when @value{GDBN} looks up symbols, it matches their names
16475 with case sensitivity determined by the current source language.
16476 Occasionally, you may wish to control that. The command @code{set
16477 case-sensitive} lets you do that by specifying @code{on} for
16478 case-sensitive matches or @code{off} for case-insensitive ones. If
16479 you specify @code{auto}, case sensitivity is reset to the default
16480 suitable for the source language. The default is case-sensitive
16481 matches for all languages except for Fortran, for which the default is
16482 case-insensitive matches.
16484 @kindex show case-sensitive
16485 @item show case-sensitive
16486 This command shows the current setting of case sensitivity for symbols
16489 @kindex set print type methods
16490 @item set print type methods
16491 @itemx set print type methods on
16492 @itemx set print type methods off
16493 Normally, when @value{GDBN} prints a class, it displays any methods
16494 declared in that class. You can control this behavior either by
16495 passing the appropriate flag to @code{ptype}, or using @command{set
16496 print type methods}. Specifying @code{on} will cause @value{GDBN} to
16497 display the methods; this is the default. Specifying @code{off} will
16498 cause @value{GDBN} to omit the methods.
16500 @kindex show print type methods
16501 @item show print type methods
16502 This command shows the current setting of method display when printing
16505 @kindex set print type typedefs
16506 @item set print type typedefs
16507 @itemx set print type typedefs on
16508 @itemx set print type typedefs off
16510 Normally, when @value{GDBN} prints a class, it displays any typedefs
16511 defined in that class. You can control this behavior either by
16512 passing the appropriate flag to @code{ptype}, or using @command{set
16513 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
16514 display the typedef definitions; this is the default. Specifying
16515 @code{off} will cause @value{GDBN} to omit the typedef definitions.
16516 Note that this controls whether the typedef definition itself is
16517 printed, not whether typedef names are substituted when printing other
16520 @kindex show print type typedefs
16521 @item show print type typedefs
16522 This command shows the current setting of typedef display when
16525 @kindex info address
16526 @cindex address of a symbol
16527 @item info address @var{symbol}
16528 Describe where the data for @var{symbol} is stored. For a register
16529 variable, this says which register it is kept in. For a non-register
16530 local variable, this prints the stack-frame offset at which the variable
16533 Note the contrast with @samp{print &@var{symbol}}, which does not work
16534 at all for a register variable, and for a stack local variable prints
16535 the exact address of the current instantiation of the variable.
16537 @kindex info symbol
16538 @cindex symbol from address
16539 @cindex closest symbol and offset for an address
16540 @item info symbol @var{addr}
16541 Print the name of a symbol which is stored at the address @var{addr}.
16542 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
16543 nearest symbol and an offset from it:
16546 (@value{GDBP}) info symbol 0x54320
16547 _initialize_vx + 396 in section .text
16551 This is the opposite of the @code{info address} command. You can use
16552 it to find out the name of a variable or a function given its address.
16554 For dynamically linked executables, the name of executable or shared
16555 library containing the symbol is also printed:
16558 (@value{GDBP}) info symbol 0x400225
16559 _start + 5 in section .text of /tmp/a.out
16560 (@value{GDBP}) info symbol 0x2aaaac2811cf
16561 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
16566 @item demangle @r{[}-l @var{language}@r{]} @r{[}@var{--}@r{]} @var{name}
16567 Demangle @var{name}.
16568 If @var{language} is provided it is the name of the language to demangle
16569 @var{name} in. Otherwise @var{name} is demangled in the current language.
16571 The @samp{--} option specifies the end of options,
16572 and is useful when @var{name} begins with a dash.
16574 The parameter @code{demangle-style} specifies how to interpret the kind
16575 of mangling used. @xref{Print Settings}.
16578 @item whatis[/@var{flags}] [@var{arg}]
16579 Print the data type of @var{arg}, which can be either an expression
16580 or a name of a data type. With no argument, print the data type of
16581 @code{$}, the last value in the value history.
16583 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
16584 is not actually evaluated, and any side-effecting operations (such as
16585 assignments or function calls) inside it do not take place.
16587 If @var{arg} is a variable or an expression, @code{whatis} prints its
16588 literal type as it is used in the source code. If the type was
16589 defined using a @code{typedef}, @code{whatis} will @emph{not} print
16590 the data type underlying the @code{typedef}. If the type of the
16591 variable or the expression is a compound data type, such as
16592 @code{struct} or @code{class}, @code{whatis} never prints their
16593 fields or methods. It just prints the @code{struct}/@code{class}
16594 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
16595 such a compound data type, use @code{ptype}.
16597 If @var{arg} is a type name that was defined using @code{typedef},
16598 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
16599 Unrolling means that @code{whatis} will show the underlying type used
16600 in the @code{typedef} declaration of @var{arg}. However, if that
16601 underlying type is also a @code{typedef}, @code{whatis} will not
16604 For C code, the type names may also have the form @samp{class
16605 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
16606 @var{union-tag}} or @samp{enum @var{enum-tag}}.
16608 @var{flags} can be used to modify how the type is displayed.
16609 Available flags are:
16613 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
16614 parameters and typedefs defined in a class when printing the class'
16615 members. The @code{/r} flag disables this.
16618 Do not print methods defined in the class.
16621 Print methods defined in the class. This is the default, but the flag
16622 exists in case you change the default with @command{set print type methods}.
16625 Do not print typedefs defined in the class. Note that this controls
16626 whether the typedef definition itself is printed, not whether typedef
16627 names are substituted when printing other types.
16630 Print typedefs defined in the class. This is the default, but the flag
16631 exists in case you change the default with @command{set print type typedefs}.
16635 @item ptype[/@var{flags}] [@var{arg}]
16636 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
16637 detailed description of the type, instead of just the name of the type.
16638 @xref{Expressions, ,Expressions}.
16640 Contrary to @code{whatis}, @code{ptype} always unrolls any
16641 @code{typedef}s in its argument declaration, whether the argument is
16642 a variable, expression, or a data type. This means that @code{ptype}
16643 of a variable or an expression will not print literally its type as
16644 present in the source code---use @code{whatis} for that. @code{typedef}s at
16645 the pointer or reference targets are also unrolled. Only @code{typedef}s of
16646 fields, methods and inner @code{class typedef}s of @code{struct}s,
16647 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
16649 For example, for this variable declaration:
16652 typedef double real_t;
16653 struct complex @{ real_t real; double imag; @};
16654 typedef struct complex complex_t;
16656 real_t *real_pointer_var;
16660 the two commands give this output:
16664 (@value{GDBP}) whatis var
16666 (@value{GDBP}) ptype var
16667 type = struct complex @{
16671 (@value{GDBP}) whatis complex_t
16672 type = struct complex
16673 (@value{GDBP}) whatis struct complex
16674 type = struct complex
16675 (@value{GDBP}) ptype struct complex
16676 type = struct complex @{
16680 (@value{GDBP}) whatis real_pointer_var
16682 (@value{GDBP}) ptype real_pointer_var
16688 As with @code{whatis}, using @code{ptype} without an argument refers to
16689 the type of @code{$}, the last value in the value history.
16691 @cindex incomplete type
16692 Sometimes, programs use opaque data types or incomplete specifications
16693 of complex data structure. If the debug information included in the
16694 program does not allow @value{GDBN} to display a full declaration of
16695 the data type, it will say @samp{<incomplete type>}. For example,
16696 given these declarations:
16700 struct foo *fooptr;
16704 but no definition for @code{struct foo} itself, @value{GDBN} will say:
16707 (@value{GDBP}) ptype foo
16708 $1 = <incomplete type>
16712 ``Incomplete type'' is C terminology for data types that are not
16713 completely specified.
16716 @item info types @var{regexp}
16718 Print a brief description of all types whose names match the regular
16719 expression @var{regexp} (or all types in your program, if you supply
16720 no argument). Each complete typename is matched as though it were a
16721 complete line; thus, @samp{i type value} gives information on all
16722 types in your program whose names include the string @code{value}, but
16723 @samp{i type ^value$} gives information only on types whose complete
16724 name is @code{value}.
16726 This command differs from @code{ptype} in two ways: first, like
16727 @code{whatis}, it does not print a detailed description; second, it
16728 lists all source files where a type is defined.
16730 @kindex info type-printers
16731 @item info type-printers
16732 Versions of @value{GDBN} that ship with Python scripting enabled may
16733 have ``type printers'' available. When using @command{ptype} or
16734 @command{whatis}, these printers are consulted when the name of a type
16735 is needed. @xref{Type Printing API}, for more information on writing
16738 @code{info type-printers} displays all the available type printers.
16740 @kindex enable type-printer
16741 @kindex disable type-printer
16742 @item enable type-printer @var{name}@dots{}
16743 @item disable type-printer @var{name}@dots{}
16744 These commands can be used to enable or disable type printers.
16747 @cindex local variables
16748 @item info scope @var{location}
16749 List all the variables local to a particular scope. This command
16750 accepts a @var{location} argument---a function name, a source line, or
16751 an address preceded by a @samp{*}, and prints all the variables local
16752 to the scope defined by that location. (@xref{Specify Location}, for
16753 details about supported forms of @var{location}.) For example:
16756 (@value{GDBP}) @b{info scope command_line_handler}
16757 Scope for command_line_handler:
16758 Symbol rl is an argument at stack/frame offset 8, length 4.
16759 Symbol linebuffer is in static storage at address 0x150a18, length 4.
16760 Symbol linelength is in static storage at address 0x150a1c, length 4.
16761 Symbol p is a local variable in register $esi, length 4.
16762 Symbol p1 is a local variable in register $ebx, length 4.
16763 Symbol nline is a local variable in register $edx, length 4.
16764 Symbol repeat is a local variable at frame offset -8, length 4.
16768 This command is especially useful for determining what data to collect
16769 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
16772 @kindex info source
16774 Show information about the current source file---that is, the source file for
16775 the function containing the current point of execution:
16778 the name of the source file, and the directory containing it,
16780 the directory it was compiled in,
16782 its length, in lines,
16784 which programming language it is written in,
16786 if the debug information provides it, the program that compiled the file
16787 (which may include, e.g., the compiler version and command line arguments),
16789 whether the executable includes debugging information for that file, and
16790 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
16792 whether the debugging information includes information about
16793 preprocessor macros.
16797 @kindex info sources
16799 Print the names of all source files in your program for which there is
16800 debugging information, organized into two lists: files whose symbols
16801 have already been read, and files whose symbols will be read when needed.
16803 @kindex info functions
16804 @item info functions
16805 Print the names and data types of all defined functions.
16807 @item info functions @var{regexp}
16808 Print the names and data types of all defined functions
16809 whose names contain a match for regular expression @var{regexp}.
16810 Thus, @samp{info fun step} finds all functions whose names
16811 include @code{step}; @samp{info fun ^step} finds those whose names
16812 start with @code{step}. If a function name contains characters
16813 that conflict with the regular expression language (e.g.@:
16814 @samp{operator*()}), they may be quoted with a backslash.
16816 @kindex info variables
16817 @item info variables
16818 Print the names and data types of all variables that are defined
16819 outside of functions (i.e.@: excluding local variables).
16821 @item info variables @var{regexp}
16822 Print the names and data types of all variables (except for local
16823 variables) whose names contain a match for regular expression
16826 @kindex info classes
16827 @cindex Objective-C, classes and selectors
16829 @itemx info classes @var{regexp}
16830 Display all Objective-C classes in your program, or
16831 (with the @var{regexp} argument) all those matching a particular regular
16834 @kindex info selectors
16835 @item info selectors
16836 @itemx info selectors @var{regexp}
16837 Display all Objective-C selectors in your program, or
16838 (with the @var{regexp} argument) all those matching a particular regular
16842 This was never implemented.
16843 @kindex info methods
16845 @itemx info methods @var{regexp}
16846 The @code{info methods} command permits the user to examine all defined
16847 methods within C@t{++} program, or (with the @var{regexp} argument) a
16848 specific set of methods found in the various C@t{++} classes. Many
16849 C@t{++} classes provide a large number of methods. Thus, the output
16850 from the @code{ptype} command can be overwhelming and hard to use. The
16851 @code{info-methods} command filters the methods, printing only those
16852 which match the regular-expression @var{regexp}.
16855 @cindex opaque data types
16856 @kindex set opaque-type-resolution
16857 @item set opaque-type-resolution on
16858 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
16859 declared as a pointer to a @code{struct}, @code{class}, or
16860 @code{union}---for example, @code{struct MyType *}---that is used in one
16861 source file although the full declaration of @code{struct MyType} is in
16862 another source file. The default is on.
16864 A change in the setting of this subcommand will not take effect until
16865 the next time symbols for a file are loaded.
16867 @item set opaque-type-resolution off
16868 Tell @value{GDBN} not to resolve opaque types. In this case, the type
16869 is printed as follows:
16871 @{<no data fields>@}
16874 @kindex show opaque-type-resolution
16875 @item show opaque-type-resolution
16876 Show whether opaque types are resolved or not.
16878 @kindex set print symbol-loading
16879 @cindex print messages when symbols are loaded
16880 @item set print symbol-loading
16881 @itemx set print symbol-loading full
16882 @itemx set print symbol-loading brief
16883 @itemx set print symbol-loading off
16884 The @code{set print symbol-loading} command allows you to control the
16885 printing of messages when @value{GDBN} loads symbol information.
16886 By default a message is printed for the executable and one for each
16887 shared library, and normally this is what you want. However, when
16888 debugging apps with large numbers of shared libraries these messages
16890 When set to @code{brief} a message is printed for each executable,
16891 and when @value{GDBN} loads a collection of shared libraries at once
16892 it will only print one message regardless of the number of shared
16893 libraries. When set to @code{off} no messages are printed.
16895 @kindex show print symbol-loading
16896 @item show print symbol-loading
16897 Show whether messages will be printed when a @value{GDBN} command
16898 entered from the keyboard causes symbol information to be loaded.
16900 @kindex maint print symbols
16901 @cindex symbol dump
16902 @kindex maint print psymbols
16903 @cindex partial symbol dump
16904 @kindex maint print msymbols
16905 @cindex minimal symbol dump
16906 @item maint print symbols @var{filename}
16907 @itemx maint print psymbols @var{filename}
16908 @itemx maint print msymbols @var{filename}
16909 Write a dump of debugging symbol data into the file @var{filename}.
16910 These commands are used to debug the @value{GDBN} symbol-reading code. Only
16911 symbols with debugging data are included. If you use @samp{maint print
16912 symbols}, @value{GDBN} includes all the symbols for which it has already
16913 collected full details: that is, @var{filename} reflects symbols for
16914 only those files whose symbols @value{GDBN} has read. You can use the
16915 command @code{info sources} to find out which files these are. If you
16916 use @samp{maint print psymbols} instead, the dump shows information about
16917 symbols that @value{GDBN} only knows partially---that is, symbols defined in
16918 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
16919 @samp{maint print msymbols} dumps just the minimal symbol information
16920 required for each object file from which @value{GDBN} has read some symbols.
16921 @xref{Files, ,Commands to Specify Files}, for a discussion of how
16922 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
16924 @kindex maint info symtabs
16925 @kindex maint info psymtabs
16926 @cindex listing @value{GDBN}'s internal symbol tables
16927 @cindex symbol tables, listing @value{GDBN}'s internal
16928 @cindex full symbol tables, listing @value{GDBN}'s internal
16929 @cindex partial symbol tables, listing @value{GDBN}'s internal
16930 @item maint info symtabs @r{[} @var{regexp} @r{]}
16931 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
16933 List the @code{struct symtab} or @code{struct partial_symtab}
16934 structures whose names match @var{regexp}. If @var{regexp} is not
16935 given, list them all. The output includes expressions which you can
16936 copy into a @value{GDBN} debugging this one to examine a particular
16937 structure in more detail. For example:
16940 (@value{GDBP}) maint info psymtabs dwarf2read
16941 @{ objfile /home/gnu/build/gdb/gdb
16942 ((struct objfile *) 0x82e69d0)
16943 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
16944 ((struct partial_symtab *) 0x8474b10)
16947 text addresses 0x814d3c8 -- 0x8158074
16948 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
16949 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
16950 dependencies (none)
16953 (@value{GDBP}) maint info symtabs
16957 We see that there is one partial symbol table whose filename contains
16958 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
16959 and we see that @value{GDBN} has not read in any symtabs yet at all.
16960 If we set a breakpoint on a function, that will cause @value{GDBN} to
16961 read the symtab for the compilation unit containing that function:
16964 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16965 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16967 (@value{GDBP}) maint info symtabs
16968 @{ objfile /home/gnu/build/gdb/gdb
16969 ((struct objfile *) 0x82e69d0)
16970 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16971 ((struct symtab *) 0x86c1f38)
16974 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16975 linetable ((struct linetable *) 0x8370fa0)
16976 debugformat DWARF 2
16982 @kindex maint set symbol-cache-size
16983 @cindex symbol cache size
16984 @item maint set symbol-cache-size @var{size}
16985 Set the size of the symbol cache to @var{size}.
16986 The default size is intended to be good enough for debugging
16987 most applications. This option exists to allow for experimenting
16988 with different sizes.
16990 @kindex maint show symbol-cache-size
16991 @item maint show symbol-cache-size
16992 Show the size of the symbol cache.
16994 @kindex maint print symbol-cache
16995 @cindex symbol cache, printing its contents
16996 @item maint print symbol-cache
16997 Print the contents of the symbol cache.
16998 This is useful when debugging symbol cache issues.
17000 @kindex maint print symbol-cache-statistics
17001 @cindex symbol cache, printing usage statistics
17002 @item maint print symbol-cache-statistics
17003 Print symbol cache usage statistics.
17004 This helps determine how well the cache is being utilized.
17006 @kindex maint flush-symbol-cache
17007 @cindex symbol cache, flushing
17008 @item maint flush-symbol-cache
17009 Flush the contents of the symbol cache, all entries are removed.
17010 This command is useful when debugging the symbol cache.
17011 It is also useful when collecting performance data.
17016 @chapter Altering Execution
17018 Once you think you have found an error in your program, you might want to
17019 find out for certain whether correcting the apparent error would lead to
17020 correct results in the rest of the run. You can find the answer by
17021 experiment, using the @value{GDBN} features for altering execution of the
17024 For example, you can store new values into variables or memory
17025 locations, give your program a signal, restart it at a different
17026 address, or even return prematurely from a function.
17029 * Assignment:: Assignment to variables
17030 * Jumping:: Continuing at a different address
17031 * Signaling:: Giving your program a signal
17032 * Returning:: Returning from a function
17033 * Calling:: Calling your program's functions
17034 * Patching:: Patching your program
17035 * Compiling and Injecting Code:: Compiling and injecting code in @value{GDBN}
17039 @section Assignment to Variables
17042 @cindex setting variables
17043 To alter the value of a variable, evaluate an assignment expression.
17044 @xref{Expressions, ,Expressions}. For example,
17051 stores the value 4 into the variable @code{x}, and then prints the
17052 value of the assignment expression (which is 4).
17053 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
17054 information on operators in supported languages.
17056 @kindex set variable
17057 @cindex variables, setting
17058 If you are not interested in seeing the value of the assignment, use the
17059 @code{set} command instead of the @code{print} command. @code{set} is
17060 really the same as @code{print} except that the expression's value is
17061 not printed and is not put in the value history (@pxref{Value History,
17062 ,Value History}). The expression is evaluated only for its effects.
17064 If the beginning of the argument string of the @code{set} command
17065 appears identical to a @code{set} subcommand, use the @code{set
17066 variable} command instead of just @code{set}. This command is identical
17067 to @code{set} except for its lack of subcommands. For example, if your
17068 program has a variable @code{width}, you get an error if you try to set
17069 a new value with just @samp{set width=13}, because @value{GDBN} has the
17070 command @code{set width}:
17073 (@value{GDBP}) whatis width
17075 (@value{GDBP}) p width
17077 (@value{GDBP}) set width=47
17078 Invalid syntax in expression.
17082 The invalid expression, of course, is @samp{=47}. In
17083 order to actually set the program's variable @code{width}, use
17086 (@value{GDBP}) set var width=47
17089 Because the @code{set} command has many subcommands that can conflict
17090 with the names of program variables, it is a good idea to use the
17091 @code{set variable} command instead of just @code{set}. For example, if
17092 your program has a variable @code{g}, you run into problems if you try
17093 to set a new value with just @samp{set g=4}, because @value{GDBN} has
17094 the command @code{set gnutarget}, abbreviated @code{set g}:
17098 (@value{GDBP}) whatis g
17102 (@value{GDBP}) set g=4
17106 The program being debugged has been started already.
17107 Start it from the beginning? (y or n) y
17108 Starting program: /home/smith/cc_progs/a.out
17109 "/home/smith/cc_progs/a.out": can't open to read symbols:
17110 Invalid bfd target.
17111 (@value{GDBP}) show g
17112 The current BFD target is "=4".
17117 The program variable @code{g} did not change, and you silently set the
17118 @code{gnutarget} to an invalid value. In order to set the variable
17122 (@value{GDBP}) set var g=4
17125 @value{GDBN} allows more implicit conversions in assignments than C; you can
17126 freely store an integer value into a pointer variable or vice versa,
17127 and you can convert any structure to any other structure that is the
17128 same length or shorter.
17129 @comment FIXME: how do structs align/pad in these conversions?
17130 @comment /doc@cygnus.com 18dec1990
17132 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
17133 construct to generate a value of specified type at a specified address
17134 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
17135 to memory location @code{0x83040} as an integer (which implies a certain size
17136 and representation in memory), and
17139 set @{int@}0x83040 = 4
17143 stores the value 4 into that memory location.
17146 @section Continuing at a Different Address
17148 Ordinarily, when you continue your program, you do so at the place where
17149 it stopped, with the @code{continue} command. You can instead continue at
17150 an address of your own choosing, with the following commands:
17154 @kindex j @r{(@code{jump})}
17155 @item jump @var{location}
17156 @itemx j @var{location}
17157 Resume execution at @var{location}. Execution stops again immediately
17158 if there is a breakpoint there. @xref{Specify Location}, for a description
17159 of the different forms of @var{location}. It is common
17160 practice to use the @code{tbreak} command in conjunction with
17161 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
17163 The @code{jump} command does not change the current stack frame, or
17164 the stack pointer, or the contents of any memory location or any
17165 register other than the program counter. If @var{location} is in
17166 a different function from the one currently executing, the results may
17167 be bizarre if the two functions expect different patterns of arguments or
17168 of local variables. For this reason, the @code{jump} command requests
17169 confirmation if the specified line is not in the function currently
17170 executing. However, even bizarre results are predictable if you are
17171 well acquainted with the machine-language code of your program.
17174 On many systems, you can get much the same effect as the @code{jump}
17175 command by storing a new value into the register @code{$pc}. The
17176 difference is that this does not start your program running; it only
17177 changes the address of where it @emph{will} run when you continue. For
17185 makes the next @code{continue} command or stepping command execute at
17186 address @code{0x485}, rather than at the address where your program stopped.
17187 @xref{Continuing and Stepping, ,Continuing and Stepping}.
17189 The most common occasion to use the @code{jump} command is to back
17190 up---perhaps with more breakpoints set---over a portion of a program
17191 that has already executed, in order to examine its execution in more
17196 @section Giving your Program a Signal
17197 @cindex deliver a signal to a program
17201 @item signal @var{signal}
17202 Resume execution where your program is stopped, but immediately give it the
17203 signal @var{signal}. The @var{signal} can be the name or the number of a
17204 signal. For example, on many systems @code{signal 2} and @code{signal
17205 SIGINT} are both ways of sending an interrupt signal.
17207 Alternatively, if @var{signal} is zero, continue execution without
17208 giving a signal. This is useful when your program stopped on account of
17209 a signal and would ordinarily see the signal when resumed with the
17210 @code{continue} command; @samp{signal 0} causes it to resume without a
17213 @emph{Note:} When resuming a multi-threaded program, @var{signal} is
17214 delivered to the currently selected thread, not the thread that last
17215 reported a stop. This includes the situation where a thread was
17216 stopped due to a signal. So if you want to continue execution
17217 suppressing the signal that stopped a thread, you should select that
17218 same thread before issuing the @samp{signal 0} command. If you issue
17219 the @samp{signal 0} command with another thread as the selected one,
17220 @value{GDBN} detects that and asks for confirmation.
17222 Invoking the @code{signal} command is not the same as invoking the
17223 @code{kill} utility from the shell. Sending a signal with @code{kill}
17224 causes @value{GDBN} to decide what to do with the signal depending on
17225 the signal handling tables (@pxref{Signals}). The @code{signal} command
17226 passes the signal directly to your program.
17228 @code{signal} does not repeat when you press @key{RET} a second time
17229 after executing the command.
17231 @kindex queue-signal
17232 @item queue-signal @var{signal}
17233 Queue @var{signal} to be delivered immediately to the current thread
17234 when execution of the thread resumes. The @var{signal} can be the name or
17235 the number of a signal. For example, on many systems @code{signal 2} and
17236 @code{signal SIGINT} are both ways of sending an interrupt signal.
17237 The handling of the signal must be set to pass the signal to the program,
17238 otherwise @value{GDBN} will report an error.
17239 You can control the handling of signals from @value{GDBN} with the
17240 @code{handle} command (@pxref{Signals}).
17242 Alternatively, if @var{signal} is zero, any currently queued signal
17243 for the current thread is discarded and when execution resumes no signal
17244 will be delivered. This is useful when your program stopped on account
17245 of a signal and would ordinarily see the signal when resumed with the
17246 @code{continue} command.
17248 This command differs from the @code{signal} command in that the signal
17249 is just queued, execution is not resumed. And @code{queue-signal} cannot
17250 be used to pass a signal whose handling state has been set to @code{nopass}
17255 @xref{stepping into signal handlers}, for information on how stepping
17256 commands behave when the thread has a signal queued.
17259 @section Returning from a Function
17262 @cindex returning from a function
17265 @itemx return @var{expression}
17266 You can cancel execution of a function call with the @code{return}
17267 command. If you give an
17268 @var{expression} argument, its value is used as the function's return
17272 When you use @code{return}, @value{GDBN} discards the selected stack frame
17273 (and all frames within it). You can think of this as making the
17274 discarded frame return prematurely. If you wish to specify a value to
17275 be returned, give that value as the argument to @code{return}.
17277 This pops the selected stack frame (@pxref{Selection, ,Selecting a
17278 Frame}), and any other frames inside of it, leaving its caller as the
17279 innermost remaining frame. That frame becomes selected. The
17280 specified value is stored in the registers used for returning values
17283 The @code{return} command does not resume execution; it leaves the
17284 program stopped in the state that would exist if the function had just
17285 returned. In contrast, the @code{finish} command (@pxref{Continuing
17286 and Stepping, ,Continuing and Stepping}) resumes execution until the
17287 selected stack frame returns naturally.
17289 @value{GDBN} needs to know how the @var{expression} argument should be set for
17290 the inferior. The concrete registers assignment depends on the OS ABI and the
17291 type being returned by the selected stack frame. For example it is common for
17292 OS ABI to return floating point values in FPU registers while integer values in
17293 CPU registers. Still some ABIs return even floating point values in CPU
17294 registers. Larger integer widths (such as @code{long long int}) also have
17295 specific placement rules. @value{GDBN} already knows the OS ABI from its
17296 current target so it needs to find out also the type being returned to make the
17297 assignment into the right register(s).
17299 Normally, the selected stack frame has debug info. @value{GDBN} will always
17300 use the debug info instead of the implicit type of @var{expression} when the
17301 debug info is available. For example, if you type @kbd{return -1}, and the
17302 function in the current stack frame is declared to return a @code{long long
17303 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
17304 into a @code{long long int}:
17307 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
17309 (@value{GDBP}) return -1
17310 Make func return now? (y or n) y
17311 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
17312 43 printf ("result=%lld\n", func ());
17316 However, if the selected stack frame does not have a debug info, e.g., if the
17317 function was compiled without debug info, @value{GDBN} has to find out the type
17318 to return from user. Specifying a different type by mistake may set the value
17319 in different inferior registers than the caller code expects. For example,
17320 typing @kbd{return -1} with its implicit type @code{int} would set only a part
17321 of a @code{long long int} result for a debug info less function (on 32-bit
17322 architectures). Therefore the user is required to specify the return type by
17323 an appropriate cast explicitly:
17326 Breakpoint 2, 0x0040050b in func ()
17327 (@value{GDBP}) return -1
17328 Return value type not available for selected stack frame.
17329 Please use an explicit cast of the value to return.
17330 (@value{GDBP}) return (long long int) -1
17331 Make selected stack frame return now? (y or n) y
17332 #0 0x00400526 in main ()
17337 @section Calling Program Functions
17340 @cindex calling functions
17341 @cindex inferior functions, calling
17342 @item print @var{expr}
17343 Evaluate the expression @var{expr} and display the resulting value.
17344 The expression may include calls to functions in the program being
17348 @item call @var{expr}
17349 Evaluate the expression @var{expr} without displaying @code{void}
17352 You can use this variant of the @code{print} command if you want to
17353 execute a function from your program that does not return anything
17354 (a.k.a.@: @dfn{a void function}), but without cluttering the output
17355 with @code{void} returned values that @value{GDBN} will otherwise
17356 print. If the result is not void, it is printed and saved in the
17360 It is possible for the function you call via the @code{print} or
17361 @code{call} command to generate a signal (e.g., if there's a bug in
17362 the function, or if you passed it incorrect arguments). What happens
17363 in that case is controlled by the @code{set unwindonsignal} command.
17365 Similarly, with a C@t{++} program it is possible for the function you
17366 call via the @code{print} or @code{call} command to generate an
17367 exception that is not handled due to the constraints of the dummy
17368 frame. In this case, any exception that is raised in the frame, but has
17369 an out-of-frame exception handler will not be found. GDB builds a
17370 dummy-frame for the inferior function call, and the unwinder cannot
17371 seek for exception handlers outside of this dummy-frame. What happens
17372 in that case is controlled by the
17373 @code{set unwind-on-terminating-exception} command.
17376 @item set unwindonsignal
17377 @kindex set unwindonsignal
17378 @cindex unwind stack in called functions
17379 @cindex call dummy stack unwinding
17380 Set unwinding of the stack if a signal is received while in a function
17381 that @value{GDBN} called in the program being debugged. If set to on,
17382 @value{GDBN} unwinds the stack it created for the call and restores
17383 the context to what it was before the call. If set to off (the
17384 default), @value{GDBN} stops in the frame where the signal was
17387 @item show unwindonsignal
17388 @kindex show unwindonsignal
17389 Show the current setting of stack unwinding in the functions called by
17392 @item set unwind-on-terminating-exception
17393 @kindex set unwind-on-terminating-exception
17394 @cindex unwind stack in called functions with unhandled exceptions
17395 @cindex call dummy stack unwinding on unhandled exception.
17396 Set unwinding of the stack if a C@t{++} exception is raised, but left
17397 unhandled while in a function that @value{GDBN} called in the program being
17398 debugged. If set to on (the default), @value{GDBN} unwinds the stack
17399 it created for the call and restores the context to what it was before
17400 the call. If set to off, @value{GDBN} the exception is delivered to
17401 the default C@t{++} exception handler and the inferior terminated.
17403 @item show unwind-on-terminating-exception
17404 @kindex show unwind-on-terminating-exception
17405 Show the current setting of stack unwinding in the functions called by
17410 @cindex weak alias functions
17411 Sometimes, a function you wish to call is actually a @dfn{weak alias}
17412 for another function. In such case, @value{GDBN} might not pick up
17413 the type information, including the types of the function arguments,
17414 which causes @value{GDBN} to call the inferior function incorrectly.
17415 As a result, the called function will function erroneously and may
17416 even crash. A solution to that is to use the name of the aliased
17420 @section Patching Programs
17422 @cindex patching binaries
17423 @cindex writing into executables
17424 @cindex writing into corefiles
17426 By default, @value{GDBN} opens the file containing your program's
17427 executable code (or the corefile) read-only. This prevents accidental
17428 alterations to machine code; but it also prevents you from intentionally
17429 patching your program's binary.
17431 If you'd like to be able to patch the binary, you can specify that
17432 explicitly with the @code{set write} command. For example, you might
17433 want to turn on internal debugging flags, or even to make emergency
17439 @itemx set write off
17440 If you specify @samp{set write on}, @value{GDBN} opens executable and
17441 core files for both reading and writing; if you specify @kbd{set write
17442 off} (the default), @value{GDBN} opens them read-only.
17444 If you have already loaded a file, you must load it again (using the
17445 @code{exec-file} or @code{core-file} command) after changing @code{set
17446 write}, for your new setting to take effect.
17450 Display whether executable files and core files are opened for writing
17451 as well as reading.
17454 @node Compiling and Injecting Code
17455 @section Compiling and injecting code in @value{GDBN}
17456 @cindex injecting code
17457 @cindex writing into executables
17458 @cindex compiling code
17460 @value{GDBN} supports on-demand compilation and code injection into
17461 programs running under @value{GDBN}. GCC 5.0 or higher built with
17462 @file{libcc1.so} must be installed for this functionality to be enabled.
17463 This functionality is implemented with the following commands.
17466 @kindex compile code
17467 @item compile code @var{source-code}
17468 @itemx compile code -raw @var{--} @var{source-code}
17469 Compile @var{source-code} with the compiler language found as the current
17470 language in @value{GDBN} (@pxref{Languages}). If compilation and
17471 injection is not supported with the current language specified in
17472 @value{GDBN}, or the compiler does not support this feature, an error
17473 message will be printed. If @var{source-code} compiles and links
17474 successfully, @value{GDBN} will load the object-code emitted,
17475 and execute it within the context of the currently selected inferior.
17476 It is important to note that the compiled code is executed immediately.
17477 After execution, the compiled code is removed from @value{GDBN} and any
17478 new types or variables you have defined will be deleted.
17480 The command allows you to specify @var{source-code} in two ways.
17481 The simplest method is to provide a single line of code to the command.
17485 compile code printf ("hello world\n");
17488 If you specify options on the command line as well as source code, they
17489 may conflict. The @samp{--} delimiter can be used to separate options
17490 from actual source code. E.g.:
17493 compile code -r -- printf ("hello world\n");
17496 Alternatively you can enter source code as multiple lines of text. To
17497 enter this mode, invoke the @samp{compile code} command without any text
17498 following the command. This will start the multiple-line editor and
17499 allow you to type as many lines of source code as required. When you
17500 have completed typing, enter @samp{end} on its own line to exit the
17505 >printf ("hello\n");
17506 >printf ("world\n");
17510 Specifying @samp{-raw}, prohibits @value{GDBN} from wrapping the
17511 provided @var{source-code} in a callable scope. In this case, you must
17512 specify the entry point of the code by defining a function named
17513 @code{_gdb_expr_}. The @samp{-raw} code cannot access variables of the
17514 inferior. Using @samp{-raw} option may be needed for example when
17515 @var{source-code} requires @samp{#include} lines which may conflict with
17516 inferior symbols otherwise.
17518 @kindex compile file
17519 @item compile file @var{filename}
17520 @itemx compile file -raw @var{filename}
17521 Like @code{compile code}, but take the source code from @var{filename}.
17524 compile file /home/user/example.c
17529 @item compile print @var{expr}
17530 @itemx compile print /@var{f} @var{expr}
17531 Compile and execute @var{expr} with the compiler language found as the
17532 current language in @value{GDBN} (@pxref{Languages}). By default the
17533 value of @var{expr} is printed in a format appropriate to its data type;
17534 you can choose a different format by specifying @samp{/@var{f}}, where
17535 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
17538 @item compile print
17539 @itemx compile print /@var{f}
17540 @cindex reprint the last value
17541 Alternatively you can enter the expression (source code producing it) as
17542 multiple lines of text. To enter this mode, invoke the @samp{compile print}
17543 command without any text following the command. This will start the
17544 multiple-line editor.
17548 The process of compiling and injecting the code can be inspected using:
17551 @anchor{set debug compile}
17552 @item set debug compile
17553 @cindex compile command debugging info
17554 Turns on or off display of @value{GDBN} process of compiling and
17555 injecting the code. The default is off.
17557 @item show debug compile
17558 Displays the current state of displaying @value{GDBN} process of
17559 compiling and injecting the code.
17562 @subsection Compilation options for the @code{compile} command
17564 @value{GDBN} needs to specify the right compilation options for the code
17565 to be injected, in part to make its ABI compatible with the inferior
17566 and in part to make the injected code compatible with @value{GDBN}'s
17570 The options used, in increasing precedence:
17573 @item target architecture and OS options (@code{gdbarch})
17574 These options depend on target processor type and target operating
17575 system, usually they specify at least 32-bit (@code{-m32}) or 64-bit
17576 (@code{-m64}) compilation option.
17578 @item compilation options recorded in the target
17579 @value{NGCC} (since version 4.7) stores the options used for compilation
17580 into @code{DW_AT_producer} part of DWARF debugging information according
17581 to the @value{NGCC} option @code{-grecord-gcc-switches}. One has to
17582 explicitly specify @code{-g} during inferior compilation otherwise
17583 @value{NGCC} produces no DWARF. This feature is only relevant for
17584 platforms where @code{-g} produces DWARF by default, otherwise one may
17585 try to enforce DWARF by using @code{-gdwarf-4}.
17587 @item compilation options set by @code{set compile-args}
17591 You can override compilation options using the following command:
17594 @item set compile-args
17595 @cindex compile command options override
17596 Set compilation options used for compiling and injecting code with the
17597 @code{compile} commands. These options override any conflicting ones
17598 from the target architecture and/or options stored during inferior
17601 @item show compile-args
17602 Displays the current state of compilation options override.
17603 This does not show all the options actually used during compilation,
17604 use @ref{set debug compile} for that.
17607 @subsection Caveats when using the @code{compile} command
17609 There are a few caveats to keep in mind when using the @code{compile}
17610 command. As the caveats are different per language, the table below
17611 highlights specific issues on a per language basis.
17614 @item C code examples and caveats
17615 When the language in @value{GDBN} is set to @samp{C}, the compiler will
17616 attempt to compile the source code with a @samp{C} compiler. The source
17617 code provided to the @code{compile} command will have much the same
17618 access to variables and types as it normally would if it were part of
17619 the program currently being debugged in @value{GDBN}.
17621 Below is a sample program that forms the basis of the examples that
17622 follow. This program has been compiled and loaded into @value{GDBN},
17623 much like any other normal debugging session.
17626 void function1 (void)
17629 printf ("function 1\n");
17632 void function2 (void)
17647 For the purposes of the examples in this section, the program above has
17648 been compiled, loaded into @value{GDBN}, stopped at the function
17649 @code{main}, and @value{GDBN} is awaiting input from the user.
17651 To access variables and types for any program in @value{GDBN}, the
17652 program must be compiled and packaged with debug information. The
17653 @code{compile} command is not an exception to this rule. Without debug
17654 information, you can still use the @code{compile} command, but you will
17655 be very limited in what variables and types you can access.
17657 So with that in mind, the example above has been compiled with debug
17658 information enabled. The @code{compile} command will have access to
17659 all variables and types (except those that may have been optimized
17660 out). Currently, as @value{GDBN} has stopped the program in the
17661 @code{main} function, the @code{compile} command would have access to
17662 the variable @code{k}. You could invoke the @code{compile} command
17663 and type some source code to set the value of @code{k}. You can also
17664 read it, or do anything with that variable you would normally do in
17665 @code{C}. Be aware that changes to inferior variables in the
17666 @code{compile} command are persistent. In the following example:
17669 compile code k = 3;
17673 the variable @code{k} is now 3. It will retain that value until
17674 something else in the example program changes it, or another
17675 @code{compile} command changes it.
17677 Normal scope and access rules apply to source code compiled and
17678 injected by the @code{compile} command. In the example, the variables
17679 @code{j} and @code{k} are not accessible yet, because the program is
17680 currently stopped in the @code{main} function, where these variables
17681 are not in scope. Therefore, the following command
17684 compile code j = 3;
17688 will result in a compilation error message.
17690 Once the program is continued, execution will bring these variables in
17691 scope, and they will become accessible; then the code you specify via
17692 the @code{compile} command will be able to access them.
17694 You can create variables and types with the @code{compile} command as
17695 part of your source code. Variables and types that are created as part
17696 of the @code{compile} command are not visible to the rest of the program for
17697 the duration of its run. This example is valid:
17700 compile code int ff = 5; printf ("ff is %d\n", ff);
17703 However, if you were to type the following into @value{GDBN} after that
17704 command has completed:
17707 compile code printf ("ff is %d\n'', ff);
17711 a compiler error would be raised as the variable @code{ff} no longer
17712 exists. Object code generated and injected by the @code{compile}
17713 command is removed when its execution ends. Caution is advised
17714 when assigning to program variables values of variables created by the
17715 code submitted to the @code{compile} command. This example is valid:
17718 compile code int ff = 5; k = ff;
17721 The value of the variable @code{ff} is assigned to @code{k}. The variable
17722 @code{k} does not require the existence of @code{ff} to maintain the value
17723 it has been assigned. However, pointers require particular care in
17724 assignment. If the source code compiled with the @code{compile} command
17725 changed the address of a pointer in the example program, perhaps to a
17726 variable created in the @code{compile} command, that pointer would point
17727 to an invalid location when the command exits. The following example
17728 would likely cause issues with your debugged program:
17731 compile code int ff = 5; p = &ff;
17734 In this example, @code{p} would point to @code{ff} when the
17735 @code{compile} command is executing the source code provided to it.
17736 However, as variables in the (example) program persist with their
17737 assigned values, the variable @code{p} would point to an invalid
17738 location when the command exists. A general rule should be followed
17739 in that you should either assign @code{NULL} to any assigned pointers,
17740 or restore a valid location to the pointer before the command exits.
17742 Similar caution must be exercised with any structs, unions, and typedefs
17743 defined in @code{compile} command. Types defined in the @code{compile}
17744 command will no longer be available in the next @code{compile} command.
17745 Therefore, if you cast a variable to a type defined in the
17746 @code{compile} command, care must be taken to ensure that any future
17747 need to resolve the type can be achieved.
17750 (gdb) compile code static struct a @{ int a; @} v = @{ 42 @}; argv = &v;
17751 (gdb) compile code printf ("%d\n", ((struct a *) argv)->a);
17752 gdb command line:1:36: error: dereferencing pointer to incomplete type ‘struct a’
17753 Compilation failed.
17754 (gdb) compile code struct a @{ int a; @}; printf ("%d\n", ((struct a *) argv)->a);
17758 Variables that have been optimized away by the compiler are not
17759 accessible to the code submitted to the @code{compile} command.
17760 Access to those variables will generate a compiler error which @value{GDBN}
17761 will print to the console.
17764 @subsection Compiler search for the @code{compile} command
17766 @value{GDBN} needs to find @value{NGCC} for the inferior being debugged which
17767 may not be obvious for remote targets of different architecture than where
17768 @value{GDBN} is running. Environment variable @code{PATH} (@code{PATH} from
17769 shell that executed @value{GDBN}, not the one set by @value{GDBN}
17770 command @code{set environment}). @xref{Environment}. @code{PATH} on
17771 @value{GDBN} host is searched for @value{NGCC} binary matching the
17772 target architecture and operating system.
17774 Specifically @code{PATH} is searched for binaries matching regular expression
17775 @code{@var{arch}(-[^-]*)?-@var{os}-gcc} according to the inferior target being
17776 debugged. @var{arch} is processor name --- multiarch is supported, so for
17777 example both @code{i386} and @code{x86_64} targets look for pattern
17778 @code{(x86_64|i.86)} and both @code{s390} and @code{s390x} targets look
17779 for pattern @code{s390x?}. @var{os} is currently supported only for
17780 pattern @code{linux(-gnu)?}.
17783 @chapter @value{GDBN} Files
17785 @value{GDBN} needs to know the file name of the program to be debugged,
17786 both in order to read its symbol table and in order to start your
17787 program. To debug a core dump of a previous run, you must also tell
17788 @value{GDBN} the name of the core dump file.
17791 * Files:: Commands to specify files
17792 * File Caching:: Information about @value{GDBN}'s file caching
17793 * Separate Debug Files:: Debugging information in separate files
17794 * MiniDebugInfo:: Debugging information in a special section
17795 * Index Files:: Index files speed up GDB
17796 * Symbol Errors:: Errors reading symbol files
17797 * Data Files:: GDB data files
17801 @section Commands to Specify Files
17803 @cindex symbol table
17804 @cindex core dump file
17806 You may want to specify executable and core dump file names. The usual
17807 way to do this is at start-up time, using the arguments to
17808 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
17809 Out of @value{GDBN}}).
17811 Occasionally it is necessary to change to a different file during a
17812 @value{GDBN} session. Or you may run @value{GDBN} and forget to
17813 specify a file you want to use. Or you are debugging a remote target
17814 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
17815 Program}). In these situations the @value{GDBN} commands to specify
17816 new files are useful.
17819 @cindex executable file
17821 @item file @var{filename}
17822 Use @var{filename} as the program to be debugged. It is read for its
17823 symbols and for the contents of pure memory. It is also the program
17824 executed when you use the @code{run} command. If you do not specify a
17825 directory and the file is not found in the @value{GDBN} working directory,
17826 @value{GDBN} uses the environment variable @code{PATH} as a list of
17827 directories to search, just as the shell does when looking for a program
17828 to run. You can change the value of this variable, for both @value{GDBN}
17829 and your program, using the @code{path} command.
17831 @cindex unlinked object files
17832 @cindex patching object files
17833 You can load unlinked object @file{.o} files into @value{GDBN} using
17834 the @code{file} command. You will not be able to ``run'' an object
17835 file, but you can disassemble functions and inspect variables. Also,
17836 if the underlying BFD functionality supports it, you could use
17837 @kbd{gdb -write} to patch object files using this technique. Note
17838 that @value{GDBN} can neither interpret nor modify relocations in this
17839 case, so branches and some initialized variables will appear to go to
17840 the wrong place. But this feature is still handy from time to time.
17843 @code{file} with no argument makes @value{GDBN} discard any information it
17844 has on both executable file and the symbol table.
17847 @item exec-file @r{[} @var{filename} @r{]}
17848 Specify that the program to be run (but not the symbol table) is found
17849 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
17850 if necessary to locate your program. Omitting @var{filename} means to
17851 discard information on the executable file.
17853 @kindex symbol-file
17854 @item symbol-file @r{[} @var{filename} @r{]}
17855 Read symbol table information from file @var{filename}. @code{PATH} is
17856 searched when necessary. Use the @code{file} command to get both symbol
17857 table and program to run from the same file.
17859 @code{symbol-file} with no argument clears out @value{GDBN} information on your
17860 program's symbol table.
17862 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
17863 some breakpoints and auto-display expressions. This is because they may
17864 contain pointers to the internal data recording symbols and data types,
17865 which are part of the old symbol table data being discarded inside
17868 @code{symbol-file} does not repeat if you press @key{RET} again after
17871 When @value{GDBN} is configured for a particular environment, it
17872 understands debugging information in whatever format is the standard
17873 generated for that environment; you may use either a @sc{gnu} compiler, or
17874 other compilers that adhere to the local conventions.
17875 Best results are usually obtained from @sc{gnu} compilers; for example,
17876 using @code{@value{NGCC}} you can generate debugging information for
17879 For most kinds of object files, with the exception of old SVR3 systems
17880 using COFF, the @code{symbol-file} command does not normally read the
17881 symbol table in full right away. Instead, it scans the symbol table
17882 quickly to find which source files and which symbols are present. The
17883 details are read later, one source file at a time, as they are needed.
17885 The purpose of this two-stage reading strategy is to make @value{GDBN}
17886 start up faster. For the most part, it is invisible except for
17887 occasional pauses while the symbol table details for a particular source
17888 file are being read. (The @code{set verbose} command can turn these
17889 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
17890 Warnings and Messages}.)
17892 We have not implemented the two-stage strategy for COFF yet. When the
17893 symbol table is stored in COFF format, @code{symbol-file} reads the
17894 symbol table data in full right away. Note that ``stabs-in-COFF''
17895 still does the two-stage strategy, since the debug info is actually
17899 @cindex reading symbols immediately
17900 @cindex symbols, reading immediately
17901 @item symbol-file @r{[} -readnow @r{]} @var{filename}
17902 @itemx file @r{[} -readnow @r{]} @var{filename}
17903 You can override the @value{GDBN} two-stage strategy for reading symbol
17904 tables by using the @samp{-readnow} option with any of the commands that
17905 load symbol table information, if you want to be sure @value{GDBN} has the
17906 entire symbol table available.
17908 @c FIXME: for now no mention of directories, since this seems to be in
17909 @c flux. 13mar1992 status is that in theory GDB would look either in
17910 @c current dir or in same dir as myprog; but issues like competing
17911 @c GDB's, or clutter in system dirs, mean that in practice right now
17912 @c only current dir is used. FFish says maybe a special GDB hierarchy
17913 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
17917 @item core-file @r{[}@var{filename}@r{]}
17919 Specify the whereabouts of a core dump file to be used as the ``contents
17920 of memory''. Traditionally, core files contain only some parts of the
17921 address space of the process that generated them; @value{GDBN} can access the
17922 executable file itself for other parts.
17924 @code{core-file} with no argument specifies that no core file is
17927 Note that the core file is ignored when your program is actually running
17928 under @value{GDBN}. So, if you have been running your program and you
17929 wish to debug a core file instead, you must kill the subprocess in which
17930 the program is running. To do this, use the @code{kill} command
17931 (@pxref{Kill Process, ,Killing the Child Process}).
17933 @kindex add-symbol-file
17934 @cindex dynamic linking
17935 @item add-symbol-file @var{filename} @var{address}
17936 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
17937 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
17938 The @code{add-symbol-file} command reads additional symbol table
17939 information from the file @var{filename}. You would use this command
17940 when @var{filename} has been dynamically loaded (by some other means)
17941 into the program that is running. The @var{address} should give the memory
17942 address at which the file has been loaded; @value{GDBN} cannot figure
17943 this out for itself. You can additionally specify an arbitrary number
17944 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
17945 section name and base address for that section. You can specify any
17946 @var{address} as an expression.
17948 The symbol table of the file @var{filename} is added to the symbol table
17949 originally read with the @code{symbol-file} command. You can use the
17950 @code{add-symbol-file} command any number of times; the new symbol data
17951 thus read is kept in addition to the old.
17953 Changes can be reverted using the command @code{remove-symbol-file}.
17955 @cindex relocatable object files, reading symbols from
17956 @cindex object files, relocatable, reading symbols from
17957 @cindex reading symbols from relocatable object files
17958 @cindex symbols, reading from relocatable object files
17959 @cindex @file{.o} files, reading symbols from
17960 Although @var{filename} is typically a shared library file, an
17961 executable file, or some other object file which has been fully
17962 relocated for loading into a process, you can also load symbolic
17963 information from relocatable @file{.o} files, as long as:
17967 the file's symbolic information refers only to linker symbols defined in
17968 that file, not to symbols defined by other object files,
17970 every section the file's symbolic information refers to has actually
17971 been loaded into the inferior, as it appears in the file, and
17973 you can determine the address at which every section was loaded, and
17974 provide these to the @code{add-symbol-file} command.
17978 Some embedded operating systems, like Sun Chorus and VxWorks, can load
17979 relocatable files into an already running program; such systems
17980 typically make the requirements above easy to meet. However, it's
17981 important to recognize that many native systems use complex link
17982 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
17983 assembly, for example) that make the requirements difficult to meet. In
17984 general, one cannot assume that using @code{add-symbol-file} to read a
17985 relocatable object file's symbolic information will have the same effect
17986 as linking the relocatable object file into the program in the normal
17989 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
17991 @kindex remove-symbol-file
17992 @item remove-symbol-file @var{filename}
17993 @item remove-symbol-file -a @var{address}
17994 Remove a symbol file added via the @code{add-symbol-file} command. The
17995 file to remove can be identified by its @var{filename} or by an @var{address}
17996 that lies within the boundaries of this symbol file in memory. Example:
17999 (gdb) add-symbol-file /home/user/gdb/mylib.so 0x7ffff7ff9480
18000 add symbol table from file "/home/user/gdb/mylib.so" at
18001 .text_addr = 0x7ffff7ff9480
18003 Reading symbols from /home/user/gdb/mylib.so...done.
18004 (gdb) remove-symbol-file -a 0x7ffff7ff9480
18005 Remove symbol table from file "/home/user/gdb/mylib.so"? (y or n) y
18010 @code{remove-symbol-file} does not repeat if you press @key{RET} after using it.
18012 @kindex add-symbol-file-from-memory
18013 @cindex @code{syscall DSO}
18014 @cindex load symbols from memory
18015 @item add-symbol-file-from-memory @var{address}
18016 Load symbols from the given @var{address} in a dynamically loaded
18017 object file whose image is mapped directly into the inferior's memory.
18018 For example, the Linux kernel maps a @code{syscall DSO} into each
18019 process's address space; this DSO provides kernel-specific code for
18020 some system calls. The argument can be any expression whose
18021 evaluation yields the address of the file's shared object file header.
18022 For this command to work, you must have used @code{symbol-file} or
18023 @code{exec-file} commands in advance.
18026 @item section @var{section} @var{addr}
18027 The @code{section} command changes the base address of the named
18028 @var{section} of the exec file to @var{addr}. This can be used if the
18029 exec file does not contain section addresses, (such as in the
18030 @code{a.out} format), or when the addresses specified in the file
18031 itself are wrong. Each section must be changed separately. The
18032 @code{info files} command, described below, lists all the sections and
18036 @kindex info target
18039 @code{info files} and @code{info target} are synonymous; both print the
18040 current target (@pxref{Targets, ,Specifying a Debugging Target}),
18041 including the names of the executable and core dump files currently in
18042 use by @value{GDBN}, and the files from which symbols were loaded. The
18043 command @code{help target} lists all possible targets rather than
18046 @kindex maint info sections
18047 @item maint info sections
18048 Another command that can give you extra information about program sections
18049 is @code{maint info sections}. In addition to the section information
18050 displayed by @code{info files}, this command displays the flags and file
18051 offset of each section in the executable and core dump files. In addition,
18052 @code{maint info sections} provides the following command options (which
18053 may be arbitrarily combined):
18057 Display sections for all loaded object files, including shared libraries.
18058 @item @var{sections}
18059 Display info only for named @var{sections}.
18060 @item @var{section-flags}
18061 Display info only for sections for which @var{section-flags} are true.
18062 The section flags that @value{GDBN} currently knows about are:
18065 Section will have space allocated in the process when loaded.
18066 Set for all sections except those containing debug information.
18068 Section will be loaded from the file into the child process memory.
18069 Set for pre-initialized code and data, clear for @code{.bss} sections.
18071 Section needs to be relocated before loading.
18073 Section cannot be modified by the child process.
18075 Section contains executable code only.
18077 Section contains data only (no executable code).
18079 Section will reside in ROM.
18081 Section contains data for constructor/destructor lists.
18083 Section is not empty.
18085 An instruction to the linker to not output the section.
18086 @item COFF_SHARED_LIBRARY
18087 A notification to the linker that the section contains
18088 COFF shared library information.
18090 Section contains common symbols.
18093 @kindex set trust-readonly-sections
18094 @cindex read-only sections
18095 @item set trust-readonly-sections on
18096 Tell @value{GDBN} that readonly sections in your object file
18097 really are read-only (i.e.@: that their contents will not change).
18098 In that case, @value{GDBN} can fetch values from these sections
18099 out of the object file, rather than from the target program.
18100 For some targets (notably embedded ones), this can be a significant
18101 enhancement to debugging performance.
18103 The default is off.
18105 @item set trust-readonly-sections off
18106 Tell @value{GDBN} not to trust readonly sections. This means that
18107 the contents of the section might change while the program is running,
18108 and must therefore be fetched from the target when needed.
18110 @item show trust-readonly-sections
18111 Show the current setting of trusting readonly sections.
18114 All file-specifying commands allow both absolute and relative file names
18115 as arguments. @value{GDBN} always converts the file name to an absolute file
18116 name and remembers it that way.
18118 @cindex shared libraries
18119 @anchor{Shared Libraries}
18120 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, SunOS,
18121 Darwin/Mach-O, SVr4, IBM RS/6000 AIX, QNX Neutrino, FDPIC (FR-V), and
18122 DSBT (TIC6X) shared libraries.
18124 On MS-Windows @value{GDBN} must be linked with the Expat library to support
18125 shared libraries. @xref{Expat}.
18127 @value{GDBN} automatically loads symbol definitions from shared libraries
18128 when you use the @code{run} command, or when you examine a core file.
18129 (Before you issue the @code{run} command, @value{GDBN} does not understand
18130 references to a function in a shared library, however---unless you are
18131 debugging a core file).
18133 @c FIXME: some @value{GDBN} release may permit some refs to undef
18134 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
18135 @c FIXME...lib; check this from time to time when updating manual
18137 There are times, however, when you may wish to not automatically load
18138 symbol definitions from shared libraries, such as when they are
18139 particularly large or there are many of them.
18141 To control the automatic loading of shared library symbols, use the
18145 @kindex set auto-solib-add
18146 @item set auto-solib-add @var{mode}
18147 If @var{mode} is @code{on}, symbols from all shared object libraries
18148 will be loaded automatically when the inferior begins execution, you
18149 attach to an independently started inferior, or when the dynamic linker
18150 informs @value{GDBN} that a new library has been loaded. If @var{mode}
18151 is @code{off}, symbols must be loaded manually, using the
18152 @code{sharedlibrary} command. The default value is @code{on}.
18154 @cindex memory used for symbol tables
18155 If your program uses lots of shared libraries with debug info that
18156 takes large amounts of memory, you can decrease the @value{GDBN}
18157 memory footprint by preventing it from automatically loading the
18158 symbols from shared libraries. To that end, type @kbd{set
18159 auto-solib-add off} before running the inferior, then load each
18160 library whose debug symbols you do need with @kbd{sharedlibrary
18161 @var{regexp}}, where @var{regexp} is a regular expression that matches
18162 the libraries whose symbols you want to be loaded.
18164 @kindex show auto-solib-add
18165 @item show auto-solib-add
18166 Display the current autoloading mode.
18169 @cindex load shared library
18170 To explicitly load shared library symbols, use the @code{sharedlibrary}
18174 @kindex info sharedlibrary
18176 @item info share @var{regex}
18177 @itemx info sharedlibrary @var{regex}
18178 Print the names of the shared libraries which are currently loaded
18179 that match @var{regex}. If @var{regex} is omitted then print
18180 all shared libraries that are loaded.
18183 @item info dll @var{regex}
18184 This is an alias of @code{info sharedlibrary}.
18186 @kindex sharedlibrary
18188 @item sharedlibrary @var{regex}
18189 @itemx share @var{regex}
18190 Load shared object library symbols for files matching a
18191 Unix regular expression.
18192 As with files loaded automatically, it only loads shared libraries
18193 required by your program for a core file or after typing @code{run}. If
18194 @var{regex} is omitted all shared libraries required by your program are
18197 @item nosharedlibrary
18198 @kindex nosharedlibrary
18199 @cindex unload symbols from shared libraries
18200 Unload all shared object library symbols. This discards all symbols
18201 that have been loaded from all shared libraries. Symbols from shared
18202 libraries that were loaded by explicit user requests are not
18206 Sometimes you may wish that @value{GDBN} stops and gives you control
18207 when any of shared library events happen. The best way to do this is
18208 to use @code{catch load} and @code{catch unload} (@pxref{Set
18211 @value{GDBN} also supports the the @code{set stop-on-solib-events}
18212 command for this. This command exists for historical reasons. It is
18213 less useful than setting a catchpoint, because it does not allow for
18214 conditions or commands as a catchpoint does.
18217 @item set stop-on-solib-events
18218 @kindex set stop-on-solib-events
18219 This command controls whether @value{GDBN} should give you control
18220 when the dynamic linker notifies it about some shared library event.
18221 The most common event of interest is loading or unloading of a new
18224 @item show stop-on-solib-events
18225 @kindex show stop-on-solib-events
18226 Show whether @value{GDBN} stops and gives you control when shared
18227 library events happen.
18230 Shared libraries are also supported in many cross or remote debugging
18231 configurations. @value{GDBN} needs to have access to the target's libraries;
18232 this can be accomplished either by providing copies of the libraries
18233 on the host system, or by asking @value{GDBN} to automatically retrieve the
18234 libraries from the target. If copies of the target libraries are
18235 provided, they need to be the same as the target libraries, although the
18236 copies on the target can be stripped as long as the copies on the host are
18239 @cindex where to look for shared libraries
18240 For remote debugging, you need to tell @value{GDBN} where the target
18241 libraries are, so that it can load the correct copies---otherwise, it
18242 may try to load the host's libraries. @value{GDBN} has two variables
18243 to specify the search directories for target libraries.
18246 @cindex prefix for executable and shared library file names
18247 @cindex system root, alternate
18248 @kindex set solib-absolute-prefix
18249 @kindex set sysroot
18250 @item set sysroot @var{path}
18251 Use @var{path} as the system root for the program being debugged. Any
18252 absolute shared library paths will be prefixed with @var{path}; many
18253 runtime loaders store the absolute paths to the shared library in the
18254 target program's memory. When starting processes remotely, and when
18255 attaching to already-running processes (local or remote), their
18256 executable filenames will be prefixed with @var{path} if reported to
18257 @value{GDBN} as absolute by the operating system. If you use
18258 @code{set sysroot} to find executables and shared libraries, they need
18259 to be laid out in the same way that they are on the target, with
18260 e.g.@: a @file{/bin}, @file{/lib} and @file{/usr/lib} hierarchy under
18263 If @var{path} starts with the sequence @file{target:} and the target
18264 system is remote then @value{GDBN} will retrieve the target binaries
18265 from the remote system. This is only supported when using a remote
18266 target that supports the @code{remote get} command (@pxref{File
18267 Transfer,,Sending files to a remote system}). The part of @var{path}
18268 following the initial @file{target:} (if present) is used as system
18269 root prefix on the remote file system. If @var{path} starts with the
18270 sequence @file{remote:} this is converted to the sequence
18271 @file{target:} by @code{set sysroot}@footnote{Historically the
18272 functionality to retrieve binaries from the remote system was
18273 provided by prefixing @var{path} with @file{remote:}}. If you want
18274 to specify a local system root using a directory that happens to be
18275 named @file{target:} or @file{remote:}, you need to use some
18276 equivalent variant of the name like @file{./target:}.
18278 For targets with an MS-DOS based filesystem, such as MS-Windows and
18279 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
18280 absolute file name with @var{path}. But first, on Unix hosts,
18281 @value{GDBN} converts all backslash directory separators into forward
18282 slashes, because the backslash is not a directory separator on Unix:
18285 c:\foo\bar.dll @result{} c:/foo/bar.dll
18288 Then, @value{GDBN} attempts prefixing the target file name with
18289 @var{path}, and looks for the resulting file name in the host file
18293 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
18296 If that does not find the binary, @value{GDBN} tries removing
18297 the @samp{:} character from the drive spec, both for convenience, and,
18298 for the case of the host file system not supporting file names with
18302 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
18305 This makes it possible to have a system root that mirrors a target
18306 with more than one drive. E.g., you may want to setup your local
18307 copies of the target system shared libraries like so (note @samp{c} vs
18311 @file{/path/to/sysroot/c/sys/bin/foo.dll}
18312 @file{/path/to/sysroot/c/sys/bin/bar.dll}
18313 @file{/path/to/sysroot/z/sys/bin/bar.dll}
18317 and point the system root at @file{/path/to/sysroot}, so that
18318 @value{GDBN} can find the correct copies of both
18319 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
18321 If that still does not find the binary, @value{GDBN} tries
18322 removing the whole drive spec from the target file name:
18325 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
18328 This last lookup makes it possible to not care about the drive name,
18329 if you don't want or need to.
18331 The @code{set solib-absolute-prefix} command is an alias for @code{set
18334 @cindex default system root
18335 @cindex @samp{--with-sysroot}
18336 You can set the default system root by using the configure-time
18337 @samp{--with-sysroot} option. If the system root is inside
18338 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
18339 @samp{--exec-prefix}), then the default system root will be updated
18340 automatically if the installed @value{GDBN} is moved to a new
18343 @kindex show sysroot
18345 Display the current executable and shared library prefix.
18347 @kindex set solib-search-path
18348 @item set solib-search-path @var{path}
18349 If this variable is set, @var{path} is a colon-separated list of
18350 directories to search for shared libraries. @samp{solib-search-path}
18351 is used after @samp{sysroot} fails to locate the library, or if the
18352 path to the library is relative instead of absolute. If you want to
18353 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
18354 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
18355 finding your host's libraries. @samp{sysroot} is preferred; setting
18356 it to a nonexistent directory may interfere with automatic loading
18357 of shared library symbols.
18359 @kindex show solib-search-path
18360 @item show solib-search-path
18361 Display the current shared library search path.
18363 @cindex DOS file-name semantics of file names.
18364 @kindex set target-file-system-kind (unix|dos-based|auto)
18365 @kindex show target-file-system-kind
18366 @item set target-file-system-kind @var{kind}
18367 Set assumed file system kind for target reported file names.
18369 Shared library file names as reported by the target system may not
18370 make sense as is on the system @value{GDBN} is running on. For
18371 example, when remote debugging a target that has MS-DOS based file
18372 system semantics, from a Unix host, the target may be reporting to
18373 @value{GDBN} a list of loaded shared libraries with file names such as
18374 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
18375 drive letters, so the @samp{c:\} prefix is not normally understood as
18376 indicating an absolute file name, and neither is the backslash
18377 normally considered a directory separator character. In that case,
18378 the native file system would interpret this whole absolute file name
18379 as a relative file name with no directory components. This would make
18380 it impossible to point @value{GDBN} at a copy of the remote target's
18381 shared libraries on the host using @code{set sysroot}, and impractical
18382 with @code{set solib-search-path}. Setting
18383 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
18384 to interpret such file names similarly to how the target would, and to
18385 map them to file names valid on @value{GDBN}'s native file system
18386 semantics. The value of @var{kind} can be @code{"auto"}, in addition
18387 to one of the supported file system kinds. In that case, @value{GDBN}
18388 tries to determine the appropriate file system variant based on the
18389 current target's operating system (@pxref{ABI, ,Configuring the
18390 Current ABI}). The supported file system settings are:
18394 Instruct @value{GDBN} to assume the target file system is of Unix
18395 kind. Only file names starting the forward slash (@samp{/}) character
18396 are considered absolute, and the directory separator character is also
18400 Instruct @value{GDBN} to assume the target file system is DOS based.
18401 File names starting with either a forward slash, or a drive letter
18402 followed by a colon (e.g., @samp{c:}), are considered absolute, and
18403 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
18404 considered directory separators.
18407 Instruct @value{GDBN} to use the file system kind associated with the
18408 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
18409 This is the default.
18413 @cindex file name canonicalization
18414 @cindex base name differences
18415 When processing file names provided by the user, @value{GDBN}
18416 frequently needs to compare them to the file names recorded in the
18417 program's debug info. Normally, @value{GDBN} compares just the
18418 @dfn{base names} of the files as strings, which is reasonably fast
18419 even for very large programs. (The base name of a file is the last
18420 portion of its name, after stripping all the leading directories.)
18421 This shortcut in comparison is based upon the assumption that files
18422 cannot have more than one base name. This is usually true, but
18423 references to files that use symlinks or similar filesystem
18424 facilities violate that assumption. If your program records files
18425 using such facilities, or if you provide file names to @value{GDBN}
18426 using symlinks etc., you can set @code{basenames-may-differ} to
18427 @code{true} to instruct @value{GDBN} to completely canonicalize each
18428 pair of file names it needs to compare. This will make file-name
18429 comparisons accurate, but at a price of a significant slowdown.
18432 @item set basenames-may-differ
18433 @kindex set basenames-may-differ
18434 Set whether a source file may have multiple base names.
18436 @item show basenames-may-differ
18437 @kindex show basenames-may-differ
18438 Show whether a source file may have multiple base names.
18442 @section File Caching
18443 @cindex caching of opened files
18444 @cindex caching of bfd objects
18446 To speed up file loading, and reduce memory usage, @value{GDBN} will
18447 reuse the @code{bfd} objects used to track open files. @xref{Top, ,
18448 BFD, bfd, The Binary File Descriptor Library}. The following commands
18449 allow visibility and control of the caching behavior.
18452 @kindex maint info bfds
18453 @item maint info bfds
18454 This prints information about each @code{bfd} object that is known to
18457 @kindex maint set bfd-sharing
18458 @kindex maint show bfd-sharing
18459 @kindex bfd caching
18460 @item maint set bfd-sharing
18461 @item maint show bfd-sharing
18462 Control whether @code{bfd} objects can be shared. When sharing is
18463 enabled @value{GDBN} reuses already open @code{bfd} objects rather
18464 than reopening the same file. Turning sharing off does not cause
18465 already shared @code{bfd} objects to be unshared, but all future files
18466 that are opened will create a new @code{bfd} object. Similarly,
18467 re-enabling sharing does not cause multiple existing @code{bfd}
18468 objects to be collapsed into a single shared @code{bfd} object.
18470 @kindex set debug bfd-cache @var{level}
18471 @kindex bfd caching
18472 @item set debug bfd-cache @var{level}
18473 Turns on debugging of the bfd cache, setting the level to @var{level}.
18475 @kindex show debug bfd-cache
18476 @kindex bfd caching
18477 @item show debug bfd-cache
18478 Show the current debugging level of the bfd cache.
18481 @node Separate Debug Files
18482 @section Debugging Information in Separate Files
18483 @cindex separate debugging information files
18484 @cindex debugging information in separate files
18485 @cindex @file{.debug} subdirectories
18486 @cindex debugging information directory, global
18487 @cindex global debugging information directories
18488 @cindex build ID, and separate debugging files
18489 @cindex @file{.build-id} directory
18491 @value{GDBN} allows you to put a program's debugging information in a
18492 file separate from the executable itself, in a way that allows
18493 @value{GDBN} to find and load the debugging information automatically.
18494 Since debugging information can be very large---sometimes larger
18495 than the executable code itself---some systems distribute debugging
18496 information for their executables in separate files, which users can
18497 install only when they need to debug a problem.
18499 @value{GDBN} supports two ways of specifying the separate debug info
18504 The executable contains a @dfn{debug link} that specifies the name of
18505 the separate debug info file. The separate debug file's name is
18506 usually @file{@var{executable}.debug}, where @var{executable} is the
18507 name of the corresponding executable file without leading directories
18508 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
18509 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
18510 checksum for the debug file, which @value{GDBN} uses to validate that
18511 the executable and the debug file came from the same build.
18514 The executable contains a @dfn{build ID}, a unique bit string that is
18515 also present in the corresponding debug info file. (This is supported
18516 only on some operating systems, when using the ELF or PE file formats
18517 for binary files and the @sc{gnu} Binutils.) For more details about
18518 this feature, see the description of the @option{--build-id}
18519 command-line option in @ref{Options, , Command Line Options, ld.info,
18520 The GNU Linker}. The debug info file's name is not specified
18521 explicitly by the build ID, but can be computed from the build ID, see
18525 Depending on the way the debug info file is specified, @value{GDBN}
18526 uses two different methods of looking for the debug file:
18530 For the ``debug link'' method, @value{GDBN} looks up the named file in
18531 the directory of the executable file, then in a subdirectory of that
18532 directory named @file{.debug}, and finally under each one of the global debug
18533 directories, in a subdirectory whose name is identical to the leading
18534 directories of the executable's absolute file name.
18537 For the ``build ID'' method, @value{GDBN} looks in the
18538 @file{.build-id} subdirectory of each one of the global debug directories for
18539 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
18540 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
18541 are the rest of the bit string. (Real build ID strings are 32 or more
18542 hex characters, not 10.)
18545 So, for example, suppose you ask @value{GDBN} to debug
18546 @file{/usr/bin/ls}, which has a debug link that specifies the
18547 file @file{ls.debug}, and a build ID whose value in hex is
18548 @code{abcdef1234}. If the list of the global debug directories includes
18549 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
18550 debug information files, in the indicated order:
18554 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
18556 @file{/usr/bin/ls.debug}
18558 @file{/usr/bin/.debug/ls.debug}
18560 @file{/usr/lib/debug/usr/bin/ls.debug}.
18563 @anchor{debug-file-directory}
18564 Global debugging info directories default to what is set by @value{GDBN}
18565 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
18566 you can also set the global debugging info directories, and view the list
18567 @value{GDBN} is currently using.
18571 @kindex set debug-file-directory
18572 @item set debug-file-directory @var{directories}
18573 Set the directories which @value{GDBN} searches for separate debugging
18574 information files to @var{directory}. Multiple path components can be set
18575 concatenating them by a path separator.
18577 @kindex show debug-file-directory
18578 @item show debug-file-directory
18579 Show the directories @value{GDBN} searches for separate debugging
18584 @cindex @code{.gnu_debuglink} sections
18585 @cindex debug link sections
18586 A debug link is a special section of the executable file named
18587 @code{.gnu_debuglink}. The section must contain:
18591 A filename, with any leading directory components removed, followed by
18594 zero to three bytes of padding, as needed to reach the next four-byte
18595 boundary within the section, and
18597 a four-byte CRC checksum, stored in the same endianness used for the
18598 executable file itself. The checksum is computed on the debugging
18599 information file's full contents by the function given below, passing
18600 zero as the @var{crc} argument.
18603 Any executable file format can carry a debug link, as long as it can
18604 contain a section named @code{.gnu_debuglink} with the contents
18607 @cindex @code{.note.gnu.build-id} sections
18608 @cindex build ID sections
18609 The build ID is a special section in the executable file (and in other
18610 ELF binary files that @value{GDBN} may consider). This section is
18611 often named @code{.note.gnu.build-id}, but that name is not mandatory.
18612 It contains unique identification for the built files---the ID remains
18613 the same across multiple builds of the same build tree. The default
18614 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
18615 content for the build ID string. The same section with an identical
18616 value is present in the original built binary with symbols, in its
18617 stripped variant, and in the separate debugging information file.
18619 The debugging information file itself should be an ordinary
18620 executable, containing a full set of linker symbols, sections, and
18621 debugging information. The sections of the debugging information file
18622 should have the same names, addresses, and sizes as the original file,
18623 but they need not contain any data---much like a @code{.bss} section
18624 in an ordinary executable.
18626 The @sc{gnu} binary utilities (Binutils) package includes the
18627 @samp{objcopy} utility that can produce
18628 the separated executable / debugging information file pairs using the
18629 following commands:
18632 @kbd{objcopy --only-keep-debug foo foo.debug}
18637 These commands remove the debugging
18638 information from the executable file @file{foo} and place it in the file
18639 @file{foo.debug}. You can use the first, second or both methods to link the
18644 The debug link method needs the following additional command to also leave
18645 behind a debug link in @file{foo}:
18648 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
18651 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
18652 a version of the @code{strip} command such that the command @kbd{strip foo -f
18653 foo.debug} has the same functionality as the two @code{objcopy} commands and
18654 the @code{ln -s} command above, together.
18657 Build ID gets embedded into the main executable using @code{ld --build-id} or
18658 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
18659 compatibility fixes for debug files separation are present in @sc{gnu} binary
18660 utilities (Binutils) package since version 2.18.
18665 @cindex CRC algorithm definition
18666 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
18667 IEEE 802.3 using the polynomial:
18669 @c TexInfo requires naked braces for multi-digit exponents for Tex
18670 @c output, but this causes HTML output to barf. HTML has to be set using
18671 @c raw commands. So we end up having to specify this equation in 2
18676 <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>
18677 + <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
18683 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
18684 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
18688 The function is computed byte at a time, taking the least
18689 significant bit of each byte first. The initial pattern
18690 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
18691 the final result is inverted to ensure trailing zeros also affect the
18694 @emph{Note:} This is the same CRC polynomial as used in handling the
18695 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{qCRC packet}).
18696 However in the case of the Remote Serial Protocol, the CRC is computed
18697 @emph{most} significant bit first, and the result is not inverted, so
18698 trailing zeros have no effect on the CRC value.
18700 To complete the description, we show below the code of the function
18701 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
18702 initially supplied @code{crc} argument means that an initial call to
18703 this function passing in zero will start computing the CRC using
18706 @kindex gnu_debuglink_crc32
18709 gnu_debuglink_crc32 (unsigned long crc,
18710 unsigned char *buf, size_t len)
18712 static const unsigned long crc32_table[256] =
18714 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
18715 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
18716 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
18717 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
18718 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
18719 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
18720 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
18721 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
18722 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
18723 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
18724 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
18725 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
18726 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
18727 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
18728 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
18729 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
18730 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
18731 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
18732 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
18733 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
18734 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
18735 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
18736 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
18737 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
18738 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
18739 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
18740 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
18741 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
18742 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
18743 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
18744 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
18745 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
18746 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
18747 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
18748 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
18749 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
18750 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
18751 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
18752 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
18753 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
18754 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
18755 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
18756 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
18757 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
18758 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
18759 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
18760 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
18761 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
18762 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
18763 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
18764 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
18767 unsigned char *end;
18769 crc = ~crc & 0xffffffff;
18770 for (end = buf + len; buf < end; ++buf)
18771 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
18772 return ~crc & 0xffffffff;
18777 This computation does not apply to the ``build ID'' method.
18779 @node MiniDebugInfo
18780 @section Debugging information in a special section
18781 @cindex separate debug sections
18782 @cindex @samp{.gnu_debugdata} section
18784 Some systems ship pre-built executables and libraries that have a
18785 special @samp{.gnu_debugdata} section. This feature is called
18786 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
18787 is used to supply extra symbols for backtraces.
18789 The intent of this section is to provide extra minimal debugging
18790 information for use in simple backtraces. It is not intended to be a
18791 replacement for full separate debugging information (@pxref{Separate
18792 Debug Files}). The example below shows the intended use; however,
18793 @value{GDBN} does not currently put restrictions on what sort of
18794 debugging information might be included in the section.
18796 @value{GDBN} has support for this extension. If the section exists,
18797 then it is used provided that no other source of debugging information
18798 can be found, and that @value{GDBN} was configured with LZMA support.
18800 This section can be easily created using @command{objcopy} and other
18801 standard utilities:
18804 # Extract the dynamic symbols from the main binary, there is no need
18805 # to also have these in the normal symbol table.
18806 nm -D @var{binary} --format=posix --defined-only \
18807 | awk '@{ print $1 @}' | sort > dynsyms
18809 # Extract all the text (i.e. function) symbols from the debuginfo.
18810 # (Note that we actually also accept "D" symbols, for the benefit
18811 # of platforms like PowerPC64 that use function descriptors.)
18812 nm @var{binary} --format=posix --defined-only \
18813 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
18816 # Keep all the function symbols not already in the dynamic symbol
18818 comm -13 dynsyms funcsyms > keep_symbols
18820 # Separate full debug info into debug binary.
18821 objcopy --only-keep-debug @var{binary} debug
18823 # Copy the full debuginfo, keeping only a minimal set of symbols and
18824 # removing some unnecessary sections.
18825 objcopy -S --remove-section .gdb_index --remove-section .comment \
18826 --keep-symbols=keep_symbols debug mini_debuginfo
18828 # Drop the full debug info from the original binary.
18829 strip --strip-all -R .comment @var{binary}
18831 # Inject the compressed data into the .gnu_debugdata section of the
18834 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
18838 @section Index Files Speed Up @value{GDBN}
18839 @cindex index files
18840 @cindex @samp{.gdb_index} section
18842 When @value{GDBN} finds a symbol file, it scans the symbols in the
18843 file in order to construct an internal symbol table. This lets most
18844 @value{GDBN} operations work quickly---at the cost of a delay early
18845 on. For large programs, this delay can be quite lengthy, so
18846 @value{GDBN} provides a way to build an index, which speeds up
18849 The index is stored as a section in the symbol file. @value{GDBN} can
18850 write the index to a file, then you can put it into the symbol file
18851 using @command{objcopy}.
18853 To create an index file, use the @code{save gdb-index} command:
18856 @item save gdb-index @var{directory}
18857 @kindex save gdb-index
18858 Create an index file for each symbol file currently known by
18859 @value{GDBN}. Each file is named after its corresponding symbol file,
18860 with @samp{.gdb-index} appended, and is written into the given
18864 Once you have created an index file you can merge it into your symbol
18865 file, here named @file{symfile}, using @command{objcopy}:
18868 $ objcopy --add-section .gdb_index=symfile.gdb-index \
18869 --set-section-flags .gdb_index=readonly symfile symfile
18872 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
18873 sections that have been deprecated. Usually they are deprecated because
18874 they are missing a new feature or have performance issues.
18875 To tell @value{GDBN} to use a deprecated index section anyway
18876 specify @code{set use-deprecated-index-sections on}.
18877 The default is @code{off}.
18878 This can speed up startup, but may result in some functionality being lost.
18879 @xref{Index Section Format}.
18881 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
18882 must be done before gdb reads the file. The following will not work:
18885 $ gdb -ex "set use-deprecated-index-sections on" <program>
18888 Instead you must do, for example,
18891 $ gdb -iex "set use-deprecated-index-sections on" <program>
18894 There are currently some limitation on indices. They only work when
18895 for DWARF debugging information, not stabs. And, they do not
18896 currently work for programs using Ada.
18898 @node Symbol Errors
18899 @section Errors Reading Symbol Files
18901 While reading a symbol file, @value{GDBN} occasionally encounters problems,
18902 such as symbol types it does not recognize, or known bugs in compiler
18903 output. By default, @value{GDBN} does not notify you of such problems, since
18904 they are relatively common and primarily of interest to people
18905 debugging compilers. If you are interested in seeing information
18906 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
18907 only one message about each such type of problem, no matter how many
18908 times the problem occurs; or you can ask @value{GDBN} to print more messages,
18909 to see how many times the problems occur, with the @code{set
18910 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
18913 The messages currently printed, and their meanings, include:
18916 @item inner block not inside outer block in @var{symbol}
18918 The symbol information shows where symbol scopes begin and end
18919 (such as at the start of a function or a block of statements). This
18920 error indicates that an inner scope block is not fully contained
18921 in its outer scope blocks.
18923 @value{GDBN} circumvents the problem by treating the inner block as if it had
18924 the same scope as the outer block. In the error message, @var{symbol}
18925 may be shown as ``@code{(don't know)}'' if the outer block is not a
18928 @item block at @var{address} out of order
18930 The symbol information for symbol scope blocks should occur in
18931 order of increasing addresses. This error indicates that it does not
18934 @value{GDBN} does not circumvent this problem, and has trouble
18935 locating symbols in the source file whose symbols it is reading. (You
18936 can often determine what source file is affected by specifying
18937 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
18940 @item bad block start address patched
18942 The symbol information for a symbol scope block has a start address
18943 smaller than the address of the preceding source line. This is known
18944 to occur in the SunOS 4.1.1 (and earlier) C compiler.
18946 @value{GDBN} circumvents the problem by treating the symbol scope block as
18947 starting on the previous source line.
18949 @item bad string table offset in symbol @var{n}
18952 Symbol number @var{n} contains a pointer into the string table which is
18953 larger than the size of the string table.
18955 @value{GDBN} circumvents the problem by considering the symbol to have the
18956 name @code{foo}, which may cause other problems if many symbols end up
18959 @item unknown symbol type @code{0x@var{nn}}
18961 The symbol information contains new data types that @value{GDBN} does
18962 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
18963 uncomprehended information, in hexadecimal.
18965 @value{GDBN} circumvents the error by ignoring this symbol information.
18966 This usually allows you to debug your program, though certain symbols
18967 are not accessible. If you encounter such a problem and feel like
18968 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
18969 on @code{complain}, then go up to the function @code{read_dbx_symtab}
18970 and examine @code{*bufp} to see the symbol.
18972 @item stub type has NULL name
18974 @value{GDBN} could not find the full definition for a struct or class.
18976 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
18977 The symbol information for a C@t{++} member function is missing some
18978 information that recent versions of the compiler should have output for
18981 @item info mismatch between compiler and debugger
18983 @value{GDBN} could not parse a type specification output by the compiler.
18988 @section GDB Data Files
18990 @cindex prefix for data files
18991 @value{GDBN} will sometimes read an auxiliary data file. These files
18992 are kept in a directory known as the @dfn{data directory}.
18994 You can set the data directory's name, and view the name @value{GDBN}
18995 is currently using.
18998 @kindex set data-directory
18999 @item set data-directory @var{directory}
19000 Set the directory which @value{GDBN} searches for auxiliary data files
19001 to @var{directory}.
19003 @kindex show data-directory
19004 @item show data-directory
19005 Show the directory @value{GDBN} searches for auxiliary data files.
19008 @cindex default data directory
19009 @cindex @samp{--with-gdb-datadir}
19010 You can set the default data directory by using the configure-time
19011 @samp{--with-gdb-datadir} option. If the data directory is inside
19012 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
19013 @samp{--exec-prefix}), then the default data directory will be updated
19014 automatically if the installed @value{GDBN} is moved to a new
19017 The data directory may also be specified with the
19018 @code{--data-directory} command line option.
19019 @xref{Mode Options}.
19022 @chapter Specifying a Debugging Target
19024 @cindex debugging target
19025 A @dfn{target} is the execution environment occupied by your program.
19027 Often, @value{GDBN} runs in the same host environment as your program;
19028 in that case, the debugging target is specified as a side effect when
19029 you use the @code{file} or @code{core} commands. When you need more
19030 flexibility---for example, running @value{GDBN} on a physically separate
19031 host, or controlling a standalone system over a serial port or a
19032 realtime system over a TCP/IP connection---you can use the @code{target}
19033 command to specify one of the target types configured for @value{GDBN}
19034 (@pxref{Target Commands, ,Commands for Managing Targets}).
19036 @cindex target architecture
19037 It is possible to build @value{GDBN} for several different @dfn{target
19038 architectures}. When @value{GDBN} is built like that, you can choose
19039 one of the available architectures with the @kbd{set architecture}
19043 @kindex set architecture
19044 @kindex show architecture
19045 @item set architecture @var{arch}
19046 This command sets the current target architecture to @var{arch}. The
19047 value of @var{arch} can be @code{"auto"}, in addition to one of the
19048 supported architectures.
19050 @item show architecture
19051 Show the current target architecture.
19053 @item set processor
19055 @kindex set processor
19056 @kindex show processor
19057 These are alias commands for, respectively, @code{set architecture}
19058 and @code{show architecture}.
19062 * Active Targets:: Active targets
19063 * Target Commands:: Commands for managing targets
19064 * Byte Order:: Choosing target byte order
19067 @node Active Targets
19068 @section Active Targets
19070 @cindex stacking targets
19071 @cindex active targets
19072 @cindex multiple targets
19074 There are multiple classes of targets such as: processes, executable files or
19075 recording sessions. Core files belong to the process class, making core file
19076 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
19077 on multiple active targets, one in each class. This allows you to (for
19078 example) start a process and inspect its activity, while still having access to
19079 the executable file after the process finishes. Or if you start process
19080 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
19081 presented a virtual layer of the recording target, while the process target
19082 remains stopped at the chronologically last point of the process execution.
19084 Use the @code{core-file} and @code{exec-file} commands to select a new core
19085 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
19086 specify as a target a process that is already running, use the @code{attach}
19087 command (@pxref{Attach, ,Debugging an Already-running Process}).
19089 @node Target Commands
19090 @section Commands for Managing Targets
19093 @item target @var{type} @var{parameters}
19094 Connects the @value{GDBN} host environment to a target machine or
19095 process. A target is typically a protocol for talking to debugging
19096 facilities. You use the argument @var{type} to specify the type or
19097 protocol of the target machine.
19099 Further @var{parameters} are interpreted by the target protocol, but
19100 typically include things like device names or host names to connect
19101 with, process numbers, and baud rates.
19103 The @code{target} command does not repeat if you press @key{RET} again
19104 after executing the command.
19106 @kindex help target
19108 Displays the names of all targets available. To display targets
19109 currently selected, use either @code{info target} or @code{info files}
19110 (@pxref{Files, ,Commands to Specify Files}).
19112 @item help target @var{name}
19113 Describe a particular target, including any parameters necessary to
19116 @kindex set gnutarget
19117 @item set gnutarget @var{args}
19118 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
19119 knows whether it is reading an @dfn{executable},
19120 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
19121 with the @code{set gnutarget} command. Unlike most @code{target} commands,
19122 with @code{gnutarget} the @code{target} refers to a program, not a machine.
19125 @emph{Warning:} To specify a file format with @code{set gnutarget},
19126 you must know the actual BFD name.
19130 @xref{Files, , Commands to Specify Files}.
19132 @kindex show gnutarget
19133 @item show gnutarget
19134 Use the @code{show gnutarget} command to display what file format
19135 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
19136 @value{GDBN} will determine the file format for each file automatically,
19137 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
19140 @cindex common targets
19141 Here are some common targets (available, or not, depending on the GDB
19146 @item target exec @var{program}
19147 @cindex executable file target
19148 An executable file. @samp{target exec @var{program}} is the same as
19149 @samp{exec-file @var{program}}.
19151 @item target core @var{filename}
19152 @cindex core dump file target
19153 A core dump file. @samp{target core @var{filename}} is the same as
19154 @samp{core-file @var{filename}}.
19156 @item target remote @var{medium}
19157 @cindex remote target
19158 A remote system connected to @value{GDBN} via a serial line or network
19159 connection. This command tells @value{GDBN} to use its own remote
19160 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
19162 For example, if you have a board connected to @file{/dev/ttya} on the
19163 machine running @value{GDBN}, you could say:
19166 target remote /dev/ttya
19169 @code{target remote} supports the @code{load} command. This is only
19170 useful if you have some other way of getting the stub to the target
19171 system, and you can put it somewhere in memory where it won't get
19172 clobbered by the download.
19174 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19175 @cindex built-in simulator target
19176 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
19184 works; however, you cannot assume that a specific memory map, device
19185 drivers, or even basic I/O is available, although some simulators do
19186 provide these. For info about any processor-specific simulator details,
19187 see the appropriate section in @ref{Embedded Processors, ,Embedded
19190 @item target native
19191 @cindex native target
19192 Setup for local/native process debugging. Useful to make the
19193 @code{run} command spawn native processes (likewise @code{attach},
19194 etc.@:) even when @code{set auto-connect-native-target} is @code{off}
19195 (@pxref{set auto-connect-native-target}).
19199 Different targets are available on different configurations of @value{GDBN};
19200 your configuration may have more or fewer targets.
19202 Many remote targets require you to download the executable's code once
19203 you've successfully established a connection. You may wish to control
19204 various aspects of this process.
19209 @kindex set hash@r{, for remote monitors}
19210 @cindex hash mark while downloading
19211 This command controls whether a hash mark @samp{#} is displayed while
19212 downloading a file to the remote monitor. If on, a hash mark is
19213 displayed after each S-record is successfully downloaded to the
19217 @kindex show hash@r{, for remote monitors}
19218 Show the current status of displaying the hash mark.
19220 @item set debug monitor
19221 @kindex set debug monitor
19222 @cindex display remote monitor communications
19223 Enable or disable display of communications messages between
19224 @value{GDBN} and the remote monitor.
19226 @item show debug monitor
19227 @kindex show debug monitor
19228 Show the current status of displaying communications between
19229 @value{GDBN} and the remote monitor.
19234 @kindex load @var{filename}
19235 @item load @var{filename}
19237 Depending on what remote debugging facilities are configured into
19238 @value{GDBN}, the @code{load} command may be available. Where it exists, it
19239 is meant to make @var{filename} (an executable) available for debugging
19240 on the remote system---by downloading, or dynamic linking, for example.
19241 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
19242 the @code{add-symbol-file} command.
19244 If your @value{GDBN} does not have a @code{load} command, attempting to
19245 execute it gets the error message ``@code{You can't do that when your
19246 target is @dots{}}''
19248 The file is loaded at whatever address is specified in the executable.
19249 For some object file formats, you can specify the load address when you
19250 link the program; for other formats, like a.out, the object file format
19251 specifies a fixed address.
19252 @c FIXME! This would be a good place for an xref to the GNU linker doc.
19254 Depending on the remote side capabilities, @value{GDBN} may be able to
19255 load programs into flash memory.
19257 @code{load} does not repeat if you press @key{RET} again after using it.
19261 @section Choosing Target Byte Order
19263 @cindex choosing target byte order
19264 @cindex target byte order
19266 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
19267 offer the ability to run either big-endian or little-endian byte
19268 orders. Usually the executable or symbol will include a bit to
19269 designate the endian-ness, and you will not need to worry about
19270 which to use. However, you may still find it useful to adjust
19271 @value{GDBN}'s idea of processor endian-ness manually.
19275 @item set endian big
19276 Instruct @value{GDBN} to assume the target is big-endian.
19278 @item set endian little
19279 Instruct @value{GDBN} to assume the target is little-endian.
19281 @item set endian auto
19282 Instruct @value{GDBN} to use the byte order associated with the
19286 Display @value{GDBN}'s current idea of the target byte order.
19290 Note that these commands merely adjust interpretation of symbolic
19291 data on the host, and that they have absolutely no effect on the
19295 @node Remote Debugging
19296 @chapter Debugging Remote Programs
19297 @cindex remote debugging
19299 If you are trying to debug a program running on a machine that cannot run
19300 @value{GDBN} in the usual way, it is often useful to use remote debugging.
19301 For example, you might use remote debugging on an operating system kernel,
19302 or on a small system which does not have a general purpose operating system
19303 powerful enough to run a full-featured debugger.
19305 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
19306 to make this work with particular debugging targets. In addition,
19307 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
19308 but not specific to any particular target system) which you can use if you
19309 write the remote stubs---the code that runs on the remote system to
19310 communicate with @value{GDBN}.
19312 Other remote targets may be available in your
19313 configuration of @value{GDBN}; use @code{help target} to list them.
19316 * Connecting:: Connecting to a remote target
19317 * File Transfer:: Sending files to a remote system
19318 * Server:: Using the gdbserver program
19319 * Remote Configuration:: Remote configuration
19320 * Remote Stub:: Implementing a remote stub
19324 @section Connecting to a Remote Target
19325 @cindex remote debugging, connecting
19326 @cindex @code{gdbserver}, connecting
19327 @cindex remote debugging, types of connections
19328 @cindex @code{gdbserver}, types of connections
19329 @cindex @code{gdbserver}, @code{target remote} mode
19330 @cindex @code{gdbserver}, @code{target extended-remote} mode
19332 This section describes how to connect to a remote target, including the
19333 types of connections and their differences, how to set up executable and
19334 symbol files on the host and target, and the commands used for
19335 connecting to and disconnecting from the remote target.
19337 @subsection Types of Remote Connections
19339 @value{GDBN} supports two types of remote connections, @code{target remote}
19340 mode and @code{target extended-remote} mode. Note that many remote targets
19341 support only @code{target remote} mode. There are several major
19342 differences between the two types of connections, enumerated here:
19346 @cindex remote debugging, detach and program exit
19347 @item Result of detach or program exit
19348 @strong{With target remote mode:} When the debugged program exits or you
19349 detach from it, @value{GDBN} disconnects from the target. When using
19350 @code{gdbserver}, @code{gdbserver} will exit.
19352 @strong{With target extended-remote mode:} When the debugged program exits or
19353 you detach from it, @value{GDBN} remains connected to the target, even
19354 though no program is running. You can rerun the program, attach to a
19355 running program, or use @code{monitor} commands specific to the target.
19357 When using @code{gdbserver} in this case, it does not exit unless it was
19358 invoked using the @option{--once} option. If the @option{--once} option
19359 was not used, you can ask @code{gdbserver} to exit using the
19360 @code{monitor exit} command (@pxref{Monitor Commands for gdbserver}).
19362 @item Specifying the program to debug
19363 For both connection types you use the @code{file} command to specify the
19364 program on the host system. If you are using @code{gdbserver} there are
19365 some differences in how to specify the location of the program on the
19368 @strong{With target remote mode:} You must either specify the program to debug
19369 on the @code{gdbserver} command line or use the @option{--attach} option
19370 (@pxref{Attaching to a program,,Attaching to a Running Program}).
19372 @cindex @option{--multi}, @code{gdbserver} option
19373 @strong{With target extended-remote mode:} You may specify the program to debug
19374 on the @code{gdbserver} command line, or you can load the program or attach
19375 to it using @value{GDBN} commands after connecting to @code{gdbserver}.
19377 @anchor{--multi Option in Types of Remote Connnections}
19378 You can start @code{gdbserver} without supplying an initial command to run
19379 or process ID to attach. To do this, use the @option{--multi} command line
19380 option. Then you can connect using @code{target extended-remote} and start
19381 the program you want to debug (see below for details on using the
19382 @code{run} command in this scenario). Note that the conditions under which
19383 @code{gdbserver} terminates depend on how @value{GDBN} connects to it
19384 (@code{target remote} or @code{target extended-remote}). The
19385 @option{--multi} option to @code{gdbserver} has no influence on that.
19387 @item The @code{run} command
19388 @strong{With target remote mode:} The @code{run} command is not
19389 supported. Once a connection has been established, you can use all
19390 the usual @value{GDBN} commands to examine and change data. The
19391 remote program is already running, so you can use commands like
19392 @kbd{step} and @kbd{continue}.
19394 @strong{With target extended-remote mode:} The @code{run} command is
19395 supported. The @code{run} command uses the value set by
19396 @code{set remote exec-file} (@pxref{set remote exec-file}) to select
19397 the program to run. Command line arguments are supported, except for
19398 wildcard expansion and I/O redirection (@pxref{Arguments}).
19400 If you specify the program to debug on the command line, then the
19401 @code{run} command is not required to start execution, and you can
19402 resume using commands like @kbd{step} and @kbd{continue} as with
19403 @code{target remote} mode.
19405 @anchor{Attaching in Types of Remote Connections}
19407 @strong{With target remote mode:} The @value{GDBN} command @code{attach} is
19408 not supported. To attach to a running program using @code{gdbserver}, you
19409 must use the @option{--attach} option (@pxref{Running gdbserver}).
19411 @strong{With target extended-remote mode:} To attach to a running program,
19412 you may use the @code{attach} command after the connection has been
19413 established. If you are using @code{gdbserver}, you may also invoke
19414 @code{gdbserver} using the @option{--attach} option
19415 (@pxref{Running gdbserver}).
19419 @anchor{Host and target files}
19420 @subsection Host and Target Files
19421 @cindex remote debugging, symbol files
19422 @cindex symbol files, remote debugging
19424 @value{GDBN}, running on the host, needs access to symbol and debugging
19425 information for your program running on the target. This requires
19426 access to an unstripped copy of your program, and possibly any associated
19427 symbol files. Note that this section applies equally to both @code{target
19428 remote} mode and @code{target extended-remote} mode.
19430 Some remote targets (@pxref{qXfer executable filename read}, and
19431 @pxref{Host I/O Packets}) allow @value{GDBN} to access program files over
19432 the same connection used to communicate with @value{GDBN}. With such a
19433 target, if the remote program is unstripped, the only command you need is
19434 @code{target remote} (or @code{target extended-remote}).
19436 If the remote program is stripped, or the target does not support remote
19437 program file access, start up @value{GDBN} using the name of the local
19438 unstripped copy of your program as the first argument, or use the
19439 @code{file} command. Use @code{set sysroot} to specify the location (on
19440 the host) of target libraries (unless your @value{GDBN} was compiled with
19441 the correct sysroot using @code{--with-sysroot}). Alternatively, you
19442 may use @code{set solib-search-path} to specify how @value{GDBN} locates
19445 The symbol file and target libraries must exactly match the executable
19446 and libraries on the target, with one exception: the files on the host
19447 system should not be stripped, even if the files on the target system
19448 are. Mismatched or missing files will lead to confusing results
19449 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
19450 files may also prevent @code{gdbserver} from debugging multi-threaded
19453 @subsection Remote Connection Commands
19454 @cindex remote connection commands
19455 @value{GDBN} can communicate with the target over a serial line, or
19456 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
19457 each case, @value{GDBN} uses the same protocol for debugging your
19458 program; only the medium carrying the debugging packets varies. The
19459 @code{target remote} and @code{target extended-remote} commands
19460 establish a connection to the target. Both commands accept the same
19461 arguments, which indicate the medium to use:
19465 @item target remote @var{serial-device}
19466 @itemx target extended-remote @var{serial-device}
19467 @cindex serial line, @code{target remote}
19468 Use @var{serial-device} to communicate with the target. For example,
19469 to use a serial line connected to the device named @file{/dev/ttyb}:
19472 target remote /dev/ttyb
19475 If you're using a serial line, you may want to give @value{GDBN} the
19476 @samp{--baud} option, or use the @code{set serial baud} command
19477 (@pxref{Remote Configuration, set serial baud}) before the
19478 @code{target} command.
19480 @item target remote @code{@var{host}:@var{port}}
19481 @itemx target remote @code{tcp:@var{host}:@var{port}}
19482 @itemx target extended-remote @code{@var{host}:@var{port}}
19483 @itemx target extended-remote @code{tcp:@var{host}:@var{port}}
19484 @cindex @acronym{TCP} port, @code{target remote}
19485 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
19486 The @var{host} may be either a host name or a numeric @acronym{IP}
19487 address; @var{port} must be a decimal number. The @var{host} could be
19488 the target machine itself, if it is directly connected to the net, or
19489 it might be a terminal server which in turn has a serial line to the
19492 For example, to connect to port 2828 on a terminal server named
19496 target remote manyfarms:2828
19499 If your remote target is actually running on the same machine as your
19500 debugger session (e.g.@: a simulator for your target running on the
19501 same host), you can omit the hostname. For example, to connect to
19502 port 1234 on your local machine:
19505 target remote :1234
19509 Note that the colon is still required here.
19511 @item target remote @code{udp:@var{host}:@var{port}}
19512 @itemx target extended-remote @code{udp:@var{host}:@var{port}}
19513 @cindex @acronym{UDP} port, @code{target remote}
19514 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
19515 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
19518 target remote udp:manyfarms:2828
19521 When using a @acronym{UDP} connection for remote debugging, you should
19522 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
19523 can silently drop packets on busy or unreliable networks, which will
19524 cause havoc with your debugging session.
19526 @item target remote | @var{command}
19527 @itemx target extended-remote | @var{command}
19528 @cindex pipe, @code{target remote} to
19529 Run @var{command} in the background and communicate with it using a
19530 pipe. The @var{command} is a shell command, to be parsed and expanded
19531 by the system's command shell, @code{/bin/sh}; it should expect remote
19532 protocol packets on its standard input, and send replies on its
19533 standard output. You could use this to run a stand-alone simulator
19534 that speaks the remote debugging protocol, to make net connections
19535 using programs like @code{ssh}, or for other similar tricks.
19537 If @var{command} closes its standard output (perhaps by exiting),
19538 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
19539 program has already exited, this will have no effect.)
19543 @cindex interrupting remote programs
19544 @cindex remote programs, interrupting
19545 Whenever @value{GDBN} is waiting for the remote program, if you type the
19546 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
19547 program. This may or may not succeed, depending in part on the hardware
19548 and the serial drivers the remote system uses. If you type the
19549 interrupt character once again, @value{GDBN} displays this prompt:
19552 Interrupted while waiting for the program.
19553 Give up (and stop debugging it)? (y or n)
19556 In @code{target remote} mode, if you type @kbd{y}, @value{GDBN} abandons
19557 the remote debugging session. (If you decide you want to try again later,
19558 you can use @kbd{target remote} again to connect once more.) If you type
19559 @kbd{n}, @value{GDBN} goes back to waiting.
19561 In @code{target extended-remote} mode, typing @kbd{n} will leave
19562 @value{GDBN} connected to the target.
19565 @kindex detach (remote)
19567 When you have finished debugging the remote program, you can use the
19568 @code{detach} command to release it from @value{GDBN} control.
19569 Detaching from the target normally resumes its execution, but the results
19570 will depend on your particular remote stub. After the @code{detach}
19571 command in @code{target remote} mode, @value{GDBN} is free to connect to
19572 another target. In @code{target extended-remote} mode, @value{GDBN} is
19573 still connected to the target.
19577 The @code{disconnect} command closes the connection to the target, and
19578 the target is generally not resumed. It will wait for @value{GDBN}
19579 (this instance or another one) to connect and continue debugging. After
19580 the @code{disconnect} command, @value{GDBN} is again free to connect to
19583 @cindex send command to remote monitor
19584 @cindex extend @value{GDBN} for remote targets
19585 @cindex add new commands for external monitor
19587 @item monitor @var{cmd}
19588 This command allows you to send arbitrary commands directly to the
19589 remote monitor. Since @value{GDBN} doesn't care about the commands it
19590 sends like this, this command is the way to extend @value{GDBN}---you
19591 can add new commands that only the external monitor will understand
19595 @node File Transfer
19596 @section Sending files to a remote system
19597 @cindex remote target, file transfer
19598 @cindex file transfer
19599 @cindex sending files to remote systems
19601 Some remote targets offer the ability to transfer files over the same
19602 connection used to communicate with @value{GDBN}. This is convenient
19603 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
19604 running @code{gdbserver} over a network interface. For other targets,
19605 e.g.@: embedded devices with only a single serial port, this may be
19606 the only way to upload or download files.
19608 Not all remote targets support these commands.
19612 @item remote put @var{hostfile} @var{targetfile}
19613 Copy file @var{hostfile} from the host system (the machine running
19614 @value{GDBN}) to @var{targetfile} on the target system.
19617 @item remote get @var{targetfile} @var{hostfile}
19618 Copy file @var{targetfile} from the target system to @var{hostfile}
19619 on the host system.
19621 @kindex remote delete
19622 @item remote delete @var{targetfile}
19623 Delete @var{targetfile} from the target system.
19628 @section Using the @code{gdbserver} Program
19631 @cindex remote connection without stubs
19632 @code{gdbserver} is a control program for Unix-like systems, which
19633 allows you to connect your program with a remote @value{GDBN} via
19634 @code{target remote} or @code{target extended-remote}---but without
19635 linking in the usual debugging stub.
19637 @code{gdbserver} is not a complete replacement for the debugging stubs,
19638 because it requires essentially the same operating-system facilities
19639 that @value{GDBN} itself does. In fact, a system that can run
19640 @code{gdbserver} to connect to a remote @value{GDBN} could also run
19641 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
19642 because it is a much smaller program than @value{GDBN} itself. It is
19643 also easier to port than all of @value{GDBN}, so you may be able to get
19644 started more quickly on a new system by using @code{gdbserver}.
19645 Finally, if you develop code for real-time systems, you may find that
19646 the tradeoffs involved in real-time operation make it more convenient to
19647 do as much development work as possible on another system, for example
19648 by cross-compiling. You can use @code{gdbserver} to make a similar
19649 choice for debugging.
19651 @value{GDBN} and @code{gdbserver} communicate via either a serial line
19652 or a TCP connection, using the standard @value{GDBN} remote serial
19656 @emph{Warning:} @code{gdbserver} does not have any built-in security.
19657 Do not run @code{gdbserver} connected to any public network; a
19658 @value{GDBN} connection to @code{gdbserver} provides access to the
19659 target system with the same privileges as the user running
19663 @anchor{Running gdbserver}
19664 @subsection Running @code{gdbserver}
19665 @cindex arguments, to @code{gdbserver}
19666 @cindex @code{gdbserver}, command-line arguments
19668 Run @code{gdbserver} on the target system. You need a copy of the
19669 program you want to debug, including any libraries it requires.
19670 @code{gdbserver} does not need your program's symbol table, so you can
19671 strip the program if necessary to save space. @value{GDBN} on the host
19672 system does all the symbol handling.
19674 To use the server, you must tell it how to communicate with @value{GDBN};
19675 the name of your program; and the arguments for your program. The usual
19679 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
19682 @var{comm} is either a device name (to use a serial line), or a TCP
19683 hostname and portnumber, or @code{-} or @code{stdio} to use
19684 stdin/stdout of @code{gdbserver}.
19685 For example, to debug Emacs with the argument
19686 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
19690 target> gdbserver /dev/com1 emacs foo.txt
19693 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
19696 To use a TCP connection instead of a serial line:
19699 target> gdbserver host:2345 emacs foo.txt
19702 The only difference from the previous example is the first argument,
19703 specifying that you are communicating with the host @value{GDBN} via
19704 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
19705 expect a TCP connection from machine @samp{host} to local TCP port 2345.
19706 (Currently, the @samp{host} part is ignored.) You can choose any number
19707 you want for the port number as long as it does not conflict with any
19708 TCP ports already in use on the target system (for example, @code{23} is
19709 reserved for @code{telnet}).@footnote{If you choose a port number that
19710 conflicts with another service, @code{gdbserver} prints an error message
19711 and exits.} You must use the same port number with the host @value{GDBN}
19712 @code{target remote} command.
19714 The @code{stdio} connection is useful when starting @code{gdbserver}
19718 (gdb) target remote | ssh -T hostname gdbserver - hello
19721 The @samp{-T} option to ssh is provided because we don't need a remote pty,
19722 and we don't want escape-character handling. Ssh does this by default when
19723 a command is provided, the flag is provided to make it explicit.
19724 You could elide it if you want to.
19726 Programs started with stdio-connected gdbserver have @file{/dev/null} for
19727 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
19728 display through a pipe connected to gdbserver.
19729 Both @code{stdout} and @code{stderr} use the same pipe.
19731 @anchor{Attaching to a program}
19732 @subsubsection Attaching to a Running Program
19733 @cindex attach to a program, @code{gdbserver}
19734 @cindex @option{--attach}, @code{gdbserver} option
19736 On some targets, @code{gdbserver} can also attach to running programs.
19737 This is accomplished via the @code{--attach} argument. The syntax is:
19740 target> gdbserver --attach @var{comm} @var{pid}
19743 @var{pid} is the process ID of a currently running process. It isn't
19744 necessary to point @code{gdbserver} at a binary for the running process.
19746 In @code{target extended-remote} mode, you can also attach using the
19747 @value{GDBN} attach command
19748 (@pxref{Attaching in Types of Remote Connections}).
19751 You can debug processes by name instead of process ID if your target has the
19752 @code{pidof} utility:
19755 target> gdbserver --attach @var{comm} `pidof @var{program}`
19758 In case more than one copy of @var{program} is running, or @var{program}
19759 has multiple threads, most versions of @code{pidof} support the
19760 @code{-s} option to only return the first process ID.
19762 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
19764 This section applies only when @code{gdbserver} is run to listen on a TCP
19767 @code{gdbserver} normally terminates after all of its debugged processes have
19768 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
19769 extended-remote}, @code{gdbserver} stays running even with no processes left.
19770 @value{GDBN} normally terminates the spawned debugged process on its exit,
19771 which normally also terminates @code{gdbserver} in the @kbd{target remote}
19772 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
19773 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
19774 stays running even in the @kbd{target remote} mode.
19776 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
19777 Such reconnecting is useful for features like @ref{disconnected tracing}. For
19778 completeness, at most one @value{GDBN} can be connected at a time.
19780 @cindex @option{--once}, @code{gdbserver} option
19781 By default, @code{gdbserver} keeps the listening TCP port open, so that
19782 subsequent connections are possible. However, if you start @code{gdbserver}
19783 with the @option{--once} option, it will stop listening for any further
19784 connection attempts after connecting to the first @value{GDBN} session. This
19785 means no further connections to @code{gdbserver} will be possible after the
19786 first one. It also means @code{gdbserver} will terminate after the first
19787 connection with remote @value{GDBN} has closed, even for unexpectedly closed
19788 connections and even in the @kbd{target extended-remote} mode. The
19789 @option{--once} option allows reusing the same port number for connecting to
19790 multiple instances of @code{gdbserver} running on the same host, since each
19791 instance closes its port after the first connection.
19793 @anchor{Other Command-Line Arguments for gdbserver}
19794 @subsubsection Other Command-Line Arguments for @code{gdbserver}
19796 You can use the @option{--multi} option to start @code{gdbserver} without
19797 specifying a program to debug or a process to attach to. Then you can
19798 attach in @code{target extended-remote} mode and run or attach to a
19799 program. For more information,
19800 @pxref{--multi Option in Types of Remote Connnections}.
19802 @cindex @option{--debug}, @code{gdbserver} option
19803 The @option{--debug} option tells @code{gdbserver} to display extra
19804 status information about the debugging process.
19805 @cindex @option{--remote-debug}, @code{gdbserver} option
19806 The @option{--remote-debug} option tells @code{gdbserver} to display
19807 remote protocol debug output. These options are intended for
19808 @code{gdbserver} development and for bug reports to the developers.
19810 @cindex @option{--debug-format}, @code{gdbserver} option
19811 The @option{--debug-format=option1[,option2,...]} option tells
19812 @code{gdbserver} to include additional information in each output.
19813 Possible options are:
19817 Turn off all extra information in debugging output.
19819 Turn on all extra information in debugging output.
19821 Include a timestamp in each line of debugging output.
19824 Options are processed in order. Thus, for example, if @option{none}
19825 appears last then no additional information is added to debugging output.
19827 @cindex @option{--wrapper}, @code{gdbserver} option
19828 The @option{--wrapper} option specifies a wrapper to launch programs
19829 for debugging. The option should be followed by the name of the
19830 wrapper, then any command-line arguments to pass to the wrapper, then
19831 @kbd{--} indicating the end of the wrapper arguments.
19833 @code{gdbserver} runs the specified wrapper program with a combined
19834 command line including the wrapper arguments, then the name of the
19835 program to debug, then any arguments to the program. The wrapper
19836 runs until it executes your program, and then @value{GDBN} gains control.
19838 You can use any program that eventually calls @code{execve} with
19839 its arguments as a wrapper. Several standard Unix utilities do
19840 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
19841 with @code{exec "$@@"} will also work.
19843 For example, you can use @code{env} to pass an environment variable to
19844 the debugged program, without setting the variable in @code{gdbserver}'s
19848 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
19851 @subsection Connecting to @code{gdbserver}
19853 The basic procedure for connecting to the remote target is:
19857 Run @value{GDBN} on the host system.
19860 Make sure you have the necessary symbol files
19861 (@pxref{Host and target files}).
19862 Load symbols for your application using the @code{file} command before you
19863 connect. Use @code{set sysroot} to locate target libraries (unless your
19864 @value{GDBN} was compiled with the correct sysroot using
19865 @code{--with-sysroot}).
19868 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
19869 For TCP connections, you must start up @code{gdbserver} prior to using
19870 the @code{target} command. Otherwise you may get an error whose
19871 text depends on the host system, but which usually looks something like
19872 @samp{Connection refused}. Don't use the @code{load}
19873 command in @value{GDBN} when using @code{target remote} mode, since the
19874 program is already on the target.
19878 @anchor{Monitor Commands for gdbserver}
19879 @subsection Monitor Commands for @code{gdbserver}
19880 @cindex monitor commands, for @code{gdbserver}
19882 During a @value{GDBN} session using @code{gdbserver}, you can use the
19883 @code{monitor} command to send special requests to @code{gdbserver}.
19884 Here are the available commands.
19888 List the available monitor commands.
19890 @item monitor set debug 0
19891 @itemx monitor set debug 1
19892 Disable or enable general debugging messages.
19894 @item monitor set remote-debug 0
19895 @itemx monitor set remote-debug 1
19896 Disable or enable specific debugging messages associated with the remote
19897 protocol (@pxref{Remote Protocol}).
19899 @item monitor set debug-format option1@r{[},option2,...@r{]}
19900 Specify additional text to add to debugging messages.
19901 Possible options are:
19905 Turn off all extra information in debugging output.
19907 Turn on all extra information in debugging output.
19909 Include a timestamp in each line of debugging output.
19912 Options are processed in order. Thus, for example, if @option{none}
19913 appears last then no additional information is added to debugging output.
19915 @item monitor set libthread-db-search-path [PATH]
19916 @cindex gdbserver, search path for @code{libthread_db}
19917 When this command is issued, @var{path} is a colon-separated list of
19918 directories to search for @code{libthread_db} (@pxref{Threads,,set
19919 libthread-db-search-path}). If you omit @var{path},
19920 @samp{libthread-db-search-path} will be reset to its default value.
19922 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
19923 not supported in @code{gdbserver}.
19926 Tell gdbserver to exit immediately. This command should be followed by
19927 @code{disconnect} to close the debugging session. @code{gdbserver} will
19928 detach from any attached processes and kill any processes it created.
19929 Use @code{monitor exit} to terminate @code{gdbserver} at the end
19930 of a multi-process mode debug session.
19934 @subsection Tracepoints support in @code{gdbserver}
19935 @cindex tracepoints support in @code{gdbserver}
19937 On some targets, @code{gdbserver} supports tracepoints, fast
19938 tracepoints and static tracepoints.
19940 For fast or static tracepoints to work, a special library called the
19941 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
19942 This library is built and distributed as an integral part of
19943 @code{gdbserver}. In addition, support for static tracepoints
19944 requires building the in-process agent library with static tracepoints
19945 support. At present, the UST (LTTng Userspace Tracer,
19946 @url{http://lttng.org/ust}) tracing engine is supported. This support
19947 is automatically available if UST development headers are found in the
19948 standard include path when @code{gdbserver} is built, or if
19949 @code{gdbserver} was explicitly configured using @option{--with-ust}
19950 to point at such headers. You can explicitly disable the support
19951 using @option{--with-ust=no}.
19953 There are several ways to load the in-process agent in your program:
19956 @item Specifying it as dependency at link time
19958 You can link your program dynamically with the in-process agent
19959 library. On most systems, this is accomplished by adding
19960 @code{-linproctrace} to the link command.
19962 @item Using the system's preloading mechanisms
19964 You can force loading the in-process agent at startup time by using
19965 your system's support for preloading shared libraries. Many Unixes
19966 support the concept of preloading user defined libraries. In most
19967 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
19968 in the environment. See also the description of @code{gdbserver}'s
19969 @option{--wrapper} command line option.
19971 @item Using @value{GDBN} to force loading the agent at run time
19973 On some systems, you can force the inferior to load a shared library,
19974 by calling a dynamic loader function in the inferior that takes care
19975 of dynamically looking up and loading a shared library. On most Unix
19976 systems, the function is @code{dlopen}. You'll use the @code{call}
19977 command for that. For example:
19980 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
19983 Note that on most Unix systems, for the @code{dlopen} function to be
19984 available, the program needs to be linked with @code{-ldl}.
19987 On systems that have a userspace dynamic loader, like most Unix
19988 systems, when you connect to @code{gdbserver} using @code{target
19989 remote}, you'll find that the program is stopped at the dynamic
19990 loader's entry point, and no shared library has been loaded in the
19991 program's address space yet, including the in-process agent. In that
19992 case, before being able to use any of the fast or static tracepoints
19993 features, you need to let the loader run and load the shared
19994 libraries. The simplest way to do that is to run the program to the
19995 main procedure. E.g., if debugging a C or C@t{++} program, start
19996 @code{gdbserver} like so:
19999 $ gdbserver :9999 myprogram
20002 Start GDB and connect to @code{gdbserver} like so, and run to main:
20006 (@value{GDBP}) target remote myhost:9999
20007 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
20008 (@value{GDBP}) b main
20009 (@value{GDBP}) continue
20012 The in-process tracing agent library should now be loaded into the
20013 process; you can confirm it with the @code{info sharedlibrary}
20014 command, which will list @file{libinproctrace.so} as loaded in the
20015 process. You are now ready to install fast tracepoints, list static
20016 tracepoint markers, probe static tracepoints markers, and start
20019 @node Remote Configuration
20020 @section Remote Configuration
20023 @kindex show remote
20024 This section documents the configuration options available when
20025 debugging remote programs. For the options related to the File I/O
20026 extensions of the remote protocol, see @ref{system,
20027 system-call-allowed}.
20030 @item set remoteaddresssize @var{bits}
20031 @cindex address size for remote targets
20032 @cindex bits in remote address
20033 Set the maximum size of address in a memory packet to the specified
20034 number of bits. @value{GDBN} will mask off the address bits above
20035 that number, when it passes addresses to the remote target. The
20036 default value is the number of bits in the target's address.
20038 @item show remoteaddresssize
20039 Show the current value of remote address size in bits.
20041 @item set serial baud @var{n}
20042 @cindex baud rate for remote targets
20043 Set the baud rate for the remote serial I/O to @var{n} baud. The
20044 value is used to set the speed of the serial port used for debugging
20047 @item show serial baud
20048 Show the current speed of the remote connection.
20050 @item set serial parity @var{parity}
20051 Set the parity for the remote serial I/O. Supported values of @var{parity} are:
20052 @code{even}, @code{none}, and @code{odd}. The default is @code{none}.
20054 @item show serial parity
20055 Show the current parity of the serial port.
20057 @item set remotebreak
20058 @cindex interrupt remote programs
20059 @cindex BREAK signal instead of Ctrl-C
20060 @anchor{set remotebreak}
20061 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
20062 when you type @kbd{Ctrl-c} to interrupt the program running
20063 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
20064 character instead. The default is off, since most remote systems
20065 expect to see @samp{Ctrl-C} as the interrupt signal.
20067 @item show remotebreak
20068 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
20069 interrupt the remote program.
20071 @item set remoteflow on
20072 @itemx set remoteflow off
20073 @kindex set remoteflow
20074 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
20075 on the serial port used to communicate to the remote target.
20077 @item show remoteflow
20078 @kindex show remoteflow
20079 Show the current setting of hardware flow control.
20081 @item set remotelogbase @var{base}
20082 Set the base (a.k.a.@: radix) of logging serial protocol
20083 communications to @var{base}. Supported values of @var{base} are:
20084 @code{ascii}, @code{octal}, and @code{hex}. The default is
20087 @item show remotelogbase
20088 Show the current setting of the radix for logging remote serial
20091 @item set remotelogfile @var{file}
20092 @cindex record serial communications on file
20093 Record remote serial communications on the named @var{file}. The
20094 default is not to record at all.
20096 @item show remotelogfile.
20097 Show the current setting of the file name on which to record the
20098 serial communications.
20100 @item set remotetimeout @var{num}
20101 @cindex timeout for serial communications
20102 @cindex remote timeout
20103 Set the timeout limit to wait for the remote target to respond to
20104 @var{num} seconds. The default is 2 seconds.
20106 @item show remotetimeout
20107 Show the current number of seconds to wait for the remote target
20110 @cindex limit hardware breakpoints and watchpoints
20111 @cindex remote target, limit break- and watchpoints
20112 @anchor{set remote hardware-watchpoint-limit}
20113 @anchor{set remote hardware-breakpoint-limit}
20114 @item set remote hardware-watchpoint-limit @var{limit}
20115 @itemx set remote hardware-breakpoint-limit @var{limit}
20116 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
20117 watchpoints. A limit of -1, the default, is treated as unlimited.
20119 @cindex limit hardware watchpoints length
20120 @cindex remote target, limit watchpoints length
20121 @anchor{set remote hardware-watchpoint-length-limit}
20122 @item set remote hardware-watchpoint-length-limit @var{limit}
20123 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
20124 a remote hardware watchpoint. A limit of -1, the default, is treated
20127 @item show remote hardware-watchpoint-length-limit
20128 Show the current limit (in bytes) of the maximum length of
20129 a remote hardware watchpoint.
20131 @item set remote exec-file @var{filename}
20132 @itemx show remote exec-file
20133 @anchor{set remote exec-file}
20134 @cindex executable file, for remote target
20135 Select the file used for @code{run} with @code{target
20136 extended-remote}. This should be set to a filename valid on the
20137 target system. If it is not set, the target will use a default
20138 filename (e.g.@: the last program run).
20140 @item set remote interrupt-sequence
20141 @cindex interrupt remote programs
20142 @cindex select Ctrl-C, BREAK or BREAK-g
20143 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
20144 @samp{BREAK-g} as the
20145 sequence to the remote target in order to interrupt the execution.
20146 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
20147 is high level of serial line for some certain time.
20148 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
20149 It is @code{BREAK} signal followed by character @code{g}.
20151 @item show interrupt-sequence
20152 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
20153 is sent by @value{GDBN} to interrupt the remote program.
20154 @code{BREAK-g} is BREAK signal followed by @code{g} and
20155 also known as Magic SysRq g.
20157 @item set remote interrupt-on-connect
20158 @cindex send interrupt-sequence on start
20159 Specify whether interrupt-sequence is sent to remote target when
20160 @value{GDBN} connects to it. This is mostly needed when you debug
20161 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
20162 which is known as Magic SysRq g in order to connect @value{GDBN}.
20164 @item show interrupt-on-connect
20165 Show whether interrupt-sequence is sent
20166 to remote target when @value{GDBN} connects to it.
20170 @item set tcp auto-retry on
20171 @cindex auto-retry, for remote TCP target
20172 Enable auto-retry for remote TCP connections. This is useful if the remote
20173 debugging agent is launched in parallel with @value{GDBN}; there is a race
20174 condition because the agent may not become ready to accept the connection
20175 before @value{GDBN} attempts to connect. When auto-retry is
20176 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
20177 to establish the connection using the timeout specified by
20178 @code{set tcp connect-timeout}.
20180 @item set tcp auto-retry off
20181 Do not auto-retry failed TCP connections.
20183 @item show tcp auto-retry
20184 Show the current auto-retry setting.
20186 @item set tcp connect-timeout @var{seconds}
20187 @itemx set tcp connect-timeout unlimited
20188 @cindex connection timeout, for remote TCP target
20189 @cindex timeout, for remote target connection
20190 Set the timeout for establishing a TCP connection to the remote target to
20191 @var{seconds}. The timeout affects both polling to retry failed connections
20192 (enabled by @code{set tcp auto-retry on}) and waiting for connections
20193 that are merely slow to complete, and represents an approximate cumulative
20194 value. If @var{seconds} is @code{unlimited}, there is no timeout and
20195 @value{GDBN} will keep attempting to establish a connection forever,
20196 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
20198 @item show tcp connect-timeout
20199 Show the current connection timeout setting.
20202 @cindex remote packets, enabling and disabling
20203 The @value{GDBN} remote protocol autodetects the packets supported by
20204 your debugging stub. If you need to override the autodetection, you
20205 can use these commands to enable or disable individual packets. Each
20206 packet can be set to @samp{on} (the remote target supports this
20207 packet), @samp{off} (the remote target does not support this packet),
20208 or @samp{auto} (detect remote target support for this packet). They
20209 all default to @samp{auto}. For more information about each packet,
20210 see @ref{Remote Protocol}.
20212 During normal use, you should not have to use any of these commands.
20213 If you do, that may be a bug in your remote debugging stub, or a bug
20214 in @value{GDBN}. You may want to report the problem to the
20215 @value{GDBN} developers.
20217 For each packet @var{name}, the command to enable or disable the
20218 packet is @code{set remote @var{name}-packet}. The available settings
20221 @multitable @columnfractions 0.28 0.32 0.25
20224 @tab Related Features
20226 @item @code{fetch-register}
20228 @tab @code{info registers}
20230 @item @code{set-register}
20234 @item @code{binary-download}
20236 @tab @code{load}, @code{set}
20238 @item @code{read-aux-vector}
20239 @tab @code{qXfer:auxv:read}
20240 @tab @code{info auxv}
20242 @item @code{symbol-lookup}
20243 @tab @code{qSymbol}
20244 @tab Detecting multiple threads
20246 @item @code{attach}
20247 @tab @code{vAttach}
20250 @item @code{verbose-resume}
20252 @tab Stepping or resuming multiple threads
20258 @item @code{software-breakpoint}
20262 @item @code{hardware-breakpoint}
20266 @item @code{write-watchpoint}
20270 @item @code{read-watchpoint}
20274 @item @code{access-watchpoint}
20278 @item @code{pid-to-exec-file}
20279 @tab @code{qXfer:exec-file:read}
20280 @tab @code{attach}, @code{run}
20282 @item @code{target-features}
20283 @tab @code{qXfer:features:read}
20284 @tab @code{set architecture}
20286 @item @code{library-info}
20287 @tab @code{qXfer:libraries:read}
20288 @tab @code{info sharedlibrary}
20290 @item @code{memory-map}
20291 @tab @code{qXfer:memory-map:read}
20292 @tab @code{info mem}
20294 @item @code{read-sdata-object}
20295 @tab @code{qXfer:sdata:read}
20296 @tab @code{print $_sdata}
20298 @item @code{read-spu-object}
20299 @tab @code{qXfer:spu:read}
20300 @tab @code{info spu}
20302 @item @code{write-spu-object}
20303 @tab @code{qXfer:spu:write}
20304 @tab @code{info spu}
20306 @item @code{read-siginfo-object}
20307 @tab @code{qXfer:siginfo:read}
20308 @tab @code{print $_siginfo}
20310 @item @code{write-siginfo-object}
20311 @tab @code{qXfer:siginfo:write}
20312 @tab @code{set $_siginfo}
20314 @item @code{threads}
20315 @tab @code{qXfer:threads:read}
20316 @tab @code{info threads}
20318 @item @code{get-thread-local-@*storage-address}
20319 @tab @code{qGetTLSAddr}
20320 @tab Displaying @code{__thread} variables
20322 @item @code{get-thread-information-block-address}
20323 @tab @code{qGetTIBAddr}
20324 @tab Display MS-Windows Thread Information Block.
20326 @item @code{search-memory}
20327 @tab @code{qSearch:memory}
20330 @item @code{supported-packets}
20331 @tab @code{qSupported}
20332 @tab Remote communications parameters
20334 @item @code{catch-syscalls}
20335 @tab @code{QCatchSyscalls}
20336 @tab @code{catch syscall}
20338 @item @code{pass-signals}
20339 @tab @code{QPassSignals}
20340 @tab @code{handle @var{signal}}
20342 @item @code{program-signals}
20343 @tab @code{QProgramSignals}
20344 @tab @code{handle @var{signal}}
20346 @item @code{hostio-close-packet}
20347 @tab @code{vFile:close}
20348 @tab @code{remote get}, @code{remote put}
20350 @item @code{hostio-open-packet}
20351 @tab @code{vFile:open}
20352 @tab @code{remote get}, @code{remote put}
20354 @item @code{hostio-pread-packet}
20355 @tab @code{vFile:pread}
20356 @tab @code{remote get}, @code{remote put}
20358 @item @code{hostio-pwrite-packet}
20359 @tab @code{vFile:pwrite}
20360 @tab @code{remote get}, @code{remote put}
20362 @item @code{hostio-unlink-packet}
20363 @tab @code{vFile:unlink}
20364 @tab @code{remote delete}
20366 @item @code{hostio-readlink-packet}
20367 @tab @code{vFile:readlink}
20370 @item @code{hostio-fstat-packet}
20371 @tab @code{vFile:fstat}
20374 @item @code{hostio-setfs-packet}
20375 @tab @code{vFile:setfs}
20378 @item @code{noack-packet}
20379 @tab @code{QStartNoAckMode}
20380 @tab Packet acknowledgment
20382 @item @code{osdata}
20383 @tab @code{qXfer:osdata:read}
20384 @tab @code{info os}
20386 @item @code{query-attached}
20387 @tab @code{qAttached}
20388 @tab Querying remote process attach state.
20390 @item @code{trace-buffer-size}
20391 @tab @code{QTBuffer:size}
20392 @tab @code{set trace-buffer-size}
20394 @item @code{trace-status}
20395 @tab @code{qTStatus}
20396 @tab @code{tstatus}
20398 @item @code{traceframe-info}
20399 @tab @code{qXfer:traceframe-info:read}
20400 @tab Traceframe info
20402 @item @code{install-in-trace}
20403 @tab @code{InstallInTrace}
20404 @tab Install tracepoint in tracing
20406 @item @code{disable-randomization}
20407 @tab @code{QDisableRandomization}
20408 @tab @code{set disable-randomization}
20410 @item @code{conditional-breakpoints-packet}
20411 @tab @code{Z0 and Z1}
20412 @tab @code{Support for target-side breakpoint condition evaluation}
20414 @item @code{multiprocess-extensions}
20415 @tab @code{multiprocess extensions}
20416 @tab Debug multiple processes and remote process PID awareness
20418 @item @code{swbreak-feature}
20419 @tab @code{swbreak stop reason}
20422 @item @code{hwbreak-feature}
20423 @tab @code{hwbreak stop reason}
20426 @item @code{fork-event-feature}
20427 @tab @code{fork stop reason}
20430 @item @code{vfork-event-feature}
20431 @tab @code{vfork stop reason}
20434 @item @code{exec-event-feature}
20435 @tab @code{exec stop reason}
20438 @item @code{thread-events}
20439 @tab @code{QThreadEvents}
20440 @tab Tracking thread lifetime.
20442 @item @code{no-resumed-stop-reply}
20443 @tab @code{no resumed thread left stop reply}
20444 @tab Tracking thread lifetime.
20449 @section Implementing a Remote Stub
20451 @cindex debugging stub, example
20452 @cindex remote stub, example
20453 @cindex stub example, remote debugging
20454 The stub files provided with @value{GDBN} implement the target side of the
20455 communication protocol, and the @value{GDBN} side is implemented in the
20456 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
20457 these subroutines to communicate, and ignore the details. (If you're
20458 implementing your own stub file, you can still ignore the details: start
20459 with one of the existing stub files. @file{sparc-stub.c} is the best
20460 organized, and therefore the easiest to read.)
20462 @cindex remote serial debugging, overview
20463 To debug a program running on another machine (the debugging
20464 @dfn{target} machine), you must first arrange for all the usual
20465 prerequisites for the program to run by itself. For example, for a C
20470 A startup routine to set up the C runtime environment; these usually
20471 have a name like @file{crt0}. The startup routine may be supplied by
20472 your hardware supplier, or you may have to write your own.
20475 A C subroutine library to support your program's
20476 subroutine calls, notably managing input and output.
20479 A way of getting your program to the other machine---for example, a
20480 download program. These are often supplied by the hardware
20481 manufacturer, but you may have to write your own from hardware
20485 The next step is to arrange for your program to use a serial port to
20486 communicate with the machine where @value{GDBN} is running (the @dfn{host}
20487 machine). In general terms, the scheme looks like this:
20491 @value{GDBN} already understands how to use this protocol; when everything
20492 else is set up, you can simply use the @samp{target remote} command
20493 (@pxref{Targets,,Specifying a Debugging Target}).
20495 @item On the target,
20496 you must link with your program a few special-purpose subroutines that
20497 implement the @value{GDBN} remote serial protocol. The file containing these
20498 subroutines is called a @dfn{debugging stub}.
20500 On certain remote targets, you can use an auxiliary program
20501 @code{gdbserver} instead of linking a stub into your program.
20502 @xref{Server,,Using the @code{gdbserver} Program}, for details.
20505 The debugging stub is specific to the architecture of the remote
20506 machine; for example, use @file{sparc-stub.c} to debug programs on
20509 @cindex remote serial stub list
20510 These working remote stubs are distributed with @value{GDBN}:
20515 @cindex @file{i386-stub.c}
20518 For Intel 386 and compatible architectures.
20521 @cindex @file{m68k-stub.c}
20522 @cindex Motorola 680x0
20524 For Motorola 680x0 architectures.
20527 @cindex @file{sh-stub.c}
20530 For Renesas SH architectures.
20533 @cindex @file{sparc-stub.c}
20535 For @sc{sparc} architectures.
20537 @item sparcl-stub.c
20538 @cindex @file{sparcl-stub.c}
20541 For Fujitsu @sc{sparclite} architectures.
20545 The @file{README} file in the @value{GDBN} distribution may list other
20546 recently added stubs.
20549 * Stub Contents:: What the stub can do for you
20550 * Bootstrapping:: What you must do for the stub
20551 * Debug Session:: Putting it all together
20554 @node Stub Contents
20555 @subsection What the Stub Can Do for You
20557 @cindex remote serial stub
20558 The debugging stub for your architecture supplies these three
20562 @item set_debug_traps
20563 @findex set_debug_traps
20564 @cindex remote serial stub, initialization
20565 This routine arranges for @code{handle_exception} to run when your
20566 program stops. You must call this subroutine explicitly in your
20567 program's startup code.
20569 @item handle_exception
20570 @findex handle_exception
20571 @cindex remote serial stub, main routine
20572 This is the central workhorse, but your program never calls it
20573 explicitly---the setup code arranges for @code{handle_exception} to
20574 run when a trap is triggered.
20576 @code{handle_exception} takes control when your program stops during
20577 execution (for example, on a breakpoint), and mediates communications
20578 with @value{GDBN} on the host machine. This is where the communications
20579 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
20580 representative on the target machine. It begins by sending summary
20581 information on the state of your program, then continues to execute,
20582 retrieving and transmitting any information @value{GDBN} needs, until you
20583 execute a @value{GDBN} command that makes your program resume; at that point,
20584 @code{handle_exception} returns control to your own code on the target
20588 @cindex @code{breakpoint} subroutine, remote
20589 Use this auxiliary subroutine to make your program contain a
20590 breakpoint. Depending on the particular situation, this may be the only
20591 way for @value{GDBN} to get control. For instance, if your target
20592 machine has some sort of interrupt button, you won't need to call this;
20593 pressing the interrupt button transfers control to
20594 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
20595 simply receiving characters on the serial port may also trigger a trap;
20596 again, in that situation, you don't need to call @code{breakpoint} from
20597 your own program---simply running @samp{target remote} from the host
20598 @value{GDBN} session gets control.
20600 Call @code{breakpoint} if none of these is true, or if you simply want
20601 to make certain your program stops at a predetermined point for the
20602 start of your debugging session.
20605 @node Bootstrapping
20606 @subsection What You Must Do for the Stub
20608 @cindex remote stub, support routines
20609 The debugging stubs that come with @value{GDBN} are set up for a particular
20610 chip architecture, but they have no information about the rest of your
20611 debugging target machine.
20613 First of all you need to tell the stub how to communicate with the
20617 @item int getDebugChar()
20618 @findex getDebugChar
20619 Write this subroutine to read a single character from the serial port.
20620 It may be identical to @code{getchar} for your target system; a
20621 different name is used to allow you to distinguish the two if you wish.
20623 @item void putDebugChar(int)
20624 @findex putDebugChar
20625 Write this subroutine to write a single character to the serial port.
20626 It may be identical to @code{putchar} for your target system; a
20627 different name is used to allow you to distinguish the two if you wish.
20630 @cindex control C, and remote debugging
20631 @cindex interrupting remote targets
20632 If you want @value{GDBN} to be able to stop your program while it is
20633 running, you need to use an interrupt-driven serial driver, and arrange
20634 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
20635 character). That is the character which @value{GDBN} uses to tell the
20636 remote system to stop.
20638 Getting the debugging target to return the proper status to @value{GDBN}
20639 probably requires changes to the standard stub; one quick and dirty way
20640 is to just execute a breakpoint instruction (the ``dirty'' part is that
20641 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
20643 Other routines you need to supply are:
20646 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
20647 @findex exceptionHandler
20648 Write this function to install @var{exception_address} in the exception
20649 handling tables. You need to do this because the stub does not have any
20650 way of knowing what the exception handling tables on your target system
20651 are like (for example, the processor's table might be in @sc{rom},
20652 containing entries which point to a table in @sc{ram}).
20653 The @var{exception_number} specifies the exception which should be changed;
20654 its meaning is architecture-dependent (for example, different numbers
20655 might represent divide by zero, misaligned access, etc). When this
20656 exception occurs, control should be transferred directly to
20657 @var{exception_address}, and the processor state (stack, registers,
20658 and so on) should be just as it is when a processor exception occurs. So if
20659 you want to use a jump instruction to reach @var{exception_address}, it
20660 should be a simple jump, not a jump to subroutine.
20662 For the 386, @var{exception_address} should be installed as an interrupt
20663 gate so that interrupts are masked while the handler runs. The gate
20664 should be at privilege level 0 (the most privileged level). The
20665 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
20666 help from @code{exceptionHandler}.
20668 @item void flush_i_cache()
20669 @findex flush_i_cache
20670 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
20671 instruction cache, if any, on your target machine. If there is no
20672 instruction cache, this subroutine may be a no-op.
20674 On target machines that have instruction caches, @value{GDBN} requires this
20675 function to make certain that the state of your program is stable.
20679 You must also make sure this library routine is available:
20682 @item void *memset(void *, int, int)
20684 This is the standard library function @code{memset} that sets an area of
20685 memory to a known value. If you have one of the free versions of
20686 @code{libc.a}, @code{memset} can be found there; otherwise, you must
20687 either obtain it from your hardware manufacturer, or write your own.
20690 If you do not use the GNU C compiler, you may need other standard
20691 library subroutines as well; this varies from one stub to another,
20692 but in general the stubs are likely to use any of the common library
20693 subroutines which @code{@value{NGCC}} generates as inline code.
20696 @node Debug Session
20697 @subsection Putting it All Together
20699 @cindex remote serial debugging summary
20700 In summary, when your program is ready to debug, you must follow these
20705 Make sure you have defined the supporting low-level routines
20706 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
20708 @code{getDebugChar}, @code{putDebugChar},
20709 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
20713 Insert these lines in your program's startup code, before the main
20714 procedure is called:
20721 On some machines, when a breakpoint trap is raised, the hardware
20722 automatically makes the PC point to the instruction after the
20723 breakpoint. If your machine doesn't do that, you may need to adjust
20724 @code{handle_exception} to arrange for it to return to the instruction
20725 after the breakpoint on this first invocation, so that your program
20726 doesn't keep hitting the initial breakpoint instead of making
20730 For the 680x0 stub only, you need to provide a variable called
20731 @code{exceptionHook}. Normally you just use:
20734 void (*exceptionHook)() = 0;
20738 but if before calling @code{set_debug_traps}, you set it to point to a
20739 function in your program, that function is called when
20740 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
20741 error). The function indicated by @code{exceptionHook} is called with
20742 one parameter: an @code{int} which is the exception number.
20745 Compile and link together: your program, the @value{GDBN} debugging stub for
20746 your target architecture, and the supporting subroutines.
20749 Make sure you have a serial connection between your target machine and
20750 the @value{GDBN} host, and identify the serial port on the host.
20753 @c The "remote" target now provides a `load' command, so we should
20754 @c document that. FIXME.
20755 Download your program to your target machine (or get it there by
20756 whatever means the manufacturer provides), and start it.
20759 Start @value{GDBN} on the host, and connect to the target
20760 (@pxref{Connecting,,Connecting to a Remote Target}).
20764 @node Configurations
20765 @chapter Configuration-Specific Information
20767 While nearly all @value{GDBN} commands are available for all native and
20768 cross versions of the debugger, there are some exceptions. This chapter
20769 describes things that are only available in certain configurations.
20771 There are three major categories of configurations: native
20772 configurations, where the host and target are the same, embedded
20773 operating system configurations, which are usually the same for several
20774 different processor architectures, and bare embedded processors, which
20775 are quite different from each other.
20780 * Embedded Processors::
20787 This section describes details specific to particular native
20791 * BSD libkvm Interface:: Debugging BSD kernel memory images
20792 * SVR4 Process Information:: SVR4 process information
20793 * DJGPP Native:: Features specific to the DJGPP port
20794 * Cygwin Native:: Features specific to the Cygwin port
20795 * Hurd Native:: Features specific to @sc{gnu} Hurd
20796 * Darwin:: Features specific to Darwin
20799 @node BSD libkvm Interface
20800 @subsection BSD libkvm Interface
20803 @cindex kernel memory image
20804 @cindex kernel crash dump
20806 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
20807 interface that provides a uniform interface for accessing kernel virtual
20808 memory images, including live systems and crash dumps. @value{GDBN}
20809 uses this interface to allow you to debug live kernels and kernel crash
20810 dumps on many native BSD configurations. This is implemented as a
20811 special @code{kvm} debugging target. For debugging a live system, load
20812 the currently running kernel into @value{GDBN} and connect to the
20816 (@value{GDBP}) @b{target kvm}
20819 For debugging crash dumps, provide the file name of the crash dump as an
20823 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
20826 Once connected to the @code{kvm} target, the following commands are
20832 Set current context from the @dfn{Process Control Block} (PCB) address.
20835 Set current context from proc address. This command isn't available on
20836 modern FreeBSD systems.
20839 @node SVR4 Process Information
20840 @subsection SVR4 Process Information
20842 @cindex examine process image
20843 @cindex process info via @file{/proc}
20845 Many versions of SVR4 and compatible systems provide a facility called
20846 @samp{/proc} that can be used to examine the image of a running
20847 process using file-system subroutines.
20849 If @value{GDBN} is configured for an operating system with this
20850 facility, the command @code{info proc} is available to report
20851 information about the process running your program, or about any
20852 process running on your system. This includes, as of this writing,
20853 @sc{gnu}/Linux and Solaris, for example.
20855 This command may also work on core files that were created on a system
20856 that has the @samp{/proc} facility.
20862 @itemx info proc @var{process-id}
20863 Summarize available information about any running process. If a
20864 process ID is specified by @var{process-id}, display information about
20865 that process; otherwise display information about the program being
20866 debugged. The summary includes the debugged process ID, the command
20867 line used to invoke it, its current working directory, and its
20868 executable file's absolute file name.
20870 On some systems, @var{process-id} can be of the form
20871 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
20872 within a process. If the optional @var{pid} part is missing, it means
20873 a thread from the process being debugged (the leading @samp{/} still
20874 needs to be present, or else @value{GDBN} will interpret the number as
20875 a process ID rather than a thread ID).
20877 @item info proc cmdline
20878 @cindex info proc cmdline
20879 Show the original command line of the process. This command is
20880 specific to @sc{gnu}/Linux.
20882 @item info proc cwd
20883 @cindex info proc cwd
20884 Show the current working directory of the process. This command is
20885 specific to @sc{gnu}/Linux.
20887 @item info proc exe
20888 @cindex info proc exe
20889 Show the name of executable of the process. This command is specific
20892 @item info proc mappings
20893 @cindex memory address space mappings
20894 Report the memory address space ranges accessible in the program, with
20895 information on whether the process has read, write, or execute access
20896 rights to each range. On @sc{gnu}/Linux systems, each memory range
20897 includes the object file which is mapped to that range, instead of the
20898 memory access rights to that range.
20900 @item info proc stat
20901 @itemx info proc status
20902 @cindex process detailed status information
20903 These subcommands are specific to @sc{gnu}/Linux systems. They show
20904 the process-related information, including the user ID and group ID;
20905 how many threads are there in the process; its virtual memory usage;
20906 the signals that are pending, blocked, and ignored; its TTY; its
20907 consumption of system and user time; its stack size; its @samp{nice}
20908 value; etc. For more information, see the @samp{proc} man page
20909 (type @kbd{man 5 proc} from your shell prompt).
20911 @item info proc all
20912 Show all the information about the process described under all of the
20913 above @code{info proc} subcommands.
20916 @comment These sub-options of 'info proc' were not included when
20917 @comment procfs.c was re-written. Keep their descriptions around
20918 @comment against the day when someone finds the time to put them back in.
20919 @kindex info proc times
20920 @item info proc times
20921 Starting time, user CPU time, and system CPU time for your program and
20924 @kindex info proc id
20926 Report on the process IDs related to your program: its own process ID,
20927 the ID of its parent, the process group ID, and the session ID.
20930 @item set procfs-trace
20931 @kindex set procfs-trace
20932 @cindex @code{procfs} API calls
20933 This command enables and disables tracing of @code{procfs} API calls.
20935 @item show procfs-trace
20936 @kindex show procfs-trace
20937 Show the current state of @code{procfs} API call tracing.
20939 @item set procfs-file @var{file}
20940 @kindex set procfs-file
20941 Tell @value{GDBN} to write @code{procfs} API trace to the named
20942 @var{file}. @value{GDBN} appends the trace info to the previous
20943 contents of the file. The default is to display the trace on the
20946 @item show procfs-file
20947 @kindex show procfs-file
20948 Show the file to which @code{procfs} API trace is written.
20950 @item proc-trace-entry
20951 @itemx proc-trace-exit
20952 @itemx proc-untrace-entry
20953 @itemx proc-untrace-exit
20954 @kindex proc-trace-entry
20955 @kindex proc-trace-exit
20956 @kindex proc-untrace-entry
20957 @kindex proc-untrace-exit
20958 These commands enable and disable tracing of entries into and exits
20959 from the @code{syscall} interface.
20962 @kindex info pidlist
20963 @cindex process list, QNX Neutrino
20964 For QNX Neutrino only, this command displays the list of all the
20965 processes and all the threads within each process.
20968 @kindex info meminfo
20969 @cindex mapinfo list, QNX Neutrino
20970 For QNX Neutrino only, this command displays the list of all mapinfos.
20974 @subsection Features for Debugging @sc{djgpp} Programs
20975 @cindex @sc{djgpp} debugging
20976 @cindex native @sc{djgpp} debugging
20977 @cindex MS-DOS-specific commands
20980 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
20981 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
20982 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
20983 top of real-mode DOS systems and their emulations.
20985 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
20986 defines a few commands specific to the @sc{djgpp} port. This
20987 subsection describes those commands.
20992 This is a prefix of @sc{djgpp}-specific commands which print
20993 information about the target system and important OS structures.
20996 @cindex MS-DOS system info
20997 @cindex free memory information (MS-DOS)
20998 @item info dos sysinfo
20999 This command displays assorted information about the underlying
21000 platform: the CPU type and features, the OS version and flavor, the
21001 DPMI version, and the available conventional and DPMI memory.
21006 @cindex segment descriptor tables
21007 @cindex descriptor tables display
21009 @itemx info dos ldt
21010 @itemx info dos idt
21011 These 3 commands display entries from, respectively, Global, Local,
21012 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
21013 tables are data structures which store a descriptor for each segment
21014 that is currently in use. The segment's selector is an index into a
21015 descriptor table; the table entry for that index holds the
21016 descriptor's base address and limit, and its attributes and access
21019 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
21020 segment (used for both data and the stack), and a DOS segment (which
21021 allows access to DOS/BIOS data structures and absolute addresses in
21022 conventional memory). However, the DPMI host will usually define
21023 additional segments in order to support the DPMI environment.
21025 @cindex garbled pointers
21026 These commands allow to display entries from the descriptor tables.
21027 Without an argument, all entries from the specified table are
21028 displayed. An argument, which should be an integer expression, means
21029 display a single entry whose index is given by the argument. For
21030 example, here's a convenient way to display information about the
21031 debugged program's data segment:
21034 @exdent @code{(@value{GDBP}) info dos ldt $ds}
21035 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
21039 This comes in handy when you want to see whether a pointer is outside
21040 the data segment's limit (i.e.@: @dfn{garbled}).
21042 @cindex page tables display (MS-DOS)
21044 @itemx info dos pte
21045 These two commands display entries from, respectively, the Page
21046 Directory and the Page Tables. Page Directories and Page Tables are
21047 data structures which control how virtual memory addresses are mapped
21048 into physical addresses. A Page Table includes an entry for every
21049 page of memory that is mapped into the program's address space; there
21050 may be several Page Tables, each one holding up to 4096 entries. A
21051 Page Directory has up to 4096 entries, one each for every Page Table
21052 that is currently in use.
21054 Without an argument, @kbd{info dos pde} displays the entire Page
21055 Directory, and @kbd{info dos pte} displays all the entries in all of
21056 the Page Tables. An argument, an integer expression, given to the
21057 @kbd{info dos pde} command means display only that entry from the Page
21058 Directory table. An argument given to the @kbd{info dos pte} command
21059 means display entries from a single Page Table, the one pointed to by
21060 the specified entry in the Page Directory.
21062 @cindex direct memory access (DMA) on MS-DOS
21063 These commands are useful when your program uses @dfn{DMA} (Direct
21064 Memory Access), which needs physical addresses to program the DMA
21067 These commands are supported only with some DPMI servers.
21069 @cindex physical address from linear address
21070 @item info dos address-pte @var{addr}
21071 This command displays the Page Table entry for a specified linear
21072 address. The argument @var{addr} is a linear address which should
21073 already have the appropriate segment's base address added to it,
21074 because this command accepts addresses which may belong to @emph{any}
21075 segment. For example, here's how to display the Page Table entry for
21076 the page where a variable @code{i} is stored:
21079 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
21080 @exdent @code{Page Table entry for address 0x11a00d30:}
21081 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
21085 This says that @code{i} is stored at offset @code{0xd30} from the page
21086 whose physical base address is @code{0x02698000}, and shows all the
21087 attributes of that page.
21089 Note that you must cast the addresses of variables to a @code{char *},
21090 since otherwise the value of @code{__djgpp_base_address}, the base
21091 address of all variables and functions in a @sc{djgpp} program, will
21092 be added using the rules of C pointer arithmetics: if @code{i} is
21093 declared an @code{int}, @value{GDBN} will add 4 times the value of
21094 @code{__djgpp_base_address} to the address of @code{i}.
21096 Here's another example, it displays the Page Table entry for the
21100 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
21101 @exdent @code{Page Table entry for address 0x29110:}
21102 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
21106 (The @code{+ 3} offset is because the transfer buffer's address is the
21107 3rd member of the @code{_go32_info_block} structure.) The output
21108 clearly shows that this DPMI server maps the addresses in conventional
21109 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
21110 linear (@code{0x29110}) addresses are identical.
21112 This command is supported only with some DPMI servers.
21115 @cindex DOS serial data link, remote debugging
21116 In addition to native debugging, the DJGPP port supports remote
21117 debugging via a serial data link. The following commands are specific
21118 to remote serial debugging in the DJGPP port of @value{GDBN}.
21121 @kindex set com1base
21122 @kindex set com1irq
21123 @kindex set com2base
21124 @kindex set com2irq
21125 @kindex set com3base
21126 @kindex set com3irq
21127 @kindex set com4base
21128 @kindex set com4irq
21129 @item set com1base @var{addr}
21130 This command sets the base I/O port address of the @file{COM1} serial
21133 @item set com1irq @var{irq}
21134 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
21135 for the @file{COM1} serial port.
21137 There are similar commands @samp{set com2base}, @samp{set com3irq},
21138 etc.@: for setting the port address and the @code{IRQ} lines for the
21141 @kindex show com1base
21142 @kindex show com1irq
21143 @kindex show com2base
21144 @kindex show com2irq
21145 @kindex show com3base
21146 @kindex show com3irq
21147 @kindex show com4base
21148 @kindex show com4irq
21149 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
21150 display the current settings of the base address and the @code{IRQ}
21151 lines used by the COM ports.
21154 @kindex info serial
21155 @cindex DOS serial port status
21156 This command prints the status of the 4 DOS serial ports. For each
21157 port, it prints whether it's active or not, its I/O base address and
21158 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
21159 counts of various errors encountered so far.
21163 @node Cygwin Native
21164 @subsection Features for Debugging MS Windows PE Executables
21165 @cindex MS Windows debugging
21166 @cindex native Cygwin debugging
21167 @cindex Cygwin-specific commands
21169 @value{GDBN} supports native debugging of MS Windows programs, including
21170 DLLs with and without symbolic debugging information.
21172 @cindex Ctrl-BREAK, MS-Windows
21173 @cindex interrupt debuggee on MS-Windows
21174 MS-Windows programs that call @code{SetConsoleMode} to switch off the
21175 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
21176 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
21177 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
21178 sequence, which can be used to interrupt the debuggee even if it
21181 There are various additional Cygwin-specific commands, described in
21182 this section. Working with DLLs that have no debugging symbols is
21183 described in @ref{Non-debug DLL Symbols}.
21188 This is a prefix of MS Windows-specific commands which print
21189 information about the target system and important OS structures.
21191 @item info w32 selector
21192 This command displays information returned by
21193 the Win32 API @code{GetThreadSelectorEntry} function.
21194 It takes an optional argument that is evaluated to
21195 a long value to give the information about this given selector.
21196 Without argument, this command displays information
21197 about the six segment registers.
21199 @item info w32 thread-information-block
21200 This command displays thread specific information stored in the
21201 Thread Information Block (readable on the X86 CPU family using @code{$fs}
21202 selector for 32-bit programs and @code{$gs} for 64-bit programs).
21204 @kindex set cygwin-exceptions
21205 @cindex debugging the Cygwin DLL
21206 @cindex Cygwin DLL, debugging
21207 @item set cygwin-exceptions @var{mode}
21208 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
21209 happen inside the Cygwin DLL. If @var{mode} is @code{off},
21210 @value{GDBN} will delay recognition of exceptions, and may ignore some
21211 exceptions which seem to be caused by internal Cygwin DLL
21212 ``bookkeeping''. This option is meant primarily for debugging the
21213 Cygwin DLL itself; the default value is @code{off} to avoid annoying
21214 @value{GDBN} users with false @code{SIGSEGV} signals.
21216 @kindex show cygwin-exceptions
21217 @item show cygwin-exceptions
21218 Displays whether @value{GDBN} will break on exceptions that happen
21219 inside the Cygwin DLL itself.
21221 @kindex set new-console
21222 @item set new-console @var{mode}
21223 If @var{mode} is @code{on} the debuggee will
21224 be started in a new console on next start.
21225 If @var{mode} is @code{off}, the debuggee will
21226 be started in the same console as the debugger.
21228 @kindex show new-console
21229 @item show new-console
21230 Displays whether a new console is used
21231 when the debuggee is started.
21233 @kindex set new-group
21234 @item set new-group @var{mode}
21235 This boolean value controls whether the debuggee should
21236 start a new group or stay in the same group as the debugger.
21237 This affects the way the Windows OS handles
21240 @kindex show new-group
21241 @item show new-group
21242 Displays current value of new-group boolean.
21244 @kindex set debugevents
21245 @item set debugevents
21246 This boolean value adds debug output concerning kernel events related
21247 to the debuggee seen by the debugger. This includes events that
21248 signal thread and process creation and exit, DLL loading and
21249 unloading, console interrupts, and debugging messages produced by the
21250 Windows @code{OutputDebugString} API call.
21252 @kindex set debugexec
21253 @item set debugexec
21254 This boolean value adds debug output concerning execute events
21255 (such as resume thread) seen by the debugger.
21257 @kindex set debugexceptions
21258 @item set debugexceptions
21259 This boolean value adds debug output concerning exceptions in the
21260 debuggee seen by the debugger.
21262 @kindex set debugmemory
21263 @item set debugmemory
21264 This boolean value adds debug output concerning debuggee memory reads
21265 and writes by the debugger.
21269 This boolean values specifies whether the debuggee is called
21270 via a shell or directly (default value is on).
21274 Displays if the debuggee will be started with a shell.
21279 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
21282 @node Non-debug DLL Symbols
21283 @subsubsection Support for DLLs without Debugging Symbols
21284 @cindex DLLs with no debugging symbols
21285 @cindex Minimal symbols and DLLs
21287 Very often on windows, some of the DLLs that your program relies on do
21288 not include symbolic debugging information (for example,
21289 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
21290 symbols in a DLL, it relies on the minimal amount of symbolic
21291 information contained in the DLL's export table. This section
21292 describes working with such symbols, known internally to @value{GDBN} as
21293 ``minimal symbols''.
21295 Note that before the debugged program has started execution, no DLLs
21296 will have been loaded. The easiest way around this problem is simply to
21297 start the program --- either by setting a breakpoint or letting the
21298 program run once to completion.
21300 @subsubsection DLL Name Prefixes
21302 In keeping with the naming conventions used by the Microsoft debugging
21303 tools, DLL export symbols are made available with a prefix based on the
21304 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
21305 also entered into the symbol table, so @code{CreateFileA} is often
21306 sufficient. In some cases there will be name clashes within a program
21307 (particularly if the executable itself includes full debugging symbols)
21308 necessitating the use of the fully qualified name when referring to the
21309 contents of the DLL. Use single-quotes around the name to avoid the
21310 exclamation mark (``!'') being interpreted as a language operator.
21312 Note that the internal name of the DLL may be all upper-case, even
21313 though the file name of the DLL is lower-case, or vice-versa. Since
21314 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
21315 some confusion. If in doubt, try the @code{info functions} and
21316 @code{info variables} commands or even @code{maint print msymbols}
21317 (@pxref{Symbols}). Here's an example:
21320 (@value{GDBP}) info function CreateFileA
21321 All functions matching regular expression "CreateFileA":
21323 Non-debugging symbols:
21324 0x77e885f4 CreateFileA
21325 0x77e885f4 KERNEL32!CreateFileA
21329 (@value{GDBP}) info function !
21330 All functions matching regular expression "!":
21332 Non-debugging symbols:
21333 0x6100114c cygwin1!__assert
21334 0x61004034 cygwin1!_dll_crt0@@0
21335 0x61004240 cygwin1!dll_crt0(per_process *)
21339 @subsubsection Working with Minimal Symbols
21341 Symbols extracted from a DLL's export table do not contain very much
21342 type information. All that @value{GDBN} can do is guess whether a symbol
21343 refers to a function or variable depending on the linker section that
21344 contains the symbol. Also note that the actual contents of the memory
21345 contained in a DLL are not available unless the program is running. This
21346 means that you cannot examine the contents of a variable or disassemble
21347 a function within a DLL without a running program.
21349 Variables are generally treated as pointers and dereferenced
21350 automatically. For this reason, it is often necessary to prefix a
21351 variable name with the address-of operator (``&'') and provide explicit
21352 type information in the command. Here's an example of the type of
21356 (@value{GDBP}) print 'cygwin1!__argv'
21361 (@value{GDBP}) x 'cygwin1!__argv'
21362 0x10021610: "\230y\""
21365 And two possible solutions:
21368 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
21369 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
21373 (@value{GDBP}) x/2x &'cygwin1!__argv'
21374 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
21375 (@value{GDBP}) x/x 0x10021608
21376 0x10021608: 0x0022fd98
21377 (@value{GDBP}) x/s 0x0022fd98
21378 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
21381 Setting a break point within a DLL is possible even before the program
21382 starts execution. However, under these circumstances, @value{GDBN} can't
21383 examine the initial instructions of the function in order to skip the
21384 function's frame set-up code. You can work around this by using ``*&''
21385 to set the breakpoint at a raw memory address:
21388 (@value{GDBP}) break *&'python22!PyOS_Readline'
21389 Breakpoint 1 at 0x1e04eff0
21392 The author of these extensions is not entirely convinced that setting a
21393 break point within a shared DLL like @file{kernel32.dll} is completely
21397 @subsection Commands Specific to @sc{gnu} Hurd Systems
21398 @cindex @sc{gnu} Hurd debugging
21400 This subsection describes @value{GDBN} commands specific to the
21401 @sc{gnu} Hurd native debugging.
21406 @kindex set signals@r{, Hurd command}
21407 @kindex set sigs@r{, Hurd command}
21408 This command toggles the state of inferior signal interception by
21409 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
21410 affected by this command. @code{sigs} is a shorthand alias for
21415 @kindex show signals@r{, Hurd command}
21416 @kindex show sigs@r{, Hurd command}
21417 Show the current state of intercepting inferior's signals.
21419 @item set signal-thread
21420 @itemx set sigthread
21421 @kindex set signal-thread
21422 @kindex set sigthread
21423 This command tells @value{GDBN} which thread is the @code{libc} signal
21424 thread. That thread is run when a signal is delivered to a running
21425 process. @code{set sigthread} is the shorthand alias of @code{set
21428 @item show signal-thread
21429 @itemx show sigthread
21430 @kindex show signal-thread
21431 @kindex show sigthread
21432 These two commands show which thread will run when the inferior is
21433 delivered a signal.
21436 @kindex set stopped@r{, Hurd command}
21437 This commands tells @value{GDBN} that the inferior process is stopped,
21438 as with the @code{SIGSTOP} signal. The stopped process can be
21439 continued by delivering a signal to it.
21442 @kindex show stopped@r{, Hurd command}
21443 This command shows whether @value{GDBN} thinks the debuggee is
21446 @item set exceptions
21447 @kindex set exceptions@r{, Hurd command}
21448 Use this command to turn off trapping of exceptions in the inferior.
21449 When exception trapping is off, neither breakpoints nor
21450 single-stepping will work. To restore the default, set exception
21453 @item show exceptions
21454 @kindex show exceptions@r{, Hurd command}
21455 Show the current state of trapping exceptions in the inferior.
21457 @item set task pause
21458 @kindex set task@r{, Hurd commands}
21459 @cindex task attributes (@sc{gnu} Hurd)
21460 @cindex pause current task (@sc{gnu} Hurd)
21461 This command toggles task suspension when @value{GDBN} has control.
21462 Setting it to on takes effect immediately, and the task is suspended
21463 whenever @value{GDBN} gets control. Setting it to off will take
21464 effect the next time the inferior is continued. If this option is set
21465 to off, you can use @code{set thread default pause on} or @code{set
21466 thread pause on} (see below) to pause individual threads.
21468 @item show task pause
21469 @kindex show task@r{, Hurd commands}
21470 Show the current state of task suspension.
21472 @item set task detach-suspend-count
21473 @cindex task suspend count
21474 @cindex detach from task, @sc{gnu} Hurd
21475 This command sets the suspend count the task will be left with when
21476 @value{GDBN} detaches from it.
21478 @item show task detach-suspend-count
21479 Show the suspend count the task will be left with when detaching.
21481 @item set task exception-port
21482 @itemx set task excp
21483 @cindex task exception port, @sc{gnu} Hurd
21484 This command sets the task exception port to which @value{GDBN} will
21485 forward exceptions. The argument should be the value of the @dfn{send
21486 rights} of the task. @code{set task excp} is a shorthand alias.
21488 @item set noninvasive
21489 @cindex noninvasive task options
21490 This command switches @value{GDBN} to a mode that is the least
21491 invasive as far as interfering with the inferior is concerned. This
21492 is the same as using @code{set task pause}, @code{set exceptions}, and
21493 @code{set signals} to values opposite to the defaults.
21495 @item info send-rights
21496 @itemx info receive-rights
21497 @itemx info port-rights
21498 @itemx info port-sets
21499 @itemx info dead-names
21502 @cindex send rights, @sc{gnu} Hurd
21503 @cindex receive rights, @sc{gnu} Hurd
21504 @cindex port rights, @sc{gnu} Hurd
21505 @cindex port sets, @sc{gnu} Hurd
21506 @cindex dead names, @sc{gnu} Hurd
21507 These commands display information about, respectively, send rights,
21508 receive rights, port rights, port sets, and dead names of a task.
21509 There are also shorthand aliases: @code{info ports} for @code{info
21510 port-rights} and @code{info psets} for @code{info port-sets}.
21512 @item set thread pause
21513 @kindex set thread@r{, Hurd command}
21514 @cindex thread properties, @sc{gnu} Hurd
21515 @cindex pause current thread (@sc{gnu} Hurd)
21516 This command toggles current thread suspension when @value{GDBN} has
21517 control. Setting it to on takes effect immediately, and the current
21518 thread is suspended whenever @value{GDBN} gets control. Setting it to
21519 off will take effect the next time the inferior is continued.
21520 Normally, this command has no effect, since when @value{GDBN} has
21521 control, the whole task is suspended. However, if you used @code{set
21522 task pause off} (see above), this command comes in handy to suspend
21523 only the current thread.
21525 @item show thread pause
21526 @kindex show thread@r{, Hurd command}
21527 This command shows the state of current thread suspension.
21529 @item set thread run
21530 This command sets whether the current thread is allowed to run.
21532 @item show thread run
21533 Show whether the current thread is allowed to run.
21535 @item set thread detach-suspend-count
21536 @cindex thread suspend count, @sc{gnu} Hurd
21537 @cindex detach from thread, @sc{gnu} Hurd
21538 This command sets the suspend count @value{GDBN} will leave on a
21539 thread when detaching. This number is relative to the suspend count
21540 found by @value{GDBN} when it notices the thread; use @code{set thread
21541 takeover-suspend-count} to force it to an absolute value.
21543 @item show thread detach-suspend-count
21544 Show the suspend count @value{GDBN} will leave on the thread when
21547 @item set thread exception-port
21548 @itemx set thread excp
21549 Set the thread exception port to which to forward exceptions. This
21550 overrides the port set by @code{set task exception-port} (see above).
21551 @code{set thread excp} is the shorthand alias.
21553 @item set thread takeover-suspend-count
21554 Normally, @value{GDBN}'s thread suspend counts are relative to the
21555 value @value{GDBN} finds when it notices each thread. This command
21556 changes the suspend counts to be absolute instead.
21558 @item set thread default
21559 @itemx show thread default
21560 @cindex thread default settings, @sc{gnu} Hurd
21561 Each of the above @code{set thread} commands has a @code{set thread
21562 default} counterpart (e.g., @code{set thread default pause}, @code{set
21563 thread default exception-port}, etc.). The @code{thread default}
21564 variety of commands sets the default thread properties for all
21565 threads; you can then change the properties of individual threads with
21566 the non-default commands.
21573 @value{GDBN} provides the following commands specific to the Darwin target:
21576 @item set debug darwin @var{num}
21577 @kindex set debug darwin
21578 When set to a non zero value, enables debugging messages specific to
21579 the Darwin support. Higher values produce more verbose output.
21581 @item show debug darwin
21582 @kindex show debug darwin
21583 Show the current state of Darwin messages.
21585 @item set debug mach-o @var{num}
21586 @kindex set debug mach-o
21587 When set to a non zero value, enables debugging messages while
21588 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
21589 file format used on Darwin for object and executable files.) Higher
21590 values produce more verbose output. This is a command to diagnose
21591 problems internal to @value{GDBN} and should not be needed in normal
21594 @item show debug mach-o
21595 @kindex show debug mach-o
21596 Show the current state of Mach-O file messages.
21598 @item set mach-exceptions on
21599 @itemx set mach-exceptions off
21600 @kindex set mach-exceptions
21601 On Darwin, faults are first reported as a Mach exception and are then
21602 mapped to a Posix signal. Use this command to turn on trapping of
21603 Mach exceptions in the inferior. This might be sometimes useful to
21604 better understand the cause of a fault. The default is off.
21606 @item show mach-exceptions
21607 @kindex show mach-exceptions
21608 Show the current state of exceptions trapping.
21613 @section Embedded Operating Systems
21615 This section describes configurations involving the debugging of
21616 embedded operating systems that are available for several different
21619 @value{GDBN} includes the ability to debug programs running on
21620 various real-time operating systems.
21622 @node Embedded Processors
21623 @section Embedded Processors
21625 This section goes into details specific to particular embedded
21628 @cindex send command to simulator
21629 Whenever a specific embedded processor has a simulator, @value{GDBN}
21630 allows to send an arbitrary command to the simulator.
21633 @item sim @var{command}
21634 @kindex sim@r{, a command}
21635 Send an arbitrary @var{command} string to the simulator. Consult the
21636 documentation for the specific simulator in use for information about
21637 acceptable commands.
21643 * M32R/SDI:: Renesas M32R/SDI
21644 * M68K:: Motorola M68K
21645 * MicroBlaze:: Xilinx MicroBlaze
21646 * MIPS Embedded:: MIPS Embedded
21647 * PowerPC Embedded:: PowerPC Embedded
21650 * Super-H:: Renesas Super-H
21656 @value{GDBN} provides the following ARM-specific commands:
21659 @item set arm disassembler
21661 This commands selects from a list of disassembly styles. The
21662 @code{"std"} style is the standard style.
21664 @item show arm disassembler
21666 Show the current disassembly style.
21668 @item set arm apcs32
21669 @cindex ARM 32-bit mode
21670 This command toggles ARM operation mode between 32-bit and 26-bit.
21672 @item show arm apcs32
21673 Display the current usage of the ARM 32-bit mode.
21675 @item set arm fpu @var{fputype}
21676 This command sets the ARM floating-point unit (FPU) type. The
21677 argument @var{fputype} can be one of these:
21681 Determine the FPU type by querying the OS ABI.
21683 Software FPU, with mixed-endian doubles on little-endian ARM
21686 GCC-compiled FPA co-processor.
21688 Software FPU with pure-endian doubles.
21694 Show the current type of the FPU.
21697 This command forces @value{GDBN} to use the specified ABI.
21700 Show the currently used ABI.
21702 @item set arm fallback-mode (arm|thumb|auto)
21703 @value{GDBN} uses the symbol table, when available, to determine
21704 whether instructions are ARM or Thumb. This command controls
21705 @value{GDBN}'s default behavior when the symbol table is not
21706 available. The default is @samp{auto}, which causes @value{GDBN} to
21707 use the current execution mode (from the @code{T} bit in the @code{CPSR}
21710 @item show arm fallback-mode
21711 Show the current fallback instruction mode.
21713 @item set arm force-mode (arm|thumb|auto)
21714 This command overrides use of the symbol table to determine whether
21715 instructions are ARM or Thumb. The default is @samp{auto}, which
21716 causes @value{GDBN} to use the symbol table and then the setting
21717 of @samp{set arm fallback-mode}.
21719 @item show arm force-mode
21720 Show the current forced instruction mode.
21722 @item set debug arm
21723 Toggle whether to display ARM-specific debugging messages from the ARM
21724 target support subsystem.
21726 @item show debug arm
21727 Show whether ARM-specific debugging messages are enabled.
21731 @item target sim @r{[}@var{simargs}@r{]} @dots{}
21732 The @value{GDBN} ARM simulator accepts the following optional arguments.
21735 @item --swi-support=@var{type}
21736 Tell the simulator which SWI interfaces to support. The argument
21737 @var{type} may be a comma separated list of the following values.
21738 The default value is @code{all}.
21751 @subsection Renesas M32R/SDI
21753 The following commands are available for M32R/SDI:
21758 @cindex reset SDI connection, M32R
21759 This command resets the SDI connection.
21763 This command shows the SDI connection status.
21766 @kindex debug_chaos
21767 @cindex M32R/Chaos debugging
21768 Instructs the remote that M32R/Chaos debugging is to be used.
21770 @item use_debug_dma
21771 @kindex use_debug_dma
21772 Instructs the remote to use the DEBUG_DMA method of accessing memory.
21775 @kindex use_mon_code
21776 Instructs the remote to use the MON_CODE method of accessing memory.
21779 @kindex use_ib_break
21780 Instructs the remote to set breakpoints by IB break.
21782 @item use_dbt_break
21783 @kindex use_dbt_break
21784 Instructs the remote to set breakpoints by DBT.
21790 The Motorola m68k configuration includes ColdFire support.
21793 @subsection MicroBlaze
21794 @cindex Xilinx MicroBlaze
21795 @cindex XMD, Xilinx Microprocessor Debugger
21797 The MicroBlaze is a soft-core processor supported on various Xilinx
21798 FPGAs, such as Spartan or Virtex series. Boards with these processors
21799 usually have JTAG ports which connect to a host system running the Xilinx
21800 Embedded Development Kit (EDK) or Software Development Kit (SDK).
21801 This host system is used to download the configuration bitstream to
21802 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
21803 communicates with the target board using the JTAG interface and
21804 presents a @code{gdbserver} interface to the board. By default
21805 @code{xmd} uses port @code{1234}. (While it is possible to change
21806 this default port, it requires the use of undocumented @code{xmd}
21807 commands. Contact Xilinx support if you need to do this.)
21809 Use these GDB commands to connect to the MicroBlaze target processor.
21812 @item target remote :1234
21813 Use this command to connect to the target if you are running @value{GDBN}
21814 on the same system as @code{xmd}.
21816 @item target remote @var{xmd-host}:1234
21817 Use this command to connect to the target if it is connected to @code{xmd}
21818 running on a different system named @var{xmd-host}.
21821 Use this command to download a program to the MicroBlaze target.
21823 @item set debug microblaze @var{n}
21824 Enable MicroBlaze-specific debugging messages if non-zero.
21826 @item show debug microblaze @var{n}
21827 Show MicroBlaze-specific debugging level.
21830 @node MIPS Embedded
21831 @subsection @acronym{MIPS} Embedded
21833 @cindex @acronym{MIPS} boards
21834 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
21835 @acronym{MIPS} board attached to a serial line. This is available when
21836 you configure @value{GDBN} with @samp{--target=mips-elf}.
21839 Use these @value{GDBN} commands to specify the connection to your target board:
21842 @item target mips @var{port}
21843 @kindex target mips @var{port}
21844 To run a program on the board, start up @code{@value{GDBP}} with the
21845 name of your program as the argument. To connect to the board, use the
21846 command @samp{target mips @var{port}}, where @var{port} is the name of
21847 the serial port connected to the board. If the program has not already
21848 been downloaded to the board, you may use the @code{load} command to
21849 download it. You can then use all the usual @value{GDBN} commands.
21851 For example, this sequence connects to the target board through a serial
21852 port, and loads and runs a program called @var{prog} through the
21856 host$ @value{GDBP} @var{prog}
21857 @value{GDBN} is free software and @dots{}
21858 (@value{GDBP}) target mips /dev/ttyb
21859 (@value{GDBP}) load @var{prog}
21863 @item target mips @var{hostname}:@var{portnumber}
21864 On some @value{GDBN} host configurations, you can specify a TCP
21865 connection (for instance, to a serial line managed by a terminal
21866 concentrator) instead of a serial port, using the syntax
21867 @samp{@var{hostname}:@var{portnumber}}.
21869 @item target pmon @var{port}
21870 @kindex target pmon @var{port}
21873 @item target ddb @var{port}
21874 @kindex target ddb @var{port}
21875 NEC's DDB variant of PMON for Vr4300.
21877 @item target lsi @var{port}
21878 @kindex target lsi @var{port}
21879 LSI variant of PMON.
21885 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
21888 @item set mipsfpu double
21889 @itemx set mipsfpu single
21890 @itemx set mipsfpu none
21891 @itemx set mipsfpu auto
21892 @itemx show mipsfpu
21893 @kindex set mipsfpu
21894 @kindex show mipsfpu
21895 @cindex @acronym{MIPS} remote floating point
21896 @cindex floating point, @acronym{MIPS} remote
21897 If your target board does not support the @acronym{MIPS} floating point
21898 coprocessor, you should use the command @samp{set mipsfpu none} (if you
21899 need this, you may wish to put the command in your @value{GDBN} init
21900 file). This tells @value{GDBN} how to find the return value of
21901 functions which return floating point values. It also allows
21902 @value{GDBN} to avoid saving the floating point registers when calling
21903 functions on the board. If you are using a floating point coprocessor
21904 with only single precision floating point support, as on the @sc{r4650}
21905 processor, use the command @samp{set mipsfpu single}. The default
21906 double precision floating point coprocessor may be selected using
21907 @samp{set mipsfpu double}.
21909 In previous versions the only choices were double precision or no
21910 floating point, so @samp{set mipsfpu on} will select double precision
21911 and @samp{set mipsfpu off} will select no floating point.
21913 As usual, you can inquire about the @code{mipsfpu} variable with
21914 @samp{show mipsfpu}.
21916 @item set timeout @var{seconds}
21917 @itemx set retransmit-timeout @var{seconds}
21918 @itemx show timeout
21919 @itemx show retransmit-timeout
21920 @cindex @code{timeout}, @acronym{MIPS} protocol
21921 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
21922 @kindex set timeout
21923 @kindex show timeout
21924 @kindex set retransmit-timeout
21925 @kindex show retransmit-timeout
21926 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
21927 remote protocol, with the @code{set timeout @var{seconds}} command. The
21928 default is 5 seconds. Similarly, you can control the timeout used while
21929 waiting for an acknowledgment of a packet with the @code{set
21930 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
21931 You can inspect both values with @code{show timeout} and @code{show
21932 retransmit-timeout}. (These commands are @emph{only} available when
21933 @value{GDBN} is configured for @samp{--target=mips-elf}.)
21935 The timeout set by @code{set timeout} does not apply when @value{GDBN}
21936 is waiting for your program to stop. In that case, @value{GDBN} waits
21937 forever because it has no way of knowing how long the program is going
21938 to run before stopping.
21940 @item set syn-garbage-limit @var{num}
21941 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
21942 @cindex synchronize with remote @acronym{MIPS} target
21943 Limit the maximum number of characters @value{GDBN} should ignore when
21944 it tries to synchronize with the remote target. The default is 10
21945 characters. Setting the limit to -1 means there's no limit.
21947 @item show syn-garbage-limit
21948 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
21949 Show the current limit on the number of characters to ignore when
21950 trying to synchronize with the remote system.
21952 @item set monitor-prompt @var{prompt}
21953 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
21954 @cindex remote monitor prompt
21955 Tell @value{GDBN} to expect the specified @var{prompt} string from the
21956 remote monitor. The default depends on the target:
21966 @item show monitor-prompt
21967 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
21968 Show the current strings @value{GDBN} expects as the prompt from the
21971 @item set monitor-warnings
21972 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
21973 Enable or disable monitor warnings about hardware breakpoints. This
21974 has effect only for the @code{lsi} target. When on, @value{GDBN} will
21975 display warning messages whose codes are returned by the @code{lsi}
21976 PMON monitor for breakpoint commands.
21978 @item show monitor-warnings
21979 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
21980 Show the current setting of printing monitor warnings.
21982 @item pmon @var{command}
21983 @kindex pmon@r{, @acronym{MIPS} remote}
21984 @cindex send PMON command
21985 This command allows sending an arbitrary @var{command} string to the
21986 monitor. The monitor must be in debug mode for this to work.
21989 @node PowerPC Embedded
21990 @subsection PowerPC Embedded
21992 @cindex DVC register
21993 @value{GDBN} supports using the DVC (Data Value Compare) register to
21994 implement in hardware simple hardware watchpoint conditions of the form:
21997 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
21998 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
22001 The DVC register will be automatically used when @value{GDBN} detects
22002 such pattern in a condition expression, and the created watchpoint uses one
22003 debug register (either the @code{exact-watchpoints} option is on and the
22004 variable is scalar, or the variable has a length of one byte). This feature
22005 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
22008 When running on PowerPC embedded processors, @value{GDBN} automatically uses
22009 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
22010 in which case watchpoints using only one debug register are created when
22011 watching variables of scalar types.
22013 You can create an artificial array to watch an arbitrary memory
22014 region using one of the following commands (@pxref{Expressions}):
22017 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
22018 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
22021 PowerPC embedded processors support masked watchpoints. See the discussion
22022 about the @code{mask} argument in @ref{Set Watchpoints}.
22024 @cindex ranged breakpoint
22025 PowerPC embedded processors support hardware accelerated
22026 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
22027 the inferior whenever it executes an instruction at any address within
22028 the range it specifies. To set a ranged breakpoint in @value{GDBN},
22029 use the @code{break-range} command.
22031 @value{GDBN} provides the following PowerPC-specific commands:
22034 @kindex break-range
22035 @item break-range @var{start-location}, @var{end-location}
22036 Set a breakpoint for an address range given by
22037 @var{start-location} and @var{end-location}, which can specify a function name,
22038 a line number, an offset of lines from the current line or from the start
22039 location, or an address of an instruction (see @ref{Specify Location},
22040 for a list of all the possible ways to specify a @var{location}.)
22041 The breakpoint will stop execution of the inferior whenever it
22042 executes an instruction at any address within the specified range,
22043 (including @var{start-location} and @var{end-location}.)
22045 @kindex set powerpc
22046 @item set powerpc soft-float
22047 @itemx show powerpc soft-float
22048 Force @value{GDBN} to use (or not use) a software floating point calling
22049 convention. By default, @value{GDBN} selects the calling convention based
22050 on the selected architecture and the provided executable file.
22052 @item set powerpc vector-abi
22053 @itemx show powerpc vector-abi
22054 Force @value{GDBN} to use the specified calling convention for vector
22055 arguments and return values. The valid options are @samp{auto};
22056 @samp{generic}, to avoid vector registers even if they are present;
22057 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
22058 registers. By default, @value{GDBN} selects the calling convention
22059 based on the selected architecture and the provided executable file.
22061 @item set powerpc exact-watchpoints
22062 @itemx show powerpc exact-watchpoints
22063 Allow @value{GDBN} to use only one debug register when watching a variable
22064 of scalar type, thus assuming that the variable is accessed through the
22065 address of its first byte.
22070 @subsection Atmel AVR
22073 When configured for debugging the Atmel AVR, @value{GDBN} supports the
22074 following AVR-specific commands:
22077 @item info io_registers
22078 @kindex info io_registers@r{, AVR}
22079 @cindex I/O registers (Atmel AVR)
22080 This command displays information about the AVR I/O registers. For
22081 each register, @value{GDBN} prints its number and value.
22088 When configured for debugging CRIS, @value{GDBN} provides the
22089 following CRIS-specific commands:
22092 @item set cris-version @var{ver}
22093 @cindex CRIS version
22094 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
22095 The CRIS version affects register names and sizes. This command is useful in
22096 case autodetection of the CRIS version fails.
22098 @item show cris-version
22099 Show the current CRIS version.
22101 @item set cris-dwarf2-cfi
22102 @cindex DWARF-2 CFI and CRIS
22103 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
22104 Change to @samp{off} when using @code{gcc-cris} whose version is below
22107 @item show cris-dwarf2-cfi
22108 Show the current state of using DWARF-2 CFI.
22110 @item set cris-mode @var{mode}
22112 Set the current CRIS mode to @var{mode}. It should only be changed when
22113 debugging in guru mode, in which case it should be set to
22114 @samp{guru} (the default is @samp{normal}).
22116 @item show cris-mode
22117 Show the current CRIS mode.
22121 @subsection Renesas Super-H
22124 For the Renesas Super-H processor, @value{GDBN} provides these
22128 @item set sh calling-convention @var{convention}
22129 @kindex set sh calling-convention
22130 Set the calling-convention used when calling functions from @value{GDBN}.
22131 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
22132 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
22133 convention. If the DWARF-2 information of the called function specifies
22134 that the function follows the Renesas calling convention, the function
22135 is called using the Renesas calling convention. If the calling convention
22136 is set to @samp{renesas}, the Renesas calling convention is always used,
22137 regardless of the DWARF-2 information. This can be used to override the
22138 default of @samp{gcc} if debug information is missing, or the compiler
22139 does not emit the DWARF-2 calling convention entry for a function.
22141 @item show sh calling-convention
22142 @kindex show sh calling-convention
22143 Show the current calling convention setting.
22148 @node Architectures
22149 @section Architectures
22151 This section describes characteristics of architectures that affect
22152 all uses of @value{GDBN} with the architecture, both native and cross.
22159 * HPPA:: HP PA architecture
22160 * SPU:: Cell Broadband Engine SPU architecture
22166 @subsection AArch64
22167 @cindex AArch64 support
22169 When @value{GDBN} is debugging the AArch64 architecture, it provides the
22170 following special commands:
22173 @item set debug aarch64
22174 @kindex set debug aarch64
22175 This command determines whether AArch64 architecture-specific debugging
22176 messages are to be displayed.
22178 @item show debug aarch64
22179 Show whether AArch64 debugging messages are displayed.
22184 @subsection x86 Architecture-specific Issues
22187 @item set struct-convention @var{mode}
22188 @kindex set struct-convention
22189 @cindex struct return convention
22190 @cindex struct/union returned in registers
22191 Set the convention used by the inferior to return @code{struct}s and
22192 @code{union}s from functions to @var{mode}. Possible values of
22193 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
22194 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
22195 are returned on the stack, while @code{"reg"} means that a
22196 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
22197 be returned in a register.
22199 @item show struct-convention
22200 @kindex show struct-convention
22201 Show the current setting of the convention to return @code{struct}s
22206 @subsubsection Intel @dfn{Memory Protection Extensions} (MPX).
22207 @cindex Intel Memory Protection Extensions (MPX).
22209 Memory Protection Extension (MPX) adds the bound registers @samp{BND0}
22210 @footnote{The register named with capital letters represent the architecture
22211 registers.} through @samp{BND3}. Bound registers store a pair of 64-bit values
22212 which are the lower bound and upper bound. Bounds are effective addresses or
22213 memory locations. The upper bounds are architecturally represented in 1's
22214 complement form. A bound having lower bound = 0, and upper bound = 0
22215 (1's complement of all bits set) will allow access to the entire address space.
22217 @samp{BND0} through @samp{BND3} are represented in @value{GDBN} as @samp{bnd0raw}
22218 through @samp{bnd3raw}. Pseudo registers @samp{bnd0} through @samp{bnd3}
22219 display the upper bound performing the complement of one operation on the
22220 upper bound value, i.e.@ when upper bound in @samp{bnd0raw} is 0 in the
22221 @value{GDBN} @samp{bnd0} it will be @code{0xfff@dots{}}. In this sense it
22222 can also be noted that the upper bounds are inclusive.
22224 As an example, assume that the register BND0 holds bounds for a pointer having
22225 access allowed for the range between 0x32 and 0x71. The values present on
22226 bnd0raw and bnd registers are presented as follows:
22229 bnd0raw = @{0x32, 0xffffffff8e@}
22230 bnd0 = @{lbound = 0x32, ubound = 0x71@} : size 64
22233 This way the raw value can be accessed via bnd0raw@dots{}bnd3raw. Any
22234 change on bnd0@dots{}bnd3 or bnd0raw@dots{}bnd3raw is reflect on its
22235 counterpart. When the bnd0@dots{}bnd3 registers are displayed via
22236 Python, the display includes the memory size, in bits, accessible to
22239 Bounds can also be stored in bounds tables, which are stored in
22240 application memory. These tables store bounds for pointers by specifying
22241 the bounds pointer's value along with its bounds. Evaluating and changing
22242 bounds located in bound tables is therefore interesting while investigating
22243 bugs on MPX context. @value{GDBN} provides commands for this purpose:
22246 @item show mpx bound @var{pointer}
22247 @kindex show mpx bound
22248 Display bounds of the given @var{pointer}.
22250 @item set mpx bound @var{pointer}, @var{lbound}, @var{ubound}
22251 @kindex set mpx bound
22252 Set the bounds of a pointer in the bound table.
22253 This command takes three parameters: @var{pointer} is the pointers
22254 whose bounds are to be changed, @var{lbound} and @var{ubound} are new values
22255 for lower and upper bounds respectively.
22261 See the following section.
22264 @subsection @acronym{MIPS}
22266 @cindex stack on Alpha
22267 @cindex stack on @acronym{MIPS}
22268 @cindex Alpha stack
22269 @cindex @acronym{MIPS} stack
22270 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
22271 sometimes requires @value{GDBN} to search backward in the object code to
22272 find the beginning of a function.
22274 @cindex response time, @acronym{MIPS} debugging
22275 To improve response time (especially for embedded applications, where
22276 @value{GDBN} may be restricted to a slow serial line for this search)
22277 you may want to limit the size of this search, using one of these
22281 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
22282 @item set heuristic-fence-post @var{limit}
22283 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
22284 search for the beginning of a function. A value of @var{0} (the
22285 default) means there is no limit. However, except for @var{0}, the
22286 larger the limit the more bytes @code{heuristic-fence-post} must search
22287 and therefore the longer it takes to run. You should only need to use
22288 this command when debugging a stripped executable.
22290 @item show heuristic-fence-post
22291 Display the current limit.
22295 These commands are available @emph{only} when @value{GDBN} is configured
22296 for debugging programs on Alpha or @acronym{MIPS} processors.
22298 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
22302 @item set mips abi @var{arg}
22303 @kindex set mips abi
22304 @cindex set ABI for @acronym{MIPS}
22305 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
22306 values of @var{arg} are:
22310 The default ABI associated with the current binary (this is the
22320 @item show mips abi
22321 @kindex show mips abi
22322 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
22324 @item set mips compression @var{arg}
22325 @kindex set mips compression
22326 @cindex code compression, @acronym{MIPS}
22327 Tell @value{GDBN} which @acronym{MIPS} compressed
22328 @acronym{ISA, Instruction Set Architecture} encoding is used by the
22329 inferior. @value{GDBN} uses this for code disassembly and other
22330 internal interpretation purposes. This setting is only referred to
22331 when no executable has been associated with the debugging session or
22332 the executable does not provide information about the encoding it uses.
22333 Otherwise this setting is automatically updated from information
22334 provided by the executable.
22336 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
22337 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
22338 executables containing @acronym{MIPS16} code frequently are not
22339 identified as such.
22341 This setting is ``sticky''; that is, it retains its value across
22342 debugging sessions until reset either explicitly with this command or
22343 implicitly from an executable.
22345 The compiler and/or assembler typically add symbol table annotations to
22346 identify functions compiled for the @acronym{MIPS16} or
22347 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
22348 are present, @value{GDBN} uses them in preference to the global
22349 compressed @acronym{ISA} encoding setting.
22351 @item show mips compression
22352 @kindex show mips compression
22353 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
22354 @value{GDBN} to debug the inferior.
22357 @itemx show mipsfpu
22358 @xref{MIPS Embedded, set mipsfpu}.
22360 @item set mips mask-address @var{arg}
22361 @kindex set mips mask-address
22362 @cindex @acronym{MIPS} addresses, masking
22363 This command determines whether the most-significant 32 bits of 64-bit
22364 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
22365 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
22366 setting, which lets @value{GDBN} determine the correct value.
22368 @item show mips mask-address
22369 @kindex show mips mask-address
22370 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
22373 @item set remote-mips64-transfers-32bit-regs
22374 @kindex set remote-mips64-transfers-32bit-regs
22375 This command controls compatibility with 64-bit @acronym{MIPS} targets that
22376 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
22377 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
22378 and 64 bits for other registers, set this option to @samp{on}.
22380 @item show remote-mips64-transfers-32bit-regs
22381 @kindex show remote-mips64-transfers-32bit-regs
22382 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
22384 @item set debug mips
22385 @kindex set debug mips
22386 This command turns on and off debugging messages for the @acronym{MIPS}-specific
22387 target code in @value{GDBN}.
22389 @item show debug mips
22390 @kindex show debug mips
22391 Show the current setting of @acronym{MIPS} debugging messages.
22397 @cindex HPPA support
22399 When @value{GDBN} is debugging the HP PA architecture, it provides the
22400 following special commands:
22403 @item set debug hppa
22404 @kindex set debug hppa
22405 This command determines whether HPPA architecture-specific debugging
22406 messages are to be displayed.
22408 @item show debug hppa
22409 Show whether HPPA debugging messages are displayed.
22411 @item maint print unwind @var{address}
22412 @kindex maint print unwind@r{, HPPA}
22413 This command displays the contents of the unwind table entry at the
22414 given @var{address}.
22420 @subsection Cell Broadband Engine SPU architecture
22421 @cindex Cell Broadband Engine
22424 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
22425 it provides the following special commands:
22428 @item info spu event
22430 Display SPU event facility status. Shows current event mask
22431 and pending event status.
22433 @item info spu signal
22434 Display SPU signal notification facility status. Shows pending
22435 signal-control word and signal notification mode of both signal
22436 notification channels.
22438 @item info spu mailbox
22439 Display SPU mailbox facility status. Shows all pending entries,
22440 in order of processing, in each of the SPU Write Outbound,
22441 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
22444 Display MFC DMA status. Shows all pending commands in the MFC
22445 DMA queue. For each entry, opcode, tag, class IDs, effective
22446 and local store addresses and transfer size are shown.
22448 @item info spu proxydma
22449 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
22450 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
22451 and local store addresses and transfer size are shown.
22455 When @value{GDBN} is debugging a combined PowerPC/SPU application
22456 on the Cell Broadband Engine, it provides in addition the following
22460 @item set spu stop-on-load @var{arg}
22462 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
22463 will give control to the user when a new SPE thread enters its @code{main}
22464 function. The default is @code{off}.
22466 @item show spu stop-on-load
22468 Show whether to stop for new SPE threads.
22470 @item set spu auto-flush-cache @var{arg}
22471 Set whether to automatically flush the software-managed cache. When set to
22472 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
22473 cache to be flushed whenever SPE execution stops. This provides a consistent
22474 view of PowerPC memory that is accessed via the cache. If an application
22475 does not use the software-managed cache, this option has no effect.
22477 @item show spu auto-flush-cache
22478 Show whether to automatically flush the software-managed cache.
22483 @subsection PowerPC
22484 @cindex PowerPC architecture
22486 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
22487 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
22488 numbers stored in the floating point registers. These values must be stored
22489 in two consecutive registers, always starting at an even register like
22490 @code{f0} or @code{f2}.
22492 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
22493 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
22494 @code{f2} and @code{f3} for @code{$dl1} and so on.
22496 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
22497 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
22500 @subsection Nios II
22501 @cindex Nios II architecture
22503 When @value{GDBN} is debugging the Nios II architecture,
22504 it provides the following special commands:
22508 @item set debug nios2
22509 @kindex set debug nios2
22510 This command turns on and off debugging messages for the Nios II
22511 target code in @value{GDBN}.
22513 @item show debug nios2
22514 @kindex show debug nios2
22515 Show the current setting of Nios II debugging messages.
22518 @node Controlling GDB
22519 @chapter Controlling @value{GDBN}
22521 You can alter the way @value{GDBN} interacts with you by using the
22522 @code{set} command. For commands controlling how @value{GDBN} displays
22523 data, see @ref{Print Settings, ,Print Settings}. Other settings are
22528 * Editing:: Command editing
22529 * Command History:: Command history
22530 * Screen Size:: Screen size
22531 * Numbers:: Numbers
22532 * ABI:: Configuring the current ABI
22533 * Auto-loading:: Automatically loading associated files
22534 * Messages/Warnings:: Optional warnings and messages
22535 * Debugging Output:: Optional messages about internal happenings
22536 * Other Misc Settings:: Other Miscellaneous Settings
22544 @value{GDBN} indicates its readiness to read a command by printing a string
22545 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
22546 can change the prompt string with the @code{set prompt} command. For
22547 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
22548 the prompt in one of the @value{GDBN} sessions so that you can always tell
22549 which one you are talking to.
22551 @emph{Note:} @code{set prompt} does not add a space for you after the
22552 prompt you set. This allows you to set a prompt which ends in a space
22553 or a prompt that does not.
22557 @item set prompt @var{newprompt}
22558 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
22560 @kindex show prompt
22562 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
22565 Versions of @value{GDBN} that ship with Python scripting enabled have
22566 prompt extensions. The commands for interacting with these extensions
22570 @kindex set extended-prompt
22571 @item set extended-prompt @var{prompt}
22572 Set an extended prompt that allows for substitutions.
22573 @xref{gdb.prompt}, for a list of escape sequences that can be used for
22574 substitution. Any escape sequences specified as part of the prompt
22575 string are replaced with the corresponding strings each time the prompt
22581 set extended-prompt Current working directory: \w (gdb)
22584 Note that when an extended-prompt is set, it takes control of the
22585 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
22587 @kindex show extended-prompt
22588 @item show extended-prompt
22589 Prints the extended prompt. Any escape sequences specified as part of
22590 the prompt string with @code{set extended-prompt}, are replaced with the
22591 corresponding strings each time the prompt is displayed.
22595 @section Command Editing
22597 @cindex command line editing
22599 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
22600 @sc{gnu} library provides consistent behavior for programs which provide a
22601 command line interface to the user. Advantages are @sc{gnu} Emacs-style
22602 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
22603 substitution, and a storage and recall of command history across
22604 debugging sessions.
22606 You may control the behavior of command line editing in @value{GDBN} with the
22607 command @code{set}.
22610 @kindex set editing
22613 @itemx set editing on
22614 Enable command line editing (enabled by default).
22616 @item set editing off
22617 Disable command line editing.
22619 @kindex show editing
22621 Show whether command line editing is enabled.
22624 @ifset SYSTEM_READLINE
22625 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
22627 @ifclear SYSTEM_READLINE
22628 @xref{Command Line Editing},
22630 for more details about the Readline
22631 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
22632 encouraged to read that chapter.
22634 @node Command History
22635 @section Command History
22636 @cindex command history
22638 @value{GDBN} can keep track of the commands you type during your
22639 debugging sessions, so that you can be certain of precisely what
22640 happened. Use these commands to manage the @value{GDBN} command
22643 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
22644 package, to provide the history facility.
22645 @ifset SYSTEM_READLINE
22646 @xref{Using History Interactively, , , history, GNU History Library},
22648 @ifclear SYSTEM_READLINE
22649 @xref{Using History Interactively},
22651 for the detailed description of the History library.
22653 To issue a command to @value{GDBN} without affecting certain aspects of
22654 the state which is seen by users, prefix it with @samp{server }
22655 (@pxref{Server Prefix}). This
22656 means that this command will not affect the command history, nor will it
22657 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
22658 pressed on a line by itself.
22660 @cindex @code{server}, command prefix
22661 The server prefix does not affect the recording of values into the value
22662 history; to print a value without recording it into the value history,
22663 use the @code{output} command instead of the @code{print} command.
22665 Here is the description of @value{GDBN} commands related to command
22669 @cindex history substitution
22670 @cindex history file
22671 @kindex set history filename
22672 @cindex @env{GDBHISTFILE}, environment variable
22673 @item set history filename @var{fname}
22674 Set the name of the @value{GDBN} command history file to @var{fname}.
22675 This is the file where @value{GDBN} reads an initial command history
22676 list, and where it writes the command history from this session when it
22677 exits. You can access this list through history expansion or through
22678 the history command editing characters listed below. This file defaults
22679 to the value of the environment variable @code{GDBHISTFILE}, or to
22680 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
22683 @cindex save command history
22684 @kindex set history save
22685 @item set history save
22686 @itemx set history save on
22687 Record command history in a file, whose name may be specified with the
22688 @code{set history filename} command. By default, this option is disabled.
22690 @item set history save off
22691 Stop recording command history in a file.
22693 @cindex history size
22694 @kindex set history size
22695 @cindex @env{GDBHISTSIZE}, environment variable
22696 @item set history size @var{size}
22697 @itemx set history size unlimited
22698 Set the number of commands which @value{GDBN} keeps in its history list.
22699 This defaults to the value of the environment variable @env{GDBHISTSIZE}, or
22700 to 256 if this variable is not set. Non-numeric values of @env{GDBHISTSIZE}
22701 are ignored. If @var{size} is @code{unlimited} or if @env{GDBHISTSIZE} is
22702 either a negative number or the empty string, then the number of commands
22703 @value{GDBN} keeps in the history list is unlimited.
22705 @cindex remove duplicate history
22706 @kindex set history remove-duplicates
22707 @item set history remove-duplicates @var{count}
22708 @itemx set history remove-duplicates unlimited
22709 Control the removal of duplicate history entries in the command history list.
22710 If @var{count} is non-zero, @value{GDBN} will look back at the last @var{count}
22711 history entries and remove the first entry that is a duplicate of the current
22712 entry being added to the command history list. If @var{count} is
22713 @code{unlimited} then this lookbehind is unbounded. If @var{count} is 0, then
22714 removal of duplicate history entries is disabled.
22716 Only history entries added during the current session are considered for
22717 removal. This option is set to 0 by default.
22721 History expansion assigns special meaning to the character @kbd{!}.
22722 @ifset SYSTEM_READLINE
22723 @xref{Event Designators, , , history, GNU History Library},
22725 @ifclear SYSTEM_READLINE
22726 @xref{Event Designators},
22730 @cindex history expansion, turn on/off
22731 Since @kbd{!} is also the logical not operator in C, history expansion
22732 is off by default. If you decide to enable history expansion with the
22733 @code{set history expansion on} command, you may sometimes need to
22734 follow @kbd{!} (when it is used as logical not, in an expression) with
22735 a space or a tab to prevent it from being expanded. The readline
22736 history facilities do not attempt substitution on the strings
22737 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
22739 The commands to control history expansion are:
22742 @item set history expansion on
22743 @itemx set history expansion
22744 @kindex set history expansion
22745 Enable history expansion. History expansion is off by default.
22747 @item set history expansion off
22748 Disable history expansion.
22751 @kindex show history
22753 @itemx show history filename
22754 @itemx show history save
22755 @itemx show history size
22756 @itemx show history expansion
22757 These commands display the state of the @value{GDBN} history parameters.
22758 @code{show history} by itself displays all four states.
22763 @kindex show commands
22764 @cindex show last commands
22765 @cindex display command history
22766 @item show commands
22767 Display the last ten commands in the command history.
22769 @item show commands @var{n}
22770 Print ten commands centered on command number @var{n}.
22772 @item show commands +
22773 Print ten commands just after the commands last printed.
22777 @section Screen Size
22778 @cindex size of screen
22779 @cindex screen size
22782 @cindex pauses in output
22784 Certain commands to @value{GDBN} may produce large amounts of
22785 information output to the screen. To help you read all of it,
22786 @value{GDBN} pauses and asks you for input at the end of each page of
22787 output. Type @key{RET} when you want to continue the output, or @kbd{q}
22788 to discard the remaining output. Also, the screen width setting
22789 determines when to wrap lines of output. Depending on what is being
22790 printed, @value{GDBN} tries to break the line at a readable place,
22791 rather than simply letting it overflow onto the following line.
22793 Normally @value{GDBN} knows the size of the screen from the terminal
22794 driver software. For example, on Unix @value{GDBN} uses the termcap data base
22795 together with the value of the @code{TERM} environment variable and the
22796 @code{stty rows} and @code{stty cols} settings. If this is not correct,
22797 you can override it with the @code{set height} and @code{set
22804 @kindex show height
22805 @item set height @var{lpp}
22806 @itemx set height unlimited
22808 @itemx set width @var{cpl}
22809 @itemx set width unlimited
22811 These @code{set} commands specify a screen height of @var{lpp} lines and
22812 a screen width of @var{cpl} characters. The associated @code{show}
22813 commands display the current settings.
22815 If you specify a height of either @code{unlimited} or zero lines,
22816 @value{GDBN} does not pause during output no matter how long the
22817 output is. This is useful if output is to a file or to an editor
22820 Likewise, you can specify @samp{set width unlimited} or @samp{set
22821 width 0} to prevent @value{GDBN} from wrapping its output.
22823 @item set pagination on
22824 @itemx set pagination off
22825 @kindex set pagination
22826 Turn the output pagination on or off; the default is on. Turning
22827 pagination off is the alternative to @code{set height unlimited}. Note that
22828 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
22829 Options, -batch}) also automatically disables pagination.
22831 @item show pagination
22832 @kindex show pagination
22833 Show the current pagination mode.
22838 @cindex number representation
22839 @cindex entering numbers
22841 You can always enter numbers in octal, decimal, or hexadecimal in
22842 @value{GDBN} by the usual conventions: octal numbers begin with
22843 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
22844 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
22845 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
22846 10; likewise, the default display for numbers---when no particular
22847 format is specified---is base 10. You can change the default base for
22848 both input and output with the commands described below.
22851 @kindex set input-radix
22852 @item set input-radix @var{base}
22853 Set the default base for numeric input. Supported choices
22854 for @var{base} are decimal 8, 10, or 16. The base must itself be
22855 specified either unambiguously or using the current input radix; for
22859 set input-radix 012
22860 set input-radix 10.
22861 set input-radix 0xa
22865 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
22866 leaves the input radix unchanged, no matter what it was, since
22867 @samp{10}, being without any leading or trailing signs of its base, is
22868 interpreted in the current radix. Thus, if the current radix is 16,
22869 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
22872 @kindex set output-radix
22873 @item set output-radix @var{base}
22874 Set the default base for numeric display. Supported choices
22875 for @var{base} are decimal 8, 10, or 16. The base must itself be
22876 specified either unambiguously or using the current input radix.
22878 @kindex show input-radix
22879 @item show input-radix
22880 Display the current default base for numeric input.
22882 @kindex show output-radix
22883 @item show output-radix
22884 Display the current default base for numeric display.
22886 @item set radix @r{[}@var{base}@r{]}
22890 These commands set and show the default base for both input and output
22891 of numbers. @code{set radix} sets the radix of input and output to
22892 the same base; without an argument, it resets the radix back to its
22893 default value of 10.
22898 @section Configuring the Current ABI
22900 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
22901 application automatically. However, sometimes you need to override its
22902 conclusions. Use these commands to manage @value{GDBN}'s view of the
22908 @cindex Newlib OS ABI and its influence on the longjmp handling
22910 One @value{GDBN} configuration can debug binaries for multiple operating
22911 system targets, either via remote debugging or native emulation.
22912 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
22913 but you can override its conclusion using the @code{set osabi} command.
22914 One example where this is useful is in debugging of binaries which use
22915 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
22916 not have the same identifying marks that the standard C library for your
22919 When @value{GDBN} is debugging the AArch64 architecture, it provides a
22920 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
22921 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
22922 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
22926 Show the OS ABI currently in use.
22929 With no argument, show the list of registered available OS ABI's.
22931 @item set osabi @var{abi}
22932 Set the current OS ABI to @var{abi}.
22935 @cindex float promotion
22937 Generally, the way that an argument of type @code{float} is passed to a
22938 function depends on whether the function is prototyped. For a prototyped
22939 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
22940 according to the architecture's convention for @code{float}. For unprototyped
22941 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
22942 @code{double} and then passed.
22944 Unfortunately, some forms of debug information do not reliably indicate whether
22945 a function is prototyped. If @value{GDBN} calls a function that is not marked
22946 as prototyped, it consults @kbd{set coerce-float-to-double}.
22949 @kindex set coerce-float-to-double
22950 @item set coerce-float-to-double
22951 @itemx set coerce-float-to-double on
22952 Arguments of type @code{float} will be promoted to @code{double} when passed
22953 to an unprototyped function. This is the default setting.
22955 @item set coerce-float-to-double off
22956 Arguments of type @code{float} will be passed directly to unprototyped
22959 @kindex show coerce-float-to-double
22960 @item show coerce-float-to-double
22961 Show the current setting of promoting @code{float} to @code{double}.
22965 @kindex show cp-abi
22966 @value{GDBN} needs to know the ABI used for your program's C@t{++}
22967 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
22968 used to build your application. @value{GDBN} only fully supports
22969 programs with a single C@t{++} ABI; if your program contains code using
22970 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
22971 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
22972 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
22973 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
22974 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
22975 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
22980 Show the C@t{++} ABI currently in use.
22983 With no argument, show the list of supported C@t{++} ABI's.
22985 @item set cp-abi @var{abi}
22986 @itemx set cp-abi auto
22987 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
22991 @section Automatically loading associated files
22992 @cindex auto-loading
22994 @value{GDBN} sometimes reads files with commands and settings automatically,
22995 without being explicitly told so by the user. We call this feature
22996 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
22997 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
22998 results or introduce security risks (e.g., if the file comes from untrusted
23002 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
23003 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
23005 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
23006 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
23009 There are various kinds of files @value{GDBN} can automatically load.
23010 In addition to these files, @value{GDBN} supports auto-loading code written
23011 in various extension languages. @xref{Auto-loading extensions}.
23013 Note that loading of these associated files (including the local @file{.gdbinit}
23014 file) requires accordingly configured @code{auto-load safe-path}
23015 (@pxref{Auto-loading safe path}).
23017 For these reasons, @value{GDBN} includes commands and options to let you
23018 control when to auto-load files and which files should be auto-loaded.
23021 @anchor{set auto-load off}
23022 @kindex set auto-load off
23023 @item set auto-load off
23024 Globally disable loading of all auto-loaded files.
23025 You may want to use this command with the @samp{-iex} option
23026 (@pxref{Option -init-eval-command}) such as:
23028 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
23031 Be aware that system init file (@pxref{System-wide configuration})
23032 and init files from your home directory (@pxref{Home Directory Init File})
23033 still get read (as they come from generally trusted directories).
23034 To prevent @value{GDBN} from auto-loading even those init files, use the
23035 @option{-nx} option (@pxref{Mode Options}), in addition to
23036 @code{set auto-load no}.
23038 @anchor{show auto-load}
23039 @kindex show auto-load
23040 @item show auto-load
23041 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
23045 (gdb) show auto-load
23046 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
23047 libthread-db: Auto-loading of inferior specific libthread_db is on.
23048 local-gdbinit: Auto-loading of .gdbinit script from current directory
23050 python-scripts: Auto-loading of Python scripts is on.
23051 safe-path: List of directories from which it is safe to auto-load files
23052 is $debugdir:$datadir/auto-load.
23053 scripts-directory: List of directories from which to load auto-loaded scripts
23054 is $debugdir:$datadir/auto-load.
23057 @anchor{info auto-load}
23058 @kindex info auto-load
23059 @item info auto-load
23060 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
23064 (gdb) info auto-load
23067 Yes /home/user/gdb/gdb-gdb.gdb
23068 libthread-db: No auto-loaded libthread-db.
23069 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
23073 Yes /home/user/gdb/gdb-gdb.py
23077 These are @value{GDBN} control commands for the auto-loading:
23079 @multitable @columnfractions .5 .5
23080 @item @xref{set auto-load off}.
23081 @tab Disable auto-loading globally.
23082 @item @xref{show auto-load}.
23083 @tab Show setting of all kinds of files.
23084 @item @xref{info auto-load}.
23085 @tab Show state of all kinds of files.
23086 @item @xref{set auto-load gdb-scripts}.
23087 @tab Control for @value{GDBN} command scripts.
23088 @item @xref{show auto-load gdb-scripts}.
23089 @tab Show setting of @value{GDBN} command scripts.
23090 @item @xref{info auto-load gdb-scripts}.
23091 @tab Show state of @value{GDBN} command scripts.
23092 @item @xref{set auto-load python-scripts}.
23093 @tab Control for @value{GDBN} Python scripts.
23094 @item @xref{show auto-load python-scripts}.
23095 @tab Show setting of @value{GDBN} Python scripts.
23096 @item @xref{info auto-load python-scripts}.
23097 @tab Show state of @value{GDBN} Python scripts.
23098 @item @xref{set auto-load guile-scripts}.
23099 @tab Control for @value{GDBN} Guile scripts.
23100 @item @xref{show auto-load guile-scripts}.
23101 @tab Show setting of @value{GDBN} Guile scripts.
23102 @item @xref{info auto-load guile-scripts}.
23103 @tab Show state of @value{GDBN} Guile scripts.
23104 @item @xref{set auto-load scripts-directory}.
23105 @tab Control for @value{GDBN} auto-loaded scripts location.
23106 @item @xref{show auto-load scripts-directory}.
23107 @tab Show @value{GDBN} auto-loaded scripts location.
23108 @item @xref{add-auto-load-scripts-directory}.
23109 @tab Add directory for auto-loaded scripts location list.
23110 @item @xref{set auto-load local-gdbinit}.
23111 @tab Control for init file in the current directory.
23112 @item @xref{show auto-load local-gdbinit}.
23113 @tab Show setting of init file in the current directory.
23114 @item @xref{info auto-load local-gdbinit}.
23115 @tab Show state of init file in the current directory.
23116 @item @xref{set auto-load libthread-db}.
23117 @tab Control for thread debugging library.
23118 @item @xref{show auto-load libthread-db}.
23119 @tab Show setting of thread debugging library.
23120 @item @xref{info auto-load libthread-db}.
23121 @tab Show state of thread debugging library.
23122 @item @xref{set auto-load safe-path}.
23123 @tab Control directories trusted for automatic loading.
23124 @item @xref{show auto-load safe-path}.
23125 @tab Show directories trusted for automatic loading.
23126 @item @xref{add-auto-load-safe-path}.
23127 @tab Add directory trusted for automatic loading.
23130 @node Init File in the Current Directory
23131 @subsection Automatically loading init file in the current directory
23132 @cindex auto-loading init file in the current directory
23134 By default, @value{GDBN} reads and executes the canned sequences of commands
23135 from init file (if any) in the current working directory,
23136 see @ref{Init File in the Current Directory during Startup}.
23138 Note that loading of this local @file{.gdbinit} file also requires accordingly
23139 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23142 @anchor{set auto-load local-gdbinit}
23143 @kindex set auto-load local-gdbinit
23144 @item set auto-load local-gdbinit [on|off]
23145 Enable or disable the auto-loading of canned sequences of commands
23146 (@pxref{Sequences}) found in init file in the current directory.
23148 @anchor{show auto-load local-gdbinit}
23149 @kindex show auto-load local-gdbinit
23150 @item show auto-load local-gdbinit
23151 Show whether auto-loading of canned sequences of commands from init file in the
23152 current directory is enabled or disabled.
23154 @anchor{info auto-load local-gdbinit}
23155 @kindex info auto-load local-gdbinit
23156 @item info auto-load local-gdbinit
23157 Print whether canned sequences of commands from init file in the
23158 current directory have been auto-loaded.
23161 @node libthread_db.so.1 file
23162 @subsection Automatically loading thread debugging library
23163 @cindex auto-loading libthread_db.so.1
23165 This feature is currently present only on @sc{gnu}/Linux native hosts.
23167 @value{GDBN} reads in some cases thread debugging library from places specific
23168 to the inferior (@pxref{set libthread-db-search-path}).
23170 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
23171 without checking this @samp{set auto-load libthread-db} switch as system
23172 libraries have to be trusted in general. In all other cases of
23173 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
23174 auto-load libthread-db} is enabled before trying to open such thread debugging
23177 Note that loading of this debugging library also requires accordingly configured
23178 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
23181 @anchor{set auto-load libthread-db}
23182 @kindex set auto-load libthread-db
23183 @item set auto-load libthread-db [on|off]
23184 Enable or disable the auto-loading of inferior specific thread debugging library.
23186 @anchor{show auto-load libthread-db}
23187 @kindex show auto-load libthread-db
23188 @item show auto-load libthread-db
23189 Show whether auto-loading of inferior specific thread debugging library is
23190 enabled or disabled.
23192 @anchor{info auto-load libthread-db}
23193 @kindex info auto-load libthread-db
23194 @item info auto-load libthread-db
23195 Print the list of all loaded inferior specific thread debugging libraries and
23196 for each such library print list of inferior @var{pid}s using it.
23199 @node Auto-loading safe path
23200 @subsection Security restriction for auto-loading
23201 @cindex auto-loading safe-path
23203 As the files of inferior can come from untrusted source (such as submitted by
23204 an application user) @value{GDBN} does not always load any files automatically.
23205 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
23206 directories trusted for loading files not explicitly requested by user.
23207 Each directory can also be a shell wildcard pattern.
23209 If the path is not set properly you will see a warning and the file will not
23214 Reading symbols from /home/user/gdb/gdb...done.
23215 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
23216 declined by your `auto-load safe-path' set
23217 to "$debugdir:$datadir/auto-load".
23218 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
23219 declined by your `auto-load safe-path' set
23220 to "$debugdir:$datadir/auto-load".
23224 To instruct @value{GDBN} to go ahead and use the init files anyway,
23225 invoke @value{GDBN} like this:
23228 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
23231 The list of trusted directories is controlled by the following commands:
23234 @anchor{set auto-load safe-path}
23235 @kindex set auto-load safe-path
23236 @item set auto-load safe-path @r{[}@var{directories}@r{]}
23237 Set the list of directories (and their subdirectories) trusted for automatic
23238 loading and execution of scripts. You can also enter a specific trusted file.
23239 Each directory can also be a shell wildcard pattern; wildcards do not match
23240 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
23241 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
23242 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
23243 its default value as specified during @value{GDBN} compilation.
23245 The list of directories uses path separator (@samp{:} on GNU and Unix
23246 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
23247 to the @env{PATH} environment variable.
23249 @anchor{show auto-load safe-path}
23250 @kindex show auto-load safe-path
23251 @item show auto-load safe-path
23252 Show the list of directories trusted for automatic loading and execution of
23255 @anchor{add-auto-load-safe-path}
23256 @kindex add-auto-load-safe-path
23257 @item add-auto-load-safe-path
23258 Add an entry (or list of entries) to the list of directories trusted for
23259 automatic loading and execution of scripts. Multiple entries may be delimited
23260 by the host platform path separator in use.
23263 This variable defaults to what @code{--with-auto-load-dir} has been configured
23264 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
23265 substitution applies the same as for @ref{set auto-load scripts-directory}.
23266 The default @code{set auto-load safe-path} value can be also overriden by
23267 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
23269 Setting this variable to @file{/} disables this security protection,
23270 corresponding @value{GDBN} configuration option is
23271 @option{--without-auto-load-safe-path}.
23272 This variable is supposed to be set to the system directories writable by the
23273 system superuser only. Users can add their source directories in init files in
23274 their home directories (@pxref{Home Directory Init File}). See also deprecated
23275 init file in the current directory
23276 (@pxref{Init File in the Current Directory during Startup}).
23278 To force @value{GDBN} to load the files it declined to load in the previous
23279 example, you could use one of the following ways:
23282 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
23283 Specify this trusted directory (or a file) as additional component of the list.
23284 You have to specify also any existing directories displayed by
23285 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
23287 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
23288 Specify this directory as in the previous case but just for a single
23289 @value{GDBN} session.
23291 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
23292 Disable auto-loading safety for a single @value{GDBN} session.
23293 This assumes all the files you debug during this @value{GDBN} session will come
23294 from trusted sources.
23296 @item @kbd{./configure --without-auto-load-safe-path}
23297 During compilation of @value{GDBN} you may disable any auto-loading safety.
23298 This assumes all the files you will ever debug with this @value{GDBN} come from
23302 On the other hand you can also explicitly forbid automatic files loading which
23303 also suppresses any such warning messages:
23306 @item @kbd{gdb -iex "set auto-load no" @dots{}}
23307 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
23309 @item @file{~/.gdbinit}: @samp{set auto-load no}
23310 Disable auto-loading globally for the user
23311 (@pxref{Home Directory Init File}). While it is improbable, you could also
23312 use system init file instead (@pxref{System-wide configuration}).
23315 This setting applies to the file names as entered by user. If no entry matches
23316 @value{GDBN} tries as a last resort to also resolve all the file names into
23317 their canonical form (typically resolving symbolic links) and compare the
23318 entries again. @value{GDBN} already canonicalizes most of the filenames on its
23319 own before starting the comparison so a canonical form of directories is
23320 recommended to be entered.
23322 @node Auto-loading verbose mode
23323 @subsection Displaying files tried for auto-load
23324 @cindex auto-loading verbose mode
23326 For better visibility of all the file locations where you can place scripts to
23327 be auto-loaded with inferior --- or to protect yourself against accidental
23328 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
23329 all the files attempted to be loaded. Both existing and non-existing files may
23332 For example the list of directories from which it is safe to auto-load files
23333 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
23334 may not be too obvious while setting it up.
23337 (gdb) set debug auto-load on
23338 (gdb) file ~/src/t/true
23339 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
23340 for objfile "/tmp/true".
23341 auto-load: Updating directories of "/usr:/opt".
23342 auto-load: Using directory "/usr".
23343 auto-load: Using directory "/opt".
23344 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
23345 by your `auto-load safe-path' set to "/usr:/opt".
23349 @anchor{set debug auto-load}
23350 @kindex set debug auto-load
23351 @item set debug auto-load [on|off]
23352 Set whether to print the filenames attempted to be auto-loaded.
23354 @anchor{show debug auto-load}
23355 @kindex show debug auto-load
23356 @item show debug auto-load
23357 Show whether printing of the filenames attempted to be auto-loaded is turned
23361 @node Messages/Warnings
23362 @section Optional Warnings and Messages
23364 @cindex verbose operation
23365 @cindex optional warnings
23366 By default, @value{GDBN} is silent about its inner workings. If you are
23367 running on a slow machine, you may want to use the @code{set verbose}
23368 command. This makes @value{GDBN} tell you when it does a lengthy
23369 internal operation, so you will not think it has crashed.
23371 Currently, the messages controlled by @code{set verbose} are those
23372 which announce that the symbol table for a source file is being read;
23373 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
23376 @kindex set verbose
23377 @item set verbose on
23378 Enables @value{GDBN} output of certain informational messages.
23380 @item set verbose off
23381 Disables @value{GDBN} output of certain informational messages.
23383 @kindex show verbose
23385 Displays whether @code{set verbose} is on or off.
23388 By default, if @value{GDBN} encounters bugs in the symbol table of an
23389 object file, it is silent; but if you are debugging a compiler, you may
23390 find this information useful (@pxref{Symbol Errors, ,Errors Reading
23395 @kindex set complaints
23396 @item set complaints @var{limit}
23397 Permits @value{GDBN} to output @var{limit} complaints about each type of
23398 unusual symbols before becoming silent about the problem. Set
23399 @var{limit} to zero to suppress all complaints; set it to a large number
23400 to prevent complaints from being suppressed.
23402 @kindex show complaints
23403 @item show complaints
23404 Displays how many symbol complaints @value{GDBN} is permitted to produce.
23408 @anchor{confirmation requests}
23409 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
23410 lot of stupid questions to confirm certain commands. For example, if
23411 you try to run a program which is already running:
23415 The program being debugged has been started already.
23416 Start it from the beginning? (y or n)
23419 If you are willing to unflinchingly face the consequences of your own
23420 commands, you can disable this ``feature'':
23424 @kindex set confirm
23426 @cindex confirmation
23427 @cindex stupid questions
23428 @item set confirm off
23429 Disables confirmation requests. Note that running @value{GDBN} with
23430 the @option{--batch} option (@pxref{Mode Options, -batch}) also
23431 automatically disables confirmation requests.
23433 @item set confirm on
23434 Enables confirmation requests (the default).
23436 @kindex show confirm
23438 Displays state of confirmation requests.
23442 @cindex command tracing
23443 If you need to debug user-defined commands or sourced files you may find it
23444 useful to enable @dfn{command tracing}. In this mode each command will be
23445 printed as it is executed, prefixed with one or more @samp{+} symbols, the
23446 quantity denoting the call depth of each command.
23449 @kindex set trace-commands
23450 @cindex command scripts, debugging
23451 @item set trace-commands on
23452 Enable command tracing.
23453 @item set trace-commands off
23454 Disable command tracing.
23455 @item show trace-commands
23456 Display the current state of command tracing.
23459 @node Debugging Output
23460 @section Optional Messages about Internal Happenings
23461 @cindex optional debugging messages
23463 @value{GDBN} has commands that enable optional debugging messages from
23464 various @value{GDBN} subsystems; normally these commands are of
23465 interest to @value{GDBN} maintainers, or when reporting a bug. This
23466 section documents those commands.
23469 @kindex set exec-done-display
23470 @item set exec-done-display
23471 Turns on or off the notification of asynchronous commands'
23472 completion. When on, @value{GDBN} will print a message when an
23473 asynchronous command finishes its execution. The default is off.
23474 @kindex show exec-done-display
23475 @item show exec-done-display
23476 Displays the current setting of asynchronous command completion
23479 @cindex ARM AArch64
23480 @item set debug aarch64
23481 Turns on or off display of debugging messages related to ARM AArch64.
23482 The default is off.
23484 @item show debug aarch64
23485 Displays the current state of displaying debugging messages related to
23487 @cindex gdbarch debugging info
23488 @cindex architecture debugging info
23489 @item set debug arch
23490 Turns on or off display of gdbarch debugging info. The default is off
23491 @item show debug arch
23492 Displays the current state of displaying gdbarch debugging info.
23493 @item set debug aix-solib
23494 @cindex AIX shared library debugging
23495 Control display of debugging messages from the AIX shared library
23496 support module. The default is off.
23497 @item show debug aix-thread
23498 Show the current state of displaying AIX shared library debugging messages.
23499 @item set debug aix-thread
23500 @cindex AIX threads
23501 Display debugging messages about inner workings of the AIX thread
23503 @item show debug aix-thread
23504 Show the current state of AIX thread debugging info display.
23505 @item set debug check-physname
23507 Check the results of the ``physname'' computation. When reading DWARF
23508 debugging information for C@t{++}, @value{GDBN} attempts to compute
23509 each entity's name. @value{GDBN} can do this computation in two
23510 different ways, depending on exactly what information is present.
23511 When enabled, this setting causes @value{GDBN} to compute the names
23512 both ways and display any discrepancies.
23513 @item show debug check-physname
23514 Show the current state of ``physname'' checking.
23515 @item set debug coff-pe-read
23516 @cindex COFF/PE exported symbols
23517 Control display of debugging messages related to reading of COFF/PE
23518 exported symbols. The default is off.
23519 @item show debug coff-pe-read
23520 Displays the current state of displaying debugging messages related to
23521 reading of COFF/PE exported symbols.
23522 @item set debug dwarf-die
23524 Dump DWARF DIEs after they are read in.
23525 The value is the number of nesting levels to print.
23526 A value of zero turns off the display.
23527 @item show debug dwarf-die
23528 Show the current state of DWARF DIE debugging.
23529 @item set debug dwarf-line
23530 @cindex DWARF Line Tables
23531 Turns on or off display of debugging messages related to reading
23532 DWARF line tables. The default is 0 (off).
23533 A value of 1 provides basic information.
23534 A value greater than 1 provides more verbose information.
23535 @item show debug dwarf-line
23536 Show the current state of DWARF line table debugging.
23537 @item set debug dwarf-read
23538 @cindex DWARF Reading
23539 Turns on or off display of debugging messages related to reading
23540 DWARF debug info. The default is 0 (off).
23541 A value of 1 provides basic information.
23542 A value greater than 1 provides more verbose information.
23543 @item show debug dwarf-read
23544 Show the current state of DWARF reader debugging.
23545 @item set debug displaced
23546 @cindex displaced stepping debugging info
23547 Turns on or off display of @value{GDBN} debugging info for the
23548 displaced stepping support. The default is off.
23549 @item show debug displaced
23550 Displays the current state of displaying @value{GDBN} debugging info
23551 related to displaced stepping.
23552 @item set debug event
23553 @cindex event debugging info
23554 Turns on or off display of @value{GDBN} event debugging info. The
23556 @item show debug event
23557 Displays the current state of displaying @value{GDBN} event debugging
23559 @item set debug expression
23560 @cindex expression debugging info
23561 Turns on or off display of debugging info about @value{GDBN}
23562 expression parsing. The default is off.
23563 @item show debug expression
23564 Displays the current state of displaying debugging info about
23565 @value{GDBN} expression parsing.
23566 @item set debug frame
23567 @cindex frame debugging info
23568 Turns on or off display of @value{GDBN} frame debugging info. The
23570 @item show debug frame
23571 Displays the current state of displaying @value{GDBN} frame debugging
23573 @item set debug gnu-nat
23574 @cindex @sc{gnu}/Hurd debug messages
23575 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
23576 @item show debug gnu-nat
23577 Show the current state of @sc{gnu}/Hurd debugging messages.
23578 @item set debug infrun
23579 @cindex inferior debugging info
23580 Turns on or off display of @value{GDBN} debugging info for running the inferior.
23581 The default is off. @file{infrun.c} contains GDB's runtime state machine used
23582 for implementing operations such as single-stepping the inferior.
23583 @item show debug infrun
23584 Displays the current state of @value{GDBN} inferior debugging.
23585 @item set debug jit
23586 @cindex just-in-time compilation, debugging messages
23587 Turns on or off debugging messages from JIT debug support.
23588 @item show debug jit
23589 Displays the current state of @value{GDBN} JIT debugging.
23590 @item set debug lin-lwp
23591 @cindex @sc{gnu}/Linux LWP debug messages
23592 @cindex Linux lightweight processes
23593 Turns on or off debugging messages from the Linux LWP debug support.
23594 @item show debug lin-lwp
23595 Show the current state of Linux LWP debugging messages.
23596 @item set debug linux-namespaces
23597 @cindex @sc{gnu}/Linux namespaces debug messages
23598 Turns on or off debugging messages from the Linux namespaces debug support.
23599 @item show debug linux-namespaces
23600 Show the current state of Linux namespaces debugging messages.
23601 @item set debug mach-o
23602 @cindex Mach-O symbols processing
23603 Control display of debugging messages related to Mach-O symbols
23604 processing. The default is off.
23605 @item show debug mach-o
23606 Displays the current state of displaying debugging messages related to
23607 reading of COFF/PE exported symbols.
23608 @item set debug notification
23609 @cindex remote async notification debugging info
23610 Turns on or off debugging messages about remote async notification.
23611 The default is off.
23612 @item show debug notification
23613 Displays the current state of remote async notification debugging messages.
23614 @item set debug observer
23615 @cindex observer debugging info
23616 Turns on or off display of @value{GDBN} observer debugging. This
23617 includes info such as the notification of observable events.
23618 @item show debug observer
23619 Displays the current state of observer debugging.
23620 @item set debug overload
23621 @cindex C@t{++} overload debugging info
23622 Turns on or off display of @value{GDBN} C@t{++} overload debugging
23623 info. This includes info such as ranking of functions, etc. The default
23625 @item show debug overload
23626 Displays the current state of displaying @value{GDBN} C@t{++} overload
23628 @cindex expression parser, debugging info
23629 @cindex debug expression parser
23630 @item set debug parser
23631 Turns on or off the display of expression parser debugging output.
23632 Internally, this sets the @code{yydebug} variable in the expression
23633 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
23634 details. The default is off.
23635 @item show debug parser
23636 Show the current state of expression parser debugging.
23637 @cindex packets, reporting on stdout
23638 @cindex serial connections, debugging
23639 @cindex debug remote protocol
23640 @cindex remote protocol debugging
23641 @cindex display remote packets
23642 @item set debug remote
23643 Turns on or off display of reports on all packets sent back and forth across
23644 the serial line to the remote machine. The info is printed on the
23645 @value{GDBN} standard output stream. The default is off.
23646 @item show debug remote
23647 Displays the state of display of remote packets.
23648 @item set debug serial
23649 Turns on or off display of @value{GDBN} serial debugging info. The
23651 @item show debug serial
23652 Displays the current state of displaying @value{GDBN} serial debugging
23654 @item set debug solib-frv
23655 @cindex FR-V shared-library debugging
23656 Turns on or off debugging messages for FR-V shared-library code.
23657 @item show debug solib-frv
23658 Display the current state of FR-V shared-library code debugging
23660 @item set debug symbol-lookup
23661 @cindex symbol lookup
23662 Turns on or off display of debugging messages related to symbol lookup.
23663 The default is 0 (off).
23664 A value of 1 provides basic information.
23665 A value greater than 1 provides more verbose information.
23666 @item show debug symbol-lookup
23667 Show the current state of symbol lookup debugging messages.
23668 @item set debug symfile
23669 @cindex symbol file functions
23670 Turns on or off display of debugging messages related to symbol file functions.
23671 The default is off. @xref{Files}.
23672 @item show debug symfile
23673 Show the current state of symbol file debugging messages.
23674 @item set debug symtab-create
23675 @cindex symbol table creation
23676 Turns on or off display of debugging messages related to symbol table creation.
23677 The default is 0 (off).
23678 A value of 1 provides basic information.
23679 A value greater than 1 provides more verbose information.
23680 @item show debug symtab-create
23681 Show the current state of symbol table creation debugging.
23682 @item set debug target
23683 @cindex target debugging info
23684 Turns on or off display of @value{GDBN} target debugging info. This info
23685 includes what is going on at the target level of GDB, as it happens. The
23686 default is 0. Set it to 1 to track events, and to 2 to also track the
23687 value of large memory transfers.
23688 @item show debug target
23689 Displays the current state of displaying @value{GDBN} target debugging
23691 @item set debug timestamp
23692 @cindex timestampping debugging info
23693 Turns on or off display of timestamps with @value{GDBN} debugging info.
23694 When enabled, seconds and microseconds are displayed before each debugging
23696 @item show debug timestamp
23697 Displays the current state of displaying timestamps with @value{GDBN}
23699 @item set debug varobj
23700 @cindex variable object debugging info
23701 Turns on or off display of @value{GDBN} variable object debugging
23702 info. The default is off.
23703 @item show debug varobj
23704 Displays the current state of displaying @value{GDBN} variable object
23706 @item set debug xml
23707 @cindex XML parser debugging
23708 Turns on or off debugging messages for built-in XML parsers.
23709 @item show debug xml
23710 Displays the current state of XML debugging messages.
23713 @node Other Misc Settings
23714 @section Other Miscellaneous Settings
23715 @cindex miscellaneous settings
23718 @kindex set interactive-mode
23719 @item set interactive-mode
23720 If @code{on}, forces @value{GDBN} to assume that GDB was started
23721 in a terminal. In practice, this means that @value{GDBN} should wait
23722 for the user to answer queries generated by commands entered at
23723 the command prompt. If @code{off}, forces @value{GDBN} to operate
23724 in the opposite mode, and it uses the default answers to all queries.
23725 If @code{auto} (the default), @value{GDBN} tries to determine whether
23726 its standard input is a terminal, and works in interactive-mode if it
23727 is, non-interactively otherwise.
23729 In the vast majority of cases, the debugger should be able to guess
23730 correctly which mode should be used. But this setting can be useful
23731 in certain specific cases, such as running a MinGW @value{GDBN}
23732 inside a cygwin window.
23734 @kindex show interactive-mode
23735 @item show interactive-mode
23736 Displays whether the debugger is operating in interactive mode or not.
23739 @node Extending GDB
23740 @chapter Extending @value{GDBN}
23741 @cindex extending GDB
23743 @value{GDBN} provides several mechanisms for extension.
23744 @value{GDBN} also provides the ability to automatically load
23745 extensions when it reads a file for debugging. This allows the
23746 user to automatically customize @value{GDBN} for the program
23750 * Sequences:: Canned Sequences of @value{GDBN} Commands
23751 * Python:: Extending @value{GDBN} using Python
23752 * Guile:: Extending @value{GDBN} using Guile
23753 * Auto-loading extensions:: Automatically loading extensions
23754 * Multiple Extension Languages:: Working with multiple extension languages
23755 * Aliases:: Creating new spellings of existing commands
23758 To facilitate the use of extension languages, @value{GDBN} is capable
23759 of evaluating the contents of a file. When doing so, @value{GDBN}
23760 can recognize which extension language is being used by looking at
23761 the filename extension. Files with an unrecognized filename extension
23762 are always treated as a @value{GDBN} Command Files.
23763 @xref{Command Files,, Command files}.
23765 You can control how @value{GDBN} evaluates these files with the following
23769 @kindex set script-extension
23770 @kindex show script-extension
23771 @item set script-extension off
23772 All scripts are always evaluated as @value{GDBN} Command Files.
23774 @item set script-extension soft
23775 The debugger determines the scripting language based on filename
23776 extension. If this scripting language is supported, @value{GDBN}
23777 evaluates the script using that language. Otherwise, it evaluates
23778 the file as a @value{GDBN} Command File.
23780 @item set script-extension strict
23781 The debugger determines the scripting language based on filename
23782 extension, and evaluates the script using that language. If the
23783 language is not supported, then the evaluation fails.
23785 @item show script-extension
23786 Display the current value of the @code{script-extension} option.
23791 @section Canned Sequences of Commands
23793 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
23794 Command Lists}), @value{GDBN} provides two ways to store sequences of
23795 commands for execution as a unit: user-defined commands and command
23799 * Define:: How to define your own commands
23800 * Hooks:: Hooks for user-defined commands
23801 * Command Files:: How to write scripts of commands to be stored in a file
23802 * Output:: Commands for controlled output
23803 * Auto-loading sequences:: Controlling auto-loaded command files
23807 @subsection User-defined Commands
23809 @cindex user-defined command
23810 @cindex arguments, to user-defined commands
23811 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
23812 which you assign a new name as a command. This is done with the
23813 @code{define} command. User commands may accept up to 10 arguments
23814 separated by whitespace. Arguments are accessed within the user command
23815 via @code{$arg0@dots{}$arg9}. A trivial example:
23819 print $arg0 + $arg1 + $arg2
23824 To execute the command use:
23831 This defines the command @code{adder}, which prints the sum of
23832 its three arguments. Note the arguments are text substitutions, so they may
23833 reference variables, use complex expressions, or even perform inferior
23836 @cindex argument count in user-defined commands
23837 @cindex how many arguments (user-defined commands)
23838 In addition, @code{$argc} may be used to find out how many arguments have
23839 been passed. This expands to a number in the range 0@dots{}10.
23844 print $arg0 + $arg1
23847 print $arg0 + $arg1 + $arg2
23855 @item define @var{commandname}
23856 Define a command named @var{commandname}. If there is already a command
23857 by that name, you are asked to confirm that you want to redefine it.
23858 The argument @var{commandname} may be a bare command name consisting of letters,
23859 numbers, dashes, and underscores. It may also start with any predefined
23860 prefix command. For example, @samp{define target my-target} creates
23861 a user-defined @samp{target my-target} command.
23863 The definition of the command is made up of other @value{GDBN} command lines,
23864 which are given following the @code{define} command. The end of these
23865 commands is marked by a line containing @code{end}.
23868 @kindex end@r{ (user-defined commands)}
23869 @item document @var{commandname}
23870 Document the user-defined command @var{commandname}, so that it can be
23871 accessed by @code{help}. The command @var{commandname} must already be
23872 defined. This command reads lines of documentation just as @code{define}
23873 reads the lines of the command definition, ending with @code{end}.
23874 After the @code{document} command is finished, @code{help} on command
23875 @var{commandname} displays the documentation you have written.
23877 You may use the @code{document} command again to change the
23878 documentation of a command. Redefining the command with @code{define}
23879 does not change the documentation.
23881 @kindex dont-repeat
23882 @cindex don't repeat command
23884 Used inside a user-defined command, this tells @value{GDBN} that this
23885 command should not be repeated when the user hits @key{RET}
23886 (@pxref{Command Syntax, repeat last command}).
23888 @kindex help user-defined
23889 @item help user-defined
23890 List all user-defined commands and all python commands defined in class
23891 COMAND_USER. The first line of the documentation or docstring is
23896 @itemx show user @var{commandname}
23897 Display the @value{GDBN} commands used to define @var{commandname} (but
23898 not its documentation). If no @var{commandname} is given, display the
23899 definitions for all user-defined commands.
23900 This does not work for user-defined python commands.
23902 @cindex infinite recursion in user-defined commands
23903 @kindex show max-user-call-depth
23904 @kindex set max-user-call-depth
23905 @item show max-user-call-depth
23906 @itemx set max-user-call-depth
23907 The value of @code{max-user-call-depth} controls how many recursion
23908 levels are allowed in user-defined commands before @value{GDBN} suspects an
23909 infinite recursion and aborts the command.
23910 This does not apply to user-defined python commands.
23913 In addition to the above commands, user-defined commands frequently
23914 use control flow commands, described in @ref{Command Files}.
23916 When user-defined commands are executed, the
23917 commands of the definition are not printed. An error in any command
23918 stops execution of the user-defined command.
23920 If used interactively, commands that would ask for confirmation proceed
23921 without asking when used inside a user-defined command. Many @value{GDBN}
23922 commands that normally print messages to say what they are doing omit the
23923 messages when used in a user-defined command.
23926 @subsection User-defined Command Hooks
23927 @cindex command hooks
23928 @cindex hooks, for commands
23929 @cindex hooks, pre-command
23932 You may define @dfn{hooks}, which are a special kind of user-defined
23933 command. Whenever you run the command @samp{foo}, if the user-defined
23934 command @samp{hook-foo} exists, it is executed (with no arguments)
23935 before that command.
23937 @cindex hooks, post-command
23939 A hook may also be defined which is run after the command you executed.
23940 Whenever you run the command @samp{foo}, if the user-defined command
23941 @samp{hookpost-foo} exists, it is executed (with no arguments) after
23942 that command. Post-execution hooks may exist simultaneously with
23943 pre-execution hooks, for the same command.
23945 It is valid for a hook to call the command which it hooks. If this
23946 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
23948 @c It would be nice if hookpost could be passed a parameter indicating
23949 @c if the command it hooks executed properly or not. FIXME!
23951 @kindex stop@r{, a pseudo-command}
23952 In addition, a pseudo-command, @samp{stop} exists. Defining
23953 (@samp{hook-stop}) makes the associated commands execute every time
23954 execution stops in your program: before breakpoint commands are run,
23955 displays are printed, or the stack frame is printed.
23957 For example, to ignore @code{SIGALRM} signals while
23958 single-stepping, but treat them normally during normal execution,
23963 handle SIGALRM nopass
23967 handle SIGALRM pass
23970 define hook-continue
23971 handle SIGALRM pass
23975 As a further example, to hook at the beginning and end of the @code{echo}
23976 command, and to add extra text to the beginning and end of the message,
23984 define hookpost-echo
23988 (@value{GDBP}) echo Hello World
23989 <<<---Hello World--->>>
23994 You can define a hook for any single-word command in @value{GDBN}, but
23995 not for command aliases; you should define a hook for the basic command
23996 name, e.g.@: @code{backtrace} rather than @code{bt}.
23997 @c FIXME! So how does Joe User discover whether a command is an alias
23999 You can hook a multi-word command by adding @code{hook-} or
24000 @code{hookpost-} to the last word of the command, e.g.@:
24001 @samp{define target hook-remote} to add a hook to @samp{target remote}.
24003 If an error occurs during the execution of your hook, execution of
24004 @value{GDBN} commands stops and @value{GDBN} issues a prompt
24005 (before the command that you actually typed had a chance to run).
24007 If you try to define a hook which does not match any known command, you
24008 get a warning from the @code{define} command.
24010 @node Command Files
24011 @subsection Command Files
24013 @cindex command files
24014 @cindex scripting commands
24015 A command file for @value{GDBN} is a text file made of lines that are
24016 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
24017 also be included. An empty line in a command file does nothing; it
24018 does not mean to repeat the last command, as it would from the
24021 You can request the execution of a command file with the @code{source}
24022 command. Note that the @code{source} command is also used to evaluate
24023 scripts that are not Command Files. The exact behavior can be configured
24024 using the @code{script-extension} setting.
24025 @xref{Extending GDB,, Extending GDB}.
24029 @cindex execute commands from a file
24030 @item source [-s] [-v] @var{filename}
24031 Execute the command file @var{filename}.
24034 The lines in a command file are generally executed sequentially,
24035 unless the order of execution is changed by one of the
24036 @emph{flow-control commands} described below. The commands are not
24037 printed as they are executed. An error in any command terminates
24038 execution of the command file and control is returned to the console.
24040 @value{GDBN} first searches for @var{filename} in the current directory.
24041 If the file is not found there, and @var{filename} does not specify a
24042 directory, then @value{GDBN} also looks for the file on the source search path
24043 (specified with the @samp{directory} command);
24044 except that @file{$cdir} is not searched because the compilation directory
24045 is not relevant to scripts.
24047 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
24048 on the search path even if @var{filename} specifies a directory.
24049 The search is done by appending @var{filename} to each element of the
24050 search path. So, for example, if @var{filename} is @file{mylib/myscript}
24051 and the search path contains @file{/home/user} then @value{GDBN} will
24052 look for the script @file{/home/user/mylib/myscript}.
24053 The search is also done if @var{filename} is an absolute path.
24054 For example, if @var{filename} is @file{/tmp/myscript} and
24055 the search path contains @file{/home/user} then @value{GDBN} will
24056 look for the script @file{/home/user/tmp/myscript}.
24057 For DOS-like systems, if @var{filename} contains a drive specification,
24058 it is stripped before concatenation. For example, if @var{filename} is
24059 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
24060 will look for the script @file{c:/tmp/myscript}.
24062 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
24063 each command as it is executed. The option must be given before
24064 @var{filename}, and is interpreted as part of the filename anywhere else.
24066 Commands that would ask for confirmation if used interactively proceed
24067 without asking when used in a command file. Many @value{GDBN} commands that
24068 normally print messages to say what they are doing omit the messages
24069 when called from command files.
24071 @value{GDBN} also accepts command input from standard input. In this
24072 mode, normal output goes to standard output and error output goes to
24073 standard error. Errors in a command file supplied on standard input do
24074 not terminate execution of the command file---execution continues with
24078 gdb < cmds > log 2>&1
24081 (The syntax above will vary depending on the shell used.) This example
24082 will execute commands from the file @file{cmds}. All output and errors
24083 would be directed to @file{log}.
24085 Since commands stored on command files tend to be more general than
24086 commands typed interactively, they frequently need to deal with
24087 complicated situations, such as different or unexpected values of
24088 variables and symbols, changes in how the program being debugged is
24089 built, etc. @value{GDBN} provides a set of flow-control commands to
24090 deal with these complexities. Using these commands, you can write
24091 complex scripts that loop over data structures, execute commands
24092 conditionally, etc.
24099 This command allows to include in your script conditionally executed
24100 commands. The @code{if} command takes a single argument, which is an
24101 expression to evaluate. It is followed by a series of commands that
24102 are executed only if the expression is true (its value is nonzero).
24103 There can then optionally be an @code{else} line, followed by a series
24104 of commands that are only executed if the expression was false. The
24105 end of the list is marked by a line containing @code{end}.
24109 This command allows to write loops. Its syntax is similar to
24110 @code{if}: the command takes a single argument, which is an expression
24111 to evaluate, and must be followed by the commands to execute, one per
24112 line, terminated by an @code{end}. These commands are called the
24113 @dfn{body} of the loop. The commands in the body of @code{while} are
24114 executed repeatedly as long as the expression evaluates to true.
24118 This command exits the @code{while} loop in whose body it is included.
24119 Execution of the script continues after that @code{while}s @code{end}
24122 @kindex loop_continue
24123 @item loop_continue
24124 This command skips the execution of the rest of the body of commands
24125 in the @code{while} loop in whose body it is included. Execution
24126 branches to the beginning of the @code{while} loop, where it evaluates
24127 the controlling expression.
24129 @kindex end@r{ (if/else/while commands)}
24131 Terminate the block of commands that are the body of @code{if},
24132 @code{else}, or @code{while} flow-control commands.
24137 @subsection Commands for Controlled Output
24139 During the execution of a command file or a user-defined command, normal
24140 @value{GDBN} output is suppressed; the only output that appears is what is
24141 explicitly printed by the commands in the definition. This section
24142 describes three commands useful for generating exactly the output you
24147 @item echo @var{text}
24148 @c I do not consider backslash-space a standard C escape sequence
24149 @c because it is not in ANSI.
24150 Print @var{text}. Nonprinting characters can be included in
24151 @var{text} using C escape sequences, such as @samp{\n} to print a
24152 newline. @strong{No newline is printed unless you specify one.}
24153 In addition to the standard C escape sequences, a backslash followed
24154 by a space stands for a space. This is useful for displaying a
24155 string with spaces at the beginning or the end, since leading and
24156 trailing spaces are otherwise trimmed from all arguments.
24157 To print @samp{@w{ }and foo =@w{ }}, use the command
24158 @samp{echo \@w{ }and foo = \@w{ }}.
24160 A backslash at the end of @var{text} can be used, as in C, to continue
24161 the command onto subsequent lines. For example,
24164 echo This is some text\n\
24165 which is continued\n\
24166 onto several lines.\n
24169 produces the same output as
24172 echo This is some text\n
24173 echo which is continued\n
24174 echo onto several lines.\n
24178 @item output @var{expression}
24179 Print the value of @var{expression} and nothing but that value: no
24180 newlines, no @samp{$@var{nn} = }. The value is not entered in the
24181 value history either. @xref{Expressions, ,Expressions}, for more information
24184 @item output/@var{fmt} @var{expression}
24185 Print the value of @var{expression} in format @var{fmt}. You can use
24186 the same formats as for @code{print}. @xref{Output Formats,,Output
24187 Formats}, for more information.
24190 @item printf @var{template}, @var{expressions}@dots{}
24191 Print the values of one or more @var{expressions} under the control of
24192 the string @var{template}. To print several values, make
24193 @var{expressions} be a comma-separated list of individual expressions,
24194 which may be either numbers or pointers. Their values are printed as
24195 specified by @var{template}, exactly as a C program would do by
24196 executing the code below:
24199 printf (@var{template}, @var{expressions}@dots{});
24202 As in @code{C} @code{printf}, ordinary characters in @var{template}
24203 are printed verbatim, while @dfn{conversion specification} introduced
24204 by the @samp{%} character cause subsequent @var{expressions} to be
24205 evaluated, their values converted and formatted according to type and
24206 style information encoded in the conversion specifications, and then
24209 For example, you can print two values in hex like this:
24212 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
24215 @code{printf} supports all the standard @code{C} conversion
24216 specifications, including the flags and modifiers between the @samp{%}
24217 character and the conversion letter, with the following exceptions:
24221 The argument-ordering modifiers, such as @samp{2$}, are not supported.
24224 The modifier @samp{*} is not supported for specifying precision or
24228 The @samp{'} flag (for separation of digits into groups according to
24229 @code{LC_NUMERIC'}) is not supported.
24232 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
24236 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
24239 The conversion letters @samp{a} and @samp{A} are not supported.
24243 Note that the @samp{ll} type modifier is supported only if the
24244 underlying @code{C} implementation used to build @value{GDBN} supports
24245 the @code{long long int} type, and the @samp{L} type modifier is
24246 supported only if @code{long double} type is available.
24248 As in @code{C}, @code{printf} supports simple backslash-escape
24249 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
24250 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
24251 single character. Octal and hexadecimal escape sequences are not
24254 Additionally, @code{printf} supports conversion specifications for DFP
24255 (@dfn{Decimal Floating Point}) types using the following length modifiers
24256 together with a floating point specifier.
24261 @samp{H} for printing @code{Decimal32} types.
24264 @samp{D} for printing @code{Decimal64} types.
24267 @samp{DD} for printing @code{Decimal128} types.
24270 If the underlying @code{C} implementation used to build @value{GDBN} has
24271 support for the three length modifiers for DFP types, other modifiers
24272 such as width and precision will also be available for @value{GDBN} to use.
24274 In case there is no such @code{C} support, no additional modifiers will be
24275 available and the value will be printed in the standard way.
24277 Here's an example of printing DFP types using the above conversion letters:
24279 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
24283 @item eval @var{template}, @var{expressions}@dots{}
24284 Convert the values of one or more @var{expressions} under the control of
24285 the string @var{template} to a command line, and call it.
24289 @node Auto-loading sequences
24290 @subsection Controlling auto-loading native @value{GDBN} scripts
24291 @cindex native script auto-loading
24293 When a new object file is read (for example, due to the @code{file}
24294 command, or because the inferior has loaded a shared library),
24295 @value{GDBN} will look for the command file @file{@var{objfile}-gdb.gdb}.
24296 @xref{Auto-loading extensions}.
24298 Auto-loading can be enabled or disabled,
24299 and the list of auto-loaded scripts can be printed.
24302 @anchor{set auto-load gdb-scripts}
24303 @kindex set auto-load gdb-scripts
24304 @item set auto-load gdb-scripts [on|off]
24305 Enable or disable the auto-loading of canned sequences of commands scripts.
24307 @anchor{show auto-load gdb-scripts}
24308 @kindex show auto-load gdb-scripts
24309 @item show auto-load gdb-scripts
24310 Show whether auto-loading of canned sequences of commands scripts is enabled or
24313 @anchor{info auto-load gdb-scripts}
24314 @kindex info auto-load gdb-scripts
24315 @cindex print list of auto-loaded canned sequences of commands scripts
24316 @item info auto-load gdb-scripts [@var{regexp}]
24317 Print the list of all canned sequences of commands scripts that @value{GDBN}
24321 If @var{regexp} is supplied only canned sequences of commands scripts with
24322 matching names are printed.
24324 @c Python docs live in a separate file.
24325 @include python.texi
24327 @c Guile docs live in a separate file.
24328 @include guile.texi
24330 @node Auto-loading extensions
24331 @section Auto-loading extensions
24332 @cindex auto-loading extensions
24334 @value{GDBN} provides two mechanisms for automatically loading extensions
24335 when a new object file is read (for example, due to the @code{file}
24336 command, or because the inferior has loaded a shared library):
24337 @file{@var{objfile}-gdb.@var{ext}} and the @code{.debug_gdb_scripts}
24338 section of modern file formats like ELF.
24341 * objfile-gdb.ext file: objfile-gdbdotext file. The @file{@var{objfile}-gdb.@var{ext}} file
24342 * .debug_gdb_scripts section: dotdebug_gdb_scripts section. The @code{.debug_gdb_scripts} section
24343 * Which flavor to choose?::
24346 The auto-loading feature is useful for supplying application-specific
24347 debugging commands and features.
24349 Auto-loading can be enabled or disabled,
24350 and the list of auto-loaded scripts can be printed.
24351 See the @samp{auto-loading} section of each extension language
24352 for more information.
24353 For @value{GDBN} command files see @ref{Auto-loading sequences}.
24354 For Python files see @ref{Python Auto-loading}.
24356 Note that loading of this script file also requires accordingly configured
24357 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24359 @node objfile-gdbdotext file
24360 @subsection The @file{@var{objfile}-gdb.@var{ext}} file
24361 @cindex @file{@var{objfile}-gdb.gdb}
24362 @cindex @file{@var{objfile}-gdb.py}
24363 @cindex @file{@var{objfile}-gdb.scm}
24365 When a new object file is read, @value{GDBN} looks for a file named
24366 @file{@var{objfile}-gdb.@var{ext}} (we call it @var{script-name} below),
24367 where @var{objfile} is the object file's name and
24368 where @var{ext} is the file extension for the extension language:
24371 @item @file{@var{objfile}-gdb.gdb}
24372 GDB's own command language
24373 @item @file{@var{objfile}-gdb.py}
24375 @item @file{@var{objfile}-gdb.scm}
24379 @var{script-name} is formed by ensuring that the file name of @var{objfile}
24380 is absolute, following all symlinks, and resolving @code{.} and @code{..}
24381 components, and appending the @file{-gdb.@var{ext}} suffix.
24382 If this file exists and is readable, @value{GDBN} will evaluate it as a
24383 script in the specified extension language.
24385 If this file does not exist, then @value{GDBN} will look for
24386 @var{script-name} file in all of the directories as specified below.
24388 Note that loading of these files requires an accordingly configured
24389 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24391 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
24392 scripts normally according to its @file{.exe} filename. But if no scripts are
24393 found @value{GDBN} also tries script filenames matching the object file without
24394 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
24395 is attempted on any platform. This makes the script filenames compatible
24396 between Unix and MS-Windows hosts.
24399 @anchor{set auto-load scripts-directory}
24400 @kindex set auto-load scripts-directory
24401 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
24402 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
24403 may be delimited by the host platform path separator in use
24404 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
24406 Each entry here needs to be covered also by the security setting
24407 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
24409 @anchor{with-auto-load-dir}
24410 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
24411 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
24412 configuration option @option{--with-auto-load-dir}.
24414 Any reference to @file{$debugdir} will get replaced by
24415 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
24416 reference to @file{$datadir} will get replaced by @var{data-directory} which is
24417 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
24418 @file{$datadir} must be placed as a directory component --- either alone or
24419 delimited by @file{/} or @file{\} directory separators, depending on the host
24422 The list of directories uses path separator (@samp{:} on GNU and Unix
24423 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
24424 to the @env{PATH} environment variable.
24426 @anchor{show auto-load scripts-directory}
24427 @kindex show auto-load scripts-directory
24428 @item show auto-load scripts-directory
24429 Show @value{GDBN} auto-loaded scripts location.
24431 @anchor{add-auto-load-scripts-directory}
24432 @kindex add-auto-load-scripts-directory
24433 @item add-auto-load-scripts-directory @r{[}@var{directories}@dots{}@r{]}
24434 Add an entry (or list of entries) to the list of auto-loaded scripts locations.
24435 Multiple entries may be delimited by the host platform path separator in use.
24438 @value{GDBN} does not track which files it has already auto-loaded this way.
24439 @value{GDBN} will load the associated script every time the corresponding
24440 @var{objfile} is opened.
24441 So your @file{-gdb.@var{ext}} file should be careful to avoid errors if it
24442 is evaluated more than once.
24444 @node dotdebug_gdb_scripts section
24445 @subsection The @code{.debug_gdb_scripts} section
24446 @cindex @code{.debug_gdb_scripts} section
24448 For systems using file formats like ELF and COFF,
24449 when @value{GDBN} loads a new object file
24450 it will look for a special section named @code{.debug_gdb_scripts}.
24451 If this section exists, its contents is a list of null-terminated entries
24452 specifying scripts to load. Each entry begins with a non-null prefix byte that
24453 specifies the kind of entry, typically the extension language and whether the
24454 script is in a file or inlined in @code{.debug_gdb_scripts}.
24456 The following entries are supported:
24459 @item SECTION_SCRIPT_ID_PYTHON_FILE = 1
24460 @item SECTION_SCRIPT_ID_SCHEME_FILE = 3
24461 @item SECTION_SCRIPT_ID_PYTHON_TEXT = 4
24462 @item SECTION_SCRIPT_ID_SCHEME_TEXT = 6
24465 @subsubsection Script File Entries
24467 If the entry specifies a file, @value{GDBN} will look for the file first
24468 in the current directory and then along the source search path
24469 (@pxref{Source Path, ,Specifying Source Directories}),
24470 except that @file{$cdir} is not searched, since the compilation
24471 directory is not relevant to scripts.
24473 File entries can be placed in section @code{.debug_gdb_scripts} with,
24474 for example, this GCC macro for Python scripts.
24477 /* Note: The "MS" section flags are to remove duplicates. */
24478 #define DEFINE_GDB_PY_SCRIPT(script_name) \
24480 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24481 .byte 1 /* Python */\n\
24482 .asciz \"" script_name "\"\n\
24488 For Guile scripts, replace @code{.byte 1} with @code{.byte 3}.
24489 Then one can reference the macro in a header or source file like this:
24492 DEFINE_GDB_PY_SCRIPT ("my-app-scripts.py")
24495 The script name may include directories if desired.
24497 Note that loading of this script file also requires accordingly configured
24498 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24500 If the macro invocation is put in a header, any application or library
24501 using this header will get a reference to the specified script,
24502 and with the use of @code{"MS"} attributes on the section, the linker
24503 will remove duplicates.
24505 @subsubsection Script Text Entries
24507 Script text entries allow to put the executable script in the entry
24508 itself instead of loading it from a file.
24509 The first line of the entry, everything after the prefix byte and up to
24510 the first newline (@code{0xa}) character, is the script name, and must not
24511 contain any kind of space character, e.g., spaces or tabs.
24512 The rest of the entry, up to the trailing null byte, is the script to
24513 execute in the specified language. The name needs to be unique among
24514 all script names, as @value{GDBN} executes each script only once based
24517 Here is an example from file @file{py-section-script.c} in the @value{GDBN}
24521 #include "symcat.h"
24522 #include "gdb/section-scripts.h"
24524 ".pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n"
24525 ".byte " XSTRING (SECTION_SCRIPT_ID_PYTHON_TEXT) "\n"
24526 ".ascii \"gdb.inlined-script\\n\"\n"
24527 ".ascii \"class test_cmd (gdb.Command):\\n\"\n"
24528 ".ascii \" def __init__ (self):\\n\"\n"
24529 ".ascii \" super (test_cmd, self).__init__ ("
24530 "\\\"test-cmd\\\", gdb.COMMAND_OBSCURE)\\n\"\n"
24531 ".ascii \" def invoke (self, arg, from_tty):\\n\"\n"
24532 ".ascii \" print (\\\"test-cmd output, arg = %s\\\" % arg)\\n\"\n"
24533 ".ascii \"test_cmd ()\\n\"\n"
24539 Loading of inlined scripts requires a properly configured
24540 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
24541 The path to specify in @code{auto-load safe-path} is the path of the file
24542 containing the @code{.debug_gdb_scripts} section.
24544 @node Which flavor to choose?
24545 @subsection Which flavor to choose?
24547 Given the multiple ways of auto-loading extensions, it might not always
24548 be clear which one to choose. This section provides some guidance.
24551 Benefits of the @file{-gdb.@var{ext}} way:
24555 Can be used with file formats that don't support multiple sections.
24558 Ease of finding scripts for public libraries.
24560 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24561 in the source search path.
24562 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24563 isn't a source directory in which to find the script.
24566 Doesn't require source code additions.
24570 Benefits of the @code{.debug_gdb_scripts} way:
24574 Works with static linking.
24576 Scripts for libraries done the @file{-gdb.@var{ext}} way require an objfile to
24577 trigger their loading. When an application is statically linked the only
24578 objfile available is the executable, and it is cumbersome to attach all the
24579 scripts from all the input libraries to the executable's
24580 @file{-gdb.@var{ext}} script.
24583 Works with classes that are entirely inlined.
24585 Some classes can be entirely inlined, and thus there may not be an associated
24586 shared library to attach a @file{-gdb.@var{ext}} script to.
24589 Scripts needn't be copied out of the source tree.
24591 In some circumstances, apps can be built out of large collections of internal
24592 libraries, and the build infrastructure necessary to install the
24593 @file{-gdb.@var{ext}} scripts in a place where @value{GDBN} can find them is
24594 cumbersome. It may be easier to specify the scripts in the
24595 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24596 top of the source tree to the source search path.
24599 @node Multiple Extension Languages
24600 @section Multiple Extension Languages
24602 The Guile and Python extension languages do not share any state,
24603 and generally do not interfere with each other.
24604 There are some things to be aware of, however.
24606 @subsection Python comes first
24608 Python was @value{GDBN}'s first extension language, and to avoid breaking
24609 existing behaviour Python comes first. This is generally solved by the
24610 ``first one wins'' principle. @value{GDBN} maintains a list of enabled
24611 extension languages, and when it makes a call to an extension language,
24612 (say to pretty-print a value), it tries each in turn until an extension
24613 language indicates it has performed the request (e.g., has returned the
24614 pretty-printed form of a value).
24615 This extends to errors while performing such requests: If an error happens
24616 while, for example, trying to pretty-print an object then the error is
24617 reported and any following extension languages are not tried.
24620 @section Creating new spellings of existing commands
24621 @cindex aliases for commands
24623 It is often useful to define alternate spellings of existing commands.
24624 For example, if a new @value{GDBN} command defined in Python has
24625 a long name to type, it is handy to have an abbreviated version of it
24626 that involves less typing.
24628 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24629 of the @samp{step} command even though it is otherwise an ambiguous
24630 abbreviation of other commands like @samp{set} and @samp{show}.
24632 Aliases are also used to provide shortened or more common versions
24633 of multi-word commands. For example, @value{GDBN} provides the
24634 @samp{tty} alias of the @samp{set inferior-tty} command.
24636 You can define a new alias with the @samp{alias} command.
24641 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24645 @var{ALIAS} specifies the name of the new alias.
24646 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24649 @var{COMMAND} specifies the name of an existing command
24650 that is being aliased.
24652 The @samp{-a} option specifies that the new alias is an abbreviation
24653 of the command. Abbreviations are not shown in command
24654 lists displayed by the @samp{help} command.
24656 The @samp{--} option specifies the end of options,
24657 and is useful when @var{ALIAS} begins with a dash.
24659 Here is a simple example showing how to make an abbreviation
24660 of a command so that there is less to type.
24661 Suppose you were tired of typing @samp{disas}, the current
24662 shortest unambiguous abbreviation of the @samp{disassemble} command
24663 and you wanted an even shorter version named @samp{di}.
24664 The following will accomplish this.
24667 (gdb) alias -a di = disas
24670 Note that aliases are different from user-defined commands.
24671 With a user-defined command, you also need to write documentation
24672 for it with the @samp{document} command.
24673 An alias automatically picks up the documentation of the existing command.
24675 Here is an example where we make @samp{elms} an abbreviation of
24676 @samp{elements} in the @samp{set print elements} command.
24677 This is to show that you can make an abbreviation of any part
24681 (gdb) alias -a set print elms = set print elements
24682 (gdb) alias -a show print elms = show print elements
24683 (gdb) set p elms 20
24685 Limit on string chars or array elements to print is 200.
24688 Note that if you are defining an alias of a @samp{set} command,
24689 and you want to have an alias for the corresponding @samp{show}
24690 command, then you need to define the latter separately.
24692 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24693 @var{ALIAS}, just as they are normally.
24696 (gdb) alias -a set pr elms = set p ele
24699 Finally, here is an example showing the creation of a one word
24700 alias for a more complex command.
24701 This creates alias @samp{spe} of the command @samp{set print elements}.
24704 (gdb) alias spe = set print elements
24709 @chapter Command Interpreters
24710 @cindex command interpreters
24712 @value{GDBN} supports multiple command interpreters, and some command
24713 infrastructure to allow users or user interface writers to switch
24714 between interpreters or run commands in other interpreters.
24716 @value{GDBN} currently supports two command interpreters, the console
24717 interpreter (sometimes called the command-line interpreter or @sc{cli})
24718 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24719 describes both of these interfaces in great detail.
24721 By default, @value{GDBN} will start with the console interpreter.
24722 However, the user may choose to start @value{GDBN} with another
24723 interpreter by specifying the @option{-i} or @option{--interpreter}
24724 startup options. Defined interpreters include:
24728 @cindex console interpreter
24729 The traditional console or command-line interpreter. This is the most often
24730 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24731 @value{GDBN} will use this interpreter.
24734 @cindex mi interpreter
24735 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24736 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24737 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24741 @cindex mi2 interpreter
24742 The current @sc{gdb/mi} interface.
24745 @cindex mi1 interpreter
24746 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24750 @cindex invoke another interpreter
24751 The interpreter being used by @value{GDBN} may not be dynamically
24752 switched at runtime. Although possible, this could lead to a very
24753 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24754 enters the command "interpreter-set console" in a console view,
24755 @value{GDBN} would switch to using the console interpreter, rendering
24756 the IDE inoperable!
24758 @kindex interpreter-exec
24759 Although you may only choose a single interpreter at startup, you may execute
24760 commands in any interpreter from the current interpreter using the appropriate
24761 command. If you are running the console interpreter, simply use the
24762 @code{interpreter-exec} command:
24765 interpreter-exec mi "-data-list-register-names"
24768 @sc{gdb/mi} has a similar command, although it is only available in versions of
24769 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24772 @chapter @value{GDBN} Text User Interface
24774 @cindex Text User Interface
24777 * TUI Overview:: TUI overview
24778 * TUI Keys:: TUI key bindings
24779 * TUI Single Key Mode:: TUI single key mode
24780 * TUI Commands:: TUI-specific commands
24781 * TUI Configuration:: TUI configuration variables
24784 The @value{GDBN} Text User Interface (TUI) is a terminal
24785 interface which uses the @code{curses} library to show the source
24786 file, the assembly output, the program registers and @value{GDBN}
24787 commands in separate text windows. The TUI mode is supported only
24788 on platforms where a suitable version of the @code{curses} library
24791 The TUI mode is enabled by default when you invoke @value{GDBN} as
24792 @samp{@value{GDBP} -tui}.
24793 You can also switch in and out of TUI mode while @value{GDBN} runs by
24794 using various TUI commands and key bindings, such as @command{tui
24795 enable} or @kbd{C-x C-a}. @xref{TUI Commands, ,TUI Commands}, and
24796 @ref{TUI Keys, ,TUI Key Bindings}.
24799 @section TUI Overview
24801 In TUI mode, @value{GDBN} can display several text windows:
24805 This window is the @value{GDBN} command window with the @value{GDBN}
24806 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24807 managed using readline.
24810 The source window shows the source file of the program. The current
24811 line and active breakpoints are displayed in this window.
24814 The assembly window shows the disassembly output of the program.
24817 This window shows the processor registers. Registers are highlighted
24818 when their values change.
24821 The source and assembly windows show the current program position
24822 by highlighting the current line and marking it with a @samp{>} marker.
24823 Breakpoints are indicated with two markers. The first marker
24824 indicates the breakpoint type:
24828 Breakpoint which was hit at least once.
24831 Breakpoint which was never hit.
24834 Hardware breakpoint which was hit at least once.
24837 Hardware breakpoint which was never hit.
24840 The second marker indicates whether the breakpoint is enabled or not:
24844 Breakpoint is enabled.
24847 Breakpoint is disabled.
24850 The source, assembly and register windows are updated when the current
24851 thread changes, when the frame changes, or when the program counter
24854 These windows are not all visible at the same time. The command
24855 window is always visible. The others can be arranged in several
24866 source and assembly,
24869 source and registers, or
24872 assembly and registers.
24875 A status line above the command window shows the following information:
24879 Indicates the current @value{GDBN} target.
24880 (@pxref{Targets, ,Specifying a Debugging Target}).
24883 Gives the current process or thread number.
24884 When no process is being debugged, this field is set to @code{No process}.
24887 Gives the current function name for the selected frame.
24888 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24889 When there is no symbol corresponding to the current program counter,
24890 the string @code{??} is displayed.
24893 Indicates the current line number for the selected frame.
24894 When the current line number is not known, the string @code{??} is displayed.
24897 Indicates the current program counter address.
24901 @section TUI Key Bindings
24902 @cindex TUI key bindings
24904 The TUI installs several key bindings in the readline keymaps
24905 @ifset SYSTEM_READLINE
24906 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24908 @ifclear SYSTEM_READLINE
24909 (@pxref{Command Line Editing}).
24911 The following key bindings are installed for both TUI mode and the
24912 @value{GDBN} standard mode.
24921 Enter or leave the TUI mode. When leaving the TUI mode,
24922 the curses window management stops and @value{GDBN} operates using
24923 its standard mode, writing on the terminal directly. When reentering
24924 the TUI mode, control is given back to the curses windows.
24925 The screen is then refreshed.
24929 Use a TUI layout with only one window. The layout will
24930 either be @samp{source} or @samp{assembly}. When the TUI mode
24931 is not active, it will switch to the TUI mode.
24933 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24937 Use a TUI layout with at least two windows. When the current
24938 layout already has two windows, the next layout with two windows is used.
24939 When a new layout is chosen, one window will always be common to the
24940 previous layout and the new one.
24942 Think of it as the Emacs @kbd{C-x 2} binding.
24946 Change the active window. The TUI associates several key bindings
24947 (like scrolling and arrow keys) with the active window. This command
24948 gives the focus to the next TUI window.
24950 Think of it as the Emacs @kbd{C-x o} binding.
24954 Switch in and out of the TUI SingleKey mode that binds single
24955 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24958 The following key bindings only work in the TUI mode:
24963 Scroll the active window one page up.
24967 Scroll the active window one page down.
24971 Scroll the active window one line up.
24975 Scroll the active window one line down.
24979 Scroll the active window one column left.
24983 Scroll the active window one column right.
24987 Refresh the screen.
24990 Because the arrow keys scroll the active window in the TUI mode, they
24991 are not available for their normal use by readline unless the command
24992 window has the focus. When another window is active, you must use
24993 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24994 and @kbd{C-f} to control the command window.
24996 @node TUI Single Key Mode
24997 @section TUI Single Key Mode
24998 @cindex TUI single key mode
25000 The TUI also provides a @dfn{SingleKey} mode, which binds several
25001 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25002 switch into this mode, where the following key bindings are used:
25005 @kindex c @r{(SingleKey TUI key)}
25009 @kindex d @r{(SingleKey TUI key)}
25013 @kindex f @r{(SingleKey TUI key)}
25017 @kindex n @r{(SingleKey TUI key)}
25021 @kindex q @r{(SingleKey TUI key)}
25023 exit the SingleKey mode.
25025 @kindex r @r{(SingleKey TUI key)}
25029 @kindex s @r{(SingleKey TUI key)}
25033 @kindex u @r{(SingleKey TUI key)}
25037 @kindex v @r{(SingleKey TUI key)}
25041 @kindex w @r{(SingleKey TUI key)}
25046 Other keys temporarily switch to the @value{GDBN} command prompt.
25047 The key that was pressed is inserted in the editing buffer so that
25048 it is possible to type most @value{GDBN} commands without interaction
25049 with the TUI SingleKey mode. Once the command is entered the TUI
25050 SingleKey mode is restored. The only way to permanently leave
25051 this mode is by typing @kbd{q} or @kbd{C-x s}.
25055 @section TUI-specific Commands
25056 @cindex TUI commands
25058 The TUI has specific commands to control the text windows.
25059 These commands are always available, even when @value{GDBN} is not in
25060 the TUI mode. When @value{GDBN} is in the standard mode, most
25061 of these commands will automatically switch to the TUI mode.
25063 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25064 terminal, or @value{GDBN} has been started with the machine interface
25065 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25066 these commands will fail with an error, because it would not be
25067 possible or desirable to enable curses window management.
25072 Activate TUI mode. The last active TUI window layout will be used if
25073 TUI mode has prevsiouly been used in the current debugging session,
25074 otherwise a default layout is used.
25077 @kindex tui disable
25078 Disable TUI mode, returning to the console interpreter.
25082 List and give the size of all displayed windows.
25084 @item layout @var{name}
25086 Changes which TUI windows are displayed. In each layout the command
25087 window is always displayed, the @var{name} parameter controls which
25088 additional windows are displayed, and can be any of the following:
25092 Display the next layout.
25095 Display the previous layout.
25098 Display the source and command windows.
25101 Display the assembly and command windows.
25104 Display the source, assembly, and command windows.
25107 When in @code{src} layout display the register, source, and command
25108 windows. When in @code{asm} or @code{split} layout display the
25109 register, assembler, and command windows.
25112 @item focus @var{name}
25114 Changes which TUI window is currently active for scrolling. The
25115 @var{name} parameter can be any of the following:
25119 Make the next window active for scrolling.
25122 Make the previous window active for scrolling.
25125 Make the source window active for scrolling.
25128 Make the assembly window active for scrolling.
25131 Make the register window active for scrolling.
25134 Make the command window active for scrolling.
25139 Refresh the screen. This is similar to typing @kbd{C-L}.
25141 @item tui reg @var{group}
25143 Changes the register group displayed in the tui register window to
25144 @var{group}. If the register window is not currently displayed this
25145 command will cause the register window to be displayed. The list of
25146 register groups, as well as their order is target specific. The
25147 following groups are available on most targets:
25150 Repeatedly selecting this group will cause the display to cycle
25151 through all of the available register groups.
25154 Repeatedly selecting this group will cause the display to cycle
25155 through all of the available register groups in the reverse order to
25159 Display the general registers.
25161 Display the floating point registers.
25163 Display the system registers.
25165 Display the vector registers.
25167 Display all registers.
25172 Update the source window and the current execution point.
25174 @item winheight @var{name} +@var{count}
25175 @itemx winheight @var{name} -@var{count}
25177 Change the height of the window @var{name} by @var{count}
25178 lines. Positive counts increase the height, while negative counts
25179 decrease it. The @var{name} parameter can be one of @code{src} (the
25180 source window), @code{cmd} (the command window), @code{asm} (the
25181 disassembly window), or @code{regs} (the register display window).
25183 @item tabset @var{nchars}
25185 Set the width of tab stops to be @var{nchars} characters. This
25186 setting affects the display of TAB characters in the source and
25190 @node TUI Configuration
25191 @section TUI Configuration Variables
25192 @cindex TUI configuration variables
25194 Several configuration variables control the appearance of TUI windows.
25197 @item set tui border-kind @var{kind}
25198 @kindex set tui border-kind
25199 Select the border appearance for the source, assembly and register windows.
25200 The possible values are the following:
25203 Use a space character to draw the border.
25206 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25209 Use the Alternate Character Set to draw the border. The border is
25210 drawn using character line graphics if the terminal supports them.
25213 @item set tui border-mode @var{mode}
25214 @kindex set tui border-mode
25215 @itemx set tui active-border-mode @var{mode}
25216 @kindex set tui active-border-mode
25217 Select the display attributes for the borders of the inactive windows
25218 or the active window. The @var{mode} can be one of the following:
25221 Use normal attributes to display the border.
25227 Use reverse video mode.
25230 Use half bright mode.
25232 @item half-standout
25233 Use half bright and standout mode.
25236 Use extra bright or bold mode.
25238 @item bold-standout
25239 Use extra bright or bold and standout mode.
25244 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25247 @cindex @sc{gnu} Emacs
25248 A special interface allows you to use @sc{gnu} Emacs to view (and
25249 edit) the source files for the program you are debugging with
25252 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25253 executable file you want to debug as an argument. This command starts
25254 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25255 created Emacs buffer.
25256 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25258 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25263 All ``terminal'' input and output goes through an Emacs buffer, called
25266 This applies both to @value{GDBN} commands and their output, and to the input
25267 and output done by the program you are debugging.
25269 This is useful because it means that you can copy the text of previous
25270 commands and input them again; you can even use parts of the output
25273 All the facilities of Emacs' Shell mode are available for interacting
25274 with your program. In particular, you can send signals the usual
25275 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25279 @value{GDBN} displays source code through Emacs.
25281 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25282 source file for that frame and puts an arrow (@samp{=>}) at the
25283 left margin of the current line. Emacs uses a separate buffer for
25284 source display, and splits the screen to show both your @value{GDBN} session
25287 Explicit @value{GDBN} @code{list} or search commands still produce output as
25288 usual, but you probably have no reason to use them from Emacs.
25291 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25292 a graphical mode, enabled by default, which provides further buffers
25293 that can control the execution and describe the state of your program.
25294 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25296 If you specify an absolute file name when prompted for the @kbd{M-x
25297 gdb} argument, then Emacs sets your current working directory to where
25298 your program resides. If you only specify the file name, then Emacs
25299 sets your current working directory to the directory associated
25300 with the previous buffer. In this case, @value{GDBN} may find your
25301 program by searching your environment's @code{PATH} variable, but on
25302 some operating systems it might not find the source. So, although the
25303 @value{GDBN} input and output session proceeds normally, the auxiliary
25304 buffer does not display the current source and line of execution.
25306 The initial working directory of @value{GDBN} is printed on the top
25307 line of the GUD buffer and this serves as a default for the commands
25308 that specify files for @value{GDBN} to operate on. @xref{Files,
25309 ,Commands to Specify Files}.
25311 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25312 need to call @value{GDBN} by a different name (for example, if you
25313 keep several configurations around, with different names) you can
25314 customize the Emacs variable @code{gud-gdb-command-name} to run the
25317 In the GUD buffer, you can use these special Emacs commands in
25318 addition to the standard Shell mode commands:
25322 Describe the features of Emacs' GUD Mode.
25325 Execute to another source line, like the @value{GDBN} @code{step} command; also
25326 update the display window to show the current file and location.
25329 Execute to next source line in this function, skipping all function
25330 calls, like the @value{GDBN} @code{next} command. Then update the display window
25331 to show the current file and location.
25334 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25335 display window accordingly.
25338 Execute until exit from the selected stack frame, like the @value{GDBN}
25339 @code{finish} command.
25342 Continue execution of your program, like the @value{GDBN} @code{continue}
25346 Go up the number of frames indicated by the numeric argument
25347 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25348 like the @value{GDBN} @code{up} command.
25351 Go down the number of frames indicated by the numeric argument, like the
25352 @value{GDBN} @code{down} command.
25355 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25356 tells @value{GDBN} to set a breakpoint on the source line point is on.
25358 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25359 separate frame which shows a backtrace when the GUD buffer is current.
25360 Move point to any frame in the stack and type @key{RET} to make it
25361 become the current frame and display the associated source in the
25362 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25363 selected frame become the current one. In graphical mode, the
25364 speedbar displays watch expressions.
25366 If you accidentally delete the source-display buffer, an easy way to get
25367 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25368 request a frame display; when you run under Emacs, this recreates
25369 the source buffer if necessary to show you the context of the current
25372 The source files displayed in Emacs are in ordinary Emacs buffers
25373 which are visiting the source files in the usual way. You can edit
25374 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25375 communicates with Emacs in terms of line numbers. If you add or
25376 delete lines from the text, the line numbers that @value{GDBN} knows cease
25377 to correspond properly with the code.
25379 A more detailed description of Emacs' interaction with @value{GDBN} is
25380 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25384 @chapter The @sc{gdb/mi} Interface
25386 @unnumberedsec Function and Purpose
25388 @cindex @sc{gdb/mi}, its purpose
25389 @sc{gdb/mi} is a line based machine oriented text interface to
25390 @value{GDBN} and is activated by specifying using the
25391 @option{--interpreter} command line option (@pxref{Mode Options}). It
25392 is specifically intended to support the development of systems which
25393 use the debugger as just one small component of a larger system.
25395 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25396 in the form of a reference manual.
25398 Note that @sc{gdb/mi} is still under construction, so some of the
25399 features described below are incomplete and subject to change
25400 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25402 @unnumberedsec Notation and Terminology
25404 @cindex notational conventions, for @sc{gdb/mi}
25405 This chapter uses the following notation:
25409 @code{|} separates two alternatives.
25412 @code{[ @var{something} ]} indicates that @var{something} is optional:
25413 it may or may not be given.
25416 @code{( @var{group} )*} means that @var{group} inside the parentheses
25417 may repeat zero or more times.
25420 @code{( @var{group} )+} means that @var{group} inside the parentheses
25421 may repeat one or more times.
25424 @code{"@var{string}"} means a literal @var{string}.
25428 @heading Dependencies
25432 * GDB/MI General Design::
25433 * GDB/MI Command Syntax::
25434 * GDB/MI Compatibility with CLI::
25435 * GDB/MI Development and Front Ends::
25436 * GDB/MI Output Records::
25437 * GDB/MI Simple Examples::
25438 * GDB/MI Command Description Format::
25439 * GDB/MI Breakpoint Commands::
25440 * GDB/MI Catchpoint Commands::
25441 * GDB/MI Program Context::
25442 * GDB/MI Thread Commands::
25443 * GDB/MI Ada Tasking Commands::
25444 * GDB/MI Program Execution::
25445 * GDB/MI Stack Manipulation::
25446 * GDB/MI Variable Objects::
25447 * GDB/MI Data Manipulation::
25448 * GDB/MI Tracepoint Commands::
25449 * GDB/MI Symbol Query::
25450 * GDB/MI File Commands::
25452 * GDB/MI Kod Commands::
25453 * GDB/MI Memory Overlay Commands::
25454 * GDB/MI Signal Handling Commands::
25456 * GDB/MI Target Manipulation::
25457 * GDB/MI File Transfer Commands::
25458 * GDB/MI Ada Exceptions Commands::
25459 * GDB/MI Support Commands::
25460 * GDB/MI Miscellaneous Commands::
25463 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25464 @node GDB/MI General Design
25465 @section @sc{gdb/mi} General Design
25466 @cindex GDB/MI General Design
25468 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25469 parts---commands sent to @value{GDBN}, responses to those commands
25470 and notifications. Each command results in exactly one response,
25471 indicating either successful completion of the command, or an error.
25472 For the commands that do not resume the target, the response contains the
25473 requested information. For the commands that resume the target, the
25474 response only indicates whether the target was successfully resumed.
25475 Notifications is the mechanism for reporting changes in the state of the
25476 target, or in @value{GDBN} state, that cannot conveniently be associated with
25477 a command and reported as part of that command response.
25479 The important examples of notifications are:
25483 Exec notifications. These are used to report changes in
25484 target state---when a target is resumed, or stopped. It would not
25485 be feasible to include this information in response of resuming
25486 commands, because one resume commands can result in multiple events in
25487 different threads. Also, quite some time may pass before any event
25488 happens in the target, while a frontend needs to know whether the resuming
25489 command itself was successfully executed.
25492 Console output, and status notifications. Console output
25493 notifications are used to report output of CLI commands, as well as
25494 diagnostics for other commands. Status notifications are used to
25495 report the progress of a long-running operation. Naturally, including
25496 this information in command response would mean no output is produced
25497 until the command is finished, which is undesirable.
25500 General notifications. Commands may have various side effects on
25501 the @value{GDBN} or target state beyond their official purpose. For example,
25502 a command may change the selected thread. Although such changes can
25503 be included in command response, using notification allows for more
25504 orthogonal frontend design.
25508 There's no guarantee that whenever an MI command reports an error,
25509 @value{GDBN} or the target are in any specific state, and especially,
25510 the state is not reverted to the state before the MI command was
25511 processed. Therefore, whenever an MI command results in an error,
25512 we recommend that the frontend refreshes all the information shown in
25513 the user interface.
25517 * Context management::
25518 * Asynchronous and non-stop modes::
25522 @node Context management
25523 @subsection Context management
25525 @subsubsection Threads and Frames
25527 In most cases when @value{GDBN} accesses the target, this access is
25528 done in context of a specific thread and frame (@pxref{Frames}).
25529 Often, even when accessing global data, the target requires that a thread
25530 be specified. The CLI interface maintains the selected thread and frame,
25531 and supplies them to target on each command. This is convenient,
25532 because a command line user would not want to specify that information
25533 explicitly on each command, and because user interacts with
25534 @value{GDBN} via a single terminal, so no confusion is possible as
25535 to what thread and frame are the current ones.
25537 In the case of MI, the concept of selected thread and frame is less
25538 useful. First, a frontend can easily remember this information
25539 itself. Second, a graphical frontend can have more than one window,
25540 each one used for debugging a different thread, and the frontend might
25541 want to access additional threads for internal purposes. This
25542 increases the risk that by relying on implicitly selected thread, the
25543 frontend may be operating on a wrong one. Therefore, each MI command
25544 should explicitly specify which thread and frame to operate on. To
25545 make it possible, each MI command accepts the @samp{--thread} and
25546 @samp{--frame} options, the value to each is @value{GDBN} global
25547 identifier for thread and frame to operate on.
25549 Usually, each top-level window in a frontend allows the user to select
25550 a thread and a frame, and remembers the user selection for further
25551 operations. However, in some cases @value{GDBN} may suggest that the
25552 current thread be changed. For example, when stopping on a breakpoint
25553 it is reasonable to switch to the thread where breakpoint is hit. For
25554 another example, if the user issues the CLI @samp{thread} command via
25555 the frontend, it is desirable to change the frontend's selected thread to the
25556 one specified by user. @value{GDBN} communicates the suggestion to
25557 change current thread using the @samp{=thread-selected} notification.
25558 No such notification is available for the selected frame at the moment.
25560 Note that historically, MI shares the selected thread with CLI, so
25561 frontends used the @code{-thread-select} to execute commands in the
25562 right context. However, getting this to work right is cumbersome. The
25563 simplest way is for frontend to emit @code{-thread-select} command
25564 before every command. This doubles the number of commands that need
25565 to be sent. The alternative approach is to suppress @code{-thread-select}
25566 if the selected thread in @value{GDBN} is supposed to be identical to the
25567 thread the frontend wants to operate on. However, getting this
25568 optimization right can be tricky. In particular, if the frontend
25569 sends several commands to @value{GDBN}, and one of the commands changes the
25570 selected thread, then the behaviour of subsequent commands will
25571 change. So, a frontend should either wait for response from such
25572 problematic commands, or explicitly add @code{-thread-select} for
25573 all subsequent commands. No frontend is known to do this exactly
25574 right, so it is suggested to just always pass the @samp{--thread} and
25575 @samp{--frame} options.
25577 @subsubsection Language
25579 The execution of several commands depends on which language is selected.
25580 By default, the current language (@pxref{show language}) is used.
25581 But for commands known to be language-sensitive, it is recommended
25582 to use the @samp{--language} option. This option takes one argument,
25583 which is the name of the language to use while executing the command.
25587 -data-evaluate-expression --language c "sizeof (void*)"
25592 The valid language names are the same names accepted by the
25593 @samp{set language} command (@pxref{Manually}), excluding @samp{auto},
25594 @samp{local} or @samp{unknown}.
25596 @node Asynchronous and non-stop modes
25597 @subsection Asynchronous command execution and non-stop mode
25599 On some targets, @value{GDBN} is capable of processing MI commands
25600 even while the target is running. This is called @dfn{asynchronous
25601 command execution} (@pxref{Background Execution}). The frontend may
25602 specify a preferrence for asynchronous execution using the
25603 @code{-gdb-set mi-async 1} command, which should be emitted before
25604 either running the executable or attaching to the target. After the
25605 frontend has started the executable or attached to the target, it can
25606 find if asynchronous execution is enabled using the
25607 @code{-list-target-features} command.
25610 @item -gdb-set mi-async on
25611 @item -gdb-set mi-async off
25612 Set whether MI is in asynchronous mode.
25614 When @code{off}, which is the default, MI execution commands (e.g.,
25615 @code{-exec-continue}) are foreground commands, and @value{GDBN} waits
25616 for the program to stop before processing further commands.
25618 When @code{on}, MI execution commands are background execution
25619 commands (e.g., @code{-exec-continue} becomes the equivalent of the
25620 @code{c&} CLI command), and so @value{GDBN} is capable of processing
25621 MI commands even while the target is running.
25623 @item -gdb-show mi-async
25624 Show whether MI asynchronous mode is enabled.
25627 Note: In @value{GDBN} version 7.7 and earlier, this option was called
25628 @code{target-async} instead of @code{mi-async}, and it had the effect
25629 of both putting MI in asynchronous mode and making CLI background
25630 commands possible. CLI background commands are now always possible
25631 ``out of the box'' if the target supports them. The old spelling is
25632 kept as a deprecated alias for backwards compatibility.
25634 Even if @value{GDBN} can accept a command while target is running,
25635 many commands that access the target do not work when the target is
25636 running. Therefore, asynchronous command execution is most useful
25637 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25638 it is possible to examine the state of one thread, while other threads
25641 When a given thread is running, MI commands that try to access the
25642 target in the context of that thread may not work, or may work only on
25643 some targets. In particular, commands that try to operate on thread's
25644 stack will not work, on any target. Commands that read memory, or
25645 modify breakpoints, may work or not work, depending on the target. Note
25646 that even commands that operate on global state, such as @code{print},
25647 @code{set}, and breakpoint commands, still access the target in the
25648 context of a specific thread, so frontend should try to find a
25649 stopped thread and perform the operation on that thread (using the
25650 @samp{--thread} option).
25652 Which commands will work in the context of a running thread is
25653 highly target dependent. However, the two commands
25654 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25655 to find the state of a thread, will always work.
25657 @node Thread groups
25658 @subsection Thread groups
25659 @value{GDBN} may be used to debug several processes at the same time.
25660 On some platfroms, @value{GDBN} may support debugging of several
25661 hardware systems, each one having several cores with several different
25662 processes running on each core. This section describes the MI
25663 mechanism to support such debugging scenarios.
25665 The key observation is that regardless of the structure of the
25666 target, MI can have a global list of threads, because most commands that
25667 accept the @samp{--thread} option do not need to know what process that
25668 thread belongs to. Therefore, it is not necessary to introduce
25669 neither additional @samp{--process} option, nor an notion of the
25670 current process in the MI interface. The only strictly new feature
25671 that is required is the ability to find how the threads are grouped
25674 To allow the user to discover such grouping, and to support arbitrary
25675 hierarchy of machines/cores/processes, MI introduces the concept of a
25676 @dfn{thread group}. Thread group is a collection of threads and other
25677 thread groups. A thread group always has a string identifier, a type,
25678 and may have additional attributes specific to the type. A new
25679 command, @code{-list-thread-groups}, returns the list of top-level
25680 thread groups, which correspond to processes that @value{GDBN} is
25681 debugging at the moment. By passing an identifier of a thread group
25682 to the @code{-list-thread-groups} command, it is possible to obtain
25683 the members of specific thread group.
25685 To allow the user to easily discover processes, and other objects, he
25686 wishes to debug, a concept of @dfn{available thread group} is
25687 introduced. Available thread group is an thread group that
25688 @value{GDBN} is not debugging, but that can be attached to, using the
25689 @code{-target-attach} command. The list of available top-level thread
25690 groups can be obtained using @samp{-list-thread-groups --available}.
25691 In general, the content of a thread group may be only retrieved only
25692 after attaching to that thread group.
25694 Thread groups are related to inferiors (@pxref{Inferiors and
25695 Programs}). Each inferior corresponds to a thread group of a special
25696 type @samp{process}, and some additional operations are permitted on
25697 such thread groups.
25699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25700 @node GDB/MI Command Syntax
25701 @section @sc{gdb/mi} Command Syntax
25704 * GDB/MI Input Syntax::
25705 * GDB/MI Output Syntax::
25708 @node GDB/MI Input Syntax
25709 @subsection @sc{gdb/mi} Input Syntax
25711 @cindex input syntax for @sc{gdb/mi}
25712 @cindex @sc{gdb/mi}, input syntax
25714 @item @var{command} @expansion{}
25715 @code{@var{cli-command} | @var{mi-command}}
25717 @item @var{cli-command} @expansion{}
25718 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25719 @var{cli-command} is any existing @value{GDBN} CLI command.
25721 @item @var{mi-command} @expansion{}
25722 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25723 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25725 @item @var{token} @expansion{}
25726 "any sequence of digits"
25728 @item @var{option} @expansion{}
25729 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25731 @item @var{parameter} @expansion{}
25732 @code{@var{non-blank-sequence} | @var{c-string}}
25734 @item @var{operation} @expansion{}
25735 @emph{any of the operations described in this chapter}
25737 @item @var{non-blank-sequence} @expansion{}
25738 @emph{anything, provided it doesn't contain special characters such as
25739 "-", @var{nl}, """ and of course " "}
25741 @item @var{c-string} @expansion{}
25742 @code{""" @var{seven-bit-iso-c-string-content} """}
25744 @item @var{nl} @expansion{}
25753 The CLI commands are still handled by the @sc{mi} interpreter; their
25754 output is described below.
25757 The @code{@var{token}}, when present, is passed back when the command
25761 Some @sc{mi} commands accept optional arguments as part of the parameter
25762 list. Each option is identified by a leading @samp{-} (dash) and may be
25763 followed by an optional argument parameter. Options occur first in the
25764 parameter list and can be delimited from normal parameters using
25765 @samp{--} (this is useful when some parameters begin with a dash).
25772 We want easy access to the existing CLI syntax (for debugging).
25775 We want it to be easy to spot a @sc{mi} operation.
25778 @node GDB/MI Output Syntax
25779 @subsection @sc{gdb/mi} Output Syntax
25781 @cindex output syntax of @sc{gdb/mi}
25782 @cindex @sc{gdb/mi}, output syntax
25783 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25784 followed, optionally, by a single result record. This result record
25785 is for the most recent command. The sequence of output records is
25786 terminated by @samp{(gdb)}.
25788 If an input command was prefixed with a @code{@var{token}} then the
25789 corresponding output for that command will also be prefixed by that same
25793 @item @var{output} @expansion{}
25794 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25796 @item @var{result-record} @expansion{}
25797 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25799 @item @var{out-of-band-record} @expansion{}
25800 @code{@var{async-record} | @var{stream-record}}
25802 @item @var{async-record} @expansion{}
25803 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25805 @item @var{exec-async-output} @expansion{}
25806 @code{[ @var{token} ] "*" @var{async-output nl}}
25808 @item @var{status-async-output} @expansion{}
25809 @code{[ @var{token} ] "+" @var{async-output nl}}
25811 @item @var{notify-async-output} @expansion{}
25812 @code{[ @var{token} ] "=" @var{async-output nl}}
25814 @item @var{async-output} @expansion{}
25815 @code{@var{async-class} ( "," @var{result} )*}
25817 @item @var{result-class} @expansion{}
25818 @code{"done" | "running" | "connected" | "error" | "exit"}
25820 @item @var{async-class} @expansion{}
25821 @code{"stopped" | @var{others}} (where @var{others} will be added
25822 depending on the needs---this is still in development).
25824 @item @var{result} @expansion{}
25825 @code{ @var{variable} "=" @var{value}}
25827 @item @var{variable} @expansion{}
25828 @code{ @var{string} }
25830 @item @var{value} @expansion{}
25831 @code{ @var{const} | @var{tuple} | @var{list} }
25833 @item @var{const} @expansion{}
25834 @code{@var{c-string}}
25836 @item @var{tuple} @expansion{}
25837 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25839 @item @var{list} @expansion{}
25840 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25841 @var{result} ( "," @var{result} )* "]" }
25843 @item @var{stream-record} @expansion{}
25844 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25846 @item @var{console-stream-output} @expansion{}
25847 @code{"~" @var{c-string nl}}
25849 @item @var{target-stream-output} @expansion{}
25850 @code{"@@" @var{c-string nl}}
25852 @item @var{log-stream-output} @expansion{}
25853 @code{"&" @var{c-string nl}}
25855 @item @var{nl} @expansion{}
25858 @item @var{token} @expansion{}
25859 @emph{any sequence of digits}.
25867 All output sequences end in a single line containing a period.
25870 The @code{@var{token}} is from the corresponding request. Note that
25871 for all async output, while the token is allowed by the grammar and
25872 may be output by future versions of @value{GDBN} for select async
25873 output messages, it is generally omitted. Frontends should treat
25874 all async output as reporting general changes in the state of the
25875 target and there should be no need to associate async output to any
25879 @cindex status output in @sc{gdb/mi}
25880 @var{status-async-output} contains on-going status information about the
25881 progress of a slow operation. It can be discarded. All status output is
25882 prefixed by @samp{+}.
25885 @cindex async output in @sc{gdb/mi}
25886 @var{exec-async-output} contains asynchronous state change on the target
25887 (stopped, started, disappeared). All async output is prefixed by
25891 @cindex notify output in @sc{gdb/mi}
25892 @var{notify-async-output} contains supplementary information that the
25893 client should handle (e.g., a new breakpoint information). All notify
25894 output is prefixed by @samp{=}.
25897 @cindex console output in @sc{gdb/mi}
25898 @var{console-stream-output} is output that should be displayed as is in the
25899 console. It is the textual response to a CLI command. All the console
25900 output is prefixed by @samp{~}.
25903 @cindex target output in @sc{gdb/mi}
25904 @var{target-stream-output} is the output produced by the target program.
25905 All the target output is prefixed by @samp{@@}.
25908 @cindex log output in @sc{gdb/mi}
25909 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25910 instance messages that should be displayed as part of an error log. All
25911 the log output is prefixed by @samp{&}.
25914 @cindex list output in @sc{gdb/mi}
25915 New @sc{gdb/mi} commands should only output @var{lists} containing
25921 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25922 details about the various output records.
25924 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25925 @node GDB/MI Compatibility with CLI
25926 @section @sc{gdb/mi} Compatibility with CLI
25928 @cindex compatibility, @sc{gdb/mi} and CLI
25929 @cindex @sc{gdb/mi}, compatibility with CLI
25931 For the developers convenience CLI commands can be entered directly,
25932 but there may be some unexpected behaviour. For example, commands
25933 that query the user will behave as if the user replied yes, breakpoint
25934 command lists are not executed and some CLI commands, such as
25935 @code{if}, @code{when} and @code{define}, prompt for further input with
25936 @samp{>}, which is not valid MI output.
25938 This feature may be removed at some stage in the future and it is
25939 recommended that front ends use the @code{-interpreter-exec} command
25940 (@pxref{-interpreter-exec}).
25942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25943 @node GDB/MI Development and Front Ends
25944 @section @sc{gdb/mi} Development and Front Ends
25945 @cindex @sc{gdb/mi} development
25947 The application which takes the MI output and presents the state of the
25948 program being debugged to the user is called a @dfn{front end}.
25950 Although @sc{gdb/mi} is still incomplete, it is currently being used
25951 by a variety of front ends to @value{GDBN}. This makes it difficult
25952 to introduce new functionality without breaking existing usage. This
25953 section tries to minimize the problems by describing how the protocol
25956 Some changes in MI need not break a carefully designed front end, and
25957 for these the MI version will remain unchanged. The following is a
25958 list of changes that may occur within one level, so front ends should
25959 parse MI output in a way that can handle them:
25963 New MI commands may be added.
25966 New fields may be added to the output of any MI command.
25969 The range of values for fields with specified values, e.g.,
25970 @code{in_scope} (@pxref{-var-update}) may be extended.
25972 @c The format of field's content e.g type prefix, may change so parse it
25973 @c at your own risk. Yes, in general?
25975 @c The order of fields may change? Shouldn't really matter but it might
25976 @c resolve inconsistencies.
25979 If the changes are likely to break front ends, the MI version level
25980 will be increased by one. This will allow the front end to parse the
25981 output according to the MI version. Apart from mi0, new versions of
25982 @value{GDBN} will not support old versions of MI and it will be the
25983 responsibility of the front end to work with the new one.
25985 @c Starting with mi3, add a new command -mi-version that prints the MI
25988 The best way to avoid unexpected changes in MI that might break your front
25989 end is to make your project known to @value{GDBN} developers and
25990 follow development on @email{gdb@@sourceware.org} and
25991 @email{gdb-patches@@sourceware.org}.
25992 @cindex mailing lists
25994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25995 @node GDB/MI Output Records
25996 @section @sc{gdb/mi} Output Records
25999 * GDB/MI Result Records::
26000 * GDB/MI Stream Records::
26001 * GDB/MI Async Records::
26002 * GDB/MI Breakpoint Information::
26003 * GDB/MI Frame Information::
26004 * GDB/MI Thread Information::
26005 * GDB/MI Ada Exception Information::
26008 @node GDB/MI Result Records
26009 @subsection @sc{gdb/mi} Result Records
26011 @cindex result records in @sc{gdb/mi}
26012 @cindex @sc{gdb/mi}, result records
26013 In addition to a number of out-of-band notifications, the response to a
26014 @sc{gdb/mi} command includes one of the following result indications:
26018 @item "^done" [ "," @var{results} ]
26019 The synchronous operation was successful, @code{@var{results}} are the return
26024 This result record is equivalent to @samp{^done}. Historically, it
26025 was output instead of @samp{^done} if the command has resumed the
26026 target. This behaviour is maintained for backward compatibility, but
26027 all frontends should treat @samp{^done} and @samp{^running}
26028 identically and rely on the @samp{*running} output record to determine
26029 which threads are resumed.
26033 @value{GDBN} has connected to a remote target.
26035 @item "^error" "," "msg=" @var{c-string} [ "," "code=" @var{c-string} ]
26037 The operation failed. The @code{msg=@var{c-string}} variable contains
26038 the corresponding error message.
26040 If present, the @code{code=@var{c-string}} variable provides an error
26041 code on which consumers can rely on to detect the corresponding
26042 error condition. At present, only one error code is defined:
26045 @item "undefined-command"
26046 Indicates that the command causing the error does not exist.
26051 @value{GDBN} has terminated.
26055 @node GDB/MI Stream Records
26056 @subsection @sc{gdb/mi} Stream Records
26058 @cindex @sc{gdb/mi}, stream records
26059 @cindex stream records in @sc{gdb/mi}
26060 @value{GDBN} internally maintains a number of output streams: the console, the
26061 target, and the log. The output intended for each of these streams is
26062 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26064 Each stream record begins with a unique @dfn{prefix character} which
26065 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26066 Syntax}). In addition to the prefix, each stream record contains a
26067 @code{@var{string-output}}. This is either raw text (with an implicit new
26068 line) or a quoted C string (which does not contain an implicit newline).
26071 @item "~" @var{string-output}
26072 The console output stream contains text that should be displayed in the
26073 CLI console window. It contains the textual responses to CLI commands.
26075 @item "@@" @var{string-output}
26076 The target output stream contains any textual output from the running
26077 target. This is only present when GDB's event loop is truly
26078 asynchronous, which is currently only the case for remote targets.
26080 @item "&" @var{string-output}
26081 The log stream contains debugging messages being produced by @value{GDBN}'s
26085 @node GDB/MI Async Records
26086 @subsection @sc{gdb/mi} Async Records
26088 @cindex async records in @sc{gdb/mi}
26089 @cindex @sc{gdb/mi}, async records
26090 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26091 additional changes that have occurred. Those changes can either be a
26092 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26093 target activity (e.g., target stopped).
26095 The following is the list of possible async records:
26099 @item *running,thread-id="@var{thread}"
26100 The target is now running. The @var{thread} field can be the global
26101 thread ID of the the thread that is now running, and it can be
26102 @samp{all} if all threads are running. The frontend should assume
26103 that no interaction with a running thread is possible after this
26104 notification is produced. The frontend should not assume that this
26105 notification is output only once for any command. @value{GDBN} may
26106 emit this notification several times, either for different threads,
26107 because it cannot resume all threads together, or even for a single
26108 thread, if the thread must be stepped though some code before letting
26111 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26112 The target has stopped. The @var{reason} field can have one of the
26116 @item breakpoint-hit
26117 A breakpoint was reached.
26118 @item watchpoint-trigger
26119 A watchpoint was triggered.
26120 @item read-watchpoint-trigger
26121 A read watchpoint was triggered.
26122 @item access-watchpoint-trigger
26123 An access watchpoint was triggered.
26124 @item function-finished
26125 An -exec-finish or similar CLI command was accomplished.
26126 @item location-reached
26127 An -exec-until or similar CLI command was accomplished.
26128 @item watchpoint-scope
26129 A watchpoint has gone out of scope.
26130 @item end-stepping-range
26131 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26132 similar CLI command was accomplished.
26133 @item exited-signalled
26134 The inferior exited because of a signal.
26136 The inferior exited.
26137 @item exited-normally
26138 The inferior exited normally.
26139 @item signal-received
26140 A signal was received by the inferior.
26142 The inferior has stopped due to a library being loaded or unloaded.
26143 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26144 set or when a @code{catch load} or @code{catch unload} catchpoint is
26145 in use (@pxref{Set Catchpoints}).
26147 The inferior has forked. This is reported when @code{catch fork}
26148 (@pxref{Set Catchpoints}) has been used.
26150 The inferior has vforked. This is reported in when @code{catch vfork}
26151 (@pxref{Set Catchpoints}) has been used.
26152 @item syscall-entry
26153 The inferior entered a system call. This is reported when @code{catch
26154 syscall} (@pxref{Set Catchpoints}) has been used.
26155 @item syscall-return
26156 The inferior returned from a system call. This is reported when
26157 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26159 The inferior called @code{exec}. This is reported when @code{catch exec}
26160 (@pxref{Set Catchpoints}) has been used.
26163 The @var{id} field identifies the global thread ID of the thread
26164 that directly caused the stop -- for example by hitting a breakpoint.
26165 Depending on whether all-stop
26166 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26167 stop all threads, or only the thread that directly triggered the stop.
26168 If all threads are stopped, the @var{stopped} field will have the
26169 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26170 field will be a list of thread identifiers. Presently, this list will
26171 always include a single thread, but frontend should be prepared to see
26172 several threads in the list. The @var{core} field reports the
26173 processor core on which the stop event has happened. This field may be absent
26174 if such information is not available.
26176 @item =thread-group-added,id="@var{id}"
26177 @itemx =thread-group-removed,id="@var{id}"
26178 A thread group was either added or removed. The @var{id} field
26179 contains the @value{GDBN} identifier of the thread group. When a thread
26180 group is added, it generally might not be associated with a running
26181 process. When a thread group is removed, its id becomes invalid and
26182 cannot be used in any way.
26184 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26185 A thread group became associated with a running program,
26186 either because the program was just started or the thread group
26187 was attached to a program. The @var{id} field contains the
26188 @value{GDBN} identifier of the thread group. The @var{pid} field
26189 contains process identifier, specific to the operating system.
26191 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26192 A thread group is no longer associated with a running program,
26193 either because the program has exited, or because it was detached
26194 from. The @var{id} field contains the @value{GDBN} identifier of the
26195 thread group. The @var{code} field is the exit code of the inferior; it exists
26196 only when the inferior exited with some code.
26198 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26199 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26200 A thread either was created, or has exited. The @var{id} field
26201 contains the global @value{GDBN} identifier of the thread. The @var{gid}
26202 field identifies the thread group this thread belongs to.
26204 @item =thread-selected,id="@var{id}"
26205 Informs that the selected thread was changed as result of the last
26206 command. This notification is not emitted as result of @code{-thread-select}
26207 command but is emitted whenever an MI command that is not documented
26208 to change the selected thread actually changes it. In particular,
26209 invoking, directly or indirectly (via user-defined command), the CLI
26210 @code{thread} command, will generate this notification.
26212 We suggest that in response to this notification, front ends
26213 highlight the selected thread and cause subsequent commands to apply to
26216 @item =library-loaded,...
26217 Reports that a new library file was loaded by the program. This
26218 notification has 4 fields---@var{id}, @var{target-name},
26219 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26220 opaque identifier of the library. For remote debugging case,
26221 @var{target-name} and @var{host-name} fields give the name of the
26222 library file on the target, and on the host respectively. For native
26223 debugging, both those fields have the same value. The
26224 @var{symbols-loaded} field is emitted only for backward compatibility
26225 and should not be relied on to convey any useful information. The
26226 @var{thread-group} field, if present, specifies the id of the thread
26227 group in whose context the library was loaded. If the field is
26228 absent, it means the library was loaded in the context of all present
26231 @item =library-unloaded,...
26232 Reports that a library was unloaded by the program. This notification
26233 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26234 the same meaning as for the @code{=library-loaded} notification.
26235 The @var{thread-group} field, if present, specifies the id of the
26236 thread group in whose context the library was unloaded. If the field is
26237 absent, it means the library was unloaded in the context of all present
26240 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
26241 @itemx =traceframe-changed,end
26242 Reports that the trace frame was changed and its new number is
26243 @var{tfnum}. The number of the tracepoint associated with this trace
26244 frame is @var{tpnum}.
26246 @item =tsv-created,name=@var{name},initial=@var{initial}
26247 Reports that the new trace state variable @var{name} is created with
26248 initial value @var{initial}.
26250 @item =tsv-deleted,name=@var{name}
26251 @itemx =tsv-deleted
26252 Reports that the trace state variable @var{name} is deleted or all
26253 trace state variables are deleted.
26255 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
26256 Reports that the trace state variable @var{name} is modified with
26257 the initial value @var{initial}. The current value @var{current} of
26258 trace state variable is optional and is reported if the current
26259 value of trace state variable is known.
26261 @item =breakpoint-created,bkpt=@{...@}
26262 @itemx =breakpoint-modified,bkpt=@{...@}
26263 @itemx =breakpoint-deleted,id=@var{number}
26264 Reports that a breakpoint was created, modified, or deleted,
26265 respectively. Only user-visible breakpoints are reported to the MI
26268 The @var{bkpt} argument is of the same form as returned by the various
26269 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
26270 @var{number} is the ordinal number of the breakpoint.
26272 Note that if a breakpoint is emitted in the result record of a
26273 command, then it will not also be emitted in an async record.
26275 @item =record-started,thread-group="@var{id}"
26276 @itemx =record-stopped,thread-group="@var{id}"
26277 Execution log recording was either started or stopped on an
26278 inferior. The @var{id} is the @value{GDBN} identifier of the thread
26279 group corresponding to the affected inferior.
26281 @item =cmd-param-changed,param=@var{param},value=@var{value}
26282 Reports that a parameter of the command @code{set @var{param}} is
26283 changed to @var{value}. In the multi-word @code{set} command,
26284 the @var{param} is the whole parameter list to @code{set} command.
26285 For example, In command @code{set check type on}, @var{param}
26286 is @code{check type} and @var{value} is @code{on}.
26288 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
26289 Reports that bytes from @var{addr} to @var{data} + @var{len} were
26290 written in an inferior. The @var{id} is the identifier of the
26291 thread group corresponding to the affected inferior. The optional
26292 @code{type="code"} part is reported if the memory written to holds
26296 @node GDB/MI Breakpoint Information
26297 @subsection @sc{gdb/mi} Breakpoint Information
26299 When @value{GDBN} reports information about a breakpoint, a
26300 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
26305 The breakpoint number. For a breakpoint that represents one location
26306 of a multi-location breakpoint, this will be a dotted pair, like
26310 The type of the breakpoint. For ordinary breakpoints this will be
26311 @samp{breakpoint}, but many values are possible.
26314 If the type of the breakpoint is @samp{catchpoint}, then this
26315 indicates the exact type of catchpoint.
26318 This is the breakpoint disposition---either @samp{del}, meaning that
26319 the breakpoint will be deleted at the next stop, or @samp{keep},
26320 meaning that the breakpoint will not be deleted.
26323 This indicates whether the breakpoint is enabled, in which case the
26324 value is @samp{y}, or disabled, in which case the value is @samp{n}.
26325 Note that this is not the same as the field @code{enable}.
26328 The address of the breakpoint. This may be a hexidecimal number,
26329 giving the address; or the string @samp{<PENDING>}, for a pending
26330 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
26331 multiple locations. This field will not be present if no address can
26332 be determined. For example, a watchpoint does not have an address.
26335 If known, the function in which the breakpoint appears.
26336 If not known, this field is not present.
26339 The name of the source file which contains this function, if known.
26340 If not known, this field is not present.
26343 The full file name of the source file which contains this function, if
26344 known. If not known, this field is not present.
26347 The line number at which this breakpoint appears, if known.
26348 If not known, this field is not present.
26351 If the source file is not known, this field may be provided. If
26352 provided, this holds the address of the breakpoint, possibly followed
26356 If this breakpoint is pending, this field is present and holds the
26357 text used to set the breakpoint, as entered by the user.
26360 Where this breakpoint's condition is evaluated, either @samp{host} or
26364 If this is a thread-specific breakpoint, then this identifies the
26365 thread in which the breakpoint can trigger.
26368 If this breakpoint is restricted to a particular Ada task, then this
26369 field will hold the task identifier.
26372 If the breakpoint is conditional, this is the condition expression.
26375 The ignore count of the breakpoint.
26378 The enable count of the breakpoint.
26380 @item traceframe-usage
26383 @item static-tracepoint-marker-string-id
26384 For a static tracepoint, the name of the static tracepoint marker.
26387 For a masked watchpoint, this is the mask.
26390 A tracepoint's pass count.
26392 @item original-location
26393 The location of the breakpoint as originally specified by the user.
26394 This field is optional.
26397 The number of times the breakpoint has been hit.
26400 This field is only given for tracepoints. This is either @samp{y},
26401 meaning that the tracepoint is installed, or @samp{n}, meaning that it
26405 Some extra data, the exact contents of which are type-dependent.
26409 For example, here is what the output of @code{-break-insert}
26410 (@pxref{GDB/MI Breakpoint Commands}) might be:
26413 -> -break-insert main
26414 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26415 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26416 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26421 @node GDB/MI Frame Information
26422 @subsection @sc{gdb/mi} Frame Information
26424 Response from many MI commands includes an information about stack
26425 frame. This information is a tuple that may have the following
26430 The level of the stack frame. The innermost frame has the level of
26431 zero. This field is always present.
26434 The name of the function corresponding to the frame. This field may
26435 be absent if @value{GDBN} is unable to determine the function name.
26438 The code address for the frame. This field is always present.
26441 The name of the source files that correspond to the frame's code
26442 address. This field may be absent.
26445 The source line corresponding to the frames' code address. This field
26449 The name of the binary file (either executable or shared library) the
26450 corresponds to the frame's code address. This field may be absent.
26454 @node GDB/MI Thread Information
26455 @subsection @sc{gdb/mi} Thread Information
26457 Whenever @value{GDBN} has to report an information about a thread, it
26458 uses a tuple with the following fields:
26462 The global numeric id assigned to the thread by @value{GDBN}. This field is
26466 Target-specific string identifying the thread. This field is always present.
26469 Additional information about the thread provided by the target.
26470 It is supposed to be human-readable and not interpreted by the
26471 frontend. This field is optional.
26474 Either @samp{stopped} or @samp{running}, depending on whether the
26475 thread is presently running. This field is always present.
26478 The value of this field is an integer number of the processor core the
26479 thread was last seen on. This field is optional.
26482 @node GDB/MI Ada Exception Information
26483 @subsection @sc{gdb/mi} Ada Exception Information
26485 Whenever a @code{*stopped} record is emitted because the program
26486 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26487 @value{GDBN} provides the name of the exception that was raised via
26488 the @code{exception-name} field.
26490 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26491 @node GDB/MI Simple Examples
26492 @section Simple Examples of @sc{gdb/mi} Interaction
26493 @cindex @sc{gdb/mi}, simple examples
26495 This subsection presents several simple examples of interaction using
26496 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26497 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26498 the output received from @sc{gdb/mi}.
26500 Note the line breaks shown in the examples are here only for
26501 readability, they don't appear in the real output.
26503 @subheading Setting a Breakpoint
26505 Setting a breakpoint generates synchronous output which contains detailed
26506 information of the breakpoint.
26509 -> -break-insert main
26510 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26511 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26512 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
26517 @subheading Program Execution
26519 Program execution generates asynchronous records and MI gives the
26520 reason that execution stopped.
26526 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26527 frame=@{addr="0x08048564",func="main",
26528 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26529 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26534 <- *stopped,reason="exited-normally"
26538 @subheading Quitting @value{GDBN}
26540 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26548 Please note that @samp{^exit} is printed immediately, but it might
26549 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26550 performs necessary cleanups, including killing programs being debugged
26551 or disconnecting from debug hardware, so the frontend should wait till
26552 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26553 fails to exit in reasonable time.
26555 @subheading A Bad Command
26557 Here's what happens if you pass a non-existent command:
26561 <- ^error,msg="Undefined MI command: rubbish"
26566 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26567 @node GDB/MI Command Description Format
26568 @section @sc{gdb/mi} Command Description Format
26570 The remaining sections describe blocks of commands. Each block of
26571 commands is laid out in a fashion similar to this section.
26573 @subheading Motivation
26575 The motivation for this collection of commands.
26577 @subheading Introduction
26579 A brief introduction to this collection of commands as a whole.
26581 @subheading Commands
26583 For each command in the block, the following is described:
26585 @subsubheading Synopsis
26588 -command @var{args}@dots{}
26591 @subsubheading Result
26593 @subsubheading @value{GDBN} Command
26595 The corresponding @value{GDBN} CLI command(s), if any.
26597 @subsubheading Example
26599 Example(s) formatted for readability. Some of the described commands have
26600 not been implemented yet and these are labeled N.A.@: (not available).
26603 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26604 @node GDB/MI Breakpoint Commands
26605 @section @sc{gdb/mi} Breakpoint Commands
26607 @cindex breakpoint commands for @sc{gdb/mi}
26608 @cindex @sc{gdb/mi}, breakpoint commands
26609 This section documents @sc{gdb/mi} commands for manipulating
26612 @subheading The @code{-break-after} Command
26613 @findex -break-after
26615 @subsubheading Synopsis
26618 -break-after @var{number} @var{count}
26621 The breakpoint number @var{number} is not in effect until it has been
26622 hit @var{count} times. To see how this is reflected in the output of
26623 the @samp{-break-list} command, see the description of the
26624 @samp{-break-list} command below.
26626 @subsubheading @value{GDBN} Command
26628 The corresponding @value{GDBN} command is @samp{ignore}.
26630 @subsubheading Example
26635 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26636 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26637 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26645 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26646 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26647 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26648 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26649 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26650 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26651 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26652 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26653 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26654 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
26659 @subheading The @code{-break-catch} Command
26660 @findex -break-catch
26663 @subheading The @code{-break-commands} Command
26664 @findex -break-commands
26666 @subsubheading Synopsis
26669 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26672 Specifies the CLI commands that should be executed when breakpoint
26673 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26674 are the commands. If no command is specified, any previously-set
26675 commands are cleared. @xref{Break Commands}. Typical use of this
26676 functionality is tracing a program, that is, printing of values of
26677 some variables whenever breakpoint is hit and then continuing.
26679 @subsubheading @value{GDBN} Command
26681 The corresponding @value{GDBN} command is @samp{commands}.
26683 @subsubheading Example
26688 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26689 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26690 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
26693 -break-commands 1 "print v" "continue"
26698 @subheading The @code{-break-condition} Command
26699 @findex -break-condition
26701 @subsubheading Synopsis
26704 -break-condition @var{number} @var{expr}
26707 Breakpoint @var{number} will stop the program only if the condition in
26708 @var{expr} is true. The condition becomes part of the
26709 @samp{-break-list} output (see the description of the @samp{-break-list}
26712 @subsubheading @value{GDBN} Command
26714 The corresponding @value{GDBN} command is @samp{condition}.
26716 @subsubheading Example
26720 -break-condition 1 1
26724 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26725 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26726 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26727 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26728 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26729 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26730 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26731 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26732 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26733 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
26737 @subheading The @code{-break-delete} Command
26738 @findex -break-delete
26740 @subsubheading Synopsis
26743 -break-delete ( @var{breakpoint} )+
26746 Delete the breakpoint(s) whose number(s) are specified in the argument
26747 list. This is obviously reflected in the breakpoint list.
26749 @subsubheading @value{GDBN} Command
26751 The corresponding @value{GDBN} command is @samp{delete}.
26753 @subsubheading Example
26761 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26762 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26763 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26764 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26765 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26766 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26767 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26772 @subheading The @code{-break-disable} Command
26773 @findex -break-disable
26775 @subsubheading Synopsis
26778 -break-disable ( @var{breakpoint} )+
26781 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26782 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26784 @subsubheading @value{GDBN} Command
26786 The corresponding @value{GDBN} command is @samp{disable}.
26788 @subsubheading Example
26796 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26797 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26798 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26799 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26800 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26801 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26802 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26803 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26804 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26805 line="5",thread-groups=["i1"],times="0"@}]@}
26809 @subheading The @code{-break-enable} Command
26810 @findex -break-enable
26812 @subsubheading Synopsis
26815 -break-enable ( @var{breakpoint} )+
26818 Enable (previously disabled) @var{breakpoint}(s).
26820 @subsubheading @value{GDBN} Command
26822 The corresponding @value{GDBN} command is @samp{enable}.
26824 @subsubheading Example
26832 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26833 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26834 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26835 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26836 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26837 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26838 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26839 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26840 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26841 line="5",thread-groups=["i1"],times="0"@}]@}
26845 @subheading The @code{-break-info} Command
26846 @findex -break-info
26848 @subsubheading Synopsis
26851 -break-info @var{breakpoint}
26855 Get information about a single breakpoint.
26857 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
26858 Information}, for details on the format of each breakpoint in the
26861 @subsubheading @value{GDBN} Command
26863 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26865 @subsubheading Example
26868 @subheading The @code{-break-insert} Command
26869 @findex -break-insert
26870 @anchor{-break-insert}
26872 @subsubheading Synopsis
26875 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26876 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26877 [ -p @var{thread-id} ] [ @var{location} ]
26881 If specified, @var{location}, can be one of:
26884 @item linespec location
26885 A linespec location. @xref{Linespec Locations}.
26887 @item explicit location
26888 An explicit location. @sc{gdb/mi} explicit locations are
26889 analogous to the CLI's explicit locations using the option names
26890 listed below. @xref{Explicit Locations}.
26893 @item --source @var{filename}
26894 The source file name of the location. This option requires the use
26895 of either @samp{--function} or @samp{--line}.
26897 @item --function @var{function}
26898 The name of a function or method.
26900 @item --label @var{label}
26901 The name of a label.
26903 @item --line @var{lineoffset}
26904 An absolute or relative line offset from the start of the location.
26907 @item address location
26908 An address location, *@var{address}. @xref{Address Locations}.
26912 The possible optional parameters of this command are:
26916 Insert a temporary breakpoint.
26918 Insert a hardware breakpoint.
26920 If @var{location} cannot be parsed (for example if it
26921 refers to unknown files or functions), create a pending
26922 breakpoint. Without this flag, @value{GDBN} will report
26923 an error, and won't create a breakpoint, if @var{location}
26926 Create a disabled breakpoint.
26928 Create a tracepoint. @xref{Tracepoints}. When this parameter
26929 is used together with @samp{-h}, a fast tracepoint is created.
26930 @item -c @var{condition}
26931 Make the breakpoint conditional on @var{condition}.
26932 @item -i @var{ignore-count}
26933 Initialize the @var{ignore-count}.
26934 @item -p @var{thread-id}
26935 Restrict the breakpoint to the thread with the specified global
26939 @subsubheading Result
26941 @xref{GDB/MI Breakpoint Information}, for details on the format of the
26942 resulting breakpoint.
26944 Note: this format is open to change.
26945 @c An out-of-band breakpoint instead of part of the result?
26947 @subsubheading @value{GDBN} Command
26949 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26950 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
26952 @subsubheading Example
26957 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26958 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
26961 -break-insert -t foo
26962 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26963 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
26967 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26968 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26969 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26970 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26971 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26972 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26973 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26974 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26975 addr="0x0001072c", func="main",file="recursive2.c",
26976 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
26978 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26979 addr="0x00010774",func="foo",file="recursive2.c",
26980 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26983 @c -break-insert -r foo.*
26984 @c ~int foo(int, int);
26985 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26986 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
26991 @subheading The @code{-dprintf-insert} Command
26992 @findex -dprintf-insert
26994 @subsubheading Synopsis
26997 -dprintf-insert [ -t ] [ -f ] [ -d ]
26998 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26999 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
27004 If supplied, @var{location} may be specified the same way as for
27005 the @code{-break-insert} command. @xref{-break-insert}.
27007 The possible optional parameters of this command are:
27011 Insert a temporary breakpoint.
27013 If @var{location} cannot be parsed (for example, if it
27014 refers to unknown files or functions), create a pending
27015 breakpoint. Without this flag, @value{GDBN} will report
27016 an error, and won't create a breakpoint, if @var{location}
27019 Create a disabled breakpoint.
27020 @item -c @var{condition}
27021 Make the breakpoint conditional on @var{condition}.
27022 @item -i @var{ignore-count}
27023 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
27024 to @var{ignore-count}.
27025 @item -p @var{thread-id}
27026 Restrict the breakpoint to the thread with the specified global
27030 @subsubheading Result
27032 @xref{GDB/MI Breakpoint Information}, for details on the format of the
27033 resulting breakpoint.
27035 @c An out-of-band breakpoint instead of part of the result?
27037 @subsubheading @value{GDBN} Command
27039 The corresponding @value{GDBN} command is @samp{dprintf}.
27041 @subsubheading Example
27045 4-dprintf-insert foo "At foo entry\n"
27046 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
27047 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
27048 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
27049 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
27050 original-location="foo"@}
27052 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
27053 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
27054 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
27055 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
27056 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
27057 original-location="mi-dprintf.c:26"@}
27061 @subheading The @code{-break-list} Command
27062 @findex -break-list
27064 @subsubheading Synopsis
27070 Displays the list of inserted breakpoints, showing the following fields:
27074 number of the breakpoint
27076 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27078 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27081 is the breakpoint enabled or no: @samp{y} or @samp{n}
27083 memory location at which the breakpoint is set
27085 logical location of the breakpoint, expressed by function name, file
27087 @item Thread-groups
27088 list of thread groups to which this breakpoint applies
27090 number of times the breakpoint has been hit
27093 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27094 @code{body} field is an empty list.
27096 @subsubheading @value{GDBN} Command
27098 The corresponding @value{GDBN} command is @samp{info break}.
27100 @subsubheading Example
27105 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27106 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27107 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27108 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27109 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27110 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27111 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27112 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27113 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
27115 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27116 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27117 line="13",thread-groups=["i1"],times="0"@}]@}
27121 Here's an example of the result when there are no breakpoints:
27126 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27127 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27128 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27129 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27130 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27131 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27132 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27137 @subheading The @code{-break-passcount} Command
27138 @findex -break-passcount
27140 @subsubheading Synopsis
27143 -break-passcount @var{tracepoint-number} @var{passcount}
27146 Set the passcount for tracepoint @var{tracepoint-number} to
27147 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27148 is not a tracepoint, error is emitted. This corresponds to CLI
27149 command @samp{passcount}.
27151 @subheading The @code{-break-watch} Command
27152 @findex -break-watch
27154 @subsubheading Synopsis
27157 -break-watch [ -a | -r ]
27160 Create a watchpoint. With the @samp{-a} option it will create an
27161 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27162 read from or on a write to the memory location. With the @samp{-r}
27163 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27164 trigger only when the memory location is accessed for reading. Without
27165 either of the options, the watchpoint created is a regular watchpoint,
27166 i.e., it will trigger when the memory location is accessed for writing.
27167 @xref{Set Watchpoints, , Setting Watchpoints}.
27169 Note that @samp{-break-list} will report a single list of watchpoints and
27170 breakpoints inserted.
27172 @subsubheading @value{GDBN} Command
27174 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27177 @subsubheading Example
27179 Setting a watchpoint on a variable in the @code{main} function:
27184 ^done,wpt=@{number="2",exp="x"@}
27189 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27190 value=@{old="-268439212",new="55"@},
27191 frame=@{func="main",args=[],file="recursive2.c",
27192 fullname="/home/foo/bar/recursive2.c",line="5"@}
27196 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27197 the program execution twice: first for the variable changing value, then
27198 for the watchpoint going out of scope.
27203 ^done,wpt=@{number="5",exp="C"@}
27208 *stopped,reason="watchpoint-trigger",
27209 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27210 frame=@{func="callee4",args=[],
27211 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27212 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27217 *stopped,reason="watchpoint-scope",wpnum="5",
27218 frame=@{func="callee3",args=[@{name="strarg",
27219 value="0x11940 \"A string argument.\""@}],
27220 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27221 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27225 Listing breakpoints and watchpoints, at different points in the program
27226 execution. Note that once the watchpoint goes out of scope, it is
27232 ^done,wpt=@{number="2",exp="C"@}
27235 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27236 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27237 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27238 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27239 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27240 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27241 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27242 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27243 addr="0x00010734",func="callee4",
27244 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27245 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
27247 bkpt=@{number="2",type="watchpoint",disp="keep",
27248 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
27253 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27254 value=@{old="-276895068",new="3"@},
27255 frame=@{func="callee4",args=[],
27256 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27257 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27260 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27261 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27262 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27263 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27264 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27265 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27266 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27267 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27268 addr="0x00010734",func="callee4",
27269 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27270 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
27272 bkpt=@{number="2",type="watchpoint",disp="keep",
27273 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
27277 ^done,reason="watchpoint-scope",wpnum="2",
27278 frame=@{func="callee3",args=[@{name="strarg",
27279 value="0x11940 \"A string argument.\""@}],
27280 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27281 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27284 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27285 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27286 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27287 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27288 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27289 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27290 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27291 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27292 addr="0x00010734",func="callee4",
27293 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27294 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27295 thread-groups=["i1"],times="1"@}]@}
27300 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27301 @node GDB/MI Catchpoint Commands
27302 @section @sc{gdb/mi} Catchpoint Commands
27304 This section documents @sc{gdb/mi} commands for manipulating
27308 * Shared Library GDB/MI Catchpoint Commands::
27309 * Ada Exception GDB/MI Catchpoint Commands::
27312 @node Shared Library GDB/MI Catchpoint Commands
27313 @subsection Shared Library @sc{gdb/mi} Catchpoints
27315 @subheading The @code{-catch-load} Command
27316 @findex -catch-load
27318 @subsubheading Synopsis
27321 -catch-load [ -t ] [ -d ] @var{regexp}
27324 Add a catchpoint for library load events. If the @samp{-t} option is used,
27325 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27326 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
27327 in a disabled state. The @samp{regexp} argument is a regular
27328 expression used to match the name of the loaded library.
27331 @subsubheading @value{GDBN} Command
27333 The corresponding @value{GDBN} command is @samp{catch load}.
27335 @subsubheading Example
27338 -catch-load -t foo.so
27339 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
27340 what="load of library matching foo.so",catch-type="load",times="0"@}
27345 @subheading The @code{-catch-unload} Command
27346 @findex -catch-unload
27348 @subsubheading Synopsis
27351 -catch-unload [ -t ] [ -d ] @var{regexp}
27354 Add a catchpoint for library unload events. If the @samp{-t} option is
27355 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
27356 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
27357 created in a disabled state. The @samp{regexp} argument is a regular
27358 expression used to match the name of the unloaded library.
27360 @subsubheading @value{GDBN} Command
27362 The corresponding @value{GDBN} command is @samp{catch unload}.
27364 @subsubheading Example
27367 -catch-unload -d bar.so
27368 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
27369 what="load of library matching bar.so",catch-type="unload",times="0"@}
27373 @node Ada Exception GDB/MI Catchpoint Commands
27374 @subsection Ada Exception @sc{gdb/mi} Catchpoints
27376 The following @sc{gdb/mi} commands can be used to create catchpoints
27377 that stop the execution when Ada exceptions are being raised.
27379 @subheading The @code{-catch-assert} Command
27380 @findex -catch-assert
27382 @subsubheading Synopsis
27385 -catch-assert [ -c @var{condition}] [ -d ] [ -t ]
27388 Add a catchpoint for failed Ada assertions.
27390 The possible optional parameters for this command are:
27393 @item -c @var{condition}
27394 Make the catchpoint conditional on @var{condition}.
27396 Create a disabled catchpoint.
27398 Create a temporary catchpoint.
27401 @subsubheading @value{GDBN} Command
27403 The corresponding @value{GDBN} command is @samp{catch assert}.
27405 @subsubheading Example
27409 ^done,bkptno="5",bkpt=@{number="5",type="breakpoint",disp="keep",
27410 enabled="y",addr="0x0000000000404888",what="failed Ada assertions",
27411 thread-groups=["i1"],times="0",
27412 original-location="__gnat_debug_raise_assert_failure"@}
27416 @subheading The @code{-catch-exception} Command
27417 @findex -catch-exception
27419 @subsubheading Synopsis
27422 -catch-exception [ -c @var{condition}] [ -d ] [ -e @var{exception-name} ]
27426 Add a catchpoint stopping when Ada exceptions are raised.
27427 By default, the command stops the program when any Ada exception
27428 gets raised. But it is also possible, by using some of the
27429 optional parameters described below, to create more selective
27432 The possible optional parameters for this command are:
27435 @item -c @var{condition}
27436 Make the catchpoint conditional on @var{condition}.
27438 Create a disabled catchpoint.
27439 @item -e @var{exception-name}
27440 Only stop when @var{exception-name} is raised. This option cannot
27441 be used combined with @samp{-u}.
27443 Create a temporary catchpoint.
27445 Stop only when an unhandled exception gets raised. This option
27446 cannot be used combined with @samp{-e}.
27449 @subsubheading @value{GDBN} Command
27451 The corresponding @value{GDBN} commands are @samp{catch exception}
27452 and @samp{catch exception unhandled}.
27454 @subsubheading Example
27457 -catch-exception -e Program_Error
27458 ^done,bkptno="4",bkpt=@{number="4",type="breakpoint",disp="keep",
27459 enabled="y",addr="0x0000000000404874",
27460 what="`Program_Error' Ada exception", thread-groups=["i1"],
27461 times="0",original-location="__gnat_debug_raise_exception"@}
27465 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27466 @node GDB/MI Program Context
27467 @section @sc{gdb/mi} Program Context
27469 @subheading The @code{-exec-arguments} Command
27470 @findex -exec-arguments
27473 @subsubheading Synopsis
27476 -exec-arguments @var{args}
27479 Set the inferior program arguments, to be used in the next
27482 @subsubheading @value{GDBN} Command
27484 The corresponding @value{GDBN} command is @samp{set args}.
27486 @subsubheading Example
27490 -exec-arguments -v word
27497 @subheading The @code{-exec-show-arguments} Command
27498 @findex -exec-show-arguments
27500 @subsubheading Synopsis
27503 -exec-show-arguments
27506 Print the arguments of the program.
27508 @subsubheading @value{GDBN} Command
27510 The corresponding @value{GDBN} command is @samp{show args}.
27512 @subsubheading Example
27517 @subheading The @code{-environment-cd} Command
27518 @findex -environment-cd
27520 @subsubheading Synopsis
27523 -environment-cd @var{pathdir}
27526 Set @value{GDBN}'s working directory.
27528 @subsubheading @value{GDBN} Command
27530 The corresponding @value{GDBN} command is @samp{cd}.
27532 @subsubheading Example
27536 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27542 @subheading The @code{-environment-directory} Command
27543 @findex -environment-directory
27545 @subsubheading Synopsis
27548 -environment-directory [ -r ] [ @var{pathdir} ]+
27551 Add directories @var{pathdir} to beginning of search path for source files.
27552 If the @samp{-r} option is used, the search path is reset to the default
27553 search path. If directories @var{pathdir} are supplied in addition to the
27554 @samp{-r} option, the search path is first reset and then addition
27556 Multiple directories may be specified, separated by blanks. Specifying
27557 multiple directories in a single command
27558 results in the directories added to the beginning of the
27559 search path in the same order they were presented in the command.
27560 If blanks are needed as
27561 part of a directory name, double-quotes should be used around
27562 the name. In the command output, the path will show up separated
27563 by the system directory-separator character. The directory-separator
27564 character must not be used
27565 in any directory name.
27566 If no directories are specified, the current search path is displayed.
27568 @subsubheading @value{GDBN} Command
27570 The corresponding @value{GDBN} command is @samp{dir}.
27572 @subsubheading Example
27576 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27577 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27579 -environment-directory ""
27580 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27582 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27583 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27585 -environment-directory -r
27586 ^done,source-path="$cdir:$cwd"
27591 @subheading The @code{-environment-path} Command
27592 @findex -environment-path
27594 @subsubheading Synopsis
27597 -environment-path [ -r ] [ @var{pathdir} ]+
27600 Add directories @var{pathdir} to beginning of search path for object files.
27601 If the @samp{-r} option is used, the search path is reset to the original
27602 search path that existed at gdb start-up. If directories @var{pathdir} are
27603 supplied in addition to the
27604 @samp{-r} option, the search path is first reset and then addition
27606 Multiple directories may be specified, separated by blanks. Specifying
27607 multiple directories in a single command
27608 results in the directories added to the beginning of the
27609 search path in the same order they were presented in the command.
27610 If blanks are needed as
27611 part of a directory name, double-quotes should be used around
27612 the name. In the command output, the path will show up separated
27613 by the system directory-separator character. The directory-separator
27614 character must not be used
27615 in any directory name.
27616 If no directories are specified, the current path is displayed.
27619 @subsubheading @value{GDBN} Command
27621 The corresponding @value{GDBN} command is @samp{path}.
27623 @subsubheading Example
27628 ^done,path="/usr/bin"
27630 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27631 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27633 -environment-path -r /usr/local/bin
27634 ^done,path="/usr/local/bin:/usr/bin"
27639 @subheading The @code{-environment-pwd} Command
27640 @findex -environment-pwd
27642 @subsubheading Synopsis
27648 Show the current working directory.
27650 @subsubheading @value{GDBN} Command
27652 The corresponding @value{GDBN} command is @samp{pwd}.
27654 @subsubheading Example
27659 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27663 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27664 @node GDB/MI Thread Commands
27665 @section @sc{gdb/mi} Thread Commands
27668 @subheading The @code{-thread-info} Command
27669 @findex -thread-info
27671 @subsubheading Synopsis
27674 -thread-info [ @var{thread-id} ]
27677 Reports information about either a specific thread, if the
27678 @var{thread-id} parameter is present, or about all threads.
27679 @var{thread-id} is the thread's global thread ID. When printing
27680 information about all threads, also reports the global ID of the
27683 @subsubheading @value{GDBN} Command
27685 The @samp{info thread} command prints the same information
27688 @subsubheading Result
27690 The result is a list of threads. The following attributes are
27691 defined for a given thread:
27695 This field exists only for the current thread. It has the value @samp{*}.
27698 The global identifier that @value{GDBN} uses to refer to the thread.
27701 The identifier that the target uses to refer to the thread.
27704 Extra information about the thread, in a target-specific format. This
27708 The name of the thread. If the user specified a name using the
27709 @code{thread name} command, then this name is given. Otherwise, if
27710 @value{GDBN} can extract the thread name from the target, then that
27711 name is given. If @value{GDBN} cannot find the thread name, then this
27715 The stack frame currently executing in the thread.
27718 The thread's state. The @samp{state} field may have the following
27723 The thread is stopped. Frame information is available for stopped
27727 The thread is running. There's no frame information for running
27733 If @value{GDBN} can find the CPU core on which this thread is running,
27734 then this field is the core identifier. This field is optional.
27738 @subsubheading Example
27743 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27744 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27745 args=[]@},state="running"@},
27746 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27747 frame=@{level="0",addr="0x0804891f",func="foo",
27748 args=[@{name="i",value="10"@}],
27749 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27750 state="running"@}],
27751 current-thread-id="1"
27755 @subheading The @code{-thread-list-ids} Command
27756 @findex -thread-list-ids
27758 @subsubheading Synopsis
27764 Produces a list of the currently known global @value{GDBN} thread ids.
27765 At the end of the list it also prints the total number of such
27768 This command is retained for historical reasons, the
27769 @code{-thread-info} command should be used instead.
27771 @subsubheading @value{GDBN} Command
27773 Part of @samp{info threads} supplies the same information.
27775 @subsubheading Example
27780 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27781 current-thread-id="1",number-of-threads="3"
27786 @subheading The @code{-thread-select} Command
27787 @findex -thread-select
27789 @subsubheading Synopsis
27792 -thread-select @var{thread-id}
27795 Make thread with global thread number @var{thread-id} the current
27796 thread. It prints the number of the new current thread, and the
27797 topmost frame for that thread.
27799 This command is deprecated in favor of explicitly using the
27800 @samp{--thread} option to each command.
27802 @subsubheading @value{GDBN} Command
27804 The corresponding @value{GDBN} command is @samp{thread}.
27806 @subsubheading Example
27813 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27814 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27818 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27819 number-of-threads="3"
27822 ^done,new-thread-id="3",
27823 frame=@{level="0",func="vprintf",
27824 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27825 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27830 @node GDB/MI Ada Tasking Commands
27831 @section @sc{gdb/mi} Ada Tasking Commands
27833 @subheading The @code{-ada-task-info} Command
27834 @findex -ada-task-info
27836 @subsubheading Synopsis
27839 -ada-task-info [ @var{task-id} ]
27842 Reports information about either a specific Ada task, if the
27843 @var{task-id} parameter is present, or about all Ada tasks.
27845 @subsubheading @value{GDBN} Command
27847 The @samp{info tasks} command prints the same information
27848 about all Ada tasks (@pxref{Ada Tasks}).
27850 @subsubheading Result
27852 The result is a table of Ada tasks. The following columns are
27853 defined for each Ada task:
27857 This field exists only for the current thread. It has the value @samp{*}.
27860 The identifier that @value{GDBN} uses to refer to the Ada task.
27863 The identifier that the target uses to refer to the Ada task.
27866 The global thread identifier of the thread corresponding to the Ada
27869 This field should always exist, as Ada tasks are always implemented
27870 on top of a thread. But if @value{GDBN} cannot find this corresponding
27871 thread for any reason, the field is omitted.
27874 This field exists only when the task was created by another task.
27875 In this case, it provides the ID of the parent task.
27878 The base priority of the task.
27881 The current state of the task. For a detailed description of the
27882 possible states, see @ref{Ada Tasks}.
27885 The name of the task.
27889 @subsubheading Example
27893 ^done,tasks=@{nr_rows="3",nr_cols="8",
27894 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27895 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27896 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27897 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27898 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27899 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27900 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27901 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27902 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27903 state="Child Termination Wait",name="main_task"@}]@}
27907 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27908 @node GDB/MI Program Execution
27909 @section @sc{gdb/mi} Program Execution
27911 These are the asynchronous commands which generate the out-of-band
27912 record @samp{*stopped}. Currently @value{GDBN} only really executes
27913 asynchronously with remote targets and this interaction is mimicked in
27916 @subheading The @code{-exec-continue} Command
27917 @findex -exec-continue
27919 @subsubheading Synopsis
27922 -exec-continue [--reverse] [--all|--thread-group N]
27925 Resumes the execution of the inferior program, which will continue
27926 to execute until it reaches a debugger stop event. If the
27927 @samp{--reverse} option is specified, execution resumes in reverse until
27928 it reaches a stop event. Stop events may include
27931 breakpoints or watchpoints
27933 signals or exceptions
27935 the end of the process (or its beginning under @samp{--reverse})
27937 the end or beginning of a replay log if one is being used.
27939 In all-stop mode (@pxref{All-Stop
27940 Mode}), may resume only one thread, or all threads, depending on the
27941 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27942 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27943 ignored in all-stop mode. If the @samp{--thread-group} options is
27944 specified, then all threads in that thread group are resumed.
27946 @subsubheading @value{GDBN} Command
27948 The corresponding @value{GDBN} corresponding is @samp{continue}.
27950 @subsubheading Example
27957 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27958 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27964 @subheading The @code{-exec-finish} Command
27965 @findex -exec-finish
27967 @subsubheading Synopsis
27970 -exec-finish [--reverse]
27973 Resumes the execution of the inferior program until the current
27974 function is exited. Displays the results returned by the function.
27975 If the @samp{--reverse} option is specified, resumes the reverse
27976 execution of the inferior program until the point where current
27977 function was called.
27979 @subsubheading @value{GDBN} Command
27981 The corresponding @value{GDBN} command is @samp{finish}.
27983 @subsubheading Example
27985 Function returning @code{void}.
27992 *stopped,reason="function-finished",frame=@{func="main",args=[],
27993 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27997 Function returning other than @code{void}. The name of the internal
27998 @value{GDBN} variable storing the result is printed, together with the
28005 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
28006 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
28007 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28008 gdb-result-var="$1",return-value="0"
28013 @subheading The @code{-exec-interrupt} Command
28014 @findex -exec-interrupt
28016 @subsubheading Synopsis
28019 -exec-interrupt [--all|--thread-group N]
28022 Interrupts the background execution of the target. Note how the token
28023 associated with the stop message is the one for the execution command
28024 that has been interrupted. The token for the interrupt itself only
28025 appears in the @samp{^done} output. If the user is trying to
28026 interrupt a non-running program, an error message will be printed.
28028 Note that when asynchronous execution is enabled, this command is
28029 asynchronous just like other execution commands. That is, first the
28030 @samp{^done} response will be printed, and the target stop will be
28031 reported after that using the @samp{*stopped} notification.
28033 In non-stop mode, only the context thread is interrupted by default.
28034 All threads (in all inferiors) will be interrupted if the
28035 @samp{--all} option is specified. If the @samp{--thread-group}
28036 option is specified, all threads in that group will be interrupted.
28038 @subsubheading @value{GDBN} Command
28040 The corresponding @value{GDBN} command is @samp{interrupt}.
28042 @subsubheading Example
28053 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
28054 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
28055 fullname="/home/foo/bar/try.c",line="13"@}
28060 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
28064 @subheading The @code{-exec-jump} Command
28067 @subsubheading Synopsis
28070 -exec-jump @var{location}
28073 Resumes execution of the inferior program at the location specified by
28074 parameter. @xref{Specify Location}, for a description of the
28075 different forms of @var{location}.
28077 @subsubheading @value{GDBN} Command
28079 The corresponding @value{GDBN} command is @samp{jump}.
28081 @subsubheading Example
28084 -exec-jump foo.c:10
28085 *running,thread-id="all"
28090 @subheading The @code{-exec-next} Command
28093 @subsubheading Synopsis
28096 -exec-next [--reverse]
28099 Resumes execution of the inferior program, stopping when the beginning
28100 of the next source line is reached.
28102 If the @samp{--reverse} option is specified, resumes reverse execution
28103 of the inferior program, stopping at the beginning of the previous
28104 source line. If you issue this command on the first line of a
28105 function, it will take you back to the caller of that function, to the
28106 source line where the function was called.
28109 @subsubheading @value{GDBN} Command
28111 The corresponding @value{GDBN} command is @samp{next}.
28113 @subsubheading Example
28119 *stopped,reason="end-stepping-range",line="8",file="hello.c"
28124 @subheading The @code{-exec-next-instruction} Command
28125 @findex -exec-next-instruction
28127 @subsubheading Synopsis
28130 -exec-next-instruction [--reverse]
28133 Executes one machine instruction. If the instruction is a function
28134 call, continues until the function returns. If the program stops at an
28135 instruction in the middle of a source line, the address will be
28138 If the @samp{--reverse} option is specified, resumes reverse execution
28139 of the inferior program, stopping at the previous instruction. If the
28140 previously executed instruction was a return from another function,
28141 it will continue to execute in reverse until the call to that function
28142 (from the current stack frame) is reached.
28144 @subsubheading @value{GDBN} Command
28146 The corresponding @value{GDBN} command is @samp{nexti}.
28148 @subsubheading Example
28152 -exec-next-instruction
28156 *stopped,reason="end-stepping-range",
28157 addr="0x000100d4",line="5",file="hello.c"
28162 @subheading The @code{-exec-return} Command
28163 @findex -exec-return
28165 @subsubheading Synopsis
28171 Makes current function return immediately. Doesn't execute the inferior.
28172 Displays the new current frame.
28174 @subsubheading @value{GDBN} Command
28176 The corresponding @value{GDBN} command is @samp{return}.
28178 @subsubheading Example
28182 200-break-insert callee4
28183 200^done,bkpt=@{number="1",addr="0x00010734",
28184 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28189 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28190 frame=@{func="callee4",args=[],
28191 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28192 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28198 111^done,frame=@{level="0",func="callee3",
28199 args=[@{name="strarg",
28200 value="0x11940 \"A string argument.\""@}],
28201 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28202 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28207 @subheading The @code{-exec-run} Command
28210 @subsubheading Synopsis
28213 -exec-run [ --all | --thread-group N ] [ --start ]
28216 Starts execution of the inferior from the beginning. The inferior
28217 executes until either a breakpoint is encountered or the program
28218 exits. In the latter case the output will include an exit code, if
28219 the program has exited exceptionally.
28221 When neither the @samp{--all} nor the @samp{--thread-group} option
28222 is specified, the current inferior is started. If the
28223 @samp{--thread-group} option is specified, it should refer to a thread
28224 group of type @samp{process}, and that thread group will be started.
28225 If the @samp{--all} option is specified, then all inferiors will be started.
28227 Using the @samp{--start} option instructs the debugger to stop
28228 the execution at the start of the inferior's main subprogram,
28229 following the same behavior as the @code{start} command
28230 (@pxref{Starting}).
28232 @subsubheading @value{GDBN} Command
28234 The corresponding @value{GDBN} command is @samp{run}.
28236 @subsubheading Examples
28241 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28246 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28247 frame=@{func="main",args=[],file="recursive2.c",
28248 fullname="/home/foo/bar/recursive2.c",line="4"@}
28253 Program exited normally:
28261 *stopped,reason="exited-normally"
28266 Program exited exceptionally:
28274 *stopped,reason="exited",exit-code="01"
28278 Another way the program can terminate is if it receives a signal such as
28279 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28283 *stopped,reason="exited-signalled",signal-name="SIGINT",
28284 signal-meaning="Interrupt"
28288 @c @subheading -exec-signal
28291 @subheading The @code{-exec-step} Command
28294 @subsubheading Synopsis
28297 -exec-step [--reverse]
28300 Resumes execution of the inferior program, stopping when the beginning
28301 of the next source line is reached, if the next source line is not a
28302 function call. If it is, stop at the first instruction of the called
28303 function. If the @samp{--reverse} option is specified, resumes reverse
28304 execution of the inferior program, stopping at the beginning of the
28305 previously executed source line.
28307 @subsubheading @value{GDBN} Command
28309 The corresponding @value{GDBN} command is @samp{step}.
28311 @subsubheading Example
28313 Stepping into a function:
28319 *stopped,reason="end-stepping-range",
28320 frame=@{func="foo",args=[@{name="a",value="10"@},
28321 @{name="b",value="0"@}],file="recursive2.c",
28322 fullname="/home/foo/bar/recursive2.c",line="11"@}
28332 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28337 @subheading The @code{-exec-step-instruction} Command
28338 @findex -exec-step-instruction
28340 @subsubheading Synopsis
28343 -exec-step-instruction [--reverse]
28346 Resumes the inferior which executes one machine instruction. If the
28347 @samp{--reverse} option is specified, resumes reverse execution of the
28348 inferior program, stopping at the previously executed instruction.
28349 The output, once @value{GDBN} has stopped, will vary depending on
28350 whether we have stopped in the middle of a source line or not. In the
28351 former case, the address at which the program stopped will be printed
28354 @subsubheading @value{GDBN} Command
28356 The corresponding @value{GDBN} command is @samp{stepi}.
28358 @subsubheading Example
28362 -exec-step-instruction
28366 *stopped,reason="end-stepping-range",
28367 frame=@{func="foo",args=[],file="try.c",
28368 fullname="/home/foo/bar/try.c",line="10"@}
28370 -exec-step-instruction
28374 *stopped,reason="end-stepping-range",
28375 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28376 fullname="/home/foo/bar/try.c",line="10"@}
28381 @subheading The @code{-exec-until} Command
28382 @findex -exec-until
28384 @subsubheading Synopsis
28387 -exec-until [ @var{location} ]
28390 Executes the inferior until the @var{location} specified in the
28391 argument is reached. If there is no argument, the inferior executes
28392 until a source line greater than the current one is reached. The
28393 reason for stopping in this case will be @samp{location-reached}.
28395 @subsubheading @value{GDBN} Command
28397 The corresponding @value{GDBN} command is @samp{until}.
28399 @subsubheading Example
28403 -exec-until recursive2.c:6
28407 *stopped,reason="location-reached",frame=@{func="main",args=[],
28408 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28413 @subheading -file-clear
28414 Is this going away????
28417 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28418 @node GDB/MI Stack Manipulation
28419 @section @sc{gdb/mi} Stack Manipulation Commands
28421 @subheading The @code{-enable-frame-filters} Command
28422 @findex -enable-frame-filters
28425 -enable-frame-filters
28428 @value{GDBN} allows Python-based frame filters to affect the output of
28429 the MI commands relating to stack traces. As there is no way to
28430 implement this in a fully backward-compatible way, a front end must
28431 request that this functionality be enabled.
28433 Once enabled, this feature cannot be disabled.
28435 Note that if Python support has not been compiled into @value{GDBN},
28436 this command will still succeed (and do nothing).
28438 @subheading The @code{-stack-info-frame} Command
28439 @findex -stack-info-frame
28441 @subsubheading Synopsis
28447 Get info on the selected frame.
28449 @subsubheading @value{GDBN} Command
28451 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28452 (without arguments).
28454 @subsubheading Example
28459 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28460 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28461 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28465 @subheading The @code{-stack-info-depth} Command
28466 @findex -stack-info-depth
28468 @subsubheading Synopsis
28471 -stack-info-depth [ @var{max-depth} ]
28474 Return the depth of the stack. If the integer argument @var{max-depth}
28475 is specified, do not count beyond @var{max-depth} frames.
28477 @subsubheading @value{GDBN} Command
28479 There's no equivalent @value{GDBN} command.
28481 @subsubheading Example
28483 For a stack with frame levels 0 through 11:
28490 -stack-info-depth 4
28493 -stack-info-depth 12
28496 -stack-info-depth 11
28499 -stack-info-depth 13
28504 @anchor{-stack-list-arguments}
28505 @subheading The @code{-stack-list-arguments} Command
28506 @findex -stack-list-arguments
28508 @subsubheading Synopsis
28511 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28512 [ @var{low-frame} @var{high-frame} ]
28515 Display a list of the arguments for the frames between @var{low-frame}
28516 and @var{high-frame} (inclusive). If @var{low-frame} and
28517 @var{high-frame} are not provided, list the arguments for the whole
28518 call stack. If the two arguments are equal, show the single frame
28519 at the corresponding level. It is an error if @var{low-frame} is
28520 larger than the actual number of frames. On the other hand,
28521 @var{high-frame} may be larger than the actual number of frames, in
28522 which case only existing frames will be returned.
28524 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28525 the variables; if it is 1 or @code{--all-values}, print also their
28526 values; and if it is 2 or @code{--simple-values}, print the name,
28527 type and value for simple data types, and the name and type for arrays,
28528 structures and unions. If the option @code{--no-frame-filters} is
28529 supplied, then Python frame filters will not be executed.
28531 If the @code{--skip-unavailable} option is specified, arguments that
28532 are not available are not listed. Partially available arguments
28533 are still displayed, however.
28535 Use of this command to obtain arguments in a single frame is
28536 deprecated in favor of the @samp{-stack-list-variables} command.
28538 @subsubheading @value{GDBN} Command
28540 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28541 @samp{gdb_get_args} command which partially overlaps with the
28542 functionality of @samp{-stack-list-arguments}.
28544 @subsubheading Example
28551 frame=@{level="0",addr="0x00010734",func="callee4",
28552 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28553 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28554 frame=@{level="1",addr="0x0001076c",func="callee3",
28555 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28556 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28557 frame=@{level="2",addr="0x0001078c",func="callee2",
28558 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28559 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28560 frame=@{level="3",addr="0x000107b4",func="callee1",
28561 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28562 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28563 frame=@{level="4",addr="0x000107e0",func="main",
28564 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28565 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28567 -stack-list-arguments 0
28570 frame=@{level="0",args=[]@},
28571 frame=@{level="1",args=[name="strarg"]@},
28572 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28573 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28574 frame=@{level="4",args=[]@}]
28576 -stack-list-arguments 1
28579 frame=@{level="0",args=[]@},
28581 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28582 frame=@{level="2",args=[
28583 @{name="intarg",value="2"@},
28584 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28585 @{frame=@{level="3",args=[
28586 @{name="intarg",value="2"@},
28587 @{name="strarg",value="0x11940 \"A string argument.\""@},
28588 @{name="fltarg",value="3.5"@}]@},
28589 frame=@{level="4",args=[]@}]
28591 -stack-list-arguments 0 2 2
28592 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28594 -stack-list-arguments 1 2 2
28595 ^done,stack-args=[frame=@{level="2",
28596 args=[@{name="intarg",value="2"@},
28597 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28601 @c @subheading -stack-list-exception-handlers
28604 @anchor{-stack-list-frames}
28605 @subheading The @code{-stack-list-frames} Command
28606 @findex -stack-list-frames
28608 @subsubheading Synopsis
28611 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
28614 List the frames currently on the stack. For each frame it displays the
28619 The frame number, 0 being the topmost frame, i.e., the innermost function.
28621 The @code{$pc} value for that frame.
28625 File name of the source file where the function lives.
28626 @item @var{fullname}
28627 The full file name of the source file where the function lives.
28629 Line number corresponding to the @code{$pc}.
28631 The shared library where this function is defined. This is only given
28632 if the frame's function is not known.
28635 If invoked without arguments, this command prints a backtrace for the
28636 whole stack. If given two integer arguments, it shows the frames whose
28637 levels are between the two arguments (inclusive). If the two arguments
28638 are equal, it shows the single frame at the corresponding level. It is
28639 an error if @var{low-frame} is larger than the actual number of
28640 frames. On the other hand, @var{high-frame} may be larger than the
28641 actual number of frames, in which case only existing frames will be
28642 returned. If the option @code{--no-frame-filters} is supplied, then
28643 Python frame filters will not be executed.
28645 @subsubheading @value{GDBN} Command
28647 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28649 @subsubheading Example
28651 Full stack backtrace:
28657 [frame=@{level="0",addr="0x0001076c",func="foo",
28658 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28659 frame=@{level="1",addr="0x000107a4",func="foo",
28660 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28661 frame=@{level="2",addr="0x000107a4",func="foo",
28662 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28663 frame=@{level="3",addr="0x000107a4",func="foo",
28664 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28665 frame=@{level="4",addr="0x000107a4",func="foo",
28666 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28667 frame=@{level="5",addr="0x000107a4",func="foo",
28668 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28669 frame=@{level="6",addr="0x000107a4",func="foo",
28670 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28671 frame=@{level="7",addr="0x000107a4",func="foo",
28672 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28673 frame=@{level="8",addr="0x000107a4",func="foo",
28674 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28675 frame=@{level="9",addr="0x000107a4",func="foo",
28676 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28677 frame=@{level="10",addr="0x000107a4",func="foo",
28678 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28679 frame=@{level="11",addr="0x00010738",func="main",
28680 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28684 Show frames between @var{low_frame} and @var{high_frame}:
28688 -stack-list-frames 3 5
28690 [frame=@{level="3",addr="0x000107a4",func="foo",
28691 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28692 frame=@{level="4",addr="0x000107a4",func="foo",
28693 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28694 frame=@{level="5",addr="0x000107a4",func="foo",
28695 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28699 Show a single frame:
28703 -stack-list-frames 3 3
28705 [frame=@{level="3",addr="0x000107a4",func="foo",
28706 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28711 @subheading The @code{-stack-list-locals} Command
28712 @findex -stack-list-locals
28713 @anchor{-stack-list-locals}
28715 @subsubheading Synopsis
28718 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28721 Display the local variable names for the selected frame. If
28722 @var{print-values} is 0 or @code{--no-values}, print only the names of
28723 the variables; if it is 1 or @code{--all-values}, print also their
28724 values; and if it is 2 or @code{--simple-values}, print the name,
28725 type and value for simple data types, and the name and type for arrays,
28726 structures and unions. In this last case, a frontend can immediately
28727 display the value of simple data types and create variable objects for
28728 other data types when the user wishes to explore their values in
28729 more detail. If the option @code{--no-frame-filters} is supplied, then
28730 Python frame filters will not be executed.
28732 If the @code{--skip-unavailable} option is specified, local variables
28733 that are not available are not listed. Partially available local
28734 variables are still displayed, however.
28736 This command is deprecated in favor of the
28737 @samp{-stack-list-variables} command.
28739 @subsubheading @value{GDBN} Command
28741 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28743 @subsubheading Example
28747 -stack-list-locals 0
28748 ^done,locals=[name="A",name="B",name="C"]
28750 -stack-list-locals --all-values
28751 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28752 @{name="C",value="@{1, 2, 3@}"@}]
28753 -stack-list-locals --simple-values
28754 ^done,locals=[@{name="A",type="int",value="1"@},
28755 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28759 @anchor{-stack-list-variables}
28760 @subheading The @code{-stack-list-variables} Command
28761 @findex -stack-list-variables
28763 @subsubheading Synopsis
28766 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
28769 Display the names of local variables and function arguments for the selected frame. If
28770 @var{print-values} is 0 or @code{--no-values}, print only the names of
28771 the variables; if it is 1 or @code{--all-values}, print also their
28772 values; and if it is 2 or @code{--simple-values}, print the name,
28773 type and value for simple data types, and the name and type for arrays,
28774 structures and unions. If the option @code{--no-frame-filters} is
28775 supplied, then Python frame filters will not be executed.
28777 If the @code{--skip-unavailable} option is specified, local variables
28778 and arguments that are not available are not listed. Partially
28779 available arguments and local variables are still displayed, however.
28781 @subsubheading Example
28785 -stack-list-variables --thread 1 --frame 0 --all-values
28786 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28791 @subheading The @code{-stack-select-frame} Command
28792 @findex -stack-select-frame
28794 @subsubheading Synopsis
28797 -stack-select-frame @var{framenum}
28800 Change the selected frame. Select a different frame @var{framenum} on
28803 This command in deprecated in favor of passing the @samp{--frame}
28804 option to every command.
28806 @subsubheading @value{GDBN} Command
28808 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28809 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28811 @subsubheading Example
28815 -stack-select-frame 2
28820 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28821 @node GDB/MI Variable Objects
28822 @section @sc{gdb/mi} Variable Objects
28826 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28828 For the implementation of a variable debugger window (locals, watched
28829 expressions, etc.), we are proposing the adaptation of the existing code
28830 used by @code{Insight}.
28832 The two main reasons for that are:
28836 It has been proven in practice (it is already on its second generation).
28839 It will shorten development time (needless to say how important it is
28843 The original interface was designed to be used by Tcl code, so it was
28844 slightly changed so it could be used through @sc{gdb/mi}. This section
28845 describes the @sc{gdb/mi} operations that will be available and gives some
28846 hints about their use.
28848 @emph{Note}: In addition to the set of operations described here, we
28849 expect the @sc{gui} implementation of a variable window to require, at
28850 least, the following operations:
28853 @item @code{-gdb-show} @code{output-radix}
28854 @item @code{-stack-list-arguments}
28855 @item @code{-stack-list-locals}
28856 @item @code{-stack-select-frame}
28861 @subheading Introduction to Variable Objects
28863 @cindex variable objects in @sc{gdb/mi}
28865 Variable objects are "object-oriented" MI interface for examining and
28866 changing values of expressions. Unlike some other MI interfaces that
28867 work with expressions, variable objects are specifically designed for
28868 simple and efficient presentation in the frontend. A variable object
28869 is identified by string name. When a variable object is created, the
28870 frontend specifies the expression for that variable object. The
28871 expression can be a simple variable, or it can be an arbitrary complex
28872 expression, and can even involve CPU registers. After creating a
28873 variable object, the frontend can invoke other variable object
28874 operations---for example to obtain or change the value of a variable
28875 object, or to change display format.
28877 Variable objects have hierarchical tree structure. Any variable object
28878 that corresponds to a composite type, such as structure in C, has
28879 a number of child variable objects, for example corresponding to each
28880 element of a structure. A child variable object can itself have
28881 children, recursively. Recursion ends when we reach
28882 leaf variable objects, which always have built-in types. Child variable
28883 objects are created only by explicit request, so if a frontend
28884 is not interested in the children of a particular variable object, no
28885 child will be created.
28887 For a leaf variable object it is possible to obtain its value as a
28888 string, or set the value from a string. String value can be also
28889 obtained for a non-leaf variable object, but it's generally a string
28890 that only indicates the type of the object, and does not list its
28891 contents. Assignment to a non-leaf variable object is not allowed.
28893 A frontend does not need to read the values of all variable objects each time
28894 the program stops. Instead, MI provides an update command that lists all
28895 variable objects whose values has changed since the last update
28896 operation. This considerably reduces the amount of data that must
28897 be transferred to the frontend. As noted above, children variable
28898 objects are created on demand, and only leaf variable objects have a
28899 real value. As result, gdb will read target memory only for leaf
28900 variables that frontend has created.
28902 The automatic update is not always desirable. For example, a frontend
28903 might want to keep a value of some expression for future reference,
28904 and never update it. For another example, fetching memory is
28905 relatively slow for embedded targets, so a frontend might want
28906 to disable automatic update for the variables that are either not
28907 visible on the screen, or ``closed''. This is possible using so
28908 called ``frozen variable objects''. Such variable objects are never
28909 implicitly updated.
28911 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28912 fixed variable object, the expression is parsed when the variable
28913 object is created, including associating identifiers to specific
28914 variables. The meaning of expression never changes. For a floating
28915 variable object the values of variables whose names appear in the
28916 expressions are re-evaluated every time in the context of the current
28917 frame. Consider this example:
28922 struct work_state state;
28929 If a fixed variable object for the @code{state} variable is created in
28930 this function, and we enter the recursive call, the variable
28931 object will report the value of @code{state} in the top-level
28932 @code{do_work} invocation. On the other hand, a floating variable
28933 object will report the value of @code{state} in the current frame.
28935 If an expression specified when creating a fixed variable object
28936 refers to a local variable, the variable object becomes bound to the
28937 thread and frame in which the variable object is created. When such
28938 variable object is updated, @value{GDBN} makes sure that the
28939 thread/frame combination the variable object is bound to still exists,
28940 and re-evaluates the variable object in context of that thread/frame.
28942 The following is the complete set of @sc{gdb/mi} operations defined to
28943 access this functionality:
28945 @multitable @columnfractions .4 .6
28946 @item @strong{Operation}
28947 @tab @strong{Description}
28949 @item @code{-enable-pretty-printing}
28950 @tab enable Python-based pretty-printing
28951 @item @code{-var-create}
28952 @tab create a variable object
28953 @item @code{-var-delete}
28954 @tab delete the variable object and/or its children
28955 @item @code{-var-set-format}
28956 @tab set the display format of this variable
28957 @item @code{-var-show-format}
28958 @tab show the display format of this variable
28959 @item @code{-var-info-num-children}
28960 @tab tells how many children this object has
28961 @item @code{-var-list-children}
28962 @tab return a list of the object's children
28963 @item @code{-var-info-type}
28964 @tab show the type of this variable object
28965 @item @code{-var-info-expression}
28966 @tab print parent-relative expression that this variable object represents
28967 @item @code{-var-info-path-expression}
28968 @tab print full expression that this variable object represents
28969 @item @code{-var-show-attributes}
28970 @tab is this variable editable? does it exist here?
28971 @item @code{-var-evaluate-expression}
28972 @tab get the value of this variable
28973 @item @code{-var-assign}
28974 @tab set the value of this variable
28975 @item @code{-var-update}
28976 @tab update the variable and its children
28977 @item @code{-var-set-frozen}
28978 @tab set frozeness attribute
28979 @item @code{-var-set-update-range}
28980 @tab set range of children to display on update
28983 In the next subsection we describe each operation in detail and suggest
28984 how it can be used.
28986 @subheading Description And Use of Operations on Variable Objects
28988 @subheading The @code{-enable-pretty-printing} Command
28989 @findex -enable-pretty-printing
28992 -enable-pretty-printing
28995 @value{GDBN} allows Python-based visualizers to affect the output of the
28996 MI variable object commands. However, because there was no way to
28997 implement this in a fully backward-compatible way, a front end must
28998 request that this functionality be enabled.
29000 Once enabled, this feature cannot be disabled.
29002 Note that if Python support has not been compiled into @value{GDBN},
29003 this command will still succeed (and do nothing).
29005 This feature is currently (as of @value{GDBN} 7.0) experimental, and
29006 may work differently in future versions of @value{GDBN}.
29008 @subheading The @code{-var-create} Command
29009 @findex -var-create
29011 @subsubheading Synopsis
29014 -var-create @{@var{name} | "-"@}
29015 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
29018 This operation creates a variable object, which allows the monitoring of
29019 a variable, the result of an expression, a memory cell or a CPU
29022 The @var{name} parameter is the string by which the object can be
29023 referenced. It must be unique. If @samp{-} is specified, the varobj
29024 system will generate a string ``varNNNNNN'' automatically. It will be
29025 unique provided that one does not specify @var{name} of that format.
29026 The command fails if a duplicate name is found.
29028 The frame under which the expression should be evaluated can be
29029 specified by @var{frame-addr}. A @samp{*} indicates that the current
29030 frame should be used. A @samp{@@} indicates that a floating variable
29031 object must be created.
29033 @var{expression} is any expression valid on the current language set (must not
29034 begin with a @samp{*}), or one of the following:
29038 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
29041 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
29044 @samp{$@var{regname}} --- a CPU register name
29047 @cindex dynamic varobj
29048 A varobj's contents may be provided by a Python-based pretty-printer. In this
29049 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
29050 have slightly different semantics in some cases. If the
29051 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
29052 will never create a dynamic varobj. This ensures backward
29053 compatibility for existing clients.
29055 @subsubheading Result
29057 This operation returns attributes of the newly-created varobj. These
29062 The name of the varobj.
29065 The number of children of the varobj. This number is not necessarily
29066 reliable for a dynamic varobj. Instead, you must examine the
29067 @samp{has_more} attribute.
29070 The varobj's scalar value. For a varobj whose type is some sort of
29071 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
29072 will not be interesting.
29075 The varobj's type. This is a string representation of the type, as
29076 would be printed by the @value{GDBN} CLI. If @samp{print object}
29077 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29078 @emph{actual} (derived) type of the object is shown rather than the
29079 @emph{declared} one.
29082 If a variable object is bound to a specific thread, then this is the
29083 thread's global identifier.
29086 For a dynamic varobj, this indicates whether there appear to be any
29087 children available. For a non-dynamic varobj, this will be 0.
29090 This attribute will be present and have the value @samp{1} if the
29091 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29092 then this attribute will not be present.
29095 A dynamic varobj can supply a display hint to the front end. The
29096 value comes directly from the Python pretty-printer object's
29097 @code{display_hint} method. @xref{Pretty Printing API}.
29100 Typical output will look like this:
29103 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
29104 has_more="@var{has_more}"
29108 @subheading The @code{-var-delete} Command
29109 @findex -var-delete
29111 @subsubheading Synopsis
29114 -var-delete [ -c ] @var{name}
29117 Deletes a previously created variable object and all of its children.
29118 With the @samp{-c} option, just deletes the children.
29120 Returns an error if the object @var{name} is not found.
29123 @subheading The @code{-var-set-format} Command
29124 @findex -var-set-format
29126 @subsubheading Synopsis
29129 -var-set-format @var{name} @var{format-spec}
29132 Sets the output format for the value of the object @var{name} to be
29135 @anchor{-var-set-format}
29136 The syntax for the @var{format-spec} is as follows:
29139 @var{format-spec} @expansion{}
29140 @{binary | decimal | hexadecimal | octal | natural | zero-hexadecimal@}
29143 The natural format is the default format choosen automatically
29144 based on the variable type (like decimal for an @code{int}, hex
29145 for pointers, etc.).
29147 The zero-hexadecimal format has a representation similar to hexadecimal
29148 but with padding zeroes to the left of the value. For example, a 32-bit
29149 hexadecimal value of 0x1234 would be represented as 0x00001234 in the
29150 zero-hexadecimal format.
29152 For a variable with children, the format is set only on the
29153 variable itself, and the children are not affected.
29155 @subheading The @code{-var-show-format} Command
29156 @findex -var-show-format
29158 @subsubheading Synopsis
29161 -var-show-format @var{name}
29164 Returns the format used to display the value of the object @var{name}.
29167 @var{format} @expansion{}
29172 @subheading The @code{-var-info-num-children} Command
29173 @findex -var-info-num-children
29175 @subsubheading Synopsis
29178 -var-info-num-children @var{name}
29181 Returns the number of children of a variable object @var{name}:
29187 Note that this number is not completely reliable for a dynamic varobj.
29188 It will return the current number of children, but more children may
29192 @subheading The @code{-var-list-children} Command
29193 @findex -var-list-children
29195 @subsubheading Synopsis
29198 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29200 @anchor{-var-list-children}
29202 Return a list of the children of the specified variable object and
29203 create variable objects for them, if they do not already exist. With
29204 a single argument or if @var{print-values} has a value of 0 or
29205 @code{--no-values}, print only the names of the variables; if
29206 @var{print-values} is 1 or @code{--all-values}, also print their
29207 values; and if it is 2 or @code{--simple-values} print the name and
29208 value for simple data types and just the name for arrays, structures
29211 @var{from} and @var{to}, if specified, indicate the range of children
29212 to report. If @var{from} or @var{to} is less than zero, the range is
29213 reset and all children will be reported. Otherwise, children starting
29214 at @var{from} (zero-based) and up to and excluding @var{to} will be
29217 If a child range is requested, it will only affect the current call to
29218 @code{-var-list-children}, but not future calls to @code{-var-update}.
29219 For this, you must instead use @code{-var-set-update-range}. The
29220 intent of this approach is to enable a front end to implement any
29221 update approach it likes; for example, scrolling a view may cause the
29222 front end to request more children with @code{-var-list-children}, and
29223 then the front end could call @code{-var-set-update-range} with a
29224 different range to ensure that future updates are restricted to just
29227 For each child the following results are returned:
29232 Name of the variable object created for this child.
29235 The expression to be shown to the user by the front end to designate this child.
29236 For example this may be the name of a structure member.
29238 For a dynamic varobj, this value cannot be used to form an
29239 expression. There is no way to do this at all with a dynamic varobj.
29241 For C/C@t{++} structures there are several pseudo children returned to
29242 designate access qualifiers. For these pseudo children @var{exp} is
29243 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29244 type and value are not present.
29246 A dynamic varobj will not report the access qualifying
29247 pseudo-children, regardless of the language. This information is not
29248 available at all with a dynamic varobj.
29251 Number of children this child has. For a dynamic varobj, this will be
29255 The type of the child. If @samp{print object}
29256 (@pxref{Print Settings, set print object}) is set to @code{on}, the
29257 @emph{actual} (derived) type of the object is shown rather than the
29258 @emph{declared} one.
29261 If values were requested, this is the value.
29264 If this variable object is associated with a thread, this is the
29265 thread's global thread id. Otherwise this result is not present.
29268 If the variable object is frozen, this variable will be present with a value of 1.
29271 A dynamic varobj can supply a display hint to the front end. The
29272 value comes directly from the Python pretty-printer object's
29273 @code{display_hint} method. @xref{Pretty Printing API}.
29276 This attribute will be present and have the value @samp{1} if the
29277 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29278 then this attribute will not be present.
29282 The result may have its own attributes:
29286 A dynamic varobj can supply a display hint to the front end. The
29287 value comes directly from the Python pretty-printer object's
29288 @code{display_hint} method. @xref{Pretty Printing API}.
29291 This is an integer attribute which is nonzero if there are children
29292 remaining after the end of the selected range.
29295 @subsubheading Example
29299 -var-list-children n
29300 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29301 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29303 -var-list-children --all-values n
29304 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29305 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29309 @subheading The @code{-var-info-type} Command
29310 @findex -var-info-type
29312 @subsubheading Synopsis
29315 -var-info-type @var{name}
29318 Returns the type of the specified variable @var{name}. The type is
29319 returned as a string in the same format as it is output by the
29323 type=@var{typename}
29327 @subheading The @code{-var-info-expression} Command
29328 @findex -var-info-expression
29330 @subsubheading Synopsis
29333 -var-info-expression @var{name}
29336 Returns a string that is suitable for presenting this
29337 variable object in user interface. The string is generally
29338 not valid expression in the current language, and cannot be evaluated.
29340 For example, if @code{a} is an array, and variable object
29341 @code{A} was created for @code{a}, then we'll get this output:
29344 (gdb) -var-info-expression A.1
29345 ^done,lang="C",exp="1"
29349 Here, the value of @code{lang} is the language name, which can be
29350 found in @ref{Supported Languages}.
29352 Note that the output of the @code{-var-list-children} command also
29353 includes those expressions, so the @code{-var-info-expression} command
29356 @subheading The @code{-var-info-path-expression} Command
29357 @findex -var-info-path-expression
29359 @subsubheading Synopsis
29362 -var-info-path-expression @var{name}
29365 Returns an expression that can be evaluated in the current
29366 context and will yield the same value that a variable object has.
29367 Compare this with the @code{-var-info-expression} command, which
29368 result can be used only for UI presentation. Typical use of
29369 the @code{-var-info-path-expression} command is creating a
29370 watchpoint from a variable object.
29372 This command is currently not valid for children of a dynamic varobj,
29373 and will give an error when invoked on one.
29375 For example, suppose @code{C} is a C@t{++} class, derived from class
29376 @code{Base}, and that the @code{Base} class has a member called
29377 @code{m_size}. Assume a variable @code{c} is has the type of
29378 @code{C} and a variable object @code{C} was created for variable
29379 @code{c}. Then, we'll get this output:
29381 (gdb) -var-info-path-expression C.Base.public.m_size
29382 ^done,path_expr=((Base)c).m_size)
29385 @subheading The @code{-var-show-attributes} Command
29386 @findex -var-show-attributes
29388 @subsubheading Synopsis
29391 -var-show-attributes @var{name}
29394 List attributes of the specified variable object @var{name}:
29397 status=@var{attr} [ ( ,@var{attr} )* ]
29401 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29403 @subheading The @code{-var-evaluate-expression} Command
29404 @findex -var-evaluate-expression
29406 @subsubheading Synopsis
29409 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29412 Evaluates the expression that is represented by the specified variable
29413 object and returns its value as a string. The format of the string
29414 can be specified with the @samp{-f} option. The possible values of
29415 this option are the same as for @code{-var-set-format}
29416 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29417 the current display format will be used. The current display format
29418 can be changed using the @code{-var-set-format} command.
29424 Note that one must invoke @code{-var-list-children} for a variable
29425 before the value of a child variable can be evaluated.
29427 @subheading The @code{-var-assign} Command
29428 @findex -var-assign
29430 @subsubheading Synopsis
29433 -var-assign @var{name} @var{expression}
29436 Assigns the value of @var{expression} to the variable object specified
29437 by @var{name}. The object must be @samp{editable}. If the variable's
29438 value is altered by the assign, the variable will show up in any
29439 subsequent @code{-var-update} list.
29441 @subsubheading Example
29449 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29453 @subheading The @code{-var-update} Command
29454 @findex -var-update
29456 @subsubheading Synopsis
29459 -var-update [@var{print-values}] @{@var{name} | "*"@}
29462 Reevaluate the expressions corresponding to the variable object
29463 @var{name} and all its direct and indirect children, and return the
29464 list of variable objects whose values have changed; @var{name} must
29465 be a root variable object. Here, ``changed'' means that the result of
29466 @code{-var-evaluate-expression} before and after the
29467 @code{-var-update} is different. If @samp{*} is used as the variable
29468 object names, all existing variable objects are updated, except
29469 for frozen ones (@pxref{-var-set-frozen}). The option
29470 @var{print-values} determines whether both names and values, or just
29471 names are printed. The possible values of this option are the same
29472 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29473 recommended to use the @samp{--all-values} option, to reduce the
29474 number of MI commands needed on each program stop.
29476 With the @samp{*} parameter, if a variable object is bound to a
29477 currently running thread, it will not be updated, without any
29480 If @code{-var-set-update-range} was previously used on a varobj, then
29481 only the selected range of children will be reported.
29483 @code{-var-update} reports all the changed varobjs in a tuple named
29486 Each item in the change list is itself a tuple holding:
29490 The name of the varobj.
29493 If values were requested for this update, then this field will be
29494 present and will hold the value of the varobj.
29497 @anchor{-var-update}
29498 This field is a string which may take one of three values:
29502 The variable object's current value is valid.
29505 The variable object does not currently hold a valid value but it may
29506 hold one in the future if its associated expression comes back into
29510 The variable object no longer holds a valid value.
29511 This can occur when the executable file being debugged has changed,
29512 either through recompilation or by using the @value{GDBN} @code{file}
29513 command. The front end should normally choose to delete these variable
29517 In the future new values may be added to this list so the front should
29518 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29521 This is only present if the varobj is still valid. If the type
29522 changed, then this will be the string @samp{true}; otherwise it will
29525 When a varobj's type changes, its children are also likely to have
29526 become incorrect. Therefore, the varobj's children are automatically
29527 deleted when this attribute is @samp{true}. Also, the varobj's update
29528 range, when set using the @code{-var-set-update-range} command, is
29532 If the varobj's type changed, then this field will be present and will
29535 @item new_num_children
29536 For a dynamic varobj, if the number of children changed, or if the
29537 type changed, this will be the new number of children.
29539 The @samp{numchild} field in other varobj responses is generally not
29540 valid for a dynamic varobj -- it will show the number of children that
29541 @value{GDBN} knows about, but because dynamic varobjs lazily
29542 instantiate their children, this will not reflect the number of
29543 children which may be available.
29545 The @samp{new_num_children} attribute only reports changes to the
29546 number of children known by @value{GDBN}. This is the only way to
29547 detect whether an update has removed children (which necessarily can
29548 only happen at the end of the update range).
29551 The display hint, if any.
29554 This is an integer value, which will be 1 if there are more children
29555 available outside the varobj's update range.
29558 This attribute will be present and have the value @samp{1} if the
29559 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29560 then this attribute will not be present.
29563 If new children were added to a dynamic varobj within the selected
29564 update range (as set by @code{-var-set-update-range}), then they will
29565 be listed in this attribute.
29568 @subsubheading Example
29575 -var-update --all-values var1
29576 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29577 type_changed="false"@}]
29581 @subheading The @code{-var-set-frozen} Command
29582 @findex -var-set-frozen
29583 @anchor{-var-set-frozen}
29585 @subsubheading Synopsis
29588 -var-set-frozen @var{name} @var{flag}
29591 Set the frozenness flag on the variable object @var{name}. The
29592 @var{flag} parameter should be either @samp{1} to make the variable
29593 frozen or @samp{0} to make it unfrozen. If a variable object is
29594 frozen, then neither itself, nor any of its children, are
29595 implicitly updated by @code{-var-update} of
29596 a parent variable or by @code{-var-update *}. Only
29597 @code{-var-update} of the variable itself will update its value and
29598 values of its children. After a variable object is unfrozen, it is
29599 implicitly updated by all subsequent @code{-var-update} operations.
29600 Unfreezing a variable does not update it, only subsequent
29601 @code{-var-update} does.
29603 @subsubheading Example
29607 -var-set-frozen V 1
29612 @subheading The @code{-var-set-update-range} command
29613 @findex -var-set-update-range
29614 @anchor{-var-set-update-range}
29616 @subsubheading Synopsis
29619 -var-set-update-range @var{name} @var{from} @var{to}
29622 Set the range of children to be returned by future invocations of
29623 @code{-var-update}.
29625 @var{from} and @var{to} indicate the range of children to report. If
29626 @var{from} or @var{to} is less than zero, the range is reset and all
29627 children will be reported. Otherwise, children starting at @var{from}
29628 (zero-based) and up to and excluding @var{to} will be reported.
29630 @subsubheading Example
29634 -var-set-update-range V 1 2
29638 @subheading The @code{-var-set-visualizer} command
29639 @findex -var-set-visualizer
29640 @anchor{-var-set-visualizer}
29642 @subsubheading Synopsis
29645 -var-set-visualizer @var{name} @var{visualizer}
29648 Set a visualizer for the variable object @var{name}.
29650 @var{visualizer} is the visualizer to use. The special value
29651 @samp{None} means to disable any visualizer in use.
29653 If not @samp{None}, @var{visualizer} must be a Python expression.
29654 This expression must evaluate to a callable object which accepts a
29655 single argument. @value{GDBN} will call this object with the value of
29656 the varobj @var{name} as an argument (this is done so that the same
29657 Python pretty-printing code can be used for both the CLI and MI).
29658 When called, this object must return an object which conforms to the
29659 pretty-printing interface (@pxref{Pretty Printing API}).
29661 The pre-defined function @code{gdb.default_visualizer} may be used to
29662 select a visualizer by following the built-in process
29663 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29664 a varobj is created, and so ordinarily is not needed.
29666 This feature is only available if Python support is enabled. The MI
29667 command @code{-list-features} (@pxref{GDB/MI Support Commands})
29668 can be used to check this.
29670 @subsubheading Example
29672 Resetting the visualizer:
29676 -var-set-visualizer V None
29680 Reselecting the default (type-based) visualizer:
29684 -var-set-visualizer V gdb.default_visualizer
29688 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29689 can be used to instantiate this class for a varobj:
29693 -var-set-visualizer V "lambda val: SomeClass()"
29697 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29698 @node GDB/MI Data Manipulation
29699 @section @sc{gdb/mi} Data Manipulation
29701 @cindex data manipulation, in @sc{gdb/mi}
29702 @cindex @sc{gdb/mi}, data manipulation
29703 This section describes the @sc{gdb/mi} commands that manipulate data:
29704 examine memory and registers, evaluate expressions, etc.
29706 For details about what an addressable memory unit is,
29707 @pxref{addressable memory unit}.
29709 @c REMOVED FROM THE INTERFACE.
29710 @c @subheading -data-assign
29711 @c Change the value of a program variable. Plenty of side effects.
29712 @c @subsubheading GDB Command
29714 @c @subsubheading Example
29717 @subheading The @code{-data-disassemble} Command
29718 @findex -data-disassemble
29720 @subsubheading Synopsis
29724 [ -s @var{start-addr} -e @var{end-addr} ]
29725 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29733 @item @var{start-addr}
29734 is the beginning address (or @code{$pc})
29735 @item @var{end-addr}
29737 @item @var{filename}
29738 is the name of the file to disassemble
29739 @item @var{linenum}
29740 is the line number to disassemble around
29742 is the number of disassembly lines to be produced. If it is -1,
29743 the whole function will be disassembled, in case no @var{end-addr} is
29744 specified. If @var{end-addr} is specified as a non-zero value, and
29745 @var{lines} is lower than the number of disassembly lines between
29746 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29747 displayed; if @var{lines} is higher than the number of lines between
29748 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29753 @item 0 disassembly only
29754 @item 1 mixed source and disassembly (deprecated)
29755 @item 2 disassembly with raw opcodes
29756 @item 3 mixed source and disassembly with raw opcodes (deprecated)
29757 @item 4 mixed source and disassembly
29758 @item 5 mixed source and disassembly with raw opcodes
29761 Modes 1 and 3 are deprecated. The output is ``source centric''
29762 which hasn't proved useful in practice.
29763 @xref{Machine Code}, for a discussion of the difference between
29764 @code{/m} and @code{/s} output of the @code{disassemble} command.
29767 @subsubheading Result
29769 The result of the @code{-data-disassemble} command will be a list named
29770 @samp{asm_insns}, the contents of this list depend on the @var{mode}
29771 used with the @code{-data-disassemble} command.
29773 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
29778 The address at which this instruction was disassembled.
29781 The name of the function this instruction is within.
29784 The decimal offset in bytes from the start of @samp{func-name}.
29787 The text disassembly for this @samp{address}.
29790 This field is only present for modes 2, 3 and 5. This contains the raw opcode
29791 bytes for the @samp{inst} field.
29795 For modes 1, 3, 4 and 5 the @samp{asm_insns} list contains tuples named
29796 @samp{src_and_asm_line}, each of which has the following fields:
29800 The line number within @samp{file}.
29803 The file name from the compilation unit. This might be an absolute
29804 file name or a relative file name depending on the compile command
29808 Absolute file name of @samp{file}. It is converted to a canonical form
29809 using the source file search path
29810 (@pxref{Source Path, ,Specifying Source Directories})
29811 and after resolving all the symbolic links.
29813 If the source file is not found this field will contain the path as
29814 present in the debug information.
29816 @item line_asm_insn
29817 This is a list of tuples containing the disassembly for @samp{line} in
29818 @samp{file}. The fields of each tuple are the same as for
29819 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
29820 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
29825 Note that whatever included in the @samp{inst} field, is not
29826 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
29829 @subsubheading @value{GDBN} Command
29831 The corresponding @value{GDBN} command is @samp{disassemble}.
29833 @subsubheading Example
29835 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29839 -data-disassemble -s $pc -e "$pc + 20" -- 0
29842 @{address="0x000107c0",func-name="main",offset="4",
29843 inst="mov 2, %o0"@},
29844 @{address="0x000107c4",func-name="main",offset="8",
29845 inst="sethi %hi(0x11800), %o2"@},
29846 @{address="0x000107c8",func-name="main",offset="12",
29847 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29848 @{address="0x000107cc",func-name="main",offset="16",
29849 inst="sethi %hi(0x11800), %o2"@},
29850 @{address="0x000107d0",func-name="main",offset="20",
29851 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29855 Disassemble the whole @code{main} function. Line 32 is part of
29859 -data-disassemble -f basics.c -l 32 -- 0
29861 @{address="0x000107bc",func-name="main",offset="0",
29862 inst="save %sp, -112, %sp"@},
29863 @{address="0x000107c0",func-name="main",offset="4",
29864 inst="mov 2, %o0"@},
29865 @{address="0x000107c4",func-name="main",offset="8",
29866 inst="sethi %hi(0x11800), %o2"@},
29868 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29869 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29873 Disassemble 3 instructions from the start of @code{main}:
29877 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29879 @{address="0x000107bc",func-name="main",offset="0",
29880 inst="save %sp, -112, %sp"@},
29881 @{address="0x000107c0",func-name="main",offset="4",
29882 inst="mov 2, %o0"@},
29883 @{address="0x000107c4",func-name="main",offset="8",
29884 inst="sethi %hi(0x11800), %o2"@}]
29888 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29892 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29894 src_and_asm_line=@{line="31",
29895 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29896 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29897 line_asm_insn=[@{address="0x000107bc",
29898 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
29899 src_and_asm_line=@{line="32",
29900 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
29901 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
29902 line_asm_insn=[@{address="0x000107c0",
29903 func-name="main",offset="4",inst="mov 2, %o0"@},
29904 @{address="0x000107c4",func-name="main",offset="8",
29905 inst="sethi %hi(0x11800), %o2"@}]@}]
29910 @subheading The @code{-data-evaluate-expression} Command
29911 @findex -data-evaluate-expression
29913 @subsubheading Synopsis
29916 -data-evaluate-expression @var{expr}
29919 Evaluate @var{expr} as an expression. The expression could contain an
29920 inferior function call. The function call will execute synchronously.
29921 If the expression contains spaces, it must be enclosed in double quotes.
29923 @subsubheading @value{GDBN} Command
29925 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29926 @samp{call}. In @code{gdbtk} only, there's a corresponding
29927 @samp{gdb_eval} command.
29929 @subsubheading Example
29931 In the following example, the numbers that precede the commands are the
29932 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29933 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29937 211-data-evaluate-expression A
29940 311-data-evaluate-expression &A
29941 311^done,value="0xefffeb7c"
29943 411-data-evaluate-expression A+3
29946 511-data-evaluate-expression "A + 3"
29952 @subheading The @code{-data-list-changed-registers} Command
29953 @findex -data-list-changed-registers
29955 @subsubheading Synopsis
29958 -data-list-changed-registers
29961 Display a list of the registers that have changed.
29963 @subsubheading @value{GDBN} Command
29965 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29966 has the corresponding command @samp{gdb_changed_register_list}.
29968 @subsubheading Example
29970 On a PPC MBX board:
29978 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29979 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29982 -data-list-changed-registers
29983 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29984 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29985 "24","25","26","27","28","30","31","64","65","66","67","69"]
29990 @subheading The @code{-data-list-register-names} Command
29991 @findex -data-list-register-names
29993 @subsubheading Synopsis
29996 -data-list-register-names [ ( @var{regno} )+ ]
29999 Show a list of register names for the current target. If no arguments
30000 are given, it shows a list of the names of all the registers. If
30001 integer numbers are given as arguments, it will print a list of the
30002 names of the registers corresponding to the arguments. To ensure
30003 consistency between a register name and its number, the output list may
30004 include empty register names.
30006 @subsubheading @value{GDBN} Command
30008 @value{GDBN} does not have a command which corresponds to
30009 @samp{-data-list-register-names}. In @code{gdbtk} there is a
30010 corresponding command @samp{gdb_regnames}.
30012 @subsubheading Example
30014 For the PPC MBX board:
30017 -data-list-register-names
30018 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
30019 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
30020 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
30021 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
30022 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
30023 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
30024 "", "pc","ps","cr","lr","ctr","xer"]
30026 -data-list-register-names 1 2 3
30027 ^done,register-names=["r1","r2","r3"]
30031 @subheading The @code{-data-list-register-values} Command
30032 @findex -data-list-register-values
30034 @subsubheading Synopsis
30037 -data-list-register-values
30038 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
30041 Display the registers' contents. The format according to which the
30042 registers' contents are to be returned is given by @var{fmt}, followed
30043 by an optional list of numbers specifying the registers to display. A
30044 missing list of numbers indicates that the contents of all the
30045 registers must be returned. The @code{--skip-unavailable} option
30046 indicates that only the available registers are to be returned.
30048 Allowed formats for @var{fmt} are:
30065 @subsubheading @value{GDBN} Command
30067 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
30068 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
30070 @subsubheading Example
30072 For a PPC MBX board (note: line breaks are for readability only, they
30073 don't appear in the actual output):
30077 -data-list-register-values r 64 65
30078 ^done,register-values=[@{number="64",value="0xfe00a300"@},
30079 @{number="65",value="0x00029002"@}]
30081 -data-list-register-values x
30082 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
30083 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
30084 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
30085 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
30086 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
30087 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
30088 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
30089 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
30090 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
30091 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
30092 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
30093 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
30094 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
30095 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
30096 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
30097 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
30098 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
30099 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
30100 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
30101 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
30102 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
30103 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
30104 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
30105 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
30106 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
30107 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
30108 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
30109 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
30110 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
30111 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
30112 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
30113 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
30114 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
30115 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
30116 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
30117 @{number="69",value="0x20002b03"@}]
30122 @subheading The @code{-data-read-memory} Command
30123 @findex -data-read-memory
30125 This command is deprecated, use @code{-data-read-memory-bytes} instead.
30127 @subsubheading Synopsis
30130 -data-read-memory [ -o @var{byte-offset} ]
30131 @var{address} @var{word-format} @var{word-size}
30132 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
30139 @item @var{address}
30140 An expression specifying the address of the first memory word to be
30141 read. Complex expressions containing embedded white space should be
30142 quoted using the C convention.
30144 @item @var{word-format}
30145 The format to be used to print the memory words. The notation is the
30146 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
30149 @item @var{word-size}
30150 The size of each memory word in bytes.
30152 @item @var{nr-rows}
30153 The number of rows in the output table.
30155 @item @var{nr-cols}
30156 The number of columns in the output table.
30159 If present, indicates that each row should include an @sc{ascii} dump. The
30160 value of @var{aschar} is used as a padding character when a byte is not a
30161 member of the printable @sc{ascii} character set (printable @sc{ascii}
30162 characters are those whose code is between 32 and 126, inclusively).
30164 @item @var{byte-offset}
30165 An offset to add to the @var{address} before fetching memory.
30168 This command displays memory contents as a table of @var{nr-rows} by
30169 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
30170 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
30171 (returned as @samp{total-bytes}). Should less than the requested number
30172 of bytes be returned by the target, the missing words are identified
30173 using @samp{N/A}. The number of bytes read from the target is returned
30174 in @samp{nr-bytes} and the starting address used to read memory in
30177 The address of the next/previous row or page is available in
30178 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
30181 @subsubheading @value{GDBN} Command
30183 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
30184 @samp{gdb_get_mem} memory read command.
30186 @subsubheading Example
30188 Read six bytes of memory starting at @code{bytes+6} but then offset by
30189 @code{-6} bytes. Format as three rows of two columns. One byte per
30190 word. Display each word in hex.
30194 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
30195 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
30196 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
30197 prev-page="0x0000138a",memory=[
30198 @{addr="0x00001390",data=["0x00","0x01"]@},
30199 @{addr="0x00001392",data=["0x02","0x03"]@},
30200 @{addr="0x00001394",data=["0x04","0x05"]@}]
30204 Read two bytes of memory starting at address @code{shorts + 64} and
30205 display as a single word formatted in decimal.
30209 5-data-read-memory shorts+64 d 2 1 1
30210 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
30211 next-row="0x00001512",prev-row="0x0000150e",
30212 next-page="0x00001512",prev-page="0x0000150e",memory=[
30213 @{addr="0x00001510",data=["128"]@}]
30217 Read thirty two bytes of memory starting at @code{bytes+16} and format
30218 as eight rows of four columns. Include a string encoding with @samp{x}
30219 used as the non-printable character.
30223 4-data-read-memory bytes+16 x 1 8 4 x
30224 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
30225 next-row="0x000013c0",prev-row="0x0000139c",
30226 next-page="0x000013c0",prev-page="0x00001380",memory=[
30227 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
30228 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
30229 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
30230 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
30231 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
30232 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
30233 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
30234 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
30238 @subheading The @code{-data-read-memory-bytes} Command
30239 @findex -data-read-memory-bytes
30241 @subsubheading Synopsis
30244 -data-read-memory-bytes [ -o @var{offset} ]
30245 @var{address} @var{count}
30252 @item @var{address}
30253 An expression specifying the address of the first addressable memory unit
30254 to be read. Complex expressions containing embedded white space should be
30255 quoted using the C convention.
30258 The number of addressable memory units to read. This should be an integer
30262 The offset relative to @var{address} at which to start reading. This
30263 should be an integer literal. This option is provided so that a frontend
30264 is not required to first evaluate address and then perform address
30265 arithmetics itself.
30269 This command attempts to read all accessible memory regions in the
30270 specified range. First, all regions marked as unreadable in the memory
30271 map (if one is defined) will be skipped. @xref{Memory Region
30272 Attributes}. Second, @value{GDBN} will attempt to read the remaining
30273 regions. For each one, if reading full region results in an errors,
30274 @value{GDBN} will try to read a subset of the region.
30276 In general, every single memory unit in the region may be readable or not,
30277 and the only way to read every readable unit is to try a read at
30278 every address, which is not practical. Therefore, @value{GDBN} will
30279 attempt to read all accessible memory units at either beginning or the end
30280 of the region, using a binary division scheme. This heuristic works
30281 well for reading accross a memory map boundary. Note that if a region
30282 has a readable range that is neither at the beginning or the end,
30283 @value{GDBN} will not read it.
30285 The result record (@pxref{GDB/MI Result Records}) that is output of
30286 the command includes a field named @samp{memory} whose content is a
30287 list of tuples. Each tuple represent a successfully read memory block
30288 and has the following fields:
30292 The start address of the memory block, as hexadecimal literal.
30295 The end address of the memory block, as hexadecimal literal.
30298 The offset of the memory block, as hexadecimal literal, relative to
30299 the start address passed to @code{-data-read-memory-bytes}.
30302 The contents of the memory block, in hex.
30308 @subsubheading @value{GDBN} Command
30310 The corresponding @value{GDBN} command is @samp{x}.
30312 @subsubheading Example
30316 -data-read-memory-bytes &a 10
30317 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30319 contents="01000000020000000300"@}]
30324 @subheading The @code{-data-write-memory-bytes} Command
30325 @findex -data-write-memory-bytes
30327 @subsubheading Synopsis
30330 -data-write-memory-bytes @var{address} @var{contents}
30331 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
30338 @item @var{address}
30339 An expression specifying the address of the first addressable memory unit
30340 to be written. Complex expressions containing embedded white space should
30341 be quoted using the C convention.
30343 @item @var{contents}
30344 The hex-encoded data to write. It is an error if @var{contents} does
30345 not represent an integral number of addressable memory units.
30348 Optional argument indicating the number of addressable memory units to be
30349 written. If @var{count} is greater than @var{contents}' length,
30350 @value{GDBN} will repeatedly write @var{contents} until it fills
30351 @var{count} memory units.
30355 @subsubheading @value{GDBN} Command
30357 There's no corresponding @value{GDBN} command.
30359 @subsubheading Example
30363 -data-write-memory-bytes &a "aabbccdd"
30370 -data-write-memory-bytes &a "aabbccdd" 16e
30375 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30376 @node GDB/MI Tracepoint Commands
30377 @section @sc{gdb/mi} Tracepoint Commands
30379 The commands defined in this section implement MI support for
30380 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30382 @subheading The @code{-trace-find} Command
30383 @findex -trace-find
30385 @subsubheading Synopsis
30388 -trace-find @var{mode} [@var{parameters}@dots{}]
30391 Find a trace frame using criteria defined by @var{mode} and
30392 @var{parameters}. The following table lists permissible
30393 modes and their parameters. For details of operation, see @ref{tfind}.
30398 No parameters are required. Stops examining trace frames.
30401 An integer is required as parameter. Selects tracepoint frame with
30404 @item tracepoint-number
30405 An integer is required as parameter. Finds next
30406 trace frame that corresponds to tracepoint with the specified number.
30409 An address is required as parameter. Finds
30410 next trace frame that corresponds to any tracepoint at the specified
30413 @item pc-inside-range
30414 Two addresses are required as parameters. Finds next trace
30415 frame that corresponds to a tracepoint at an address inside the
30416 specified range. Both bounds are considered to be inside the range.
30418 @item pc-outside-range
30419 Two addresses are required as parameters. Finds
30420 next trace frame that corresponds to a tracepoint at an address outside
30421 the specified range. Both bounds are considered to be inside the range.
30424 Line specification is required as parameter. @xref{Specify Location}.
30425 Finds next trace frame that corresponds to a tracepoint at
30426 the specified location.
30430 If @samp{none} was passed as @var{mode}, the response does not
30431 have fields. Otherwise, the response may have the following fields:
30435 This field has either @samp{0} or @samp{1} as the value, depending
30436 on whether a matching tracepoint was found.
30439 The index of the found traceframe. This field is present iff
30440 the @samp{found} field has value of @samp{1}.
30443 The index of the found tracepoint. This field is present iff
30444 the @samp{found} field has value of @samp{1}.
30447 The information about the frame corresponding to the found trace
30448 frame. This field is present only if a trace frame was found.
30449 @xref{GDB/MI Frame Information}, for description of this field.
30453 @subsubheading @value{GDBN} Command
30455 The corresponding @value{GDBN} command is @samp{tfind}.
30457 @subheading -trace-define-variable
30458 @findex -trace-define-variable
30460 @subsubheading Synopsis
30463 -trace-define-variable @var{name} [ @var{value} ]
30466 Create trace variable @var{name} if it does not exist. If
30467 @var{value} is specified, sets the initial value of the specified
30468 trace variable to that value. Note that the @var{name} should start
30469 with the @samp{$} character.
30471 @subsubheading @value{GDBN} Command
30473 The corresponding @value{GDBN} command is @samp{tvariable}.
30475 @subheading The @code{-trace-frame-collected} Command
30476 @findex -trace-frame-collected
30478 @subsubheading Synopsis
30481 -trace-frame-collected
30482 [--var-print-values @var{var_pval}]
30483 [--comp-print-values @var{comp_pval}]
30484 [--registers-format @var{regformat}]
30485 [--memory-contents]
30488 This command returns the set of collected objects, register names,
30489 trace state variable names, memory ranges and computed expressions
30490 that have been collected at a particular trace frame. The optional
30491 parameters to the command affect the output format in different ways.
30492 See the output description table below for more details.
30494 The reported names can be used in the normal manner to create
30495 varobjs and inspect the objects themselves. The items returned by
30496 this command are categorized so that it is clear which is a variable,
30497 which is a register, which is a trace state variable, which is a
30498 memory range and which is a computed expression.
30500 For instance, if the actions were
30502 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
30503 collect *(int*)0xaf02bef0@@40
30507 the object collected in its entirety would be @code{myVar}. The
30508 object @code{myArray} would be partially collected, because only the
30509 element at index @code{myIndex} would be collected. The remaining
30510 objects would be computed expressions.
30512 An example output would be:
30516 -trace-frame-collected
30518 explicit-variables=[@{name="myVar",value="1"@}],
30519 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
30520 @{name="myObj.field",value="0"@},
30521 @{name="myPtr->field",value="1"@},
30522 @{name="myCount + 2",value="3"@},
30523 @{name="$tvar1 + 1",value="43970027"@}],
30524 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
30525 @{number="1",value="0x0"@},
30526 @{number="2",value="0x4"@},
30528 @{number="125",value="0x0"@}],
30529 tvars=[@{name="$tvar1",current="43970026"@}],
30530 memory=[@{address="0x0000000000602264",length="4"@},
30531 @{address="0x0000000000615bc0",length="4"@}]
30538 @item explicit-variables
30539 The set of objects that have been collected in their entirety (as
30540 opposed to collecting just a few elements of an array or a few struct
30541 members). For each object, its name and value are printed.
30542 The @code{--var-print-values} option affects how or whether the value
30543 field is output. If @var{var_pval} is 0, then print only the names;
30544 if it is 1, print also their values; and if it is 2, print the name,
30545 type and value for simple data types, and the name and type for
30546 arrays, structures and unions.
30548 @item computed-expressions
30549 The set of computed expressions that have been collected at the
30550 current trace frame. The @code{--comp-print-values} option affects
30551 this set like the @code{--var-print-values} option affects the
30552 @code{explicit-variables} set. See above.
30555 The registers that have been collected at the current trace frame.
30556 For each register collected, the name and current value are returned.
30557 The value is formatted according to the @code{--registers-format}
30558 option. See the @command{-data-list-register-values} command for a
30559 list of the allowed formats. The default is @samp{x}.
30562 The trace state variables that have been collected at the current
30563 trace frame. For each trace state variable collected, the name and
30564 current value are returned.
30567 The set of memory ranges that have been collected at the current trace
30568 frame. Its content is a list of tuples. Each tuple represents a
30569 collected memory range and has the following fields:
30573 The start address of the memory range, as hexadecimal literal.
30576 The length of the memory range, as decimal literal.
30579 The contents of the memory block, in hex. This field is only present
30580 if the @code{--memory-contents} option is specified.
30586 @subsubheading @value{GDBN} Command
30588 There is no corresponding @value{GDBN} command.
30590 @subsubheading Example
30592 @subheading -trace-list-variables
30593 @findex -trace-list-variables
30595 @subsubheading Synopsis
30598 -trace-list-variables
30601 Return a table of all defined trace variables. Each element of the
30602 table has the following fields:
30606 The name of the trace variable. This field is always present.
30609 The initial value. This is a 64-bit signed integer. This
30610 field is always present.
30613 The value the trace variable has at the moment. This is a 64-bit
30614 signed integer. This field is absent iff current value is
30615 not defined, for example if the trace was never run, or is
30620 @subsubheading @value{GDBN} Command
30622 The corresponding @value{GDBN} command is @samp{tvariables}.
30624 @subsubheading Example
30628 -trace-list-variables
30629 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30630 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30631 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30632 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30633 body=[variable=@{name="$trace_timestamp",initial="0"@}
30634 variable=@{name="$foo",initial="10",current="15"@}]@}
30638 @subheading -trace-save
30639 @findex -trace-save
30641 @subsubheading Synopsis
30644 -trace-save [-r ] @var{filename}
30647 Saves the collected trace data to @var{filename}. Without the
30648 @samp{-r} option, the data is downloaded from the target and saved
30649 in a local file. With the @samp{-r} option the target is asked
30650 to perform the save.
30652 @subsubheading @value{GDBN} Command
30654 The corresponding @value{GDBN} command is @samp{tsave}.
30657 @subheading -trace-start
30658 @findex -trace-start
30660 @subsubheading Synopsis
30666 Starts a tracing experiments. The result of this command does not
30669 @subsubheading @value{GDBN} Command
30671 The corresponding @value{GDBN} command is @samp{tstart}.
30673 @subheading -trace-status
30674 @findex -trace-status
30676 @subsubheading Synopsis
30682 Obtains the status of a tracing experiment. The result may include
30683 the following fields:
30688 May have a value of either @samp{0}, when no tracing operations are
30689 supported, @samp{1}, when all tracing operations are supported, or
30690 @samp{file} when examining trace file. In the latter case, examining
30691 of trace frame is possible but new tracing experiement cannot be
30692 started. This field is always present.
30695 May have a value of either @samp{0} or @samp{1} depending on whether
30696 tracing experiement is in progress on target. This field is present
30697 if @samp{supported} field is not @samp{0}.
30700 Report the reason why the tracing was stopped last time. This field
30701 may be absent iff tracing was never stopped on target yet. The
30702 value of @samp{request} means the tracing was stopped as result of
30703 the @code{-trace-stop} command. The value of @samp{overflow} means
30704 the tracing buffer is full. The value of @samp{disconnection} means
30705 tracing was automatically stopped when @value{GDBN} has disconnected.
30706 The value of @samp{passcount} means tracing was stopped when a
30707 tracepoint was passed a maximal number of times for that tracepoint.
30708 This field is present if @samp{supported} field is not @samp{0}.
30710 @item stopping-tracepoint
30711 The number of tracepoint whose passcount as exceeded. This field is
30712 present iff the @samp{stop-reason} field has the value of
30716 @itemx frames-created
30717 The @samp{frames} field is a count of the total number of trace frames
30718 in the trace buffer, while @samp{frames-created} is the total created
30719 during the run, including ones that were discarded, such as when a
30720 circular trace buffer filled up. Both fields are optional.
30724 These fields tell the current size of the tracing buffer and the
30725 remaining space. These fields are optional.
30728 The value of the circular trace buffer flag. @code{1} means that the
30729 trace buffer is circular and old trace frames will be discarded if
30730 necessary to make room, @code{0} means that the trace buffer is linear
30734 The value of the disconnected tracing flag. @code{1} means that
30735 tracing will continue after @value{GDBN} disconnects, @code{0} means
30736 that the trace run will stop.
30739 The filename of the trace file being examined. This field is
30740 optional, and only present when examining a trace file.
30744 @subsubheading @value{GDBN} Command
30746 The corresponding @value{GDBN} command is @samp{tstatus}.
30748 @subheading -trace-stop
30749 @findex -trace-stop
30751 @subsubheading Synopsis
30757 Stops a tracing experiment. The result of this command has the same
30758 fields as @code{-trace-status}, except that the @samp{supported} and
30759 @samp{running} fields are not output.
30761 @subsubheading @value{GDBN} Command
30763 The corresponding @value{GDBN} command is @samp{tstop}.
30766 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30767 @node GDB/MI Symbol Query
30768 @section @sc{gdb/mi} Symbol Query Commands
30772 @subheading The @code{-symbol-info-address} Command
30773 @findex -symbol-info-address
30775 @subsubheading Synopsis
30778 -symbol-info-address @var{symbol}
30781 Describe where @var{symbol} is stored.
30783 @subsubheading @value{GDBN} Command
30785 The corresponding @value{GDBN} command is @samp{info address}.
30787 @subsubheading Example
30791 @subheading The @code{-symbol-info-file} Command
30792 @findex -symbol-info-file
30794 @subsubheading Synopsis
30800 Show the file for the symbol.
30802 @subsubheading @value{GDBN} Command
30804 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30805 @samp{gdb_find_file}.
30807 @subsubheading Example
30811 @subheading The @code{-symbol-info-function} Command
30812 @findex -symbol-info-function
30814 @subsubheading Synopsis
30817 -symbol-info-function
30820 Show which function the symbol lives in.
30822 @subsubheading @value{GDBN} Command
30824 @samp{gdb_get_function} in @code{gdbtk}.
30826 @subsubheading Example
30830 @subheading The @code{-symbol-info-line} Command
30831 @findex -symbol-info-line
30833 @subsubheading Synopsis
30839 Show the core addresses of the code for a source line.
30841 @subsubheading @value{GDBN} Command
30843 The corresponding @value{GDBN} command is @samp{info line}.
30844 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30846 @subsubheading Example
30850 @subheading The @code{-symbol-info-symbol} Command
30851 @findex -symbol-info-symbol
30853 @subsubheading Synopsis
30856 -symbol-info-symbol @var{addr}
30859 Describe what symbol is at location @var{addr}.
30861 @subsubheading @value{GDBN} Command
30863 The corresponding @value{GDBN} command is @samp{info symbol}.
30865 @subsubheading Example
30869 @subheading The @code{-symbol-list-functions} Command
30870 @findex -symbol-list-functions
30872 @subsubheading Synopsis
30875 -symbol-list-functions
30878 List the functions in the executable.
30880 @subsubheading @value{GDBN} Command
30882 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30883 @samp{gdb_search} in @code{gdbtk}.
30885 @subsubheading Example
30890 @subheading The @code{-symbol-list-lines} Command
30891 @findex -symbol-list-lines
30893 @subsubheading Synopsis
30896 -symbol-list-lines @var{filename}
30899 Print the list of lines that contain code and their associated program
30900 addresses for the given source filename. The entries are sorted in
30901 ascending PC order.
30903 @subsubheading @value{GDBN} Command
30905 There is no corresponding @value{GDBN} command.
30907 @subsubheading Example
30910 -symbol-list-lines basics.c
30911 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30917 @subheading The @code{-symbol-list-types} Command
30918 @findex -symbol-list-types
30920 @subsubheading Synopsis
30926 List all the type names.
30928 @subsubheading @value{GDBN} Command
30930 The corresponding commands are @samp{info types} in @value{GDBN},
30931 @samp{gdb_search} in @code{gdbtk}.
30933 @subsubheading Example
30937 @subheading The @code{-symbol-list-variables} Command
30938 @findex -symbol-list-variables
30940 @subsubheading Synopsis
30943 -symbol-list-variables
30946 List all the global and static variable names.
30948 @subsubheading @value{GDBN} Command
30950 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30952 @subsubheading Example
30956 @subheading The @code{-symbol-locate} Command
30957 @findex -symbol-locate
30959 @subsubheading Synopsis
30965 @subsubheading @value{GDBN} Command
30967 @samp{gdb_loc} in @code{gdbtk}.
30969 @subsubheading Example
30973 @subheading The @code{-symbol-type} Command
30974 @findex -symbol-type
30976 @subsubheading Synopsis
30979 -symbol-type @var{variable}
30982 Show type of @var{variable}.
30984 @subsubheading @value{GDBN} Command
30986 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30987 @samp{gdb_obj_variable}.
30989 @subsubheading Example
30994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30995 @node GDB/MI File Commands
30996 @section @sc{gdb/mi} File Commands
30998 This section describes the GDB/MI commands to specify executable file names
30999 and to read in and obtain symbol table information.
31001 @subheading The @code{-file-exec-and-symbols} Command
31002 @findex -file-exec-and-symbols
31004 @subsubheading Synopsis
31007 -file-exec-and-symbols @var{file}
31010 Specify the executable file to be debugged. This file is the one from
31011 which the symbol table is also read. If no file is specified, the
31012 command clears the executable and symbol information. If breakpoints
31013 are set when using this command with no arguments, @value{GDBN} will produce
31014 error messages. Otherwise, no output is produced, except a completion
31017 @subsubheading @value{GDBN} Command
31019 The corresponding @value{GDBN} command is @samp{file}.
31021 @subsubheading Example
31025 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31031 @subheading The @code{-file-exec-file} Command
31032 @findex -file-exec-file
31034 @subsubheading Synopsis
31037 -file-exec-file @var{file}
31040 Specify the executable file to be debugged. Unlike
31041 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
31042 from this file. If used without argument, @value{GDBN} clears the information
31043 about the executable file. No output is produced, except a completion
31046 @subsubheading @value{GDBN} Command
31048 The corresponding @value{GDBN} command is @samp{exec-file}.
31050 @subsubheading Example
31054 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31061 @subheading The @code{-file-list-exec-sections} Command
31062 @findex -file-list-exec-sections
31064 @subsubheading Synopsis
31067 -file-list-exec-sections
31070 List the sections of the current executable file.
31072 @subsubheading @value{GDBN} Command
31074 The @value{GDBN} command @samp{info file} shows, among the rest, the same
31075 information as this command. @code{gdbtk} has a corresponding command
31076 @samp{gdb_load_info}.
31078 @subsubheading Example
31083 @subheading The @code{-file-list-exec-source-file} Command
31084 @findex -file-list-exec-source-file
31086 @subsubheading Synopsis
31089 -file-list-exec-source-file
31092 List the line number, the current source file, and the absolute path
31093 to the current source file for the current executable. The macro
31094 information field has a value of @samp{1} or @samp{0} depending on
31095 whether or not the file includes preprocessor macro information.
31097 @subsubheading @value{GDBN} Command
31099 The @value{GDBN} equivalent is @samp{info source}
31101 @subsubheading Example
31105 123-file-list-exec-source-file
31106 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
31111 @subheading The @code{-file-list-exec-source-files} Command
31112 @findex -file-list-exec-source-files
31114 @subsubheading Synopsis
31117 -file-list-exec-source-files
31120 List the source files for the current executable.
31122 It will always output both the filename and fullname (absolute file
31123 name) of a source file.
31125 @subsubheading @value{GDBN} Command
31127 The @value{GDBN} equivalent is @samp{info sources}.
31128 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
31130 @subsubheading Example
31133 -file-list-exec-source-files
31135 @{file=foo.c,fullname=/home/foo.c@},
31136 @{file=/home/bar.c,fullname=/home/bar.c@},
31137 @{file=gdb_could_not_find_fullpath.c@}]
31142 @subheading The @code{-file-list-shared-libraries} Command
31143 @findex -file-list-shared-libraries
31145 @subsubheading Synopsis
31148 -file-list-shared-libraries
31151 List the shared libraries in the program.
31153 @subsubheading @value{GDBN} Command
31155 The corresponding @value{GDBN} command is @samp{info shared}.
31157 @subsubheading Example
31161 @subheading The @code{-file-list-symbol-files} Command
31162 @findex -file-list-symbol-files
31164 @subsubheading Synopsis
31167 -file-list-symbol-files
31172 @subsubheading @value{GDBN} Command
31174 The corresponding @value{GDBN} command is @samp{info file} (part of it).
31176 @subsubheading Example
31181 @subheading The @code{-file-symbol-file} Command
31182 @findex -file-symbol-file
31184 @subsubheading Synopsis
31187 -file-symbol-file @var{file}
31190 Read symbol table info from the specified @var{file} argument. When
31191 used without arguments, clears @value{GDBN}'s symbol table info. No output is
31192 produced, except for a completion notification.
31194 @subsubheading @value{GDBN} Command
31196 The corresponding @value{GDBN} command is @samp{symbol-file}.
31198 @subsubheading Example
31202 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
31208 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31209 @node GDB/MI Memory Overlay Commands
31210 @section @sc{gdb/mi} Memory Overlay Commands
31212 The memory overlay commands are not implemented.
31214 @c @subheading -overlay-auto
31216 @c @subheading -overlay-list-mapping-state
31218 @c @subheading -overlay-list-overlays
31220 @c @subheading -overlay-map
31222 @c @subheading -overlay-off
31224 @c @subheading -overlay-on
31226 @c @subheading -overlay-unmap
31228 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31229 @node GDB/MI Signal Handling Commands
31230 @section @sc{gdb/mi} Signal Handling Commands
31232 Signal handling commands are not implemented.
31234 @c @subheading -signal-handle
31236 @c @subheading -signal-list-handle-actions
31238 @c @subheading -signal-list-signal-types
31242 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31243 @node GDB/MI Target Manipulation
31244 @section @sc{gdb/mi} Target Manipulation Commands
31247 @subheading The @code{-target-attach} Command
31248 @findex -target-attach
31250 @subsubheading Synopsis
31253 -target-attach @var{pid} | @var{gid} | @var{file}
31256 Attach to a process @var{pid} or a file @var{file} outside of
31257 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
31258 group, the id previously returned by
31259 @samp{-list-thread-groups --available} must be used.
31261 @subsubheading @value{GDBN} Command
31263 The corresponding @value{GDBN} command is @samp{attach}.
31265 @subsubheading Example
31269 =thread-created,id="1"
31270 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
31276 @subheading The @code{-target-compare-sections} Command
31277 @findex -target-compare-sections
31279 @subsubheading Synopsis
31282 -target-compare-sections [ @var{section} ]
31285 Compare data of section @var{section} on target to the exec file.
31286 Without the argument, all sections are compared.
31288 @subsubheading @value{GDBN} Command
31290 The @value{GDBN} equivalent is @samp{compare-sections}.
31292 @subsubheading Example
31297 @subheading The @code{-target-detach} Command
31298 @findex -target-detach
31300 @subsubheading Synopsis
31303 -target-detach [ @var{pid} | @var{gid} ]
31306 Detach from the remote target which normally resumes its execution.
31307 If either @var{pid} or @var{gid} is specified, detaches from either
31308 the specified process, or specified thread group. There's no output.
31310 @subsubheading @value{GDBN} Command
31312 The corresponding @value{GDBN} command is @samp{detach}.
31314 @subsubheading Example
31324 @subheading The @code{-target-disconnect} Command
31325 @findex -target-disconnect
31327 @subsubheading Synopsis
31333 Disconnect from the remote target. There's no output and the target is
31334 generally not resumed.
31336 @subsubheading @value{GDBN} Command
31338 The corresponding @value{GDBN} command is @samp{disconnect}.
31340 @subsubheading Example
31350 @subheading The @code{-target-download} Command
31351 @findex -target-download
31353 @subsubheading Synopsis
31359 Loads the executable onto the remote target.
31360 It prints out an update message every half second, which includes the fields:
31364 The name of the section.
31366 The size of what has been sent so far for that section.
31368 The size of the section.
31370 The total size of what was sent so far (the current and the previous sections).
31372 The size of the overall executable to download.
31376 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
31377 @sc{gdb/mi} Output Syntax}).
31379 In addition, it prints the name and size of the sections, as they are
31380 downloaded. These messages include the following fields:
31384 The name of the section.
31386 The size of the section.
31388 The size of the overall executable to download.
31392 At the end, a summary is printed.
31394 @subsubheading @value{GDBN} Command
31396 The corresponding @value{GDBN} command is @samp{load}.
31398 @subsubheading Example
31400 Note: each status message appears on a single line. Here the messages
31401 have been broken down so that they can fit onto a page.
31406 +download,@{section=".text",section-size="6668",total-size="9880"@}
31407 +download,@{section=".text",section-sent="512",section-size="6668",
31408 total-sent="512",total-size="9880"@}
31409 +download,@{section=".text",section-sent="1024",section-size="6668",
31410 total-sent="1024",total-size="9880"@}
31411 +download,@{section=".text",section-sent="1536",section-size="6668",
31412 total-sent="1536",total-size="9880"@}
31413 +download,@{section=".text",section-sent="2048",section-size="6668",
31414 total-sent="2048",total-size="9880"@}
31415 +download,@{section=".text",section-sent="2560",section-size="6668",
31416 total-sent="2560",total-size="9880"@}
31417 +download,@{section=".text",section-sent="3072",section-size="6668",
31418 total-sent="3072",total-size="9880"@}
31419 +download,@{section=".text",section-sent="3584",section-size="6668",
31420 total-sent="3584",total-size="9880"@}
31421 +download,@{section=".text",section-sent="4096",section-size="6668",
31422 total-sent="4096",total-size="9880"@}
31423 +download,@{section=".text",section-sent="4608",section-size="6668",
31424 total-sent="4608",total-size="9880"@}
31425 +download,@{section=".text",section-sent="5120",section-size="6668",
31426 total-sent="5120",total-size="9880"@}
31427 +download,@{section=".text",section-sent="5632",section-size="6668",
31428 total-sent="5632",total-size="9880"@}
31429 +download,@{section=".text",section-sent="6144",section-size="6668",
31430 total-sent="6144",total-size="9880"@}
31431 +download,@{section=".text",section-sent="6656",section-size="6668",
31432 total-sent="6656",total-size="9880"@}
31433 +download,@{section=".init",section-size="28",total-size="9880"@}
31434 +download,@{section=".fini",section-size="28",total-size="9880"@}
31435 +download,@{section=".data",section-size="3156",total-size="9880"@}
31436 +download,@{section=".data",section-sent="512",section-size="3156",
31437 total-sent="7236",total-size="9880"@}
31438 +download,@{section=".data",section-sent="1024",section-size="3156",
31439 total-sent="7748",total-size="9880"@}
31440 +download,@{section=".data",section-sent="1536",section-size="3156",
31441 total-sent="8260",total-size="9880"@}
31442 +download,@{section=".data",section-sent="2048",section-size="3156",
31443 total-sent="8772",total-size="9880"@}
31444 +download,@{section=".data",section-sent="2560",section-size="3156",
31445 total-sent="9284",total-size="9880"@}
31446 +download,@{section=".data",section-sent="3072",section-size="3156",
31447 total-sent="9796",total-size="9880"@}
31448 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31455 @subheading The @code{-target-exec-status} Command
31456 @findex -target-exec-status
31458 @subsubheading Synopsis
31461 -target-exec-status
31464 Provide information on the state of the target (whether it is running or
31465 not, for instance).
31467 @subsubheading @value{GDBN} Command
31469 There's no equivalent @value{GDBN} command.
31471 @subsubheading Example
31475 @subheading The @code{-target-list-available-targets} Command
31476 @findex -target-list-available-targets
31478 @subsubheading Synopsis
31481 -target-list-available-targets
31484 List the possible targets to connect to.
31486 @subsubheading @value{GDBN} Command
31488 The corresponding @value{GDBN} command is @samp{help target}.
31490 @subsubheading Example
31494 @subheading The @code{-target-list-current-targets} Command
31495 @findex -target-list-current-targets
31497 @subsubheading Synopsis
31500 -target-list-current-targets
31503 Describe the current target.
31505 @subsubheading @value{GDBN} Command
31507 The corresponding information is printed by @samp{info file} (among
31510 @subsubheading Example
31514 @subheading The @code{-target-list-parameters} Command
31515 @findex -target-list-parameters
31517 @subsubheading Synopsis
31520 -target-list-parameters
31526 @subsubheading @value{GDBN} Command
31530 @subsubheading Example
31534 @subheading The @code{-target-select} Command
31535 @findex -target-select
31537 @subsubheading Synopsis
31540 -target-select @var{type} @var{parameters @dots{}}
31543 Connect @value{GDBN} to the remote target. This command takes two args:
31547 The type of target, for instance @samp{remote}, etc.
31548 @item @var{parameters}
31549 Device names, host names and the like. @xref{Target Commands, ,
31550 Commands for Managing Targets}, for more details.
31553 The output is a connection notification, followed by the address at
31554 which the target program is, in the following form:
31557 ^connected,addr="@var{address}",func="@var{function name}",
31558 args=[@var{arg list}]
31561 @subsubheading @value{GDBN} Command
31563 The corresponding @value{GDBN} command is @samp{target}.
31565 @subsubheading Example
31569 -target-select remote /dev/ttya
31570 ^connected,addr="0xfe00a300",func="??",args=[]
31574 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31575 @node GDB/MI File Transfer Commands
31576 @section @sc{gdb/mi} File Transfer Commands
31579 @subheading The @code{-target-file-put} Command
31580 @findex -target-file-put
31582 @subsubheading Synopsis
31585 -target-file-put @var{hostfile} @var{targetfile}
31588 Copy file @var{hostfile} from the host system (the machine running
31589 @value{GDBN}) to @var{targetfile} on the target system.
31591 @subsubheading @value{GDBN} Command
31593 The corresponding @value{GDBN} command is @samp{remote put}.
31595 @subsubheading Example
31599 -target-file-put localfile remotefile
31605 @subheading The @code{-target-file-get} Command
31606 @findex -target-file-get
31608 @subsubheading Synopsis
31611 -target-file-get @var{targetfile} @var{hostfile}
31614 Copy file @var{targetfile} from the target system to @var{hostfile}
31615 on the host system.
31617 @subsubheading @value{GDBN} Command
31619 The corresponding @value{GDBN} command is @samp{remote get}.
31621 @subsubheading Example
31625 -target-file-get remotefile localfile
31631 @subheading The @code{-target-file-delete} Command
31632 @findex -target-file-delete
31634 @subsubheading Synopsis
31637 -target-file-delete @var{targetfile}
31640 Delete @var{targetfile} from the target system.
31642 @subsubheading @value{GDBN} Command
31644 The corresponding @value{GDBN} command is @samp{remote delete}.
31646 @subsubheading Example
31650 -target-file-delete remotefile
31656 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31657 @node GDB/MI Ada Exceptions Commands
31658 @section Ada Exceptions @sc{gdb/mi} Commands
31660 @subheading The @code{-info-ada-exceptions} Command
31661 @findex -info-ada-exceptions
31663 @subsubheading Synopsis
31666 -info-ada-exceptions [ @var{regexp}]
31669 List all Ada exceptions defined within the program being debugged.
31670 With a regular expression @var{regexp}, only those exceptions whose
31671 names match @var{regexp} are listed.
31673 @subsubheading @value{GDBN} Command
31675 The corresponding @value{GDBN} command is @samp{info exceptions}.
31677 @subsubheading Result
31679 The result is a table of Ada exceptions. The following columns are
31680 defined for each exception:
31684 The name of the exception.
31687 The address of the exception.
31691 @subsubheading Example
31694 -info-ada-exceptions aint
31695 ^done,ada-exceptions=@{nr_rows="2",nr_cols="2",
31696 hdr=[@{width="1",alignment="-1",col_name="name",colhdr="Name"@},
31697 @{width="1",alignment="-1",col_name="address",colhdr="Address"@}],
31698 body=[@{name="constraint_error",address="0x0000000000613da0"@},
31699 @{name="const.aint_global_e",address="0x0000000000613b00"@}]@}
31702 @subheading Catching Ada Exceptions
31704 The commands describing how to ask @value{GDBN} to stop when a program
31705 raises an exception are described at @ref{Ada Exception GDB/MI
31706 Catchpoint Commands}.
31709 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31710 @node GDB/MI Support Commands
31711 @section @sc{gdb/mi} Support Commands
31713 Since new commands and features get regularly added to @sc{gdb/mi},
31714 some commands are available to help front-ends query the debugger
31715 about support for these capabilities. Similarly, it is also possible
31716 to query @value{GDBN} about target support of certain features.
31718 @subheading The @code{-info-gdb-mi-command} Command
31719 @cindex @code{-info-gdb-mi-command}
31720 @findex -info-gdb-mi-command
31722 @subsubheading Synopsis
31725 -info-gdb-mi-command @var{cmd_name}
31728 Query support for the @sc{gdb/mi} command named @var{cmd_name}.
31730 Note that the dash (@code{-}) starting all @sc{gdb/mi} commands
31731 is technically not part of the command name (@pxref{GDB/MI Input
31732 Syntax}), and thus should be omitted in @var{cmd_name}. However,
31733 for ease of use, this command also accepts the form with the leading
31736 @subsubheading @value{GDBN} Command
31738 There is no corresponding @value{GDBN} command.
31740 @subsubheading Result
31742 The result is a tuple. There is currently only one field:
31746 This field is equal to @code{"true"} if the @sc{gdb/mi} command exists,
31747 @code{"false"} otherwise.
31751 @subsubheading Example
31753 Here is an example where the @sc{gdb/mi} command does not exist:
31756 -info-gdb-mi-command unsupported-command
31757 ^done,command=@{exists="false"@}
31761 And here is an example where the @sc{gdb/mi} command is known
31765 -info-gdb-mi-command symbol-list-lines
31766 ^done,command=@{exists="true"@}
31769 @subheading The @code{-list-features} Command
31770 @findex -list-features
31771 @cindex supported @sc{gdb/mi} features, list
31773 Returns a list of particular features of the MI protocol that
31774 this version of gdb implements. A feature can be a command,
31775 or a new field in an output of some command, or even an
31776 important bugfix. While a frontend can sometimes detect presence
31777 of a feature at runtime, it is easier to perform detection at debugger
31780 The command returns a list of strings, with each string naming an
31781 available feature. Each returned string is just a name, it does not
31782 have any internal structure. The list of possible feature names
31788 (gdb) -list-features
31789 ^done,result=["feature1","feature2"]
31792 The current list of features is:
31795 @item frozen-varobjs
31796 Indicates support for the @code{-var-set-frozen} command, as well
31797 as possible presense of the @code{frozen} field in the output
31798 of @code{-varobj-create}.
31799 @item pending-breakpoints
31800 Indicates support for the @option{-f} option to the @code{-break-insert}
31803 Indicates Python scripting support, Python-based
31804 pretty-printing commands, and possible presence of the
31805 @samp{display_hint} field in the output of @code{-var-list-children}
31807 Indicates support for the @code{-thread-info} command.
31808 @item data-read-memory-bytes
31809 Indicates support for the @code{-data-read-memory-bytes} and the
31810 @code{-data-write-memory-bytes} commands.
31811 @item breakpoint-notifications
31812 Indicates that changes to breakpoints and breakpoints created via the
31813 CLI will be announced via async records.
31814 @item ada-task-info
31815 Indicates support for the @code{-ada-task-info} command.
31816 @item language-option
31817 Indicates that all @sc{gdb/mi} commands accept the @option{--language}
31818 option (@pxref{Context management}).
31819 @item info-gdb-mi-command
31820 Indicates support for the @code{-info-gdb-mi-command} command.
31821 @item undefined-command-error-code
31822 Indicates support for the "undefined-command" error code in error result
31823 records, produced when trying to execute an undefined @sc{gdb/mi} command
31824 (@pxref{GDB/MI Result Records}).
31825 @item exec-run-start-option
31826 Indicates that the @code{-exec-run} command supports the @option{--start}
31827 option (@pxref{GDB/MI Program Execution}).
31830 @subheading The @code{-list-target-features} Command
31831 @findex -list-target-features
31833 Returns a list of particular features that are supported by the
31834 target. Those features affect the permitted MI commands, but
31835 unlike the features reported by the @code{-list-features} command, the
31836 features depend on which target GDB is using at the moment. Whenever
31837 a target can change, due to commands such as @code{-target-select},
31838 @code{-target-attach} or @code{-exec-run}, the list of target features
31839 may change, and the frontend should obtain it again.
31843 (gdb) -list-target-features
31844 ^done,result=["async"]
31847 The current list of features is:
31851 Indicates that the target is capable of asynchronous command
31852 execution, which means that @value{GDBN} will accept further commands
31853 while the target is running.
31856 Indicates that the target is capable of reverse execution.
31857 @xref{Reverse Execution}, for more information.
31861 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31862 @node GDB/MI Miscellaneous Commands
31863 @section Miscellaneous @sc{gdb/mi} Commands
31865 @c @subheading -gdb-complete
31867 @subheading The @code{-gdb-exit} Command
31870 @subsubheading Synopsis
31876 Exit @value{GDBN} immediately.
31878 @subsubheading @value{GDBN} Command
31880 Approximately corresponds to @samp{quit}.
31882 @subsubheading Example
31892 @subheading The @code{-exec-abort} Command
31893 @findex -exec-abort
31895 @subsubheading Synopsis
31901 Kill the inferior running program.
31903 @subsubheading @value{GDBN} Command
31905 The corresponding @value{GDBN} command is @samp{kill}.
31907 @subsubheading Example
31912 @subheading The @code{-gdb-set} Command
31915 @subsubheading Synopsis
31921 Set an internal @value{GDBN} variable.
31922 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31924 @subsubheading @value{GDBN} Command
31926 The corresponding @value{GDBN} command is @samp{set}.
31928 @subsubheading Example
31938 @subheading The @code{-gdb-show} Command
31941 @subsubheading Synopsis
31947 Show the current value of a @value{GDBN} variable.
31949 @subsubheading @value{GDBN} Command
31951 The corresponding @value{GDBN} command is @samp{show}.
31953 @subsubheading Example
31962 @c @subheading -gdb-source
31965 @subheading The @code{-gdb-version} Command
31966 @findex -gdb-version
31968 @subsubheading Synopsis
31974 Show version information for @value{GDBN}. Used mostly in testing.
31976 @subsubheading @value{GDBN} Command
31978 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31979 default shows this information when you start an interactive session.
31981 @subsubheading Example
31983 @c This example modifies the actual output from GDB to avoid overfull
31989 ~Copyright 2000 Free Software Foundation, Inc.
31990 ~GDB is free software, covered by the GNU General Public License, and
31991 ~you are welcome to change it and/or distribute copies of it under
31992 ~ certain conditions.
31993 ~Type "show copying" to see the conditions.
31994 ~There is absolutely no warranty for GDB. Type "show warranty" for
31996 ~This GDB was configured as
31997 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
32002 @subheading The @code{-list-thread-groups} Command
32003 @findex -list-thread-groups
32005 @subheading Synopsis
32008 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
32011 Lists thread groups (@pxref{Thread groups}). When a single thread
32012 group is passed as the argument, lists the children of that group.
32013 When several thread group are passed, lists information about those
32014 thread groups. Without any parameters, lists information about all
32015 top-level thread groups.
32017 Normally, thread groups that are being debugged are reported.
32018 With the @samp{--available} option, @value{GDBN} reports thread groups
32019 available on the target.
32021 The output of this command may have either a @samp{threads} result or
32022 a @samp{groups} result. The @samp{thread} result has a list of tuples
32023 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
32024 Information}). The @samp{groups} result has a list of tuples as value,
32025 each tuple describing a thread group. If top-level groups are
32026 requested (that is, no parameter is passed), or when several groups
32027 are passed, the output always has a @samp{groups} result. The format
32028 of the @samp{group} result is described below.
32030 To reduce the number of roundtrips it's possible to list thread groups
32031 together with their children, by passing the @samp{--recurse} option
32032 and the recursion depth. Presently, only recursion depth of 1 is
32033 permitted. If this option is present, then every reported thread group
32034 will also include its children, either as @samp{group} or
32035 @samp{threads} field.
32037 In general, any combination of option and parameters is permitted, with
32038 the following caveats:
32042 When a single thread group is passed, the output will typically
32043 be the @samp{threads} result. Because threads may not contain
32044 anything, the @samp{recurse} option will be ignored.
32047 When the @samp{--available} option is passed, limited information may
32048 be available. In particular, the list of threads of a process might
32049 be inaccessible. Further, specifying specific thread groups might
32050 not give any performance advantage over listing all thread groups.
32051 The frontend should assume that @samp{-list-thread-groups --available}
32052 is always an expensive operation and cache the results.
32056 The @samp{groups} result is a list of tuples, where each tuple may
32057 have the following fields:
32061 Identifier of the thread group. This field is always present.
32062 The identifier is an opaque string; frontends should not try to
32063 convert it to an integer, even though it might look like one.
32066 The type of the thread group. At present, only @samp{process} is a
32070 The target-specific process identifier. This field is only present
32071 for thread groups of type @samp{process} and only if the process exists.
32074 The exit code of this group's last exited thread, formatted in octal.
32075 This field is only present for thread groups of type @samp{process} and
32076 only if the process is not running.
32079 The number of children this thread group has. This field may be
32080 absent for an available thread group.
32083 This field has a list of tuples as value, each tuple describing a
32084 thread. It may be present if the @samp{--recurse} option is
32085 specified, and it's actually possible to obtain the threads.
32088 This field is a list of integers, each identifying a core that one
32089 thread of the group is running on. This field may be absent if
32090 such information is not available.
32093 The name of the executable file that corresponds to this thread group.
32094 The field is only present for thread groups of type @samp{process},
32095 and only if there is a corresponding executable file.
32099 @subheading Example
32103 -list-thread-groups
32104 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
32105 -list-thread-groups 17
32106 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
32107 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
32108 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
32109 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
32110 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
32111 -list-thread-groups --available
32112 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
32113 -list-thread-groups --available --recurse 1
32114 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32115 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32116 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
32117 -list-thread-groups --available --recurse 1 17 18
32118 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
32119 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
32120 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
32123 @subheading The @code{-info-os} Command
32126 @subsubheading Synopsis
32129 -info-os [ @var{type} ]
32132 If no argument is supplied, the command returns a table of available
32133 operating-system-specific information types. If one of these types is
32134 supplied as an argument @var{type}, then the command returns a table
32135 of data of that type.
32137 The types of information available depend on the target operating
32140 @subsubheading @value{GDBN} Command
32142 The corresponding @value{GDBN} command is @samp{info os}.
32144 @subsubheading Example
32146 When run on a @sc{gnu}/Linux system, the output will look something
32152 ^done,OSDataTable=@{nr_rows="10",nr_cols="3",
32153 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
32154 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
32155 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
32156 body=[item=@{col0="cpus",col1="Listing of all cpus/cores on the system",
32158 item=@{col0="files",col1="Listing of all file descriptors",
32159 col2="File descriptors"@},
32160 item=@{col0="modules",col1="Listing of all loaded kernel modules",
32161 col2="Kernel modules"@},
32162 item=@{col0="msg",col1="Listing of all message queues",
32163 col2="Message queues"@},
32164 item=@{col0="processes",col1="Listing of all processes",
32165 col2="Processes"@},
32166 item=@{col0="procgroups",col1="Listing of all process groups",
32167 col2="Process groups"@},
32168 item=@{col0="semaphores",col1="Listing of all semaphores",
32169 col2="Semaphores"@},
32170 item=@{col0="shm",col1="Listing of all shared-memory regions",
32171 col2="Shared-memory regions"@},
32172 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
32174 item=@{col0="threads",col1="Listing of all threads",
32178 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
32179 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
32180 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
32181 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
32182 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
32183 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
32184 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
32185 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
32187 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
32188 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
32192 (Note that the MI output here includes a @code{"Title"} column that
32193 does not appear in command-line @code{info os}; this column is useful
32194 for MI clients that want to enumerate the types of data, such as in a
32195 popup menu, but is needless clutter on the command line, and
32196 @code{info os} omits it.)
32198 @subheading The @code{-add-inferior} Command
32199 @findex -add-inferior
32201 @subheading Synopsis
32207 Creates a new inferior (@pxref{Inferiors and Programs}). The created
32208 inferior is not associated with any executable. Such association may
32209 be established with the @samp{-file-exec-and-symbols} command
32210 (@pxref{GDB/MI File Commands}). The command response has a single
32211 field, @samp{inferior}, whose value is the identifier of the
32212 thread group corresponding to the new inferior.
32214 @subheading Example
32219 ^done,inferior="i3"
32222 @subheading The @code{-interpreter-exec} Command
32223 @findex -interpreter-exec
32225 @subheading Synopsis
32228 -interpreter-exec @var{interpreter} @var{command}
32230 @anchor{-interpreter-exec}
32232 Execute the specified @var{command} in the given @var{interpreter}.
32234 @subheading @value{GDBN} Command
32236 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
32238 @subheading Example
32242 -interpreter-exec console "break main"
32243 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
32244 &"During symbol reading, bad structure-type format.\n"
32245 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
32250 @subheading The @code{-inferior-tty-set} Command
32251 @findex -inferior-tty-set
32253 @subheading Synopsis
32256 -inferior-tty-set /dev/pts/1
32259 Set terminal for future runs of the program being debugged.
32261 @subheading @value{GDBN} Command
32263 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
32265 @subheading Example
32269 -inferior-tty-set /dev/pts/1
32274 @subheading The @code{-inferior-tty-show} Command
32275 @findex -inferior-tty-show
32277 @subheading Synopsis
32283 Show terminal for future runs of program being debugged.
32285 @subheading @value{GDBN} Command
32287 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
32289 @subheading Example
32293 -inferior-tty-set /dev/pts/1
32297 ^done,inferior_tty_terminal="/dev/pts/1"
32301 @subheading The @code{-enable-timings} Command
32302 @findex -enable-timings
32304 @subheading Synopsis
32307 -enable-timings [yes | no]
32310 Toggle the printing of the wallclock, user and system times for an MI
32311 command as a field in its output. This command is to help frontend
32312 developers optimize the performance of their code. No argument is
32313 equivalent to @samp{yes}.
32315 @subheading @value{GDBN} Command
32319 @subheading Example
32327 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
32328 addr="0x080484ed",func="main",file="myprog.c",
32329 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
32331 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
32339 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
32340 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
32341 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
32342 fullname="/home/nickrob/myprog.c",line="73"@}
32347 @chapter @value{GDBN} Annotations
32349 This chapter describes annotations in @value{GDBN}. Annotations were
32350 designed to interface @value{GDBN} to graphical user interfaces or other
32351 similar programs which want to interact with @value{GDBN} at a
32352 relatively high level.
32354 The annotation mechanism has largely been superseded by @sc{gdb/mi}
32358 This is Edition @value{EDITION}, @value{DATE}.
32362 * Annotations Overview:: What annotations are; the general syntax.
32363 * Server Prefix:: Issuing a command without affecting user state.
32364 * Prompting:: Annotations marking @value{GDBN}'s need for input.
32365 * Errors:: Annotations for error messages.
32366 * Invalidation:: Some annotations describe things now invalid.
32367 * Annotations for Running::
32368 Whether the program is running, how it stopped, etc.
32369 * Source Annotations:: Annotations describing source code.
32372 @node Annotations Overview
32373 @section What is an Annotation?
32374 @cindex annotations
32376 Annotations start with a newline character, two @samp{control-z}
32377 characters, and the name of the annotation. If there is no additional
32378 information associated with this annotation, the name of the annotation
32379 is followed immediately by a newline. If there is additional
32380 information, the name of the annotation is followed by a space, the
32381 additional information, and a newline. The additional information
32382 cannot contain newline characters.
32384 Any output not beginning with a newline and two @samp{control-z}
32385 characters denotes literal output from @value{GDBN}. Currently there is
32386 no need for @value{GDBN} to output a newline followed by two
32387 @samp{control-z} characters, but if there was such a need, the
32388 annotations could be extended with an @samp{escape} annotation which
32389 means those three characters as output.
32391 The annotation @var{level}, which is specified using the
32392 @option{--annotate} command line option (@pxref{Mode Options}), controls
32393 how much information @value{GDBN} prints together with its prompt,
32394 values of expressions, source lines, and other types of output. Level 0
32395 is for no annotations, level 1 is for use when @value{GDBN} is run as a
32396 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
32397 for programs that control @value{GDBN}, and level 2 annotations have
32398 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
32399 Interface, annotate, GDB's Obsolete Annotations}).
32402 @kindex set annotate
32403 @item set annotate @var{level}
32404 The @value{GDBN} command @code{set annotate} sets the level of
32405 annotations to the specified @var{level}.
32407 @item show annotate
32408 @kindex show annotate
32409 Show the current annotation level.
32412 This chapter describes level 3 annotations.
32414 A simple example of starting up @value{GDBN} with annotations is:
32417 $ @kbd{gdb --annotate=3}
32419 Copyright 2003 Free Software Foundation, Inc.
32420 GDB is free software, covered by the GNU General Public License,
32421 and you are welcome to change it and/or distribute copies of it
32422 under certain conditions.
32423 Type "show copying" to see the conditions.
32424 There is absolutely no warranty for GDB. Type "show warranty"
32426 This GDB was configured as "i386-pc-linux-gnu"
32437 Here @samp{quit} is input to @value{GDBN}; the rest is output from
32438 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
32439 denotes a @samp{control-z} character) are annotations; the rest is
32440 output from @value{GDBN}.
32442 @node Server Prefix
32443 @section The Server Prefix
32444 @cindex server prefix
32446 If you prefix a command with @samp{server } then it will not affect
32447 the command history, nor will it affect @value{GDBN}'s notion of which
32448 command to repeat if @key{RET} is pressed on a line by itself. This
32449 means that commands can be run behind a user's back by a front-end in
32450 a transparent manner.
32452 The @code{server } prefix does not affect the recording of values into
32453 the value history; to print a value without recording it into the
32454 value history, use the @code{output} command instead of the
32455 @code{print} command.
32457 Using this prefix also disables confirmation requests
32458 (@pxref{confirmation requests}).
32461 @section Annotation for @value{GDBN} Input
32463 @cindex annotations for prompts
32464 When @value{GDBN} prompts for input, it annotates this fact so it is possible
32465 to know when to send output, when the output from a given command is
32468 Different kinds of input each have a different @dfn{input type}. Each
32469 input type has three annotations: a @code{pre-} annotation, which
32470 denotes the beginning of any prompt which is being output, a plain
32471 annotation, which denotes the end of the prompt, and then a @code{post-}
32472 annotation which denotes the end of any echo which may (or may not) be
32473 associated with the input. For example, the @code{prompt} input type
32474 features the following annotations:
32482 The input types are
32485 @findex pre-prompt annotation
32486 @findex prompt annotation
32487 @findex post-prompt annotation
32489 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
32491 @findex pre-commands annotation
32492 @findex commands annotation
32493 @findex post-commands annotation
32495 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
32496 command. The annotations are repeated for each command which is input.
32498 @findex pre-overload-choice annotation
32499 @findex overload-choice annotation
32500 @findex post-overload-choice annotation
32501 @item overload-choice
32502 When @value{GDBN} wants the user to select between various overloaded functions.
32504 @findex pre-query annotation
32505 @findex query annotation
32506 @findex post-query annotation
32508 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
32510 @findex pre-prompt-for-continue annotation
32511 @findex prompt-for-continue annotation
32512 @findex post-prompt-for-continue annotation
32513 @item prompt-for-continue
32514 When @value{GDBN} is asking the user to press return to continue. Note: Don't
32515 expect this to work well; instead use @code{set height 0} to disable
32516 prompting. This is because the counting of lines is buggy in the
32517 presence of annotations.
32522 @cindex annotations for errors, warnings and interrupts
32524 @findex quit annotation
32529 This annotation occurs right before @value{GDBN} responds to an interrupt.
32531 @findex error annotation
32536 This annotation occurs right before @value{GDBN} responds to an error.
32538 Quit and error annotations indicate that any annotations which @value{GDBN} was
32539 in the middle of may end abruptly. For example, if a
32540 @code{value-history-begin} annotation is followed by a @code{error}, one
32541 cannot expect to receive the matching @code{value-history-end}. One
32542 cannot expect not to receive it either, however; an error annotation
32543 does not necessarily mean that @value{GDBN} is immediately returning all the way
32546 @findex error-begin annotation
32547 A quit or error annotation may be preceded by
32553 Any output between that and the quit or error annotation is the error
32556 Warning messages are not yet annotated.
32557 @c If we want to change that, need to fix warning(), type_error(),
32558 @c range_error(), and possibly other places.
32561 @section Invalidation Notices
32563 @cindex annotations for invalidation messages
32564 The following annotations say that certain pieces of state may have
32568 @findex frames-invalid annotation
32569 @item ^Z^Zframes-invalid
32571 The frames (for example, output from the @code{backtrace} command) may
32574 @findex breakpoints-invalid annotation
32575 @item ^Z^Zbreakpoints-invalid
32577 The breakpoints may have changed. For example, the user just added or
32578 deleted a breakpoint.
32581 @node Annotations for Running
32582 @section Running the Program
32583 @cindex annotations for running programs
32585 @findex starting annotation
32586 @findex stopping annotation
32587 When the program starts executing due to a @value{GDBN} command such as
32588 @code{step} or @code{continue},
32594 is output. When the program stops,
32600 is output. Before the @code{stopped} annotation, a variety of
32601 annotations describe how the program stopped.
32604 @findex exited annotation
32605 @item ^Z^Zexited @var{exit-status}
32606 The program exited, and @var{exit-status} is the exit status (zero for
32607 successful exit, otherwise nonzero).
32609 @findex signalled annotation
32610 @findex signal-name annotation
32611 @findex signal-name-end annotation
32612 @findex signal-string annotation
32613 @findex signal-string-end annotation
32614 @item ^Z^Zsignalled
32615 The program exited with a signal. After the @code{^Z^Zsignalled}, the
32616 annotation continues:
32622 ^Z^Zsignal-name-end
32626 ^Z^Zsignal-string-end
32631 where @var{name} is the name of the signal, such as @code{SIGILL} or
32632 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32633 as @code{Illegal Instruction} or @code{Segmentation fault}. The arguments
32634 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32635 user's benefit and have no particular format.
32637 @findex signal annotation
32639 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32640 just saying that the program received the signal, not that it was
32641 terminated with it.
32643 @findex breakpoint annotation
32644 @item ^Z^Zbreakpoint @var{number}
32645 The program hit breakpoint number @var{number}.
32647 @findex watchpoint annotation
32648 @item ^Z^Zwatchpoint @var{number}
32649 The program hit watchpoint number @var{number}.
32652 @node Source Annotations
32653 @section Displaying Source
32654 @cindex annotations for source display
32656 @findex source annotation
32657 The following annotation is used instead of displaying source code:
32660 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32663 where @var{filename} is an absolute file name indicating which source
32664 file, @var{line} is the line number within that file (where 1 is the
32665 first line in the file), @var{character} is the character position
32666 within the file (where 0 is the first character in the file) (for most
32667 debug formats this will necessarily point to the beginning of a line),
32668 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32669 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32670 @var{addr} is the address in the target program associated with the
32671 source which is being displayed. The @var{addr} is in the form @samp{0x}
32672 followed by one or more lowercase hex digits (note that this does not
32673 depend on the language).
32675 @node JIT Interface
32676 @chapter JIT Compilation Interface
32677 @cindex just-in-time compilation
32678 @cindex JIT compilation interface
32680 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32681 interface. A JIT compiler is a program or library that generates native
32682 executable code at runtime and executes it, usually in order to achieve good
32683 performance while maintaining platform independence.
32685 Programs that use JIT compilation are normally difficult to debug because
32686 portions of their code are generated at runtime, instead of being loaded from
32687 object files, which is where @value{GDBN} normally finds the program's symbols
32688 and debug information. In order to debug programs that use JIT compilation,
32689 @value{GDBN} has an interface that allows the program to register in-memory
32690 symbol files with @value{GDBN} at runtime.
32692 If you are using @value{GDBN} to debug a program that uses this interface, then
32693 it should work transparently so long as you have not stripped the binary. If
32694 you are developing a JIT compiler, then the interface is documented in the rest
32695 of this chapter. At this time, the only known client of this interface is the
32698 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32699 JIT compiler communicates with @value{GDBN} by writing data into a global
32700 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32701 attaches, it reads a linked list of symbol files from the global variable to
32702 find existing code, and puts a breakpoint in the function so that it can find
32703 out about additional code.
32706 * Declarations:: Relevant C struct declarations
32707 * Registering Code:: Steps to register code
32708 * Unregistering Code:: Steps to unregister code
32709 * Custom Debug Info:: Emit debug information in a custom format
32713 @section JIT Declarations
32715 These are the relevant struct declarations that a C program should include to
32716 implement the interface:
32726 struct jit_code_entry
32728 struct jit_code_entry *next_entry;
32729 struct jit_code_entry *prev_entry;
32730 const char *symfile_addr;
32731 uint64_t symfile_size;
32734 struct jit_descriptor
32737 /* This type should be jit_actions_t, but we use uint32_t
32738 to be explicit about the bitwidth. */
32739 uint32_t action_flag;
32740 struct jit_code_entry *relevant_entry;
32741 struct jit_code_entry *first_entry;
32744 /* GDB puts a breakpoint in this function. */
32745 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32747 /* Make sure to specify the version statically, because the
32748 debugger may check the version before we can set it. */
32749 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32752 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32753 modifications to this global data properly, which can easily be done by putting
32754 a global mutex around modifications to these structures.
32756 @node Registering Code
32757 @section Registering Code
32759 To register code with @value{GDBN}, the JIT should follow this protocol:
32763 Generate an object file in memory with symbols and other desired debug
32764 information. The file must include the virtual addresses of the sections.
32767 Create a code entry for the file, which gives the start and size of the symbol
32771 Add it to the linked list in the JIT descriptor.
32774 Point the relevant_entry field of the descriptor at the entry.
32777 Set @code{action_flag} to @code{JIT_REGISTER} and call
32778 @code{__jit_debug_register_code}.
32781 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32782 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32783 new code. However, the linked list must still be maintained in order to allow
32784 @value{GDBN} to attach to a running process and still find the symbol files.
32786 @node Unregistering Code
32787 @section Unregistering Code
32789 If code is freed, then the JIT should use the following protocol:
32793 Remove the code entry corresponding to the code from the linked list.
32796 Point the @code{relevant_entry} field of the descriptor at the code entry.
32799 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32800 @code{__jit_debug_register_code}.
32803 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32804 and the JIT will leak the memory used for the associated symbol files.
32806 @node Custom Debug Info
32807 @section Custom Debug Info
32808 @cindex custom JIT debug info
32809 @cindex JIT debug info reader
32811 Generating debug information in platform-native file formats (like ELF
32812 or COFF) may be an overkill for JIT compilers; especially if all the
32813 debug info is used for is displaying a meaningful backtrace. The
32814 issue can be resolved by having the JIT writers decide on a debug info
32815 format and also provide a reader that parses the debug info generated
32816 by the JIT compiler. This section gives a brief overview on writing
32817 such a parser. More specific details can be found in the source file
32818 @file{gdb/jit-reader.in}, which is also installed as a header at
32819 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32821 The reader is implemented as a shared object (so this functionality is
32822 not available on platforms which don't allow loading shared objects at
32823 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32824 @code{jit-reader-unload} are provided, to be used to load and unload
32825 the readers from a preconfigured directory. Once loaded, the shared
32826 object is used the parse the debug information emitted by the JIT
32830 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32831 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32834 @node Using JIT Debug Info Readers
32835 @subsection Using JIT Debug Info Readers
32836 @kindex jit-reader-load
32837 @kindex jit-reader-unload
32839 Readers can be loaded and unloaded using the @code{jit-reader-load}
32840 and @code{jit-reader-unload} commands.
32843 @item jit-reader-load @var{reader}
32844 Load the JIT reader named @var{reader}, which is a shared
32845 object specified as either an absolute or a relative file name. In
32846 the latter case, @value{GDBN} will try to load the reader from a
32847 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
32848 system (here @var{libdir} is the system library directory, often
32849 @file{/usr/local/lib}).
32851 Only one reader can be active at a time; trying to load a second
32852 reader when one is already loaded will result in @value{GDBN}
32853 reporting an error. A new JIT reader can be loaded by first unloading
32854 the current one using @code{jit-reader-unload} and then invoking
32855 @code{jit-reader-load}.
32857 @item jit-reader-unload
32858 Unload the currently loaded JIT reader.
32862 @node Writing JIT Debug Info Readers
32863 @subsection Writing JIT Debug Info Readers
32864 @cindex writing JIT debug info readers
32866 As mentioned, a reader is essentially a shared object conforming to a
32867 certain ABI. This ABI is described in @file{jit-reader.h}.
32869 @file{jit-reader.h} defines the structures, macros and functions
32870 required to write a reader. It is installed (along with
32871 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32872 the system include directory.
32874 Readers need to be released under a GPL compatible license. A reader
32875 can be declared as released under such a license by placing the macro
32876 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32878 The entry point for readers is the symbol @code{gdb_init_reader},
32879 which is expected to be a function with the prototype
32881 @findex gdb_init_reader
32883 extern struct gdb_reader_funcs *gdb_init_reader (void);
32886 @cindex @code{struct gdb_reader_funcs}
32888 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32889 functions. These functions are executed to read the debug info
32890 generated by the JIT compiler (@code{read}), to unwind stack frames
32891 (@code{unwind}) and to create canonical frame IDs
32892 (@code{get_Frame_id}). It also has a callback that is called when the
32893 reader is being unloaded (@code{destroy}). The struct looks like this
32896 struct gdb_reader_funcs
32898 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32899 int reader_version;
32901 /* For use by the reader. */
32904 gdb_read_debug_info *read;
32905 gdb_unwind_frame *unwind;
32906 gdb_get_frame_id *get_frame_id;
32907 gdb_destroy_reader *destroy;
32911 @cindex @code{struct gdb_symbol_callbacks}
32912 @cindex @code{struct gdb_unwind_callbacks}
32914 The callbacks are provided with another set of callbacks by
32915 @value{GDBN} to do their job. For @code{read}, these callbacks are
32916 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32917 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32918 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32919 files and new symbol tables inside those object files. @code{struct
32920 gdb_unwind_callbacks} has callbacks to read registers off the current
32921 frame and to write out the values of the registers in the previous
32922 frame. Both have a callback (@code{target_read}) to read bytes off the
32923 target's address space.
32925 @node In-Process Agent
32926 @chapter In-Process Agent
32927 @cindex debugging agent
32928 The traditional debugging model is conceptually low-speed, but works fine,
32929 because most bugs can be reproduced in debugging-mode execution. However,
32930 as multi-core or many-core processors are becoming mainstream, and
32931 multi-threaded programs become more and more popular, there should be more
32932 and more bugs that only manifest themselves at normal-mode execution, for
32933 example, thread races, because debugger's interference with the program's
32934 timing may conceal the bugs. On the other hand, in some applications,
32935 it is not feasible for the debugger to interrupt the program's execution
32936 long enough for the developer to learn anything helpful about its behavior.
32937 If the program's correctness depends on its real-time behavior, delays
32938 introduced by a debugger might cause the program to fail, even when the
32939 code itself is correct. It is useful to be able to observe the program's
32940 behavior without interrupting it.
32942 Therefore, traditional debugging model is too intrusive to reproduce
32943 some bugs. In order to reduce the interference with the program, we can
32944 reduce the number of operations performed by debugger. The
32945 @dfn{In-Process Agent}, a shared library, is running within the same
32946 process with inferior, and is able to perform some debugging operations
32947 itself. As a result, debugger is only involved when necessary, and
32948 performance of debugging can be improved accordingly. Note that
32949 interference with program can be reduced but can't be removed completely,
32950 because the in-process agent will still stop or slow down the program.
32952 The in-process agent can interpret and execute Agent Expressions
32953 (@pxref{Agent Expressions}) during performing debugging operations. The
32954 agent expressions can be used for different purposes, such as collecting
32955 data in tracepoints, and condition evaluation in breakpoints.
32957 @anchor{Control Agent}
32958 You can control whether the in-process agent is used as an aid for
32959 debugging with the following commands:
32962 @kindex set agent on
32964 Causes the in-process agent to perform some operations on behalf of the
32965 debugger. Just which operations requested by the user will be done
32966 by the in-process agent depends on the its capabilities. For example,
32967 if you request to evaluate breakpoint conditions in the in-process agent,
32968 and the in-process agent has such capability as well, then breakpoint
32969 conditions will be evaluated in the in-process agent.
32971 @kindex set agent off
32972 @item set agent off
32973 Disables execution of debugging operations by the in-process agent. All
32974 of the operations will be performed by @value{GDBN}.
32978 Display the current setting of execution of debugging operations by
32979 the in-process agent.
32983 * In-Process Agent Protocol::
32986 @node In-Process Agent Protocol
32987 @section In-Process Agent Protocol
32988 @cindex in-process agent protocol
32990 The in-process agent is able to communicate with both @value{GDBN} and
32991 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
32992 used for communications between @value{GDBN} or GDBserver and the IPA.
32993 In general, @value{GDBN} or GDBserver sends commands
32994 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
32995 in-process agent replies back with the return result of the command, or
32996 some other information. The data sent to in-process agent is composed
32997 of primitive data types, such as 4-byte or 8-byte type, and composite
32998 types, which are called objects (@pxref{IPA Protocol Objects}).
33001 * IPA Protocol Objects::
33002 * IPA Protocol Commands::
33005 @node IPA Protocol Objects
33006 @subsection IPA Protocol Objects
33007 @cindex ipa protocol objects
33009 The commands sent to and results received from agent may contain some
33010 complex data types called @dfn{objects}.
33012 The in-process agent is running on the same machine with @value{GDBN}
33013 or GDBserver, so it doesn't have to handle as much differences between
33014 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
33015 However, there are still some differences of two ends in two processes:
33019 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
33020 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
33022 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
33023 GDBserver is compiled with one, and in-process agent is compiled with
33027 Here are the IPA Protocol Objects:
33031 agent expression object. It represents an agent expression
33032 (@pxref{Agent Expressions}).
33033 @anchor{agent expression object}
33035 tracepoint action object. It represents a tracepoint action
33036 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
33037 memory, static trace data and to evaluate expression.
33038 @anchor{tracepoint action object}
33040 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
33041 @anchor{tracepoint object}
33045 The following table describes important attributes of each IPA protocol
33048 @multitable @columnfractions .30 .20 .50
33049 @headitem Name @tab Size @tab Description
33050 @item @emph{agent expression object} @tab @tab
33051 @item length @tab 4 @tab length of bytes code
33052 @item byte code @tab @var{length} @tab contents of byte code
33053 @item @emph{tracepoint action for collecting memory} @tab @tab
33054 @item 'M' @tab 1 @tab type of tracepoint action
33055 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
33056 address of the lowest byte to collect, otherwise @var{addr} is the offset
33057 of @var{basereg} for memory collecting.
33058 @item len @tab 8 @tab length of memory for collecting
33059 @item basereg @tab 4 @tab the register number containing the starting
33060 memory address for collecting.
33061 @item @emph{tracepoint action for collecting registers} @tab @tab
33062 @item 'R' @tab 1 @tab type of tracepoint action
33063 @item @emph{tracepoint action for collecting static trace data} @tab @tab
33064 @item 'L' @tab 1 @tab type of tracepoint action
33065 @item @emph{tracepoint action for expression evaluation} @tab @tab
33066 @item 'X' @tab 1 @tab type of tracepoint action
33067 @item agent expression @tab length of @tab @ref{agent expression object}
33068 @item @emph{tracepoint object} @tab @tab
33069 @item number @tab 4 @tab number of tracepoint
33070 @item address @tab 8 @tab address of tracepoint inserted on
33071 @item type @tab 4 @tab type of tracepoint
33072 @item enabled @tab 1 @tab enable or disable of tracepoint
33073 @item step_count @tab 8 @tab step
33074 @item pass_count @tab 8 @tab pass
33075 @item numactions @tab 4 @tab number of tracepoint actions
33076 @item hit count @tab 8 @tab hit count
33077 @item trace frame usage @tab 8 @tab trace frame usage
33078 @item compiled_cond @tab 8 @tab compiled condition
33079 @item orig_size @tab 8 @tab orig size
33080 @item condition @tab 4 if condition is NULL otherwise length of
33081 @ref{agent expression object}
33082 @tab zero if condition is NULL, otherwise is
33083 @ref{agent expression object}
33084 @item actions @tab variable
33085 @tab numactions number of @ref{tracepoint action object}
33088 @node IPA Protocol Commands
33089 @subsection IPA Protocol Commands
33090 @cindex ipa protocol commands
33092 The spaces in each command are delimiters to ease reading this commands
33093 specification. They don't exist in real commands.
33097 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
33098 Installs a new fast tracepoint described by @var{tracepoint_object}
33099 (@pxref{tracepoint object}). The @var{gdb_jump_pad_head}, 8-byte long, is the
33100 head of @dfn{jumppad}, which is used to jump to data collection routine
33105 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
33106 @var{target_address} is address of tracepoint in the inferior.
33107 The @var{gdb_jump_pad_head} is updated head of jumppad. Both of
33108 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
33109 The @var{fjump} contains a sequence of instructions jump to jumppad entry.
33110 The @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
33117 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
33118 is about to kill inferiors.
33126 @item probe_marker_at:@var{address}
33127 Asks in-process agent to probe the marker at @var{address}.
33134 @item unprobe_marker_at:@var{address}
33135 Asks in-process agent to unprobe the marker at @var{address}.
33139 @chapter Reporting Bugs in @value{GDBN}
33140 @cindex bugs in @value{GDBN}
33141 @cindex reporting bugs in @value{GDBN}
33143 Your bug reports play an essential role in making @value{GDBN} reliable.
33145 Reporting a bug may help you by bringing a solution to your problem, or it
33146 may not. But in any case the principal function of a bug report is to help
33147 the entire community by making the next version of @value{GDBN} work better. Bug
33148 reports are your contribution to the maintenance of @value{GDBN}.
33150 In order for a bug report to serve its purpose, you must include the
33151 information that enables us to fix the bug.
33154 * Bug Criteria:: Have you found a bug?
33155 * Bug Reporting:: How to report bugs
33159 @section Have You Found a Bug?
33160 @cindex bug criteria
33162 If you are not sure whether you have found a bug, here are some guidelines:
33165 @cindex fatal signal
33166 @cindex debugger crash
33167 @cindex crash of debugger
33169 If the debugger gets a fatal signal, for any input whatever, that is a
33170 @value{GDBN} bug. Reliable debuggers never crash.
33172 @cindex error on valid input
33174 If @value{GDBN} produces an error message for valid input, that is a
33175 bug. (Note that if you're cross debugging, the problem may also be
33176 somewhere in the connection to the target.)
33178 @cindex invalid input
33180 If @value{GDBN} does not produce an error message for invalid input,
33181 that is a bug. However, you should note that your idea of
33182 ``invalid input'' might be our idea of ``an extension'' or ``support
33183 for traditional practice''.
33186 If you are an experienced user of debugging tools, your suggestions
33187 for improvement of @value{GDBN} are welcome in any case.
33190 @node Bug Reporting
33191 @section How to Report Bugs
33192 @cindex bug reports
33193 @cindex @value{GDBN} bugs, reporting
33195 A number of companies and individuals offer support for @sc{gnu} products.
33196 If you obtained @value{GDBN} from a support organization, we recommend you
33197 contact that organization first.
33199 You can find contact information for many support companies and
33200 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
33202 @c should add a web page ref...
33205 @ifset BUGURL_DEFAULT
33206 In any event, we also recommend that you submit bug reports for
33207 @value{GDBN}. The preferred method is to submit them directly using
33208 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
33209 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
33212 @strong{Do not send bug reports to @samp{info-gdb}, or to
33213 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
33214 not want to receive bug reports. Those that do have arranged to receive
33217 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
33218 serves as a repeater. The mailing list and the newsgroup carry exactly
33219 the same messages. Often people think of posting bug reports to the
33220 newsgroup instead of mailing them. This appears to work, but it has one
33221 problem which can be crucial: a newsgroup posting often lacks a mail
33222 path back to the sender. Thus, if we need to ask for more information,
33223 we may be unable to reach you. For this reason, it is better to send
33224 bug reports to the mailing list.
33226 @ifclear BUGURL_DEFAULT
33227 In any event, we also recommend that you submit bug reports for
33228 @value{GDBN} to @value{BUGURL}.
33232 The fundamental principle of reporting bugs usefully is this:
33233 @strong{report all the facts}. If you are not sure whether to state a
33234 fact or leave it out, state it!
33236 Often people omit facts because they think they know what causes the
33237 problem and assume that some details do not matter. Thus, you might
33238 assume that the name of the variable you use in an example does not matter.
33239 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
33240 stray memory reference which happens to fetch from the location where that
33241 name is stored in memory; perhaps, if the name were different, the contents
33242 of that location would fool the debugger into doing the right thing despite
33243 the bug. Play it safe and give a specific, complete example. That is the
33244 easiest thing for you to do, and the most helpful.
33246 Keep in mind that the purpose of a bug report is to enable us to fix the
33247 bug. It may be that the bug has been reported previously, but neither
33248 you nor we can know that unless your bug report is complete and
33251 Sometimes people give a few sketchy facts and ask, ``Does this ring a
33252 bell?'' Those bug reports are useless, and we urge everyone to
33253 @emph{refuse to respond to them} except to chide the sender to report
33256 To enable us to fix the bug, you should include all these things:
33260 The version of @value{GDBN}. @value{GDBN} announces it if you start
33261 with no arguments; you can also print it at any time using @code{show
33264 Without this, we will not know whether there is any point in looking for
33265 the bug in the current version of @value{GDBN}.
33268 The type of machine you are using, and the operating system name and
33272 The details of the @value{GDBN} build-time configuration.
33273 @value{GDBN} shows these details if you invoke it with the
33274 @option{--configuration} command-line option, or if you type
33275 @code{show configuration} at @value{GDBN}'s prompt.
33278 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
33279 ``@value{GCC}--2.8.1''.
33282 What compiler (and its version) was used to compile the program you are
33283 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
33284 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
33285 to get this information; for other compilers, see the documentation for
33289 The command arguments you gave the compiler to compile your example and
33290 observe the bug. For example, did you use @samp{-O}? To guarantee
33291 you will not omit something important, list them all. A copy of the
33292 Makefile (or the output from make) is sufficient.
33294 If we were to try to guess the arguments, we would probably guess wrong
33295 and then we might not encounter the bug.
33298 A complete input script, and all necessary source files, that will
33302 A description of what behavior you observe that you believe is
33303 incorrect. For example, ``It gets a fatal signal.''
33305 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
33306 will certainly notice it. But if the bug is incorrect output, we might
33307 not notice unless it is glaringly wrong. You might as well not give us
33308 a chance to make a mistake.
33310 Even if the problem you experience is a fatal signal, you should still
33311 say so explicitly. Suppose something strange is going on, such as, your
33312 copy of @value{GDBN} is out of synch, or you have encountered a bug in
33313 the C library on your system. (This has happened!) Your copy might
33314 crash and ours would not. If you told us to expect a crash, then when
33315 ours fails to crash, we would know that the bug was not happening for
33316 us. If you had not told us to expect a crash, then we would not be able
33317 to draw any conclusion from our observations.
33320 @cindex recording a session script
33321 To collect all this information, you can use a session recording program
33322 such as @command{script}, which is available on many Unix systems.
33323 Just run your @value{GDBN} session inside @command{script} and then
33324 include the @file{typescript} file with your bug report.
33326 Another way to record a @value{GDBN} session is to run @value{GDBN}
33327 inside Emacs and then save the entire buffer to a file.
33330 If you wish to suggest changes to the @value{GDBN} source, send us context
33331 diffs. If you even discuss something in the @value{GDBN} source, refer to
33332 it by context, not by line number.
33334 The line numbers in our development sources will not match those in your
33335 sources. Your line numbers would convey no useful information to us.
33339 Here are some things that are not necessary:
33343 A description of the envelope of the bug.
33345 Often people who encounter a bug spend a lot of time investigating
33346 which changes to the input file will make the bug go away and which
33347 changes will not affect it.
33349 This is often time consuming and not very useful, because the way we
33350 will find the bug is by running a single example under the debugger
33351 with breakpoints, not by pure deduction from a series of examples.
33352 We recommend that you save your time for something else.
33354 Of course, if you can find a simpler example to report @emph{instead}
33355 of the original one, that is a convenience for us. Errors in the
33356 output will be easier to spot, running under the debugger will take
33357 less time, and so on.
33359 However, simplification is not vital; if you do not want to do this,
33360 report the bug anyway and send us the entire test case you used.
33363 A patch for the bug.
33365 A patch for the bug does help us if it is a good one. But do not omit
33366 the necessary information, such as the test case, on the assumption that
33367 a patch is all we need. We might see problems with your patch and decide
33368 to fix the problem another way, or we might not understand it at all.
33370 Sometimes with a program as complicated as @value{GDBN} it is very hard to
33371 construct an example that will make the program follow a certain path
33372 through the code. If you do not send us the example, we will not be able
33373 to construct one, so we will not be able to verify that the bug is fixed.
33375 And if we cannot understand what bug you are trying to fix, or why your
33376 patch should be an improvement, we will not install it. A test case will
33377 help us to understand.
33380 A guess about what the bug is or what it depends on.
33382 Such guesses are usually wrong. Even we cannot guess right about such
33383 things without first using the debugger to find the facts.
33386 @c The readline documentation is distributed with the readline code
33387 @c and consists of the two following files:
33390 @c Use -I with makeinfo to point to the appropriate directory,
33391 @c environment var TEXINPUTS with TeX.
33392 @ifclear SYSTEM_READLINE
33393 @include rluser.texi
33394 @include hsuser.texi
33398 @appendix In Memoriam
33400 The @value{GDBN} project mourns the loss of the following long-time
33405 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
33406 to Free Software in general. Outside of @value{GDBN}, he was known in
33407 the Amiga world for his series of Fish Disks, and the GeekGadget project.
33409 @item Michael Snyder
33410 Michael was one of the Global Maintainers of the @value{GDBN} project,
33411 with contributions recorded as early as 1996, until 2011. In addition
33412 to his day to day participation, he was a large driving force behind
33413 adding Reverse Debugging to @value{GDBN}.
33416 Beyond their technical contributions to the project, they were also
33417 enjoyable members of the Free Software Community. We will miss them.
33419 @node Formatting Documentation
33420 @appendix Formatting Documentation
33422 @cindex @value{GDBN} reference card
33423 @cindex reference card
33424 The @value{GDBN} 4 release includes an already-formatted reference card, ready
33425 for printing with PostScript or Ghostscript, in the @file{gdb}
33426 subdirectory of the main source directory@footnote{In
33427 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
33428 release.}. If you can use PostScript or Ghostscript with your printer,
33429 you can print the reference card immediately with @file{refcard.ps}.
33431 The release also includes the source for the reference card. You
33432 can format it, using @TeX{}, by typing:
33438 The @value{GDBN} reference card is designed to print in @dfn{landscape}
33439 mode on US ``letter'' size paper;
33440 that is, on a sheet 11 inches wide by 8.5 inches
33441 high. You will need to specify this form of printing as an option to
33442 your @sc{dvi} output program.
33444 @cindex documentation
33446 All the documentation for @value{GDBN} comes as part of the machine-readable
33447 distribution. The documentation is written in Texinfo format, which is
33448 a documentation system that uses a single source file to produce both
33449 on-line information and a printed manual. You can use one of the Info
33450 formatting commands to create the on-line version of the documentation
33451 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
33453 @value{GDBN} includes an already formatted copy of the on-line Info
33454 version of this manual in the @file{gdb} subdirectory. The main Info
33455 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
33456 subordinate files matching @samp{gdb.info*} in the same directory. If
33457 necessary, you can print out these files, or read them with any editor;
33458 but they are easier to read using the @code{info} subsystem in @sc{gnu}
33459 Emacs or the standalone @code{info} program, available as part of the
33460 @sc{gnu} Texinfo distribution.
33462 If you want to format these Info files yourself, you need one of the
33463 Info formatting programs, such as @code{texinfo-format-buffer} or
33466 If you have @code{makeinfo} installed, and are in the top level
33467 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
33468 version @value{GDBVN}), you can make the Info file by typing:
33475 If you want to typeset and print copies of this manual, you need @TeX{},
33476 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
33477 Texinfo definitions file.
33479 @TeX{} is a typesetting program; it does not print files directly, but
33480 produces output files called @sc{dvi} files. To print a typeset
33481 document, you need a program to print @sc{dvi} files. If your system
33482 has @TeX{} installed, chances are it has such a program. The precise
33483 command to use depends on your system; @kbd{lpr -d} is common; another
33484 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
33485 require a file name without any extension or a @samp{.dvi} extension.
33487 @TeX{} also requires a macro definitions file called
33488 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
33489 written in Texinfo format. On its own, @TeX{} cannot either read or
33490 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
33491 and is located in the @file{gdb-@var{version-number}/texinfo}
33494 If you have @TeX{} and a @sc{dvi} printer program installed, you can
33495 typeset and print this manual. First switch to the @file{gdb}
33496 subdirectory of the main source directory (for example, to
33497 @file{gdb-@value{GDBVN}/gdb}) and type:
33503 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
33505 @node Installing GDB
33506 @appendix Installing @value{GDBN}
33507 @cindex installation
33510 * Requirements:: Requirements for building @value{GDBN}
33511 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
33512 * Separate Objdir:: Compiling @value{GDBN} in another directory
33513 * Config Names:: Specifying names for hosts and targets
33514 * Configure Options:: Summary of options for configure
33515 * System-wide configuration:: Having a system-wide init file
33519 @section Requirements for Building @value{GDBN}
33520 @cindex building @value{GDBN}, requirements for
33522 Building @value{GDBN} requires various tools and packages to be available.
33523 Other packages will be used only if they are found.
33525 @heading Tools/Packages Necessary for Building @value{GDBN}
33527 @item ISO C90 compiler
33528 @value{GDBN} is written in ISO C90. It should be buildable with any
33529 working C90 compiler, e.g.@: GCC.
33533 @heading Tools/Packages Optional for Building @value{GDBN}
33537 @value{GDBN} can use the Expat XML parsing library. This library may be
33538 included with your operating system distribution; if it is not, you
33539 can get the latest version from @url{http://expat.sourceforge.net}.
33540 The @file{configure} script will search for this library in several
33541 standard locations; if it is installed in an unusual path, you can
33542 use the @option{--with-libexpat-prefix} option to specify its location.
33548 Remote protocol memory maps (@pxref{Memory Map Format})
33550 Target descriptions (@pxref{Target Descriptions})
33552 Remote shared library lists (@xref{Library List Format},
33553 or alternatively @pxref{Library List Format for SVR4 Targets})
33555 MS-Windows shared libraries (@pxref{Shared Libraries})
33557 Traceframe info (@pxref{Traceframe Info Format})
33559 Branch trace (@pxref{Branch Trace Format},
33560 @pxref{Branch Trace Configuration Format})
33564 @cindex compressed debug sections
33565 @value{GDBN} will use the @samp{zlib} library, if available, to read
33566 compressed debug sections. Some linkers, such as GNU gold, are capable
33567 of producing binaries with compressed debug sections. If @value{GDBN}
33568 is compiled with @samp{zlib}, it will be able to read the debug
33569 information in such binaries.
33571 The @samp{zlib} library is likely included with your operating system
33572 distribution; if it is not, you can get the latest version from
33573 @url{http://zlib.net}.
33576 @value{GDBN}'s features related to character sets (@pxref{Character
33577 Sets}) require a functioning @code{iconv} implementation. If you are
33578 on a GNU system, then this is provided by the GNU C Library. Some
33579 other systems also provide a working @code{iconv}.
33581 If @value{GDBN} is using the @code{iconv} program which is installed
33582 in a non-standard place, you will need to tell @value{GDBN} where to find it.
33583 This is done with @option{--with-iconv-bin} which specifies the
33584 directory that contains the @code{iconv} program.
33586 On systems without @code{iconv}, you can install GNU Libiconv. If you
33587 have previously installed Libiconv, you can use the
33588 @option{--with-libiconv-prefix} option to configure.
33590 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
33591 arrange to build Libiconv if a directory named @file{libiconv} appears
33592 in the top-most source directory. If Libiconv is built this way, and
33593 if the operating system does not provide a suitable @code{iconv}
33594 implementation, then the just-built library will automatically be used
33595 by @value{GDBN}. One easy way to set this up is to download GNU
33596 Libiconv, unpack it, and then rename the directory holding the
33597 Libiconv source code to @samp{libiconv}.
33600 @node Running Configure
33601 @section Invoking the @value{GDBN} @file{configure} Script
33602 @cindex configuring @value{GDBN}
33603 @value{GDBN} comes with a @file{configure} script that automates the process
33604 of preparing @value{GDBN} for installation; you can then use @code{make} to
33605 build the @code{gdb} program.
33607 @c irrelevant in info file; it's as current as the code it lives with.
33608 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
33609 look at the @file{README} file in the sources; we may have improved the
33610 installation procedures since publishing this manual.}
33613 The @value{GDBN} distribution includes all the source code you need for
33614 @value{GDBN} in a single directory, whose name is usually composed by
33615 appending the version number to @samp{gdb}.
33617 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
33618 @file{gdb-@value{GDBVN}} directory. That directory contains:
33621 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
33622 script for configuring @value{GDBN} and all its supporting libraries
33624 @item gdb-@value{GDBVN}/gdb
33625 the source specific to @value{GDBN} itself
33627 @item gdb-@value{GDBVN}/bfd
33628 source for the Binary File Descriptor library
33630 @item gdb-@value{GDBVN}/include
33631 @sc{gnu} include files
33633 @item gdb-@value{GDBVN}/libiberty
33634 source for the @samp{-liberty} free software library
33636 @item gdb-@value{GDBVN}/opcodes
33637 source for the library of opcode tables and disassemblers
33639 @item gdb-@value{GDBVN}/readline
33640 source for the @sc{gnu} command-line interface
33642 @item gdb-@value{GDBVN}/glob
33643 source for the @sc{gnu} filename pattern-matching subroutine
33645 @item gdb-@value{GDBVN}/mmalloc
33646 source for the @sc{gnu} memory-mapped malloc package
33649 The simplest way to configure and build @value{GDBN} is to run @file{configure}
33650 from the @file{gdb-@var{version-number}} source directory, which in
33651 this example is the @file{gdb-@value{GDBVN}} directory.
33653 First switch to the @file{gdb-@var{version-number}} source directory
33654 if you are not already in it; then run @file{configure}. Pass the
33655 identifier for the platform on which @value{GDBN} will run as an
33661 cd gdb-@value{GDBVN}
33662 ./configure @var{host}
33667 where @var{host} is an identifier such as @samp{sun4} or
33668 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
33669 (You can often leave off @var{host}; @file{configure} tries to guess the
33670 correct value by examining your system.)
33672 Running @samp{configure @var{host}} and then running @code{make} builds the
33673 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
33674 libraries, then @code{gdb} itself. The configured source files, and the
33675 binaries, are left in the corresponding source directories.
33678 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
33679 system does not recognize this automatically when you run a different
33680 shell, you may need to run @code{sh} on it explicitly:
33683 sh configure @var{host}
33686 If you run @file{configure} from a directory that contains source
33687 directories for multiple libraries or programs, such as the
33688 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
33690 creates configuration files for every directory level underneath (unless
33691 you tell it not to, with the @samp{--norecursion} option).
33693 You should run the @file{configure} script from the top directory in the
33694 source tree, the @file{gdb-@var{version-number}} directory. If you run
33695 @file{configure} from one of the subdirectories, you will configure only
33696 that subdirectory. That is usually not what you want. In particular,
33697 if you run the first @file{configure} from the @file{gdb} subdirectory
33698 of the @file{gdb-@var{version-number}} directory, you will omit the
33699 configuration of @file{bfd}, @file{readline}, and other sibling
33700 directories of the @file{gdb} subdirectory. This leads to build errors
33701 about missing include files such as @file{bfd/bfd.h}.
33703 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
33704 However, you should make sure that the shell on your path (named by
33705 the @samp{SHELL} environment variable) is publicly readable. Remember
33706 that @value{GDBN} uses the shell to start your program---some systems refuse to
33707 let @value{GDBN} debug child processes whose programs are not readable.
33709 @node Separate Objdir
33710 @section Compiling @value{GDBN} in Another Directory
33712 If you want to run @value{GDBN} versions for several host or target machines,
33713 you need a different @code{gdb} compiled for each combination of
33714 host and target. @file{configure} is designed to make this easy by
33715 allowing you to generate each configuration in a separate subdirectory,
33716 rather than in the source directory. If your @code{make} program
33717 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
33718 @code{make} in each of these directories builds the @code{gdb}
33719 program specified there.
33721 To build @code{gdb} in a separate directory, run @file{configure}
33722 with the @samp{--srcdir} option to specify where to find the source.
33723 (You also need to specify a path to find @file{configure}
33724 itself from your working directory. If the path to @file{configure}
33725 would be the same as the argument to @samp{--srcdir}, you can leave out
33726 the @samp{--srcdir} option; it is assumed.)
33728 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
33729 separate directory for a Sun 4 like this:
33733 cd gdb-@value{GDBVN}
33736 ../gdb-@value{GDBVN}/configure sun4
33741 When @file{configure} builds a configuration using a remote source
33742 directory, it creates a tree for the binaries with the same structure
33743 (and using the same names) as the tree under the source directory. In
33744 the example, you'd find the Sun 4 library @file{libiberty.a} in the
33745 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
33746 @file{gdb-sun4/gdb}.
33748 Make sure that your path to the @file{configure} script has just one
33749 instance of @file{gdb} in it. If your path to @file{configure} looks
33750 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
33751 one subdirectory of @value{GDBN}, not the whole package. This leads to
33752 build errors about missing include files such as @file{bfd/bfd.h}.
33754 One popular reason to build several @value{GDBN} configurations in separate
33755 directories is to configure @value{GDBN} for cross-compiling (where
33756 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
33757 programs that run on another machine---the @dfn{target}).
33758 You specify a cross-debugging target by
33759 giving the @samp{--target=@var{target}} option to @file{configure}.
33761 When you run @code{make} to build a program or library, you must run
33762 it in a configured directory---whatever directory you were in when you
33763 called @file{configure} (or one of its subdirectories).
33765 The @code{Makefile} that @file{configure} generates in each source
33766 directory also runs recursively. If you type @code{make} in a source
33767 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
33768 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
33769 will build all the required libraries, and then build GDB.
33771 When you have multiple hosts or targets configured in separate
33772 directories, you can run @code{make} on them in parallel (for example,
33773 if they are NFS-mounted on each of the hosts); they will not interfere
33777 @section Specifying Names for Hosts and Targets
33779 The specifications used for hosts and targets in the @file{configure}
33780 script are based on a three-part naming scheme, but some short predefined
33781 aliases are also supported. The full naming scheme encodes three pieces
33782 of information in the following pattern:
33785 @var{architecture}-@var{vendor}-@var{os}
33788 For example, you can use the alias @code{sun4} as a @var{host} argument,
33789 or as the value for @var{target} in a @code{--target=@var{target}}
33790 option. The equivalent full name is @samp{sparc-sun-sunos4}.
33792 The @file{configure} script accompanying @value{GDBN} does not provide
33793 any query facility to list all supported host and target names or
33794 aliases. @file{configure} calls the Bourne shell script
33795 @code{config.sub} to map abbreviations to full names; you can read the
33796 script, if you wish, or you can use it to test your guesses on
33797 abbreviations---for example:
33800 % sh config.sub i386-linux
33802 % sh config.sub alpha-linux
33803 alpha-unknown-linux-gnu
33804 % sh config.sub hp9k700
33806 % sh config.sub sun4
33807 sparc-sun-sunos4.1.1
33808 % sh config.sub sun3
33809 m68k-sun-sunos4.1.1
33810 % sh config.sub i986v
33811 Invalid configuration `i986v': machine `i986v' not recognized
33815 @code{config.sub} is also distributed in the @value{GDBN} source
33816 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33818 @node Configure Options
33819 @section @file{configure} Options
33821 Here is a summary of the @file{configure} options and arguments that
33822 are most often useful for building @value{GDBN}. @file{configure} also has
33823 several other options not listed here. @inforef{What Configure
33824 Does,,configure.info}, for a full explanation of @file{configure}.
33827 configure @r{[}--help@r{]}
33828 @r{[}--prefix=@var{dir}@r{]}
33829 @r{[}--exec-prefix=@var{dir}@r{]}
33830 @r{[}--srcdir=@var{dirname}@r{]}
33831 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33832 @r{[}--target=@var{target}@r{]}
33837 You may introduce options with a single @samp{-} rather than
33838 @samp{--} if you prefer; but you may abbreviate option names if you use
33843 Display a quick summary of how to invoke @file{configure}.
33845 @item --prefix=@var{dir}
33846 Configure the source to install programs and files under directory
33849 @item --exec-prefix=@var{dir}
33850 Configure the source to install programs under directory
33853 @c avoid splitting the warning from the explanation:
33855 @item --srcdir=@var{dirname}
33856 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33857 @code{make} that implements the @code{VPATH} feature.}@*
33858 Use this option to make configurations in directories separate from the
33859 @value{GDBN} source directories. Among other things, you can use this to
33860 build (or maintain) several configurations simultaneously, in separate
33861 directories. @file{configure} writes configuration-specific files in
33862 the current directory, but arranges for them to use the source in the
33863 directory @var{dirname}. @file{configure} creates directories under
33864 the working directory in parallel to the source directories below
33867 @item --norecursion
33868 Configure only the directory level where @file{configure} is executed; do not
33869 propagate configuration to subdirectories.
33871 @item --target=@var{target}
33872 Configure @value{GDBN} for cross-debugging programs running on the specified
33873 @var{target}. Without this option, @value{GDBN} is configured to debug
33874 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33876 There is no convenient way to generate a list of all available targets.
33878 @item @var{host} @dots{}
33879 Configure @value{GDBN} to run on the specified @var{host}.
33881 There is no convenient way to generate a list of all available hosts.
33884 There are many other options available as well, but they are generally
33885 needed for special purposes only.
33887 @node System-wide configuration
33888 @section System-wide configuration and settings
33889 @cindex system-wide init file
33891 @value{GDBN} can be configured to have a system-wide init file;
33892 this file will be read and executed at startup (@pxref{Startup, , What
33893 @value{GDBN} does during startup}).
33895 Here is the corresponding configure option:
33898 @item --with-system-gdbinit=@var{file}
33899 Specify that the default location of the system-wide init file is
33903 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33904 it may be subject to relocation. Two possible cases:
33908 If the default location of this init file contains @file{$prefix},
33909 it will be subject to relocation. Suppose that the configure options
33910 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33911 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33912 init file is looked for as @file{$install/etc/gdbinit} instead of
33913 @file{$prefix/etc/gdbinit}.
33916 By contrast, if the default location does not contain the prefix,
33917 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33918 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33919 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33920 wherever @value{GDBN} is installed.
33923 If the configured location of the system-wide init file (as given by the
33924 @option{--with-system-gdbinit} option at configure time) is in the
33925 data-directory (as specified by @option{--with-gdb-datadir} at configure
33926 time) or in one of its subdirectories, then @value{GDBN} will look for the
33927 system-wide init file in the directory specified by the
33928 @option{--data-directory} command-line option.
33929 Note that the system-wide init file is only read once, during @value{GDBN}
33930 initialization. If the data-directory is changed after @value{GDBN} has
33931 started with the @code{set data-directory} command, the file will not be
33935 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
33938 @node System-wide Configuration Scripts
33939 @subsection Installed System-wide Configuration Scripts
33940 @cindex system-wide configuration scripts
33942 The @file{system-gdbinit} directory, located inside the data-directory
33943 (as specified by @option{--with-gdb-datadir} at configure time) contains
33944 a number of scripts which can be used as system-wide init files. To
33945 automatically source those scripts at startup, @value{GDBN} should be
33946 configured with @option{--with-system-gdbinit}. Otherwise, any user
33947 should be able to source them by hand as needed.
33949 The following scripts are currently available:
33952 @item @file{elinos.py}
33954 @cindex ELinOS system-wide configuration script
33955 This script is useful when debugging a program on an ELinOS target.
33956 It takes advantage of the environment variables defined in a standard
33957 ELinOS environment in order to determine the location of the system
33958 shared libraries, and then sets the @samp{solib-absolute-prefix}
33959 and @samp{solib-search-path} variables appropriately.
33961 @item @file{wrs-linux.py}
33962 @pindex wrs-linux.py
33963 @cindex Wind River Linux system-wide configuration script
33964 This script is useful when debugging a program on a target running
33965 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
33966 the host-side sysroot used by the target system.
33970 @node Maintenance Commands
33971 @appendix Maintenance Commands
33972 @cindex maintenance commands
33973 @cindex internal commands
33975 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33976 includes a number of commands intended for @value{GDBN} developers,
33977 that are not documented elsewhere in this manual. These commands are
33978 provided here for reference. (For commands that turn on debugging
33979 messages, see @ref{Debugging Output}.)
33982 @kindex maint agent
33983 @kindex maint agent-eval
33984 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33985 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
33986 Translate the given @var{expression} into remote agent bytecodes.
33987 This command is useful for debugging the Agent Expression mechanism
33988 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33989 expression useful for data collection, such as by tracepoints, while
33990 @samp{maint agent-eval} produces an expression that evaluates directly
33991 to a result. For instance, a collection expression for @code{globa +
33992 globb} will include bytecodes to record four bytes of memory at each
33993 of the addresses of @code{globa} and @code{globb}, while discarding
33994 the result of the addition, while an evaluation expression will do the
33995 addition and return the sum.
33996 If @code{-at} is given, generate remote agent bytecode for @var{location}.
33997 If not, generate remote agent bytecode for current frame PC address.
33999 @kindex maint agent-printf
34000 @item maint agent-printf @var{format},@var{expr},...
34001 Translate the given format string and list of argument expressions
34002 into remote agent bytecodes and display them as a disassembled list.
34003 This command is useful for debugging the agent version of dynamic
34004 printf (@pxref{Dynamic Printf}).
34006 @kindex maint info breakpoints
34007 @item @anchor{maint info breakpoints}maint info breakpoints
34008 Using the same format as @samp{info breakpoints}, display both the
34009 breakpoints you've set explicitly, and those @value{GDBN} is using for
34010 internal purposes. Internal breakpoints are shown with negative
34011 breakpoint numbers. The type column identifies what kind of breakpoint
34016 Normal, explicitly set breakpoint.
34019 Normal, explicitly set watchpoint.
34022 Internal breakpoint, used to handle correctly stepping through
34023 @code{longjmp} calls.
34025 @item longjmp resume
34026 Internal breakpoint at the target of a @code{longjmp}.
34029 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
34032 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
34035 Shared library events.
34039 @kindex maint info btrace
34040 @item maint info btrace
34041 Pint information about raw branch tracing data.
34043 @kindex maint btrace packet-history
34044 @item maint btrace packet-history
34045 Print the raw branch trace packets that are used to compute the
34046 execution history for the @samp{record btrace} command. Both the
34047 information and the format in which it is printed depend on the btrace
34052 For the BTS recording format, print a list of blocks of sequential
34053 code. For each block, the following information is printed:
34057 Newer blocks have higher numbers. The oldest block has number zero.
34058 @item Lowest @samp{PC}
34059 @item Highest @samp{PC}
34063 For the Intel Processor Trace recording format, print a list of
34064 Intel Processor Trace packets. For each packet, the following
34065 information is printed:
34068 @item Packet number
34069 Newer packets have higher numbers. The oldest packet has number zero.
34071 The packet's offset in the trace stream.
34072 @item Packet opcode and payload
34076 @kindex maint btrace clear-packet-history
34077 @item maint btrace clear-packet-history
34078 Discards the cached packet history printed by the @samp{maint btrace
34079 packet-history} command. The history will be computed again when
34082 @kindex maint btrace clear
34083 @item maint btrace clear
34084 Discard the branch trace data. The data will be fetched anew and the
34085 branch trace will be recomputed when needed.
34087 This implicitly truncates the branch trace to a single branch trace
34088 buffer. When updating branch trace incrementally, the branch trace
34089 available to @value{GDBN} may be bigger than a single branch trace
34092 @kindex maint set btrace pt skip-pad
34093 @item maint set btrace pt skip-pad
34094 @kindex maint show btrace pt skip-pad
34095 @item maint show btrace pt skip-pad
34096 Control whether @value{GDBN} will skip PAD packets when computing the
34099 @kindex set displaced-stepping
34100 @kindex show displaced-stepping
34101 @cindex displaced stepping support
34102 @cindex out-of-line single-stepping
34103 @item set displaced-stepping
34104 @itemx show displaced-stepping
34105 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
34106 if the target supports it. Displaced stepping is a way to single-step
34107 over breakpoints without removing them from the inferior, by executing
34108 an out-of-line copy of the instruction that was originally at the
34109 breakpoint location. It is also known as out-of-line single-stepping.
34112 @item set displaced-stepping on
34113 If the target architecture supports it, @value{GDBN} will use
34114 displaced stepping to step over breakpoints.
34116 @item set displaced-stepping off
34117 @value{GDBN} will not use displaced stepping to step over breakpoints,
34118 even if such is supported by the target architecture.
34120 @cindex non-stop mode, and @samp{set displaced-stepping}
34121 @item set displaced-stepping auto
34122 This is the default mode. @value{GDBN} will use displaced stepping
34123 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
34124 architecture supports displaced stepping.
34127 @kindex maint check-psymtabs
34128 @item maint check-psymtabs
34129 Check the consistency of currently expanded psymtabs versus symtabs.
34130 Use this to check, for example, whether a symbol is in one but not the other.
34132 @kindex maint check-symtabs
34133 @item maint check-symtabs
34134 Check the consistency of currently expanded symtabs.
34136 @kindex maint expand-symtabs
34137 @item maint expand-symtabs [@var{regexp}]
34138 Expand symbol tables.
34139 If @var{regexp} is specified, only expand symbol tables for file
34140 names matching @var{regexp}.
34142 @kindex maint set catch-demangler-crashes
34143 @kindex maint show catch-demangler-crashes
34144 @cindex demangler crashes
34145 @item maint set catch-demangler-crashes [on|off]
34146 @itemx maint show catch-demangler-crashes
34147 Control whether @value{GDBN} should attempt to catch crashes in the
34148 symbol name demangler. The default is to attempt to catch crashes.
34149 If enabled, the first time a crash is caught, a core file is created,
34150 the offending symbol is displayed and the user is presented with the
34151 option to terminate the current session.
34153 @kindex maint cplus first_component
34154 @item maint cplus first_component @var{name}
34155 Print the first C@t{++} class/namespace component of @var{name}.
34157 @kindex maint cplus namespace
34158 @item maint cplus namespace
34159 Print the list of possible C@t{++} namespaces.
34161 @kindex maint deprecate
34162 @kindex maint undeprecate
34163 @cindex deprecated commands
34164 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
34165 @itemx maint undeprecate @var{command}
34166 Deprecate or undeprecate the named @var{command}. Deprecated commands
34167 cause @value{GDBN} to issue a warning when you use them. The optional
34168 argument @var{replacement} says which newer command should be used in
34169 favor of the deprecated one; if it is given, @value{GDBN} will mention
34170 the replacement as part of the warning.
34172 @kindex maint dump-me
34173 @item maint dump-me
34174 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
34175 Cause a fatal signal in the debugger and force it to dump its core.
34176 This is supported only on systems which support aborting a program
34177 with the @code{SIGQUIT} signal.
34179 @kindex maint internal-error
34180 @kindex maint internal-warning
34181 @kindex maint demangler-warning
34182 @cindex demangler crashes
34183 @item maint internal-error @r{[}@var{message-text}@r{]}
34184 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
34185 @itemx maint demangler-warning @r{[}@var{message-text}@r{]}
34187 Cause @value{GDBN} to call the internal function @code{internal_error},
34188 @code{internal_warning} or @code{demangler_warning} and hence behave
34189 as though an internal problem has been detected. In addition to
34190 reporting the internal problem, these functions give the user the
34191 opportunity to either quit @value{GDBN} or (for @code{internal_error}
34192 and @code{internal_warning}) create a core file of the current
34193 @value{GDBN} session.
34195 These commands take an optional parameter @var{message-text} that is
34196 used as the text of the error or warning message.
34198 Here's an example of using @code{internal-error}:
34201 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
34202 @dots{}/maint.c:121: internal-error: testing, 1, 2
34203 A problem internal to GDB has been detected. Further
34204 debugging may prove unreliable.
34205 Quit this debugging session? (y or n) @kbd{n}
34206 Create a core file? (y or n) @kbd{n}
34210 @cindex @value{GDBN} internal error
34211 @cindex internal errors, control of @value{GDBN} behavior
34212 @cindex demangler crashes
34214 @kindex maint set internal-error
34215 @kindex maint show internal-error
34216 @kindex maint set internal-warning
34217 @kindex maint show internal-warning
34218 @kindex maint set demangler-warning
34219 @kindex maint show demangler-warning
34220 @item maint set internal-error @var{action} [ask|yes|no]
34221 @itemx maint show internal-error @var{action}
34222 @itemx maint set internal-warning @var{action} [ask|yes|no]
34223 @itemx maint show internal-warning @var{action}
34224 @itemx maint set demangler-warning @var{action} [ask|yes|no]
34225 @itemx maint show demangler-warning @var{action}
34226 When @value{GDBN} reports an internal problem (error or warning) it
34227 gives the user the opportunity to both quit @value{GDBN} and create a
34228 core file of the current @value{GDBN} session. These commands let you
34229 override the default behaviour for each particular @var{action},
34230 described in the table below.
34234 You can specify that @value{GDBN} should always (yes) or never (no)
34235 quit. The default is to ask the user what to do.
34238 You can specify that @value{GDBN} should always (yes) or never (no)
34239 create a core file. The default is to ask the user what to do. Note
34240 that there is no @code{corefile} option for @code{demangler-warning}:
34241 demangler warnings always create a core file and this cannot be
34245 @kindex maint packet
34246 @item maint packet @var{text}
34247 If @value{GDBN} is talking to an inferior via the serial protocol,
34248 then this command sends the string @var{text} to the inferior, and
34249 displays the response packet. @value{GDBN} supplies the initial
34250 @samp{$} character, the terminating @samp{#} character, and the
34253 @kindex maint print architecture
34254 @item maint print architecture @r{[}@var{file}@r{]}
34255 Print the entire architecture configuration. The optional argument
34256 @var{file} names the file where the output goes.
34258 @kindex maint print c-tdesc
34259 @item maint print c-tdesc
34260 Print the current target description (@pxref{Target Descriptions}) as
34261 a C source file. The created source file can be used in @value{GDBN}
34262 when an XML parser is not available to parse the description.
34264 @kindex maint print dummy-frames
34265 @item maint print dummy-frames
34266 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
34269 (@value{GDBP}) @kbd{b add}
34271 (@value{GDBP}) @kbd{print add(2,3)}
34272 Breakpoint 2, add (a=2, b=3) at @dots{}
34274 The program being debugged stopped while in a function called from GDB.
34276 (@value{GDBP}) @kbd{maint print dummy-frames}
34277 0xa8206d8: id=@{stack=0xbfffe734,code=0xbfffe73f,!special@}, ptid=process 9353
34281 Takes an optional file parameter.
34283 @kindex maint print registers
34284 @kindex maint print raw-registers
34285 @kindex maint print cooked-registers
34286 @kindex maint print register-groups
34287 @kindex maint print remote-registers
34288 @item maint print registers @r{[}@var{file}@r{]}
34289 @itemx maint print raw-registers @r{[}@var{file}@r{]}
34290 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
34291 @itemx maint print register-groups @r{[}@var{file}@r{]}
34292 @itemx maint print remote-registers @r{[}@var{file}@r{]}
34293 Print @value{GDBN}'s internal register data structures.
34295 The command @code{maint print raw-registers} includes the contents of
34296 the raw register cache; the command @code{maint print
34297 cooked-registers} includes the (cooked) value of all registers,
34298 including registers which aren't available on the target nor visible
34299 to user; the command @code{maint print register-groups} includes the
34300 groups that each register is a member of; and the command @code{maint
34301 print remote-registers} includes the remote target's register numbers
34302 and offsets in the `G' packets.
34304 These commands take an optional parameter, a file name to which to
34305 write the information.
34307 @kindex maint print reggroups
34308 @item maint print reggroups @r{[}@var{file}@r{]}
34309 Print @value{GDBN}'s internal register group data structures. The
34310 optional argument @var{file} tells to what file to write the
34313 The register groups info looks like this:
34316 (@value{GDBP}) @kbd{maint print reggroups}
34329 This command forces @value{GDBN} to flush its internal register cache.
34331 @kindex maint print objfiles
34332 @cindex info for known object files
34333 @item maint print objfiles @r{[}@var{regexp}@r{]}
34334 Print a dump of all known object files.
34335 If @var{regexp} is specified, only print object files whose names
34336 match @var{regexp}. For each object file, this command prints its name,
34337 address in memory, and all of its psymtabs and symtabs.
34339 @kindex maint print user-registers
34340 @cindex user registers
34341 @item maint print user-registers
34342 List all currently available @dfn{user registers}. User registers
34343 typically provide alternate names for actual hardware registers. They
34344 include the four ``standard'' registers @code{$fp}, @code{$pc},
34345 @code{$sp}, and @code{$ps}. @xref{standard registers}. User
34346 registers can be used in expressions in the same way as the canonical
34347 register names, but only the latter are listed by the @code{info
34348 registers} and @code{maint print registers} commands.
34350 @kindex maint print section-scripts
34351 @cindex info for known .debug_gdb_scripts-loaded scripts
34352 @item maint print section-scripts [@var{regexp}]
34353 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
34354 If @var{regexp} is specified, only print scripts loaded by object files
34355 matching @var{regexp}.
34356 For each script, this command prints its name as specified in the objfile,
34357 and the full path if known.
34358 @xref{dotdebug_gdb_scripts section}.
34360 @kindex maint print statistics
34361 @cindex bcache statistics
34362 @item maint print statistics
34363 This command prints, for each object file in the program, various data
34364 about that object file followed by the byte cache (@dfn{bcache})
34365 statistics for the object file. The objfile data includes the number
34366 of minimal, partial, full, and stabs symbols, the number of types
34367 defined by the objfile, the number of as yet unexpanded psym tables,
34368 the number of line tables and string tables, and the amount of memory
34369 used by the various tables. The bcache statistics include the counts,
34370 sizes, and counts of duplicates of all and unique objects, max,
34371 average, and median entry size, total memory used and its overhead and
34372 savings, and various measures of the hash table size and chain
34375 @kindex maint print target-stack
34376 @cindex target stack description
34377 @item maint print target-stack
34378 A @dfn{target} is an interface between the debugger and a particular
34379 kind of file or process. Targets can be stacked in @dfn{strata},
34380 so that more than one target can potentially respond to a request.
34381 In particular, memory accesses will walk down the stack of targets
34382 until they find a target that is interested in handling that particular
34385 This command prints a short description of each layer that was pushed on
34386 the @dfn{target stack}, starting from the top layer down to the bottom one.
34388 @kindex maint print type
34389 @cindex type chain of a data type
34390 @item maint print type @var{expr}
34391 Print the type chain for a type specified by @var{expr}. The argument
34392 can be either a type name or a symbol. If it is a symbol, the type of
34393 that symbol is described. The type chain produced by this command is
34394 a recursive definition of the data type as stored in @value{GDBN}'s
34395 data structures, including its flags and contained types.
34397 @kindex maint set dwarf always-disassemble
34398 @kindex maint show dwarf always-disassemble
34399 @item maint set dwarf always-disassemble
34400 @item maint show dwarf always-disassemble
34401 Control the behavior of @code{info address} when using DWARF debugging
34404 The default is @code{off}, which means that @value{GDBN} should try to
34405 describe a variable's location in an easily readable format. When
34406 @code{on}, @value{GDBN} will instead display the DWARF location
34407 expression in an assembly-like format. Note that some locations are
34408 too complex for @value{GDBN} to describe simply; in this case you will
34409 always see the disassembly form.
34411 Here is an example of the resulting disassembly:
34414 (gdb) info addr argc
34415 Symbol "argc" is a complex DWARF expression:
34419 For more information on these expressions, see
34420 @uref{http://www.dwarfstd.org/, the DWARF standard}.
34422 @kindex maint set dwarf max-cache-age
34423 @kindex maint show dwarf max-cache-age
34424 @item maint set dwarf max-cache-age
34425 @itemx maint show dwarf max-cache-age
34426 Control the DWARF compilation unit cache.
34428 @cindex DWARF compilation units cache
34429 In object files with inter-compilation-unit references, such as those
34430 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF
34431 reader needs to frequently refer to previously read compilation units.
34432 This setting controls how long a compilation unit will remain in the
34433 cache if it is not referenced. A higher limit means that cached
34434 compilation units will be stored in memory longer, and more total
34435 memory will be used. Setting it to zero disables caching, which will
34436 slow down @value{GDBN} startup, but reduce memory consumption.
34438 @kindex maint set profile
34439 @kindex maint show profile
34440 @cindex profiling GDB
34441 @item maint set profile
34442 @itemx maint show profile
34443 Control profiling of @value{GDBN}.
34445 Profiling will be disabled until you use the @samp{maint set profile}
34446 command to enable it. When you enable profiling, the system will begin
34447 collecting timing and execution count data; when you disable profiling or
34448 exit @value{GDBN}, the results will be written to a log file. Remember that
34449 if you use profiling, @value{GDBN} will overwrite the profiling log file
34450 (often called @file{gmon.out}). If you have a record of important profiling
34451 data in a @file{gmon.out} file, be sure to move it to a safe location.
34453 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
34454 compiled with the @samp{-pg} compiler option.
34456 @kindex maint set show-debug-regs
34457 @kindex maint show show-debug-regs
34458 @cindex hardware debug registers
34459 @item maint set show-debug-regs
34460 @itemx maint show show-debug-regs
34461 Control whether to show variables that mirror the hardware debug
34462 registers. Use @code{on} to enable, @code{off} to disable. If
34463 enabled, the debug registers values are shown when @value{GDBN} inserts or
34464 removes a hardware breakpoint or watchpoint, and when the inferior
34465 triggers a hardware-assisted breakpoint or watchpoint.
34467 @kindex maint set show-all-tib
34468 @kindex maint show show-all-tib
34469 @item maint set show-all-tib
34470 @itemx maint show show-all-tib
34471 Control whether to show all non zero areas within a 1k block starting
34472 at thread local base, when using the @samp{info w32 thread-information-block}
34475 @kindex maint set target-async
34476 @kindex maint show target-async
34477 @item maint set target-async
34478 @itemx maint show target-async
34479 This controls whether @value{GDBN} targets operate in synchronous or
34480 asynchronous mode (@pxref{Background Execution}). Normally the
34481 default is asynchronous, if it is available; but this can be changed
34482 to more easily debug problems occurring only in synchronous mode.
34484 @kindex maint set target-non-stop @var{mode} [on|off|auto]
34485 @kindex maint show target-non-stop
34486 @item maint set target-non-stop
34487 @itemx maint show target-non-stop
34489 This controls whether @value{GDBN} targets always operate in non-stop
34490 mode even if @code{set non-stop} is @code{off} (@pxref{Non-Stop
34491 Mode}). The default is @code{auto}, meaning non-stop mode is enabled
34492 if supported by the target.
34495 @item maint set target-non-stop auto
34496 This is the default mode. @value{GDBN} controls the target in
34497 non-stop mode if the target supports it.
34499 @item maint set target-non-stop on
34500 @value{GDBN} controls the target in non-stop mode even if the target
34501 does not indicate support.
34503 @item maint set target-non-stop off
34504 @value{GDBN} does not control the target in non-stop mode even if the
34505 target supports it.
34508 @kindex maint set per-command
34509 @kindex maint show per-command
34510 @item maint set per-command
34511 @itemx maint show per-command
34512 @cindex resources used by commands
34514 @value{GDBN} can display the resources used by each command.
34515 This is useful in debugging performance problems.
34518 @item maint set per-command space [on|off]
34519 @itemx maint show per-command space
34520 Enable or disable the printing of the memory used by GDB for each command.
34521 If enabled, @value{GDBN} will display how much memory each command
34522 took, following the command's own output.
34523 This can also be requested by invoking @value{GDBN} with the
34524 @option{--statistics} command-line switch (@pxref{Mode Options}).
34526 @item maint set per-command time [on|off]
34527 @itemx maint show per-command time
34528 Enable or disable the printing of the execution time of @value{GDBN}
34530 If enabled, @value{GDBN} will display how much time it
34531 took to execute each command, following the command's own output.
34532 Both CPU time and wallclock time are printed.
34533 Printing both is useful when trying to determine whether the cost is
34534 CPU or, e.g., disk/network latency.
34535 Note that the CPU time printed is for @value{GDBN} only, it does not include
34536 the execution time of the inferior because there's no mechanism currently
34537 to compute how much time was spent by @value{GDBN} and how much time was
34538 spent by the program been debugged.
34539 This can also be requested by invoking @value{GDBN} with the
34540 @option{--statistics} command-line switch (@pxref{Mode Options}).
34542 @item maint set per-command symtab [on|off]
34543 @itemx maint show per-command symtab
34544 Enable or disable the printing of basic symbol table statistics
34546 If enabled, @value{GDBN} will display the following information:
34550 number of symbol tables
34552 number of primary symbol tables
34554 number of blocks in the blockvector
34558 @kindex maint space
34559 @cindex memory used by commands
34560 @item maint space @var{value}
34561 An alias for @code{maint set per-command space}.
34562 A non-zero value enables it, zero disables it.
34565 @cindex time of command execution
34566 @item maint time @var{value}
34567 An alias for @code{maint set per-command time}.
34568 A non-zero value enables it, zero disables it.
34570 @kindex maint translate-address
34571 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
34572 Find the symbol stored at the location specified by the address
34573 @var{addr} and an optional section name @var{section}. If found,
34574 @value{GDBN} prints the name of the closest symbol and an offset from
34575 the symbol's location to the specified address. This is similar to
34576 the @code{info address} command (@pxref{Symbols}), except that this
34577 command also allows to find symbols in other sections.
34579 If section was not specified, the section in which the symbol was found
34580 is also printed. For dynamically linked executables, the name of
34581 executable or shared library containing the symbol is printed as well.
34585 The following command is useful for non-interactive invocations of
34586 @value{GDBN}, such as in the test suite.
34589 @item set watchdog @var{nsec}
34590 @kindex set watchdog
34591 @cindex watchdog timer
34592 @cindex timeout for commands
34593 Set the maximum number of seconds @value{GDBN} will wait for the
34594 target operation to finish. If this time expires, @value{GDBN}
34595 reports and error and the command is aborted.
34597 @item show watchdog
34598 Show the current setting of the target wait timeout.
34601 @node Remote Protocol
34602 @appendix @value{GDBN} Remote Serial Protocol
34607 * Stop Reply Packets::
34608 * General Query Packets::
34609 * Architecture-Specific Protocol Details::
34610 * Tracepoint Packets::
34611 * Host I/O Packets::
34613 * Notification Packets::
34614 * Remote Non-Stop::
34615 * Packet Acknowledgment::
34617 * File-I/O Remote Protocol Extension::
34618 * Library List Format::
34619 * Library List Format for SVR4 Targets::
34620 * Memory Map Format::
34621 * Thread List Format::
34622 * Traceframe Info Format::
34623 * Branch Trace Format::
34624 * Branch Trace Configuration Format::
34630 There may be occasions when you need to know something about the
34631 protocol---for example, if there is only one serial port to your target
34632 machine, you might want your program to do something special if it
34633 recognizes a packet meant for @value{GDBN}.
34635 In the examples below, @samp{->} and @samp{<-} are used to indicate
34636 transmitted and received data, respectively.
34638 @cindex protocol, @value{GDBN} remote serial
34639 @cindex serial protocol, @value{GDBN} remote
34640 @cindex remote serial protocol
34641 All @value{GDBN} commands and responses (other than acknowledgments
34642 and notifications, see @ref{Notification Packets}) are sent as a
34643 @var{packet}. A @var{packet} is introduced with the character
34644 @samp{$}, the actual @var{packet-data}, and the terminating character
34645 @samp{#} followed by a two-digit @var{checksum}:
34648 @code{$}@var{packet-data}@code{#}@var{checksum}
34652 @cindex checksum, for @value{GDBN} remote
34654 The two-digit @var{checksum} is computed as the modulo 256 sum of all
34655 characters between the leading @samp{$} and the trailing @samp{#} (an
34656 eight bit unsigned checksum).
34658 Implementors should note that prior to @value{GDBN} 5.0 the protocol
34659 specification also included an optional two-digit @var{sequence-id}:
34662 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
34665 @cindex sequence-id, for @value{GDBN} remote
34667 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
34668 has never output @var{sequence-id}s. Stubs that handle packets added
34669 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
34671 When either the host or the target machine receives a packet, the first
34672 response expected is an acknowledgment: either @samp{+} (to indicate
34673 the package was received correctly) or @samp{-} (to request
34677 -> @code{$}@var{packet-data}@code{#}@var{checksum}
34682 The @samp{+}/@samp{-} acknowledgments can be disabled
34683 once a connection is established.
34684 @xref{Packet Acknowledgment}, for details.
34686 The host (@value{GDBN}) sends @var{command}s, and the target (the
34687 debugging stub incorporated in your program) sends a @var{response}. In
34688 the case of step and continue @var{command}s, the response is only sent
34689 when the operation has completed, and the target has again stopped all
34690 threads in all attached processes. This is the default all-stop mode
34691 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
34692 execution mode; see @ref{Remote Non-Stop}, for details.
34694 @var{packet-data} consists of a sequence of characters with the
34695 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
34698 @cindex remote protocol, field separator
34699 Fields within the packet should be separated using @samp{,} @samp{;} or
34700 @samp{:}. Except where otherwise noted all numbers are represented in
34701 @sc{hex} with leading zeros suppressed.
34703 Implementors should note that prior to @value{GDBN} 5.0, the character
34704 @samp{:} could not appear as the third character in a packet (as it
34705 would potentially conflict with the @var{sequence-id}).
34707 @cindex remote protocol, binary data
34708 @anchor{Binary Data}
34709 Binary data in most packets is encoded either as two hexadecimal
34710 digits per byte of binary data. This allowed the traditional remote
34711 protocol to work over connections which were only seven-bit clean.
34712 Some packets designed more recently assume an eight-bit clean
34713 connection, and use a more efficient encoding to send and receive
34716 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
34717 as an escape character. Any escaped byte is transmitted as the escape
34718 character followed by the original character XORed with @code{0x20}.
34719 For example, the byte @code{0x7d} would be transmitted as the two
34720 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
34721 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
34722 @samp{@}}) must always be escaped. Responses sent by the stub
34723 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
34724 is not interpreted as the start of a run-length encoded sequence
34727 Response @var{data} can be run-length encoded to save space.
34728 Run-length encoding replaces runs of identical characters with one
34729 instance of the repeated character, followed by a @samp{*} and a
34730 repeat count. The repeat count is itself sent encoded, to avoid
34731 binary characters in @var{data}: a value of @var{n} is sent as
34732 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
34733 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
34734 code 32) for a repeat count of 3. (This is because run-length
34735 encoding starts to win for counts 3 or more.) Thus, for example,
34736 @samp{0* } is a run-length encoding of ``0000'': the space character
34737 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
34740 The printable characters @samp{#} and @samp{$} or with a numeric value
34741 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
34742 seven repeats (@samp{$}) can be expanded using a repeat count of only
34743 five (@samp{"}). For example, @samp{00000000} can be encoded as
34746 The error response returned for some packets includes a two character
34747 error number. That number is not well defined.
34749 @cindex empty response, for unsupported packets
34750 For any @var{command} not supported by the stub, an empty response
34751 (@samp{$#00}) should be returned. That way it is possible to extend the
34752 protocol. A newer @value{GDBN} can tell if a packet is supported based
34755 At a minimum, a stub is required to support the @samp{g} and @samp{G}
34756 commands for register access, and the @samp{m} and @samp{M} commands
34757 for memory access. Stubs that only control single-threaded targets
34758 can implement run control with the @samp{c} (continue), and @samp{s}
34759 (step) commands. Stubs that support multi-threading targets should
34760 support the @samp{vCont} command. All other commands are optional.
34765 The following table provides a complete list of all currently defined
34766 @var{command}s and their corresponding response @var{data}.
34767 @xref{File-I/O Remote Protocol Extension}, for details about the File
34768 I/O extension of the remote protocol.
34770 Each packet's description has a template showing the packet's overall
34771 syntax, followed by an explanation of the packet's meaning. We
34772 include spaces in some of the templates for clarity; these are not
34773 part of the packet's syntax. No @value{GDBN} packet uses spaces to
34774 separate its components. For example, a template like @samp{foo
34775 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
34776 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
34777 @var{baz}. @value{GDBN} does not transmit a space character between the
34778 @samp{foo} and the @var{bar}, or between the @var{bar} and the
34781 @cindex @var{thread-id}, in remote protocol
34782 @anchor{thread-id syntax}
34783 Several packets and replies include a @var{thread-id} field to identify
34784 a thread. Normally these are positive numbers with a target-specific
34785 interpretation, formatted as big-endian hex strings. A @var{thread-id}
34786 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
34789 In addition, the remote protocol supports a multiprocess feature in
34790 which the @var{thread-id} syntax is extended to optionally include both
34791 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
34792 The @var{pid} (process) and @var{tid} (thread) components each have the
34793 format described above: a positive number with target-specific
34794 interpretation formatted as a big-endian hex string, literal @samp{-1}
34795 to indicate all processes or threads (respectively), or @samp{0} to
34796 indicate an arbitrary process or thread. Specifying just a process, as
34797 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
34798 error to specify all processes but a specific thread, such as
34799 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
34800 for those packets and replies explicitly documented to include a process
34801 ID, rather than a @var{thread-id}.
34803 The multiprocess @var{thread-id} syntax extensions are only used if both
34804 @value{GDBN} and the stub report support for the @samp{multiprocess}
34805 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
34808 Note that all packet forms beginning with an upper- or lower-case
34809 letter, other than those described here, are reserved for future use.
34811 Here are the packet descriptions.
34816 @cindex @samp{!} packet
34817 @anchor{extended mode}
34818 Enable extended mode. In extended mode, the remote server is made
34819 persistent. The @samp{R} packet is used to restart the program being
34825 The remote target both supports and has enabled extended mode.
34829 @cindex @samp{?} packet
34831 Indicate the reason the target halted. The reply is the same as for
34832 step and continue. This packet has a special interpretation when the
34833 target is in non-stop mode; see @ref{Remote Non-Stop}.
34836 @xref{Stop Reply Packets}, for the reply specifications.
34838 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
34839 @cindex @samp{A} packet
34840 Initialized @code{argv[]} array passed into program. @var{arglen}
34841 specifies the number of bytes in the hex encoded byte stream
34842 @var{arg}. See @code{gdbserver} for more details.
34847 The arguments were set.
34853 @cindex @samp{b} packet
34854 (Don't use this packet; its behavior is not well-defined.)
34855 Change the serial line speed to @var{baud}.
34857 JTC: @emph{When does the transport layer state change? When it's
34858 received, or after the ACK is transmitted. In either case, there are
34859 problems if the command or the acknowledgment packet is dropped.}
34861 Stan: @emph{If people really wanted to add something like this, and get
34862 it working for the first time, they ought to modify ser-unix.c to send
34863 some kind of out-of-band message to a specially-setup stub and have the
34864 switch happen "in between" packets, so that from remote protocol's point
34865 of view, nothing actually happened.}
34867 @item B @var{addr},@var{mode}
34868 @cindex @samp{B} packet
34869 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
34870 breakpoint at @var{addr}.
34872 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
34873 (@pxref{insert breakpoint or watchpoint packet}).
34875 @cindex @samp{bc} packet
34878 Backward continue. Execute the target system in reverse. No parameter.
34879 @xref{Reverse Execution}, for more information.
34882 @xref{Stop Reply Packets}, for the reply specifications.
34884 @cindex @samp{bs} packet
34887 Backward single step. Execute one instruction in reverse. No parameter.
34888 @xref{Reverse Execution}, for more information.
34891 @xref{Stop Reply Packets}, for the reply specifications.
34893 @item c @r{[}@var{addr}@r{]}
34894 @cindex @samp{c} packet
34895 Continue at @var{addr}, which is the address to resume. If @var{addr}
34896 is omitted, resume at current address.
34898 This packet is deprecated for multi-threading support. @xref{vCont
34902 @xref{Stop Reply Packets}, for the reply specifications.
34904 @item C @var{sig}@r{[};@var{addr}@r{]}
34905 @cindex @samp{C} packet
34906 Continue with signal @var{sig} (hex signal number). If
34907 @samp{;@var{addr}} is omitted, resume at same address.
34909 This packet is deprecated for multi-threading support. @xref{vCont
34913 @xref{Stop Reply Packets}, for the reply specifications.
34916 @cindex @samp{d} packet
34919 Don't use this packet; instead, define a general set packet
34920 (@pxref{General Query Packets}).
34924 @cindex @samp{D} packet
34925 The first form of the packet is used to detach @value{GDBN} from the
34926 remote system. It is sent to the remote target
34927 before @value{GDBN} disconnects via the @code{detach} command.
34929 The second form, including a process ID, is used when multiprocess
34930 protocol extensions are enabled (@pxref{multiprocess extensions}), to
34931 detach only a specific process. The @var{pid} is specified as a
34932 big-endian hex string.
34942 @item F @var{RC},@var{EE},@var{CF};@var{XX}
34943 @cindex @samp{F} packet
34944 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
34945 This is part of the File-I/O protocol extension. @xref{File-I/O
34946 Remote Protocol Extension}, for the specification.
34949 @anchor{read registers packet}
34950 @cindex @samp{g} packet
34951 Read general registers.
34955 @item @var{XX@dots{}}
34956 Each byte of register data is described by two hex digits. The bytes
34957 with the register are transmitted in target byte order. The size of
34958 each register and their position within the @samp{g} packet are
34959 determined by the @value{GDBN} internal gdbarch functions
34960 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
34961 specification of several standard @samp{g} packets is specified below.
34963 When reading registers from a trace frame (@pxref{Analyze Collected
34964 Data,,Using the Collected Data}), the stub may also return a string of
34965 literal @samp{x}'s in place of the register data digits, to indicate
34966 that the corresponding register has not been collected, thus its value
34967 is unavailable. For example, for an architecture with 4 registers of
34968 4 bytes each, the following reply indicates to @value{GDBN} that
34969 registers 0 and 2 have not been collected, while registers 1 and 3
34970 have been collected, and both have zero value:
34974 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
34981 @item G @var{XX@dots{}}
34982 @cindex @samp{G} packet
34983 Write general registers. @xref{read registers packet}, for a
34984 description of the @var{XX@dots{}} data.
34994 @item H @var{op} @var{thread-id}
34995 @cindex @samp{H} packet
34996 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
34997 @samp{G}, et.al.). Depending on the operation to be performed, @var{op}
34998 should be @samp{c} for step and continue operations (note that this
34999 is deprecated, supporting the @samp{vCont} command is a better
35000 option), and @samp{g} for other operations. The thread designator
35001 @var{thread-id} has the format and interpretation described in
35002 @ref{thread-id syntax}.
35013 @c 'H': How restrictive (or permissive) is the thread model. If a
35014 @c thread is selected and stopped, are other threads allowed
35015 @c to continue to execute? As I mentioned above, I think the
35016 @c semantics of each command when a thread is selected must be
35017 @c described. For example:
35019 @c 'g': If the stub supports threads and a specific thread is
35020 @c selected, returns the register block from that thread;
35021 @c otherwise returns current registers.
35023 @c 'G' If the stub supports threads and a specific thread is
35024 @c selected, sets the registers of the register block of
35025 @c that thread; otherwise sets current registers.
35027 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
35028 @anchor{cycle step packet}
35029 @cindex @samp{i} packet
35030 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
35031 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
35032 step starting at that address.
35035 @cindex @samp{I} packet
35036 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
35040 @cindex @samp{k} packet
35043 The exact effect of this packet is not specified.
35045 For a bare-metal target, it may power cycle or reset the target
35046 system. For that reason, the @samp{k} packet has no reply.
35048 For a single-process target, it may kill that process if possible.
35050 A multiple-process target may choose to kill just one process, or all
35051 that are under @value{GDBN}'s control. For more precise control, use
35052 the vKill packet (@pxref{vKill packet}).
35054 If the target system immediately closes the connection in response to
35055 @samp{k}, @value{GDBN} does not consider the lack of packet
35056 acknowledgment to be an error, and assumes the kill was successful.
35058 If connected using @kbd{target extended-remote}, and the target does
35059 not close the connection in response to a kill request, @value{GDBN}
35060 probes the target state as if a new connection was opened
35061 (@pxref{? packet}).
35063 @item m @var{addr},@var{length}
35064 @cindex @samp{m} packet
35065 Read @var{length} addressable memory units starting at address @var{addr}
35066 (@pxref{addressable memory unit}). Note that @var{addr} may not be aligned to
35067 any particular boundary.
35069 The stub need not use any particular size or alignment when gathering
35070 data from memory for the response; even if @var{addr} is word-aligned
35071 and @var{length} is a multiple of the word size, the stub is free to
35072 use byte accesses, or not. For this reason, this packet may not be
35073 suitable for accessing memory-mapped I/O devices.
35074 @cindex alignment of remote memory accesses
35075 @cindex size of remote memory accesses
35076 @cindex memory, alignment and size of remote accesses
35080 @item @var{XX@dots{}}
35081 Memory contents; each byte is transmitted as a two-digit hexadecimal number.
35082 The reply may contain fewer addressable memory units than requested if the
35083 server was able to read only part of the region of memory.
35088 @item M @var{addr},@var{length}:@var{XX@dots{}}
35089 @cindex @samp{M} packet
35090 Write @var{length} addressable memory units starting at address @var{addr}
35091 (@pxref{addressable memory unit}). The data is given by @var{XX@dots{}}; each
35092 byte is transmitted as a two-digit hexadecimal number.
35099 for an error (this includes the case where only part of the data was
35104 @cindex @samp{p} packet
35105 Read the value of register @var{n}; @var{n} is in hex.
35106 @xref{read registers packet}, for a description of how the returned
35107 register value is encoded.
35111 @item @var{XX@dots{}}
35112 the register's value
35116 Indicating an unrecognized @var{query}.
35119 @item P @var{n@dots{}}=@var{r@dots{}}
35120 @anchor{write register packet}
35121 @cindex @samp{P} packet
35122 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
35123 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
35124 digits for each byte in the register (target byte order).
35134 @item q @var{name} @var{params}@dots{}
35135 @itemx Q @var{name} @var{params}@dots{}
35136 @cindex @samp{q} packet
35137 @cindex @samp{Q} packet
35138 General query (@samp{q}) and set (@samp{Q}). These packets are
35139 described fully in @ref{General Query Packets}.
35142 @cindex @samp{r} packet
35143 Reset the entire system.
35145 Don't use this packet; use the @samp{R} packet instead.
35148 @cindex @samp{R} packet
35149 Restart the program being debugged. The @var{XX}, while needed, is ignored.
35150 This packet is only available in extended mode (@pxref{extended mode}).
35152 The @samp{R} packet has no reply.
35154 @item s @r{[}@var{addr}@r{]}
35155 @cindex @samp{s} packet
35156 Single step, resuming at @var{addr}. If
35157 @var{addr} is omitted, resume at same address.
35159 This packet is deprecated for multi-threading support. @xref{vCont
35163 @xref{Stop Reply Packets}, for the reply specifications.
35165 @item S @var{sig}@r{[};@var{addr}@r{]}
35166 @anchor{step with signal packet}
35167 @cindex @samp{S} packet
35168 Step with signal. This is analogous to the @samp{C} packet, but
35169 requests a single-step, rather than a normal resumption of execution.
35171 This packet is deprecated for multi-threading support. @xref{vCont
35175 @xref{Stop Reply Packets}, for the reply specifications.
35177 @item t @var{addr}:@var{PP},@var{MM}
35178 @cindex @samp{t} packet
35179 Search backwards starting at address @var{addr} for a match with pattern
35180 @var{PP} and mask @var{MM}, both of which are are 4 byte long.
35181 There must be at least 3 digits in @var{addr}.
35183 @item T @var{thread-id}
35184 @cindex @samp{T} packet
35185 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
35190 thread is still alive
35196 Packets starting with @samp{v} are identified by a multi-letter name,
35197 up to the first @samp{;} or @samp{?} (or the end of the packet).
35199 @item vAttach;@var{pid}
35200 @cindex @samp{vAttach} packet
35201 Attach to a new process with the specified process ID @var{pid}.
35202 The process ID is a
35203 hexadecimal integer identifying the process. In all-stop mode, all
35204 threads in the attached process are stopped; in non-stop mode, it may be
35205 attached without being stopped if that is supported by the target.
35207 @c In non-stop mode, on a successful vAttach, the stub should set the
35208 @c current thread to a thread of the newly-attached process. After
35209 @c attaching, GDB queries for the attached process's thread ID with qC.
35210 @c Also note that, from a user perspective, whether or not the
35211 @c target is stopped on attach in non-stop mode depends on whether you
35212 @c use the foreground or background version of the attach command, not
35213 @c on what vAttach does; GDB does the right thing with respect to either
35214 @c stopping or restarting threads.
35216 This packet is only available in extended mode (@pxref{extended mode}).
35222 @item @r{Any stop packet}
35223 for success in all-stop mode (@pxref{Stop Reply Packets})
35225 for success in non-stop mode (@pxref{Remote Non-Stop})
35228 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
35229 @cindex @samp{vCont} packet
35230 @anchor{vCont packet}
35231 Resume the inferior, specifying different actions for each thread.
35232 If an action is specified with no @var{thread-id}, then it is applied to any
35233 threads that don't have a specific action specified; if no default action is
35234 specified then other threads should remain stopped in all-stop mode and
35235 in their current state in non-stop mode.
35236 Specifying multiple
35237 default actions is an error; specifying no actions is also an error.
35238 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
35240 Currently supported actions are:
35246 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
35250 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
35253 @item r @var{start},@var{end}
35254 Step once, and then keep stepping as long as the thread stops at
35255 addresses between @var{start} (inclusive) and @var{end} (exclusive).
35256 The remote stub reports a stop reply when either the thread goes out
35257 of the range or is stopped due to an unrelated reason, such as hitting
35258 a breakpoint. @xref{range stepping}.
35260 If the range is empty (@var{start} == @var{end}), then the action
35261 becomes equivalent to the @samp{s} action. In other words,
35262 single-step once, and report the stop (even if the stepped instruction
35263 jumps to @var{start}).
35265 (A stop reply may be sent at any point even if the PC is still within
35266 the stepping range; for example, it is valid to implement this packet
35267 in a degenerate way as a single instruction step operation.)
35271 The optional argument @var{addr} normally associated with the
35272 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
35273 not supported in @samp{vCont}.
35275 The @samp{t} action is only relevant in non-stop mode
35276 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
35277 A stop reply should be generated for any affected thread not already stopped.
35278 When a thread is stopped by means of a @samp{t} action,
35279 the corresponding stop reply should indicate that the thread has stopped with
35280 signal @samp{0}, regardless of whether the target uses some other signal
35281 as an implementation detail.
35283 The stub must support @samp{vCont} if it reports support for
35284 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
35285 this case @samp{vCont} actions can be specified to apply to all threads
35286 in a process by using the @samp{p@var{pid}.-1} form of the
35290 @xref{Stop Reply Packets}, for the reply specifications.
35293 @cindex @samp{vCont?} packet
35294 Request a list of actions supported by the @samp{vCont} packet.
35298 @item vCont@r{[};@var{action}@dots{}@r{]}
35299 The @samp{vCont} packet is supported. Each @var{action} is a supported
35300 command in the @samp{vCont} packet.
35302 The @samp{vCont} packet is not supported.
35305 @anchor{vCtrlC packet}
35307 @cindex @samp{vCtrlC} packet
35308 Interrupt remote target as if a control-C was pressed on the remote
35309 terminal. This is the equivalent to reacting to the @code{^C}
35310 (@samp{\003}, the control-C character) character in all-stop mode
35311 while the target is running, except this works in non-stop mode.
35312 @xref{interrupting remote targets}, for more info on the all-stop
35323 @item vFile:@var{operation}:@var{parameter}@dots{}
35324 @cindex @samp{vFile} packet
35325 Perform a file operation on the target system. For details,
35326 see @ref{Host I/O Packets}.
35328 @item vFlashErase:@var{addr},@var{length}
35329 @cindex @samp{vFlashErase} packet
35330 Direct the stub to erase @var{length} bytes of flash starting at
35331 @var{addr}. The region may enclose any number of flash blocks, but
35332 its start and end must fall on block boundaries, as indicated by the
35333 flash block size appearing in the memory map (@pxref{Memory Map
35334 Format}). @value{GDBN} groups flash memory programming operations
35335 together, and sends a @samp{vFlashDone} request after each group; the
35336 stub is allowed to delay erase operation until the @samp{vFlashDone}
35337 packet is received.
35347 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
35348 @cindex @samp{vFlashWrite} packet
35349 Direct the stub to write data to flash address @var{addr}. The data
35350 is passed in binary form using the same encoding as for the @samp{X}
35351 packet (@pxref{Binary Data}). The memory ranges specified by
35352 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
35353 not overlap, and must appear in order of increasing addresses
35354 (although @samp{vFlashErase} packets for higher addresses may already
35355 have been received; the ordering is guaranteed only between
35356 @samp{vFlashWrite} packets). If a packet writes to an address that was
35357 neither erased by a preceding @samp{vFlashErase} packet nor by some other
35358 target-specific method, the results are unpredictable.
35366 for vFlashWrite addressing non-flash memory
35372 @cindex @samp{vFlashDone} packet
35373 Indicate to the stub that flash programming operation is finished.
35374 The stub is permitted to delay or batch the effects of a group of
35375 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
35376 @samp{vFlashDone} packet is received. The contents of the affected
35377 regions of flash memory are unpredictable until the @samp{vFlashDone}
35378 request is completed.
35380 @item vKill;@var{pid}
35381 @cindex @samp{vKill} packet
35382 @anchor{vKill packet}
35383 Kill the process with the specified process ID @var{pid}, which is a
35384 hexadecimal integer identifying the process. This packet is used in
35385 preference to @samp{k} when multiprocess protocol extensions are
35386 supported; see @ref{multiprocess extensions}.
35396 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
35397 @cindex @samp{vRun} packet
35398 Run the program @var{filename}, passing it each @var{argument} on its
35399 command line. The file and arguments are hex-encoded strings. If
35400 @var{filename} is an empty string, the stub may use a default program
35401 (e.g.@: the last program run). The program is created in the stopped
35404 @c FIXME: What about non-stop mode?
35406 This packet is only available in extended mode (@pxref{extended mode}).
35412 @item @r{Any stop packet}
35413 for success (@pxref{Stop Reply Packets})
35417 @cindex @samp{vStopped} packet
35418 @xref{Notification Packets}.
35420 @item X @var{addr},@var{length}:@var{XX@dots{}}
35422 @cindex @samp{X} packet
35423 Write data to memory, where the data is transmitted in binary.
35424 Memory is specified by its address @var{addr} and number of addressable memory
35425 units @var{length} (@pxref{addressable memory unit});
35426 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
35436 @item z @var{type},@var{addr},@var{kind}
35437 @itemx Z @var{type},@var{addr},@var{kind}
35438 @anchor{insert breakpoint or watchpoint packet}
35439 @cindex @samp{z} packet
35440 @cindex @samp{Z} packets
35441 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
35442 watchpoint starting at address @var{address} of kind @var{kind}.
35444 Each breakpoint and watchpoint packet @var{type} is documented
35447 @emph{Implementation notes: A remote target shall return an empty string
35448 for an unrecognized breakpoint or watchpoint packet @var{type}. A
35449 remote target shall support either both or neither of a given
35450 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
35451 avoid potential problems with duplicate packets, the operations should
35452 be implemented in an idempotent way.}
35454 @item z0,@var{addr},@var{kind}
35455 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
35456 @cindex @samp{z0} packet
35457 @cindex @samp{Z0} packet
35458 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
35459 @var{addr} of type @var{kind}.
35461 A memory breakpoint is implemented by replacing the instruction at
35462 @var{addr} with a software breakpoint or trap instruction. The
35463 @var{kind} is target-specific and typically indicates the size of
35464 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
35465 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
35466 architectures have additional meanings for @var{kind};
35467 @var{cond_list} is an optional list of conditional expressions in bytecode
35468 form that should be evaluated on the target's side. These are the
35469 conditions that should be taken into consideration when deciding if
35470 the breakpoint trigger should be reported back to @var{GDBN}.
35472 See also the @samp{swbreak} stop reason (@pxref{swbreak stop reason})
35473 for how to best report a memory breakpoint event to @value{GDBN}.
35475 The @var{cond_list} parameter is comprised of a series of expressions,
35476 concatenated without separators. Each expression has the following form:
35480 @item X @var{len},@var{expr}
35481 @var{len} is the length of the bytecode expression and @var{expr} is the
35482 actual conditional expression in bytecode form.
35486 The optional @var{cmd_list} parameter introduces commands that may be
35487 run on the target, rather than being reported back to @value{GDBN}.
35488 The parameter starts with a numeric flag @var{persist}; if the flag is
35489 nonzero, then the breakpoint may remain active and the commands
35490 continue to be run even when @value{GDBN} disconnects from the target.
35491 Following this flag is a series of expressions concatenated with no
35492 separators. Each expression has the following form:
35496 @item X @var{len},@var{expr}
35497 @var{len} is the length of the bytecode expression and @var{expr} is the
35498 actual conditional expression in bytecode form.
35502 see @ref{Architecture-Specific Protocol Details}.
35504 @emph{Implementation note: It is possible for a target to copy or move
35505 code that contains memory breakpoints (e.g., when implementing
35506 overlays). The behavior of this packet, in the presence of such a
35507 target, is not defined.}
35519 @item z1,@var{addr},@var{kind}
35520 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
35521 @cindex @samp{z1} packet
35522 @cindex @samp{Z1} packet
35523 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
35524 address @var{addr}.
35526 A hardware breakpoint is implemented using a mechanism that is not
35527 dependant on being able to modify the target's memory. The @var{kind}
35528 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
35530 @emph{Implementation note: A hardware breakpoint is not affected by code
35543 @item z2,@var{addr},@var{kind}
35544 @itemx Z2,@var{addr},@var{kind}
35545 @cindex @samp{z2} packet
35546 @cindex @samp{Z2} packet
35547 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
35548 The number of bytes to watch is specified by @var{kind}.
35560 @item z3,@var{addr},@var{kind}
35561 @itemx Z3,@var{addr},@var{kind}
35562 @cindex @samp{z3} packet
35563 @cindex @samp{Z3} packet
35564 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
35565 The number of bytes to watch is specified by @var{kind}.
35577 @item z4,@var{addr},@var{kind}
35578 @itemx Z4,@var{addr},@var{kind}
35579 @cindex @samp{z4} packet
35580 @cindex @samp{Z4} packet
35581 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
35582 The number of bytes to watch is specified by @var{kind}.
35596 @node Stop Reply Packets
35597 @section Stop Reply Packets
35598 @cindex stop reply packets
35600 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
35601 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
35602 receive any of the below as a reply. Except for @samp{?}
35603 and @samp{vStopped}, that reply is only returned
35604 when the target halts. In the below the exact meaning of @dfn{signal
35605 number} is defined by the header @file{include/gdb/signals.h} in the
35606 @value{GDBN} source code.
35608 As in the description of request packets, we include spaces in the
35609 reply templates for clarity; these are not part of the reply packet's
35610 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
35616 The program received signal number @var{AA} (a two-digit hexadecimal
35617 number). This is equivalent to a @samp{T} response with no
35618 @var{n}:@var{r} pairs.
35620 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
35621 @cindex @samp{T} packet reply
35622 The program received signal number @var{AA} (a two-digit hexadecimal
35623 number). This is equivalent to an @samp{S} response, except that the
35624 @samp{@var{n}:@var{r}} pairs can carry values of important registers
35625 and other information directly in the stop reply packet, reducing
35626 round-trip latency. Single-step and breakpoint traps are reported
35627 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
35631 If @var{n} is a hexadecimal number, it is a register number, and the
35632 corresponding @var{r} gives that register's value. The data @var{r} is a
35633 series of bytes in target byte order, with each byte given by a
35634 two-digit hex number.
35637 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
35638 the stopped thread, as specified in @ref{thread-id syntax}.
35641 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
35642 the core on which the stop event was detected.
35645 If @var{n} is a recognized @dfn{stop reason}, it describes a more
35646 specific event that stopped the target. The currently defined stop
35647 reasons are listed below. The @var{aa} should be @samp{05}, the trap
35648 signal. At most one stop reason should be present.
35651 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
35652 and go on to the next; this allows us to extend the protocol in the
35656 The currently defined stop reasons are:
35662 The packet indicates a watchpoint hit, and @var{r} is the data address, in
35665 @item syscall_entry
35666 @itemx syscall_return
35667 The packet indicates a syscall entry or return, and @var{r} is the
35668 syscall number, in hex.
35670 @cindex shared library events, remote reply
35672 The packet indicates that the loaded libraries have changed.
35673 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
35674 list of loaded libraries. The @var{r} part is ignored.
35676 @cindex replay log events, remote reply
35678 The packet indicates that the target cannot continue replaying
35679 logged execution events, because it has reached the end (or the
35680 beginning when executing backward) of the log. The value of @var{r}
35681 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
35682 for more information.
35685 @anchor{swbreak stop reason}
35686 The packet indicates a memory breakpoint instruction was executed,
35687 irrespective of whether it was @value{GDBN} that planted the
35688 breakpoint or the breakpoint is hardcoded in the program. The @var{r}
35689 part must be left empty.
35691 On some architectures, such as x86, at the architecture level, when a
35692 breakpoint instruction executes the program counter points at the
35693 breakpoint address plus an offset. On such targets, the stub is
35694 responsible for adjusting the PC to point back at the breakpoint
35697 This packet should not be sent by default; older @value{GDBN} versions
35698 did not support it. @value{GDBN} requests it, by supplying an
35699 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35700 remote stub must also supply the appropriate @samp{qSupported} feature
35701 indicating support.
35703 This packet is required for correct non-stop mode operation.
35706 The packet indicates the target stopped for a hardware breakpoint.
35707 The @var{r} part must be left empty.
35709 The same remarks about @samp{qSupported} and non-stop mode above
35712 @cindex fork events, remote reply
35714 The packet indicates that @code{fork} was called, and @var{r}
35715 is the thread ID of the new child process. Refer to
35716 @ref{thread-id syntax} for the format of the @var{thread-id}
35717 field. This packet is only applicable to targets that support
35720 This packet should not be sent by default; older @value{GDBN} versions
35721 did not support it. @value{GDBN} requests it, by supplying an
35722 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35723 remote stub must also supply the appropriate @samp{qSupported} feature
35724 indicating support.
35726 @cindex vfork events, remote reply
35728 The packet indicates that @code{vfork} was called, and @var{r}
35729 is the thread ID of the new child process. Refer to
35730 @ref{thread-id syntax} for the format of the @var{thread-id}
35731 field. This packet is only applicable to targets that support
35734 This packet should not be sent by default; older @value{GDBN} versions
35735 did not support it. @value{GDBN} requests it, by supplying an
35736 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35737 remote stub must also supply the appropriate @samp{qSupported} feature
35738 indicating support.
35740 @cindex vforkdone events, remote reply
35742 The packet indicates that a child process created by a vfork
35743 has either called @code{exec} or terminated, so that the
35744 address spaces of the parent and child process are no longer
35745 shared. The @var{r} part is ignored. This packet is only
35746 applicable to targets that support vforkdone events.
35748 This packet should not be sent by default; older @value{GDBN} versions
35749 did not support it. @value{GDBN} requests it, by supplying an
35750 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35751 remote stub must also supply the appropriate @samp{qSupported} feature
35752 indicating support.
35754 @cindex exec events, remote reply
35756 The packet indicates that @code{execve} was called, and @var{r}
35757 is the absolute pathname of the file that was executed, in hex.
35758 This packet is only applicable to targets that support exec events.
35760 This packet should not be sent by default; older @value{GDBN} versions
35761 did not support it. @value{GDBN} requests it, by supplying an
35762 appropriate @samp{qSupported} feature (@pxref{qSupported}). The
35763 remote stub must also supply the appropriate @samp{qSupported} feature
35764 indicating support.
35766 @cindex thread create event, remote reply
35767 @anchor{thread create event}
35769 The packet indicates that the thread was just created. The new thread
35770 is stopped until @value{GDBN} sets it running with a resumption packet
35771 (@pxref{vCont packet}). This packet should not be sent by default;
35772 @value{GDBN} requests it with the @ref{QThreadEvents} packet. See
35773 also the @samp{w} (@ref{thread exit event}) remote reply below.
35778 @itemx W @var{AA} ; process:@var{pid}
35779 The process exited, and @var{AA} is the exit status. This is only
35780 applicable to certain targets.
35782 The second form of the response, including the process ID of the exited
35783 process, can be used only when @value{GDBN} has reported support for
35784 multiprocess protocol extensions; see @ref{multiprocess extensions}.
35785 The @var{pid} is formatted as a big-endian hex string.
35788 @itemx X @var{AA} ; process:@var{pid}
35789 The process terminated with signal @var{AA}.
35791 The second form of the response, including the process ID of the
35792 terminated process, can be used only when @value{GDBN} has reported
35793 support for multiprocess protocol extensions; see @ref{multiprocess
35794 extensions}. The @var{pid} is formatted as a big-endian hex string.
35796 @anchor{thread exit event}
35797 @cindex thread exit event, remote reply
35798 @item w @var{AA} ; @var{tid}
35800 The thread exited, and @var{AA} is the exit status. This response
35801 should not be sent by default; @value{GDBN} requests it with the
35802 @ref{QThreadEvents} packet. See also @ref{thread create event} above.
35805 There are no resumed threads left in the target. In other words, even
35806 though the process is alive, the last resumed thread has exited. For
35807 example, say the target process has two threads: thread 1 and thread
35808 2. The client leaves thread 1 stopped, and resumes thread 2, which
35809 subsequently exits. At this point, even though the process is still
35810 alive, and thus no @samp{W} stop reply is sent, no thread is actually
35811 executing either. The @samp{N} stop reply thus informs the client
35812 that it can stop waiting for stop replies. This packet should not be
35813 sent by default; older @value{GDBN} versions did not support it.
35814 @value{GDBN} requests it, by supplying an appropriate
35815 @samp{qSupported} feature (@pxref{qSupported}). The remote stub must
35816 also supply the appropriate @samp{qSupported} feature indicating
35819 @item O @var{XX}@dots{}
35820 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
35821 written as the program's console output. This can happen at any time
35822 while the program is running and the debugger should continue to wait
35823 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
35825 @item F @var{call-id},@var{parameter}@dots{}
35826 @var{call-id} is the identifier which says which host system call should
35827 be called. This is just the name of the function. Translation into the
35828 correct system call is only applicable as it's defined in @value{GDBN}.
35829 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
35832 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
35833 this very system call.
35835 The target replies with this packet when it expects @value{GDBN} to
35836 call a host system call on behalf of the target. @value{GDBN} replies
35837 with an appropriate @samp{F} packet and keeps up waiting for the next
35838 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
35839 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
35840 Protocol Extension}, for more details.
35844 @node General Query Packets
35845 @section General Query Packets
35846 @cindex remote query requests
35848 Packets starting with @samp{q} are @dfn{general query packets};
35849 packets starting with @samp{Q} are @dfn{general set packets}. General
35850 query and set packets are a semi-unified form for retrieving and
35851 sending information to and from the stub.
35853 The initial letter of a query or set packet is followed by a name
35854 indicating what sort of thing the packet applies to. For example,
35855 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
35856 definitions with the stub. These packet names follow some
35861 The name must not contain commas, colons or semicolons.
35863 Most @value{GDBN} query and set packets have a leading upper case
35866 The names of custom vendor packets should use a company prefix, in
35867 lower case, followed by a period. For example, packets designed at
35868 the Acme Corporation might begin with @samp{qacme.foo} (for querying
35869 foos) or @samp{Qacme.bar} (for setting bars).
35872 The name of a query or set packet should be separated from any
35873 parameters by a @samp{:}; the parameters themselves should be
35874 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
35875 full packet name, and check for a separator or the end of the packet,
35876 in case two packet names share a common prefix. New packets should not begin
35877 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
35878 packets predate these conventions, and have arguments without any terminator
35879 for the packet name; we suspect they are in widespread use in places that
35880 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
35881 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
35884 Like the descriptions of the other packets, each description here
35885 has a template showing the packet's overall syntax, followed by an
35886 explanation of the packet's meaning. We include spaces in some of the
35887 templates for clarity; these are not part of the packet's syntax. No
35888 @value{GDBN} packet uses spaces to separate its components.
35890 Here are the currently defined query and set packets:
35896 Turn on or off the agent as a helper to perform some debugging operations
35897 delegated from @value{GDBN} (@pxref{Control Agent}).
35899 @item QAllow:@var{op}:@var{val}@dots{}
35900 @cindex @samp{QAllow} packet
35901 Specify which operations @value{GDBN} expects to request of the
35902 target, as a semicolon-separated list of operation name and value
35903 pairs. Possible values for @var{op} include @samp{WriteReg},
35904 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
35905 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
35906 indicating that @value{GDBN} will not request the operation, or 1,
35907 indicating that it may. (The target can then use this to set up its
35908 own internals optimally, for instance if the debugger never expects to
35909 insert breakpoints, it may not need to install its own trap handler.)
35912 @cindex current thread, remote request
35913 @cindex @samp{qC} packet
35914 Return the current thread ID.
35918 @item QC @var{thread-id}
35919 Where @var{thread-id} is a thread ID as documented in
35920 @ref{thread-id syntax}.
35921 @item @r{(anything else)}
35922 Any other reply implies the old thread ID.
35925 @item qCRC:@var{addr},@var{length}
35926 @cindex CRC of memory block, remote request
35927 @cindex @samp{qCRC} packet
35928 @anchor{qCRC packet}
35929 Compute the CRC checksum of a block of memory using CRC-32 defined in
35930 IEEE 802.3. The CRC is computed byte at a time, taking the most
35931 significant bit of each byte first. The initial pattern code
35932 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
35934 @emph{Note:} This is the same CRC used in validating separate debug
35935 files (@pxref{Separate Debug Files, , Debugging Information in Separate
35936 Files}). However the algorithm is slightly different. When validating
35937 separate debug files, the CRC is computed taking the @emph{least}
35938 significant bit of each byte first, and the final result is inverted to
35939 detect trailing zeros.
35944 An error (such as memory fault)
35945 @item C @var{crc32}
35946 The specified memory region's checksum is @var{crc32}.
35949 @item QDisableRandomization:@var{value}
35950 @cindex disable address space randomization, remote request
35951 @cindex @samp{QDisableRandomization} packet
35952 Some target operating systems will randomize the virtual address space
35953 of the inferior process as a security feature, but provide a feature
35954 to disable such randomization, e.g.@: to allow for a more deterministic
35955 debugging experience. On such systems, this packet with a @var{value}
35956 of 1 directs the target to disable address space randomization for
35957 processes subsequently started via @samp{vRun} packets, while a packet
35958 with a @var{value} of 0 tells the target to enable address space
35961 This packet is only available in extended mode (@pxref{extended mode}).
35966 The request succeeded.
35969 An error occurred. The error number @var{nn} is given as hex digits.
35972 An empty reply indicates that @samp{QDisableRandomization} is not supported
35976 This packet is not probed by default; the remote stub must request it,
35977 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35978 This should only be done on targets that actually support disabling
35979 address space randomization.
35982 @itemx qsThreadInfo
35983 @cindex list active threads, remote request
35984 @cindex @samp{qfThreadInfo} packet
35985 @cindex @samp{qsThreadInfo} packet
35986 Obtain a list of all active thread IDs from the target (OS). Since there
35987 may be too many active threads to fit into one reply packet, this query
35988 works iteratively: it may require more than one query/reply sequence to
35989 obtain the entire list of threads. The first query of the sequence will
35990 be the @samp{qfThreadInfo} query; subsequent queries in the
35991 sequence will be the @samp{qsThreadInfo} query.
35993 NOTE: This packet replaces the @samp{qL} query (see below).
35997 @item m @var{thread-id}
35999 @item m @var{thread-id},@var{thread-id}@dots{}
36000 a comma-separated list of thread IDs
36002 (lower case letter @samp{L}) denotes end of list.
36005 In response to each query, the target will reply with a list of one or
36006 more thread IDs, separated by commas.
36007 @value{GDBN} will respond to each reply with a request for more thread
36008 ids (using the @samp{qs} form of the query), until the target responds
36009 with @samp{l} (lower-case ell, for @dfn{last}).
36010 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36013 @emph{Note: @value{GDBN} will send the @code{qfThreadInfo} query during the
36014 initial connection with the remote target, and the very first thread ID
36015 mentioned in the reply will be stopped by @value{GDBN} in a subsequent
36016 message. Therefore, the stub should ensure that the first thread ID in
36017 the @code{qfThreadInfo} reply is suitable for being stopped by @value{GDBN}.}
36019 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36020 @cindex get thread-local storage address, remote request
36021 @cindex @samp{qGetTLSAddr} packet
36022 Fetch the address associated with thread local storage specified
36023 by @var{thread-id}, @var{offset}, and @var{lm}.
36025 @var{thread-id} is the thread ID associated with the
36026 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36028 @var{offset} is the (big endian, hex encoded) offset associated with the
36029 thread local variable. (This offset is obtained from the debug
36030 information associated with the variable.)
36032 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36033 load module associated with the thread local storage. For example,
36034 a @sc{gnu}/Linux system will pass the link map address of the shared
36035 object associated with the thread local storage under consideration.
36036 Other operating environments may choose to represent the load module
36037 differently, so the precise meaning of this parameter will vary.
36041 @item @var{XX}@dots{}
36042 Hex encoded (big endian) bytes representing the address of the thread
36043 local storage requested.
36046 An error occurred. The error number @var{nn} is given as hex digits.
36049 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36052 @item qGetTIBAddr:@var{thread-id}
36053 @cindex get thread information block address
36054 @cindex @samp{qGetTIBAddr} packet
36055 Fetch address of the Windows OS specific Thread Information Block.
36057 @var{thread-id} is the thread ID associated with the thread.
36061 @item @var{XX}@dots{}
36062 Hex encoded (big endian) bytes representing the linear address of the
36063 thread information block.
36066 An error occured. This means that either the thread was not found, or the
36067 address could not be retrieved.
36070 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36073 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36074 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36075 digit) is one to indicate the first query and zero to indicate a
36076 subsequent query; @var{threadcount} (two hex digits) is the maximum
36077 number of threads the response packet can contain; and @var{nextthread}
36078 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36079 returned in the response as @var{argthread}.
36081 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36085 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36086 Where: @var{count} (two hex digits) is the number of threads being
36087 returned; @var{done} (one hex digit) is zero to indicate more threads
36088 and one indicates no further threads; @var{argthreadid} (eight hex
36089 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36090 is a sequence of thread IDs, @var{threadid} (eight hex
36091 digits), from the target. See @code{remote.c:parse_threadlist_response()}.
36095 @cindex section offsets, remote request
36096 @cindex @samp{qOffsets} packet
36097 Get section offsets that the target used when relocating the downloaded
36102 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36103 Relocate the @code{Text} section by @var{xxx} from its original address.
36104 Relocate the @code{Data} section by @var{yyy} from its original address.
36105 If the object file format provides segment information (e.g.@: @sc{elf}
36106 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36107 segments by the supplied offsets.
36109 @emph{Note: while a @code{Bss} offset may be included in the response,
36110 @value{GDBN} ignores this and instead applies the @code{Data} offset
36111 to the @code{Bss} section.}
36113 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36114 Relocate the first segment of the object file, which conventionally
36115 contains program code, to a starting address of @var{xxx}. If
36116 @samp{DataSeg} is specified, relocate the second segment, which
36117 conventionally contains modifiable data, to a starting address of
36118 @var{yyy}. @value{GDBN} will report an error if the object file
36119 does not contain segment information, or does not contain at least
36120 as many segments as mentioned in the reply. Extra segments are
36121 kept at fixed offsets relative to the last relocated segment.
36124 @item qP @var{mode} @var{thread-id}
36125 @cindex thread information, remote request
36126 @cindex @samp{qP} packet
36127 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36128 encoded 32 bit mode; @var{thread-id} is a thread ID
36129 (@pxref{thread-id syntax}).
36131 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36134 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36138 @cindex non-stop mode, remote request
36139 @cindex @samp{QNonStop} packet
36141 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36142 @xref{Remote Non-Stop}, for more information.
36147 The request succeeded.
36150 An error occurred. The error number @var{nn} is given as hex digits.
36153 An empty reply indicates that @samp{QNonStop} is not supported by
36157 This packet is not probed by default; the remote stub must request it,
36158 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36159 Use of this packet is controlled by the @code{set non-stop} command;
36160 @pxref{Non-Stop Mode}.
36162 @item QCatchSyscalls:1 @r{[};@var{sysno}@r{]}@dots{}
36163 @itemx QCatchSyscalls:0
36164 @cindex catch syscalls from inferior, remote request
36165 @cindex @samp{QCatchSyscalls} packet
36166 @anchor{QCatchSyscalls}
36167 Enable (@samp{QCatchSyscalls:1}) or disable (@samp{QCatchSyscalls:0})
36168 catching syscalls from the inferior process.
36170 For @samp{QCatchSyscalls:1}, each listed syscall @var{sysno} (encoded
36171 in hex) should be reported to @value{GDBN}. If no syscall @var{sysno}
36172 is listed, every system call should be reported.
36174 Note that if a syscall not in the list is reported, @value{GDBN} will
36175 still filter the event according to its own list from all corresponding
36176 @code{catch syscall} commands. However, it is more efficient to only
36177 report the requested syscalls.
36179 Multiple @samp{QCatchSyscalls:1} packets do not combine; any earlier
36180 @samp{QCatchSyscalls:1} list is completely replaced by the new list.
36182 If the inferior process execs, the state of @samp{QCatchSyscalls} is
36183 kept for the new process too. On targets where exec may affect syscall
36184 numbers, for example with exec between 32 and 64-bit processes, the
36185 client should send a new packet with the new syscall list.
36190 The request succeeded.
36193 An error occurred. @var{nn} are hex digits.
36196 An empty reply indicates that @samp{QCatchSyscalls} is not supported by
36200 Use of this packet is controlled by the @code{set remote catch-syscalls}
36201 command (@pxref{Remote Configuration, set remote catch-syscalls}).
36202 This packet is not probed by default; the remote stub must request it,
36203 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36205 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36206 @cindex pass signals to inferior, remote request
36207 @cindex @samp{QPassSignals} packet
36208 @anchor{QPassSignals}
36209 Each listed @var{signal} should be passed directly to the inferior process.
36210 Signals are numbered identically to continue packets and stop replies
36211 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36212 strictly greater than the previous item. These signals do not need to stop
36213 the inferior, or be reported to @value{GDBN}. All other signals should be
36214 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36215 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36216 new list. This packet improves performance when using @samp{handle
36217 @var{signal} nostop noprint pass}.
36222 The request succeeded.
36225 An error occurred. The error number @var{nn} is given as hex digits.
36228 An empty reply indicates that @samp{QPassSignals} is not supported by
36232 Use of this packet is controlled by the @code{set remote pass-signals}
36233 command (@pxref{Remote Configuration, set remote pass-signals}).
36234 This packet is not probed by default; the remote stub must request it,
36235 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36237 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36238 @cindex signals the inferior may see, remote request
36239 @cindex @samp{QProgramSignals} packet
36240 @anchor{QProgramSignals}
36241 Each listed @var{signal} may be delivered to the inferior process.
36242 Others should be silently discarded.
36244 In some cases, the remote stub may need to decide whether to deliver a
36245 signal to the program or not without @value{GDBN} involvement. One
36246 example of that is while detaching --- the program's threads may have
36247 stopped for signals that haven't yet had a chance of being reported to
36248 @value{GDBN}, and so the remote stub can use the signal list specified
36249 by this packet to know whether to deliver or ignore those pending
36252 This does not influence whether to deliver a signal as requested by a
36253 resumption packet (@pxref{vCont packet}).
36255 Signals are numbered identically to continue packets and stop replies
36256 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36257 strictly greater than the previous item. Multiple
36258 @samp{QProgramSignals} packets do not combine; any earlier
36259 @samp{QProgramSignals} list is completely replaced by the new list.
36264 The request succeeded.
36267 An error occurred. The error number @var{nn} is given as hex digits.
36270 An empty reply indicates that @samp{QProgramSignals} is not supported
36274 Use of this packet is controlled by the @code{set remote program-signals}
36275 command (@pxref{Remote Configuration, set remote program-signals}).
36276 This packet is not probed by default; the remote stub must request it,
36277 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36279 @anchor{QThreadEvents}
36280 @item QThreadEvents:1
36281 @itemx QThreadEvents:0
36282 @cindex thread create/exit events, remote request
36283 @cindex @samp{QThreadEvents} packet
36285 Enable (@samp{QThreadEvents:1}) or disable (@samp{QThreadEvents:0})
36286 reporting of thread create and exit events. @xref{thread create
36287 event}, for the reply specifications. For example, this is used in
36288 non-stop mode when @value{GDBN} stops a set of threads and
36289 synchronously waits for the their corresponding stop replies. Without
36290 exit events, if one of the threads exits, @value{GDBN} would hang
36291 forever not knowing that it should no longer expect a stop for that
36292 same thread. @value{GDBN} does not enable this feature unless the
36293 stub reports that it supports it by including @samp{QThreadEvents+} in
36294 its @samp{qSupported} reply.
36299 The request succeeded.
36302 An error occurred. The error number @var{nn} is given as hex digits.
36305 An empty reply indicates that @samp{QThreadEvents} is not supported by
36309 Use of this packet is controlled by the @code{set remote thread-events}
36310 command (@pxref{Remote Configuration, set remote thread-events}).
36312 @item qRcmd,@var{command}
36313 @cindex execute remote command, remote request
36314 @cindex @samp{qRcmd} packet
36315 @var{command} (hex encoded) is passed to the local interpreter for
36316 execution. Invalid commands should be reported using the output
36317 string. Before the final result packet, the target may also respond
36318 with a number of intermediate @samp{O@var{output}} console output
36319 packets. @emph{Implementors should note that providing access to a
36320 stubs's interpreter may have security implications}.
36325 A command response with no output.
36327 A command response with the hex encoded output string @var{OUTPUT}.
36329 Indicate a badly formed request.
36331 An empty reply indicates that @samp{qRcmd} is not recognized.
36334 (Note that the @code{qRcmd} packet's name is separated from the
36335 command by a @samp{,}, not a @samp{:}, contrary to the naming
36336 conventions above. Please don't use this packet as a model for new
36339 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
36340 @cindex searching memory, in remote debugging
36342 @cindex @samp{qSearch:memory} packet
36344 @cindex @samp{qSearch memory} packet
36345 @anchor{qSearch memory}
36346 Search @var{length} bytes at @var{address} for @var{search-pattern}.
36347 Both @var{address} and @var{length} are encoded in hex;
36348 @var{search-pattern} is a sequence of bytes, also hex encoded.
36353 The pattern was not found.
36355 The pattern was found at @var{address}.
36357 A badly formed request or an error was encountered while searching memory.
36359 An empty reply indicates that @samp{qSearch:memory} is not recognized.
36362 @item QStartNoAckMode
36363 @cindex @samp{QStartNoAckMode} packet
36364 @anchor{QStartNoAckMode}
36365 Request that the remote stub disable the normal @samp{+}/@samp{-}
36366 protocol acknowledgments (@pxref{Packet Acknowledgment}).
36371 The stub has switched to no-acknowledgment mode.
36372 @value{GDBN} acknowledges this reponse,
36373 but neither the stub nor @value{GDBN} shall send or expect further
36374 @samp{+}/@samp{-} acknowledgments in the current connection.
36376 An empty reply indicates that the stub does not support no-acknowledgment mode.
36379 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
36380 @cindex supported packets, remote query
36381 @cindex features of the remote protocol
36382 @cindex @samp{qSupported} packet
36383 @anchor{qSupported}
36384 Tell the remote stub about features supported by @value{GDBN}, and
36385 query the stub for features it supports. This packet allows
36386 @value{GDBN} and the remote stub to take advantage of each others'
36387 features. @samp{qSupported} also consolidates multiple feature probes
36388 at startup, to improve @value{GDBN} performance---a single larger
36389 packet performs better than multiple smaller probe packets on
36390 high-latency links. Some features may enable behavior which must not
36391 be on by default, e.g.@: because it would confuse older clients or
36392 stubs. Other features may describe packets which could be
36393 automatically probed for, but are not. These features must be
36394 reported before @value{GDBN} will use them. This ``default
36395 unsupported'' behavior is not appropriate for all packets, but it
36396 helps to keep the initial connection time under control with new
36397 versions of @value{GDBN} which support increasing numbers of packets.
36401 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
36402 The stub supports or does not support each returned @var{stubfeature},
36403 depending on the form of each @var{stubfeature} (see below for the
36406 An empty reply indicates that @samp{qSupported} is not recognized,
36407 or that no features needed to be reported to @value{GDBN}.
36410 The allowed forms for each feature (either a @var{gdbfeature} in the
36411 @samp{qSupported} packet, or a @var{stubfeature} in the response)
36415 @item @var{name}=@var{value}
36416 The remote protocol feature @var{name} is supported, and associated
36417 with the specified @var{value}. The format of @var{value} depends
36418 on the feature, but it must not include a semicolon.
36420 The remote protocol feature @var{name} is supported, and does not
36421 need an associated value.
36423 The remote protocol feature @var{name} is not supported.
36425 The remote protocol feature @var{name} may be supported, and
36426 @value{GDBN} should auto-detect support in some other way when it is
36427 needed. This form will not be used for @var{gdbfeature} notifications,
36428 but may be used for @var{stubfeature} responses.
36431 Whenever the stub receives a @samp{qSupported} request, the
36432 supplied set of @value{GDBN} features should override any previous
36433 request. This allows @value{GDBN} to put the stub in a known
36434 state, even if the stub had previously been communicating with
36435 a different version of @value{GDBN}.
36437 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
36442 This feature indicates whether @value{GDBN} supports multiprocess
36443 extensions to the remote protocol. @value{GDBN} does not use such
36444 extensions unless the stub also reports that it supports them by
36445 including @samp{multiprocess+} in its @samp{qSupported} reply.
36446 @xref{multiprocess extensions}, for details.
36449 This feature indicates that @value{GDBN} supports the XML target
36450 description. If the stub sees @samp{xmlRegisters=} with target
36451 specific strings separated by a comma, it will report register
36455 This feature indicates whether @value{GDBN} supports the
36456 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
36457 instruction reply packet}).
36460 This feature indicates whether @value{GDBN} supports the swbreak stop
36461 reason in stop replies. @xref{swbreak stop reason}, for details.
36464 This feature indicates whether @value{GDBN} supports the hwbreak stop
36465 reason in stop replies. @xref{swbreak stop reason}, for details.
36468 This feature indicates whether @value{GDBN} supports fork event
36469 extensions to the remote protocol. @value{GDBN} does not use such
36470 extensions unless the stub also reports that it supports them by
36471 including @samp{fork-events+} in its @samp{qSupported} reply.
36474 This feature indicates whether @value{GDBN} supports vfork event
36475 extensions to the remote protocol. @value{GDBN} does not use such
36476 extensions unless the stub also reports that it supports them by
36477 including @samp{vfork-events+} in its @samp{qSupported} reply.
36480 This feature indicates whether @value{GDBN} supports exec event
36481 extensions to the remote protocol. @value{GDBN} does not use such
36482 extensions unless the stub also reports that it supports them by
36483 including @samp{exec-events+} in its @samp{qSupported} reply.
36485 @item vContSupported
36486 This feature indicates whether @value{GDBN} wants to know the
36487 supported actions in the reply to @samp{vCont?} packet.
36490 Stubs should ignore any unknown values for
36491 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
36492 packet supports receiving packets of unlimited length (earlier
36493 versions of @value{GDBN} may reject overly long responses). Additional values
36494 for @var{gdbfeature} may be defined in the future to let the stub take
36495 advantage of new features in @value{GDBN}, e.g.@: incompatible
36496 improvements in the remote protocol---the @samp{multiprocess} feature is
36497 an example of such a feature. The stub's reply should be independent
36498 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
36499 describes all the features it supports, and then the stub replies with
36500 all the features it supports.
36502 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
36503 responses, as long as each response uses one of the standard forms.
36505 Some features are flags. A stub which supports a flag feature
36506 should respond with a @samp{+} form response. Other features
36507 require values, and the stub should respond with an @samp{=}
36510 Each feature has a default value, which @value{GDBN} will use if
36511 @samp{qSupported} is not available or if the feature is not mentioned
36512 in the @samp{qSupported} response. The default values are fixed; a
36513 stub is free to omit any feature responses that match the defaults.
36515 Not all features can be probed, but for those which can, the probing
36516 mechanism is useful: in some cases, a stub's internal
36517 architecture may not allow the protocol layer to know some information
36518 about the underlying target in advance. This is especially common in
36519 stubs which may be configured for multiple targets.
36521 These are the currently defined stub features and their properties:
36523 @multitable @columnfractions 0.35 0.2 0.12 0.2
36524 @c NOTE: The first row should be @headitem, but we do not yet require
36525 @c a new enough version of Texinfo (4.7) to use @headitem.
36527 @tab Value Required
36531 @item @samp{PacketSize}
36536 @item @samp{qXfer:auxv:read}
36541 @item @samp{qXfer:btrace:read}
36546 @item @samp{qXfer:btrace-conf:read}
36551 @item @samp{qXfer:exec-file:read}
36556 @item @samp{qXfer:features:read}
36561 @item @samp{qXfer:libraries:read}
36566 @item @samp{qXfer:libraries-svr4:read}
36571 @item @samp{augmented-libraries-svr4-read}
36576 @item @samp{qXfer:memory-map:read}
36581 @item @samp{qXfer:sdata:read}
36586 @item @samp{qXfer:spu:read}
36591 @item @samp{qXfer:spu:write}
36596 @item @samp{qXfer:siginfo:read}
36601 @item @samp{qXfer:siginfo:write}
36606 @item @samp{qXfer:threads:read}
36611 @item @samp{qXfer:traceframe-info:read}
36616 @item @samp{qXfer:uib:read}
36621 @item @samp{qXfer:fdpic:read}
36626 @item @samp{Qbtrace:off}
36631 @item @samp{Qbtrace:bts}
36636 @item @samp{Qbtrace:pt}
36641 @item @samp{Qbtrace-conf:bts:size}
36646 @item @samp{Qbtrace-conf:pt:size}
36651 @item @samp{QNonStop}
36656 @item @samp{QCatchSyscalls}
36661 @item @samp{QPassSignals}
36666 @item @samp{QStartNoAckMode}
36671 @item @samp{multiprocess}
36676 @item @samp{ConditionalBreakpoints}
36681 @item @samp{ConditionalTracepoints}
36686 @item @samp{ReverseContinue}
36691 @item @samp{ReverseStep}
36696 @item @samp{TracepointSource}
36701 @item @samp{QAgent}
36706 @item @samp{QAllow}
36711 @item @samp{QDisableRandomization}
36716 @item @samp{EnableDisableTracepoints}
36721 @item @samp{QTBuffer:size}
36726 @item @samp{tracenz}
36731 @item @samp{BreakpointCommands}
36736 @item @samp{swbreak}
36741 @item @samp{hwbreak}
36746 @item @samp{fork-events}
36751 @item @samp{vfork-events}
36756 @item @samp{exec-events}
36761 @item @samp{QThreadEvents}
36766 @item @samp{no-resumed}
36773 These are the currently defined stub features, in more detail:
36776 @cindex packet size, remote protocol
36777 @item PacketSize=@var{bytes}
36778 The remote stub can accept packets up to at least @var{bytes} in
36779 length. @value{GDBN} will send packets up to this size for bulk
36780 transfers, and will never send larger packets. This is a limit on the
36781 data characters in the packet, including the frame and checksum.
36782 There is no trailing NUL byte in a remote protocol packet; if the stub
36783 stores packets in a NUL-terminated format, it should allow an extra
36784 byte in its buffer for the NUL. If this stub feature is not supported,
36785 @value{GDBN} guesses based on the size of the @samp{g} packet response.
36787 @item qXfer:auxv:read
36788 The remote stub understands the @samp{qXfer:auxv:read} packet
36789 (@pxref{qXfer auxiliary vector read}).
36791 @item qXfer:btrace:read
36792 The remote stub understands the @samp{qXfer:btrace:read}
36793 packet (@pxref{qXfer btrace read}).
36795 @item qXfer:btrace-conf:read
36796 The remote stub understands the @samp{qXfer:btrace-conf:read}
36797 packet (@pxref{qXfer btrace-conf read}).
36799 @item qXfer:exec-file:read
36800 The remote stub understands the @samp{qXfer:exec-file:read} packet
36801 (@pxref{qXfer executable filename read}).
36803 @item qXfer:features:read
36804 The remote stub understands the @samp{qXfer:features:read} packet
36805 (@pxref{qXfer target description read}).
36807 @item qXfer:libraries:read
36808 The remote stub understands the @samp{qXfer:libraries:read} packet
36809 (@pxref{qXfer library list read}).
36811 @item qXfer:libraries-svr4:read
36812 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
36813 (@pxref{qXfer svr4 library list read}).
36815 @item augmented-libraries-svr4-read
36816 The remote stub understands the augmented form of the
36817 @samp{qXfer:libraries-svr4:read} packet
36818 (@pxref{qXfer svr4 library list read}).
36820 @item qXfer:memory-map:read
36821 The remote stub understands the @samp{qXfer:memory-map:read} packet
36822 (@pxref{qXfer memory map read}).
36824 @item qXfer:sdata:read
36825 The remote stub understands the @samp{qXfer:sdata:read} packet
36826 (@pxref{qXfer sdata read}).
36828 @item qXfer:spu:read
36829 The remote stub understands the @samp{qXfer:spu:read} packet
36830 (@pxref{qXfer spu read}).
36832 @item qXfer:spu:write
36833 The remote stub understands the @samp{qXfer:spu:write} packet
36834 (@pxref{qXfer spu write}).
36836 @item qXfer:siginfo:read
36837 The remote stub understands the @samp{qXfer:siginfo:read} packet
36838 (@pxref{qXfer siginfo read}).
36840 @item qXfer:siginfo:write
36841 The remote stub understands the @samp{qXfer:siginfo:write} packet
36842 (@pxref{qXfer siginfo write}).
36844 @item qXfer:threads:read
36845 The remote stub understands the @samp{qXfer:threads:read} packet
36846 (@pxref{qXfer threads read}).
36848 @item qXfer:traceframe-info:read
36849 The remote stub understands the @samp{qXfer:traceframe-info:read}
36850 packet (@pxref{qXfer traceframe info read}).
36852 @item qXfer:uib:read
36853 The remote stub understands the @samp{qXfer:uib:read}
36854 packet (@pxref{qXfer unwind info block}).
36856 @item qXfer:fdpic:read
36857 The remote stub understands the @samp{qXfer:fdpic:read}
36858 packet (@pxref{qXfer fdpic loadmap read}).
36861 The remote stub understands the @samp{QNonStop} packet
36862 (@pxref{QNonStop}).
36864 @item QCatchSyscalls
36865 The remote stub understands the @samp{QCatchSyscalls} packet
36866 (@pxref{QCatchSyscalls}).
36869 The remote stub understands the @samp{QPassSignals} packet
36870 (@pxref{QPassSignals}).
36872 @item QStartNoAckMode
36873 The remote stub understands the @samp{QStartNoAckMode} packet and
36874 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
36877 @anchor{multiprocess extensions}
36878 @cindex multiprocess extensions, in remote protocol
36879 The remote stub understands the multiprocess extensions to the remote
36880 protocol syntax. The multiprocess extensions affect the syntax of
36881 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
36882 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
36883 replies. Note that reporting this feature indicates support for the
36884 syntactic extensions only, not that the stub necessarily supports
36885 debugging of more than one process at a time. The stub must not use
36886 multiprocess extensions in packet replies unless @value{GDBN} has also
36887 indicated it supports them in its @samp{qSupported} request.
36889 @item qXfer:osdata:read
36890 The remote stub understands the @samp{qXfer:osdata:read} packet
36891 ((@pxref{qXfer osdata read}).
36893 @item ConditionalBreakpoints
36894 The target accepts and implements evaluation of conditional expressions
36895 defined for breakpoints. The target will only report breakpoint triggers
36896 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
36898 @item ConditionalTracepoints
36899 The remote stub accepts and implements conditional expressions defined
36900 for tracepoints (@pxref{Tracepoint Conditions}).
36902 @item ReverseContinue
36903 The remote stub accepts and implements the reverse continue packet
36907 The remote stub accepts and implements the reverse step packet
36910 @item TracepointSource
36911 The remote stub understands the @samp{QTDPsrc} packet that supplies
36912 the source form of tracepoint definitions.
36915 The remote stub understands the @samp{QAgent} packet.
36918 The remote stub understands the @samp{QAllow} packet.
36920 @item QDisableRandomization
36921 The remote stub understands the @samp{QDisableRandomization} packet.
36923 @item StaticTracepoint
36924 @cindex static tracepoints, in remote protocol
36925 The remote stub supports static tracepoints.
36927 @item InstallInTrace
36928 @anchor{install tracepoint in tracing}
36929 The remote stub supports installing tracepoint in tracing.
36931 @item EnableDisableTracepoints
36932 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
36933 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
36934 to be enabled and disabled while a trace experiment is running.
36936 @item QTBuffer:size
36937 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
36938 packet that allows to change the size of the trace buffer.
36941 @cindex string tracing, in remote protocol
36942 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
36943 See @ref{Bytecode Descriptions} for details about the bytecode.
36945 @item BreakpointCommands
36946 @cindex breakpoint commands, in remote protocol
36947 The remote stub supports running a breakpoint's command list itself,
36948 rather than reporting the hit to @value{GDBN}.
36951 The remote stub understands the @samp{Qbtrace:off} packet.
36954 The remote stub understands the @samp{Qbtrace:bts} packet.
36957 The remote stub understands the @samp{Qbtrace:pt} packet.
36959 @item Qbtrace-conf:bts:size
36960 The remote stub understands the @samp{Qbtrace-conf:bts:size} packet.
36962 @item Qbtrace-conf:pt:size
36963 The remote stub understands the @samp{Qbtrace-conf:pt:size} packet.
36966 The remote stub reports the @samp{swbreak} stop reason for memory
36970 The remote stub reports the @samp{hwbreak} stop reason for hardware
36974 The remote stub reports the @samp{fork} stop reason for fork events.
36977 The remote stub reports the @samp{vfork} stop reason for vfork events
36978 and vforkdone events.
36981 The remote stub reports the @samp{exec} stop reason for exec events.
36983 @item vContSupported
36984 The remote stub reports the supported actions in the reply to
36985 @samp{vCont?} packet.
36987 @item QThreadEvents
36988 The remote stub understands the @samp{QThreadEvents} packet.
36991 The remote stub reports the @samp{N} stop reply.
36996 @cindex symbol lookup, remote request
36997 @cindex @samp{qSymbol} packet
36998 Notify the target that @value{GDBN} is prepared to serve symbol lookup
36999 requests. Accept requests from the target for the values of symbols.
37004 The target does not need to look up any (more) symbols.
37005 @item qSymbol:@var{sym_name}
37006 The target requests the value of symbol @var{sym_name} (hex encoded).
37007 @value{GDBN} may provide the value by using the
37008 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37012 @item qSymbol:@var{sym_value}:@var{sym_name}
37013 Set the value of @var{sym_name} to @var{sym_value}.
37015 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37016 target has previously requested.
37018 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37019 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37025 The target does not need to look up any (more) symbols.
37026 @item qSymbol:@var{sym_name}
37027 The target requests the value of a new symbol @var{sym_name} (hex
37028 encoded). @value{GDBN} will continue to supply the values of symbols
37029 (if available), until the target ceases to request them.
37034 @itemx QTDisconnected
37041 @itemx qTMinFTPILen
37043 @xref{Tracepoint Packets}.
37045 @item qThreadExtraInfo,@var{thread-id}
37046 @cindex thread attributes info, remote request
37047 @cindex @samp{qThreadExtraInfo} packet
37048 Obtain from the target OS a printable string description of thread
37049 attributes for the thread @var{thread-id}; see @ref{thread-id syntax},
37050 for the forms of @var{thread-id}. This
37051 string may contain anything that the target OS thinks is interesting
37052 for @value{GDBN} to tell the user about the thread. The string is
37053 displayed in @value{GDBN}'s @code{info threads} display. Some
37054 examples of possible thread extra info strings are @samp{Runnable}, or
37055 @samp{Blocked on Mutex}.
37059 @item @var{XX}@dots{}
37060 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37061 comprising the printable string containing the extra information about
37062 the thread's attributes.
37065 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37066 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37067 conventions above. Please don't use this packet as a model for new
37086 @xref{Tracepoint Packets}.
37088 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37089 @cindex read special object, remote request
37090 @cindex @samp{qXfer} packet
37091 @anchor{qXfer read}
37092 Read uninterpreted bytes from the target's special data area
37093 identified by the keyword @var{object}. Request @var{length} bytes
37094 starting at @var{offset} bytes into the data. The content and
37095 encoding of @var{annex} is specific to @var{object}; it can supply
37096 additional details about what data to access.
37098 Here are the specific requests of this form defined so far. All
37099 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37100 formats, listed below.
37103 @item qXfer:auxv:read::@var{offset},@var{length}
37104 @anchor{qXfer auxiliary vector read}
37105 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37106 auxiliary vector}. Note @var{annex} must be empty.
37108 This packet is not probed by default; the remote stub must request it,
37109 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37111 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37112 @anchor{qXfer btrace read}
37114 Return a description of the current branch trace.
37115 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37116 packet may have one of the following values:
37120 Returns all available branch trace.
37123 Returns all available branch trace if the branch trace changed since
37124 the last read request.
37127 Returns the new branch trace since the last read request. Adds a new
37128 block to the end of the trace that begins at zero and ends at the source
37129 location of the first branch in the trace buffer. This extra block is
37130 used to stitch traces together.
37132 If the trace buffer overflowed, returns an error indicating the overflow.
37135 This packet is not probed by default; the remote stub must request it
37136 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37138 @item qXfer:btrace-conf:read::@var{offset},@var{length}
37139 @anchor{qXfer btrace-conf read}
37141 Return a description of the current branch trace configuration.
37142 @xref{Branch Trace Configuration Format}.
37144 This packet is not probed by default; the remote stub must request it
37145 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37147 @item qXfer:exec-file:read:@var{annex}:@var{offset},@var{length}
37148 @anchor{qXfer executable filename read}
37149 Return the full absolute name of the file that was executed to create
37150 a process running on the remote system. The annex specifies the
37151 numeric process ID of the process to query, encoded as a hexadecimal
37152 number. If the annex part is empty the remote stub should return the
37153 filename corresponding to the currently executing process.
37155 This packet is not probed by default; the remote stub must request it,
37156 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37158 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37159 @anchor{qXfer target description read}
37160 Access the @dfn{target description}. @xref{Target Descriptions}. The
37161 annex specifies which XML document to access. The main description is
37162 always loaded from the @samp{target.xml} annex.
37164 This packet is not probed by default; the remote stub must request it,
37165 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37167 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37168 @anchor{qXfer library list read}
37169 Access the target's list of loaded libraries. @xref{Library List Format}.
37170 The annex part of the generic @samp{qXfer} packet must be empty
37171 (@pxref{qXfer read}).
37173 Targets which maintain a list of libraries in the program's memory do
37174 not need to implement this packet; it is designed for platforms where
37175 the operating system manages the list of loaded libraries.
37177 This packet is not probed by default; the remote stub must request it,
37178 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37180 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37181 @anchor{qXfer svr4 library list read}
37182 Access the target's list of loaded libraries when the target is an SVR4
37183 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37184 of the generic @samp{qXfer} packet must be empty unless the remote
37185 stub indicated it supports the augmented form of this packet
37186 by supplying an appropriate @samp{qSupported} response
37187 (@pxref{qXfer read}, @ref{qSupported}).
37189 This packet is optional for better performance on SVR4 targets.
37190 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37192 This packet is not probed by default; the remote stub must request it,
37193 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37195 If the remote stub indicates it supports the augmented form of this
37196 packet then the annex part of the generic @samp{qXfer} packet may
37197 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
37198 arguments. The currently supported arguments are:
37201 @item start=@var{address}
37202 A hexadecimal number specifying the address of the @samp{struct
37203 link_map} to start reading the library list from. If unset or zero
37204 then the first @samp{struct link_map} in the library list will be
37205 chosen as the starting point.
37207 @item prev=@var{address}
37208 A hexadecimal number specifying the address of the @samp{struct
37209 link_map} immediately preceding the @samp{struct link_map}
37210 specified by the @samp{start} argument. If unset or zero then
37211 the remote stub will expect that no @samp{struct link_map}
37212 exists prior to the starting point.
37216 Arguments that are not understood by the remote stub will be silently
37219 @item qXfer:memory-map:read::@var{offset},@var{length}
37220 @anchor{qXfer memory map read}
37221 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37222 annex part of the generic @samp{qXfer} packet must be empty
37223 (@pxref{qXfer read}).
37225 This packet is not probed by default; the remote stub must request it,
37226 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37228 @item qXfer:sdata:read::@var{offset},@var{length}
37229 @anchor{qXfer sdata read}
37231 Read contents of the extra collected static tracepoint marker
37232 information. The annex part of the generic @samp{qXfer} packet must
37233 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37236 This packet is not probed by default; the remote stub must request it,
37237 by supplying an appropriate @samp{qSupported} response
37238 (@pxref{qSupported}).
37240 @item qXfer:siginfo:read::@var{offset},@var{length}
37241 @anchor{qXfer siginfo read}
37242 Read contents of the extra signal information on the target
37243 system. The annex part of the generic @samp{qXfer} packet must be
37244 empty (@pxref{qXfer read}).
37246 This packet is not probed by default; the remote stub must request it,
37247 by supplying an appropriate @samp{qSupported} response
37248 (@pxref{qSupported}).
37250 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37251 @anchor{qXfer spu read}
37252 Read contents of an @code{spufs} file on the target system. The
37253 annex specifies which file to read; it must be of the form
37254 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37255 in the target process, and @var{name} identifes the @code{spufs} file
37256 in that context to be accessed.
37258 This packet is not probed by default; the remote stub must request it,
37259 by supplying an appropriate @samp{qSupported} response
37260 (@pxref{qSupported}).
37262 @item qXfer:threads:read::@var{offset},@var{length}
37263 @anchor{qXfer threads read}
37264 Access the list of threads on target. @xref{Thread List Format}. The
37265 annex part of the generic @samp{qXfer} packet must be empty
37266 (@pxref{qXfer read}).
37268 This packet is not probed by default; the remote stub must request it,
37269 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37271 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37272 @anchor{qXfer traceframe info read}
37274 Return a description of the current traceframe's contents.
37275 @xref{Traceframe Info Format}. The annex part of the generic
37276 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37278 This packet is not probed by default; the remote stub must request it,
37279 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37281 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37282 @anchor{qXfer unwind info block}
37284 Return the unwind information block for @var{pc}. This packet is used
37285 on OpenVMS/ia64 to ask the kernel unwind information.
37287 This packet is not probed by default.
37289 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37290 @anchor{qXfer fdpic loadmap read}
37291 Read contents of @code{loadmap}s on the target system. The
37292 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37293 executable @code{loadmap} or interpreter @code{loadmap} to read.
37295 This packet is not probed by default; the remote stub must request it,
37296 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37298 @item qXfer:osdata:read::@var{offset},@var{length}
37299 @anchor{qXfer osdata read}
37300 Access the target's @dfn{operating system information}.
37301 @xref{Operating System Information}.
37308 Data @var{data} (@pxref{Binary Data}) has been read from the
37309 target. There may be more data at a higher address (although
37310 it is permitted to return @samp{m} even for the last valid
37311 block of data, as long as at least one byte of data was read).
37312 It is possible for @var{data} to have fewer bytes than the @var{length} in the
37316 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37317 There is no more data to be read. It is possible for @var{data} to
37318 have fewer bytes than the @var{length} in the request.
37321 The @var{offset} in the request is at the end of the data.
37322 There is no more data to be read.
37325 The request was malformed, or @var{annex} was invalid.
37328 The offset was invalid, or there was an error encountered reading the data.
37329 The @var{nn} part is a hex-encoded @code{errno} value.
37332 An empty reply indicates the @var{object} string was not recognized by
37333 the stub, or that the object does not support reading.
37336 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37337 @cindex write data into object, remote request
37338 @anchor{qXfer write}
37339 Write uninterpreted bytes into the target's special data area
37340 identified by the keyword @var{object}, starting at @var{offset} bytes
37341 into the data. The binary-encoded data (@pxref{Binary Data}) to be
37342 written is given by @var{data}@dots{}. The content and encoding of @var{annex}
37343 is specific to @var{object}; it can supply additional details about what data
37346 Here are the specific requests of this form defined so far. All
37347 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37348 formats, listed below.
37351 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37352 @anchor{qXfer siginfo write}
37353 Write @var{data} to the extra signal information on the target system.
37354 The annex part of the generic @samp{qXfer} packet must be
37355 empty (@pxref{qXfer write}).
37357 This packet is not probed by default; the remote stub must request it,
37358 by supplying an appropriate @samp{qSupported} response
37359 (@pxref{qSupported}).
37361 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37362 @anchor{qXfer spu write}
37363 Write @var{data} to an @code{spufs} file on the target system. The
37364 annex specifies which file to write; it must be of the form
37365 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37366 in the target process, and @var{name} identifes the @code{spufs} file
37367 in that context to be accessed.
37369 This packet is not probed by default; the remote stub must request it,
37370 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37376 @var{nn} (hex encoded) is the number of bytes written.
37377 This may be fewer bytes than supplied in the request.
37380 The request was malformed, or @var{annex} was invalid.
37383 The offset was invalid, or there was an error encountered writing the data.
37384 The @var{nn} part is a hex-encoded @code{errno} value.
37387 An empty reply indicates the @var{object} string was not
37388 recognized by the stub, or that the object does not support writing.
37391 @item qXfer:@var{object}:@var{operation}:@dots{}
37392 Requests of this form may be added in the future. When a stub does
37393 not recognize the @var{object} keyword, or its support for
37394 @var{object} does not recognize the @var{operation} keyword, the stub
37395 must respond with an empty packet.
37397 @item qAttached:@var{pid}
37398 @cindex query attached, remote request
37399 @cindex @samp{qAttached} packet
37400 Return an indication of whether the remote server attached to an
37401 existing process or created a new process. When the multiprocess
37402 protocol extensions are supported (@pxref{multiprocess extensions}),
37403 @var{pid} is an integer in hexadecimal format identifying the target
37404 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37405 the query packet will be simplified as @samp{qAttached}.
37407 This query is used, for example, to know whether the remote process
37408 should be detached or killed when a @value{GDBN} session is ended with
37409 the @code{quit} command.
37414 The remote server attached to an existing process.
37416 The remote server created a new process.
37418 A badly formed request or an error was encountered.
37422 Enable branch tracing for the current thread using Branch Trace Store.
37427 Branch tracing has been enabled.
37429 A badly formed request or an error was encountered.
37433 Enable branch tracing for the current thread using Intel Processor Trace.
37438 Branch tracing has been enabled.
37440 A badly formed request or an error was encountered.
37444 Disable branch tracing for the current thread.
37449 Branch tracing has been disabled.
37451 A badly formed request or an error was encountered.
37454 @item Qbtrace-conf:bts:size=@var{value}
37455 Set the requested ring buffer size for new threads that use the
37456 btrace recording method in bts format.
37461 The ring buffer size has been set.
37463 A badly formed request or an error was encountered.
37466 @item Qbtrace-conf:pt:size=@var{value}
37467 Set the requested ring buffer size for new threads that use the
37468 btrace recording method in pt format.
37473 The ring buffer size has been set.
37475 A badly formed request or an error was encountered.
37480 @node Architecture-Specific Protocol Details
37481 @section Architecture-Specific Protocol Details
37483 This section describes how the remote protocol is applied to specific
37484 target architectures. Also see @ref{Standard Target Features}, for
37485 details of XML target descriptions for each architecture.
37488 * ARM-Specific Protocol Details::
37489 * MIPS-Specific Protocol Details::
37492 @node ARM-Specific Protocol Details
37493 @subsection @acronym{ARM}-specific Protocol Details
37496 * ARM Breakpoint Kinds::
37499 @node ARM Breakpoint Kinds
37500 @subsubsection @acronym{ARM} Breakpoint Kinds
37501 @cindex breakpoint kinds, @acronym{ARM}
37503 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37508 16-bit Thumb mode breakpoint.
37511 32-bit Thumb mode (Thumb-2) breakpoint.
37514 32-bit @acronym{ARM} mode breakpoint.
37518 @node MIPS-Specific Protocol Details
37519 @subsection @acronym{MIPS}-specific Protocol Details
37522 * MIPS Register packet Format::
37523 * MIPS Breakpoint Kinds::
37526 @node MIPS Register packet Format
37527 @subsubsection @acronym{MIPS} Register Packet Format
37528 @cindex register packet format, @acronym{MIPS}
37530 The following @code{g}/@code{G} packets have previously been defined.
37531 In the below, some thirty-two bit registers are transferred as
37532 sixty-four bits. Those registers should be zero/sign extended (which?)
37533 to fill the space allocated. Register bytes are transferred in target
37534 byte order. The two nibbles within a register byte are transferred
37535 most-significant -- least-significant.
37540 All registers are transferred as thirty-two bit quantities in the order:
37541 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37542 registers; fsr; fir; fp.
37545 All registers are transferred as sixty-four bit quantities (including
37546 thirty-two bit registers such as @code{sr}). The ordering is the same
37551 @node MIPS Breakpoint Kinds
37552 @subsubsection @acronym{MIPS} Breakpoint Kinds
37553 @cindex breakpoint kinds, @acronym{MIPS}
37555 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37560 16-bit @acronym{MIPS16} mode breakpoint.
37563 16-bit @acronym{microMIPS} mode breakpoint.
37566 32-bit standard @acronym{MIPS} mode breakpoint.
37569 32-bit @acronym{microMIPS} mode breakpoint.
37573 @node Tracepoint Packets
37574 @section Tracepoint Packets
37575 @cindex tracepoint packets
37576 @cindex packets, tracepoint
37578 Here we describe the packets @value{GDBN} uses to implement
37579 tracepoints (@pxref{Tracepoints}).
37583 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
37584 @cindex @samp{QTDP} packet
37585 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
37586 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
37587 the tracepoint is disabled. The @var{step} gives the tracepoint's step
37588 count, and @var{pass} gives its pass count. If an @samp{F} is present,
37589 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
37590 the number of bytes that the target should copy elsewhere to make room
37591 for the tracepoint. If an @samp{X} is present, it introduces a
37592 tracepoint condition, which consists of a hexadecimal length, followed
37593 by a comma and hex-encoded bytes, in a manner similar to action
37594 encodings as described below. If the trailing @samp{-} is present,
37595 further @samp{QTDP} packets will follow to specify this tracepoint's
37601 The packet was understood and carried out.
37603 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37605 The packet was not recognized.
37608 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
37609 Define actions to be taken when a tracepoint is hit. The @var{n} and
37610 @var{addr} must be the same as in the initial @samp{QTDP} packet for
37611 this tracepoint. This packet may only be sent immediately after
37612 another @samp{QTDP} packet that ended with a @samp{-}. If the
37613 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
37614 specifying more actions for this tracepoint.
37616 In the series of action packets for a given tracepoint, at most one
37617 can have an @samp{S} before its first @var{action}. If such a packet
37618 is sent, it and the following packets define ``while-stepping''
37619 actions. Any prior packets define ordinary actions --- that is, those
37620 taken when the tracepoint is first hit. If no action packet has an
37621 @samp{S}, then all the packets in the series specify ordinary
37622 tracepoint actions.
37624 The @samp{@var{action}@dots{}} portion of the packet is a series of
37625 actions, concatenated without separators. Each action has one of the
37631 Collect the registers whose bits are set in @var{mask},
37632 a hexadecimal number whose @var{i}'th bit is set if register number
37633 @var{i} should be collected. (The least significant bit is numbered
37634 zero.) Note that @var{mask} may be any number of digits long; it may
37635 not fit in a 32-bit word.
37637 @item M @var{basereg},@var{offset},@var{len}
37638 Collect @var{len} bytes of memory starting at the address in register
37639 number @var{basereg}, plus @var{offset}. If @var{basereg} is
37640 @samp{-1}, then the range has a fixed address: @var{offset} is the
37641 address of the lowest byte to collect. The @var{basereg},
37642 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
37643 values (the @samp{-1} value for @var{basereg} is a special case).
37645 @item X @var{len},@var{expr}
37646 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
37647 it directs. The agent expression @var{expr} is as described in
37648 @ref{Agent Expressions}. Each byte of the expression is encoded as a
37649 two-digit hex number in the packet; @var{len} is the number of bytes
37650 in the expression (and thus one-half the number of hex digits in the
37655 Any number of actions may be packed together in a single @samp{QTDP}
37656 packet, as long as the packet does not exceed the maximum packet
37657 length (400 bytes, for many stubs). There may be only one @samp{R}
37658 action per tracepoint, and it must precede any @samp{M} or @samp{X}
37659 actions. Any registers referred to by @samp{M} and @samp{X} actions
37660 must be collected by a preceding @samp{R} action. (The
37661 ``while-stepping'' actions are treated as if they were attached to a
37662 separate tracepoint, as far as these restrictions are concerned.)
37667 The packet was understood and carried out.
37669 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
37671 The packet was not recognized.
37674 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
37675 @cindex @samp{QTDPsrc} packet
37676 Specify a source string of tracepoint @var{n} at address @var{addr}.
37677 This is useful to get accurate reproduction of the tracepoints
37678 originally downloaded at the beginning of the trace run. The @var{type}
37679 is the name of the tracepoint part, such as @samp{cond} for the
37680 tracepoint's conditional expression (see below for a list of types), while
37681 @var{bytes} is the string, encoded in hexadecimal.
37683 @var{start} is the offset of the @var{bytes} within the overall source
37684 string, while @var{slen} is the total length of the source string.
37685 This is intended for handling source strings that are longer than will
37686 fit in a single packet.
37687 @c Add detailed example when this info is moved into a dedicated
37688 @c tracepoint descriptions section.
37690 The available string types are @samp{at} for the location,
37691 @samp{cond} for the conditional, and @samp{cmd} for an action command.
37692 @value{GDBN} sends a separate packet for each command in the action
37693 list, in the same order in which the commands are stored in the list.
37695 The target does not need to do anything with source strings except
37696 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
37699 Although this packet is optional, and @value{GDBN} will only send it
37700 if the target replies with @samp{TracepointSource} @xref{General
37701 Query Packets}, it makes both disconnected tracing and trace files
37702 much easier to use. Otherwise the user must be careful that the
37703 tracepoints in effect while looking at trace frames are identical to
37704 the ones in effect during the trace run; even a small discrepancy
37705 could cause @samp{tdump} not to work, or a particular trace frame not
37708 @item QTDV:@var{n}:@var{value}:@var{builtin}:@var{name}
37709 @cindex define trace state variable, remote request
37710 @cindex @samp{QTDV} packet
37711 Create a new trace state variable, number @var{n}, with an initial
37712 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
37713 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
37714 the option of not using this packet for initial values of zero; the
37715 target should simply create the trace state variables as they are
37716 mentioned in expressions. The value @var{builtin} should be 1 (one)
37717 if the trace state variable is builtin and 0 (zero) if it is not builtin.
37718 @value{GDBN} only sets @var{builtin} to 1 if a previous @samp{qTfV} or
37719 @samp{qTsV} packet had it set. The contents of @var{name} is the
37720 hex-encoded name (without the leading @samp{$}) of the trace state
37723 @item QTFrame:@var{n}
37724 @cindex @samp{QTFrame} packet
37725 Select the @var{n}'th tracepoint frame from the buffer, and use the
37726 register and memory contents recorded there to answer subsequent
37727 request packets from @value{GDBN}.
37729 A successful reply from the stub indicates that the stub has found the
37730 requested frame. The response is a series of parts, concatenated
37731 without separators, describing the frame we selected. Each part has
37732 one of the following forms:
37736 The selected frame is number @var{n} in the trace frame buffer;
37737 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
37738 was no frame matching the criteria in the request packet.
37741 The selected trace frame records a hit of tracepoint number @var{t};
37742 @var{t} is a hexadecimal number.
37746 @item QTFrame:pc:@var{addr}
37747 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37748 currently selected frame whose PC is @var{addr};
37749 @var{addr} is a hexadecimal number.
37751 @item QTFrame:tdp:@var{t}
37752 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37753 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
37754 is a hexadecimal number.
37756 @item QTFrame:range:@var{start}:@var{end}
37757 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
37758 currently selected frame whose PC is between @var{start} (inclusive)
37759 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
37762 @item QTFrame:outside:@var{start}:@var{end}
37763 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
37764 frame @emph{outside} the given range of addresses (exclusive).
37767 @cindex @samp{qTMinFTPILen} packet
37768 This packet requests the minimum length of instruction at which a fast
37769 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
37770 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
37771 it depends on the target system being able to create trampolines in
37772 the first 64K of memory, which might or might not be possible for that
37773 system. So the reply to this packet will be 4 if it is able to
37780 The minimum instruction length is currently unknown.
37782 The minimum instruction length is @var{length}, where @var{length}
37783 is a hexadecimal number greater or equal to 1. A reply
37784 of 1 means that a fast tracepoint may be placed on any instruction
37785 regardless of size.
37787 An error has occurred.
37789 An empty reply indicates that the request is not supported by the stub.
37793 @cindex @samp{QTStart} packet
37794 Begin the tracepoint experiment. Begin collecting data from
37795 tracepoint hits in the trace frame buffer. This packet supports the
37796 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
37797 instruction reply packet}).
37800 @cindex @samp{QTStop} packet
37801 End the tracepoint experiment. Stop collecting trace frames.
37803 @item QTEnable:@var{n}:@var{addr}
37805 @cindex @samp{QTEnable} packet
37806 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
37807 experiment. If the tracepoint was previously disabled, then collection
37808 of data from it will resume.
37810 @item QTDisable:@var{n}:@var{addr}
37812 @cindex @samp{QTDisable} packet
37813 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
37814 experiment. No more data will be collected from the tracepoint unless
37815 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
37818 @cindex @samp{QTinit} packet
37819 Clear the table of tracepoints, and empty the trace frame buffer.
37821 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
37822 @cindex @samp{QTro} packet
37823 Establish the given ranges of memory as ``transparent''. The stub
37824 will answer requests for these ranges from memory's current contents,
37825 if they were not collected as part of the tracepoint hit.
37827 @value{GDBN} uses this to mark read-only regions of memory, like those
37828 containing program code. Since these areas never change, they should
37829 still have the same contents they did when the tracepoint was hit, so
37830 there's no reason for the stub to refuse to provide their contents.
37832 @item QTDisconnected:@var{value}
37833 @cindex @samp{QTDisconnected} packet
37834 Set the choice to what to do with the tracing run when @value{GDBN}
37835 disconnects from the target. A @var{value} of 1 directs the target to
37836 continue the tracing run, while 0 tells the target to stop tracing if
37837 @value{GDBN} is no longer in the picture.
37840 @cindex @samp{qTStatus} packet
37841 Ask the stub if there is a trace experiment running right now.
37843 The reply has the form:
37847 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
37848 @var{running} is a single digit @code{1} if the trace is presently
37849 running, or @code{0} if not. It is followed by semicolon-separated
37850 optional fields that an agent may use to report additional status.
37854 If the trace is not running, the agent may report any of several
37855 explanations as one of the optional fields:
37860 No trace has been run yet.
37862 @item tstop[:@var{text}]:0
37863 The trace was stopped by a user-originated stop command. The optional
37864 @var{text} field is a user-supplied string supplied as part of the
37865 stop command (for instance, an explanation of why the trace was
37866 stopped manually). It is hex-encoded.
37869 The trace stopped because the trace buffer filled up.
37871 @item tdisconnected:0
37872 The trace stopped because @value{GDBN} disconnected from the target.
37874 @item tpasscount:@var{tpnum}
37875 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
37877 @item terror:@var{text}:@var{tpnum}
37878 The trace stopped because tracepoint @var{tpnum} had an error. The
37879 string @var{text} is available to describe the nature of the error
37880 (for instance, a divide by zero in the condition expression); it
37884 The trace stopped for some other reason.
37888 Additional optional fields supply statistical and other information.
37889 Although not required, they are extremely useful for users monitoring
37890 the progress of a trace run. If a trace has stopped, and these
37891 numbers are reported, they must reflect the state of the just-stopped
37896 @item tframes:@var{n}
37897 The number of trace frames in the buffer.
37899 @item tcreated:@var{n}
37900 The total number of trace frames created during the run. This may
37901 be larger than the trace frame count, if the buffer is circular.
37903 @item tsize:@var{n}
37904 The total size of the trace buffer, in bytes.
37906 @item tfree:@var{n}
37907 The number of bytes still unused in the buffer.
37909 @item circular:@var{n}
37910 The value of the circular trace buffer flag. @code{1} means that the
37911 trace buffer is circular and old trace frames will be discarded if
37912 necessary to make room, @code{0} means that the trace buffer is linear
37915 @item disconn:@var{n}
37916 The value of the disconnected tracing flag. @code{1} means that
37917 tracing will continue after @value{GDBN} disconnects, @code{0} means
37918 that the trace run will stop.
37922 @item qTP:@var{tp}:@var{addr}
37923 @cindex tracepoint status, remote request
37924 @cindex @samp{qTP} packet
37925 Ask the stub for the current state of tracepoint number @var{tp} at
37926 address @var{addr}.
37930 @item V@var{hits}:@var{usage}
37931 The tracepoint has been hit @var{hits} times so far during the trace
37932 run, and accounts for @var{usage} in the trace buffer. Note that
37933 @code{while-stepping} steps are not counted as separate hits, but the
37934 steps' space consumption is added into the usage number.
37938 @item qTV:@var{var}
37939 @cindex trace state variable value, remote request
37940 @cindex @samp{qTV} packet
37941 Ask the stub for the value of the trace state variable number @var{var}.
37946 The value of the variable is @var{value}. This will be the current
37947 value of the variable if the user is examining a running target, or a
37948 saved value if the variable was collected in the trace frame that the
37949 user is looking at. Note that multiple requests may result in
37950 different reply values, such as when requesting values while the
37951 program is running.
37954 The value of the variable is unknown. This would occur, for example,
37955 if the user is examining a trace frame in which the requested variable
37960 @cindex @samp{qTfP} packet
37962 @cindex @samp{qTsP} packet
37963 These packets request data about tracepoints that are being used by
37964 the target. @value{GDBN} sends @code{qTfP} to get the first piece
37965 of data, and multiple @code{qTsP} to get additional pieces. Replies
37966 to these packets generally take the form of the @code{QTDP} packets
37967 that define tracepoints. (FIXME add detailed syntax)
37970 @cindex @samp{qTfV} packet
37972 @cindex @samp{qTsV} packet
37973 These packets request data about trace state variables that are on the
37974 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
37975 and multiple @code{qTsV} to get additional variables. Replies to
37976 these packets follow the syntax of the @code{QTDV} packets that define
37977 trace state variables.
37983 @cindex @samp{qTfSTM} packet
37984 @cindex @samp{qTsSTM} packet
37985 These packets request data about static tracepoint markers that exist
37986 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
37987 first piece of data, and multiple @code{qTsSTM} to get additional
37988 pieces. Replies to these packets take the following form:
37992 @item m @var{address}:@var{id}:@var{extra}
37994 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
37995 a comma-separated list of markers
37997 (lower case letter @samp{L}) denotes end of list.
37999 An error occurred. The error number @var{nn} is given as hex digits.
38001 An empty reply indicates that the request is not supported by the
38005 The @var{address} is encoded in hex;
38006 @var{id} and @var{extra} are strings encoded in hex.
38008 In response to each query, the target will reply with a list of one or
38009 more markers, separated by commas. @value{GDBN} will respond to each
38010 reply with a request for more markers (using the @samp{qs} form of the
38011 query), until the target responds with @samp{l} (lower-case ell, for
38014 @item qTSTMat:@var{address}
38016 @cindex @samp{qTSTMat} packet
38017 This packets requests data about static tracepoint markers in the
38018 target program at @var{address}. Replies to this packet follow the
38019 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38020 tracepoint markers.
38022 @item QTSave:@var{filename}
38023 @cindex @samp{QTSave} packet
38024 This packet directs the target to save trace data to the file name
38025 @var{filename} in the target's filesystem. The @var{filename} is encoded
38026 as a hex string; the interpretation of the file name (relative vs
38027 absolute, wild cards, etc) is up to the target.
38029 @item qTBuffer:@var{offset},@var{len}
38030 @cindex @samp{qTBuffer} packet
38031 Return up to @var{len} bytes of the current contents of trace buffer,
38032 starting at @var{offset}. The trace buffer is treated as if it were
38033 a contiguous collection of traceframes, as per the trace file format.
38034 The reply consists as many hex-encoded bytes as the target can deliver
38035 in a packet; it is not an error to return fewer than were asked for.
38036 A reply consisting of just @code{l} indicates that no bytes are
38039 @item QTBuffer:circular:@var{value}
38040 This packet directs the target to use a circular trace buffer if
38041 @var{value} is 1, or a linear buffer if the value is 0.
38043 @item QTBuffer:size:@var{size}
38044 @anchor{QTBuffer-size}
38045 @cindex @samp{QTBuffer size} packet
38046 This packet directs the target to make the trace buffer be of size
38047 @var{size} if possible. A value of @code{-1} tells the target to
38048 use whatever size it prefers.
38050 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38051 @cindex @samp{QTNotes} packet
38052 This packet adds optional textual notes to the trace run. Allowable
38053 types include @code{user}, @code{notes}, and @code{tstop}, the
38054 @var{text} fields are arbitrary strings, hex-encoded.
38058 @subsection Relocate instruction reply packet
38059 When installing fast tracepoints in memory, the target may need to
38060 relocate the instruction currently at the tracepoint address to a
38061 different address in memory. For most instructions, a simple copy is
38062 enough, but, for example, call instructions that implicitly push the
38063 return address on the stack, and relative branches or other
38064 PC-relative instructions require offset adjustment, so that the effect
38065 of executing the instruction at a different address is the same as if
38066 it had executed in the original location.
38068 In response to several of the tracepoint packets, the target may also
38069 respond with a number of intermediate @samp{qRelocInsn} request
38070 packets before the final result packet, to have @value{GDBN} handle
38071 this relocation operation. If a packet supports this mechanism, its
38072 documentation will explicitly say so. See for example the above
38073 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38074 format of the request is:
38077 @item qRelocInsn:@var{from};@var{to}
38079 This requests @value{GDBN} to copy instruction at address @var{from}
38080 to address @var{to}, possibly adjusted so that executing the
38081 instruction at @var{to} has the same effect as executing it at
38082 @var{from}. @value{GDBN} writes the adjusted instruction to target
38083 memory starting at @var{to}.
38088 @item qRelocInsn:@var{adjusted_size}
38089 Informs the stub the relocation is complete. The @var{adjusted_size} is
38090 the length in bytes of resulting relocated instruction sequence.
38092 A badly formed request was detected, or an error was encountered while
38093 relocating the instruction.
38096 @node Host I/O Packets
38097 @section Host I/O Packets
38098 @cindex Host I/O, remote protocol
38099 @cindex file transfer, remote protocol
38101 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38102 operations on the far side of a remote link. For example, Host I/O is
38103 used to upload and download files to a remote target with its own
38104 filesystem. Host I/O uses the same constant values and data structure
38105 layout as the target-initiated File-I/O protocol. However, the
38106 Host I/O packets are structured differently. The target-initiated
38107 protocol relies on target memory to store parameters and buffers.
38108 Host I/O requests are initiated by @value{GDBN}, and the
38109 target's memory is not involved. @xref{File-I/O Remote Protocol
38110 Extension}, for more details on the target-initiated protocol.
38112 The Host I/O request packets all encode a single operation along with
38113 its arguments. They have this format:
38117 @item vFile:@var{operation}: @var{parameter}@dots{}
38118 @var{operation} is the name of the particular request; the target
38119 should compare the entire packet name up to the second colon when checking
38120 for a supported operation. The format of @var{parameter} depends on
38121 the operation. Numbers are always passed in hexadecimal. Negative
38122 numbers have an explicit minus sign (i.e.@: two's complement is not
38123 used). Strings (e.g.@: filenames) are encoded as a series of
38124 hexadecimal bytes. The last argument to a system call may be a
38125 buffer of escaped binary data (@pxref{Binary Data}).
38129 The valid responses to Host I/O packets are:
38133 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38134 @var{result} is the integer value returned by this operation, usually
38135 non-negative for success and -1 for errors. If an error has occured,
38136 @var{errno} will be included in the result specifying a
38137 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38138 operations which return data, @var{attachment} supplies the data as a
38139 binary buffer. Binary buffers in response packets are escaped in the
38140 normal way (@pxref{Binary Data}). See the individual packet
38141 documentation for the interpretation of @var{result} and
38145 An empty response indicates that this operation is not recognized.
38149 These are the supported Host I/O operations:
38152 @item vFile:open: @var{filename}, @var{flags}, @var{mode}
38153 Open a file at @var{filename} and return a file descriptor for it, or
38154 return -1 if an error occurs. The @var{filename} is a string,
38155 @var{flags} is an integer indicating a mask of open flags
38156 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38157 of mode bits to use if the file is created (@pxref{mode_t Values}).
38158 @xref{open}, for details of the open flags and mode values.
38160 @item vFile:close: @var{fd}
38161 Close the open file corresponding to @var{fd} and return 0, or
38162 -1 if an error occurs.
38164 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38165 Read data from the open file corresponding to @var{fd}. Up to
38166 @var{count} bytes will be read from the file, starting at @var{offset}
38167 relative to the start of the file. The target may read fewer bytes;
38168 common reasons include packet size limits and an end-of-file
38169 condition. The number of bytes read is returned. Zero should only be
38170 returned for a successful read at the end of the file, or if
38171 @var{count} was zero.
38173 The data read should be returned as a binary attachment on success.
38174 If zero bytes were read, the response should include an empty binary
38175 attachment (i.e.@: a trailing semicolon). The return value is the
38176 number of target bytes read; the binary attachment may be longer if
38177 some characters were escaped.
38179 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38180 Write @var{data} (a binary buffer) to the open file corresponding
38181 to @var{fd}. Start the write at @var{offset} from the start of the
38182 file. Unlike many @code{write} system calls, there is no
38183 separate @var{count} argument; the length of @var{data} in the
38184 packet is used. @samp{vFile:write} returns the number of bytes written,
38185 which may be shorter than the length of @var{data}, or -1 if an
38188 @item vFile:fstat: @var{fd}
38189 Get information about the open file corresponding to @var{fd}.
38190 On success the information is returned as a binary attachment
38191 and the return value is the size of this attachment in bytes.
38192 If an error occurs the return value is -1. The format of the
38193 returned binary attachment is as described in @ref{struct stat}.
38195 @item vFile:unlink: @var{filename}
38196 Delete the file at @var{filename} on the target. Return 0,
38197 or -1 if an error occurs. The @var{filename} is a string.
38199 @item vFile:readlink: @var{filename}
38200 Read value of symbolic link @var{filename} on the target. Return
38201 the number of bytes read, or -1 if an error occurs.
38203 The data read should be returned as a binary attachment on success.
38204 If zero bytes were read, the response should include an empty binary
38205 attachment (i.e.@: a trailing semicolon). The return value is the
38206 number of target bytes read; the binary attachment may be longer if
38207 some characters were escaped.
38209 @item vFile:setfs: @var{pid}
38210 Select the filesystem on which @code{vFile} operations with
38211 @var{filename} arguments will operate. This is required for
38212 @value{GDBN} to be able to access files on remote targets where
38213 the remote stub does not share a common filesystem with the
38216 If @var{pid} is nonzero, select the filesystem as seen by process
38217 @var{pid}. If @var{pid} is zero, select the filesystem as seen by
38218 the remote stub. Return 0 on success, or -1 if an error occurs.
38219 If @code{vFile:setfs:} indicates success, the selected filesystem
38220 remains selected until the next successful @code{vFile:setfs:}
38226 @section Interrupts
38227 @cindex interrupts (remote protocol)
38228 @anchor{interrupting remote targets}
38230 In all-stop mode, when a program on the remote target is running,
38231 @value{GDBN} may attempt to interrupt it by sending a @samp{Ctrl-C},
38232 @code{BREAK} or a @code{BREAK} followed by @code{g}, control of which
38233 is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38235 The precise meaning of @code{BREAK} is defined by the transport
38236 mechanism and may, in fact, be undefined. @value{GDBN} does not
38237 currently define a @code{BREAK} mechanism for any of the network
38238 interfaces except for TCP, in which case @value{GDBN} sends the
38239 @code{telnet} BREAK sequence.
38241 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38242 transport mechanisms. It is represented by sending the single byte
38243 @code{0x03} without any of the usual packet overhead described in
38244 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38245 transmitted as part of a packet, it is considered to be packet data
38246 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38247 (@pxref{X packet}), used for binary downloads, may include an unescaped
38248 @code{0x03} as part of its packet.
38250 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38251 When Linux kernel receives this sequence from serial port,
38252 it stops execution and connects to gdb.
38254 In non-stop mode, because packet resumptions are asynchronous
38255 (@pxref{vCont packet}), @value{GDBN} is always free to send a remote
38256 command to the remote stub, even when the target is running. For that
38257 reason, @value{GDBN} instead sends a regular packet (@pxref{vCtrlC
38258 packet}) with the usual packet framing instead of the single byte
38261 Stubs are not required to recognize these interrupt mechanisms and the
38262 precise meaning associated with receipt of the interrupt is
38263 implementation defined. If the target supports debugging of multiple
38264 threads and/or processes, it should attempt to interrupt all
38265 currently-executing threads and processes.
38266 If the stub is successful at interrupting the
38267 running program, it should send one of the stop
38268 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38269 of successfully stopping the program in all-stop mode, and a stop reply
38270 for each stopped thread in non-stop mode.
38271 Interrupts received while the
38272 program is stopped are queued and the program will be interrupted when
38273 it is resumed next time.
38275 @node Notification Packets
38276 @section Notification Packets
38277 @cindex notification packets
38278 @cindex packets, notification
38280 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38281 packets that require no acknowledgment. Both the GDB and the stub
38282 may send notifications (although the only notifications defined at
38283 present are sent by the stub). Notifications carry information
38284 without incurring the round-trip latency of an acknowledgment, and so
38285 are useful for low-impact communications where occasional packet loss
38288 A notification packet has the form @samp{% @var{data} #
38289 @var{checksum}}, where @var{data} is the content of the notification,
38290 and @var{checksum} is a checksum of @var{data}, computed and formatted
38291 as for ordinary @value{GDBN} packets. A notification's @var{data}
38292 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38293 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38294 to acknowledge the notification's receipt or to report its corruption.
38296 Every notification's @var{data} begins with a name, which contains no
38297 colon characters, followed by a colon character.
38299 Recipients should silently ignore corrupted notifications and
38300 notifications they do not understand. Recipients should restart
38301 timeout periods on receipt of a well-formed notification, whether or
38302 not they understand it.
38304 Senders should only send the notifications described here when this
38305 protocol description specifies that they are permitted. In the
38306 future, we may extend the protocol to permit existing notifications in
38307 new contexts; this rule helps older senders avoid confusing newer
38310 (Older versions of @value{GDBN} ignore bytes received until they see
38311 the @samp{$} byte that begins an ordinary packet, so new stubs may
38312 transmit notifications without fear of confusing older clients. There
38313 are no notifications defined for @value{GDBN} to send at the moment, but we
38314 assume that most older stubs would ignore them, as well.)
38316 Each notification is comprised of three parts:
38318 @item @var{name}:@var{event}
38319 The notification packet is sent by the side that initiates the
38320 exchange (currently, only the stub does that), with @var{event}
38321 carrying the specific information about the notification, and
38322 @var{name} specifying the name of the notification.
38324 The acknowledge sent by the other side, usually @value{GDBN}, to
38325 acknowledge the exchange and request the event.
38328 The purpose of an asynchronous notification mechanism is to report to
38329 @value{GDBN} that something interesting happened in the remote stub.
38331 The remote stub may send notification @var{name}:@var{event}
38332 at any time, but @value{GDBN} acknowledges the notification when
38333 appropriate. The notification event is pending before @value{GDBN}
38334 acknowledges. Only one notification at a time may be pending; if
38335 additional events occur before @value{GDBN} has acknowledged the
38336 previous notification, they must be queued by the stub for later
38337 synchronous transmission in response to @var{ack} packets from
38338 @value{GDBN}. Because the notification mechanism is unreliable,
38339 the stub is permitted to resend a notification if it believes
38340 @value{GDBN} may not have received it.
38342 Specifically, notifications may appear when @value{GDBN} is not
38343 otherwise reading input from the stub, or when @value{GDBN} is
38344 expecting to read a normal synchronous response or a
38345 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38346 Notification packets are distinct from any other communication from
38347 the stub so there is no ambiguity.
38349 After receiving a notification, @value{GDBN} shall acknowledge it by
38350 sending a @var{ack} packet as a regular, synchronous request to the
38351 stub. Such acknowledgment is not required to happen immediately, as
38352 @value{GDBN} is permitted to send other, unrelated packets to the
38353 stub first, which the stub should process normally.
38355 Upon receiving a @var{ack} packet, if the stub has other queued
38356 events to report to @value{GDBN}, it shall respond by sending a
38357 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38358 packet to solicit further responses; again, it is permitted to send
38359 other, unrelated packets as well which the stub should process
38362 If the stub receives a @var{ack} packet and there are no additional
38363 @var{event} to report, the stub shall return an @samp{OK} response.
38364 At this point, @value{GDBN} has finished processing a notification
38365 and the stub has completed sending any queued events. @value{GDBN}
38366 won't accept any new notifications until the final @samp{OK} is
38367 received . If further notification events occur, the stub shall send
38368 a new notification, @value{GDBN} shall accept the notification, and
38369 the process shall be repeated.
38371 The process of asynchronous notification can be illustrated by the
38374 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38377 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38379 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38384 The following notifications are defined:
38385 @multitable @columnfractions 0.12 0.12 0.38 0.38
38394 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38395 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38396 for information on how these notifications are acknowledged by
38398 @tab Report an asynchronous stop event in non-stop mode.
38402 @node Remote Non-Stop
38403 @section Remote Protocol Support for Non-Stop Mode
38405 @value{GDBN}'s remote protocol supports non-stop debugging of
38406 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38407 supports non-stop mode, it should report that to @value{GDBN} by including
38408 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38410 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38411 establishing a new connection with the stub. Entering non-stop mode
38412 does not alter the state of any currently-running threads, but targets
38413 must stop all threads in any already-attached processes when entering
38414 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38415 probe the target state after a mode change.
38417 In non-stop mode, when an attached process encounters an event that
38418 would otherwise be reported with a stop reply, it uses the
38419 asynchronous notification mechanism (@pxref{Notification Packets}) to
38420 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38421 in all processes are stopped when a stop reply is sent, in non-stop
38422 mode only the thread reporting the stop event is stopped. That is,
38423 when reporting a @samp{S} or @samp{T} response to indicate completion
38424 of a step operation, hitting a breakpoint, or a fault, only the
38425 affected thread is stopped; any other still-running threads continue
38426 to run. When reporting a @samp{W} or @samp{X} response, all running
38427 threads belonging to other attached processes continue to run.
38429 In non-stop mode, the target shall respond to the @samp{?} packet as
38430 follows. First, any incomplete stop reply notification/@samp{vStopped}
38431 sequence in progress is abandoned. The target must begin a new
38432 sequence reporting stop events for all stopped threads, whether or not
38433 it has previously reported those events to @value{GDBN}. The first
38434 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38435 subsequent stop replies are sent as responses to @samp{vStopped} packets
38436 using the mechanism described above. The target must not send
38437 asynchronous stop reply notifications until the sequence is complete.
38438 If all threads are running when the target receives the @samp{?} packet,
38439 or if the target is not attached to any process, it shall respond
38442 If the stub supports non-stop mode, it should also support the
38443 @samp{swbreak} stop reason if software breakpoints are supported, and
38444 the @samp{hwbreak} stop reason if hardware breakpoints are supported
38445 (@pxref{swbreak stop reason}). This is because given the asynchronous
38446 nature of non-stop mode, between the time a thread hits a breakpoint
38447 and the time the event is finally processed by @value{GDBN}, the
38448 breakpoint may have already been removed from the target. Due to
38449 this, @value{GDBN} needs to be able to tell whether a trap stop was
38450 caused by a delayed breakpoint event, which should be ignored, as
38451 opposed to a random trap signal, which should be reported to the user.
38452 Note the @samp{swbreak} feature implies that the target is responsible
38453 for adjusting the PC when a software breakpoint triggers, if
38454 necessary, such as on the x86 architecture.
38456 @node Packet Acknowledgment
38457 @section Packet Acknowledgment
38459 @cindex acknowledgment, for @value{GDBN} remote
38460 @cindex packet acknowledgment, for @value{GDBN} remote
38461 By default, when either the host or the target machine receives a packet,
38462 the first response expected is an acknowledgment: either @samp{+} (to indicate
38463 the package was received correctly) or @samp{-} (to request retransmission).
38464 This mechanism allows the @value{GDBN} remote protocol to operate over
38465 unreliable transport mechanisms, such as a serial line.
38467 In cases where the transport mechanism is itself reliable (such as a pipe or
38468 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38469 It may be desirable to disable them in that case to reduce communication
38470 overhead, or for other reasons. This can be accomplished by means of the
38471 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38473 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38474 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38475 and response format still includes the normal checksum, as described in
38476 @ref{Overview}, but the checksum may be ignored by the receiver.
38478 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38479 no-acknowledgment mode, it should report that to @value{GDBN}
38480 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38481 @pxref{qSupported}.
38482 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38483 disabled via the @code{set remote noack-packet off} command
38484 (@pxref{Remote Configuration}),
38485 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38486 Only then may the stub actually turn off packet acknowledgments.
38487 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38488 response, which can be safely ignored by the stub.
38490 Note that @code{set remote noack-packet} command only affects negotiation
38491 between @value{GDBN} and the stub when subsequent connections are made;
38492 it does not affect the protocol acknowledgment state for any current
38494 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38495 new connection is established,
38496 there is also no protocol request to re-enable the acknowledgments
38497 for the current connection, once disabled.
38502 Example sequence of a target being re-started. Notice how the restart
38503 does not get any direct output:
38508 @emph{target restarts}
38511 <- @code{T001:1234123412341234}
38515 Example sequence of a target being stepped by a single instruction:
38518 -> @code{G1445@dots{}}
38523 <- @code{T001:1234123412341234}
38527 <- @code{1455@dots{}}
38531 @node File-I/O Remote Protocol Extension
38532 @section File-I/O Remote Protocol Extension
38533 @cindex File-I/O remote protocol extension
38536 * File-I/O Overview::
38537 * Protocol Basics::
38538 * The F Request Packet::
38539 * The F Reply Packet::
38540 * The Ctrl-C Message::
38542 * List of Supported Calls::
38543 * Protocol-specific Representation of Datatypes::
38545 * File-I/O Examples::
38548 @node File-I/O Overview
38549 @subsection File-I/O Overview
38550 @cindex file-i/o overview
38552 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38553 target to use the host's file system and console I/O to perform various
38554 system calls. System calls on the target system are translated into a
38555 remote protocol packet to the host system, which then performs the needed
38556 actions and returns a response packet to the target system.
38557 This simulates file system operations even on targets that lack file systems.
38559 The protocol is defined to be independent of both the host and target systems.
38560 It uses its own internal representation of datatypes and values. Both
38561 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38562 translating the system-dependent value representations into the internal
38563 protocol representations when data is transmitted.
38565 The communication is synchronous. A system call is possible only when
38566 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38567 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38568 the target is stopped to allow deterministic access to the target's
38569 memory. Therefore File-I/O is not interruptible by target signals. On
38570 the other hand, it is possible to interrupt File-I/O by a user interrupt
38571 (@samp{Ctrl-C}) within @value{GDBN}.
38573 The target's request to perform a host system call does not finish
38574 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38575 after finishing the system call, the target returns to continuing the
38576 previous activity (continue, step). No additional continue or step
38577 request from @value{GDBN} is required.
38580 (@value{GDBP}) continue
38581 <- target requests 'system call X'
38582 target is stopped, @value{GDBN} executes system call
38583 -> @value{GDBN} returns result
38584 ... target continues, @value{GDBN} returns to wait for the target
38585 <- target hits breakpoint and sends a Txx packet
38588 The protocol only supports I/O on the console and to regular files on
38589 the host file system. Character or block special devices, pipes,
38590 named pipes, sockets or any other communication method on the host
38591 system are not supported by this protocol.
38593 File I/O is not supported in non-stop mode.
38595 @node Protocol Basics
38596 @subsection Protocol Basics
38597 @cindex protocol basics, file-i/o
38599 The File-I/O protocol uses the @code{F} packet as the request as well
38600 as reply packet. Since a File-I/O system call can only occur when
38601 @value{GDBN} is waiting for a response from the continuing or stepping target,
38602 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38603 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38604 This @code{F} packet contains all information needed to allow @value{GDBN}
38605 to call the appropriate host system call:
38609 A unique identifier for the requested system call.
38612 All parameters to the system call. Pointers are given as addresses
38613 in the target memory address space. Pointers to strings are given as
38614 pointer/length pair. Numerical values are given as they are.
38615 Numerical control flags are given in a protocol-specific representation.
38619 At this point, @value{GDBN} has to perform the following actions.
38623 If the parameters include pointer values to data needed as input to a
38624 system call, @value{GDBN} requests this data from the target with a
38625 standard @code{m} packet request. This additional communication has to be
38626 expected by the target implementation and is handled as any other @code{m}
38630 @value{GDBN} translates all value from protocol representation to host
38631 representation as needed. Datatypes are coerced into the host types.
38634 @value{GDBN} calls the system call.
38637 It then coerces datatypes back to protocol representation.
38640 If the system call is expected to return data in buffer space specified
38641 by pointer parameters to the call, the data is transmitted to the
38642 target using a @code{M} or @code{X} packet. This packet has to be expected
38643 by the target implementation and is handled as any other @code{M} or @code{X}
38648 Eventually @value{GDBN} replies with another @code{F} packet which contains all
38649 necessary information for the target to continue. This at least contains
38656 @code{errno}, if has been changed by the system call.
38663 After having done the needed type and value coercion, the target continues
38664 the latest continue or step action.
38666 @node The F Request Packet
38667 @subsection The @code{F} Request Packet
38668 @cindex file-i/o request packet
38669 @cindex @code{F} request packet
38671 The @code{F} request packet has the following format:
38674 @item F@var{call-id},@var{parameter@dots{}}
38676 @var{call-id} is the identifier to indicate the host system call to be called.
38677 This is just the name of the function.
38679 @var{parameter@dots{}} are the parameters to the system call.
38680 Parameters are hexadecimal integer values, either the actual values in case
38681 of scalar datatypes, pointers to target buffer space in case of compound
38682 datatypes and unspecified memory areas, or pointer/length pairs in case
38683 of string parameters. These are appended to the @var{call-id} as a
38684 comma-delimited list. All values are transmitted in ASCII
38685 string representation, pointer/length pairs separated by a slash.
38691 @node The F Reply Packet
38692 @subsection The @code{F} Reply Packet
38693 @cindex file-i/o reply packet
38694 @cindex @code{F} reply packet
38696 The @code{F} reply packet has the following format:
38700 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
38702 @var{retcode} is the return code of the system call as hexadecimal value.
38704 @var{errno} is the @code{errno} set by the call, in protocol-specific
38706 This parameter can be omitted if the call was successful.
38708 @var{Ctrl-C flag} is only sent if the user requested a break. In this
38709 case, @var{errno} must be sent as well, even if the call was successful.
38710 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
38717 or, if the call was interrupted before the host call has been performed:
38724 assuming 4 is the protocol-specific representation of @code{EINTR}.
38729 @node The Ctrl-C Message
38730 @subsection The @samp{Ctrl-C} Message
38731 @cindex ctrl-c message, in file-i/o protocol
38733 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
38734 reply packet (@pxref{The F Reply Packet}),
38735 the target should behave as if it had
38736 gotten a break message. The meaning for the target is ``system call
38737 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
38738 (as with a break message) and return to @value{GDBN} with a @code{T02}
38741 It's important for the target to know in which
38742 state the system call was interrupted. There are two possible cases:
38746 The system call hasn't been performed on the host yet.
38749 The system call on the host has been finished.
38753 These two states can be distinguished by the target by the value of the
38754 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
38755 call hasn't been performed. This is equivalent to the @code{EINTR} handling
38756 on POSIX systems. In any other case, the target may presume that the
38757 system call has been finished --- successfully or not --- and should behave
38758 as if the break message arrived right after the system call.
38760 @value{GDBN} must behave reliably. If the system call has not been called
38761 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
38762 @code{errno} in the packet. If the system call on the host has been finished
38763 before the user requests a break, the full action must be finished by
38764 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
38765 The @code{F} packet may only be sent when either nothing has happened
38766 or the full action has been completed.
38769 @subsection Console I/O
38770 @cindex console i/o as part of file-i/o
38772 By default and if not explicitly closed by the target system, the file
38773 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
38774 on the @value{GDBN} console is handled as any other file output operation
38775 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
38776 by @value{GDBN} so that after the target read request from file descriptor
38777 0 all following typing is buffered until either one of the following
38782 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
38784 system call is treated as finished.
38787 The user presses @key{RET}. This is treated as end of input with a trailing
38791 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
38792 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
38796 If the user has typed more characters than fit in the buffer given to
38797 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
38798 either another @code{read(0, @dots{})} is requested by the target, or debugging
38799 is stopped at the user's request.
38802 @node List of Supported Calls
38803 @subsection List of Supported Calls
38804 @cindex list of supported file-i/o calls
38821 @unnumberedsubsubsec open
38822 @cindex open, file-i/o system call
38827 int open(const char *pathname, int flags);
38828 int open(const char *pathname, int flags, mode_t mode);
38832 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
38835 @var{flags} is the bitwise @code{OR} of the following values:
38839 If the file does not exist it will be created. The host
38840 rules apply as far as file ownership and time stamps
38844 When used with @code{O_CREAT}, if the file already exists it is
38845 an error and open() fails.
38848 If the file already exists and the open mode allows
38849 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
38850 truncated to zero length.
38853 The file is opened in append mode.
38856 The file is opened for reading only.
38859 The file is opened for writing only.
38862 The file is opened for reading and writing.
38866 Other bits are silently ignored.
38870 @var{mode} is the bitwise @code{OR} of the following values:
38874 User has read permission.
38877 User has write permission.
38880 Group has read permission.
38883 Group has write permission.
38886 Others have read permission.
38889 Others have write permission.
38893 Other bits are silently ignored.
38896 @item Return value:
38897 @code{open} returns the new file descriptor or -1 if an error
38904 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
38907 @var{pathname} refers to a directory.
38910 The requested access is not allowed.
38913 @var{pathname} was too long.
38916 A directory component in @var{pathname} does not exist.
38919 @var{pathname} refers to a device, pipe, named pipe or socket.
38922 @var{pathname} refers to a file on a read-only filesystem and
38923 write access was requested.
38926 @var{pathname} is an invalid pointer value.
38929 No space on device to create the file.
38932 The process already has the maximum number of files open.
38935 The limit on the total number of files open on the system
38939 The call was interrupted by the user.
38945 @unnumberedsubsubsec close
38946 @cindex close, file-i/o system call
38955 @samp{Fclose,@var{fd}}
38957 @item Return value:
38958 @code{close} returns zero on success, or -1 if an error occurred.
38964 @var{fd} isn't a valid open file descriptor.
38967 The call was interrupted by the user.
38973 @unnumberedsubsubsec read
38974 @cindex read, file-i/o system call
38979 int read(int fd, void *buf, unsigned int count);
38983 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
38985 @item Return value:
38986 On success, the number of bytes read is returned.
38987 Zero indicates end of file. If count is zero, read
38988 returns zero as well. On error, -1 is returned.
38994 @var{fd} is not a valid file descriptor or is not open for
38998 @var{bufptr} is an invalid pointer value.
39001 The call was interrupted by the user.
39007 @unnumberedsubsubsec write
39008 @cindex write, file-i/o system call
39013 int write(int fd, const void *buf, unsigned int count);
39017 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39019 @item Return value:
39020 On success, the number of bytes written are returned.
39021 Zero indicates nothing was written. On error, -1
39028 @var{fd} is not a valid file descriptor or is not open for
39032 @var{bufptr} is an invalid pointer value.
39035 An attempt was made to write a file that exceeds the
39036 host-specific maximum file size allowed.
39039 No space on device to write the data.
39042 The call was interrupted by the user.
39048 @unnumberedsubsubsec lseek
39049 @cindex lseek, file-i/o system call
39054 long lseek (int fd, long offset, int flag);
39058 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39060 @var{flag} is one of:
39064 The offset is set to @var{offset} bytes.
39067 The offset is set to its current location plus @var{offset}
39071 The offset is set to the size of the file plus @var{offset}
39075 @item Return value:
39076 On success, the resulting unsigned offset in bytes from
39077 the beginning of the file is returned. Otherwise, a
39078 value of -1 is returned.
39084 @var{fd} is not a valid open file descriptor.
39087 @var{fd} is associated with the @value{GDBN} console.
39090 @var{flag} is not a proper value.
39093 The call was interrupted by the user.
39099 @unnumberedsubsubsec rename
39100 @cindex rename, file-i/o system call
39105 int rename(const char *oldpath, const char *newpath);
39109 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39111 @item Return value:
39112 On success, zero is returned. On error, -1 is returned.
39118 @var{newpath} is an existing directory, but @var{oldpath} is not a
39122 @var{newpath} is a non-empty directory.
39125 @var{oldpath} or @var{newpath} is a directory that is in use by some
39129 An attempt was made to make a directory a subdirectory
39133 A component used as a directory in @var{oldpath} or new
39134 path is not a directory. Or @var{oldpath} is a directory
39135 and @var{newpath} exists but is not a directory.
39138 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39141 No access to the file or the path of the file.
39145 @var{oldpath} or @var{newpath} was too long.
39148 A directory component in @var{oldpath} or @var{newpath} does not exist.
39151 The file is on a read-only filesystem.
39154 The device containing the file has no room for the new
39158 The call was interrupted by the user.
39164 @unnumberedsubsubsec unlink
39165 @cindex unlink, file-i/o system call
39170 int unlink(const char *pathname);
39174 @samp{Funlink,@var{pathnameptr}/@var{len}}
39176 @item Return value:
39177 On success, zero is returned. On error, -1 is returned.
39183 No access to the file or the path of the file.
39186 The system does not allow unlinking of directories.
39189 The file @var{pathname} cannot be unlinked because it's
39190 being used by another process.
39193 @var{pathnameptr} is an invalid pointer value.
39196 @var{pathname} was too long.
39199 A directory component in @var{pathname} does not exist.
39202 A component of the path is not a directory.
39205 The file is on a read-only filesystem.
39208 The call was interrupted by the user.
39214 @unnumberedsubsubsec stat/fstat
39215 @cindex fstat, file-i/o system call
39216 @cindex stat, file-i/o system call
39221 int stat(const char *pathname, struct stat *buf);
39222 int fstat(int fd, struct stat *buf);
39226 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39227 @samp{Ffstat,@var{fd},@var{bufptr}}
39229 @item Return value:
39230 On success, zero is returned. On error, -1 is returned.
39236 @var{fd} is not a valid open file.
39239 A directory component in @var{pathname} does not exist or the
39240 path is an empty string.
39243 A component of the path is not a directory.
39246 @var{pathnameptr} is an invalid pointer value.
39249 No access to the file or the path of the file.
39252 @var{pathname} was too long.
39255 The call was interrupted by the user.
39261 @unnumberedsubsubsec gettimeofday
39262 @cindex gettimeofday, file-i/o system call
39267 int gettimeofday(struct timeval *tv, void *tz);
39271 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39273 @item Return value:
39274 On success, 0 is returned, -1 otherwise.
39280 @var{tz} is a non-NULL pointer.
39283 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39289 @unnumberedsubsubsec isatty
39290 @cindex isatty, file-i/o system call
39295 int isatty(int fd);
39299 @samp{Fisatty,@var{fd}}
39301 @item Return value:
39302 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39308 The call was interrupted by the user.
39313 Note that the @code{isatty} call is treated as a special case: it returns
39314 1 to the target if the file descriptor is attached
39315 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39316 would require implementing @code{ioctl} and would be more complex than
39321 @unnumberedsubsubsec system
39322 @cindex system, file-i/o system call
39327 int system(const char *command);
39331 @samp{Fsystem,@var{commandptr}/@var{len}}
39333 @item Return value:
39334 If @var{len} is zero, the return value indicates whether a shell is
39335 available. A zero return value indicates a shell is not available.
39336 For non-zero @var{len}, the value returned is -1 on error and the
39337 return status of the command otherwise. Only the exit status of the
39338 command is returned, which is extracted from the host's @code{system}
39339 return value by calling @code{WEXITSTATUS(retval)}. In case
39340 @file{/bin/sh} could not be executed, 127 is returned.
39346 The call was interrupted by the user.
39351 @value{GDBN} takes over the full task of calling the necessary host calls
39352 to perform the @code{system} call. The return value of @code{system} on
39353 the host is simplified before it's returned
39354 to the target. Any termination signal information from the child process
39355 is discarded, and the return value consists
39356 entirely of the exit status of the called command.
39358 Due to security concerns, the @code{system} call is by default refused
39359 by @value{GDBN}. The user has to allow this call explicitly with the
39360 @code{set remote system-call-allowed 1} command.
39363 @item set remote system-call-allowed
39364 @kindex set remote system-call-allowed
39365 Control whether to allow the @code{system} calls in the File I/O
39366 protocol for the remote target. The default is zero (disabled).
39368 @item show remote system-call-allowed
39369 @kindex show remote system-call-allowed
39370 Show whether the @code{system} calls are allowed in the File I/O
39374 @node Protocol-specific Representation of Datatypes
39375 @subsection Protocol-specific Representation of Datatypes
39376 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39379 * Integral Datatypes::
39381 * Memory Transfer::
39386 @node Integral Datatypes
39387 @unnumberedsubsubsec Integral Datatypes
39388 @cindex integral datatypes, in file-i/o protocol
39390 The integral datatypes used in the system calls are @code{int},
39391 @code{unsigned int}, @code{long}, @code{unsigned long},
39392 @code{mode_t}, and @code{time_t}.
39394 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39395 implemented as 32 bit values in this protocol.
39397 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39399 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39400 in @file{limits.h}) to allow range checking on host and target.
39402 @code{time_t} datatypes are defined as seconds since the Epoch.
39404 All integral datatypes transferred as part of a memory read or write of a
39405 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39408 @node Pointer Values
39409 @unnumberedsubsubsec Pointer Values
39410 @cindex pointer values, in file-i/o protocol
39412 Pointers to target data are transmitted as they are. An exception
39413 is made for pointers to buffers for which the length isn't
39414 transmitted as part of the function call, namely strings. Strings
39415 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39422 which is a pointer to data of length 18 bytes at position 0x1aaf.
39423 The length is defined as the full string length in bytes, including
39424 the trailing null byte. For example, the string @code{"hello world"}
39425 at address 0x123456 is transmitted as
39431 @node Memory Transfer
39432 @unnumberedsubsubsec Memory Transfer
39433 @cindex memory transfer, in file-i/o protocol
39435 Structured data which is transferred using a memory read or write (for
39436 example, a @code{struct stat}) is expected to be in a protocol-specific format
39437 with all scalar multibyte datatypes being big endian. Translation to
39438 this representation needs to be done both by the target before the @code{F}
39439 packet is sent, and by @value{GDBN} before
39440 it transfers memory to the target. Transferred pointers to structured
39441 data should point to the already-coerced data at any time.
39445 @unnumberedsubsubsec struct stat
39446 @cindex struct stat, in file-i/o protocol
39448 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39449 is defined as follows:
39453 unsigned int st_dev; /* device */
39454 unsigned int st_ino; /* inode */
39455 mode_t st_mode; /* protection */
39456 unsigned int st_nlink; /* number of hard links */
39457 unsigned int st_uid; /* user ID of owner */
39458 unsigned int st_gid; /* group ID of owner */
39459 unsigned int st_rdev; /* device type (if inode device) */
39460 unsigned long st_size; /* total size, in bytes */
39461 unsigned long st_blksize; /* blocksize for filesystem I/O */
39462 unsigned long st_blocks; /* number of blocks allocated */
39463 time_t st_atime; /* time of last access */
39464 time_t st_mtime; /* time of last modification */
39465 time_t st_ctime; /* time of last change */
39469 The integral datatypes conform to the definitions given in the
39470 appropriate section (see @ref{Integral Datatypes}, for details) so this
39471 structure is of size 64 bytes.
39473 The values of several fields have a restricted meaning and/or
39479 A value of 0 represents a file, 1 the console.
39482 No valid meaning for the target. Transmitted unchanged.
39485 Valid mode bits are described in @ref{Constants}. Any other
39486 bits have currently no meaning for the target.
39491 No valid meaning for the target. Transmitted unchanged.
39496 These values have a host and file system dependent
39497 accuracy. Especially on Windows hosts, the file system may not
39498 support exact timing values.
39501 The target gets a @code{struct stat} of the above representation and is
39502 responsible for coercing it to the target representation before
39505 Note that due to size differences between the host, target, and protocol
39506 representations of @code{struct stat} members, these members could eventually
39507 get truncated on the target.
39509 @node struct timeval
39510 @unnumberedsubsubsec struct timeval
39511 @cindex struct timeval, in file-i/o protocol
39513 The buffer of type @code{struct timeval} used by the File-I/O protocol
39514 is defined as follows:
39518 time_t tv_sec; /* second */
39519 long tv_usec; /* microsecond */
39523 The integral datatypes conform to the definitions given in the
39524 appropriate section (see @ref{Integral Datatypes}, for details) so this
39525 structure is of size 8 bytes.
39528 @subsection Constants
39529 @cindex constants, in file-i/o protocol
39531 The following values are used for the constants inside of the
39532 protocol. @value{GDBN} and target are responsible for translating these
39533 values before and after the call as needed.
39544 @unnumberedsubsubsec Open Flags
39545 @cindex open flags, in file-i/o protocol
39547 All values are given in hexadecimal representation.
39559 @node mode_t Values
39560 @unnumberedsubsubsec mode_t Values
39561 @cindex mode_t values, in file-i/o protocol
39563 All values are given in octal representation.
39580 @unnumberedsubsubsec Errno Values
39581 @cindex errno values, in file-i/o protocol
39583 All values are given in decimal representation.
39608 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39609 any error value not in the list of supported error numbers.
39612 @unnumberedsubsubsec Lseek Flags
39613 @cindex lseek flags, in file-i/o protocol
39622 @unnumberedsubsubsec Limits
39623 @cindex limits, in file-i/o protocol
39625 All values are given in decimal representation.
39628 INT_MIN -2147483648
39630 UINT_MAX 4294967295
39631 LONG_MIN -9223372036854775808
39632 LONG_MAX 9223372036854775807
39633 ULONG_MAX 18446744073709551615
39636 @node File-I/O Examples
39637 @subsection File-I/O Examples
39638 @cindex file-i/o examples
39640 Example sequence of a write call, file descriptor 3, buffer is at target
39641 address 0x1234, 6 bytes should be written:
39644 <- @code{Fwrite,3,1234,6}
39645 @emph{request memory read from target}
39648 @emph{return "6 bytes written"}
39652 Example sequence of a read call, file descriptor 3, buffer is at target
39653 address 0x1234, 6 bytes should be read:
39656 <- @code{Fread,3,1234,6}
39657 @emph{request memory write to target}
39658 -> @code{X1234,6:XXXXXX}
39659 @emph{return "6 bytes read"}
39663 Example sequence of a read call, call fails on the host due to invalid
39664 file descriptor (@code{EBADF}):
39667 <- @code{Fread,3,1234,6}
39671 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
39675 <- @code{Fread,3,1234,6}
39680 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
39684 <- @code{Fread,3,1234,6}
39685 -> @code{X1234,6:XXXXXX}
39689 @node Library List Format
39690 @section Library List Format
39691 @cindex library list format, remote protocol
39693 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
39694 same process as your application to manage libraries. In this case,
39695 @value{GDBN} can use the loader's symbol table and normal memory
39696 operations to maintain a list of shared libraries. On other
39697 platforms, the operating system manages loaded libraries.
39698 @value{GDBN} can not retrieve the list of currently loaded libraries
39699 through memory operations, so it uses the @samp{qXfer:libraries:read}
39700 packet (@pxref{qXfer library list read}) instead. The remote stub
39701 queries the target's operating system and reports which libraries
39704 The @samp{qXfer:libraries:read} packet returns an XML document which
39705 lists loaded libraries and their offsets. Each library has an
39706 associated name and one or more segment or section base addresses,
39707 which report where the library was loaded in memory.
39709 For the common case of libraries that are fully linked binaries, the
39710 library should have a list of segments. If the target supports
39711 dynamic linking of a relocatable object file, its library XML element
39712 should instead include a list of allocated sections. The segment or
39713 section bases are start addresses, not relocation offsets; they do not
39714 depend on the library's link-time base addresses.
39716 @value{GDBN} must be linked with the Expat library to support XML
39717 library lists. @xref{Expat}.
39719 A simple memory map, with one loaded library relocated by a single
39720 offset, looks like this:
39724 <library name="/lib/libc.so.6">
39725 <segment address="0x10000000"/>
39730 Another simple memory map, with one loaded library with three
39731 allocated sections (.text, .data, .bss), looks like this:
39735 <library name="sharedlib.o">
39736 <section address="0x10000000"/>
39737 <section address="0x20000000"/>
39738 <section address="0x30000000"/>
39743 The format of a library list is described by this DTD:
39746 <!-- library-list: Root element with versioning -->
39747 <!ELEMENT library-list (library)*>
39748 <!ATTLIST library-list version CDATA #FIXED "1.0">
39749 <!ELEMENT library (segment*, section*)>
39750 <!ATTLIST library name CDATA #REQUIRED>
39751 <!ELEMENT segment EMPTY>
39752 <!ATTLIST segment address CDATA #REQUIRED>
39753 <!ELEMENT section EMPTY>
39754 <!ATTLIST section address CDATA #REQUIRED>
39757 In addition, segments and section descriptors cannot be mixed within a
39758 single library element, and you must supply at least one segment or
39759 section for each library.
39761 @node Library List Format for SVR4 Targets
39762 @section Library List Format for SVR4 Targets
39763 @cindex library list format, remote protocol
39765 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
39766 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
39767 shared libraries. Still a special library list provided by this packet is
39768 more efficient for the @value{GDBN} remote protocol.
39770 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
39771 loaded libraries and their SVR4 linker parameters. For each library on SVR4
39772 target, the following parameters are reported:
39776 @code{name}, the absolute file name from the @code{l_name} field of
39777 @code{struct link_map}.
39779 @code{lm} with address of @code{struct link_map} used for TLS
39780 (Thread Local Storage) access.
39782 @code{l_addr}, the displacement as read from the field @code{l_addr} of
39783 @code{struct link_map}. For prelinked libraries this is not an absolute
39784 memory address. It is a displacement of absolute memory address against
39785 address the file was prelinked to during the library load.
39787 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
39790 Additionally the single @code{main-lm} attribute specifies address of
39791 @code{struct link_map} used for the main executable. This parameter is used
39792 for TLS access and its presence is optional.
39794 @value{GDBN} must be linked with the Expat library to support XML
39795 SVR4 library lists. @xref{Expat}.
39797 A simple memory map, with two loaded libraries (which do not use prelink),
39801 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
39802 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
39804 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
39806 </library-list-svr>
39809 The format of an SVR4 library list is described by this DTD:
39812 <!-- library-list-svr4: Root element with versioning -->
39813 <!ELEMENT library-list-svr4 (library)*>
39814 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
39815 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
39816 <!ELEMENT library EMPTY>
39817 <!ATTLIST library name CDATA #REQUIRED>
39818 <!ATTLIST library lm CDATA #REQUIRED>
39819 <!ATTLIST library l_addr CDATA #REQUIRED>
39820 <!ATTLIST library l_ld CDATA #REQUIRED>
39823 @node Memory Map Format
39824 @section Memory Map Format
39825 @cindex memory map format
39827 To be able to write into flash memory, @value{GDBN} needs to obtain a
39828 memory map from the target. This section describes the format of the
39831 The memory map is obtained using the @samp{qXfer:memory-map:read}
39832 (@pxref{qXfer memory map read}) packet and is an XML document that
39833 lists memory regions.
39835 @value{GDBN} must be linked with the Expat library to support XML
39836 memory maps. @xref{Expat}.
39838 The top-level structure of the document is shown below:
39841 <?xml version="1.0"?>
39842 <!DOCTYPE memory-map
39843 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39844 "http://sourceware.org/gdb/gdb-memory-map.dtd">
39850 Each region can be either:
39855 A region of RAM starting at @var{addr} and extending for @var{length}
39859 <memory type="ram" start="@var{addr}" length="@var{length}"/>
39864 A region of read-only memory:
39867 <memory type="rom" start="@var{addr}" length="@var{length}"/>
39872 A region of flash memory, with erasure blocks @var{blocksize}
39876 <memory type="flash" start="@var{addr}" length="@var{length}">
39877 <property name="blocksize">@var{blocksize}</property>
39883 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
39884 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
39885 packets to write to addresses in such ranges.
39887 The formal DTD for memory map format is given below:
39890 <!-- ................................................... -->
39891 <!-- Memory Map XML DTD ................................ -->
39892 <!-- File: memory-map.dtd .............................. -->
39893 <!-- .................................... .............. -->
39894 <!-- memory-map.dtd -->
39895 <!-- memory-map: Root element with versioning -->
39896 <!ELEMENT memory-map (memory | property)>
39897 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
39898 <!ELEMENT memory (property)>
39899 <!-- memory: Specifies a memory region,
39900 and its type, or device. -->
39901 <!ATTLIST memory type CDATA #REQUIRED
39902 start CDATA #REQUIRED
39903 length CDATA #REQUIRED
39904 device CDATA #IMPLIED>
39905 <!-- property: Generic attribute tag -->
39906 <!ELEMENT property (#PCDATA | property)*>
39907 <!ATTLIST property name CDATA #REQUIRED>
39910 @node Thread List Format
39911 @section Thread List Format
39912 @cindex thread list format
39914 To efficiently update the list of threads and their attributes,
39915 @value{GDBN} issues the @samp{qXfer:threads:read} packet
39916 (@pxref{qXfer threads read}) and obtains the XML document with
39917 the following structure:
39920 <?xml version="1.0"?>
39922 <thread id="id" core="0" name="name">
39923 ... description ...
39928 Each @samp{thread} element must have the @samp{id} attribute that
39929 identifies the thread (@pxref{thread-id syntax}). The
39930 @samp{core} attribute, if present, specifies which processor core
39931 the thread was last executing on. The @samp{name} attribute, if
39932 present, specifies the human-readable name of the thread. The content
39933 of the of @samp{thread} element is interpreted as human-readable
39934 auxiliary information.
39936 @node Traceframe Info Format
39937 @section Traceframe Info Format
39938 @cindex traceframe info format
39940 To be able to know which objects in the inferior can be examined when
39941 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
39942 memory ranges, registers and trace state variables that have been
39943 collected in a traceframe.
39945 This list is obtained using the @samp{qXfer:traceframe-info:read}
39946 (@pxref{qXfer traceframe info read}) packet and is an XML document.
39948 @value{GDBN} must be linked with the Expat library to support XML
39949 traceframe info discovery. @xref{Expat}.
39951 The top-level structure of the document is shown below:
39954 <?xml version="1.0"?>
39955 <!DOCTYPE traceframe-info
39956 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
39957 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
39963 Each traceframe block can be either:
39968 A region of collected memory starting at @var{addr} and extending for
39969 @var{length} bytes from there:
39972 <memory start="@var{addr}" length="@var{length}"/>
39976 A block indicating trace state variable numbered @var{number} has been
39980 <tvar id="@var{number}"/>
39985 The formal DTD for the traceframe info format is given below:
39988 <!ELEMENT traceframe-info (memory | tvar)* >
39989 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
39991 <!ELEMENT memory EMPTY>
39992 <!ATTLIST memory start CDATA #REQUIRED
39993 length CDATA #REQUIRED>
39995 <!ATTLIST tvar id CDATA #REQUIRED>
39998 @node Branch Trace Format
39999 @section Branch Trace Format
40000 @cindex branch trace format
40002 In order to display the branch trace of an inferior thread,
40003 @value{GDBN} needs to obtain the list of branches. This list is
40004 represented as list of sequential code blocks that are connected via
40005 branches. The code in each block has been executed sequentially.
40007 This list is obtained using the @samp{qXfer:btrace:read}
40008 (@pxref{qXfer btrace read}) packet and is an XML document.
40010 @value{GDBN} must be linked with the Expat library to support XML
40011 traceframe info discovery. @xref{Expat}.
40013 The top-level structure of the document is shown below:
40016 <?xml version="1.0"?>
40018 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40019 "http://sourceware.org/gdb/gdb-btrace.dtd">
40028 A block of sequentially executed instructions starting at @var{begin}
40029 and ending at @var{end}:
40032 <block begin="@var{begin}" end="@var{end}"/>
40037 The formal DTD for the branch trace format is given below:
40040 <!ELEMENT btrace (block* | pt) >
40041 <!ATTLIST btrace version CDATA #FIXED "1.0">
40043 <!ELEMENT block EMPTY>
40044 <!ATTLIST block begin CDATA #REQUIRED
40045 end CDATA #REQUIRED>
40047 <!ELEMENT pt (pt-config?, raw?)>
40049 <!ELEMENT pt-config (cpu?)>
40051 <!ELEMENT cpu EMPTY>
40052 <!ATTLIST cpu vendor CDATA #REQUIRED
40053 family CDATA #REQUIRED
40054 model CDATA #REQUIRED
40055 stepping CDATA #REQUIRED>
40057 <!ELEMENT raw (#PCDATA)>
40060 @node Branch Trace Configuration Format
40061 @section Branch Trace Configuration Format
40062 @cindex branch trace configuration format
40064 For each inferior thread, @value{GDBN} can obtain the branch trace
40065 configuration using the @samp{qXfer:btrace-conf:read}
40066 (@pxref{qXfer btrace-conf read}) packet.
40068 The configuration describes the branch trace format and configuration
40069 settings for that format. The following information is described:
40073 This thread uses the @dfn{Branch Trace Store} (@acronym{BTS}) format.
40076 The size of the @acronym{BTS} ring buffer in bytes.
40079 This thread uses the @dfn{Intel Processor Trace} (@acronym{Intel
40083 The size of the @acronym{Intel PT} ring buffer in bytes.
40087 @value{GDBN} must be linked with the Expat library to support XML
40088 branch trace configuration discovery. @xref{Expat}.
40090 The formal DTD for the branch trace configuration format is given below:
40093 <!ELEMENT btrace-conf (bts?, pt?)>
40094 <!ATTLIST btrace-conf version CDATA #FIXED "1.0">
40096 <!ELEMENT bts EMPTY>
40097 <!ATTLIST bts size CDATA #IMPLIED>
40099 <!ELEMENT pt EMPTY>
40100 <!ATTLIST pt size CDATA #IMPLIED>
40103 @include agentexpr.texi
40105 @node Target Descriptions
40106 @appendix Target Descriptions
40107 @cindex target descriptions
40109 One of the challenges of using @value{GDBN} to debug embedded systems
40110 is that there are so many minor variants of each processor
40111 architecture in use. It is common practice for vendors to start with
40112 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40113 and then make changes to adapt it to a particular market niche. Some
40114 architectures have hundreds of variants, available from dozens of
40115 vendors. This leads to a number of problems:
40119 With so many different customized processors, it is difficult for
40120 the @value{GDBN} maintainers to keep up with the changes.
40122 Since individual variants may have short lifetimes or limited
40123 audiences, it may not be worthwhile to carry information about every
40124 variant in the @value{GDBN} source tree.
40126 When @value{GDBN} does support the architecture of the embedded system
40127 at hand, the task of finding the correct architecture name to give the
40128 @command{set architecture} command can be error-prone.
40131 To address these problems, the @value{GDBN} remote protocol allows a
40132 target system to not only identify itself to @value{GDBN}, but to
40133 actually describe its own features. This lets @value{GDBN} support
40134 processor variants it has never seen before --- to the extent that the
40135 descriptions are accurate, and that @value{GDBN} understands them.
40137 @value{GDBN} must be linked with the Expat library to support XML
40138 target descriptions. @xref{Expat}.
40141 * Retrieving Descriptions:: How descriptions are fetched from a target.
40142 * Target Description Format:: The contents of a target description.
40143 * Predefined Target Types:: Standard types available for target
40145 * Standard Target Features:: Features @value{GDBN} knows about.
40148 @node Retrieving Descriptions
40149 @section Retrieving Descriptions
40151 Target descriptions can be read from the target automatically, or
40152 specified by the user manually. The default behavior is to read the
40153 description from the target. @value{GDBN} retrieves it via the remote
40154 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40155 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40156 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40157 XML document, of the form described in @ref{Target Description
40160 Alternatively, you can specify a file to read for the target description.
40161 If a file is set, the target will not be queried. The commands to
40162 specify a file are:
40165 @cindex set tdesc filename
40166 @item set tdesc filename @var{path}
40167 Read the target description from @var{path}.
40169 @cindex unset tdesc filename
40170 @item unset tdesc filename
40171 Do not read the XML target description from a file. @value{GDBN}
40172 will use the description supplied by the current target.
40174 @cindex show tdesc filename
40175 @item show tdesc filename
40176 Show the filename to read for a target description, if any.
40180 @node Target Description Format
40181 @section Target Description Format
40182 @cindex target descriptions, XML format
40184 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40185 document which complies with the Document Type Definition provided in
40186 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40187 means you can use generally available tools like @command{xmllint} to
40188 check that your feature descriptions are well-formed and valid.
40189 However, to help people unfamiliar with XML write descriptions for
40190 their targets, we also describe the grammar here.
40192 Target descriptions can identify the architecture of the remote target
40193 and (for some architectures) provide information about custom register
40194 sets. They can also identify the OS ABI of the remote target.
40195 @value{GDBN} can use this information to autoconfigure for your
40196 target, or to warn you if you connect to an unsupported target.
40198 Here is a simple target description:
40201 <target version="1.0">
40202 <architecture>i386:x86-64</architecture>
40207 This minimal description only says that the target uses
40208 the x86-64 architecture.
40210 A target description has the following overall form, with [ ] marking
40211 optional elements and @dots{} marking repeatable elements. The elements
40212 are explained further below.
40215 <?xml version="1.0"?>
40216 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40217 <target version="1.0">
40218 @r{[}@var{architecture}@r{]}
40219 @r{[}@var{osabi}@r{]}
40220 @r{[}@var{compatible}@r{]}
40221 @r{[}@var{feature}@dots{}@r{]}
40226 The description is generally insensitive to whitespace and line
40227 breaks, under the usual common-sense rules. The XML version
40228 declaration and document type declaration can generally be omitted
40229 (@value{GDBN} does not require them), but specifying them may be
40230 useful for XML validation tools. The @samp{version} attribute for
40231 @samp{<target>} may also be omitted, but we recommend
40232 including it; if future versions of @value{GDBN} use an incompatible
40233 revision of @file{gdb-target.dtd}, they will detect and report
40234 the version mismatch.
40236 @subsection Inclusion
40237 @cindex target descriptions, inclusion
40240 @cindex <xi:include>
40243 It can sometimes be valuable to split a target description up into
40244 several different annexes, either for organizational purposes, or to
40245 share files between different possible target descriptions. You can
40246 divide a description into multiple files by replacing any element of
40247 the target description with an inclusion directive of the form:
40250 <xi:include href="@var{document}"/>
40254 When @value{GDBN} encounters an element of this form, it will retrieve
40255 the named XML @var{document}, and replace the inclusion directive with
40256 the contents of that document. If the current description was read
40257 using @samp{qXfer}, then so will be the included document;
40258 @var{document} will be interpreted as the name of an annex. If the
40259 current description was read from a file, @value{GDBN} will look for
40260 @var{document} as a file in the same directory where it found the
40261 original description.
40263 @subsection Architecture
40264 @cindex <architecture>
40266 An @samp{<architecture>} element has this form:
40269 <architecture>@var{arch}</architecture>
40272 @var{arch} is one of the architectures from the set accepted by
40273 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40276 @cindex @code{<osabi>}
40278 This optional field was introduced in @value{GDBN} version 7.0.
40279 Previous versions of @value{GDBN} ignore it.
40281 An @samp{<osabi>} element has this form:
40284 <osabi>@var{abi-name}</osabi>
40287 @var{abi-name} is an OS ABI name from the same selection accepted by
40288 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40290 @subsection Compatible Architecture
40291 @cindex @code{<compatible>}
40293 This optional field was introduced in @value{GDBN} version 7.0.
40294 Previous versions of @value{GDBN} ignore it.
40296 A @samp{<compatible>} element has this form:
40299 <compatible>@var{arch}</compatible>
40302 @var{arch} is one of the architectures from the set accepted by
40303 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40305 A @samp{<compatible>} element is used to specify that the target
40306 is able to run binaries in some other than the main target architecture
40307 given by the @samp{<architecture>} element. For example, on the
40308 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40309 or @code{powerpc:common64}, but the system is able to run binaries
40310 in the @code{spu} architecture as well. The way to describe this
40311 capability with @samp{<compatible>} is as follows:
40314 <architecture>powerpc:common</architecture>
40315 <compatible>spu</compatible>
40318 @subsection Features
40321 Each @samp{<feature>} describes some logical portion of the target
40322 system. Features are currently used to describe available CPU
40323 registers and the types of their contents. A @samp{<feature>} element
40327 <feature name="@var{name}">
40328 @r{[}@var{type}@dots{}@r{]}
40334 Each feature's name should be unique within the description. The name
40335 of a feature does not matter unless @value{GDBN} has some special
40336 knowledge of the contents of that feature; if it does, the feature
40337 should have its standard name. @xref{Standard Target Features}.
40341 Any register's value is a collection of bits which @value{GDBN} must
40342 interpret. The default interpretation is a two's complement integer,
40343 but other types can be requested by name in the register description.
40344 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40345 Target Types}), and the description can define additional composite types.
40347 Each type element must have an @samp{id} attribute, which gives
40348 a unique (within the containing @samp{<feature>}) name to the type.
40349 Types must be defined before they are used.
40352 Some targets offer vector registers, which can be treated as arrays
40353 of scalar elements. These types are written as @samp{<vector>} elements,
40354 specifying the array element type, @var{type}, and the number of elements,
40358 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40362 If a register's value is usefully viewed in multiple ways, define it
40363 with a union type containing the useful representations. The
40364 @samp{<union>} element contains one or more @samp{<field>} elements,
40365 each of which has a @var{name} and a @var{type}:
40368 <union id="@var{id}">
40369 <field name="@var{name}" type="@var{type}"/>
40375 If a register's value is composed from several separate values, define
40376 it with a structure type. There are two forms of the @samp{<struct>}
40377 element; a @samp{<struct>} element must either contain only bitfields
40378 or contain no bitfields. If the structure contains only bitfields,
40379 its total size in bytes must be specified, each bitfield must have an
40380 explicit start and end, and bitfields are automatically assigned an
40381 integer type. The field's @var{start} should be less than or
40382 equal to its @var{end}, and zero represents the least significant bit.
40385 <struct id="@var{id}" size="@var{size}">
40386 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40391 If the structure contains no bitfields, then each field has an
40392 explicit type, and no implicit padding is added.
40395 <struct id="@var{id}">
40396 <field name="@var{name}" type="@var{type}"/>
40402 If a register's value is a series of single-bit flags, define it with
40403 a flags type. The @samp{<flags>} element has an explicit @var{size}
40404 and contains one or more @samp{<field>} elements. Each field has a
40405 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40409 <flags id="@var{id}" size="@var{size}">
40410 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40415 @subsection Registers
40418 Each register is represented as an element with this form:
40421 <reg name="@var{name}"
40422 bitsize="@var{size}"
40423 @r{[}regnum="@var{num}"@r{]}
40424 @r{[}save-restore="@var{save-restore}"@r{]}
40425 @r{[}type="@var{type}"@r{]}
40426 @r{[}group="@var{group}"@r{]}/>
40430 The components are as follows:
40435 The register's name; it must be unique within the target description.
40438 The register's size, in bits.
40441 The register's number. If omitted, a register's number is one greater
40442 than that of the previous register (either in the current feature or in
40443 a preceding feature); the first register in the target description
40444 defaults to zero. This register number is used to read or write
40445 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40446 packets, and registers appear in the @code{g} and @code{G} packets
40447 in order of increasing register number.
40450 Whether the register should be preserved across inferior function
40451 calls; this must be either @code{yes} or @code{no}. The default is
40452 @code{yes}, which is appropriate for most registers except for
40453 some system control registers; this is not related to the target's
40457 The type of the register. It may be a predefined type, a type
40458 defined in the current feature, or one of the special types @code{int}
40459 and @code{float}. @code{int} is an integer type of the correct size
40460 for @var{bitsize}, and @code{float} is a floating point type (in the
40461 architecture's normal floating point format) of the correct size for
40462 @var{bitsize}. The default is @code{int}.
40465 The register group to which this register belongs. It must
40466 be either @code{general}, @code{float}, or @code{vector}. If no
40467 @var{group} is specified, @value{GDBN} will not display the register
40468 in @code{info registers}.
40472 @node Predefined Target Types
40473 @section Predefined Target Types
40474 @cindex target descriptions, predefined types
40476 Type definitions in the self-description can build up composite types
40477 from basic building blocks, but can not define fundamental types. Instead,
40478 standard identifiers are provided by @value{GDBN} for the fundamental
40479 types. The currently supported types are:
40488 Signed integer types holding the specified number of bits.
40495 Unsigned integer types holding the specified number of bits.
40499 Pointers to unspecified code and data. The program counter and
40500 any dedicated return address register may be marked as code
40501 pointers; printing a code pointer converts it into a symbolic
40502 address. The stack pointer and any dedicated address registers
40503 may be marked as data pointers.
40506 Single precision IEEE floating point.
40509 Double precision IEEE floating point.
40512 The 12-byte extended precision format used by ARM FPA registers.
40515 The 10-byte extended precision format used by x87 registers.
40518 32bit @sc{eflags} register used by x86.
40521 32bit @sc{mxcsr} register used by x86.
40525 @node Standard Target Features
40526 @section Standard Target Features
40527 @cindex target descriptions, standard features
40529 A target description must contain either no registers or all the
40530 target's registers. If the description contains no registers, then
40531 @value{GDBN} will assume a default register layout, selected based on
40532 the architecture. If the description contains any registers, the
40533 default layout will not be used; the standard registers must be
40534 described in the target description, in such a way that @value{GDBN}
40535 can recognize them.
40537 This is accomplished by giving specific names to feature elements
40538 which contain standard registers. @value{GDBN} will look for features
40539 with those names and verify that they contain the expected registers;
40540 if any known feature is missing required registers, or if any required
40541 feature is missing, @value{GDBN} will reject the target
40542 description. You can add additional registers to any of the
40543 standard features --- @value{GDBN} will display them just as if
40544 they were added to an unrecognized feature.
40546 This section lists the known features and their expected contents.
40547 Sample XML documents for these features are included in the
40548 @value{GDBN} source tree, in the directory @file{gdb/features}.
40550 Names recognized by @value{GDBN} should include the name of the
40551 company or organization which selected the name, and the overall
40552 architecture to which the feature applies; so e.g.@: the feature
40553 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40555 The names of registers are not case sensitive for the purpose
40556 of recognizing standard features, but @value{GDBN} will only display
40557 registers using the capitalization used in the description.
40560 * AArch64 Features::
40563 * MicroBlaze Features::
40566 * Nios II Features::
40567 * PowerPC Features::
40568 * S/390 and System z Features::
40573 @node AArch64 Features
40574 @subsection AArch64 Features
40575 @cindex target descriptions, AArch64 features
40577 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40578 targets. It should contain registers @samp{x0} through @samp{x30},
40579 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40581 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40582 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40586 @subsection ARM Features
40587 @cindex target descriptions, ARM features
40589 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40591 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40592 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40594 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40595 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40596 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40599 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40600 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40602 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40603 it should contain at least registers @samp{wR0} through @samp{wR15} and
40604 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40605 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40607 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40608 should contain at least registers @samp{d0} through @samp{d15}. If
40609 they are present, @samp{d16} through @samp{d31} should also be included.
40610 @value{GDBN} will synthesize the single-precision registers from
40611 halves of the double-precision registers.
40613 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40614 need to contain registers; it instructs @value{GDBN} to display the
40615 VFP double-precision registers as vectors and to synthesize the
40616 quad-precision registers from pairs of double-precision registers.
40617 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40618 be present and include 32 double-precision registers.
40620 @node i386 Features
40621 @subsection i386 Features
40622 @cindex target descriptions, i386 features
40624 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40625 targets. It should describe the following registers:
40629 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40631 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40633 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40634 @samp{fs}, @samp{gs}
40636 @samp{st0} through @samp{st7}
40638 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40639 @samp{foseg}, @samp{fooff} and @samp{fop}
40642 The register sets may be different, depending on the target.
40644 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40645 describe registers:
40649 @samp{xmm0} through @samp{xmm7} for i386
40651 @samp{xmm0} through @samp{xmm15} for amd64
40656 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40657 @samp{org.gnu.gdb.i386.sse} feature. It should
40658 describe the upper 128 bits of @sc{ymm} registers:
40662 @samp{ymm0h} through @samp{ymm7h} for i386
40664 @samp{ymm0h} through @samp{ymm15h} for amd64
40667 The @samp{org.gnu.gdb.i386.mpx} is an optional feature representing Intel
40668 Memory Protection Extension (MPX). It should describe the following registers:
40672 @samp{bnd0raw} through @samp{bnd3raw} for i386 and amd64.
40674 @samp{bndcfgu} and @samp{bndstatus} for i386 and amd64.
40677 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40678 describe a single register, @samp{orig_eax}.
40680 The @samp{org.gnu.gdb.i386.avx512} feature is optional and requires the
40681 @samp{org.gnu.gdb.i386.avx} feature. It should
40682 describe additional @sc{xmm} registers:
40686 @samp{xmm16h} through @samp{xmm31h}, only valid for amd64.
40689 It should describe the upper 128 bits of additional @sc{ymm} registers:
40693 @samp{ymm16h} through @samp{ymm31h}, only valid for amd64.
40697 describe the upper 256 bits of @sc{zmm} registers:
40701 @samp{zmm0h} through @samp{zmm7h} for i386.
40703 @samp{zmm0h} through @samp{zmm15h} for amd64.
40707 describe the additional @sc{zmm} registers:
40711 @samp{zmm16h} through @samp{zmm31h}, only valid for amd64.
40714 @node MicroBlaze Features
40715 @subsection MicroBlaze Features
40716 @cindex target descriptions, MicroBlaze features
40718 The @samp{org.gnu.gdb.microblaze.core} feature is required for MicroBlaze
40719 targets. It should contain registers @samp{r0} through @samp{r31},
40720 @samp{rpc}, @samp{rmsr}, @samp{rear}, @samp{resr}, @samp{rfsr}, @samp{rbtr},
40721 @samp{rpvr}, @samp{rpvr1} through @samp{rpvr11}, @samp{redr}, @samp{rpid},
40722 @samp{rzpr}, @samp{rtlbx}, @samp{rtlbsx}, @samp{rtlblo}, and @samp{rtlbhi}.
40724 The @samp{org.gnu.gdb.microblaze.stack-protect} feature is optional.
40725 If present, it should contain registers @samp{rshr} and @samp{rslr}
40727 @node MIPS Features
40728 @subsection @acronym{MIPS} Features
40729 @cindex target descriptions, @acronym{MIPS} features
40731 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40732 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40733 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40736 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40737 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40738 registers. They may be 32-bit or 64-bit depending on the target.
40740 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40741 it may be optional in a future version of @value{GDBN}. It should
40742 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40743 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40745 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40746 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40747 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40748 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40750 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40751 contain a single register, @samp{restart}, which is used by the
40752 Linux kernel to control restartable syscalls.
40754 @node M68K Features
40755 @subsection M68K Features
40756 @cindex target descriptions, M68K features
40759 @item @samp{org.gnu.gdb.m68k.core}
40760 @itemx @samp{org.gnu.gdb.coldfire.core}
40761 @itemx @samp{org.gnu.gdb.fido.core}
40762 One of those features must be always present.
40763 The feature that is present determines which flavor of m68k is
40764 used. The feature that is present should contain registers
40765 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40766 @samp{sp}, @samp{ps} and @samp{pc}.
40768 @item @samp{org.gnu.gdb.coldfire.fp}
40769 This feature is optional. If present, it should contain registers
40770 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40774 @node Nios II Features
40775 @subsection Nios II Features
40776 @cindex target descriptions, Nios II features
40778 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
40779 targets. It should contain the 32 core registers (@samp{zero},
40780 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
40781 @samp{pc}, and the 16 control registers (@samp{status} through
40784 @node PowerPC Features
40785 @subsection PowerPC Features
40786 @cindex target descriptions, PowerPC features
40788 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40789 targets. It should contain registers @samp{r0} through @samp{r31},
40790 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40791 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40793 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40794 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40796 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40797 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40800 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40801 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40802 will combine these registers with the floating point registers
40803 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40804 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40805 through @samp{vs63}, the set of vector registers for POWER7.
40807 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40808 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40809 @samp{spefscr}. SPE targets should provide 32-bit registers in
40810 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40811 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40812 these to present registers @samp{ev0} through @samp{ev31} to the
40815 @node S/390 and System z Features
40816 @subsection S/390 and System z Features
40817 @cindex target descriptions, S/390 features
40818 @cindex target descriptions, System z features
40820 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
40821 System z targets. It should contain the PSW and the 16 general
40822 registers. In particular, System z targets should provide the 64-bit
40823 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
40824 S/390 targets should provide the 32-bit versions of these registers.
40825 A System z target that runs in 31-bit addressing mode should provide
40826 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
40827 register's upper halves @samp{r0h} through @samp{r15h}, and their
40828 lower halves @samp{r0l} through @samp{r15l}.
40830 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
40831 contain the 64-bit registers @samp{f0} through @samp{f15}, and
40834 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
40835 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
40837 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
40838 contain the register @samp{orig_r2}, which is 64-bit wide on System z
40839 targets and 32-bit otherwise. In addition, the feature may contain
40840 the @samp{last_break} register, whose width depends on the addressing
40841 mode, as well as the @samp{system_call} register, which is always
40844 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
40845 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
40846 @samp{atia}, and @samp{tr0} through @samp{tr15}.
40848 The @samp{org.gnu.gdb.s390.vx} feature is optional. It should contain
40849 64-bit wide registers @samp{v0l} through @samp{v15l}, which will be
40850 combined by @value{GDBN} with the floating point registers @samp{f0}
40851 through @samp{f15} to present the 128-bit wide vector registers
40852 @samp{v0} through @samp{v15}. In addition, this feature should
40853 contain the 128-bit wide vector registers @samp{v16} through
40856 @node TIC6x Features
40857 @subsection TMS320C6x Features
40858 @cindex target descriptions, TIC6x features
40859 @cindex target descriptions, TMS320C6x features
40860 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40861 targets. It should contain registers @samp{A0} through @samp{A15},
40862 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40864 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40865 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40866 through @samp{B31}.
40868 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
40869 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
40871 @node Operating System Information
40872 @appendix Operating System Information
40873 @cindex operating system information
40879 Users of @value{GDBN} often wish to obtain information about the state of
40880 the operating system running on the target---for example the list of
40881 processes, or the list of open files. This section describes the
40882 mechanism that makes it possible. This mechanism is similar to the
40883 target features mechanism (@pxref{Target Descriptions}), but focuses
40884 on a different aspect of target.
40886 Operating system information is retrived from the target via the
40887 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
40888 read}). The object name in the request should be @samp{osdata}, and
40889 the @var{annex} identifies the data to be fetched.
40892 @appendixsection Process list
40893 @cindex operating system information, process list
40895 When requesting the process list, the @var{annex} field in the
40896 @samp{qXfer} request should be @samp{processes}. The returned data is
40897 an XML document. The formal syntax of this document is defined in
40898 @file{gdb/features/osdata.dtd}.
40900 An example document is:
40903 <?xml version="1.0"?>
40904 <!DOCTYPE target SYSTEM "osdata.dtd">
40905 <osdata type="processes">
40907 <column name="pid">1</column>
40908 <column name="user">root</column>
40909 <column name="command">/sbin/init</column>
40910 <column name="cores">1,2,3</column>
40915 Each item should include a column whose name is @samp{pid}. The value
40916 of that column should identify the process on the target. The
40917 @samp{user} and @samp{command} columns are optional, and will be
40918 displayed by @value{GDBN}. The @samp{cores} column, if present,
40919 should contain a comma-separated list of cores that this process
40920 is running on. Target may provide additional columns,
40921 which @value{GDBN} currently ignores.
40923 @node Trace File Format
40924 @appendix Trace File Format
40925 @cindex trace file format
40927 The trace file comes in three parts: a header, a textual description
40928 section, and a trace frame section with binary data.
40930 The header has the form @code{\x7fTRACE0\n}. The first byte is
40931 @code{0x7f} so as to indicate that the file contains binary data,
40932 while the @code{0} is a version number that may have different values
40935 The description section consists of multiple lines of @sc{ascii} text
40936 separated by newline characters (@code{0xa}). The lines may include a
40937 variety of optional descriptive or context-setting information, such
40938 as tracepoint definitions or register set size. @value{GDBN} will
40939 ignore any line that it does not recognize. An empty line marks the end
40942 @c FIXME add some specific types of data
40944 The trace frame section consists of a number of consecutive frames.
40945 Each frame begins with a two-byte tracepoint number, followed by a
40946 four-byte size giving the amount of data in the frame. The data in
40947 the frame consists of a number of blocks, each introduced by a
40948 character indicating its type (at least register, memory, and trace
40949 state variable). The data in this section is raw binary, not a
40950 hexadecimal or other encoding; its endianness matches the target's
40953 @c FIXME bi-arch may require endianness/arch info in description section
40956 @item R @var{bytes}
40957 Register block. The number and ordering of bytes matches that of a
40958 @code{g} packet in the remote protocol. Note that these are the
40959 actual bytes, in target order and @value{GDBN} register order, not a
40960 hexadecimal encoding.
40962 @item M @var{address} @var{length} @var{bytes}...
40963 Memory block. This is a contiguous block of memory, at the 8-byte
40964 address @var{address}, with a 2-byte length @var{length}, followed by
40965 @var{length} bytes.
40967 @item V @var{number} @var{value}
40968 Trace state variable block. This records the 8-byte signed value
40969 @var{value} of trace state variable numbered @var{number}.
40973 Future enhancements of the trace file format may include additional types
40976 @node Index Section Format
40977 @appendix @code{.gdb_index} section format
40978 @cindex .gdb_index section format
40979 @cindex index section format
40981 This section documents the index section that is created by @code{save
40982 gdb-index} (@pxref{Index Files}). The index section is
40983 DWARF-specific; some knowledge of DWARF is assumed in this
40986 The mapped index file format is designed to be directly
40987 @code{mmap}able on any architecture. In most cases, a datum is
40988 represented using a little-endian 32-bit integer value, called an
40989 @code{offset_type}. Big endian machines must byte-swap the values
40990 before using them. Exceptions to this rule are noted. The data is
40991 laid out such that alignment is always respected.
40993 A mapped index consists of several areas, laid out in order.
40997 The file header. This is a sequence of values, of @code{offset_type}
40998 unless otherwise noted:
41002 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41003 Version 4 uses a different hashing function from versions 5 and 6.
41004 Version 6 includes symbols for inlined functions, whereas versions 4
41005 and 5 do not. Version 7 adds attributes to the CU indices in the
41006 symbol table. Version 8 specifies that symbols from DWARF type units
41007 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41008 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41010 @value{GDBN} will only read version 4, 5, or 6 indices
41011 by specifying @code{set use-deprecated-index-sections on}.
41012 GDB has a workaround for potentially broken version 7 indices so it is
41013 currently not flagged as deprecated.
41016 The offset, from the start of the file, of the CU list.
41019 The offset, from the start of the file, of the types CU list. Note
41020 that this area can be empty, in which case this offset will be equal
41021 to the next offset.
41024 The offset, from the start of the file, of the address area.
41027 The offset, from the start of the file, of the symbol table.
41030 The offset, from the start of the file, of the constant pool.
41034 The CU list. This is a sequence of pairs of 64-bit little-endian
41035 values, sorted by the CU offset. The first element in each pair is
41036 the offset of a CU in the @code{.debug_info} section. The second
41037 element in each pair is the length of that CU. References to a CU
41038 elsewhere in the map are done using a CU index, which is just the
41039 0-based index into this table. Note that if there are type CUs, then
41040 conceptually CUs and type CUs form a single list for the purposes of
41044 The types CU list. This is a sequence of triplets of 64-bit
41045 little-endian values. In a triplet, the first value is the CU offset,
41046 the second value is the type offset in the CU, and the third value is
41047 the type signature. The types CU list is not sorted.
41050 The address area. The address area consists of a sequence of address
41051 entries. Each address entry has three elements:
41055 The low address. This is a 64-bit little-endian value.
41058 The high address. This is a 64-bit little-endian value. Like
41059 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41062 The CU index. This is an @code{offset_type} value.
41066 The symbol table. This is an open-addressed hash table. The size of
41067 the hash table is always a power of 2.
41069 Each slot in the hash table consists of a pair of @code{offset_type}
41070 values. The first value is the offset of the symbol's name in the
41071 constant pool. The second value is the offset of the CU vector in the
41074 If both values are 0, then this slot in the hash table is empty. This
41075 is ok because while 0 is a valid constant pool index, it cannot be a
41076 valid index for both a string and a CU vector.
41078 The hash value for a table entry is computed by applying an
41079 iterative hash function to the symbol's name. Starting with an
41080 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41081 the string is incorporated into the hash using the formula depending on the
41086 The formula is @code{r = r * 67 + c - 113}.
41088 @item Versions 5 to 7
41089 The formula is @code{r = r * 67 + tolower (c) - 113}.
41092 The terminating @samp{\0} is not incorporated into the hash.
41094 The step size used in the hash table is computed via
41095 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41096 value, and @samp{size} is the size of the hash table. The step size
41097 is used to find the next candidate slot when handling a hash
41100 The names of C@t{++} symbols in the hash table are canonicalized. We
41101 don't currently have a simple description of the canonicalization
41102 algorithm; if you intend to create new index sections, you must read
41106 The constant pool. This is simply a bunch of bytes. It is organized
41107 so that alignment is correct: CU vectors are stored first, followed by
41110 A CU vector in the constant pool is a sequence of @code{offset_type}
41111 values. The first value is the number of CU indices in the vector.
41112 Each subsequent value is the index and symbol attributes of a CU in
41113 the CU list. This element in the hash table is used to indicate which
41114 CUs define the symbol and how the symbol is used.
41115 See below for the format of each CU index+attributes entry.
41117 A string in the constant pool is zero-terminated.
41120 Attributes were added to CU index values in @code{.gdb_index} version 7.
41121 If a symbol has multiple uses within a CU then there is one
41122 CU index+attributes value for each use.
41124 The format of each CU index+attributes entry is as follows
41130 This is the index of the CU in the CU list.
41132 These bits are reserved for future purposes and must be zero.
41134 The kind of the symbol in the CU.
41138 This value is reserved and should not be used.
41139 By reserving zero the full @code{offset_type} value is backwards compatible
41140 with previous versions of the index.
41142 The symbol is a type.
41144 The symbol is a variable or an enum value.
41146 The symbol is a function.
41148 Any other kind of symbol.
41150 These values are reserved.
41154 This bit is zero if the value is global and one if it is static.
41156 The determination of whether a symbol is global or static is complicated.
41157 The authorative reference is the file @file{dwarf2read.c} in
41158 @value{GDBN} sources.
41162 This pseudo-code describes the computation of a symbol's kind and
41163 global/static attributes in the index.
41166 is_external = get_attribute (die, DW_AT_external);
41167 language = get_attribute (cu_die, DW_AT_language);
41170 case DW_TAG_typedef:
41171 case DW_TAG_base_type:
41172 case DW_TAG_subrange_type:
41176 case DW_TAG_enumerator:
41178 is_static = (language != CPLUS && language != JAVA);
41180 case DW_TAG_subprogram:
41182 is_static = ! (is_external || language == ADA);
41184 case DW_TAG_constant:
41186 is_static = ! is_external;
41188 case DW_TAG_variable:
41190 is_static = ! is_external;
41192 case DW_TAG_namespace:
41196 case DW_TAG_class_type:
41197 case DW_TAG_interface_type:
41198 case DW_TAG_structure_type:
41199 case DW_TAG_union_type:
41200 case DW_TAG_enumeration_type:
41202 is_static = (language != CPLUS && language != JAVA);
41210 @appendix Manual pages
41214 * gdb man:: The GNU Debugger man page
41215 * gdbserver man:: Remote Server for the GNU Debugger man page
41216 * gcore man:: Generate a core file of a running program
41217 * gdbinit man:: gdbinit scripts
41223 @c man title gdb The GNU Debugger
41225 @c man begin SYNOPSIS gdb
41226 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
41227 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
41228 [@option{-b}@w{ }@var{bps}]
41229 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
41230 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
41231 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
41232 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
41233 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
41236 @c man begin DESCRIPTION gdb
41237 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
41238 going on ``inside'' another program while it executes -- or what another
41239 program was doing at the moment it crashed.
41241 @value{GDBN} can do four main kinds of things (plus other things in support of
41242 these) to help you catch bugs in the act:
41246 Start your program, specifying anything that might affect its behavior.
41249 Make your program stop on specified conditions.
41252 Examine what has happened, when your program has stopped.
41255 Change things in your program, so you can experiment with correcting the
41256 effects of one bug and go on to learn about another.
41259 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
41262 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
41263 commands from the terminal until you tell it to exit with the @value{GDBN}
41264 command @code{quit}. You can get online help from @value{GDBN} itself
41265 by using the command @code{help}.
41267 You can run @code{gdb} with no arguments or options; but the most
41268 usual way to start @value{GDBN} is with one argument or two, specifying an
41269 executable program as the argument:
41275 You can also start with both an executable program and a core file specified:
41281 You can, instead, specify a process ID as a second argument, if you want
41282 to debug a running process:
41290 would attach @value{GDBN} to process @code{1234} (unless you also have a file
41291 named @file{1234}; @value{GDBN} does check for a core file first).
41292 With option @option{-p} you can omit the @var{program} filename.
41294 Here are some of the most frequently needed @value{GDBN} commands:
41296 @c pod2man highlights the right hand side of the @item lines.
41298 @item break [@var{file}:]@var{functiop}
41299 Set a breakpoint at @var{function} (in @var{file}).
41301 @item run [@var{arglist}]
41302 Start your program (with @var{arglist}, if specified).
41305 Backtrace: display the program stack.
41307 @item print @var{expr}
41308 Display the value of an expression.
41311 Continue running your program (after stopping, e.g. at a breakpoint).
41314 Execute next program line (after stopping); step @emph{over} any
41315 function calls in the line.
41317 @item edit [@var{file}:]@var{function}
41318 look at the program line where it is presently stopped.
41320 @item list [@var{file}:]@var{function}
41321 type the text of the program in the vicinity of where it is presently stopped.
41324 Execute next program line (after stopping); step @emph{into} any
41325 function calls in the line.
41327 @item help [@var{name}]
41328 Show information about @value{GDBN} command @var{name}, or general information
41329 about using @value{GDBN}.
41332 Exit from @value{GDBN}.
41336 For full details on @value{GDBN},
41337 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41338 by Richard M. Stallman and Roland H. Pesch. The same text is available online
41339 as the @code{gdb} entry in the @code{info} program.
41343 @c man begin OPTIONS gdb
41344 Any arguments other than options specify an executable
41345 file and core file (or process ID); that is, the first argument
41346 encountered with no
41347 associated option flag is equivalent to a @option{-se} option, and the second,
41348 if any, is equivalent to a @option{-c} option if it's the name of a file.
41350 both long and short forms; both are shown here. The long forms are also
41351 recognized if you truncate them, so long as enough of the option is
41352 present to be unambiguous. (If you prefer, you can flag option
41353 arguments with @option{+} rather than @option{-}, though we illustrate the
41354 more usual convention.)
41356 All the options and command line arguments you give are processed
41357 in sequential order. The order makes a difference when the @option{-x}
41363 List all options, with brief explanations.
41365 @item -symbols=@var{file}
41366 @itemx -s @var{file}
41367 Read symbol table from file @var{file}.
41370 Enable writing into executable and core files.
41372 @item -exec=@var{file}
41373 @itemx -e @var{file}
41374 Use file @var{file} as the executable file to execute when
41375 appropriate, and for examining pure data in conjunction with a core
41378 @item -se=@var{file}
41379 Read symbol table from file @var{file} and use it as the executable
41382 @item -core=@var{file}
41383 @itemx -c @var{file}
41384 Use file @var{file} as a core dump to examine.
41386 @item -command=@var{file}
41387 @itemx -x @var{file}
41388 Execute @value{GDBN} commands from file @var{file}.
41390 @item -ex @var{command}
41391 Execute given @value{GDBN} @var{command}.
41393 @item -directory=@var{directory}
41394 @itemx -d @var{directory}
41395 Add @var{directory} to the path to search for source files.
41398 Do not execute commands from @file{~/.gdbinit}.
41402 Do not execute commands from any @file{.gdbinit} initialization files.
41406 ``Quiet''. Do not print the introductory and copyright messages. These
41407 messages are also suppressed in batch mode.
41410 Run in batch mode. Exit with status @code{0} after processing all the command
41411 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
41412 Exit with nonzero status if an error occurs in executing the @value{GDBN}
41413 commands in the command files.
41415 Batch mode may be useful for running @value{GDBN} as a filter, for example to
41416 download and run a program on another computer; in order to make this
41417 more useful, the message
41420 Program exited normally.
41424 (which is ordinarily issued whenever a program running under @value{GDBN} control
41425 terminates) is not issued when running in batch mode.
41427 @item -cd=@var{directory}
41428 Run @value{GDBN} using @var{directory} as its working directory,
41429 instead of the current directory.
41433 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
41434 @value{GDBN} to output the full file name and line number in a standard,
41435 recognizable fashion each time a stack frame is displayed (which
41436 includes each time the program stops). This recognizable format looks
41437 like two @samp{\032} characters, followed by the file name, line number
41438 and character position separated by colons, and a newline. The
41439 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
41440 characters as a signal to display the source code for the frame.
41443 Set the line speed (baud rate or bits per second) of any serial
41444 interface used by @value{GDBN} for remote debugging.
41446 @item -tty=@var{device}
41447 Run using @var{device} for your program's standard input and output.
41451 @c man begin SEEALSO gdb
41453 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41454 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41455 documentation are properly installed at your site, the command
41462 should give you access to the complete manual.
41464 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41465 Richard M. Stallman and Roland H. Pesch, July 1991.
41469 @node gdbserver man
41470 @heading gdbserver man
41472 @c man title gdbserver Remote Server for the GNU Debugger
41474 @c man begin SYNOPSIS gdbserver
41475 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41477 gdbserver --attach @var{comm} @var{pid}
41479 gdbserver --multi @var{comm}
41483 @c man begin DESCRIPTION gdbserver
41484 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
41485 than the one which is running the program being debugged.
41488 @subheading Usage (server (target) side)
41491 Usage (server (target) side):
41494 First, you need to have a copy of the program you want to debug put onto
41495 the target system. The program can be stripped to save space if needed, as
41496 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
41497 the @value{GDBN} running on the host system.
41499 To use the server, you log on to the target system, and run the @command{gdbserver}
41500 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
41501 your program, and (c) its arguments. The general syntax is:
41504 target> gdbserver @var{comm} @var{program} [@var{args} ...]
41507 For example, using a serial port, you might say:
41511 @c @file would wrap it as F</dev/com1>.
41512 target> gdbserver /dev/com1 emacs foo.txt
41515 target> gdbserver @file{/dev/com1} emacs foo.txt
41519 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
41520 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
41521 waits patiently for the host @value{GDBN} to communicate with it.
41523 To use a TCP connection, you could say:
41526 target> gdbserver host:2345 emacs foo.txt
41529 This says pretty much the same thing as the last example, except that we are
41530 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
41531 that we are expecting to see a TCP connection from @code{host} to local TCP port
41532 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
41533 want for the port number as long as it does not conflict with any existing TCP
41534 ports on the target system. This same port number must be used in the host
41535 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
41536 you chose a port number that conflicts with another service, @command{gdbserver} will
41537 print an error message and exit.
41539 @command{gdbserver} can also attach to running programs.
41540 This is accomplished via the @option{--attach} argument. The syntax is:
41543 target> gdbserver --attach @var{comm} @var{pid}
41546 @var{pid} is the process ID of a currently running process. It isn't
41547 necessary to point @command{gdbserver} at a binary for the running process.
41549 To start @code{gdbserver} without supplying an initial command to run
41550 or process ID to attach, use the @option{--multi} command line option.
41551 In such case you should connect using @kbd{target extended-remote} to start
41552 the program you want to debug.
41555 target> gdbserver --multi @var{comm}
41559 @subheading Usage (host side)
41565 You need an unstripped copy of the target program on your host system, since
41566 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
41567 would, with the target program as the first argument. (You may need to use the
41568 @option{--baud} option if the serial line is running at anything except 9600 baud.)
41569 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
41570 new command you need to know about is @code{target remote}
41571 (or @code{target extended-remote}). Its argument is either
41572 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
41573 descriptor. For example:
41577 @c @file would wrap it as F</dev/ttyb>.
41578 (gdb) target remote /dev/ttyb
41581 (gdb) target remote @file{/dev/ttyb}
41586 communicates with the server via serial line @file{/dev/ttyb}, and:
41589 (gdb) target remote the-target:2345
41593 communicates via a TCP connection to port 2345 on host `the-target', where
41594 you previously started up @command{gdbserver} with the same port number. Note that for
41595 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
41596 command, otherwise you may get an error that looks something like
41597 `Connection refused'.
41599 @command{gdbserver} can also debug multiple inferiors at once,
41602 the @value{GDBN} manual in node @code{Inferiors and Programs}
41603 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
41606 @ref{Inferiors and Programs}.
41608 In such case use the @code{extended-remote} @value{GDBN} command variant:
41611 (gdb) target extended-remote the-target:2345
41614 The @command{gdbserver} option @option{--multi} may or may not be used in such
41618 @c man begin OPTIONS gdbserver
41619 There are three different modes for invoking @command{gdbserver}:
41624 Debug a specific program specified by its program name:
41627 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
41630 The @var{comm} parameter specifies how should the server communicate
41631 with @value{GDBN}; it is either a device name (to use a serial line),
41632 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
41633 stdin/stdout of @code{gdbserver}. Specify the name of the program to
41634 debug in @var{prog}. Any remaining arguments will be passed to the
41635 program verbatim. When the program exits, @value{GDBN} will close the
41636 connection, and @code{gdbserver} will exit.
41639 Debug a specific program by specifying the process ID of a running
41643 gdbserver --attach @var{comm} @var{pid}
41646 The @var{comm} parameter is as described above. Supply the process ID
41647 of a running program in @var{pid}; @value{GDBN} will do everything
41648 else. Like with the previous mode, when the process @var{pid} exits,
41649 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
41652 Multi-process mode -- debug more than one program/process:
41655 gdbserver --multi @var{comm}
41658 In this mode, @value{GDBN} can instruct @command{gdbserver} which
41659 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
41660 close the connection when a process being debugged exits, so you can
41661 debug several processes in the same session.
41664 In each of the modes you may specify these options:
41669 List all options, with brief explanations.
41672 This option causes @command{gdbserver} to print its version number and exit.
41675 @command{gdbserver} will attach to a running program. The syntax is:
41678 target> gdbserver --attach @var{comm} @var{pid}
41681 @var{pid} is the process ID of a currently running process. It isn't
41682 necessary to point @command{gdbserver} at a binary for the running process.
41685 To start @code{gdbserver} without supplying an initial command to run
41686 or process ID to attach, use this command line option.
41687 Then you can connect using @kbd{target extended-remote} and start
41688 the program you want to debug. The syntax is:
41691 target> gdbserver --multi @var{comm}
41695 Instruct @code{gdbserver} to display extra status information about the debugging
41697 This option is intended for @code{gdbserver} development and for bug reports to
41700 @item --remote-debug
41701 Instruct @code{gdbserver} to display remote protocol debug output.
41702 This option is intended for @code{gdbserver} development and for bug reports to
41705 @item --debug-format=option1@r{[},option2,...@r{]}
41706 Instruct @code{gdbserver} to include extra information in each line
41707 of debugging output.
41708 @xref{Other Command-Line Arguments for gdbserver}.
41711 Specify a wrapper to launch programs
41712 for debugging. The option should be followed by the name of the
41713 wrapper, then any command-line arguments to pass to the wrapper, then
41714 @kbd{--} indicating the end of the wrapper arguments.
41717 By default, @command{gdbserver} keeps the listening TCP port open, so that
41718 additional connections are possible. However, if you start @code{gdbserver}
41719 with the @option{--once} option, it will stop listening for any further
41720 connection attempts after connecting to the first @value{GDBN} session.
41722 @c --disable-packet is not documented for users.
41724 @c --disable-randomization and --no-disable-randomization are superseded by
41725 @c QDisableRandomization.
41730 @c man begin SEEALSO gdbserver
41732 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41733 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41734 documentation are properly installed at your site, the command
41740 should give you access to the complete manual.
41742 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41743 Richard M. Stallman and Roland H. Pesch, July 1991.
41750 @c man title gcore Generate a core file of a running program
41753 @c man begin SYNOPSIS gcore
41754 gcore [-o @var{filename}] @var{pid}
41758 @c man begin DESCRIPTION gcore
41759 Generate a core dump of a running program with process ID @var{pid}.
41760 Produced file is equivalent to a kernel produced core file as if the process
41761 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
41762 limit). Unlike after a crash, after @command{gcore} the program remains
41763 running without any change.
41766 @c man begin OPTIONS gcore
41768 @item -o @var{filename}
41769 The optional argument
41770 @var{filename} specifies the file name where to put the core dump.
41771 If not specified, the file name defaults to @file{core.@var{pid}},
41772 where @var{pid} is the running program process ID.
41776 @c man begin SEEALSO gcore
41778 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41779 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41780 documentation are properly installed at your site, the command
41787 should give you access to the complete manual.
41789 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41790 Richard M. Stallman and Roland H. Pesch, July 1991.
41797 @c man title gdbinit GDB initialization scripts
41800 @c man begin SYNOPSIS gdbinit
41801 @ifset SYSTEM_GDBINIT
41802 @value{SYSTEM_GDBINIT}
41811 @c man begin DESCRIPTION gdbinit
41812 These files contain @value{GDBN} commands to automatically execute during
41813 @value{GDBN} startup. The lines of contents are canned sequences of commands,
41816 the @value{GDBN} manual in node @code{Sequences}
41817 -- shell command @code{info -f gdb -n Sequences}.
41823 Please read more in
41825 the @value{GDBN} manual in node @code{Startup}
41826 -- shell command @code{info -f gdb -n Startup}.
41833 @ifset SYSTEM_GDBINIT
41834 @item @value{SYSTEM_GDBINIT}
41836 @ifclear SYSTEM_GDBINIT
41837 @item (not enabled with @code{--with-system-gdbinit} during compilation)
41839 System-wide initialization file. It is executed unless user specified
41840 @value{GDBN} option @code{-nx} or @code{-n}.
41843 the @value{GDBN} manual in node @code{System-wide configuration}
41844 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
41847 @ref{System-wide configuration}.
41851 User initialization file. It is executed unless user specified
41852 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
41855 Initialization file for current directory. It may need to be enabled with
41856 @value{GDBN} security command @code{set auto-load local-gdbinit}.
41859 the @value{GDBN} manual in node @code{Init File in the Current Directory}
41860 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
41863 @ref{Init File in the Current Directory}.
41868 @c man begin SEEALSO gdbinit
41870 gdb(1), @code{info -f gdb -n Startup}
41872 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
41873 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
41874 documentation are properly installed at your site, the command
41880 should give you access to the complete manual.
41882 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
41883 Richard M. Stallman and Roland H. Pesch, July 1991.
41889 @node GNU Free Documentation License
41890 @appendix GNU Free Documentation License
41893 @node Concept Index
41894 @unnumbered Concept Index
41898 @node Command and Variable Index
41899 @unnumbered Command, Variable, and Function Index
41904 % I think something like @@colophon should be in texinfo. In the
41906 \long\def\colophon{\hbox to0pt{}\vfill
41907 \centerline{The body of this manual is set in}
41908 \centerline{\fontname\tenrm,}
41909 \centerline{with headings in {\bf\fontname\tenbf}}
41910 \centerline{and examples in {\tt\fontname\tentt}.}
41911 \centerline{{\it\fontname\tenit\/},}
41912 \centerline{{\bf\fontname\tenbf}, and}
41913 \centerline{{\sl\fontname\tensl\/}}
41914 \centerline{are used for emphasis.}\vfill}
41916 % Blame: doc@@cygnus.com, 1991.